Lead acid battery - can I replace with something smaller?

[eldudino]

I've got a Cateye HL-RC220 that has a 6v 5ah sealed lead acid battery to power it. I've always found I get enough light from it but I wouldn't mind a better battery - one that doesn't weigh a kilo and that is a LOT smaller. A guy at work said I could replace it with a Lithium battery, would this work?

I know there are some electrical genius' on here so a bit of direction would be appreciated!

 

[Twenty Inch]

Off the top of my head - you can, but charging it may be a problem.

 

[Davidc]

You can run the light from any battery which provides 6v nominal at the current required.

BUT

you need to connect it safely and reliably to the light

AND

you need a charger. For Lithiun Ion or Polymer you usually need the correct charger for the specific battery.

if you used NiMH (nickel metal hydride) they're lighter than lead acid, but still need a suitable charger

A 6v lead Acid battery starts at around 6.5 to 7v fully charged, lithium about 7.5v, and NiMH 6 cells at around 7.5v. They're close enough that you probably wouldn't have much of a compatibility problem with any of them.

 

[eldudino]

Cheers for that. I'm sort of half tempted just to buy a decent charger for my SLA and figure out a better way of attaching it to the bike. At the moment it's in a bag just behind the steerer but I'm thinking about rigging something up that sits it up in front of the steerer. Something like a bottle cage attached to the head tube would do. I'm just unsure. I see new lights with their tiny battery packs and think how much nicer they look. I've really not got much of a reason to change other than aesthetics!

 

[Davidc]

The only issue I'd have is that that design has to be nearly 10 years old. I'm sure it's the one I looked at but didn't get in 2001. I suspect that you can get more light from a modern LED unit, which will run for longer from a battery, and won't have lamp life issues.

It's a good light, and as long as the battery stays in good condition it makes sense to keep it, but is it really worth the trouble and cost of buying a new battery, the charger that goes with that, and doing the modifications to use and charge the new battery?

If it were mine I'd put the money aside ready to put it towards a new light using current technology when that one wears out.

Edit: have you thought of mounting the battery in a bottle on the underside of the down tube (if you have the fixings)?

 

[eldudino]

It's a good light, and as long as the battery stays in good condition it makes sense to keep it, but is it really worth the trouble and cost of buying a new battery, the charger that goes with that, and doing the modifications to use and charge the new battery?

If it were mine I'd put the money aside ready to put it towards a new light using current technology when that one wears out.

Exactly my thoughts. It's not really worth spending all that much money on. The SLA battery is new and I'm going to get a smart charger for it as everything I've read says the original chargers are rubbish which I agree with after using it for 3 years. Cash is tight due to our 10 month old daughter so I'll see if I can get another winter out of it then replace with something modern next year when finances allow.

I'm gonna have a look at mounting possibilities, I used to use a second bottle cage but I went to mount it again the other day and the bolts have seized and the threaded inserts in the frame are now spinning round, the weld on the other side must have weakened and sheared.

 

[jimboalee]

You can run the light from any battery which provides 6v nominal at the current required.

BUT

you need to connect it safely and reliably to the light

AND

you need a charger. For Lithiun Ion or Polymer you usually need the correct charger for the specific battery.

if you used NiMH (nickel metal hydride) they're lighter than lead acid, but still need a suitable charger

A 6v lead Acid battery starts at around 6.5 to 7v fully charged, lithium about 7.5v, and NiMH 6 cells at around 7.5v. They're close enough that you probably wouldn't have much of a compatibility problem with any of them.

I swapped a PbA 6V cell for 6 NiMh cells.
1.4 V fully charged = 8.4 V and it popped the bloody bulb.

I dropped it to 5 cells. 5 x 1.4 V = 7 & 5 x 1.2 V nominal was 6 V.

I bought 10 cells and made 2 interchangable battery packs.
1 in use and 1 on 1.25 A charge for 24 hours.

OK, so too much faffing so I bought a Tesco torch.

 

[Davidc]

I swapped a PbA 6V cell for 6 NiMh cells.
1.4 V fully charged = 8.4 V and it popped the bloody bulb.

I dropped it to 5 cells. 5 x 1.4 V = 7 & 5 x 1.2 V nominal was 6 V.

I bought 10 cells and made 2 interchangable battery packs.
1 in use and 1 on 1.25 A charge for 24 hours.

OK, so too much faffing so I bought a Tesco torch.

I've had trouble in the past using freshly charged NiMH cells. They'll drop to 1.2v per cell in a few hours, but start off even higher than your 1.4v per cell. A high power (5w) 7.5v zener with a low value (1R) resistor in series in the lamp on the battery side of the switch deals with it.

I really don't think it's worth the trouble doing much with halogen lights, especially if it costs money. Like you I think the future's LED.

 

[gbb]

It's like everything in life, you get what you pay for. The trouble is, to get a decent battery bloomin costs
Just got an Enix 7.5v Lithium battery for forthcoming projects...£20 ish
Charger for the above...about £30.
Thats where the cost of decent lights goes.

TBF, you can pick up a 6v Lead acid battery for far less than a tenner.

 

[andrew_s]

I'd be inclined to get 4 x 18650 lithium cells from dealextreme or someone, and run them as 2P2S (2 parallel pairs of series cells) to give 5Ah at about 7.4V. Most of the chargers are for 2 individual cells, so you'd need some sort of case (rather than solder and shrink-wrap) in order to separate them for charging.

However, I'd probably go for a replacement Magicshine bike light instead. £50 (ish) + VAT/import duty etc (perhaps), 4.5h of runtime on low power, which will be twice as bright as what you are currently using.

 

[02GF74]

I've had trouble in the past using freshly charged NiMH cells. They'll drop to 1.2v per cell in a few hours, but start off even higher than your 1.4v per cell. A high power (5w) 7.5v zener with a low value (1R) resistor in series in the lamp on the battery side of the switch deals with it.

I really don't think it's worth the trouble doing much with halogen lights, especially if it costs money. Like you I think the future's LED.

yep - NiMH don't keep their charge too well, especially the cheap ones.

LED would use a constant current driver so are less bothered by the supply voiltage; as long as the voltage is 2 V abot the LED Vf, typically 3.5 V, you'll be ok; i.e. your battery voltage can be 5.5 V to 12 V or more and LED will not blow due to the driver.

LEDs are the future fir sure.

 

[jimboalee]

Found this on the web.

http://www.trailtechproducts.co.uk/acatalog/MR16_Eclipse_Mountain_Bike_Light.htmlhttp://www.hidtechnologies.com.au/trailtech30w.php


thoughts?