Lithium AA batteries for bike light backup

[Offroad'Bent]

Here's a question. I've done several multi-day adventure races where there is no chance to recharge batteries. I made up some packs of 8 disposable lithium AAs, which run my Nightlightning nicely, once my 7.2V lithium battery pack and spare 6v NiMHs are done.

I wired the AA battery holders to have 2 sets of 4 Lithium AAs in parallel, to give 6-7v. I also had to upgrade the thin little wires on the standard battery holders I found.

After reading some threads here, and given that my light has a Maxflex driver, it looks like it might be more efficient to run the batteries in series, with 12v output.

Does this make sense? If so, anyone have a nice battery holder for 8AAs with decent wiring?

Thanks in advance.

 

[herulach]

that depends primarily on the Vf of the LEDs in your light - maxflex will be more efficient at higher voltage - but it has to be lower than the Vf of your LEDs

 

[Offroad'Bent]

Right now it's 3 Seoul P4s. I think the Vf would be 14v but not sure.

I'm hoping to update to 3 Cree R2s eventually.

 

[herulach]

At most it will be 11.1V (3*3.7), so you'll either want to keep it in parallel or or wire it 6 in a line

 

[Calina]

Use a dynamo and you can forget about charging or discharging batteries.

 

[Offroad'Bent]

Use a dynamo and you can forget about charging or discharging batteries.

Nice idea, but it won't help us when pushing through swamps or thick forests, carrying bikes up cliffs, crossing ziplines over waterfalls with the bike, fixing injured bikes or teammates, not to mention extra drag and weight. How much do dynamos like full submersion in wheel-deep swamps? We do all this stuff during adventure races.

Anyone have a good 6AA-in-series battery holder that can handle current efficiently?

 

[herulach]

Is there a specific reason you don't use rechargeables? How about welding up a 6 cell pack out of eneloops? Capacity should be as good if not better than Lithium AAs, and for for or 5 days you really don't need to worry about self discharge too much. Even if you need a new charger I would imagine it'd pay for itself after a couple of uses lithium primaries areexpensive.

Most places will do a 6 in a line holder, which will have minimal resistance & wouldbe easy to augment the crossover leads at the end. Somethinglike JG78 here. How long do you need the light for? what about 3 sets of 2 14500s?

 

[pyro]

Rechargeables (especially the eneloops) have far less capacity than the lithium primaries.
IMO eneloops don't make sense at all in this application.

If rechargeable is preferred then I'd look for a 18650 based pack.

 

[herulach]

Rechargeables (especially the eneloops) have far less capacity than the lithium primaries.
IMO eneloops don't make sense at all in this application.

If rechargeable is preferred then I'd look for a 18650 based pack.

They do indeed have lower capacity - but they have the advantage of being able to be made into a pack permenantly - and If they're as a back up for racing, difference in run time will be what 5/10 minutes at a 1.3A+ draw? I agree lithiums make more sense - but as the OP is using these as a backup for a li-on pack, I assume theres a reason he's ruled a second oneout.

 

[Offroad'Bent]

Is there a specific reason you don't use rechargeables? How about welding up a 6 cell pack out of eneloops? Capacity should be as good if not better than Lithium AAs, and for for or 5 days you really don't need to worry about self discharge too much. Even if you need a new charger I would imagine it'd pay for itself after a couple of uses lithium primaries areexpensive.

Most places will do a 6 in a line holder, which will have minimal resistance & wouldbe easy to augment the crossover leads at the end. Somethinglike JG78 here. How long do you need the light for? what about 3 sets of 2 14500s?

I don't use rechargeables for this application because I use my rechargeable battery packs where possible for the first couple of nights, but I need good power-to-weight for the longer term races, and the lithium primaries have the Eneloops beat there. We might need up to 10 nights worth of power with no recharge.
I use Eneloops all the time for my shorter burn applications in my modded Apex.

The holder you linked would be nice for what I'm looking for. Thanks!