Alternate way to charge your C Li-ion cells

[cernobila]

From another thread it has been shown that the WF-139 can be used to charge the C size Li-ion cells using the C holders, few bits and some soldering work. Pulled the unit apart, using sharp blade cut out the small slots to expose the ends of the "+" terminals to fit small "crocodile" clamps. Assembled the unit and ready to charge my C cells. This does not affect the normal use of the charger.











Few more pictures with a bit more detail

 

[DM51]

It will take up to ~7 hrs to charge them.

 

[cernobila]

It will take up to ~7 hrs to charge them.

Thanks for the heads up on the charging time, at least I wont panic when it takes so long......Is there a charger that is just like the WF-139 but designed for the "C" Li-ions?

 

[c0t0d0s0]

That's exactly how i charged mine. WF-139, C-size holders from RadioShack, crocodile clips. Works like a charm, but with 500mA charging rate, it takes forefer

 

[cernobila]

That's exactly how i charged mine. WF-139, C-size holders from RadioShack, crocodile clips. Works like a charm, but with 500mA charging rate, it takes forefer

I hear you........just as well I got myself two sets of cells, one in the light and one spare with plenty of time for charging......this is not going to be my everyday light so not much of an issue.....

Like I said, until something ideal comes along then this will have to do....

 

[medicmerlynn]

this is awesome... but exactly which 'unit' did you pull apart? what is just rendering the aw + charging post out a little? or did you literally take the entire thing apart? just curious... and this looks like it would take 'maybe' 10 minutes from start to finish to do... including warmup time for my archaic soldering gun...

 

[cernobila]

this is awesome... but exactly which 'unit' did you pull apart? what is just rendering the aw + charging post out a little? or did you literally take the entire thing apart? just curious... and this looks like it would take 'maybe' 10 minutes from start to finish to do... including warmup time for my archaic soldering gun...

Unscrew the base, (one screw under the sticker, the other is visible) after you lift the circuit board out slightly unhook the springs from the "-" terminals and then separate the circuit board section from the grey cover. Using a sharp stanley knife cut out the bits as per picture so that when you replace the circuit board panel back into the grey cover, the ends of the "+" terminals will be exposed. While you are reinstalling the circuit board, rehook the springs to the "-" terminals, replace the black base and that's it. Now you can use small crocodile clips when you need to. The unit is not affected in its original use.

Nothing has been done to the circuit board or any of the components on it.....basically just cut some plastic away on the cover. Entered few more pictures with more detail.

 

[DM51]

Thanks for the heads up on the charging time, at least I wont panic when it takes so long......Is there a charger that is just like the WF-139 but designed for the "C" Li-ions?

The trouble with all the budget 2-bay 'automatic' Li-Ion chargers, even the good ones like the Pila IBC, is that the charging rate is quite low for large cells. Most are in the range 450mA – 800mA per bay, which means slow charging rates. This is because they are a compromise, designed to charge a range of Li-Ion cells, usually from R123s to 18650s.

To calculate the approximate charge time, divide the output into the cell's capacity.

Incidentally, please do not even THINK about combining the output from 2 bays into 1 cell!

The capacity of a cell is given in milliamp-hours (mAh). A "C" Li-Ion is 3,300mAh, an 18650 cell will typically have a capacity of 2200mAh, a R123 cell would be 750mAh and a 10440 cell 320mAh.

Some manufacturers blatantly overstate the capacity of their cells. Any figures that significantly exceed those given above should be regarded with suspicion (the more the claimed figures are inflated, the worse the cells are likely to be).

The safe charge and discharge rates for cells are given as a multiple of a figure known as 'C'. Li-Ion cells should ideally be charged at 0.7C. The charge rate should never exceed 1C.

C is a figure for current, measured in mA, which is easily obtained from a cell's capacity. Using the figures above, just knock off the 'h' and you have the figure for 1C: it is 3300mA for a "C" Li-Ion, 2200mA for an 18650, 750mA for a R123, 320mA for a 10440, etc. This is therefore the maximum safe charging current in each case for that capacity cell.

You can immediately see from the figures for 1C above, that most budget chargers should not be used with cells smaller than R123 size. Equally, they are not ideal for "C" Li-Ions, whose capacity is 3,300mAh, because the charge time will be very long.

A solution for some people will be to invest in a hobby charger, such as Hyperion, Triton or Schulze. There are many models to choose from. The Schulze is the Rolls-Royce of the bunch, but it is complicated and takes some getting used to. It will handle every requirement.

Hobby chargers are more expensive, but they have numerous advantages and as they will do the job of a number of smaller chargers you would otherwise require for all your different cells, they may work out cheaper too – especially as they offer other advantages such as performing complete charge/discharge cycles for refreshing cells.

There will always be a place for the smaller budget chargers, which are invaluable for travelling and are very easy to use, but you should be aware of their limitations and you should always buy the best you can afford.

 

[donn_]

I've been looking at the Schulze line, and other similar chargers, but what I don't understand is where the cells go? Do they also sell banks of cell holders?

 

[medicmerlynn]

cernobila, thx a TON for descrip.... doesn't look to be all that hard. i guess i can just pick up 'any' alligator clips to work eh? Radio S#ack should have what i need eh?

 

[rizky_p]

i charged my spare mobile phone batteries with Ultrafire WF-139 because i dont have cradle for it.

 

[cernobila]

cernobila, thx a TON for descrip.... doesn't look to be all that hard. i guess i can just pick up 'any' alligator clips to work eh? Radio S#ack should have what i need eh?

If I can do it, anybody can........I ended up getting the smallest clips they had in the shop.....take the unit with you to make sure the clips fit....

 

[AndyTiedye]

1 of them will fit in a DSD with a spacer,
or into an UF-139 with a few magnets: