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Floodie / Lithium hybrid battery experiment

40178 Views 93 Replies 16 Participants Last post by  dougingraham
I'm starting an experiment to test the effects of using lithium LiFePO4 cells in parallel with cheapo lead acid batteries.

Lithiums are 40 AH Calbs, and they'll be boosting 29HMs (formerly known as 29DC) and GC8s. My current frankenpack consists of 3 29HMs and 11 GC8s.

Phase 1 of FLHE will put 8 calbs in parallel with 2 29HMs with a JLD404 to monitor AH usage and control charging. The calbs will be charged in parallel with the floodies until approx entering gassing phase where the JLD will cut the lithium contactor while the floodies finish their cycle. 1 29HM will remain unboosted as a control.

Phase 2 will add 8 calbs in parallel with 3 GC8s and tested as above.

The experiment will try to gain info about how the current sharing works out as well as how lead cycle life can be prolonged with the aid of a lithium booster.

A successful experiment would demonstrate an increase in lead cycle life sufficient to justify the cost of the lithium booster.


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You can parallel Lead Acid and you can Parallel Lithium but I would not mix chemistries in series or parallel.
Parallel works fine but you have to know what you are doing.

I wouldn't consider this as a solution for anything because you still have lead acid batteries in your car and you still have all of their disadvantages, namely the low energy density and high weight. The only thing people see with LA is the illusion of saving money.
You could line your boxes with that maybe. I would be worried about the temp differential between the warm side and cold side of the batteries though. Maybe use spacing to get convection in there too?
Probably you don't need to worry about differences across a cell. If you think about it these batteries are a stack of copper and aluminum foils with a thin electrical insulator saturated with electrolyte between them. The case might be different temps from one side to the other but there won't be much difference from one side of the internals to the other for very long.

It gets very cold here on occasion (I have seen -40 a couple of times in the last 38 years). I insulated my battery boxes (A little better than R3) and if it proves to be a problem I will put a heat plate under the cells. I expect a few jackrabbit starts will warm them up enough though. Heating this last summer was not an issue. The most I saw was about 10 degrees above ambient and with the cells in the insulated box they stayed cooler than the inside of the car when it was sitting in the sun. What I am trying to say is that the battery temps vary less than the outside air temp.
yeah a discharge at a rate of 5ah/aka amp hour . ....I found 6 volt golf cart battery 200ah on a local basis and also thinking they may withstand my application not that the AGM would not but both closely price but the purchase of 6 volt deep cycle golf less footwork
At 5 amp discharge rate both cells will give you the full 200 ah as this would be a 40 hour rate. The real problem is that once you get below about 50% state of charge the plates start sulfating at an accelerated rate so while your battery will do this once it will be hurt by doing so. I don't know which of the cell types you mention would survive this better. Some of the Lead Acid batteries would do this only a handful of times and they would be completely ruined.

If you only discharge to half (about 20 hours) either type should last a couple of years.
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