1500x Sudden battery drain when at 50%(ish)


I don’t need an answer fast but something odd happened with my 3 year old yeti 1500x.

It is set to the battery saver mode and stays plugged in on the 120w charger it came with.

It gets used approx once a month when the power goes out for a few hours and powers the modem/wifi and a phone or two. I can’t recall it ever dropping below 70% charge.

Cue our current storm in Houston, I had it plugged into our fridge freezer which was drawing 140w and into the 200w solar panel that was producing almost nothing as it was cloudy.
All was going well until it got to what must have been around 50% life maybe a little lower not exactly sure but I checked on it and power level was zero whr and no output.

I took it over to my BiL who had power and got it up to 40% with the 120w charger (I will never need the 600w charger I said 3 years ago)

Tested the draw with a toaster and all seemed well reported battery life in expectations with 700w draw. Took it back home ( via purchase of 1000w inverter for the car) and have had it back up to 70% and then running off solar and keeping the fridge going so all seems ok now.

Anyway, any thoughts on why it would have gone from 50% ish to nothing?
a feature of never having run it down all the way for a while ?
are there multiple banks in it or is it pulling off all the cells in there ?
firmware is 1.8.0 will update when we get internet back as I can’t seem to update using phone cellular data.



  • jg164
    jg164 Administrator, Moderator Posts: 313 admin


    There is a single pack inside but multiple lithium cells it needs to balance with the BMS

    My guess is the yeti got a little zap from some distant lightning that tricked the bms into rebooting. If the bus gets a fault, the screen will show 0% and often a Battery icon with an exclamation point inside. I would leave solar disconnected if there is a storm near by.

    If that is not the root cause, try charging it to full and draining with a space heater or heat gun full to empty about 5 times. The bms may need time to level the cell voltages. If you still get 50% SoC drops, might be a bad cell in the pack.