flooded lead acid batteries y charging voltage question

[DBA Forum (B) - Tim Hackett]

I have been rereading my battery charger manual (Victron Centaur). My battery bank is 600 a/hr made up of series/parallel Rolls 200a/hr deep cycle flooded cells.

I have the charger set to LA which gives absorption at 28.8volts according to the manual, but now I look again there is an "other" setting which is aimed at more specialist LA cells and this absorbs at 29.7volts which I think would be better for the Rolls batts. Their fact sheet suggests 30 v at temps up to 17 deg C but 28.9 v above that.

Anyone any thoughts? Rolls batts are very robust so I figure the higher setting won't hurt them but I will need to watch the water loss rate (negligible so far this year)

Cheers

Tim

[DBA Forum (B) - David Beaumont]

I would think there are only two reasons to put in a higher voltage 1) to fast charge a battery or 2) to try to de-sulphate one. Otherwise it's best to charge them gently. Anything above around 26V is a charge. If you want to be really kind here is the chart for a Victron Gel battery I made showing charge rates against temperature for a 12V battery. Just double the voltage figures . Admittedly a gel battery is the most sensitive to over volts but using these figures won't harm any lead acid battery.


[attachment=210]Image1_2014-08-19.jpg[/attachment]

David

[DBA Forum (B) - Chris Green]

I would think there are only two reasons to put in a higher voltage 1)
to fast charge a battery or 2) to try to de-sulphate one. Otherwise it's
best to charge them gently. Anything above around 26V is a charge. If you
want to be really kind here is the chart for a Victron Gel battery I made
showing charge rates against temperature for a 12V battery. Just double
the voltage figures . Admittedly a gel battery is the most sensitive to
over volts but using these figures won't harm any lead acid battery.

Yes. As I understand it the reduced 'maximum' voltages for sealed and
gel batteries are simply to minimise the risk of overcharging, the
chemistry is fundamentally the same as for a wet battery.
Overcharging a wet/flooded cell battery does little harm except to
make it gas and lose water so as long as it's topped up no harm is
done. Overcharging any sort of sealed battery loses water which cannot
be replaced so damages the battery.

(OK, I think there are some chemical differences in sealed batteries,
e.g. they use Calcium, but this can be in flooded-cell batteries too)

[DBA Forum (B) - Daniel Boekel]

I know 'forklift' 2v traction cells need to be charged regularly to 30 volts (24v bank) to stir the acid so the heavy part doesn't stay at the bottom.
So they need gassing to stir... don't know about the rolls batteries

I would think there are only two reasons to put in a higher voltage 1)
to fast charge a battery or 2) to try to de-sulphate one. Otherwise it's
best to charge them gently. Anything above around 26V is a charge. If you
want to be really kind here is the chart for a Victron Gel battery I made
showing charge rates against temperature for a 12V battery. Just double
the voltage figures . Admittedly a gel battery is the most sensitive to
over volts but using these figures won't harm any lead acid battery.

Yes.  As I understand it the reduced 'maximum' voltages for sealed and

gel batteries are simply to minimise the risk of overcharging, the

chemistry is fundamentally the same as for a wet battery.

Overcharging a wet/flooded cell battery does little harm except to

make it gas and lose water so as long as it's topped up no harm is

done. Overcharging any sort of sealed battery loses water which cannot

be replaced so damages the battery.



(OK, I think there are some chemical differences in sealed batteries,

e.g. they use Calcium, but this can be in flooded-cell batteries too)



--

Chris Green

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