Looking for something like this
http://www.ebay.co.uk/itm/Bicycle-Bike-Cycling-Red-Laser-Beam-5-LED-Safety-Rear-Lights-Tail-Lamp-Battery-/151216507938?pt=UK_SportGoods_CyclAcces_RL&hash=item233534cc22

BUT all rear cycle lights seem to use AAA not AA. As AA have 3 times more power than AAA AND most shops are selling at the same or similar price they are poor value for money (AAA). I also note that with the lasers on the sellers claim only 9 hours output. As disposable lose voltage quickly I would assume that actual brightness may be insufficient before the 9 hours. My options are:-
1/ Lithium disposables, expensive.
2/ Rechargeable AAA dodgy as rechargeables lose there power quickly with no warning and I would have to remember to charge them. My memory is not my strong point!
3/ Lights that take AA rather than AAA and use Alkaline. At least with this option I should have adequate warning that the batteries need replacing.
4/ Any other options I have not thought of?

Presuming light is centrally mounted on seat post – do you have a saddle bag? Remote battery pack in saddle bag. if you did 4AAs (two series, two parallele) then you could have 5+ amp hour capacity. (5 times AAA)

If you are brave you could see if 3.6v is acceptible for a supply voltage, if so then you could get a couple of 18650 cells for 3.6v 5ah capacity.

Doh1Nut – Member
Presuming light is centrally mounted on seat post – do you have a saddle bag? Remote battery pack in saddle bag. if you did 4AAs (two series, two parallele) then you could have 5+ amp hour capacity. (5 times AAA)

If you are brave you could see if 3.6v is acceptible for a supply voltage, if so then you could get a couple of 18650 cells for 3.6v 5ah capacity.

I may have a seat post bag. But have I got this right you are saying rewire the light? I must admit I like the idea but lack the knowledge for the wiring and would worry about water ingress. I would have no problem with 3.6 volt as I believe 1.5 volts is an average for AA peak would be higher.

I’d be surprised if that e-bay light lasted as long as the batteries to be honest!

Yes, it would require some faffing but as a proof of concept I would go to maplins or wherever and get a 2*AA battery holder. run the wires from that to the battery terminals inside the light.
Once you are happy that it works, you can start making it more permenant, drill a hole in the light for the wire to go through and seal it with silicone.
Get a 4*AA battery holder and switch round the wiring to get the correct voltage and increase your run time.
Get some connectors JST so you can remove the light.
etc.

.piedi di formaggio – Member
I’d be surprised if that e-bay light lasted as long as the batteries to be honest!

I have had some surprising good lights direct from China none have ever failed. All that ceased working were due to me breaking them. In fact they are all still working. I have either broken the attachment or broken the cover. Obviously i can’t say that about everything I buy from Ebay that comes direct from China.