For the van I’m building I’ve made a DIY lithium battery from CALB cells and a bms like Will made. It’s 100 ah but I feel like I need a little more. I’ve found a 250 ah full river agm battery for cheap and I was thinking about wiring it in. Is that stupid? Would it actually work? Or would it mess with the bms in the lithium battery?
Adding AGM to a DIY Lithium CALB cell battery
- Thread starter ajbaseler
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Ampster
Renewable Energy Hobbyist
The discharge curves are entirely different. You will wear out your expensive Lithium battery as it tries to charge the AGM.
John Frum
Tell me your problems
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Ampster
Renewable Energy Hobbyist
The discharge curves with NMC and LFP are much more similar. I am not saying you cannot do it or that it is stupid. It will work but I can not predict what the eddy currents will have on the charge control of the BMS and whether it will work for very long. Buddy pairing CALBs will give you a more satisfactory solution.
HighTechLab
AKA Dexter - CTO of Current Connected, LLC
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I would try to avoid it. You really won't benefit very much.
With me mixing chemistries, adding the 2kwh NMC pack to my 4.5 KWH Calb pack only gave me 5.7KWH total capacity...So only a 1.2kwh increase but at the cost of 2kwh.
Below are some thoughts that aren't fully compiled, just a few things that come to mind. Think of it carefully and don't take it for fact, just speaking from my past experiences. I've ruined 3 palettes of FLA batteries so what do I know? :shurg:
With me mixing chemistries, adding the 2kwh NMC pack to my 4.5 KWH Calb pack only gave me 5.7KWH total capacity...So only a 1.2kwh increase but at the cost of 2kwh.
Below are some thoughts that aren't fully compiled, just a few things that come to mind. Think of it carefully and don't take it for fact, just speaking from my past experiences. I've ruined 3 palettes of FLA batteries so what do I know? :shurg:
A SERIOUS issue when I was using Flooded Lead Acid cells, they had a massive self discharge as they aged. It should work so long as you set your batteries to operate on the voltage setpoints of the CALB cells (The CALB has a much narrower voltage range, so setting it to the range of the AGM would ruin the CALB) but in time as the AGM ages (Which would be more rapid than the CALB) it could start to pull down the system to be less capacity compared to what you began with.
Additionally, the bulk of the capacity of the CALB cells is at a higher voltage. like in my case 52-53 volts with CALB, whereas with my old FLA batteries, resting full charge was 51.2v. Having a lead-based chemistry over their resting voltage typically means they are going to consume power (Essentially charging off of the CALB drawing them down faster) and burning that power to electrolysis in the cell (At least for FLA - I realize you are running AGM) and heat generation.
Additionally, the bulk of the capacity of the CALB cells is at a higher voltage. like in my case 52-53 volts with CALB, whereas with my old FLA batteries, resting full charge was 51.2v. Having a lead-based chemistry over their resting voltage typically means they are going to consume power (Essentially charging off of the CALB drawing them down faster) and burning that power to electrolysis in the cell (At least for FLA - I realize you are running AGM) and heat generation.
