So I decided to replace the cells myself, my tools were a soldering iron, a T9 screwdriver, small sidecutters, 2 x 3" of insulated red wire and 1 x 3" of black insulated wire.
The original cells in my battery pack are 3.6v 4400mAh x 4. Replacement Li-ion cells came from a well known auction site were 3.6v 6600mAh x 4, so a +50% capacity. I bought 'tagged' cells which make replacement easier.
The four cells are configured in a series-parallel format to provide the required 7.2v @ 6600mAh capacity.
I noted the polarity of the original cells and then I de-soldered the original batteries from the charge protector which remains in the battery pod. I then arranged my new cells in the series-parallel format soldering the tags and adding the 2 x 3" of red and 1 x 3" of black wire. One red (positive) and one black (negative) wire are connected to the 7.2v output and the other red wire is connected to the 3.6v output - this wire is connected to the positve voltage supply for the charge protector.
Half an hours work and at a cost of £23.99 ............. a saving of over £100 !!
My next project is to replace the battery in my WM10 unit, this battery has its own charge protector built-in so will be much easier to do. The battery for this cost me just £6.78. Now I'm not sure if this is a repairable item, the 3030 battery pack is not, so its probable the WM10 is the same, however replacement of this is £180 - a lot of money if its just the battery!
This is how I repaired my battery pack, it is not a 'how to do it', so I will not accept any responsibility if someone does theirs and it all goes wrong.
Do not attempt this unless you are competent to do so.
As a guide, Panasonic brand ones are 3400 mAh.
Unfortunately, it's a nuisance to determine capacity, without constant-current discharge equipment,etc.
It's also worth pointing out (for anyone else's benefit) that some cells are longer than standard, and may not physically fit, they're supposed to be 65mm, but many are up to 4mm longer, some of which depends if they're button topped or flat.
I see the packs are described as 34 Wh, which if you take their 'nominal' voltage as 7.2V, works out as 4700 mAh, that would be 4 cells of about 2400 mAh each? Unless there are two types of battery packs? (like some laptop computers)
As a guide, Panasonic brand ones are 3400 mAh."
These are the batteries I used:- From Japan
PANASONIC NCR18650B Li-Ion 3400mAh 3.6V LITHIUM Rechargeable BATTERY TAGS x 4
2 pairs in parallel = 3.6v 3400mAh, and connected in series = 7.2v 6800mAh
The original batteries are MINMAX and are manufactured in China.
They are 4 x 3.6v 2200mAh which total 7.2v 4400mah capacity.
I found this interesting 18650 comparison test, online:
http://lygte-info.dk/review/batteries20 ... %20UK.html
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Series is positive of one battery connected to negative of another, think of two or more cars parked nose to tail, your positive would come from the front of the lead car and the negative from the back of the rear car.
So 2x 1.5v 2000 mAh = 3v 2000 mAh
Batteries in parallel add up the mAh, voltage stays the same as one battery.
Parallel would be all the cars parked side by side with all the fronts connected together, this is your positive, and all the rears connected which would be the negative.
So 2x 1.5v 2000 mAh = 1.5v 4000 mAh
So 2x in parallel in series with 2x parallel i.e. 4 cells
= 1.5v 4000 mAh + 1.5v 4000 mAh = 3v 4000 mAh.
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