Desulfating the Batteries
Last updated Monday March 26, 2012
Desulfating the Batteries
Equalizing:
Every battery is slightly different. One may re-charge faster than another. The strongest battery reaches full charge while the weaker ones doesn't quite get a full charge. After each discharge/charge cycle the weaker batteries get lower and lower until after several discharge/charge cycles, the weaker batteries are hardly charged at all. Equalizing brings all the batteries back the fully charged again.
De-sulfating:
A lead-acid battery that discharges for too long will start to build up sulfate crystals. De-sulfating is the process of breaking down these crystals. This is done with short burst of high amperage current applied to the battery.
I have been able to take a completely dead battery, put it on the capacitive charger and within a few minutes, bring life back into the dead battery. You can actually hear the crystals cracking and breaking down inside the battery.
Battery range can more than double after a good equalizing and de-sulfating process.
I normally re-charge my battery pack at 12-15 amps. Whenever I notice my batteries capacity isn't as good as it should be, I give them a deep charge at 30 amps, and let them equalize for a few hours after they are fully charged. This causes them to gas quite a bit but it is necessary to restore their full capacity. The next time I drive, they act like bran new batteries again. You don't want to do this very often simply because it uses a lot of electricity. In my case, it takes about 5-7KW-Hr (or $0.50 to $0.70 worth of electricity) to equalize and de-sulfact the pack.
I equalize and de-sulfate the batteries every 2-5 weeks. The batteries can lose a lot of water during a de-sulfating cycle. I add water to the batteries every 2 months or so.
I prefer flooded batteries to AGMs because they are way cheaper and you can add water back to them when needed.
If you accidentally leave a flooded battery on a high current charger, no problem. Just add more water. If you leave an AGM battery on a high current charger, you better start saving for a new battery.
More information about the battery charger and de-sulfating circuit that I use can be found here.
Someday, I will get Lithium batteries. In the mean time, plain old flooded, lead-acid batteries are working out just fine.
Update 7/14/2012:
After almost 9000 miles, the batteries in my EV truck have started to show signs of degradation. While I used to have a 56+ miles freeway range, most days I am lucky to get 32 miles. For the most part this isn't a problem because my commute is only 20 miles one way and in January 2012, my employer installed 2 dedicated stalls for EVs with an outlet near by.
Still, I am slightly concerned about my truck's range continuing to get worse.
I have also noticed an increase in power consumption in charging the batteries. It used to take 6 kWh to drive 20 miles it now takes 7.5 kWh.
My battery pack will perhaps last another year but in the mean time, I am researching out lithium ion battery packs. I calculate that a pack 1/2 the capacity of my current lead pack will provide nearly the same range simply because it is so much lighter and doesn't suffer from the Perkert effect as much. We'll see.
Such a battery pack will weigh 1/6th of my lead pack. This begs the question, "With such a light battery, what's the use of staying with a pickup truck anymore?" This opens up any vehicle to use as a long-range, freeway capable EV.