DIY: Repair Faulty NiMH Battery Instead of Buying New One

by:CTECHi     2019-11-27
This time I will show you how to fix the faulty NiMH battery instead of buying a new one. How I did it -
You can view it by watching DIY videos or follow the instructions below.
For this project you need: Material: good NiMH battery replacement tool for NiMH battery 2 bad battery with problem: the soldering iron screwdriver ImaxB6AC V2 or other smart chargerMultimeterI has two Bosch NiMH batteries from cordless power tools.
One performed very well, but the other was not very good.
In most cases, there are two reasons: first-
Natural battery wear, or only a small number of battery deaths in the battery pack.
Because NiMH chemistry here doesn\'t work as it does on a NiCd battery.
Therefore, bad cells must be identified and replaced.
Both batteries are fully charged with the original charger.
Let\'s see what voltage they keep.
The 18 V battery must be kept around 21 V and fully charged.
15 cells multiplied by 1, 4, V
When each battery is fully charged, 1-4 V is the top voltage of each battery.
Okay, 21, 7 V.
The second battery shows 19 V, so there must be a problem.
There is a gap of 2,7 V compared to a good battery.
By looking at this number and knowing that both batteries are fully charged
I guess there are two dead cells in it.
Let\'s take it apart and see what it looks like inside.
The nominal voltage of a NiMH battery is 1, 2 V.
Fully charged, they can have up to 1,45 V.
So my guess makes sense.
Everything looks good.
No leaking or corroded batteries.
Let\'s check the voltage of a single battery and identify the bad one.
Like I guess, there are two dead cells, 0,05 V and 0,11 V, respectively.
All the others are good ~ 1-4 V.
Before starting the repair process, I used my Imax B6AC V2 charger and discharged 3 randomly picked batteries at a voltage of load 2A to 1 v because at 1
I did this because I was wondering how much juice was left on the good battery and it was worth fixing the battery.
The capacity of these three cells is around 2Ah.
So this battery is still very good.
I bought two NiMH batteries at the local electronics parts store.
They are rated at 2, 8Ah and have spot welding labels which will help me to weld the battery.
I paid 3 euros per phone so it would be a very cheap solution.
It can also be purchased on ebay, Amazon or other online stores.
Remove bad cells with knives and cutters.
Welding new batteries in place.
Final voltage check-
Is the battery welded correctly.
Reassemble everything back into the battery case and charge it.
A few minutes later, the charger showed that the battery was full.
What about voltage?
It should be a healthy battery full of electricity ~ 21, 7 V.
There is a problem with the NiMH battery for cordless power tools and it doesn\'t always mean that you have to throw it away and buy a new one.
Most of the time, you can only change a few bad cells inside and keep it running.
I hope this is helpful!
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