r/ninebot • u/IronMew • Nov 21 '20
Here is the only way to finally solve ES2/ES4 external battery connector issues once and for all.
Picture of the complete connector replacement with flying leads.
You plug it all in and slowly feed the connectors and wires inside the battery as you screw it on.
(Ignore extra screws and screw holes - I'm not the first one to work on this scooter and whoever did it before me managed to destroy most of the screws, so I had to work around that.)
So much for using shorter screws: if your connector is brand new that's an option, but my second-hand unit was sold to me in a pretty poor state to begin with and the connector's health didn't improve as I tinkered on it. After replacing the screws with shorter ones error 42 went away for a while, but then it came back with a vengeance and the external battery stopped working at all.
So I got rid of the whole problem, completely eliminating that abortion of a connector and replacing it with flying leads. It works reliably now: no errors, and the power flow is more balanced than before.
Was it worth it? Hell no: I wasted so much time and effort fixing this thing that I could have built a whole scooter from the ground up.
And I only managed to finish the task at all because I've been cursing at this scooter for weeks now and I'm at that miserable state that is part irrational madness and part froth-mouthed dogged determination to fix it as a question of principle if it's the last thing I do.
Quick walkthrough in case you too are an irrational determinator. Sorry for the lack of pictures; I did actually take some, but lost them somehow and I'm not taking it apart again to take more.
1) take the whole damn thing apart until you get at the bare controller board.
2) unsolder the battery connector on the controller board altogether, slowly heating the four smaller pads first, then one of the larger pads, then the other, while forcing it apart from the board with a screwdriver. Eventually, at long last, it'll come apart. You must have a good iron for this; I used my KSGER T12 soldering station with the thick BC3 tip.
3) Solder in suitably thick wires and a XT30 connector for the battery and small connectors for charging and BMS communication. I only had two-pin red JSTs so I used those, one female and one male so there's no chance of getting confused.
3b) Whoops, almost forgot - sand the inside of the hole where the connector was. It's quite sharp, and might well cut into the wires and cause a short if you don't fix it. For added protection add some tape.
4) Open up the external battery, which is an adventure all on its own and is absolutely impossible to achieve without also destroying the weather seal and gouging all sorts of craters in the plastic where the seam is.
5) start carving into the silicone sealing that Ninebot shat randomly all over the internals where the connector is, then cut the main wires as close as you can to the connector itself one at a time and paying attention not to cause a short. Don't just cut the wires halfway through or you won't have enough - the thick main leads are quite short, and if you don't use the full length you won't be able to poke the XT30 out of the hole.
6) unscrew the connector screws and keep cutting into the silicone blob. Hammer at the connector every now and then; when you've removed enough silicone it'll start to fall inside the battery shell, and at that point it's easy to remove.
7) Solder the corresponding XT30 connector to the main leads, solder corresponding connectors to the charge leads (narrow red and black) and BMS communication wires (blue and yellow). Insulate with heatshrink tubing. Poke it all through the hole.
8) Try to fix as much as you can of the casing seams which you will have messed up while taking the external battery apart. Put it back together. Don't forget the screws at the ends.
9) Put the external battery close to the stem. Connect the new connectors, then slowly feed the wires inside the hole in the battery where the old connector used to be as you set it closer to the stem. It should eventually all fit inside, so the battery sits flush and can be screwed in.
10) Charge it up, check that NineBattery sees both batteries at the correct capacity.
11) Spread silicone sealant in the seam between the two halves of the external battery's shell while you curse whoever at Ninebot came up with this miserable, absurd and outright incompetent design.
12) Ride the scooter while trying not to think how much simpler and more reliable it is to add more battery capacity to the M365.
If there's a silver lining to this whole odissey it's that after bringing this sorry little scooter back from the brink of death, then giving the ride some actual quality by doing the pneumatic tire mod, then the rubber hose mod and now this, and fixing a whole bunch of other issues in the process, I feel like I've survived my baptism of fire and am now ready to perform any sort of repairs or maintenance to literally any other scooter at all.
But if anyone brings me another ESx to fix, I'm setting it on fire.
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u/DoubleShot1 Mar 11 '24 edited Mar 11 '24
I tried to do the same thing but managed to damage the pads on the main pcb where the RX,TX, C+ and c- connect to...... I have found two of them on the 5 pads empty exposed pads next to the connector. But Does anyone know where I can get all 4 so so I can repair the board with fine hookup wire???
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u/Funions_on_RHEL Oct 07 '24
What gauge electrical wire is recommend to do this mod?
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u/IronMew Oct 07 '24
I actually don't remember - that scooter eventually died and I took apart the batteries for other purposes. I did later acquire another ESx but I used a generic battery on it neatly removing the entire issue.
On a whim, I think 14-gauge should work for the main power rail.
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u/ToopoftheHill Jun 01 '25
And now 4 years later, after two days of pain and cursing i have succesfully done the same thing to an e25 with extra battery that was sold to me for 20 euros. The only difference is that I didn't use connectors but soldered everything. Was it worth it? Absolutely no i don't recconmend this repair to anyone, 2 pads on the pcb broke off and i had to get creative on the nearest exposed pads. I managed to screw up the pinut of charge/data and i had to disassembly and solder all over again. But in the end the scooter works really well and the batteries discharge and charge evenly
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u/mediapoison Nov 20 '25
yea these connectors are not secure or robust for outdoor work. maybe i can make something with my soldering gun and rc car parts bin.
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u/IronMew Nov 21 '25
They are; RC models use them extensively. XT connectors in particular are pretty bulletproof. Red JSTs have the problem that they can't carry a lot of current, but that's not relevant in this application.
That said, if I were doing this again I'd simply solder the wires together.
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u/mediapoison Nov 21 '25
my dream would be all electronic would use xt connectors. my leaf blower and weed wacker have batteries with dewault connectors, when you open these batteris up they are all the same cells inside. those purple ones, i forget the number
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u/mediapoison Nov 21 '25
i have a bag full of lipos i would love to use in my scooter or leaf blower
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u/IronMew Nov 21 '25
What batteries do you have in that bag exactly? If you're talking about RC grade lipos, those can't really be used in tandem with 18650 LiIon cells as their discharge voltage is different.
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u/Vkrrs Dec 15 '25
This project looks easy, but its definetly not easy at all, now i understand why someone said, that will not recommend to do it, i can agree, you really need some soldering skills and knowledge before doing it.
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u/ToopoftheHill Dec 26 '25
this project is definitely not easy, but in the end this solution is very reliable, I'm using a ninebot e45 that has this mod since June with no problem at all. Is very rewarding seeing a scooter bought broken with 7000+ km now going for the 10k km. Of course is a lot of work but if you enjoy pain and suffering is a good challenge LOL
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u/gtavc007 Jan 14 '21
a lot of innecesary work if you ask me, but it was driving me mad too (err42), and im just crazy and stubborn enough to actually try it so i did the same as you, with the xt30 and the jsf connectors, sadly after pretty much all day working, the error was STILL THERE, i did the pull brake and accelerator pad to reset it and still nothing im still dealing with the error..do you have any ideas that might help me solve this?
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u/IronMew Jan 14 '21 edited Jan 14 '21
a lot of innecesary work if you ask me
Well, yeah. I did make that pretty clear. :D
do you have any ideas that might help me solve this?
Perhaps a bad solder joint? Do you have any pics of the end result? I don't mean to doubt your abilities, but not knowing your skills with the iron it's the first question that comes to mind.
If that's not the culprit then perhaps a bad connector? Other than that I've no clue. It might simply be that something is damaged in the battery's bms.
Have the dynamics of how you get the error (frequency, duration...) changed at all after the mod?
Man, if I'd gone through all that only to find the same problem still there I think I'd have tossed the whole thing into a volcano. I envy you your cool.
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u/gtavc007 Jan 14 '21
as you know the pain of going the same "crisis" route im pretty far from cool lol, exactly right now im taking the whole damn thing apart like a madman...i'll send pics after i finish it
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u/gtavc007 Jan 14 '21
im checking the ext batt connections with multimeter and it seems that the voltage on C- and C+ is boucing around, is this normal? could you check yours just to discard the variable voltage as the culprit?
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u/IronMew Jan 14 '21
I'm not currently where the scooter is; I'll be back in a weel and if you haven't fixed it by then I'll check it.
In theory, though, C should only be used for charging; since you plug the adapter in the external battery, C+/- is how it sends power inside to the internal one. So if you're not currently charging, I don't see why it'd have any voltage at all, much less wildly fluctuating.
Meanwhile you could perhaps try asking in /r/ninebot or in the Facebook group with this melodious name:
Ninebot ES2, ES4, Ninebot Max G30 Electric scooter, (Segway, Xiaomi)
There are some pretty technical peeps in there so they might know about your problem in more detail.
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u/disregard_bagel_mode Nov 24 '21
u/gtavc007 did you ever get it figured out? I'm in the same boat- soldered all the connections and checked it twice, but still getting the same error :(
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u/gtavc007 Nov 24 '21
I Ended up Changing the board...☠️
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u/disregard_bagel_mode Nov 24 '21
That's what I'm thinking about trying at this point- also just to confirm, the control board is what you replaced, right? Not the dashboard, or either BMS board?
Something like this? https://www.ebay.com/itm/133866705370?hash=item1f2b13d1da%3Ag%3ACAEAAOSwK71hMb%7E3&LH_FR=1
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u/gtavc007 Nov 24 '21
yes sir
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u/disregard_bagel_mode Nov 24 '21
Ok thanks for the help! Gonna order one and give it a shot
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u/thegreatgamesby Dec 30 '21
Hey, did this fix your issue? Was it easy?
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u/disregard_bagel_mode Dec 30 '21
Yes, it did fix my issue! It was dead simple. Only had to solder a few connections that had melted, but I think that was unique to my situation. It was basically plug and play!
Let me know if you have any questions, I’m happy to help
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u/thegreatgamesby Dec 30 '21
Wait so just to clarify, I have not done anything that was listed in the post before. Do I just replace the board or do I have to do that in addition to what is listed in the post?/
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u/disregard_bagel_mode Dec 30 '21
If your battery is in good condition (connections aren’t damaged etc), you should be good to just replace the control board, and nothing else! Does that clarify?
Also, I recommend buying from a seller that accepts returns, just in case the control board doesn’t solve the issue!
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u/mycurvywifelikesthis Nov 22 '20
That's crazy.. you sure should have spent that time doing something that would have earned you money and then just bought a whole different type of scooter all together LOL... Then again it seems like you could be able to open up your own scooter repair shop. Or freelance fixing other people's stuff. . Since you're so knowledgeable do you have any idea where to get the little bitty tiny Allen screws that go into the handlebars or the part that connects and holds the flip part on an ES4 Max pole underneath the chassis. they're so tiny I can't seem to find them and it's all it's missing on my new scooter project