looking for high voltage shut-off for solar charge

Hi electrical experts. I have a harbor freight tools 100w solar unit. This system consists of 4 x 12v panels hooked up in parallel. It also comes with a 12v charge controller, which I used until my lead acid could no longer hold a charge over night. Lately, I have been charging my 30ah battery (15s) with the panels in series. It gets my battery about 1/2 charged so I usually charge for a few hours at the end of the day after having it on the charger for 90 minutes in my classroom.

Here in my battery charging, the no load voltage, and at the end of the day:











My plan is to purchase another HFT 100w solar charging unit ($149.00 on sale) and charge my bike with 100% solar power by running 2x 4s solar panels. If I had a good BMS it would not be a problem, however, The cheap BMS units I tested, do not seem to balance or have a HV cutoff. So, I have been looking for a simple high voltage cut-off circuit that I could set somewhere around 62 volts. I have looked at modifying a 12v circuit. Here is the schematic and board:











Here is another HVC system that might work:






I was hoping a 62v shut off would be just be a few resistors, diodes, and a transistor (FET). Can anyone point me in the right direction?


Thanks
Seal Beach, CA

Odd that your BMS don't have balance or HVC, as that's a really common feature even in the cheapies. Which ones do you have?


Regarding an external HVC there are a few adjustable / programmable units that've been discussed and tested here on ES, often in charger/charging threads. One such post:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=92887&p=1361149&hilit=volt%2A+relay%2A#p1361149

another
https://endless-sphere.com/forums/viewtopic.php?f=14&t=91137&p=1329447&hilit=volt%2A+relay%2A#p1329447

those particular ones might not be high enough voltage for you, but others probably are.

this one in this picture can monitor up to 99 volts. And I have use this one in solar and works everytime. (cost about 6 dollars). I have it trigger the larger 30 amp relay that I connect between the solar panel and controller. I always disconnect the panel, if you disconnect at battery, the controller will start acting weird (cycling back and forth) with no battery connected.

You can build your own but it will probably cost more than off the shelf. But I would only use these in a perfectly balance battery, if the battery is severely out of balance it can reach the shutoff voltage with one of the cells over its max voltage.