Trojan lithium finally here!

[Mike90250]

Most charge controllers fault out around 8V, some may recover and auto reboot, others may just hang till manually rebooted.

The simple workaround is a DC switch connecting the PV to battery - activate the switch for 5 min to boost the battery directly from solar, till it can fire up the controller. Switch must be rated for DC & amps the PV can put out,

[PNjunction]

The better solution is to use a secondary LVD set higher than the bms' dead-man cell protector voltage so you don't go so far down into the discharge knee in the first place and confuse the charge-controller.

Why? For best long-term life / premature aging, when you fall well down into the knee it happens very fast. Likewise, one should come OUT of the steep discharge knee SLOWLY. Ie, some form of current limiting until you reach a terminal voltage of say 12.5v for example and then continue on normally. No controller I know of gets confused seeing 12.5v !

I watched early EV guys who did the bottom-balance thing take it to the dregs. And then in the garage, attach their monster charger at 0.5C just hammer those cells when they are sitting in the bottom of the knee. In some cases, after awhile those cells were practically bursting their case-straps, or if one was monitoring both current and voltage, could see that the cells were going nowhere, just spinning their wheels. Essentially a cage wrestling match of ions and electrons with nowhere to go when hammered in the knee.

I abused some small 26650's LFP's in a hobby charger to emulate this to watch the action. YUP! They don't like that, so reduce current when recharging coming from deep within the knee, and all is well.

So, with a secondary LVD set conservatively, if/when you hit that, then you can fire up the monster charger right off the bat.

Only one manufacturer does this, Optimate LFP chargers - designed for LFP motorcycle starter batts. (energy vs deep discharge power). Somehow they got the hint, and made me smile.

So like someone relying solely on a lead-acid inverter dead-man setting of 10.7v, you don't hammer those either when they are totally discharged - you should come out slowly before hitting the gas pedal with the charger.