Bulbs, batteries, and questions.

[DiscoSnorlax]

I have a pair of bulbs (GE 7613 bulbs, 6 Volt 8 Watt according to the stamp on the back)

I also have a few 12V 2.3Ah SLA batteries I got at Walmart, came with a charger (more on that later) all for $4.50 ea. (on clearance)

I'm considering using these as headlights for my bike (will most likely mount to a large front basket I'm planning to buy.) What's the best way to do this? I'd think I should connect the bulbs in series (so each drops 6V, so they last longer - I'm sure 12V would decrease the lifespan...) Would that be 8W or 16W load? And how long would that run on the 2.3Ah battery?

More about the 'chargers' that came with them The batteries (supposedly meant for 1:6 scale R/C cars). The printing on the battery recommends 14.V7 - 15V constant voltage charge for cycle use, and 13.5V - 13.7V cvc for standby use. The so-called charger appears to be a normal wall-wart labeled as a Class 2 Power Supply and Output: 12VDC 300mA. Is that good, bad, or indifferent? Remember, I'm not too concerned with recharge time, but I do want to make the batteries stay useable as long as possible. Btw, how should I go about charging? I know lead-acid like being kept at full charge, but I'm not sure what the best method is...

Any ideas?

[The_LED_Museum]

I can answer one of your questions about the bulbs...if you place them both in series, I believe that would be an 8-watt load on the battery.But with a series connection, when one burns out, both lamps will go out, and it'll be up to you to determine which bulb went bad.

Hooking the bulbs up in parallel would cause them to instantly burn out; so you really don't want to do that.

[jtr1962]

Speaking from personal experience, you don't want to use incandescent bulbs on a bicycle. You hit a pothole and the filament breaks. I went through enough bulbs then I finally gave up and stopped having lights on my bike altogether until LEDs became bright enough. Also, incandescents have a short life, maybe a few dozen hours, making every ride a crap shoot as to whether or not you'll be left in the dark. If you really must use them then do a series connection as Craig said. This would be a 16 watt load on the battery so figure you'll get at best 1.5 hours run time. Bulbs of this wattage and voltage aren't terribly efficient either. For your 16 watts of power you might be getting 200 lumens if you're lucky but more likely 150. An LED array made up of 65 eBay 26000 mcd LEDs driven at 20 mA each would give 200 lumens while using under 5 watts.

As for charging the battery, SLA are best charged at constant voltage. For a 12V battery this would be 13.8V. For longest life connect the battery to the charger after each ride so as to avoid deep discharges.

[DiscoSnorlax]

Yeah, I figured hooking them in parallel (each dropping 12V) would probably blow them, that's why I suggested in series.

As for brightness, they were originally being used in one of things that lights the hallway when the power goes out, one of the ones here was damaged and they were throwing it out, so I got some parts and stuff off it. I checked the bulbs with a lantern battery, they work fine. They're about the same shape/size as the ones in my old Big Beam flashlight, main difference really is that they have a patterned lens instead of a plain one, in case anyone was curious.

Hmm, 13.8V ... I guess that means I'll have to buy a real recharger instead of the 12V/300mA-output wall-wart ones that came with the batteries... (They claim to be Class 2 Power Supplies, Model Batset-12V according to their labels)

Edit:
Found a picture of the bulb, site says it's PAR-36, not sure what that means actually...
http://www.emergencylight.com/detail.cfm?ID=675

[jtr1962]

PAR=Parabolic Aluminum Reflector and 36 means a 36° beam angle (I think). 36° seems wide for a bike headlight (15° to 20° is ideal) so it'll be lacking in the throw department relative to the power it'll be drawing. After seeing the size of that bulb I'm thinking you'll have another problem not related to the fact that it's incandescent-namely the mounting bracket. You'll need something pretty strong. I remember back in the days when I used dial speedometers on my bike. The brackets used to crack all the time thanks to the jarring from potholes (and the speedo is a lot lighter than those bulbs are). Chances are though that the bulbs will burn out before the bracket cracks.

I understand wanting to use parts you got for free for this project. It just seems to me that they're less than ideal for their intended use. It's lots of fun to play around with these things, although frequently by the time you're done you end up spending more time and money retrofitting than it's worth. I suppose LEDs have problems of their own, the biggest being how fast the technology advances. I'm all set to replace my bike headlight array consisting of 20 8,000 mcd LEDs with 25 or so of the 26,000 mcd LEDs I recently acquired on eBay. I'm resisting the temptation because the current LEDs have plenty of life left, and I'm sure in another year or so I'll be able to get 35,000 mcd or better LEDs.

[DiscoSnorlax]

Yeah, enclosures to mount them in is about the only thing I don't have (or have a free source for yet).

- Bulbs - Got them, free even.
- Batteries - Got those, too. $4.50ea at wal-mart, each with a lame charger.
- Wire and crimp-on fork terminals - I'll 'appropriate' some from one of my PLC classes
- Battery holder - Since I plan to attach a basket, I'll just neeed something relatively water-tight to put it in.
- Enclosures - not sure about those yet. Might get (a) shallow plastic box(es), cut holes in the lid(s) to mount the bulbs, drill holes in the bottom/back, and wire-tie it to the basket with a bunch of ('appropriated') wire-ties. Maybe latch the lid with a couple of them too.

Seal the wire-tie holes and the wire holes with cheap silicone, and I'd be ready to roll. Plus think how cool those'd look on my Huffy Cranbrook. [img]/ubbthreads/images/graemlins/happy14.gif[/img]

[LED-FX]

Quick correction, the number after the PAR is the lamps diameter in 1/8s of an inch.PAR 36 is 4 1/2" diameter.

Adam

[Lynx_Arc]

[ QUOTE ]
The_LED_Museum said:
I can answer one of your questions about the bulbs...if you place them both in series, I believe that would be an 8-watt load on the battery.But with a series connection, when one burns out, both lamps will go out, and it'll be up to you to determine which bulb went bad.

Hooking the bulbs up in parallel would cause them to instantly burn out; so you really don't want to do that.

[/ QUOTE ]
with wattage you have to add so it would be 16 watts total either in series or parallel, as in series the voltage is double and in parallel the amperage is double.

It appears the bulbs are about 1.3 amps and should probably run for I am guessing from 1-1.5 hours before they start dimming too much. I bought one of those batteries/charger combo also at my walmart for $3.00 and am wondering what to do with it. I may use it for working on car electronics or mobile phone recharging. Most bricks (wallwarts) float at higher voltage under no load or less than listed load.