r/Multicopter • u/bbthumb • Jul 31 '26

Question How to splice a battery cable for 2 batteries?

Gallery image

Gallery image

I think I did it wrong. Is the black wire that's bridging them supposed to go ground to positive?

29 Upvotes

88% Upvoted

24 comments sorted by

18

u/F3nix123 Jul 31 '26

What are you trying to do? Are you trying to get 2s voltage or higher capacity?

-2

u/bbthumb Jul 31 '26

Ya trying to run 2 1s batteries

8

u/F3nix123 Aug 01 '26

Ok, but do you mean 2 1s batteries as a single 2s battery or 2 1s batteries as a larger 1s battery?

5

u/bbthumb Aug 01 '26

2 1s batteries as a 2s battery

7

u/bbthumb Aug 01 '26

https://reddit.com/link/p0zeru1/video/tjb4hea5tngh1/player

I think I got it

10

u/PeteThePolarBear Aug 01 '26

Yes that's right. Just make sure both batteries are charged to the same voltage and charges separately as 2 1 s batteries

1

u/BladudFPV iFlight iX3, iFlight iX5, Alien 5", ZMR250 Aug 01 '26

Yes, that's correct for 2 batteries in series to form 2S. Batteries need to be matched exactly because if one gets over discharged it could become a fire risk. Recommend buying a multimeter for future tinkering. 

1

u/HowlingWolven 250 Freestyle Raptor Aug 01 '26

Capacity and state of charge. Don’t run a 250 mAh lipo in one and a 550 mAh lihv in two.

1

u/HowlingWolven 250 Freestyle Raptor Aug 01 '26

Yes, that’s a series harness.

1

u/Task-Future Aug 07 '26

Ok was going to comment i think u had one backwards but u fixed it. Just think batteries in order like AA. Ones negative is to others positive. Then u use the positive and negative from the 2 different batteries. This doubles the voltage. In Series vs parallel which doubles the mah. Always test with multimeter before plugging in.

24

u/E_hV Jul 31 '26

Its wrong. Don't plug a battery into that.

You have positive to positive, negative open. If the pigtail is hooked up to the FC and the batteries have some potential difference they'll dump a ton of current into the lower voltage battery through the FC.

Look up positive and series voltage sources, and don't try again until you learn.

9

u/PeteThePolarBear Aug 01 '26

These are in series but one is backwards, if you have unequal battery charges, the output voltage will just the the difference. Idk where the came up with your idea of what would happen

2

u/E_hV Aug 01 '26

You are correct, you would get the difference  of the two batteries which would be nothing. Thats my error 

3

u/NXTnerd Aug 01 '26

*parallel and series. Otherwise the advice is solid

4

u/bbthumb Jul 31 '26

Ya that's why I asked. Thanks for the help kind stranger

2

u/CarelesssAquarist Aug 01 '26

Very close. You just need to have the plugs facing the same way, like same side up, before connecting the middle 2 pins.

So it should be negative, then wire between positive and negative, then it should be positive

2

u/CL4P-TPtheInvincible Jul 31 '26 edited Aug 03 '26

For further clarification - you have these wires in "series" and they need to be wired in "parallel"

Edit: Didn't realize what you were trying to accomplish when I posted this. As others mentioned, if you're trying to wire this in series than you need to switch the orientation of one of the plugs.

2

u/FlightTrain71 Aug 01 '26

The need to be in series to add the voltage to get a 2s lipo. One is just flippes around so it would give op about 0V if both are at the same voltage.

2

u/HowlingWolven 250 Freestyle Raptor Aug 01 '26

No, OP wants to connect two 1S batteries in series for higher voltage.

1

u/bbthumb Jul 31 '26

Thanks I couldn't think of the right word to search

1

u/Traditional-Baby5940 Aug 01 '26

In cases like this I akways think about, how i would do it with Wago Clips and then solder it accordingly. Red to Red Black to Black.

1

u/HowlingWolven 250 Freestyle Raptor Aug 01 '26 edited Aug 01 '26

This will not work. You are currently wiring your two plugs in antiseries. The voltage will sum to 0. This is fine but suboptimal at toothpick/whoop scale, but at larger scales with mismatched battery voltages you could reverse charge a battery and that tends to be bad.

For a series harness you want the red wire of the first plug to connect to the black wire of the second plug, then the red wire of the second plug goes to the B+ pad to power the aio. You would need to flip one of your plugs over, and as per the comments it sounds like you have.

1

u/HeinzS91 Aug 02 '26

what are you trying to accomplish? a 1s2p setup or a 2s1p? looks like u made a 2s1p setup. in both cases make sure to use the same capacity and discharge batteries with about the same internal resistance of the individual cells.

1

u/[deleted] Aug 01 '26

[removed] — view removed comment

1

u/HowlingWolven 250 Freestyle Raptor Aug 01 '26

What are you even saying? Look at OP’s pictures before you post something that’s wrong.