Solar charging lifepo4

Morning chaps,

I'm looking for a more efficient way of charging my 9Ah E-bike battery from my solar shed.

Currently I have a 180W panel charging a 110A lead acid battery in the day that in turn powers a Victron 1200W sine wave inverter powering the battery charger at 230V. This system works well enough but the efficiency is pants, I’ve estimated about 60% which is ok in the summer but is likely to give issues in the winter. Charging my battery after my homeward commute takes 3 hours at 2A (at least that’s what the charger says its rated at). It’s also something of a pain to trog out to the shed 9.00 every night to unplug the charger and refit the battery to the bike.

My plan is to use one of these fellas,



They are the holy grail of boost converters, they accept an input voltage of between 9 and 60V and output anything from 0 – 60V at up to 40A, they even work in constant current mode!! I’ve have some awesome 100A power supplies with these in the past, several can be parralled together to increase current.

I have built many a lead acid charger but these lithium chaps are quite new to me. Am I correct in thinking that I just need to provide the battery pack with a regulated 43.2V at less than 1C ( probably 2A) and let the BMS do its thing inside the battery pack, This would be a boon in both efficiency (95% at full load) and I could leave the charger connected all night as long as I disconnect the motor controller? Or maybe keep the battery outside the shed or in a flame proof box while charging unatteneded.
Also it means I can leave the mains charger at work ready for the charge after the morning commute (about 2 hour charge).

I am planning a much bigger battery pack soon using 12 or 15Ah headway cells.

I am also planning on using one of these boost converters to run a second motor on the e-bike at something higher than 36V as kind of an overdrive.

Any thoughts greatly appreciated.

Sounds like it ought to work. The panel can't put out more than the battery can take, except when it's fully charged. Only 180w max, so not too many amps.

My first inclination would be to start out by charging it to 90% first, by setting too low a voltage on the converter. My main concern would be at the end of charge, the panel would keep on pumping 2 amps if still full daylight, which the bms would then try to get rid of. Eventually wearing out the bms early. Undercharging will keep the bms turned off, unless one cell is very high relative to the others.

Though it will be a PITA, ideally you'd finish the charge on your regular charger. Then it will shut off when it should. That last 10% and the balancing won't suck too much power, even if you do it on main AC. If it won't affect your range too bad, maybe just do that top off and balance once a week or so.

Play with it, while watching the cells voltage, and find out what total pack voltage you can charge to, without having every channel of the bms turned on and discharging. You might get 97% charged, without overusing the bms.

your BMS is not likely to interfere with the charging.if it gets to full charge then you will have the HVC cut off charging until the high cell drains down but that is not usually the case unless you have a battery that is far outa balance and if you use it and charge it regularly to full charge then it should be in good balance and charge fully under the BMS.

so take the power directly from the top of your lead acid array to run the inverter and maintain the current configuration of using the panels to charge your storage pod.

I made a charging setup a while back. Linking 400W setup charging a motor cycle battery, for a test. Ran the battery with charge controller to power an inverter. Worked a treat.

Do all bms have an HVC these days? I thought some relied on a charger shutoff. Much of what I know I learned here, and it's wrong.