Swap 4v Lead Acid for 18650 3.7 volt in camping lantern?

I have a camping lantern which has a 4v 2ah lead acid battery. The lead acid battery is dead and I have swapped it out for two 18650 batteries in parallel. I maybe should not have done this since I don't know the answer to this question . The cables going to the connection to the battery are putting out 5V's to charge the batteries when they are in the lantern. If the original battery was 4v's, will the 18650's get over charged in the lantern while hooked up to an outlet?

Unless it has a BMS to prevent that, by cutting off discharge, then yes.

You will want to change the charging circuit and charger to one compatible with the new battery. Or don't charge them with the lantern's built in charger, and always remove them to charge them with an 18650 charger.


The SLA would be around 2.4v per cell to charge, so nearly 5v.

The 18650 is probably about 4.2v max (less for some, more for others, but 4.3 would be the max I know of). 5v would be a pretty big overcharge.

Thanks for the reply. Those are the same lines of thought I had. I will stick to charging them with my 18650 balance charger.

You could stick one of these in there

http://www.ebay.com/itm/2PCS-5V-Mic...y-Charging-Board-Charger-Module-/400665522246

Would also give you a 2.5V LVC to avoid over discharge.

Thanks! I just ordered that board.