Modifying battery scheme of an LED torch

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abe94

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I have an LED torch which I would like to modify. I want to use the charging circuit in the torch to charge another battery of the same voltage. The battery in the torch is a smaller 6v 4.5Ah and the one I want to charge is a bigger 6v 8Ah. I soldered two battery tabs at the same point where the original battery of the torch is connected. I've taken the soldered tabs out of the torch case and plan to use it as a battery charger. My only concern is that if the different batteries would work good in parallel and not cause any problems. Also , can i use the 6v 8Ah battery to supply the LEDs ? Or should i just use this configuration for charging ?
 

Hi,

I don't know, sounds a "not recommended" solution, I could be wrong - maybe it works fine. Other members usually give better advice and direct people to something like: "Battery University .com" Best check out that web first to be sure.
 

What type are the batteries? Li-ion seem to get the most news reports as being prone to cause fires or explosions, especially if mishandled.

A charger suitable for one type of battery is not necessarily suited for another type.

Do you plan to connect the battery packs together directly? You must make sure they are exactly the same voltage, because if they are not then one pack will charge the other very quickly, with possible risk of ruining one or more cells.
 

A Lithium-ion cell is 3.2V when almost dead and should have its load disconnected and it is 4.2V when fully charged. It averages 3.7V during a discharge.
I thing a 6V/8Ah battery is a monster, heavy, lead-acid one that was used in flashlights 50 years ago.
 

you can expect big problems upon connection if the SoC is mismatched.
At least use a Polyfuse in between. 1A or less
 
Last edited:

Well I figured out a less fancy solution. Put the original battery with a switch in between. And took two charging leads out of the case. Now I use the leads for charging the 8Ah battery and whenever I need to charge it or use it as the torch's power source , I turn off the switch and take the primary battery out of the circuit. Not quite elegant , but serves my purpose. Thank you everyone for your inputs !
 

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