I killed a battery the other day. It got immersed in water. As did the rest of the bike – and me – when I rode into the canal on the way back from the pub on a night ride 😳

I’ve ordered a replacement so I took the old one apart to see what was wrong. It’s got 4 18650 cells and a tiny circuit board which I guess is a protection circuit.

Each of the cells is pumping out a good 3.7ish volts but together it’s only giving out somewhere between 10 and 13 volts, with a weird pulsing so the meter is going up and down like a mad thing. So I guess it’s the circuit that doesn’t like the water.

I’ve snipped out all the connectors to the circuit board and connected the lead to the pos & neg at the end of the cluster so I’ve now got 4 18650 cells in series kicking out about 15 volts.

What is the risk of attaching this to my Lumicycle LED3 light (it’s supposed to be OK up to 17v and has some thermal overload protection) and my charger? I’m only planning to use it as a spare once the new one arrives.

The cells are Samsung SDI, ICR18650-26A

Proably not worth it, lithium cells are very sensitive to over charging and catch fire in a big old way if they get over charged.

Hmm yes, hadn’t thought the protection might be on the charging side. I’ll rig up an outside charging point then.

I’d buy a replacement protection circuit, or not use them. Li-Ion are sensitive to over-charging, over-discharging and over-current, with the potential to catch fire as a result of any of the above.

I use these
http://www.dx.com/p/genuine-panasonic-18650-3100mah-rechargeable-battery-grey-pair-121452#.VHrjPTGsWSo
and charge them with this
http://www.amazon.co.uk/Nitecore-Intellicharge-i2-Microprocessor-Intelligent/dp/B00EPO1S12/ref=sr_1_1?ie=UTF8&qid=1417339833&sr=8-1&keywords=18650+battery+charger
The two batteries last longer than the 4 cell battery pack that came with my light. I get about 4 and half hours on full. The only problem, if you see it as a problem, they take about 5 hours to charge.
You’ll also need something to hold them.
I’ve not had any issues and have been using them now since september.

Personally I’d remove the protection circuit and connect the battery directly to the last, then I’d fut a balance lead. You can then charge it with a lithium balance charger.

I made my own battery for my lumicycle led in this way. My charger is a radio controlled car mulitcharger by the way (core rc)

A charger would be about 20 quid though.

Edit, have you asked lumicycle how much a repair would be? (Assuming its thier battery)