Charging a Lithium Ion Battery Pack?

[tony from suffolk]

Maybe this should be in idle chat because it's not a caving light, but I figured here would be a nore likely place to attract the experts in such things.

I've been given a Ring LED ultra-bright compact inspection light which contains Li Ion batteries but alas there's no charger with it, and Ring don't offer this as a spare. It's got a single socket on the side for a wall-wart type charger plug & it appears to be 3.5 volts (although unusually I cannot find the exact specification for it).

I understand these require a special charger. Any help and advice would be appreciated.

 

[royfellows]

Try the Internet for more technical info, its odd that the manufacturer does not supply a charger!

Where do you get 3.5V from?

IF it contains parallel Li Ion cells, nominal voltage 3.7V, 4.2V fresh off charge, you would easily be able to adapt a standard dedicated mains adaptor Li Ion charger by fitting a suitable plug. This type of charger usually comes with a jack plug, but sizes vary and may not be compatible out of the box.

You will pick up a charger mains adapter off eBay. Be sure to get the right one, output 4.2V

Only thing is charging time could be slow due to number of cells in the array. Mains adaptor chargers usually output 1 amp, so if 4 cells in the array sharing the output current then it will only be charging at 250 mA. Not a bad thing for the cells, and people usually leave overnight anyway.

 

[tony from suffolk]

Thanks Roy, that's very helpful. This light was given to me by someone who found it in the garage of a new house they bought, so no charger and you can't buy one as a spare (well, not that I can find by an internet search).

The chargers I've seen on e-Bay and the like seem to mostly have USB leads but I'm pretty handy with a soldering iron so no problem adapting one. I don't mind a long charging time, it'll just be for occasional use.

 

[peterk]

12vDC if this the light shown on the Ring website  http://www.ringautomotive.co.uk/uk/products/Workshop+Tools/Inspection+Lamps/LED+Cordless+Inspection+Lamps/ril2500hp

 

[royfellows]

If its 12V you will need a different type of charger as it would be 3 series cells. My 12V lamps balance charge. You really need to find out more about the lamp. Guesswork does not go well with Lithium Ion cells. Beware.

 

[tony from suffolk]

12vDC if this the light shown on the Ring website  http://www.ringautomotive.co.uk/uk/products/Workshop+Tools/Inspection+Lamps/LED+Cordless+Inspection+Lamps/ril2500hp

  That's the light, but I don't believe it's 12V, that refers to the charger that'll run off 12volts.

 

[bograt]

Could you adapt a phone charger?

 

[royfellows]

12vDC if this the light shown on the Ring website  http://www.ringautomotive.co.uk/uk/products/Workshop+Tools/Inspection+Lamps/LED+Cordless+Inspection+Lamps/ril2500hp

  That's the light, but I don't believe it's 12V, that refers to the charger that'll run off 12volts.

Sounds like a 4.2V dedicated charger that runs off a 12V DC mains adaptor.
One of the useful things about this setup is that a 12V vehicle adaptor will recharge your lamp, but beware HGVs which I believe are 24V
I do a 4.2V pro charger (for my lamps) which runs off an input of 12~24V for cars, HGVs, boats planes and helicopters

 

[tony from suffolk]

So Roy, is is feasible for me to make something up that'll run off 12V? Presumably you need to do more than just step down the voltage?

 

[royfellows]

So Roy, is is feasible for me to make something up that'll run off 12V? Presumably you need to do more than just step down the voltage?

On the face of it you dont need this. I would go for easy solution of Mains adaptor/integrated dedicated 4.2V Li Ion charger with a suitable charging plug grafted on if needed, you never know it may came with one that matches.

This is the kind of thing I mean, for less than ?4 inc post:

http://www.dx.com/p/singfire-uk1-435135-uk-plug-power-adapter-black-3-5-x-1-35mm-117cm-cable-ac-100-240v-252019#.VZ0BwflVhBc

I have tested these and they are OK for protected Li Ion cell packs, I have not tested them on unprotected.

There is a review on there from me.

As an afterthought, I would be very surprised if unsuitable for unprotected as full charge was tested by me at 4.19V and electronic overcharge protection cutoff is a fraction higher than this

 

[tony from suffolk]

Many thanks Roy - duly ordered.

 

[tony from suffolk]

Update - charger received as per Roy's recommendation. It had the wrong size DC plug on the end but handily, Maplin do a very nice box of different-sized plugs, for a fiver.

It works a treat! Thanks for the advice Roy.