[travelite]

Hi Richard,

Thanks for the write-up. It's great to hear some real world Li-Ion experience in a motorhome application. I think you nailed it. We motorhome user's by nature discharge our battery banks at fractional C-rates which makes a lot of things easier. Simple things like fuel-gauges work better if we don't have to correct for variable and extreme discharge rates. I like what you're doing with using your batteries in the middle 80% of their range. Given the replacement cost of Li-Ion's,  I'd probably go a step further and treat them much like we treat our AGM's; that is, limit the DOD to even less. Here's a paper that talks about LFP battery degradation when they're used in a more extreme manner:

LiFePO4 Cycling Degradation Battery.pdf Size: 1.38 MB  Downloads: 7

My next battery bank will be Li-Ion, but I have a split 24/12V system which needs to be provided for. My house is separate from the chassis and is composed of a 24V AGM bank, two 24V Trace SW4024 Inverters, and a Vanner Equalizer which converts the 24V to 12V for house use. My house has 120VAC, 24VDC, and 12VDC loads. The 12V loads are circuit breaker protected at 100A. What I need is a good quality 24V to 12V DC to DC Converter rated for over 100A, preferably 150A plus since efficiency can taper off when used at peak capacity. Of course not all loads will be on at the same time, but as you know you can approach a good DC draw with the Aquahot, nightime lighting, fans, and such running. Volta sells a rebranded Sensata converter that I haven't seen the specs for but the price is around $3500.  

Do you actually use your bank in the "middle 80%" range or do you use the top 80%. IOW's, do you stop charging based on the quantity of charge put back into the batteries using your fuel gauge? I also noticed that this type of middle band DOD prolongs life.