How to change voltage on 16s charger? No trim pot

[cloudy]

I ordered and recieved a charger from ebay that's supposed to be 67.2V for my 16S battery. Measured open circuit, it's giving closer to 70V :? . I don't know if it will actually charge my battery to this level, and really do not want to find out the hard way. I trust the multi meter but don't have an accurate way to verify.

The seller is so far unresponsive so I've opened it to see if there is voltage adjustment. No trim pot to be found under the heat sinks, some larger resistors that look like shunts for current sensing, and a few small SM resistors on the other side of the board.

Does anyone know how to change voltage on these generic chargers? Shipping 70v chargers advertised as 67V seems like a battery fire waiting to happen.

 

[cloudy]

For what its worth, here's a solution to my own problem: use a charge controller chip in series to cut off the charger at a defined voltage. Xy-L10a allows you to set an end of charge voltage with push buttons. It's fairly easy to use, cheap and hopefully reliable. Im charging to around 4v per cell for most rides, more if I want the extra range or speed. I'm unsure of the failure modes on this chip, hopefully it goes open circuit instead of staying connected and over charging my battery.

I usually time limit charging as well as a back up to prevent overcharging:
The white plug thing in the background is an energy meter smart plug, this allows charge scheduling, timing and also measures consumption. It connects to wifi and controlled from your phone. Ive found these fairly useful around the house and they are pretty cheap at the hardware store.

Let me know what I'm missing please.