Finally! After a few rounds with the maker of the inexpensive $37 desulfator kit I finally have two working 12V lead acid battery desulfators. My neighborhood electric vehicle has two batteries which are performing badly. At the moment I'm testing one battery which was working great two weeks ago and now has a voltage of 10.6V. I found that two cells have a specific gravity of zero. I will retest the specific gravity in each cell tomorrow and see if there is any change. This battery should be able to entirely desulfate itself within 10 days. Hopefully I will be able to repair lots and lots of batteries with these desulfators.
3 comments:
Have you seen the suggestions listed here:
http://www.buchmann.ca/Chap10-page5.asp
I've seen desulfators similar to your blog post frequently mentioned as a cure for negative plate sulfation, but I have not seen any quantitative evidence that compares it to the simpler 2.5V/cell overvoltage that is also prescribed. Have you done any comparisons? Corrosion on the positive plate (as far as I know) is not reversible.
Regarding your maintenance headaches with electrolyte depletion, have you considered that you may be overcharging the batteries? The charger you have may be assuming high end batteries an thus subsequently causing premature electrolyte depletion in the second hand batteries that you acquired.
Interesting article. Thanks for sharing it.
The article focuses on two types of batteries.
SLA - Sealed Lead Acid
VRLA - Valve Regulated Lead Acid
These two types of batteries are significantly more expensive and much less common in my world. Generally I can only locate flooded deep cycle lead acid batteries.
I believe the 2.5V over voltage charging. Plus the charge on a charge recommended article is a good idea for flooded lead acid batteries. That is the same technique I use in combination with desulfation. Charge a battery overnight, let it rest during the day and charge it again the next day. All the while leaving a desulfator hooked up. I like having a small load on the battery to give it a little exercise and the desulfator is good for .5W.
I am definitely pushing my lead acid batteries. My PV solar battery array is being equalized at least once every 10 days. I let the system sit at 59.2V for two hours during equalization. Since I have eight 6V flooded lead acid batteries in series that means a charge voltage of 2.46V per cell. I believe this is just a good practice to avoid series sulfation. The bubbling should help reduce plate corrosion on both sides.
Sadly quality data proving that my practices are effective is not available at this time. I will try and put some load testing data together this year to see if my reconditioning efforts are effective.
Thanks for sharing your battery maintenance program.
I'm not very familiar with the charge controllers available for photovoltaic installations. When I looked a few years ago it seemed the ones with data logging capabilities quickly rose in price - not sure what they are at today.
I have been considering an open source charge controller recently, not just for lead acid, but any chemistry based on profiles set by the user. I'd like it to be modular so different users can tailor the system to their needs. I was envisioning an AVR (or other microcontroller e.g. ARM or Propeller) based master module that interacted with several other slave modules - an optionally untethered from a PC e.g. with an SD card. Slave modules might be: a temperature module, a FET based constant voltage/current module (available in different power configurations), possibly a desulfator, a power resistor discharge module, an for more involved experimentation- RFID or barcode module to catalog different cell packs an chemistries a user might have, an a pressure module using one of the freescale sensors for measuring gas evolution, etc.. The gathered data could then be communicated back to an open database an allow comparison of different chemistries an manufacturers. This is likely more than one needs for a lead acid charge controller, but just a summary of the direction I would like to go. There are many different user groups that such a system might benefit outside of home power. Anyway, wasn't sure if you had thought along a similar vector.
I'm not very knowledgeable, but have discovered that different manufacturer's cells within the same chemistry class can differ considerably based on many factors, alloys (e.g. lead with calcium an other agents), geometries, etc. It can be difficult to get one's arms around, but an open repository of data seems to be the right step forward.
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