Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

Bill

On Tue, 13 May 2014 04:54:43 +0100, Bill Wright wrote:

Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

Chuck 'em both on the same 12v smart charger until they reach "float"?

On 13/05/2014 08:32, Adrian wrote:
On Tue, 13 May 2014 04:54:43 +0100, Bill Wright wrote:

Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

Chuck 'em both on the same 12v smart charger until they reach "float"?

But not at the same time.

On Tue, 13 May 2014 04:54:43 +0100, Bill Wright wrote:

Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

How are you going to be charging them, series @ 24 V or
parallel/individually @ 12 V? Even if you start with exactly the same
charge in both it won't be long before one has more (or less)
capacity than the other. Series charging is likely to make things
worse.

Making sure that you never discharge below about 1.1 V/cell(*) will
help maintain balance but they won't stay in balance.

(*) Memory, have a google for the battery makes specs, you might be
able go down to 1 V/cell.

--
Cheers
Dave.

They will never be matched in any case as obviously they are themselves made
of cells in series and each one will have slightly different capacity. When
any cell goes down, it is reverse charged by the current flowing through the
load and the impedance rises as the voltage drops, so to speak. I used to
use these batteries in models and really all one could do was try to catch
the voltage dropping below the norm and then recharge them both.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Adrian" wrote in message
...
On Tue, 13 May 2014 04:54:43 +0100, Bill Wright wrote:

Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

Chuck 'em both on the same 12v smart charger until they reach "float"?

In article o.uk, Dave
Liquorice scribeth thus
On Tue, 13 May 2014 04:54:43 +0100, Bill Wright wrote:

Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

How are you going to be charging them, series @ 24 V or
parallel/individually @ 12 V? Even if you start with exactly the same
charge in both it won't be long before one has more (or less)
capacity than the other. Series charging is likely to make things
worse.

Making sure that you never discharge below about 1.1 V/cell(*) will
help maintain balance but they won't stay in balance.

(*) Memory, have a google for the battery makes specs, you might be
able go down to 1 V/cell.


Interesting..

Over time I've been to transmitter and comms sites were they sometimes
have stack's of 2 volt cells around 500 odd amp hours each, but they
are just strung together to make 24 or 48 volts, so are they likely or
do they get one cell go "astray" and if so what can be done about it?..


*Astray meaning go wrong capacity wise in some way or 't other;!..

--
Tony Sayer

In article ,
Bill Wright wrote:
Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

I don't think it matters. Just start off with them both fully charged in
the normal way. After all, each one is cells in series, so you're just
adding more. And no two cells will be *absolutely* identical.

--
*Friends help you move. Real friends help you move bodies.

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

"tony sayer" wrote in message
...
In article o.uk, Dave
Liquorice scribeth thus
On Tue, 13 May 2014 04:54:43 +0100, Bill Wright wrote:

Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

How are you going to be charging them, series @ 24 V or
parallel/individually @ 12 V? Even if you start with exactly the same
charge in both it won't be long before one has more (or less)
capacity than the other. Series charging is likely to make things
worse.

Making sure that you never discharge below about 1.1 V/cell(*) will
help maintain balance but they won't stay in balance.

(*) Memory, have a google for the battery makes specs, you might be
able go down to 1 V/cell.


Interesting..

Over time I've been to transmitter and comms sites were they sometimes
have stack's of 2 volt cells around 500 odd amp hours each, but they
are just strung together to make 24 or 48 volts, so are they likely or
do they get one cell go "astray" and if so what can be done about it?..


*Astray meaning go wrong capacity wise in some way or 't other;!..

You do a periodical balance charge, which holds the batteries at a higher
than normal voltage for a time,
my motorhomes charger used to do this every 35 normal charging cycles, it
would take the battery bank* up to 15 and a bit volts for an hour or so,
causing them to gas vigorousely, part of the battery maintinence was to top
up the cells with distilled water every now and then, i didnt go as far as
adding the auto pumped watering system tho, as i found a check every 3
months was adequate,

*6 x 232 Ah 6 volt batteries in paralell and series to give me a 12volt 696
Ah battery bank.

BUT, that was for flooded vented cells, not sure what the equalizing voltage
for gell cells is, if there even is one,
As they are likely to be used in a granny chariot i guess, just charge them
both up to full on a 12 volt automatic charger, then connect them together
for your 24 volt bank, and charge as one battery from then on.... as that's
what the charger will see it as.... and it is just 12 x 2.2 volt cells in
series.

On 13/05/2014 08:38, newshound wrote:
On 13/05/2014 08:32, Adrian wrote:
On Tue, 13 May 2014 04:54:43 +0100, Bill Wright wrote:

Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

Chuck 'em both on the same 12v smart charger until they reach "float"?

But not at the same time.

Why not? Just parallel them up for 12V.

In article ,
newshound writes:
On 13/05/2014 08:32, Adrian wrote:
On Tue, 13 May 2014 04:54:43 +0100, Bill Wright wrote:

Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

Chuck 'em both on the same 12v smart charger until they reach "float"?

But not at the same time.

For float (up to 13.8V), they will be fine together in parallel,
as you can leave lead acid batteries on that forever. (Ideal float
voltage varies a bit with the precise battery type.)

For cyclic charge (= 14V), then charging together is not so good
as one may be gassing for a while as the other is still charging.
As a one-off, it probably won't matter, but you wouldn't want to
do it regularly. It is done (in both series and parallel) where
they are identical, same age, and replaced together at end-of-life,
but then the life you get is that of the shortest lived.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 13/05/2014 04:54, Bill Wright wrote:
Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?


Personally I would have got identical batteries as different makes will
likely have different characteristics.

Given the starting state may be different for each battery I would place
them in parallel and charge with a charger designed for gel batteries
that hopefully has a tight charging spec.

Is this for an alarm or similar, where the batteries will be
continuously float charge in situ?

Bill Wright wrote:
Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

Bill

Just stick them in series and charge them the same as a 24v battery.
My truck had that and did just fine.

Bill Wright brought next idea :
Given two 12V lead acid gell batteries, both new, both the same type, but
from different sources, how do I balance the charge before fitting them in a
24V appliance?

Bill

Charge each individually using some sort of controlled charger, to
bring each to a full charge after which they should balance.

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

Fredxxx wrote:
On 13/05/2014 04:54, Bill Wright wrote:
Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?


Personally I would have got identical batteries

They are identical, but bought from different places on the same day!

Bill

On Tue, 13 May 2014 10:32:11 +0100, tony sayer wrote:

How are you going to be charging them, series @ 24 V or
parallel/individually @ 12 V? Even if you start with exactly the
same
charge in both it won't be long before one has more (or less)
capacity than the other. Series charging is likely to make things
worse.

Making sure that you never discharge below about 1.1 V/cell(*)
will
help maintain balance but they won't stay in balance.

(*) Memory, have a google for the battery makes specs, you might
be
able go down to 1 V/cell.

Interesting..

Over time I've been to transmitter and comms sites were they sometimes
have stack's of 2 volt cells around 500 odd amp hours each, but they
are just strung together to make 24 or 48 volts, so are they likely or
do they get one cell go "astray" and if so what can be done about it?..

I doubt they are 500 AHr SLA cells, much more likely to be open
vented wet cells. I'd expect those to have routine maintenace of
checking the electrolyte density (aka the acid concentration) and
topping up as required. An open vented cell can be maintained, an SLA
can't be by it's sealed nature. This makes open vented cells are also
far more "robust" than SLAs.

--
Cheers
Dave.

Well if they have gone to the trouble of making them individually, one is
forced to the conclusion that they change out the duff cells.

Certainly in the model scenario mentioned earlier, the ideal would have been
individual cells as the cells in the pack always had at least one that went
down first.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"tony sayer" wrote in message
...
In article o.uk, Dave
Liquorice scribeth thus
On Tue, 13 May 2014 04:54:43 +0100, Bill Wright wrote:

Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

How are you going to be charging them, series @ 24 V or
parallel/individually @ 12 V? Even if you start with exactly the same
charge in both it won't be long before one has more (or less)
capacity than the other. Series charging is likely to make things
worse.

Making sure that you never discharge below about 1.1 V/cell(*) will
help maintain balance but they won't stay in balance.

(*) Memory, have a google for the battery makes specs, you might be
able go down to 1 V/cell.


Interesting..

Over time I've been to transmitter and comms sites were they sometimes
have stack's of 2 volt cells around 500 odd amp hours each, but they
are just strung together to make 24 or 48 volts, so are they likely or
do they get one cell go "astray" and if so what can be done about it?..


*Astray meaning go wrong capacity wise in some way or 't other;!..

--
Tony Sayer

It won't matter the effects everyone has noted p will still occur I'm
afraid.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Bill Wright" wrote in message
...
Fredxxx wrote:
On 13/05/2014 04:54, Bill Wright wrote:
Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?


Personally I would have got identical batteries

They are identical, but bought from different places on the same day!

Bill

On Wednesday, May 14, 2014 8:41:54 AM UTC+1, Dave Liquorice wrote:

I doubt they are 500 AHr SLA cells, much more likely to be open
vented wet cells. I'd expect those to have routine maintenace of
checking the electrolyte density (aka the acid concentration) and
topping up as required. An open vented cell can be maintained, an SLA
can't be by it's sealed nature. This makes open vented cells are also
far more "robust" than SLAs.

SLAs arent hard to open and add electrolyte - theyre not sealed despite the name - but the electrolyte pool is very small compared to flooded cells, so electrolyte issues happen much faster.


NT

On 13/05/2014 04:54, Bill Wright wrote:
Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

Bill


a 4 stage charger that includes balancing charge for Gel batteries will
take care of it for you .. CTEK make one



--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/