as I got information, Hobbyking won't be selling Multistar 4S batteries 8 and 10Ah anymore. I would like to build pack from 2x 4Ah which are still in stock in EU. I wanna tape both batteries to one piece and solder power and balance connectors in paralel way. On paralel cells will be always same voltage.
Is it good idea use it like this during discharging ?
why not just keep the existing battery packs and use a 2 -1 adapter to plug in both batteries. I've been doing this for years and never had problems. its also much easier to charge the separate packs .
If you solder the packs together then you cannot balance charge the packs together.. also if one pack fails its easy to change out.
In one pack it will act as 4S2P, I can charge it and balance with one power and one balance connector. Less wires, better handling/connecting. I have charger for 6S battery max, I can't charge two 4S together. Parallel connection when batteries are discharged can be dangerous as on cells are different voltages.
Yes and no .
Yes it will work but its still a lot of work to complete instead of a simple 2-1 adapter
You can charge 2 x 4S batteries together in parallel which is exactly what you are doing with your modification.
remember you dont need to balance charge every time. In my case I balance charge every pack the night before I need them and if I need to recharge at the flying site I can parallel charge 2 packs but do not use the balance port. its also quicker.
The charge time for 1 pack is half the time for 2 packs together.
I have yet to see any one demonstrate any problem with connecting 2 batteries that are at different levels of charge. yes, they will both assume a charge level midpoint between the 2 extremes as one charges the other and they will then both need to be charged. keeping same level packs it to be preferred.