Bit of an update on the battery pack.
I received the lipos today and decided to get the battery pack assembled to a servicable/testable state.
I ended up going a slightly different route for the lipo packs, rather than the two Turnigy 5000mah 2s1p 20c softcase packs I chose to get two Turnigy 6000mah 2s2p hardcase packs with a 25c discharge rating.
Turnigy 2s2p 6000mah hardcase
I am actually not too keen on parallel wired cells in preassembled packs because I like being able to see directly how each cell is doing, but in this case it ended up being the best option.
This was mostly down to size and capacity, with the longer but thinner 5000mah packs I could have theoretically fit 4 in there but it would have been too tight to realistically do the wiring without soldering the packs in permanently. With the 6000mah 2s2p packs I have more space for connectors and wiring at the top while also filling up the vertical space fairly efficiently and getting some more capacity in there with less hassle (compared with two 5000mah packs).
The hardcase is also quite nice and means I don’t have to worry about potentially damaging the foil packages of the bare cells when jamming the lid shut. It’s quite a tight squeeze to get things closed up.
Here’s the assembled pack as it currently stands, the two 2s 6000mah lipos connected up in parallel with deans t-connectors.
Above it are the twin relays also hooked up in parallel. They feature 6v coils, with a rating of 12Amps each and are triggered on by the master toggle switch on the outside of the pack.
Still to come is the temperature monitor/alarm and a circuit for automatic low voltage cutoff. Possibly also a short circuit detection, we’ll see.
But for now it’s ready to test.
Another difference to the last time I showed the pack is the much thicker coiled power cord. The 18awg cable I was using before just wasn’t up to the task and at 15A test currents it was wasting a stupid amount of energy through high resistance. This new cord is based on a 14awg copper stranded speaker cable and is performing much much better. The material of this speaker cable wasn’t keen to coil under heating so I had to shrink wrap it first them do the coiling and that worked out really well. It’s quite a stiff coil that likes to return to this position, much more so than my first attempt with the thinner cable.
It also weighs a heck of a lot more, but well… the lipos aren’t exactly light either!
Speaking of which the total weight of the pack is now 1.36kg! Which means you’ll definitely notice its presence on the belt, and also means I need to beef up that belt clip to something more substantial.
Finally a couple more renders showing how I plan to run the switch wiring down the back of the light.
The parts are starting to trickle in now so I can’t wait to start assembling the final thing.
Cheers
Linus