Hi guys I searched but couldnt really find an answer… If I only need a BMS for charging, and have 3 x 3s2p zippy lipos, could I use some of the bms boards from ebay, for 3S ?
I would only use bms for balance charging… not running from, but wouldn’t it still be fine, instead of buying an expensive 9s bms ? 
no. Unless you want to use 3 BMS’s. If you use a 3S BMS in a 9S system I would not be surprised if you start a fire. (at the very least you are going to get smoke)
I would of course use 3 of them yes… and then connecting them for each battery
any comments ?
i would save the headache and look for a 9s bms
If you use the balance leads only this should be possible. There was a nice video posted yesterday on how to charge a 12s battery with a 6s charger. You have to solder to wires to the positive and negative balance leads and use those for charging. I can’t find the thread though. If it’s unclear I will look for it tomorrow.