Actually that’s true. I received my new vesc yesterday from @chaka and it has those diesel XT90 connectors on it with heavy duty 10 gauge wire and it doesn’t spark at all when I plug it in. Super nice.
Hello guys! Sorry for posting in an old thread but my problem perfectly fits in here. So I plan a build with 2 3s lipo packs wired in series. I bought this serial charging harness - http://www.hobbyking.com/hobbyking/store/__10993__Twin_pack_charge_lead_2_x_3S_6S_w_XT60.html, which has XT60 plug for charging while my imax b6 charger’s cable has a dean plug. today I removed the xt60 from the harness and soldered the dean connector to be able to connect the charger’s cable and the harness. Then I thought I’d try to connect the batteries (though there were not used yet, completely new) and the harness together - to check the soldering quality - to see if voltage would be there with a voltmeter. So I connected to batteries in series (as on photo), then I plugged the 1st balance lead into the harness’ port - all was good, when i connected the 2nd batteries balance lead - there was a pretty good spark, you can see the damage of one of the pins. could this have damaged the lipo? I measured the voltage afterwards - was fine.
I am a real newbie. Can someone tell me what did I do wrong? I tried to read the forums and this thread and if i understood well i should cut out the black wire of one of the balancing leads according to @lowGuido’s beautiful diagram. But I feel confused because everyone else seems to use my type of harness without any troubles. Thanks in advance.
heres what you do:
- Wire the batteries in series FIRST
- take your 2x 3s to 6s adapter and cut the black wire closest to the middle ( you will need to cut through the heat shrink)
- Now you should be able to run this safely if you plug in the lipo alarm/voltage reader and it shows 3s, switch the two connectors around.
If you do this in any other order expect to get a shit ton of sparks
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Hi, thanks a lot for your reply. I uploaded the photo of harness once more - I assume you refer to the thin black wire of the 6 pin balancing lead?
Does it matter where I cut this wire if I isolate the cut pieces well? I would also appreciate if you could shortly tell me why does this wire cause sparks? And I find it strange that this piece is sold as a plug-n-play product and there are some extra tweaks required… I also saw other people’s reviews on HK - they all seemed happy and noone mentioned cutting wires. 
Will I actually be fine charging through this harness - I mean using the dean plug I soldered? My plan was to do charge over the harness keeping batteries in the board however with a disconnected circuit (XT90s loop switch).
Thanks a lot!
Edit: BTW, you emphasized the order but you didn’t mention the right moment for connecting the batteries to the harness - should it always stay connected or it doesn’t matter when you connect them?
I should also mention I used this exact product, and charging was horrendously slow due to it being charged through balance leads. Instead, wire a xt60/Dean in parallel to the wires feeding to your ESC and plug in through that, it will provide a higher current.
- Yes I mean the thin wire on the 6 pin. You should isolate it.
- It shorts out, thus sparking.
- you should be fine charging with this harness, though like I said above its not as fast.
- Connect the batteries after all my steps
Thank you. so you recommend the following wiring (creation of @lowGuido):
I have couple of questions:
- I read somewhere that it’s not good to have long wires between the battery and esc, I guess it is not true?
- what is the min wire thickness I should stick to for charging wires - I read somewhere that AWG10 is min, is it?
Yes that diagram is great. 12 AWG is pushing it, 10AWG is perfect for our use. Wire length shouldn’t matter as long as it’s not 3+ ft. Though you want to try and keep it as short as possible. If you are using a VESC and FOC, keep it very very short!
You need to make sure that your most negative battery has its balance leads plugged into the negative side of the balance connector. Getting this wrong is what causes your short. (Spark)
Thanks for reply. Could you please clarify what means " the most negative battery" - the one with a negative terminal going to ESC?
And how do to determine which one of two balance slots is negative? Sorry for the “newbie” questions.
Will the method described by @link5505 - disconnecting the thin black wire of the harness balance lead will eliminate the necessity of watching for the most negative battery?
Thanks.
I don’t know what’s the AWG of the wire I have but it’s from the electric kettle - so handles 240v normally, and current of certainly 16A. That should do, right?
BTW: is it an idea if I use those wire endings / terminals (donnow how it’s called in English) to create parallel wire splittings for charging? I hope you get what I mean ? 
I would love to get a confirmation from someone. Thanks in advance.
that kettle wire will not do the job. buy some nice 12 AWG at a MINIMUM.
the “most negative battery” would be the one on the right of my diagram, the one that has the big negative wire to the ESC.
Hi, thanks for your advice, I did get some super thick wires - my colleagues use them for assembling the electric car chargers. AWG number isn’t there but the its a stranded copper wire with a total cross section of certainly more than 3mm.
Will the method described by @link5505 - disconnecting the thin black wire of the harness balance lead will eliminate the necessity of watching for the most negative battery? Thanks.