Bike cutting out when battery on 3 bars

Nealh

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Aug 7, 2014
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I now only use Fogstar who sell only genuine sourced cells, but like most sellers supplies are scarce.
 
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bikemerchant

Pedelecer
Dec 17, 2021
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So I would buy something like this, use a scissors to cut off the end nub that would charge whatever it’s designed for, and a negative and positive wire should pop out of it?

Are they color coded so I know which is which?
 

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soundwave

Esteemed Pedelecer
May 23, 2015
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So I would buy something like this, use a scissors to cut off the end nub that would charge whatever it’s designed for, and a negative and positive wire should pop out of it?

Are they color coded so I know which is which?
the best advice i can give you is send it to someone that knows what they are doing, as even if you raise the voltage of that cell bank the bms stopped charging it for a reason.

what has the seller said about this ? as you cant keep using the batt in this state as will just get worse if you keep using it.

given the size of the batt and you have no tools or any idea what to do this repair attempt is not for you as you short that thing and could end in a 12ft high fire ball.
 

bikemerchant

Pedelecer
Dec 17, 2021
69
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This is where the seller bought it
and he said it is in warranty for 3 months more so has sent them photos of multimeter readings to see if they will replace the battery.

Where should I look for someone who can repair it for me? I'm in Ireland,(the 2 links provided already are UK based services).
I googled "battery repair" near my town and shot out a few emails but no joy.
Called the local independent bike repair man who doesn't do battery repairs and said he doesn't think I will find anyone that will do it for me.
 

soundwave

Esteemed Pedelecer
May 23, 2015
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This is where the seller bought it
and he said it is in warranty for 3 months more so has sent them photos of multimeter readings to see if they will replace the battery.

Where should I look for someone who can repair it for me? I'm in Ireland,(the 2 links provided already are UK based services).
I googled "battery repair" near my town and shot out a few emails but no joy.
Called the local independent bike repair man who doesn't do battery repairs and said he doesn't think I will find anyone that will do it for me.
if he sys it is still in warranty id not touch it anymore and see what he comes back with to fixing the problem.
 

Nealh

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Aug 7, 2014
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Any old phone charger that is 5v will suffice, look carefully at the two wires the 5v/+ wire should have a stripe colour on one of them. But what one should do bare the ends put the probes on them and check for polarity, checking for polarity is one of the very basics with owning a meter. If one doesn't know then one should be asking themselves questions.
 

matthewslack

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Nov 26, 2021
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This is where the seller bought it
and he said it is in warranty for 3 months more so has sent them photos of multimeter readings to see if they will replace the battery.

Where should I look for someone who can repair it for me? I'm in Ireland,(the 2 links provided already are UK based services).
I googled "battery repair" near my town and shot out a few emails but no joy.
Called the local independent bike repair man who doesn't do battery repairs and said he doesn't think I will find anyone that will do it for me.
While you work out what to do next, check the cell voltage each day, and see if is stable or going down. Might give another clue about what is going on.
 

Nealh

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Aug 7, 2014
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While you work out what to do next, check the cell voltage each day, and see if is stable or going down. Might give another clue about what is going on.
If mine I would charge balance and leave it to sit to see what occurs as you have said Matthew, if the voltage changes I would then do it again but this time with the BMS sense wires disconnected to rule out an open/faulty bleed resistor.
If the result ended up the same still then one would have to say the cell group is at fault and are either self discharging or just weak with high internal resistance.
 

bikemerchant

Pedelecer
Dec 17, 2021
69
2
Any old phone charger that is 5v will suffice, look carefully at the two wires the 5v/+ wire should have a stripe colour on one of them. But what one should do bare the ends put the probes on them and check for polarity, checking for polarity is one of the very basics with owning a meter. If one doesn't know then one should be asking themselves questions.
I didn't know but do now after a quick google :)
So I should;
1 - Pop into a phone repair store, buy an old charger and strip it
2 - Rip the JST off to expose it (this I am worried about as it's stuck to the component behind it - photo attached in next post again)
3 - Insert the negative wire into the 10th slot of the JST and the positive wire into the 11th slot, to charge the weak 11th series
4 - Test this series with a multimeter as it charges, and also touch it to ensure it's not overheating.
5 - Stop charging when series it reaches 4.16V.


you cant keep using the batt in this state as will just get worse if you keep using it.
Is this true? How bad is it to keep using it? I've been doing about 8km per day on it, making sure it doesn't reach shut down level.
 

Nealh

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Aug 7, 2014
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The White JST's are a very tight snug fit they aren't glued or stuck in, they are a two piece connector the female part is soldered direct to the PCB and the male part with the multi wires simply pushes in. Pry/lever it out gently a bit at a time from each side to remove using the wood or plastic tool, the joint is clear to see where to separate .
Personally if one is baring any wires then they need soldering or a pin from a pin strip added to each end to insert in to the hole. Bare thin wires are too flexible and will bend trying to insert the bared end, likely a fine strand will short against the adjacent one.
Without soldering I would use the magnet/washer method direct on the cell group, then the wires can't short as they are on opposite sides of the battery.

You have been warned.
 

bikemerchant

Pedelecer
Dec 17, 2021
69
2
Thanks!

I found an old charger that has an output of 4.5-9.6V and 300-600ma, I assume this is no use and I need exactly 5v 500ma?

Can anyone link a video showing the magnet/washer method?

or solder each wire to a flat washer and use a magnet to attach said washers directly to the cell group to enable a slow charge.
So this can be done without soldering? I imagine I will have to buy a magnet like @wheeliepete suggested?
 

Nealh

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Aug 7, 2014
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Two strong magnets, one for each side.
 
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Nealh

Esteemed Pedelecer
Aug 7, 2014
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Yes that charger is no go as the min voltage is 4.5v which has too higher starting voltage, it has to be 5v or less as the cells max voltage is 4.2v.
 
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Sturmey

Esteemed Pedelecer
Jan 26, 2018
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Ireland
Hi. Just looking at the battery photos. I'm not sure how mechanically well put together that pack is. Anyhow, I would very carefully both visually and perhaps with insulated probe check all the welds of the cells in the 11 group. You could also try measuring the individual cell voltages in this group with a meter. A damaged/disconnected cell connection will probably put pressure on the remaining 5 cell in that group. Anyhow, its just a thought.
I live in Ireland and have bought cells from NKON without problems. No taxes, just delivery charge.
 

bikemerchant

Pedelecer
Dec 17, 2021
69
2
Thanks @Sturmey, do you know anywhere in Ireland that I could take the battery for repair?

If not I need to buy a 5v 500ma charger and the magnets to try to manually charge the group.
I know I already asked, but does anyone know where I can find a video or instructions on how to use the magnet/washer method?
 

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