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Andy,

Sounds like you have made a career in offgrid power, something I have only dabbled with.? The earthship must have been a major project and a big learning experience, I was looking hard at that before going with strawbale infill on our post-and-beam house, has a Faswall basement and is positioned for passive solar.? Had 2.2 kW of PV till a couple years ago, now at 4.4 kW and will probably double that soon so we can get through dark NE Oregon December weeks without running a generator.? Most winter heat is currently from windfall ponderosa pine, as I get older and less inclined to swing a chainsaw we may pivot to a large well insulated hot water reservoir in the basement heated by excess PV on occasional sunny winter days to keep the hydronic floors warm in bad weather.? Wind and micro-hydro are vague possibilities here, but enough PV for cloudy weather at $0.50 per Watt is hard to beat.
When we first bought, got by with a 20 foot yurt and 45W worth of PV from Harbor Freight and a couple used golf cart batteries.? Most of that power went to a Sundanzer DCR225 fridge, cooling it off during the day and coasting through the night.? Have power lines to the property, but was quoted $15k to get power to our building site if I dug the ditch.? Was happy to hear that, as I was inclined to go offgrid anyway (we all need hobbies!).? With 4.4 kW of PV and 29 kWh of LiFePO4, we pretty much never use the generator and my partner Liz need not think about my hobby when using the 26 cuft front loading fridge/freezer, 3 chest freezers, and dishwasher with superheater.? I've given up complaining when and empty rooms are left with the very efficient LED lights left on.? Being remote, power to the area occasionally goes out, and I rather enjoy telling the neighbors "no" when they ask if our power went out too.?

The JBD 200A BMS has a rather wimpy passive balancing scheme, discharging any cells with excessive voltage at maybe 250mA.? This is proving adequate for the 2P16S pack of relatively well behaved LF280K cells from Docan, though I found it necessary to disable balancing at anything under about 3.41 Volts as the charge curve for the various cells differed enough below that value that the wrong cells were getting discharged.? I'd guess this is because any cells with tighter specs were cherry picked for use in EV's.

A minor nit of which I am sure you are aware, but seems worth pointing out to the forum:
>? "While the operational voltage per cell can vary between about 2.4 and 3.8, the family still has a max of 4.2 and a minimum of about 2V per cell."
The LiFePO4 cells should never be charged much above 3.6 Volts, they would definitely be damaged if held at at 4.2 Volts.? Pretty much all the other Lithium Ion chemisties are good to around 4.1 or 4.2 Volts as stated.?

I charge my battery to a max of 54.8 Volts (3.425 Volts per cell) and shut things down when it falls below 48.0 Volts (3.0 Volts per cell).? This is using my Magnum PT100 charger, which was designed for lead acid and so is not aware of individual cell voltages.? That range gives me something close to 99% of the available capacity and allows fast charging when only occasional sun is available, but avoids extreme highs and lows where top balancing (at the high end) and matched capacities (at the low end) become critical.? As these cells diverge with age, I may need to program those high and low voltages to something more conservative.? Ideally, I would instead figure out how to tell the PT100 to stop charging (without the possible voltage transients of letting the BMS take care of this) when any single cell exceeds 3.6 Volts.? Letting the BMS relay cut out the battery when any single cell falls below 2.5 Volts is probably just fine.

Looking forward to having an electric vehicle, especially if it can be cabled up to the house during a week of foul weather to make good use of that 70 kWh battery.? ?Will check out Endless Sphere.? When a difficult technical issue is raised on diysolar there can be ten different answers, and I might find eight of them to be misinformed.

Jerry, KE7ER