Peufeu's Electronic Stuff Unfinished projects since 1912

I was powering the helmet light from a pack of 6 Varta NiMH 2700mAH AA batteries, but found the runtime to be too short. Additionally, the low voltage was a problem for the regulator : input current was too high and tripped the overcurrent protection. I would have had to replace the inductor with a larger one to handle the extra current, a hassle I'd rather avoid.

Also, it was a hassle to take the AAs out, put them in the charger, and put them back in the light.
For a while I replaced the AAs with a RC car battery (8.2V 4200mAH) which was a lot more practical, but a bit heavy.

Recently, I could obtain a pair of brand new LiIon 14.4V/4400mAH laptop batteries, which are much lighter than the NiMH and would provide more than enough runtime :

I had the adequate charger for those, perfect.
The connector is not practical for bike use, so I decided to add a Tamiya connector, which is cheap, rugged, reliable, and easy to use.

After heeding the warning :

Let's pop this open. No surprises inside, a series/parallel arrangement of LiIon cells and a protection PCB.

The output connector should be connected AFTER the protection PCB to keep the protection active. Not directly to the batteries themselves !
Therefore I soldered 2 wires to the PCB (small ones to be able to close the battery pack afterwards) ; and then a readymade Tamiya connector plug and wire assembly.

Heat shrink for insulation, and generous amounts of hot melt glue on all sensitive parts for protection against vibrations.

Since the external wires are super-wiggly silicone insulated ones (excellent for this application since no amount of wiggling will ever destroy them), nothing sticks to them except silicone sealant. So, here I apply bathroom-grade transparent silicone sealant in generous amounts to keep the wires well attached to the battery pack.

After this, I applied some elastomer sealant (used for sealing cracks in walls, around windows etc) around the pack, and used some to prevent any movement of the cells inside the pack. Leave to dry 24 hours with lots of weight on it before it is ready :

Tada.

I need to check if I can remove half the cells from the other pack to make a lighter one (I don't need 6 hours runtime all the time...)