http://i912.photobucket.com/albums/a...r/IMG_3573.jpg

A neighbour has dropped in with his discharged and dead "RAC Portable
Power Station and Engine Starter" which he obtained without the
necessary DC charger. The starter is a dayglo orange heavy thing with a
handle and says it can crank 400 Amps.

Anyway, written on the front of the DC input socket, it claims it needs
16V - so I've got it charging up of one of my laboratory supplies set at
that.

Initially connecting it up, it was was drawing about 100mA. After 5
hours it's now drawing 400mA. Must have some 'inteligence' in it.

So I'd guess a 16V 500mA adaptor (or thereabouts) would be a suitable
replacement. But to check if anyone has one of these, could ye check
what's written on the mains adaptor? And can find for reference the user
instructions?

Thanks.

--
Adrian C

In article ,
Adrian C wrote:
Anyway, written on the front of the DC input socket, it claims it needs
16V - so I've got it charging up of one of my laboratory supplies set at
that.

Initially connecting it up, it was was drawing about 100mA. After 5
hours it's now drawing 400mA. Must have some 'inteligence' in it.

If the internal lead acid battery was very flat, this is what happens. The
internal resistance goes high. As it charges, it comes down to where it
should be. FWIW the SLAs used on these won't supply starting current very
often. Perhaps a half dozen times or so before they no longer manage the
full amount. But can limp on as just a portable 12v DC supply for quite
some time.

So I'd guess a 16V 500mA adaptor (or thereabouts) would be a suitable
replacement. But to check if anyone has one of these, could ye check
what's written on the mains adaptor? And can find for reference the user
instructions?

My Lidl one has a 1000 mA wall wart. I can look at its spec if you want.

--
*I'm pretty sure that sex is better than logic, but I can't prove it.

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

Adrian C expressed precisely :
Initially connecting it up, it was was drawing about 100mA. After 5 hours
it's now drawing 400mA. Must have some 'inteligence' in it.

That is the usual behaviour of a completely flat lead acid battery,
rather than any built in intelligence. My (not RAC) unit has an
automatic charger built in, which cuts it off once the fully charged
voltage is reached, but yours might not do that (look for an LED marked
charged)- so it might need to be carefully matched in voltage output.
It lights up as soon as powered, then goes out once fully charged and
stays out until powed down and up again.

It's charger suggests it is 18v 0.75amp DC. If yours lacks the charge
control built in, you need a voltage controlled PSU of around 13.8 to
14.2v.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

In article ,
Dave Plowman (News) wrote:
So I'd guess a 16V 500mA adaptor (or thereabouts) would be a suitable
replacement. But to check if anyone has one of these, could ye check
what's written on the mains adaptor? And can find for reference the
user instructions?

My Lidl one has a 1000 mA wall wart. I can look at its spec if you want.

It's actually marked 12 volt DC 1000mA. So must be a very nominal 12
volts. ;-)

--
*The longest recorded flightof a chicken is thirteen seconds *

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

On 02/12/2010 17:44, Dave Plowman (News) wrote:
In ,
Dave Plowman wrote:
So I'd guess a 16V 500mA adaptor (or thereabouts) would be a suitable
replacement. But to check if anyone has one of these, could ye check
what's written on the mains adaptor? And can find for reference the
user instructions?

My Lidl one has a 1000 mA wall wart. I can look at its spec if you want.

It's actually marked 12 volt DC 1000mA. So must be a very nominal 12
volts. ;-)


Thanks for checking.

Something unregulated rated at anything past 12V rated at an amp or more
might just fit the task, and be easier to find in the junk pile than
something unregulated and small with specifically 16V stamped on it.

He'll go for that :-)

--
Adrian C

Adrian C has brought this to us :
Thanks for checking.

Something unregulated rated at anything past 12V rated at an amp or more
might just fit the task, and be easier to find in the junk pile than
something unregulated and small with specifically 16V stamped on it.

12v or even 13.5v will not put a charge into a 12v lead acid battery,
it needs to be in the range 13.8 to 14.2v

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

Adrian C wrote:


http://i912.photobucket.com/albums/a...r/IMG_3573.jpg

A neighbour has dropped in with his discharged and dead "RAC Portable
Power Station and Engine Starter" which he obtained without the
necessary DC charger. The starter is a dayglo orange heavy thing with a
handle and says it can crank 400 Amps.

Anyway, written on the front of the DC input socket, it claims it needs
16V - so I've got it charging up of one of my laboratory supplies set at
that.

Initially connecting it up, it was was drawing about 100mA. After 5
hours it's now drawing 400mA. Must have some 'inteligence' in it.

So I'd guess a 16V 500mA adaptor (or thereabouts) would be a suitable
replacement. But to check if anyone has one of these, could ye check
what's written on the mains adaptor? And can find for reference the user
instructions?

Thanks.

These days battery chargers are very sophisticated things in how they
treat batteries. If your friend has more than one battery to care for,
an Optimate or Accumate charger might be a good idea, but they aren't
cheap.

TF

On 02/12/2010 18:52, Harry Bloomfield wrote:
Adrian C has brought this to us :
Thanks for checking.

Something unregulated rated at anything past 12V rated at an amp or
more might just fit the task, and be easier to find in the junk pile
than something unregulated and small with specifically 16V stamped on it.

12v or even 13.5v will not put a charge into a 12v lead acid battery, it
needs to be in the range 13.8 to 14.2v


A biggish transformer marked 12v lightly loaded will be supplying that
and more easily. Got no worries about that (and as I said easier for me
to find).

Cheers

--
Adrian

In article ,
Terry Fields wrote:
These days battery chargers are very sophisticated things in how they
treat batteries. If your friend has more than one battery to care for,
an Optimate or Accumate charger might be a good idea, but they aren't
cheap.

No need to pay silly prices for a sophisticated battery charger. Lidl and
Aldi in the UK both do similar ones for about 14 gbp. They pulse charge a
flat battery, change to a normal charge, then switch to a maintenance one.
Get the same thing with a 'name' on it and you'll pay four times as much.

--
*They call it PMS because Mad Cow Disease was already taken.

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

Dave Plowman (News) wrote:
In article ,
Terry Fields wrote:
These days battery chargers are very sophisticated things in how they
treat batteries. If your friend has more than one battery to care for,
an Optimate or Accumate charger might be a good idea, but they aren't
cheap.

No need to pay silly prices for a sophisticated battery charger. Lidl and
Aldi in the UK both do similar ones for about 14 gbp. They pulse charge a
flat battery, change to a normal charge, then switch to a maintenance one.
Get the same thing with a 'name' on it and you'll pay four times as much.


Or get a decent RC charger for silly money

http://www.alwayshobbies.com/Boats/Radio-Control-Equipment/Cells$1Chargers/Chargers/Logic-Fusion-NX81-Variable-Output-AC-Delta-Peak-Charger.ice

variable rate 4-8 cells and hardly bank breaking.

On Dec 2, 10:01*am, Adrian C wrote:
http://i912.photobucket.com/albums/a...r/IMG_3573.jpg

A neighbour has dropped in with his discharged and dead "RAC Portable
Power Station and Engine Starter" which he obtained without the
necessary DC charger. The starter is a dayglo orange heavy thing with a
handle and says it can crank 400 Amps.

Anyway, written on the front of the DC input socket, it claims it needs
16V - so I've got it charging up of one of my laboratory supplies set at
that.

Initially connecting it up, it was was drawing about 100mA. After 5
hours it's now drawing 400mA. Must have some 'inteligence' in it.

So I'd guess a 16V 500mA adaptor (or thereabouts) would be a suitable
replacement. But to check if anyone has one of these, could ye check
what's written on the mains adaptor? And can find for reference the user
instructions?


My Silverline 38Ah Jump starter -- and yes, unlike an awful lot of
these things, it actually works and will start a 2.5 litre diesel with
a flat battery -- has a charger that's marked 15v 500mA.

Dave Plowman (News) wrote:

In article ,
Terry Fields wrote:

These days battery chargers are very sophisticated things in how they
treat batteries. If your friend has more than one battery to care for,
an Optimate or Accumate charger might be a good idea, but they aren't
cheap.

No need to pay silly prices for a sophisticated battery charger. Lidl and
Aldi in the UK both do similar ones for about 14 gbp. They pulse charge a
flat battery, change to a normal charge, then switch to a maintenance one.
Get the same thing with a 'name' on it and you'll pay four times as much.

As the battery in the appliance seemed to be a SLA, getting maximum
life out of it demands using an appropriate charger rather than a
random wall-wart. I use an Accumate to keep both a SLA and a
motorcycle battery in good order - I don't have any experience of the
Lidl or Aldi chargers.

TF

In article ,
Terry Fields wrote:
No need to pay silly prices for a sophisticated battery charger. Lidl
and Aldi in the UK both do similar ones for about 14 gbp. They pulse
charge a flat battery, change to a normal charge, then switch to a
maintenance one. Get the same thing with a 'name' on it and you'll pay
four times as much.

As the battery in the appliance seemed to be a SLA, getting maximum life
out of it demands using an appropriate charger rather than a random
wall-wart.

Of course. True SLA (gel) should be charged at constant voltage. They're
not so tolerant as car batteries in this respect.

I use an Accumate to keep both a SLA and a motorcycle battery
in good order - I don't have any experience of the Lidl or Aldi chargers.

These things tend to have different brand names depending on who sells
them - but most are simply a wall wart with a few pennies of extra
components. Usually not worth the premium price.

--
*I have a degree in liberal arts -- do you want fries with that

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

On Dec 3, 12:07*am, "Dave Plowman (News)"
wrote:
In article ,
* *Terry Fields wrote:

These days battery chargers are very sophisticated things in how they
treat batteries. If your friend has more than one battery to care for,
an Optimate or Accumate charger might be a good idea, but they aren't
cheap.

No need to pay silly prices for a sophisticated battery charger. Lidl and
Aldi in the UK both do similar ones for about 14 gbp. They pulse charge a
flat battery, change to a normal charge, then switch to a maintenance one..
Get the same thing with a 'name' on it and you'll pay four times as much.

--
*They call it PMS because Mad Cow Disease was already taken. *

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

The Lidl /Aldi offerings are good there is no doubt, but they are
never there when you want them !! You have to be on their mailing
list and make a judgement to buy when they are available - and then
they sit around for ages ..... until that magic moment and hey presto
they do the job. Just been there this afternoon to top up a spare car
battery just in case, using one of these I bought probably a year
ago. Serious cold now in Edinburgh and I can see some sluggish
starting coming up.

In article
,
robgraham wrote:
No need to pay silly prices for a sophisticated battery charger. Lidl
and Aldi in the UK both do similar ones for about 14 gbp. They pulse
charge a flat battery, change to a normal charge, then switch to a
maintenance one. Get the same thing with a 'name' on it and you'll pay
four times as much.


The Lidl /Aldi offerings are good there is no doubt, but they are
never there when you want them !! You have to be on their mailing
list and make a judgement to buy when they are available - and then
they sit around for ages ..... until that magic moment and hey presto
they do the job. Just been there this afternoon to top up a spare car
battery just in case, using one of these I bought probably a year
ago. Serious cold now in Edinburgh and I can see some sluggish
starting coming up.

They're cheap enough to build into the car. I've done this on my
'classic'. With a waterproof mains connector under the rear bumper.

I get emails from both Aldi and Lidl showing their offers of the week.
With some of them you have to get there early.

--
*Certain frogs can be frozen solid, then thawed, and survive *

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

On 3 Dec,
"Dave Plowman (News)" wrote:

In article ,
Terry Fields wrote:
No need to pay silly prices for a sophisticated battery charger. Lidl
and Aldi in the UK both do similar ones for about 14 gbp. They pulse
charge a flat battery, change to a normal charge, then switch to a
maintenance one. Get the same thing with a 'name' on it and you'll pay
four times as much.

As the battery in the appliance seemed to be a SLA, getting maximum life
out of it demands using an appropriate charger rather than a random
wall-wart.

Of course. True SLA (gel) should be charged at constant voltage. They're
not so tolerant as car batteries in this respect.

I use an Accumate to keep both a SLA and a motorcycle battery
in good order - I don't have any experience of the Lidl or Aldi chargers.

These things tend to have different brand names depending on who sells
them - but most are simply a wall wart with a few pennies of extra
components. Usually not worth the premium price.

My Aldi power station seems to use a basic unstabilised wall wart. However,
it seems to charge up to a reasonable voltage, then cease charging (or go to
a very low current) I've been using it to power some electronics, and I've
been monitoring its voltage. It seems to cut out somewhere between 13.5 and
14 volts.

--
B Thumbs
Change lycos to yahoo to reply

On 03/12/2010 17:17, Dave Plowman (News) wrote:

I get emails from both Aldi and Lidl showing their offers of the week.
With some of them you have to get there early.


That's because bloody market traders are queuing at the door come
opening time to snag all the best stuff!

Ron

On 12/2/2010 2:01 AM Adrian C spake thus:

http://i912.photobucket.com/albums/a...r/IMG_3573.jpg

A neighbour has dropped in with his discharged and dead "RAC Portable
Power Station and Engine Starter" which he obtained without the
necessary DC charger. The starter is a dayglo orange heavy thing with a
handle and says it can crank 400 Amps.

I'm surprised nobody has mentioned this yet in this thread, but aren't
those claims for how much current these things will deliver a lot of BS?

I first saw one of these power units a couple weeks ago, when my
neighbor used his to get my van started after he borrowed it and the
battery started going dead. He used it twice, successfully, to
jump-start my half-dead battery. So they do work, apparently. But his
was similarly marked (I think 300 amps). Is there any way that such a
small lead-acid battery could deliver this much juice? I'm skeptical.


--
How To Access Wikileaks

These sites are still up as of 12/3/10:

http://wikileaks.de
http://wikileaks.fi
http://wikileaks.nl
http://wikileaks.eu
http://wikileaks.pl

And these IP addresses can be used:

http://213.251.145.96/
http://88.80.13.160/

In article ,
David Nebenzahl wrote:
I'm surprised nobody has mentioned this yet in this thread, but aren't
those claims for how much current these things will deliver a lot of BS?

I first saw one of these power units a couple weeks ago, when my
neighbor used his to get my van started after he borrowed it and the
battery started going dead. He used it twice, successfully, to
jump-start my half-dead battery. So they do work, apparently. But his
was similarly marked (I think 300 amps). Is there any way that such a
small lead-acid battery could deliver this much juice? I'm skeptical.

They vary quite a bit in price. At the cheaper end I've found they will
deliver enough current (when new) to start a car with a flat battery - but
no more than a handful of times. No lead acid battery likes having what is
efficitively (at that size) a dead short across it. And as is common with
so many of these things the battery costs more to replace than the entire
unit.

The one I have is many years old. It won't deliver enough current to start
a car, but still is ok as a self contained compressor for the tyres. And
as a convenient portable 12 volt source for testing things - it will still
supply much more current than my bench PS. And only cost 20 quid...

--
*He loves nature in spite of what it did to him.

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

On 12/5/2010 2:49 AM Dave Plowman (News) spake thus:

In article , David
Nebenzahl wrote:

I'm surprised nobody has mentioned this yet in this thread, but
aren't those claims for how much current these things will deliver
a lot of BS?

I first saw one of these power units a couple weeks ago, when my
neighbor used his to get my van started after he borrowed it and the
battery started going dead. He used it twice, successfully, to
jump-start my half-dead battery. So they do work, apparently. But his
was similarly marked (I think 300 amps). Is there any way that such a
small lead-acid battery could deliver this much juice? I'm skeptical.

They vary quite a bit in price. At the cheaper end I've found they will
deliver enough current (when new) to start a car with a flat battery - but
no more than a handful of times.

So how much current do you think they're actually capable of
delivering--say with the little battery fairly fresh and fully charged?


--
How To Access Wikileaks

These sites are still up as of 12/3/10:

http://wikileaks.de
http://wikileaks.fi
http://wikileaks.nl
http://wikileaks.eu
http://wikileaks.pl

And these IP addresses can be used:

http://213.251.145.96/
http://88.80.13.160/

David Nebenzahl wrote:

On 12/5/2010 2:49 AM Dave Plowman (News) spake thus:

In article , David
Nebenzahl wrote:

I'm surprised nobody has mentioned this yet in this thread, but
aren't those claims for how much current these things will deliver
a lot of BS?

I first saw one of these power units a couple weeks ago, when my
neighbor used his to get my van started after he borrowed it and the
battery started going dead. He used it twice, successfully, to
jump-start my half-dead battery. So they do work, apparently. But his
was similarly marked (I think 300 amps). Is there any way that such a
small lead-acid battery could deliver this much juice? I'm skeptical.

They vary quite a bit in price. At the cheaper end I've found they will
deliver enough current (when new) to start a car with a flat battery - but
no more than a handful of times.

So how much current do you think they're actually capable of
delivering--say with the little battery fairly fresh and fully charged?


Too many variables. What is the amp hour rating of the battery?
What is the internal resistance of the switch? The resistance of the
cables? The resistance of the starter motor? The temperature? How
clean are the battery clamps, and what is the resistance of the battery
cables? The resistance of the starter solenoid?


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

In article ,
Michael A. Terrell wrote:
So how much current do you think they're actually capable of
delivering--say with the little battery fairly fresh and fully charged?


Too many variables. What is the amp hour rating of the battery?

Tiny in automotive terms.

What is the internal resistance of the switch?

Dunno

The resistance of the
cables?

Mine has 16mm² cables. The resistance of the alligator clamps is more
likely the limiting factor.

The resistance of the starter motor? The temperature? How
clean are the battery clamps, and what is the resistance of the battery
cables? The resistance of the starter solenoid?

Non of which matters since the power pack makers claim a maximum output.

--
*When you've seen one shopping centre you've seen a mall*

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

"Dave Plowman (News)" wrote:

In article ,
Michael A. Terrell wrote:
So how much current do you think they're actually capable of
delivering--say with the little battery fairly fresh and fully charged?

Too many variables. What is the amp hour rating of the battery?

Tiny in automotive terms.


Really? My jump packs have 17 Ah batteries.

Product ID: BSL1117
Cold Cranking Amps: 240
Voltage: 12
Termination: NUT & BOLT
Chemistry: SLA OR VRLA VALVE REGULATED S
Weight: 13.3
Width: 2.99
Length: 7.13
Height: 6.57


My truck uses a size 27 battery with these specs:

Product ID: MTP-27
Amps: 1000
Cranking Amps: 1000
Cold Cranking Amps: 810
Voltage: 12
Termination: A
Pro-rata Warranty: 85
Weight: 47.4
Width: 6.81
Length: 12.06
Height: 8.88


So, it has 24% of the rating of the truck battery which isn't
'tiny'. It is intended to start a vehicle with a run down battery, not
one with mechanical problems. The portable pack is designed with a
different type of battery, as well. The available current is determined
by the plate area and thickness.

I've seen someone use 12V alarm batteries to jump start a service
truck. They were rated at 7 Ah.


What is the internal resistance of the switch?

Dunno

The resistance of the
cables?

Mine has 16mm² cables. The resistance of the alligator clamps is more
likely the limiting factor.


No, all of it is important. If the resistance of the clamps is as
high as the leads, they will overheat since all the resistance is at the
same spot rather than distributed along the length of the cables.


The resistance of the starter motor? The temperature? How
clean are the battery clamps, and what is the resistance of the battery
cables? The resistance of the starter solenoid?

Non of which matters since the power pack makers claim a maximum output.


BS. They all matter, if you aren't an ignorant troll.

What do you think the short circuit current of a fully charged 12V
car battery is?


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

In article ,
Michael A. Terrell wrote:

"Dave Plowman (News)" wrote:

In article ,
Michael A. Terrell wrote:
So how much current do you think they're actually capable of
delivering--say with the little battery fairly fresh and fully
charged?

Too many variables. What is the amp hour rating of the battery?

Tiny in automotive terms.


Really? My jump packs have 17 Ah batteries.

I suppose it depends on your definition of tiny, but 17 amp.hr is a lot
smaller than any battery in any car I've owned or seen. Both my current
ones have 70 Ah types.

Product ID: BSL1117
Cold Cranking Amps: 240
Voltage: 12
Termination: NUT & BOLT
Chemistry: SLA OR VRLA VALVE REGULATED S
Weight: 13.3
Width: 2.99
Length: 7.13
Height: 6.57


My truck uses a size 27 battery with these specs:

Product ID: MTP-27
Amps: 1000
Cranking Amps: 1000
Cold Cranking Amps: 810
Voltage: 12
Termination: A
Pro-rata Warranty: 85
Weight: 47.4
Width: 6.81
Length: 12.06
Height: 8.88


So, it has 24% of the rating of the truck battery which isn't
'tiny'.

Err, you don't appear to have given the amp.hr capacity - the very thing
you mentioned.

It is intended to start a vehicle with a run down battery, not
one with mechanical problems.
The portable pack is designed with a
different type of battery, as well. The available current is determined
by the plate area and thickness.

I've seen someone use 12V alarm batteries to jump start a service
truck. They were rated at 7 Ah.

Batteries? Parallel them and they become like a larger one.


What is the internal resistance of the switch?

Dunno

The resistance of the
cables?

Mine has 16mm² cables. The resistance of the alligator clamps is more
likely the limiting factor.


No, all of it is important. If the resistance of the clamps is as
high as the leads, they will overheat since all the resistance is at the
same spot rather than distributed along the length of the cables.


The resistance of the starter motor? The temperature? How clean
are the battery clamps, and what is the resistance of the battery
cables? The resistance of the starter solenoid?

Non of which matters since the power pack makers claim a maximum
output.


BS. They all matter, if you aren't an ignorant troll.


What do you think the short circuit current of a fully charged 12V
car battery is?

Are you trolling? The maker of the jump start pack claims a maximum
current. Since they can't possibly know exactly what the starter motor etc
draw is, just how is it relevant?

My point is (with experience of several jump start packs including
expensive ones) is that they will not do lots of starts of a vehicle with
a flat battery without permanent damage to the SLA. Somewhere round a
dozen or so seems to be it.

--
*Corduroy pillows are making headlines.

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

Dave Plowman (News) wrote:

Michael A. Terrell wrote:

I suppose it depends on your definition of tiny, but 17 amp.hr is a lot
smaller than any battery in any car I've owned or seen. Both my current
ones have 70 Ah types.

Yeah, but how many minutes would your 70Ah crank for, and how many
seconds does it need to crank for (assuming there's no other problem
with the engine)?

"Dave Plowman (News)" wrote:

In article ,
Michael A. Terrell wrote:

"Dave Plowman (News)" wrote:

In article ,
Michael A. Terrell wrote:
So how much current do you think they're actually capable of
delivering--say with the little battery fairly fresh and fully
charged?

Too many variables. What is the amp hour rating of the battery?

Tiny in automotive terms.

Really? My jump packs have 17 Ah batteries.

I suppose it depends on your definition of tiny, but 17 amp.hr is a lot
smaller than any battery in any car I've owned or seen. Both my current
ones have 70 Ah types.


Gee, that's damn close to the 24% figure isn't it? 17/.24 = 70.83


Product ID: BSL1117
Cold Cranking Amps: 240
Voltage: 12
Termination: NUT & BOLT
Chemistry: SLA OR VRLA VALVE REGULATED S
Weight: 13.3
Width: 2.99
Length: 7.13
Height: 6.57

My truck uses a size 27 battery with these specs:

Product ID: MTP-27
Amps: 1000
Cranking Amps: 1000
Cold Cranking Amps: 810
Voltage: 12
Termination: A
Pro-rata Warranty: 85
Weight: 47.4
Width: 6.81
Length: 12.06
Height: 8.88

So, it has 24% of the rating of the truck battery which isn't
'tiny'.

Err, you don't appear to have given the amp.hr capacity - the very thing
you mentioned.


Very few car batteries are given an amp our rating in the US since
they are not used without a charging circuit. If you look at the given
spces you can get an idea though.


It is intended to start a vehicle with a run down battery, not
one with mechanical problems.
The portable pack is designed with a
different type of battery, as well. The available current is determined
by the plate area and thickness.

I've seen someone use 12V alarm batteries to jump start a service
truck. They were rated at 7 Ah.

Batteries? Parallel them and they become like a larger one.

What is the internal resistance of the switch?

Dunno

The resistance of the
cables?

Mine has 16mm² cables. The resistance of the alligator clamps is more
likely the limiting factor.

No, all of it is important. If the resistance of the clamps is as
high as the leads, they will overheat since all the resistance is at the
same spot rather than distributed along the length of the cables.

The resistance of the starter motor? The temperature? How clean
are the battery clamps, and what is the resistance of the battery
cables? The resistance of the starter solenoid?

Non of which matters since the power pack makers claim a maximum
output.

BS. They all matter, if you aren't an ignorant troll.

What do you think the short circuit current of a fully charged 12V
car battery is?

Are you trolling? The maker of the jump start pack claims a maximum
current. Since they can't possibly know exactly what the starter motor etc
draw is, just how is it relevant?


It is very relevant, if you stop and think about it.


My point is (with experience of several jump start packs including
expensive ones) is that they will not do lots of starts of a vehicle with
a flat battery without permanent damage to the SLA. Somewhere round a
dozen or so seems to be it.


You keep changing the subject.
--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

In article ,
Michael A. Terrell wrote:
You keep changing the subject.

Think you should re-read my posts. Perhaps you addressed your questions to
the wrong person.

--
*I couldn't repair your brakes, so I made your horn louder *

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

In article ,
Michael A. Terrell wrote:
Very few car batteries are given an amp our rating in the US since
they are not used without a charging circuit.

Great. So never used with the engine stopped? All car batteries in the UK
have the amp.hour marked on them. As well as max current, etc.

I have an electronic battery tester - an expensive device. This gives a
instantaneous readout of the capacity in amp.hours. If you don't know what
it should be it is fairly useless.

--
*I brake for no apparent reason.

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

On 12/6/2010 8:58 AM Michael A. Terrell spake thus:

"Dave Plowman (News)" wrote:

In article ,
Michael A. Terrell wrote:

[I wrote:]

So how much current do you think they're actually capable of
delivering--say with the little battery fairly fresh and fully
charged?

Too many variables. What is the amp hour rating of the battery?

Tiny in automotive terms.


Really? My jump packs have 17 Ah batteries.

Product ID: BSL1117
Cold Cranking Amps: 240
Voltage: 12
Termination: NUT & BOLT
Chemistry: SLA OR VRLA VALVE REGULATED S
Weight: 13.3
Width: 2.99
Length: 7.13
Height: 6.57


My truck uses a size 27 battery with these specs:

Product ID: MTP-27
Amps: 1000
Cranking Amps: 1000
Cold Cranking Amps: 810
Voltage: 12
Termination: A
Pro-rata Warranty: 85
Weight: 47.4
Width: 6.81
Length: 12.06
Height: 8.88


So, it has 24% of the rating of the truck battery which isn't
'tiny'. It is intended to start a vehicle with a run down battery, not
one with mechanical problems. The portable pack is designed with a
different type of battery, as well. The available current is determined
by the plate area and thickness.

OK, your impeccable documentation has won me over. I withdraw my
objection; the current claims on those jump-packs (300 amps, 400 amps)
must be believable after all. I'm a little surprised, though.


--
How To Access Wikileaks

These sites are still up as of 12/3/10:

http://wikileaks.de
http://wikileaks.fi
http://wikileaks.nl
http://wikileaks.eu
http://wikileaks.pl

And these IP addresses can be used:

http://213.251.145.96/
http://88.80.13.160/

In the case of the Schumacher IP-55 model (12V 4Ah battery) the descriptive
term that's not been mentioned so far, is 400A Peak, for this model.

Manufacturers know that Peak is a (multi)million dollar word, whether it's
used with watts, HP, or amps.. because Peak distorts actual specifications.
Consumers love big numbers, and manufacturers know it.

With a properly rated current shunt, and a peak-reading amp meter attached,
one could determine the peak current available from such a small battery.

As Dave P points out, the number of times that a small battery can deliver
the somewhat severe duty discharge rates, is going to be a very limited
number of times.

I didn't purchase this Schumacher power pack as an emergency car battery
jump pack, but instead, only as a portable power supply.

--
Cheers,
WB
..............


"David Nebenzahl" wrote in message
.com...

OK, your impeccable documentation has won me over. I withdraw my
objection; the current claims on those jump-packs (300 amps, 400 amps)
must be believable after all. I'm a little surprised, though.

In article ,
Wild_Bill wrote:
As Dave P points out, the number of times that a small battery can
deliver the somewhat severe duty discharge rates, is going to be a very
limited number of times.

That was really the only point I was trying to make. The output from my
cheap one was enough to start a car on a few occasions - then not. What
the actual peak power is/was didn't much concern me.

I didn't purchase this Schumacher power pack as an emergency car battery
jump pack, but instead, only as a portable power supply.

Mine - despite being quite a few years old - is still fine for this, with
the battery holding its charge well. It also has a built in compressor, so
gets used for tyres. Slow, but does it.

It was remarkable value. Any cordless power tool of its age would have had
a dead battery long since.

--
* I like you. You remind me of when I was young and stupid

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

In article ,
David Nebenzahl wrote:
OK, your impeccable documentation has won me over. I withdraw my
objection; the current claims on those jump-packs (300 amps, 400 amps)
must be believable after all. I'm a little surprised, though.

I used to work in a TV production facility where some of the prog was made
in the 'studio' - some on location. So there was a fleet of small trucks
used just for this location work. That location might only be a few
minutes drive away. And the trucks left unused at other times. So by
nature many suffered from flat batteries just when needed.

The availability of cheap jump start packs was very appealing. Easy to
store and carry. But in practice, even with the low cost, weren't reliable
enough. So units were made up using a sack trolley and car battery with a
charger attached. So the same sort of idea only larger.

--
*Also too, never, ever use repetitive redundancies *

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

"Dave Plowman (News)" wrote:

In article ,
Michael A. Terrell wrote:
Very few car batteries are given an amp our rating in the US since
they are not used without a charging circuit.

Great. So never used with the engine stopped?


Sure, but vehicles that are used that way on a regular basis can have
a dual battery system so the starter is on a separate battery. I first
installed some on a pair of large paddle boats at an amusement park in
the early '70s so they could run cart machines for the music while the
283 CID V8 engines were shut down.

All car batteries in the UK
have the amp.hour marked on them. As well as max current, etc.


What good does that do the average owner? Do they stand around bars
playing 'My dick is bigger' over car batteries?


I have an electronic battery tester - an expensive device. This gives a
instantaneous readout of the capacity in amp.hours. If you don't know what
it should be it is fairly useless.


Instantaneous? Right. It gives an WAG. Battery testers have been
around for generations. Just because they add a little electronics
doesn't make them magic. Does your car battery tell you the discharge
rate to achieve the marked Ah rating?


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

"Dave Plowman (News)" wrote:

In article ,
David Nebenzahl wrote:
OK, your impeccable documentation has won me over. I withdraw my
objection; the current claims on those jump-packs (300 amps, 400 amps)
must be believable after all. I'm a little surprised, though.

I used to work in a TV production facility where some of the prog was made
in the 'studio' - some on location. So there was a fleet of small trucks
used just for this location work. That location might only be a few
minutes drive away. And the trucks left unused at other times. So by
nature many suffered from flat batteries just when needed.

The availability of cheap jump start packs was very appealing. Easy to
store and carry. But in practice, even with the low cost, weren't reliable
enough. So units were made up using a sack trolley and car battery with a
charger attached. So the same sort of idea only larger.


In the US you can find a combination battery charger & large lead
acid battery built to jump start vehicles. Garages use them, and I've
seen them at large malls. The charge can put out enough current to
start a typical vehicle but if no AC is available they use the battery.


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

In article ,
Michael A. Terrell wrote:
I have an electronic battery tester - an expensive device. This gives
a instantaneous readout of the capacity in amp.hours. If you don't
know what it should be it is fairly useless.


Instantaneous? Right. It gives an WAG. Battery testers have been
around for generations. Just because they add a little electronics
doesn't make them magic.

You don't half talk rubbish. Battery testers used to be large devices.
This is the size of a DVM. And gives an accurate readout of the overall
battery condition. Not just its voltage or how much current it can
deliver. It's invaluable for quick testing of a lead acid battery.

Does your car battery tell you the discharge
rate to achieve the marked Ah rating?

It's also a standard in the UK. 20 hour rate.

--
*Wedding dress for sale. Worn once by mistake.*

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

"Dave Plowman (News)" wrote:

In article ,
Michael A. Terrell wrote:
I have an electronic battery tester - an expensive device. This gives
a instantaneous readout of the capacity in amp.hours. If you don't
know what it should be it is fairly useless.

Instantaneous? Right. It gives an WAG. Battery testers have been
around for generations. Just because they add a little electronics
doesn't make them magic.

You don't half talk rubbish. Battery testers used to be large devices.
This is the size of a DVM. And gives an accurate readout of the overall
battery condition. Not just its voltage or how much current it can
deliver. It's invaluable for quick testing of a lead acid battery.


Then explain how it can determine the Ah rating. it sounds like it
tests the battery's ESR and guesses the Ah rating.


Does your car battery tell you the discharge
rate to achieve the marked Ah rating?

It's also a standard in the UK. 20 hour rate.


So you can leave your headlights on for 20 hours with no problems?


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

I have an electronic battery tester -- an expensive device.
This gives a instantaneous readout of the capacity in Ah.
If you don't know what it should be it is fairly useless.

You cannot take an "instantaneous" reading of a cell's Ah capacity. Such a
measurement requires actually draining the battery.

In article ,
Michael A. Terrell wrote:
You don't half talk rubbish. Battery testers used to be large devices.
This is the size of a DVM. And gives an accurate readout of the overall
battery condition. Not just its voltage or how much current it can
deliver. It's invaluable for quick testing of a lead acid battery.


Then explain how it can determine the Ah rating. it sounds like it
tests the battery's ESR and guesses the Ah rating.

It doesn't 'guess' anything. It gives a pretty accurate reading. I'd
suggest you find out for yourself how they work.

Does your car battery tell you the discharge
rate to achieve the marked Ah rating?

It's also a standard in the UK. 20 hour rate.


So you can leave your headlights on for 20 hours with no problems?

So you've no clue *either* about how battery capacity is measured?

Hint. Headlights on dip (and the other lights which will be on with them)
amount to around a 12 amp load. That's with 55 watt tungsten headlights.
At a 20 hour rate that would suggest a 240 amp.hour battery just for them
still to be sort of working. But not without problems. Please try it on
your car.

--
*Succeed, in spite of management *

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

In article ,
William Sommerwerck wrote:
I have an electronic battery tester -- an expensive device.
This gives a instantaneous readout of the capacity in Ah.
If you don't know what it should be it is fairly useless.

You cannot take an "instantaneous" reading of a cell's Ah capacity. Such
a measurement requires actually draining the battery.

I dunno how it actually achieves this, but in practice it's what it does.
And is pretty accurate if you check it against doing an actual discharge.
Nor does it need the battery to be fully charged to test it.

I've used it on many batteries of different capacities - and on known
good ones gives a readout within something like 5% of the stated capacity.
Unless the charge is too low for it to work.

For me, it's invaluable.

--
*Puritanism: The haunting fear that someone, somewhere may be happy.

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

While we're on batteries...

Yesterday whiel doing a perfunctory cleanup I came across the Canon 580EX II
flash I'd packed in a carrying case (when visiting a friend) almost a year
ago. The 2700 mAh NiMH PowerEx (MAHA) cells had not been charged since then.
When I turned the flash on, it came to full charge in less than three
seconds.

The cells measured 1.274V, 1.283V, 1.285V, and 1.286V, all higher than the
nominal 1.25V of a NiMH cell. (NiMHs generally come out of a full charge at
around 1.4V.) That's pretty good performance for a cell that's supposed to
"drop dead" within a few weeks of its last charge.

So I ask... Where did this belief that NiMH cells rapidly self-discharge
come from? I never believed it, and here's strong evidence it just isn't
true.