Lead acid battery desulfonation

Been using my 12V battery minder desulfonator on my 24V series SLA battery pack.

12 V SLA batteries wouldn't charge up indiviually on the 12 V individual batteries, but when I put the Battery minder accross the 24V series pack, the battery minder started it's desulfonation pulsing. When the desolfonater is remove, the SLA batteries are at 14V total rather than their prefferred 24V, so not sure if the experiment is progressing yet.

Does a SLA battery with sulfonated plates appear as merely a high internal resistance battery, or will a cell appear shorted or open?

meb wrote:
> Been using my 12V battery minder desulfonator on my 24V series SLA
> battery pack.
>
> 12 V SLA batteries wouldn't charge up indiviually on the 12 V
> individual batteries, but when I put the Battery minder accross the 24V
> series pack, the battery minder started it's desulfonation pulsing. When
> the desolfonater is remove, the SLA batteries are at 14V total rather
> than their prefferred 24V, so not sure if the experiment is progressing
> yet.

Uh-oh.

It sounds like your battery conditioner is intended for 12V, and
wrecked your pack. Anything less than about 21V on a 24V pack, even
for a short time, usually means it's time for a new battery.

I suggest hooking your batteries up in parallel, instead of in series,
to the same battery conditioner. You haven't got much to lose at this
point. Might as well see if they can be saved.

Chalo Colina

This 4 year old pack Twas already wrecked before I tried conditioning accross the 24V, so that is why I tried saving it by running the 12V conditioner accross the 24V serries terminals. The other 4 year old 24 V pack still is fine.

I usually run the conditioner accross the 12V SLA batteries separately, but when that failed and noticed the sum voltage was just under 12V instead of 24-26V, I though lets try this.

I've seen the two 12V batterries in the pack rise from 5.7-5.5V each to about 6.5 V, so there is some encouraging improvement.

The 12V and 24V chargers are sending out 1 A, but never reached a charged state. I wouldn't expect to see an intermediate voltage like I have if I have an internal cell open, but might if I have an internal shorted cell or if resistance was ultra high due to sulfur deposits, so was wondering if anyone knew the fail mode?

If it is merely an ultra high internal battery resistance, I would expect to be able to recover the batteries with the conditioner accross the serries combination.

If shorted, perhaps a solution would be to place the conditioner accross the separate 12 V batteries with a 10 ohm power resister in serries between the battery and conditioner.





However, the low voltage

On Fri, 15 Jul 2005 17:36:42 +1000 meb
<meb.1s7ba5@no-mx.forums.cyclingforums.com> wrote:

>Been using my 12V battery minder desulfonator on my 24V series SLA
>battery pack.
>
>12 V SLA batteries wouldn't charge up indiviually on the 12 V
>individual batteries, but when I put the Battery minder accross the 24V
>series pack, the battery minder started it's desulfonation pulsing. When
>the desolfonater is remove, the SLA batteries are at 14V total rather
>than their prefferred 24V, so not sure if the experiment is progressing
>yet.
>
>Does a SLA battery with sulfonated plates appear as merely a high
>internal resistance battery, or will a cell appear shorted or open?

From your description, it's really quite hard figuring out what you've
actually done, but I THINK that you've put 2 12V packs in series and
then put them across a 12 V charger because they measured about 12V
total when in series.

The short answer is that if a lead acid battery measures significantly
less than 2V per cell, then it probably has shorted cells. The only
cure for shorted cells is replacement.

Sulfated cells are different. They will show a high cell voltage with
a small charging current. If you charge them VERY slowly, they are
often recoverable. An appropriate charging current would be about 0.1%
of it's amp-hour rating. Expect this to take a week or 2 to work, if
it is going to work at all. Trying to recover a sulfated cell faster
by charging it faster only reduces your chances of success.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

A shorted cell is what I was expecting and your description confirms that. I finally went back to charging 12V across 12 V and the voltage after 12 hours never came up over 6.5V so it appears as if there is a shorting problem rather than sulfation. I assume there are 6 2V cells per SLA battery, so it appears I have 3 shorted cells per in each battery.

The BatteryMinder desulfator I have won't commence its desulfation pulsing till the voltage comes up, so I was only able to perform desulfation when the two batteries were series. If the low persisten voltage could have been a sulfation sympton, I might have tricked the BatteryMinder into thinking I had a fully charged battery by placing a resistor in series with the circuit.

Thanks for the confirmation, the batteries were almost 4 years old anyway. I'll generally convert my SLA packs to NiMH as they need replacement.

On Mon, 18 Jul 2005 14:35:18 +1000 meb
<meb.1sclu6@no-mx.forums.cyclingforums.com> wrote:

>A shorted cell is what I was expecting and your description confirms
>that. I finally went back to charging 12V across 12 V and the voltage
>after 12 hours never came up over 6.5V so it appears as if there is a
>shorting problem rather than sulfation. I assume there are 6 2V cells
>per SLA battery, so it appears I have 3 shorted cells per in each
>battery.

Is there any way to replace individual cells in this battery? This can
be done in some SLA assemblies. They are often made up of Gates Cyclon
SLA cells.

NiMH cells will have significantly lower voltage per cell (~1.5V
rather than 2.2V), so they won't make good replacements here.
-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

I wouldn't think individual cell replacement is feasible as the batteries are smooth boxes with terminals.

As for the NiMH, you just use more cells.