Hey dudes and dudettes,


I am a bit uncertain about the whole parallel charging. The main question is, if your batterys are not discharged to the same voltage level... let's say one battery is at 14.0V and the other one at 14.8V, I would think that I could just put them together on a parallel charging board so they can balance eachother out. Let's say they stay like this for 10 minutes. Then I could plug the board into a charger and charge them together.

Is my thought correct? The only thing I could think of that would be a danger would be a too high current between the two batterys, but shouldn't that only be a problem if one is discharged to 14V and the other one is completely charge to 16.8V?

What are your thoughts and expiriences on that?

Because it would be great if I just flew one pack *stick it on the board* next pack *stick it on the board* next pack *stick it on the board until I have 4-6 and then charge them all together

Oscar has a good tutorial on this here: https://oscarliang.com/parallel-charging-multiple-lipo/

In particular, he mentions difference in voltage (and making sure to plug in discharge leads first).

I think I will parallel charge all my batterys in the future as I described. Adding them together one after another after each flight BUT as you said or Oscar said, with the discharge leads first. That's a very important point I didn't think of.

That will equalize the overall voltage so the cell voltage should be very close to eachother when the balance leads are plugged in.

This is of course not exactly as Oscar put it, but as a skilled electronics technician I think the risk here is within a reasonable range and of course I won't leave the batteries outside my view while they are charging.

The issue is that the batteries will try to equalise the voltage very fast and the battery with higher voltage will deliver much more amps than the battery with lower voltage will safely be able to handle (would be great if we could charge batteries at the same C rating we can discharge them - we'd have megawatt chargers by now ). Since batteries are most unstable when charging, you could easily end up with fireworks. The higher the difference of voltage the higher the risk in this case.
Another weak point is the parallel board itself - if the current is too high, the leads could just melt. Once I accidentally plugged a balance lead upside down and it wasn't pretty, it melted the leads before I could even blink . The discharge ones are much larger but given enough amps...

Personally I always stick to ±0.2v difference and if a pack is too low I charge it a bit before joining the others or if it's too high I charge the others before plugging in the pack.

I stick to 0,1V per cell difference. Generally it is a good idea to storage charge your packs after a flying session if any of them are far from 3.8 per cell. For example if I have a few with 3.75 and some with lets say 3.6, I storage charge all the packs with lower voltage and leave those 3.75. This way I can put them all on parallel charge at once.

BTW storage charging from 3.5-3.6 takes maybe 10 minutes to reach 3.8 and makes the preparation for next flying session much shorter.

I'll plug packs into my parallel charge board with differences of up to half a volt, discharge leads first, but no more than that.