To provide backup during power cuts (to my shame I can't live without
broadband) I'm thinking of buying one these:

http://preview.tinyurl.com/h8kw2ln

It's a UPS circuit designed to charge a lead acid battery (not supplied)
and to maintain 12V in case of a power cut. It seems to be ideal for my
purposes as I have an 85AH leisure battery to hand.

However the spec says, quaintly, "It is allowed to connect batteries
that is below 12V 20AH".

It's been decades since I did any electronics but I don't understand the
limit. Surely, other than that it will take a long time to charge a big
battery (of no concern to me), what harm can come from using the 85AH
battery? I will, of course, be sure not to exceed the current limit.

Another Dave
--
Change nospam to techie

On 19 Oct 2016 14:48, Another Dave wrote:
To provide backup during power cuts (to my shame I can't live without
broadband) I'm thinking of buying one these:

http://preview.tinyurl.com/h8kw2ln

It's a UPS circuit designed to charge a lead acid battery (not supplied)
and to maintain 12V in case of a power cut. It seems to be ideal for my
purposes as I have an 85AH leisure battery to hand.

However the spec says, quaintly, "It is allowed to connect batteries
that is below 12V 20AH".

It's been decades since I did any electronics but I don't understand the
limit. Surely, other than that it will take a long time to charge a big
battery (of no concern to me), what harm can come from using the 85AH
battery? I will, of course, be sure not to exceed the current limit.

Another Dave
It does not imply nor indeed state to my mind that bigger batteries are
bad merely that smaller are acceptable in what I taker to be some
translation from another language? Some chargers might overcharge
smaller capacity batteries?

--
Flying on Per Ardua ad Astra

On 19/10/2016 14:48, Another Dave wrote:
To provide backup during power cuts (to my shame I can't live without
broadband) I'm thinking of buying one these:

http://preview.tinyurl.com/h8kw2ln

It's a UPS circuit designed to charge a lead acid battery (not supplied)
and to maintain 12V in case of a power cut. It seems to be ideal for my
purposes as I have an 85AH leisure battery to hand.

However the spec says, quaintly, "It is allowed to connect batteries
that is below 12V 20AH".

It's been decades since I did any electronics but I don't understand the
limit. Surely, other than that it will take a long time to charge a big
battery (of no concern to me), what harm can come from using the 85AH
battery? I will, of course, be sure not to exceed the current limit.

Another Dave

I'm going to hazard a guess here, but seeing as it's not fan cooled I
would suggest they are doing what a lot of the cheap consumer UPSs do.

That is, limit the AH of the batteries to limit the run time and prevent
the thing from cooking itself.

On 19/10/2016 14:48, Another Dave wrote:
To provide backup during power cuts (to my shame I can't live without
broadband) I'm thinking of buying one these:

http://preview.tinyurl.com/h8kw2ln

It's a UPS circuit designed to charge a lead acid battery (not supplied)
and to maintain 12V in case of a power cut. It seems to be ideal for my
purposes as I have an 85AH leisure battery to hand.

However the spec says, quaintly, "It is allowed to connect batteries
that is below 12V 20AH".

It's been decades since I did any electronics but I don't understand the
limit. Surely, other than that it will take a long time to charge a big
battery (of no concern to me), what harm can come from using the 85AH
battery? I will, of course, be sure not to exceed the current limit.

Another Dave

Doh! thought that was an inverter Maybe it's just about the charge
current or the rating of the relay then?

On Wed, 19 Oct 2016 15:21:13 +0100
Zephirum wrote:

It does not imply nor indeed state to my mind that bigger batteries
are bad merely that smaller are acceptable in what I taker to be some
translation from another language?

An example from further down the page:
"It supports float-charging with high charging efficiency, battery
plumpness could be up to 90%."

Yes, we have a dubious translation. Quite funny, though.

--
Davey.

On 19/10/16 16:33, Davey wrote:
On Wed, 19 Oct 2016 15:21:13 +0100
Zephirum wrote:

It does not imply nor indeed state to my mind that bigger batteries
are bad merely that smaller are acceptable in what I taker to be some
translation from another language?

An example from further down the page:
"It supports float-charging with high charging efficiency, battery
plumpness could be up to 90%."

Yes, we have a dubious translation. Quite funny, though.

Argh! me hearties, always clamp hard on yer rug terminal!


--
€œSome people like to travel by train because it combines the slowness of
a car with the cramped public exposure of €¨an airplane.€�

Dennis Miller

Lee wrote:
On 19/10/2016 14:48, Another Dave wrote:
To provide backup during power cuts (to my shame I can't live without
broadband) I'm thinking of buying one these:

http://preview.tinyurl.com/h8kw2ln

It's a UPS circuit designed to charge a lead acid battery (not supplied)
and to maintain 12V in case of a power cut. It seems to be ideal for my
purposes as I have an 85AH leisure battery to hand.

However the spec says, quaintly, "It is allowed to connect batteries
that is below 12V 20AH".

It's been decades since I did any electronics but I don't understand the
limit. Surely, other than that it will take a long time to charge a big
battery (of no concern to me), what harm can come from using the 85AH
battery? I will, of course, be sure not to exceed the current limit.

Another Dave

Doh! thought that was an inverter Maybe it's just about the charge
current or the rating of the relay then?
Curiously described device. It is the battery that provides the UPS
function.
Hardly any difference from a battery charger then. At best it might have
a relay to disconnect the battery if its terminal voltage falls to
possible damage level.

There are trimmable power supply bricks with nominal 12v output looking
very similar but far cheaper, primarily advertised as LED power units.

Just connect power supply, battery and load all in parallel perhaps via
fuse.

"Lee" wrote in message
...
On 19/10/2016 14:48, Another Dave wrote:
To provide backup during power cuts (to my shame I can't live without
broadband) I'm thinking of buying one these:

http://preview.tinyurl.com/h8kw2ln

It's a UPS circuit designed to charge a lead acid battery (not supplied)
and to maintain 12V in case of a power cut. It seems to be ideal for my
purposes as I have an 85AH leisure battery to hand.

However the spec says, quaintly, "It is allowed to connect batteries
that is below 12V 20AH".

It's been decades since I did any electronics but I don't understand the
limit. Surely, other than that it will take a long time to charge a big
battery (of no concern to me), what harm can come from using the 85AH
battery? I will, of course, be sure not to exceed the current limit.

Another Dave

Doh! thought that was an inverter Maybe it's just about the charge
current or the rating of the relay then?

Nope, neither of those vary with the AH of the battery.

The time it is charged for does tho.

On 19/10/2016 20:02, Rod Speed wrote:


"Lee" wrote in message
Maybe it's just about the charge
current or the rating of the relay then?


Nope, neither of those vary with the AH of the battery.

Er yes it does, try hooking up a discharged 7AH and 100AH battery to a
100A charger and tell me they take the same charge current

Of course the charger should be current limited so that it doesn't matter.
Unless it's so poorly designed that it does.

The time it is charged for does tho.

Still think they may be playing safe with the maximum current, either
through the relay or the PCB tracks.
Didn't see any sign of a DC/battery fuse...

And I'm fully aware that the theory agrees with you.
Internal resistance should not vary by AH of the battery, only by the
chemistry.

Practice however, says otherwise...

Lee wrote
Rod Speed wrote
Lee wrote

Maybe it's just about the charge
current or the rating of the relay then?

Nope, neither of those vary with the AH of the battery.

Er yes it does,

No it doesnt.

try hooking up a discharged 7AH and 100AH battery to a 100A charger and
tell me they take the same charge current

They do.

Of course the charger should be current limited so that it doesn't matter.

So the current doesnt change.

Unless it's so poorly designed that it does.

Wrong again.

The time it is charged for does tho.

Still think they may be playing safe with the maximum current, either
through the relay or the PCB tracks.

That doesnt vary with the AH of the battery.

Didn't see any sign of a DC/battery fuse...

Most dont, because they are constant current.

Lee wrote

And I'm fully aware that the theory agrees with you.
Internal resistance should not vary by AH of the
battery, only by the chemistry.

Practice however, says otherwise...

No it does not.

On 20/10/2016 00:23, Rod Speed wrote:
Lee wrote



try hooking up a discharged 7AH and 100AH battery to a 100A charger
and tell me they take the same charge current

They do.

Better tell my 100A charger and my multimeter then, because they
disagree with you.


Still think they may be playing safe with the maximum current, either
through the relay or the PCB tracks.

That doesnt vary with the AH of the battery.

Didn't see any sign of a DC/battery fuse...

Most dont, because they are constant current.

Missing the point. If the device works like others I have used, the
"output volts" terminal is relay switched between the PSU (with mains
applied) and the battery (in mains cut). How is that then current
limited if the load is connected directly to the battery?

Lee wrote
Rod Speed wrote
Lee wrote

try hooking up a discharged 7AH and 100AH battery to a 100A charger and
tell me they take the same charge current

They do.

Better tell my 100A charger and my multimeter then, because they disagree
with you.

What you are seeing is a significant difference in the
technology used in those two batterys, not the AH rating.

Still think they may be playing safe with the maximum current, either
through the relay or the PCB tracks.

That doesnt vary with the AH of the battery.

Didn't see any sign of a DC/battery fuse...

Most dont, because they are constant current.

Missing the point.

Nope.

If the device works like others I have used, the "output volts" terminal
is relay switched between the PSU (with mains applied) and the battery (in
mains cut).

Try that again in english.

How is that then current limited if the load is connected directly to the
battery?

With a charger, the battery IS the load.

On 20/10/2016 00:51, Rod Speed wrote:

Try that again in english.

I thought it was clear enough
Since it's using a relay to switch the battery, the total current
flowing into the load must flow through that relay.

Now, I realise the PSU is nominally rated at 10A, so it's unlikely the
load is going to be more than that. But as I said, maybe they are just
playing safe on the current the relay and PCB can handle.

Or more likely, for *how long*.
Which would depend on the Ah rating of the battery.

On 20/10/2016 00:51, Rod Speed wrote:

What you are seeing is a significant difference in the
technology used in those two batterys, not the AH rating.


Then maybe the designers of the unit considered that and optimised it
for small SLA batteries.
Maybe it works just fine with larger batteries with slightly different
chemistry, or maybe it doesn't and that's why they don't recommend to
use them.

"Lee" wrote in message
news
On 20/10/2016 00:51, Rod Speed wrote:

Try that again in english.

I thought it was clear enough
Since it's using a relay to switch the battery, the total current flowing
into the load must flow through that relay.

Now, I realise the PSU is nominally rated at 10A, so it's unlikely the
load is going to be more than that. But as I said, maybe they are just
playing safe on the current the relay and PCB can handle.

That isnt going to change with the AH when the battery
is the same technology.

Or more likely, for *how long*.
Which would depend on the Ah rating of the battery.

I'm not convinced that it can't supply 10A forever or close to that.

Lee wrote
Rod Speed wrote

What you are seeing is a significant difference in the
technology used in those two batterys, not the AH rating.

Then maybe the designers of the unit considered that and optimised it for
small SLA batteries.

Unlikely given the AH that they do say is acceptable.

Maybe it works just fine with larger batteries with slightly different
chemistry,

You dont know that is true with the battery being
considered.

or maybe it doesn't and that's why they don't recommend to use them.

Very unlikely.

You have not considered one thing in this scenario. I know that many of the
broad band cabinets which Virgin uses are powered by mains with no back ups,
so at least in SW London, when the power is off where the cabinet is, both
phone and broadband go off as does the TV cable service.
It could well be that BT the other supplier of the Fibre connections to
these boxes do the same for broadband. You would need to find out in some
way before wasting your money on back up supplies.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Another Dave" wrote in message
...
To provide backup during power cuts (to my shame I can't live without
broadband) I'm thinking of buying one these:

http://preview.tinyurl.com/h8kw2ln

It's a UPS circuit designed to charge a lead acid battery (not supplied)
and to maintain 12V in case of a power cut. It seems to be ideal for my
purposes as I have an 85AH leisure battery to hand.

However the spec says, quaintly, "It is allowed to connect batteries that
is below 12V 20AH".

It's been decades since I did any electronics but I don't understand the
limit. Surely, other than that it will take a long time to charge a big
battery (of no concern to me), what harm can come from using the 85AH
battery? I will, of course, be sure not to exceed the current limit.

Another Dave
--
Change nospam to techie

On 20/10/2016 07:31, Brian Gaff wrote:
You have not considered one thing in this scenario. I know that many of the
broad band cabinets which Virgin uses are powered by mains with no back ups,
so at least in SW London, when the power is off where the cabinet is, both
phone and broadband go off as does the TV cable service.
It could well be that BT the other supplier of the Fibre connections to
these boxes do the same for broadband. You would need to find out in some
way before wasting your money on back up supplies.
Brian

When our power has gone off in the past, I just use the laptop which
will last for about 5 hours on battery and tether my mobile phone to the
laptop which gets me back online.
Luckily I get a good 4G signal of up to 92Mbps down and 33 up.

In article , Brian Gaff
wrote:
You have not considered one thing in this scenario. I know that many of
the broad band cabinets which Virgin uses are powered by mains with no
back ups, so at least in SW London, when the power is off where the
cabinet is, both phone and broadband go off as does the TV cable service.
It could well be that BT the other supplier of the Fibre connections to
these boxes do the same for broadband. You would need to find out in some
way before wasting your money on back up supplies. Brian

There are certinly batteries in the BT Fibre box which feeds my house. I've
seen them.

--
from KT24 in Surrey, England

On 19/10/2016 23:57, Lee wrote:
And I'm fully aware that the theory agrees with you.
Internal resistance should not vary by AH of the battery, only by the
chemistry.

Terminal voltage is fixed for a given chemistry but internal resistance
varies with the surface area of the electrodes used and charge state.

It mainly varies with the active surface area of the lead plates in this
case (which is proportional to the battery Ah capacity AOBE).

IOW the short circuit current of a 1Ah cell is a lot lower than the
short circuit current of a 100Ah cell (don't try this at home). Both
will probably get a thin wire to red heat before you can let go.

NB This device should have an automotive low voltage fuse somewhere in
series with its battery to avoid embarrassment in the event of an
accidental short circuit on the load side. This becomes much more
important the larger the capacity of storage battery being used.

Deep discharge batteries using thicker lead plates to survive more
cycles and car starter motors thinner ones for maximum surface area to
give minimum internal resistance being the two most common variants.

Practice however, says otherwise...

So does theory.

--
Regards,
Martin Brown

On 19/10/2016 16:33, Davey wrote:
On Wed, 19 Oct 2016 15:21:13 +0100
Zephirum wrote:

It does not imply nor indeed state to my mind that bigger batteries
are bad merely that smaller are acceptable in what I taker to be some
translation from another language?

An example from further down the page:
"It supports float-charging with high charging efficiency, battery
plumpness could be up to 90%."

I find that worrying. Plump batteries in a UPS are extremely difficult
to prize out when their sides have bowed out by more than about 5%.

Yes, we have a dubious translation. Quite funny, though.


It hardly inspires confidence for an emergency backup system!

--
Regards,
Martin Brown

On Wednesday, 19 October 2016 14:48:41 UTC+1, Another Dave wrote:
To provide backup during power cuts (to my shame I can't live without
broadband) I'm thinking of buying one these:

http://preview.tinyurl.com/h8kw2ln

It's a UPS circuit designed to charge a lead acid battery (not supplied)
and to maintain 12V in case of a power cut. It seems to be ideal for my
purposes as I have an 85AH leisure battery to hand.

However the spec says, quaintly, "It is allowed to connect batteries
that is below 12V 20AH".

It's been decades since I did any electronics but I don't understand the
limit. Surely, other than that it will take a long time to charge a big
battery (of no concern to me), what harm can come from using the 85AH
battery? I will, of course, be sure not to exceed the current limit.

Another Dave
--
Change nospam to techie

Just buy a laptop.

"Bod" wrote in message
...
On 20/10/2016 07:31, Brian Gaff wrote:
You have not considered one thing in this scenario. I know that many of
the
broad band cabinets which Virgin uses are powered by mains with no back
ups,
so at least in SW London, when the power is off where the cabinet is,
both
phone and broadband go off as does the TV cable service.
It could well be that BT the other supplier of the Fibre connections to
these boxes do the same for broadband. You would need to find out in some
way before wasting your money on back up supplies.
Brian

When our power has gone off in the past, I just use the laptop which will
last for about 5 hours on battery and tether my mobile phone to the laptop
which gets me back online.

That only works when the mobile bases have battery backup.

Luckily I get a good 4G signal of up to 92Mbps down and 33 up.

I do too, and the FTTN broadband has battery backup too.

On Wednesday, 19 October 2016 16:33:07 UTC+1, Davey wrote:
On Wed, 19 Oct 2016 15:21:13 +0100
Zephirum wrote:

It does not imply nor indeed state to my mind that bigger batteries
are bad merely that smaller are acceptable in what I taker to be some
translation from another language?

An example from further down the page:
"It supports float-charging with high charging efficiency, battery
plumpness could be up to 90%."


I blame the EU it's all that cheap fatty food making everyone obese.




Yes, we have a dubious translation. Quite funny, though.

--
Davey.

On 20/10/2016 09:23, Rod Speed wrote:


"Bod" wrote in message
...
On 20/10/2016 07:31, Brian Gaff wrote:
You have not considered one thing in this scenario. I know that many
of the
broad band cabinets which Virgin uses are powered by mains with no
back ups,
so at least in SW London, when the power is off where the cabinet
is, both
phone and broadband go off as does the TV cable service.
It could well be that BT the other supplier of the Fibre connections to
these boxes do the same for broadband. You would need to find out in
some
way before wasting your money on back up supplies.
Brian

When our power has gone off in the past, I just use the laptop which
will last for about 5 hours on battery and tether my mobile phone to
the laptop which gets me back online.

That only works when the mobile bases have battery backup.

Luckily I get a good 4G signal of up to 92Mbps down and 33 up.

I do too, and the FTTN broadband has battery backup too.

I assumed that the original poster was talking about his landline
broadband going down.
It would be very unlikely for the landline broadband to go down at the
same time as the mobile broadband signal.
Well that coincidence has never happened here so far.
I also have a battery power pack for the laptop which will give me
another few hours and also a power pack for the mobile phone.

In article ,
Lee wrote:
Still think they may be playing safe with the maximum current, either
through the relay or the PCB tracks.
Didn't see any sign of a DC/battery fuse...

Ever seen a car jump start pack? The 20 amp.hr or so SLA battery in that
is capable of supplying hundreds of amps - for a short time.

--
*Venison for dinner again? Oh deer!*

Dave Plowman London SW
To e-mail, change noise into sound.

"Bod" wrote in message
...
On 20/10/2016 09:23, Rod Speed wrote:


"Bod" wrote in message
...
On 20/10/2016 07:31, Brian Gaff wrote:
You have not considered one thing in this scenario. I know that many
of the
broad band cabinets which Virgin uses are powered by mains with no
back ups,
so at least in SW London, when the power is off where the cabinet
is, both
phone and broadband go off as does the TV cable service.
It could well be that BT the other supplier of the Fibre connections
to
these boxes do the same for broadband. You would need to find out in
some
way before wasting your money on back up supplies.
Brian

When our power has gone off in the past, I just use the laptop which
will last for about 5 hours on battery and tether my mobile phone to
the laptop which gets me back online.

That only works when the mobile bases have battery backup.

Luckily I get a good 4G signal of up to 92Mbps down and 33 up.

I do too, and the FTTN broadband has battery backup too.

I assumed that the original poster was talking about his landline
broadband going down.

He was actually talking about the mains going down
and his landline broadband still being available.

It would be very unlikely for the landline broadband to go down at the
same time as the mobile broadband signal.

Depends on how the landline broadband is done.

Plenty of places have that done by a RIM or CMUX
and those don’t necessarily have battery backup
and plenty of mobile bases don’t either, so you
can see them both stop on a mains failure.

Well that coincidence has never happened here so far.

Yes, some mobile bases do have battery backup.

I also have a battery power pack for the laptop which will give me another
few hours and also a power pack for the mobile phone.

You can need it for the mobile phone. Plenty of them run the
battery down pretty quickly when they are used as a hotspot.

When our power has gone off in the past, I just use the laptop which
will last for about 5 hours on battery and tether my mobile phone to
the laptop which gets me back online.

That only works when the mobile bases have battery backup.

Luckily I get a good 4G signal of up to 92Mbps down and 33 up.

I do too, and the FTTN broadband has battery backup too.

I assumed that the original poster was talking about his landline
broadband going down.

He was actually talking about the mains going down
and his landline broadband still being available.

It would be very unlikely for the landline broadband to go down at the
same time as the mobile broadband signal.

Depends on how the landline broadband is done.

Plenty of places have that done by a RIM or CMUX
and those don’t necessarily have battery backup
and plenty of mobile bases don’t either, so you
can see them both stop on a mains failure.

Well that coincidence has never happened here so far.

Yes, some mobile bases do have battery backup.

I also have a battery power pack for the laptop which will give me
another few hours and also a power pack for the mobile phone.

You can need it for the mobile phone. Plenty of them run the
battery down pretty quickly when they are used as a hotspot.

What do you mean by "Depends on how the landline broadband is done"?

If my electricity gets cut off, the modem/router won't work.
The landline phone will still work as long as it's not a radio type that
needs separate power.

On 19/10/16 14:48, Another Dave wrote:

I'm the OP.

I'm working on the assumption the landline broadband will be up even if
my house is down. I thought it was a requirement that the landline had a
battery backup for emergency use by a landline-powered phone, although
admittedly the broadband may not have. Time will tell.

If I can't see a fuse in the battery circuit I'll put one in and
consider my options if it blows.

Another Dave

--
Change nospam to techie

On 20/10/2016 12:39, Another Dave wrote:
On 19/10/16 14:48, Another Dave wrote:

I'm the OP.

I'm working on the assumption the landline broadband will be up even if
my house is down. I thought it was a requirement that the landline had a
battery backup for emergency use by a landline-powered phone, although
admittedly the broadband may not have. Time will tell.

If I can't see a fuse in the battery circuit I'll put one in and
consider my options if it blows.

Another Dave

Ok, but...:

It hasn't worked that way with all of the routers that I've had.
When the power supply went off the router went off with it.

On 20/10/2016 12:39, Another Dave wrote:
On 19/10/16 14:48, Another Dave wrote:

I'm the OP.

I'm working on the assumption the landline broadband will be up even if
my house is down. I thought it was a requirement that the landline had a
battery backup for emergency use by a landline-powered phone, although
admittedly the broadband may not have. Time will tell.

If I can't see a fuse in the battery circuit I'll put one in and
consider my options if it blows.

Another Dave


There is zero chance the broadband will have battery backup.
Do you pay extra for it to have?
They don't need to and they aren't a charity.

On Thursday, 20 October 2016 00:37:59 UTC+1, Lee wrote:
On 20/10/2016 00:23, Rod Speed wrote:
Lee wrote

try hooking up a discharged 7AH and 100AH battery to a 100A charger
and tell me they take the same charge current

They do.

Better tell my 100A charger and my multimeter then, because they
disagree with you.

Everything disagrees with Rodney. He's right but real world objects like multimeters are too clueless to notice.


NT

On Thursday, 20 October 2016 03:41:26 UTC+1, Rod Speed wrote:

Which would depend on the Ah rating of the battery.

I'm not convinced that it can't supply 10A forever or close to that.

On Thursday, 20 October 2016 16:11:26 UTC+1, wrote:
On Thursday, 20 October 2016 03:41:26 UTC+1, Rod Speed wrote:

Which would depend on the Ah rating of the battery.

I'm not convinced that it can't supply 10A forever or close to that.

I thought lead acid was abotu 40% efficint as far ar geting Ah calculated.

That means a 100 Ah battery at 12V is only going to give you about 60Ah at 12v then it starts to drop off especailly if connected to an inverter, although it does depend on the condition of the battery and cables.
Canal Boat owners know a lot about this which is why they like 200+Ah batteries and higher. secondhand taxi batteries are used if yuo cant afford the cost of new 200Ah batts.
But if anyone thinks you can get 100Ah out of a 100Ah battery is wishing batteries were 100% effcient even when new it just doesn't work like that.

On Wed, 19 Oct 2016 15:21:13 +0100, Zephirum wrote:

On 19 Oct 2016 14:48, Another Dave wrote:
To provide backup during power cuts (to my shame I can't live without
broadband) I'm thinking of buying one these:

http://preview.tinyurl.com/h8kw2ln

It's a UPS circuit designed to charge a lead acid battery (not
supplied)
and to maintain 12V in case of a power cut. It seems to be ideal for my
purposes as I have an 85AH leisure battery to hand.

However the spec says, quaintly, "It is allowed to connect batteries
that is below 12V 20AH".

It's been decades since I did any electronics but I don't understand
the limit. Surely, other than that it will take a long time to charge a
big battery (of no concern to me), what harm can come from using the
85AH battery? I will, of course, be sure not to exceed the current
limit.

Another Dave
It does not imply nor indeed state to my mind that bigger batteries are
bad merely that smaller are acceptable in what I taker to be some
translation from another language? Some chargers might overcharge
smaller capacity batteries?

If you can read past the Chinglish translation, it appears to be more
than just a simple battery charger for float charging a 12v L/A battery
to which you also directly connect the 'protected' load (as in a simple
homebrewed 12vdc UPS set up).

Interestingly, I noted the use of 13.5 volts[1] instead of the more
typical 13.8 volts float charging level used by virtually every UPS
manufacturer for each half dozen SLA cell's worth of battery - a float
charge voltage level that I've come to suspect as being the main reason
for the limited 3 to 5 year service life of a typical UPS battery pack
whether they sit idle or are actually used in anger during a mains outage
(and also the reason why substituting SLAs with cheap car batteries
results in a set of knackered car batteries in a mere 6 to 12 months!).

The protected load is connected to terminals on the UPS charger rather
than directly to the battery terminals so it's quite clear that it
contains a battery undervolt load shedding switch (relay or solid state)
to save the battery from being over-discharged and suffering sulphation
damage as a result. The 10v cut-off corresponds to the 20.2 and 40.4 volt
cut-off voltages I've measured with APC SmartUPS700 (24v BP) and an APC
SmartUPS2000 (48v BP) units.

The major difference between this unit and a classic UPS supplying
ersatz mains power during an outage to IT kit which uses this ersatz
source of mains voltage to provide low voltage DC to power the actual
electronic loads is the elimination of "The Middleman" 12vdc to 230vac
inverter and its attendant conversion losses.

Virtually every bit of wall wart powered IT kit can be powered from a
standard 12vdc almost regardless of the claimed dc input voltage
requirement.

Indeed, there was one piece of kit that I had (still have?), after I'd
checked it out, which had been designed for 7.5 vac power input from a
cheap transformer only wallwart, which worked perfectly fine with dc
input voltages ranging from 7.5 to 12v dc, drawing less current as the
voltage was increased - a sure fire sign of the use of a switching
regulator after the fullwave rectifier and 25v rated smoothing cap that
had been incorporated to save the need of having these space consuming
components in the wallwart itself thus reducing the wallwart to nothing
more complex than a simple overheat protected mains to 7.5v transformer
no longer subjected to the heat from the additional rectifier components.

Since most SoHo ethernet switches and routers are powered from wallwarts
providing 'stated' dc input voltages ranging from 6 to 12 volts, this "12
volt UPS" can be the ideal solution to keeping your LAN and internet
connections up and running during protracted mains outages without adding
to the loading on a more conventional mains voltage supply UPS used to
protect desktop PCs against sudden loss of power.

As for the choice of battery, that depends on how much run time you feel
is desirable which, in turn, depends on the total protected load (which
might range from as little as 24 watts (a couple of ethernet switches and
a VM SuperHub2 for example) to maybe as much as 50 watts in a more
ambitious SoHo environment (ymmv- you'd have to measure the total
consumption of all of this "12 volt powered" kit to get the actual figure
by which to calculate an autonomy rating).

I'd say that that 'under-used' 85AH 'leisure battery' is just crying out
to be pressed into such service. As someone else mentioned, you're well
advised to use a fused connection to the battery to minimise the risk of
a house fire.

I used a 100A exchange rack fuse bolted to the positive terminal of the
200AH 12v battery I used to use as my shack supply which supplied a bank
of DC circuit breakers feeding my 12v powered amateur radio kit. This was
simply to eliminate the risk of a battery explosion should the heavy duty
cable feeding my bank of circuit breakers be shorted out.

The load was otherwise connected directly to the battery so had no
automated over-discharge protection, relying on manual intervention to
avoid this undesired state (the packet radio set up only took a tiny
fraction over an amp so could be run for just over a week on battery
power alone in this case).

If your load on the protected 12 volt supply is, say, just three amps,
you'll have a charging current reserve of 7 amps which is enough to fully
charge (well, 90% or so) that 85AH leisure battery from flat in just 12
hours!

With a specified charging voltage of 13.5 volts, there's very little
danger (compared to the 13.8v choice) of corrosion damage to the plates.
However, I suspect the 13.8v level chosen by the UPS manufacturers was a
choice determined by the maximum they could get away with in order to
maximise the effective battery capacity for a minimum 3 to 5 year service
life to 'plump up' their autonomy ratings whilst minimising initial
battery costs.

I reckon that if the UPS manufacturers were to "Do The Right Thing" and
use 13.5 volts instead, they'd either have to deflate their autonomy
claims by 10 to 15 percent or else specify a 10 to 15 percent larger
capacity battery pack to compensate (and effectively triple the service
life of said battery packs to reduce the overall total costs of
ownership).

[1] I've been keeping a 12v 12AH SLA parked on my office window ledge for
some 4 or 5 years now (a 5 quid 2nd hand purchase from a local flea
market). When I rechecked the voltage on getting it home, it was barely
above the 12v mark so flatter than the 13.something reading I'd observed
with a borrowed DMM at the time of purchase (I guess I must have missed
the low batt indicator on the dmm which would have accounted for the over-
reading).

Anyhow, since I didn't have an actual 13.8v charger I could safely
charge this from, I hung one of those 1.5Wpp solar panels out of the
office window to catch the afternoon sun to use as a battery charger. It
took about a fortnight to fully charge as indicated by the voltage
hitting the 14v mark and over before I disconnected it. The voltage
settled down to 12.78v, dropping to 12.75v a few months later where it
more or less stayed until the next round of late Spring/early Summer
sunshine by which to apply another dose of 'refreshing' charge.

In between times, I had used it now and again as a test supply as well
as checking it with a 55W quartz lamp capsule from time to time to
confirm that there was more than just voltage alone in the battery.
Indeed, a year or two later, I got to use it to jump start the wife's car
(an Astra 1.6 automatic with a totally knackered battery) so it certainly
seemed to be in very good condition all things considered. Indeed, having
receiving its annual solar panel refreshing charge about 4 or 4 months
ago, it's now showing a voltage of 12.88 volts (and still lights the 55W
test lamp with no signs of fade during the brief 10 seconds or so test -
I don't want to "burn up" charge/discharge cycles, just do a brief test
to confirm it hasn't "dried out" and gone high resistance).

The point of mentioning this is that I think keeping a 12v SLA on a
permanent 13.8v float charge year in, year out, does far more harm than
simply charging them right up on a 13.8v charger once a year and leaving
them sat on a shelf for the rest of the year.

The big problem with lead acid batteries is finding the optimum float
charge voltage, too high and it'll suffer corrosion, too low and it
suffers sulphation. The fact that this 12AH SLA has done quite nicely out
of being left to 'float' at a mere 12.75 volts for more than 11 months at
a time suggests to me that the lower 13.5 volts is still way more than
ample to keep the battery in a fully charged state (perhaps effectively
just 90 to 95 percent of that resulting from a float charge voltage of
13.8 volt) without excessive corrosion taking place.

IOW, use a lower voltage to sacrifice a few percent of effective
capacity for the benefit of extending the service life by a factor of two
to four times that seen when using the higher 13.8v charging regime
employed by the UPS manufacturers who are only concerned that the buyer
doesn't discover the "Squeeze the most autonomy out of the minimum
required battery capacity when charged at the maximum short term safe
float voltage" deceit until well after the warranty period has expired.

Battery packs are to UPS manufacturers what inkjet cartridges are to
inkjet printer manufacturers. I think the secret to getting a ten years
or longer life out of a UPS battery pack is to (where possible) adjust
the universal 13.8v per 6 cells float voltage setting to the less
aggressive 13.5 volt level. The fact that the "12 volt UPS" in question
is already set to this lower voltage suggests that this theory (untested
as yet by me) has validity.

I'm certainly encouraged to try out a *third* set of cheap car batteries
to place my SmartUPS2000 back into service again. This time I'll be
reducing the 55.5v float charge voltage (intended to have been 55.2
volts, btw) to a mere 54.0 volts. This isn't a very large reduction but
it can make a critical difference to batteries that were never intended
to be kept on a permanent 13.8 volt float charging regimen in the first
place (leisure batteries are better optimised for such permanent float
charging but they're more expensive than normal car batteries and almost
as costly as those expensive SLA battery packs being pushed by the UPS
makers).

--
Johnny B Good

On Thu, 20 Oct 2016 10:41:47 +0100, Bod wrote:

On 20/10/2016 09:23, Rod Speed wrote:


"Bod" wrote in message
...
On 20/10/2016 07:31, Brian Gaff wrote:
You have not considered one thing in this scenario. I know that many
of the
broad band cabinets which Virgin uses are powered by mains with no
back ups,
so at least in SW London, when the power is off where the cabinet
is, both
phone and broadband go off as does the TV cable service.
It could well be that BT the other supplier of the Fibre connections to
these boxes do the same for broadband. You would need to find out in
some
way before wasting your money on back up supplies.
Brian

When our power has gone off in the past, I just use the laptop which
will last for about 5 hours on battery and tether my mobile phone to
the laptop which gets me back online.

That only works when the mobile bases have battery backup.

Luckily I get a good 4G signal of up to 92Mbps down and 33 up.

I do too, and the FTTN broadband has battery backup too.

I assumed that the original poster was talking about his landline
broadband going down.
It would be very unlikely for the landline broadband to go down at the
same time as the mobile broadband signal.
Well that coincidence has never happened here so far.

Why would it be a coincidence? If both run off the mains and the mains goes off, they both go off.

--
Peter is listening to "DJ Markski - Ski Mix Volume 51"

"Bod" wrote in message
...

When our power has gone off in the past, I just use the laptop which
will last for about 5 hours on battery and tether my mobile phone to
the laptop which gets me back online.

That only works when the mobile bases have battery backup.

Luckily I get a good 4G signal of up to 92Mbps down and 33 up.

I do too, and the FTTN broadband has battery backup too.

I assumed that the original poster was talking about his landline
broadband going down.

He was actually talking about the mains going down
and his landline broadband still being available.

It would be very unlikely for the landline broadband to go down at the
same time as the mobile broadband signal.

Depends on how the landline broadband is done.

Plenty of places have that done by a RIM or CMUX
and those don’t necessarily have battery backup
and plenty of mobile bases don’t either, so you
can see them both stop on a mains failure.

Well that coincidence has never happened here so far.

Yes, some mobile bases do have battery backup.

I also have a battery power pack for the laptop which will give me
another few hours and also a power pack for the mobile phone.

You can need it for the mobile phone. Plenty of them run the
battery down pretty quickly when they are used as a hotspot.

What do you mean by "Depends on how the landline broadband is done"?

It can be done in a variety of ways. Some of it is done in the telephone
exchange with a DSLAM in the telephone exchange. Telephone exchanges
so mostly have full battery backup and quite a bit of the time a ****ing
great generator too which allows them to continue to provide phone
and broadband services during a mains failure.

With consumers who are further away from the telephone exchange,
there are a variety of ways they are supplied with phone and broadband
services over the copper pairs to the consumers. That can be using
smaller telephone exchanges that look like a large shed or a shipping
container. Those normally do have batterys too, but normally don’t
have generators.

And there are also devices called RIMs and CMUXes which are
much smaller, anything from big metal cabinets about 6' high
to smaller ones that are only about 4' high. Those may or may
not have batterys and never have permanent generators.

Those are often called nodes with fiber broadband.

If my electricity gets cut off, the modem/router won't work.

But will if you power it from a UPS or generator.

The landline phone will still work as long as it's not a radio type that
needs separate power.

Yes, landline phones traditionally do keep working
when the mains is no longer available, due to the
batterys and generators in the telephone exchange.

But its more complicated than that when the phone
service is supplied by a RIM or CMUX, most of those
do have internal batterys that allow them to continue
without mains power but not all of them do.

"Bod" wrote in message
...
On 20/10/2016 12:39, Another Dave wrote:
On 19/10/16 14:48, Another Dave wrote:

I'm the OP.

I'm working on the assumption the landline broadband will be up even if
my house is down. I thought it was a requirement that the landline had a
battery backup for emergency use by a landline-powered phone, although
admittedly the broadband may not have. Time will tell.

If I can't see a fuse in the battery circuit I'll put one in and
consider my options if it blows.

Another Dave

Ok, but...:

It hasn't worked that way with all of the routers that I've had.
When the power supply went off the router went off with it.

Trivially fixed by having the router on the same UPS etc
that the desktop etc is power from when the mains is down.