How do i increase run time?

[fuzzynavel]

I currently have an old set of Halogen headlamps with 2 x 10watt GH24 (6V,1.7Amp) bulbs
I think the model may be "Smart BL-201 (HB)" but I can't be sure.

Currently I have a top tube mounted 6V 4.5Ah rechargeable lead acid battery made by Yuasa Model "NP4-6"...

At the moment I only get 2.0 hours running on a single bulb before dimming is noticable...If I try running on 2 bulbs then I am cut down to about 30 minutes before I get noticeable dimming and I am better of running one bulb as it seems brighter...

when I am at full power I can ride pretty fast and not get scared but the run time worries me.

What can I do to increase the run time? Increase voltage? Increase from 4.5Ah to 9Ah?

I have no idea about this power stuff so links for further reading may be helpful..


thanks for any help in advance.

 

[Moonshadow]

Well you need to increase the capacity of your energy supply and/or reduce the rate at which it is consumed.

If you want to keep the same brightness, your options are a larger battery or more efficient emitters. If you are stuck with those bulbs, then that leaves a larger battery.

 

[glockboy]

Increase from 4.5Ah to 9Ah.

 

[qwertyydude]

Sounds like your batteries are beginning to go. If you double the power and get significantly less than half the run time then that means the batteries aren't able to output enough current and are drooping under the load. Lead acid batteries don't like being put under significant discharge, if you wait til you notice dimming you've already done some damage to them, doing so multiple times the damage will accumulate.

I think the best bet is to get yourself an MC-E powered light that can take 2 cells a couple D-cell lithium ions and make a pack. This will be a compatible voltage and significantly lighter package. With just one MC-E you should be outputting more than 20 watts worth of halogen, in fact my MC-E flashlight is as bright as a car headlight. Runtime should be comparable to what you have now or if you want tons of runtime and no li-ion hassle direct drive it on 3 D-Cell nimh and you should get about 3-4 hours of runtime.

 

[yellow]

lead-acid (any lead batt) is perfect for very short, high drain applications - like car engine starters - and they are cheap, but very very very unuseful for constant drain flashlight applications.

imho 2 hours for 10W/6V bulb from a 4.5 Ah battery is next to like-new, that does not show anything gone bad.

Switch to a larger battery, if possible to a better chemistry (= better suited for lights)

 

[fuzzynavel]

Thanks all for your comments.

I can get a 9 Ah battery which is about the same size as the one I have..

What sort of chemistry is best for this application? Alkaline/Lead acid/Nimh...other??

Anybody got any links to sites where I can get a guide on making battery packs? I have loads of 2900mAh rechargeables around....

Moonshadow.....I think I am stuck with the GH24's unless I spend some cash....the lights are plastic and wouldn't be able to get rid of much heat from other light sources.

 

[Jayls5]

Essentially, by wiring another battery in parallel, you double your time. positive terminals between batteries should be connected, and negative terminals between batteries should all connect. You can pretty much figure this stuff out by playing with Ohm's law. Select a viable power source, and if one is insufficient, wire in parallel more batteries of the same type and it will proportionately increase your run time.

 

[fuzzynavel]

Essentially, by wiring another battery in parallel, you double your time. positive terminals between batteries should be connected, and negative terminals between batteries should all connect. You can pretty much figure this stuff out by playing with Ohm's law. Select a viable power source, and if one is insufficient, wire in parallel more batteries of the same type and it will proportionately increase your run time.

Ohms Law??? I am but a humble Chemistry Graduate....will ask the wife...she's a physics teacher

Once I have all of these batteries connected....how do I regulate voltage etc to make sure that I don't destroy my lights?

 

[xenonk]

Different chemistry requires different charging methods, so you would be investing in a new charger as well as a new battery. NiMH is great, though. A series pack containing five D cells would provide around 10Ah@6V (full charge peak would be ~7V, but GH24 bulbs can withstand that).

6V battery/charger kits are sold all over the place. On the down side the charger/battery would probably cost more than the whole system you have now.