I finally managed to sort out the array of bulbs needed to drain the battery at a rate of C2. It seems to work fine and it is interesting to see how the voltage changes as they are drained.

One thing I still don't know is when to stop as I know that draining the batteries too deeply will cause damage them. I simply stopped when the voltage as they were being drained dropped to 11 volts per 12 volt battery which they reached very rapidly. How deeply do I discharge them how do I know that they have reached that point?

Is there anything else that may be helpful such as subjecting them to a heavy load?

Thanks

 

Looks like I may have screwed up. I am here to find out exactly what has gone wrong as I have 2 possibilities. This can be salvaged as I will learn from my mistakes.

The batteries have shown a large drop in capacity.

After putting the heavy load on the batteries as advised to lessen the likelihood of deformations of the lead plates I returned them to the desulfator. I was not feeling well at the time so I am unsure if I correctly recharged before doing so, they may have only had a partial recharge. I remember reading that it is important to fully charge them before desulfaton. Could this have caused the loss in capacity somehow? If so how?

Or did I drain them too heavily? I drained them at C2, 14ah on a 7ah battery, until the voltmeter read 11volts at the terminals of the batteries as I drained them. Within a few minutes of disconnecting the power drain the voltage jumped up to about 12.3 volts.

Thank you for any help you can offer.

 

Oh, gosh - I would not have discharged them so deeply.
I have had many things going on here, so have not had much time for the forums.
12v is as low as I would've gone, which is about 70% charged. If you discharge a battery heavily and deeply, you can cause damage due to heat.

You should always recharge them after the discharge, and be mindful of the battery internal temperature. It does not take long to heat them up, whether charging or discharging heavily - but takes the battery mass a comparatively long time to cool.

I have found that automotive battery plates tend to fail most often towards the center group of cells, which indicate to me that they were operating at a higher temperature than the cells more towards the outside.