Double battery power for drone

[ThomasEekels]

Hi All,

i am planning to extend the flight of my drone, by adding a 2nd battery.
The max payload of my drone is more than the weight of an additional battery, so that is not the problem.

For now, I have designed a docking station that comes in place of the original battery and that has a cable splitter, so I can connect 2 identical Lipo's through that. I will carry the 2 Lipo's externally in a bay, between the landing gears.

The question is about the connection. I have understood that parallel connection can be done safely when voltages are between 0.1 difference between the 2 lipo's. I can measure that after charging and balancing.

What should I expect at connection time... heat building-up while the 2 batteries even out ? Is it safe ? Are there additional precautions to make ? Should I keep them in parallel during charging ? In that setting I can not balance charge them I presume.

Is it a good idea ?

Thomas

 

[JackFlorey]

What should I expect at connection time... heat building-up while the 2 batteries even out ? Is it safe ? Are there additional precautions to make ? Should I keep them in parallel during charging ? In that setting I can not balance charge them I presume.

1) It's pretty safe to connect them in parallel.
2) You won't notice any heating. (If you do, balance them better the next time you try it.)
3) You can charge in parallel. The charge termination algorithm is designed for one battery, not two - but the difference is small and in most cases you won't notice the difference.

 

[jonyjoe303]

You can keep them in parallel when charging as long as the balance connectors are also connected together. Also during use keep the balance connecters connected together. This will keep the entire pack equalized during use. You will just have one large battery pack. And you will still be able to balance charge.

As long as the the batteries are close in voltage, there won't be too much amps moving from one battery to the other. You need a big voltage differential to see a major amp movement. At 0.1 difference, you won't see any type of activity between both packs. I used a dc wattmeter before to measure amps when connecting 2 batteries together, I never notice high amps going from 1 battery to another even when the voltage wasn't that close.

They sell a balancing board to charge multiple batteries. But its not needed, just make your own y-connecters, and also y-balance connectors.

 

[ThomasEekels]

Yonyjou,
do you mean I do not have to disconnect them to balance charge them ?

So not just plug both mains into a y-plug, but also plug both 3s-balance plugs into a self-made 3s balance y-plug ?
As such, I can balance-charge the dual pack as one (in my Imax B6 ? )

 

[amberwolf]

yes, exactly.

 

[ThomasEekels]

ever seen any balance 3s y-cable at Ali ?

 

[amberwolf]

dunno about ali (i generally prefer to avoid those places), but there's lots of them out there:

https://www.google.com/search?q=balance+3s+y-cable

dependign on where you live there's bound to be somewhere that won't take potentially months to get it to you.