old tractor, 2 x 12v biggish batteries linked in parallel provide
the power to start.

Only used for fetching haylage once a week so batteries often
don't start it the next time....

Is it OK to just charge the pair of batteries by clipping on a
battery charger, without disconnecting the interconnecting
wiring?

Or is it necessary or advisable (and why please) to electrically
isolate each and charge one at a time?

For longer term would a solar trickle charger be worthwhile?

TIA
--
Jim K


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

On 13/12/2016 18:14, jim wrote:

old tractor, 2 x 12v biggish batteries linked in parallel provide
the power to start.

Only used for fetching haylage once a week so batteries often
don't start it the next time....

Is it OK to just charge the pair of batteries by clipping on a
battery charger, without disconnecting the interconnecting
wiring?

Or is it necessary or advisable (and why please) to electrically
isolate each and charge one at a time?

For longer term would a solar trickle charger be worthwhile?

TIA

Assuming that they are in parallel and it isn't a 24V vehicle...

They get charged and discharged together by the vehicle, so you might as
well do the same with an external charger. I suppose you could check
periodically whether there's an imbalance if you were bothered, but
really once you suspect a battery is knackered replace them both. Stands
to reason the new ones should be identical.

Bill

Bill Wright Wrote in message:
On 13/12/2016 18:14, jim wrote:

old tractor, 2 x 12v biggish batteries linked in parallel provide
the power to start.

Only used for fetching haylage once a week so batteries often
don't start it the next time....

Is it OK to just charge the pair of batteries by clipping on a
battery charger, without disconnecting the interconnecting
wiring?

Or is it necessary or advisable (and why please) to electrically
isolate each and charge one at a time?

For longer term would a solar trickle charger be worthwhile?

TIA

Assuming that they are in parallel and it isn't a 24V vehicle...


Lead from +ve1 to +ve2 and 2x -ves commoned to the metalwork.


They get charged and discharged together by the vehicle, so you might as
well do the same with an external charger. I suppose you could check
periodically whether there's an imbalance if you were bothered, but
really once you suspect a battery is knackered replace them both. Stands
to reason the new ones should be identical.

Bill

Makes sense!
Thanks
--
Jim K


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

On 13/12/2016 18:46, jim wrote:

Lead from +ve1 to +ve2 and 2x -ves commoned to the metalwork.


They get charged and discharged together by the vehicle, so you might as
well do the same with an external charger. I suppose you could check
periodically whether there's an imbalance if you were bothered, but
really once you suspect a battery is knackered replace them both. Stands
to reason the new ones should be identical.

Bill

Makes sense!
Thanks

I suppose it's important that any leads and connectors that aren't
common to both batteries are perfectly clean, to avoid a situation where
one battery is a 'passenger'.

I mean the battery terminals, mainly.

Bill

On 12/13/2016 6:14 PM, jim wrote:

old tractor, 2 x 12v biggish batteries linked in parallel provide
the power to start.

Only used for fetching haylage once a week so batteries often
don't start it the next time....

Is it OK to just charge the pair of batteries by clipping on a
battery charger, without disconnecting the interconnecting
wiring?

Or is it necessary or advisable (and why please) to electrically
isolate each and charge one at a time?

For longer term would a solar trickle charger be worthwhile?

TIA

With this arrangement, isn't there a danger that if one battery
deteriorates (e.g. a cell shorting out) it will knacker the good one?

As others have said, since the generator charges them like this there's
no reason not to do the same with an external charger.

Was this the original arrangement or is it a later bodge? I think if it
was mine I would fit a "quick detach" connector to each of the positives
so that I could monitor the batteries separately. And perhaps just start
on one?

I have these on a couple of my "yard" vehicles because they seem to have
some discharge current when left connected.

http://www.ebay.co.uk/itm/Battery-Cl...AOSwo3pWenR l

On 13/12/2016 22:41, newshound wrote:

With this arrangement, isn't there a danger that if one battery
deteriorates (e.g. a cell shorting out) it will knacker the good one?

Yes. But if they're the same age and type you wouldn't worry about which
one had failed, you'd simply change both.

I wonder if the batteries are knackered anyway, or at least well past
their best. After all, a decent battery of the correct size should start
the engine without further help.

In the days of my youth a fellow student who had an Austin 1100 (I
think) was having starting problems. Clearly the battery was knackered.
As it happened I also had a knackered battery. I went to the motorists
discount and bought the cheapest one I could find (I think it was £7).
My friend wanted to try my old battery on his car. It was somewhat
better than his in that it would turn the engine over for a few seconds,
but it still wouldn't start the car. He then tried both batteries in
parallel, which of course didn't work. He then tried the batteries in
series. The starter motor turned quite well for a few seconds but then
stopped. All this in the students' car park when we should have been
attending a lecture. For some weeks he made sure to always park at the
top of an incline, but then one day he was distracted by a spider
lowering itself down from the car's ceiling, and he hit a wall. That was
the end of that. He lived but the car didn't.

The seven quid battery lasted less than a year, but I never got my money
back. I didn't bother trying.

Bill

Bill Wright wrote
newshound wrote

With this arrangement, isn't there a danger that if one battery
deteriorates (e.g. a cell shorting out) it will knacker the good one?

Yes. But if they're the same age and type you wouldn't worry about which
one had failed, you'd simply change both.

I wonder if the batteries are knackered anyway, or at least well past
their best. After all, a decent battery of the correct size should start
the engine without further help.

It isnt a car, it’s a piece of farm machinery that doesn’t get used a lot.

On 14/12/2016 04:57, Rod Speed wrote:
Bill Wright wrote
newshound wrote

With this arrangement, isn't there a danger that if one battery
deteriorates (e.g. a cell shorting out) it will knacker the good one?

Yes. But if they're the same age and type you wouldn't worry about
which one had failed, you'd simply change both.

I wonder if the batteries are knackered anyway, or at least well past
their best. After all, a decent battery of the correct size should
start the engine without further help.

It isnt a car, it’s a piece of farm machinery that doesn’t get used a lot.

Yes you said. It doesn't really matter. If it was designed to start on
one battery that should be all it needs. If one battery won't produce
enough current to turn the engine over fast enough then there's
something wrong. The battery, the cables, the starter, or the engine.

If it doesn't run for long enough to recharge the battery after starting
then yes, you'll need some auxiliary charging. The little solar chargers
aren't much use. The bigger ones are better. Unless the vehicle is in a
barn!

Leakage is also an issue, especially if the electrics are damp. I have
leakage on the motorhome of 0.001 to 0.002A in winter, which would be
significant if I didn't use the vehicle for several months.

Bill

"Bill Wright" wrote in message
news
On 14/12/2016 04:57, Rod Speed wrote:
Bill Wright wrote
newshound wrote

With this arrangement, isn't there a danger that if one battery
deteriorates (e.g. a cell shorting out) it will knacker the good one?

Yes. But if they're the same age and type you wouldn't worry about
which one had failed, you'd simply change both.

I wonder if the batteries are knackered anyway, or at least well past
their best. After all, a decent battery of the correct size should
start the engine without further help.

It isnt a car, it’s a piece of farm machinery that doesn’t get used a
lot.

Yes you said. It doesn't really matter.

Corse it does.

If it was designed to start on one battery that should be all it needs.

And if it never was designed to start on one battery, it wouldn't be.

If one battery won't produce enough current to turn the engine over fast
enough

You don’t know that is the problem.

then there's something wrong.

Not if was always designed to need two batterys in parallel to start it.

The battery, the cables, the starter, or the engine.

You don’t know that there is any fault at all.

If it doesn't run for long enough to recharge the battery after starting

That does appear to be the problem.

then yes, you'll need some auxiliary charging. The little solar chargers
aren't much use. The bigger ones are better. Unless the vehicle is in a
barn!

In which case it should be possible to plug it in in
the barn to allow it to be charged when in there.

Leakage is also an issue, especially if the electrics are damp. I have
leakage on the motorhome of 0.001 to 0.002A in winter, which would be
significant if I didn't use the vehicle for several months.

On Tuesday, December 13, 2016 at 6:14:13 PM UTC, jim wrote:
old tractor, 2 x 12v biggish batteries linked in parallel provide
the power to start.

Only used for fetching haylage once a week so batteries often
don't start it the next time....

Is it OK to just charge the pair of batteries by clipping on a
battery charger, without disconnecting the interconnecting
wiring?

Or is it necessary or advisable (and why please) to electrically
isolate each and charge one at a time?

For longer term would a solar trickle charger be worthwhile?



This is the typical situation in narrowboats, i.e. two or more batteries strapped in parallel and charged that way both by the alternator (when engine running) or by battery charger.

Take care with solar trickle charging over long periods. I have seen batteries wrecked by this. Once the batteries are charged the trickle goes on electrolysing the water (gassing) and eventually the plates get exposed and damaged.

Robert

On 14/12/2016 09:03, RobertL wrote:


Take care with solar trickle charging over long periods.

I have seen batteries wrecked by this. Once the batteries

are charged the trickle goes on electrolysing the water (gassing) and eventually the plates get exposed and damaged.

Yes, that's with a proper big solar panel. The little ones (about a foot
by 6") won't do that.

Bill

Personally I've found nothing but grief from car batteries in this mode.
Say one battery has a dodgy cell, the other battery then charges the duff
one until neither are very good.
If it were a low power use I'd say isolate them by diodes and charge one at
a time but in this case, either get a battery capable of starting the
vehicle on its own, make sure but batteries are switchable and keep both
charged and use them in rotation.


Incidentally this using cells in parallel goes even more so for other
rechargeable types.
Brian

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This newsgroup posting comes to you directly from...
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"jim" k wrote in message
o.uk...
old tractor, 2 x 12v biggish batteries linked in parallel provide
the power to start.

Only used for fetching haylage once a week so batteries often
don't start it the next time....

Is it OK to just charge the pair of batteries by clipping on a
battery charger, without disconnecting the interconnecting
wiring?

Or is it necessary or advisable (and why please) to electrically
isolate each and charge one at a time?

For longer term would a solar trickle charger be worthwhile?

TIA
--
Jim K


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

Brian Gaff has brought this to us :
If it were a low power use I'd say isolate them by diodes and charge one at a
time but in this case, either get a battery capable of starting the vehicle
on its own, make sure but batteries are switchable and keep both charged and
use them in rotation.

You cannot isolate batteries via diodes, because it would create a
difference of 0.7v due to the voltage lost across the diode. 0.7v is a
lot of difference in battery voltage terms, much more than the
difference between a fully charged and a flat battery.

In article , Harry Bloomfield
wrote:
Brian Gaff has brought this to us :
If it were a low power use I'd say isolate them by diodes and charge
one at a time but in this case, either get a battery capable of
starting the vehicle on its own, make sure but batteries are
switchable and keep both charged and use them in rotation.

You cannot isolate batteries via diodes, because it would create a
difference of 0.7v due to the voltage lost across the diode. 0.7v is a
lot of difference in battery voltage terms, much more than the
difference between a fully charged and a flat battery.


You certainly can isolate batteries via diodes. Lucas used to make a unit
-about the same size as an ignition coil specifially for this purpose. Our
tecnical survey vehicles used them in the 70's and '80s. After then, a
hefty relay, which closed when the alternator was producing enough volts
was used.

--
from KT24 in Surrey, England

charles laid this down on his screen :
You certainly can isolate batteries via diodes. Lucas used to make a unit
-about the same size as an ignition coil specifially for this purpose. Our
tecnical survey vehicles used them in the 70's and '80s. After then, a
hefty relay, which closed when the alternator was producing enough volts
was used.

Because they realised that diodes just did not and could not work?

The only way you can make diodes work effectively, is by increasing the
input voltage by 0.6 to 0.7 volts to take care of the forward voltage
lost across the junction.

In article ,
Harry Bloomfield wrote:
charles laid this down on his screen :
You certainly can isolate batteries via diodes. Lucas used to make a
unit -about the same size as an ignition coil specifially for this
purpose. Our tecnical survey vehicles used them in the 70's and '80s.
After then, a hefty relay, which closed when the alternator was
producing enough volts was used.

Because they realised that diodes just did not and could not work?

They did work - we used them for at least 15 years, running technical
equipment off the second battery.

The only way you can make diodes work effectively, is by increasing the
input voltage by 0.6 to 0.7 volts to take care of the forward voltage
lost across the junction.

the relay was better.

--
from KT24 in Surrey, England

Harry Bloomfield wrote:
The only way you can make diodes work effectively, is by increasing the
input voltage by 0.6 to 0.7 volts to take care of the forward voltage
lost across the junction.

Well it depends. If you don't need starting current you can get the forward
voltage down a fair bit:
http://uk.farnell.com/vishay/vs-80cp...247/dp/1013352

That would be acceptable to run equipment off without the 320mV forward
voltage being too bad. But obviously switching with relays would be more
efficient - you don't lose several watts in the diode. Use diodes to power
the relays.

If you need hundreds of amps then you are in the 600mV territory for voltage
drop.

Theo

On 14/12/2016 16:01, charles wrote:

You certainly can isolate batteries via diodes. Lucas used to make a unit
-about the same size as an ignition coil specifially for this purpose. Our
tecnical survey vehicles used them in the 70's and '80s. After then, a
hefty relay, which closed when the alternator was producing enough volts
was used.

You can isolate them, but the voltage drop greatly reduces the charge
rate, and it will taper to zero before the battery is anything like
fully charged.

Bill

On 14/12/2016 10:39, Brian Gaff wrote:
Personally I've found nothing but grief from car batteries in this mode.
Say one battery has a dodgy cell, the other battery then charges the duff
one until neither are very good.
If it were a low power use I'd say isolate them by diodes

Better to use relays.

Bill

Bill Wright formulated the question :
Better to use relays.

The ONLY effective method.