I didn't set the thresholds with any particular energy capacity in mind. Instead, I set the "critical" threshold at 10.5V, since I read at https://batteryfaq.org/ that discharging a lead-acid battery below that level is a no-no. Then, I just looked at a voltage-vs-time plot of my light system discharging, and eyeballed the battery voltage that corresponds to "about half an hour until 10.5V" with typical use. This came out near 11.5V, so that's where I set the "low battery" warning threshold.

This is really a great thread. I sure wish I would have run into it a couple of weeks ago, before I started building my own light system. Would have saved some headaches, time and probably a little money too. You folks have done some amazing things with your lights.

Here's what I came up with after stumbling along on my own. The basic design came from one I found at Dan's Workshop ( https://www.dansworkshop.com ) but I deviated on a few things.

It's a dual-light system, two 12v, 20w Malibu lamps mounted in 1-1/2" PVC threaded connectors. The threaded connectors are screwed into PVC end caps, which each contain a toggle switch and wiring. I couldn't come up with an elegant way to mount the two completed PVC units together, so finally ran out of patience and just cut a piece of redwood to fit between them, then used zip ties to hold it all together. I may change that later, depending on how it performs. So far it seems good though.

I had an old, nearly-dead Specialized headlight (one of those little 4-AA ones), so stole its quick release and mounted that to the redwood center piece. There's rubber between the quick release and redwood, and also between the redwood and each PVC unit. I cut up an old automotive water hose for the rubber. Not sure how much that will help with shock, but it seemed like a good idea.

Lamp cord was used as wiring to the battery, which is a 4500mAH NiMH battery pack mounted inside a water bottle. There's also a fuse in the circuit, mounted near the battery. It's been a big problem trying to find a water bottle with a big enough opening to fit the battery pack inside, so I ended up just cutting the bottle in half and doing it that way. I'm not thrilled with it though, and may end up going to a seat bag instead, which seems much simpler.

It went out for its first test ride last night, and wow, is that baby bright! Unfortunately, there are a couple of bugs to be worked out.

First, after burning about 10 minutes, one of the lenses warped. After buying these lamps (from Home Despot) I was disappointed to find that they didn't have lenses, so I had to make some. I cut the bottoms out of a couple of clear water bottles and siliconed them to the PVC, but they turned out to be too wimpy and can't take the heat.

Then, after the lens warped, one of the lamps popped out. There are just three small screws holding each lamp in the PVC, and I think the heat made the PVC pliable enough to allow the edge of the lamp to get past one of the screw heads. Truth is, I was pushing against the unit trying to angle it down a little when the lamp popped out. My plan is to find some thicker plexiglass to use as lenses, and to make them big enough in diameter so they can be screwed to the PVC, thereby holding the lamps in too.

The battery pack and a smart charger came from batteryspace.com. I didn't want the extra weight of an SLA battery so decided that, for me, the extra expense for NiMH was worth it. The battery (10 C cells) is light enough to hold between my thumb and index finger without much effort (maybe a pound and a half?). It was about $31, the charger was $35. Those were my biggest expenses.

I can't say enough about batteryspace.com. I ordered on a Sunday evening, and they had it at my door by Tuesday. They also have a nice forum on their site which I found to be a really good resource for technical info.

I'm pretty much a know-nothing when it comes to electronics, but lately I do find it interesting, and this experience has taught me a lot more than I knew previously.

Drat. I found what I thought to be the perfect solution for my lens problem in the hardware store tonight. A couple of clear plastic thingys that go under table legs to protect carpet. They were the perfect size, appeared sturdy enough, and at 69-cents each, fit the budget.

But alas, the hot breath of my twin 20w Malibus brought them to their proverbial knees. After 15 minutes they became soft and squishy, and what's worse, so did the PVC! I think I need to go back to the drawing board. Hmmmmm......

The good news is I got an hour and 15 minutes burn time with both lamps on, which is more than I need for my one-hour commute. Now if I can just keep the thing from going Chernobyl.

I have posted this before and will probably post it again. Optronics Competition Driving Lights, models QH-7CC and QH-8CC make just about perfect bike headlights. They are small, light, cheap (about $17/pair), easy to mount, and use easily available MR16 halogen bulbs. The come with a 50W bulb, but a new bulb of your choice only costs $3-10. I have never found them in an auto parts store, but Optronics will sell them to you. I prefer the black plastic model (QH-8CC) because it looks right at home on a bike, but the chrome metal QH-7CC is fine, too, if you want something a little retro looking. Either looks better than most of the Malibu lights I have seen.

https://www.optronicsinc.com/competition.htm

FWIW,
Raymond

Yes siree Mr. RainmanP sir, I saw your original post regarding the Optronics lights and, truth be told, if I were embarking on this journey now I would likely go that route. But since my contraption was already put together by the time I found this thread.....well....

My lamps are MR11s. Since I've already got them, I think I'll go ahead and try to use them.

Hmmmmm, this commuter mug here could be retrofitted to house an MR11 with a switch in the snap-off-cap......hmmmmmmm....

I’m in debt to you Raymond. They are perfect. I love having two independent housings to adjust as needs dictate.

Problem is not buying a light, it's buying the F#$(* batteries.

Pictures...we need your pictures!

Well the *low battery* warning would have been great on tonight's rainy return commute. On a fresh battery, I can usually make the round trip. But there were some errands to run also, so I found myself "rationing" in well lit areas so there'd be enough juice for the dark ascents.

Pictures coming soon....

Ok, so I lied about my lights. They are MR16s after all. I read somewhere online that the 16 stands for eighths of an inch of the diameter of the lamp at it's biggest circumference. Sixteen eighths = two inches and I knew my lamp wasn't that big. It's more like an inch and 3/8s = 11/8 = MR11 according to that definition. But then I was back in Home Despot today and was able to take a look at the lights again (with packaging indicating the size), and low and behold, they are MR16s. So I guess that definition I found was erroneous.

ANYWAY, now that I know I have MR16s, I'm going to go ahead and order the Optronics Competition Driving Lights (thanks RainmanP).

Dang! I lied again. Ended up going with the Home Despot landscape lights so I wouldn't have to wait for the Optronics set to be shipped. Since the price was comparable and they included 20w lamps, I figured, why wait? So I was able to finish my light yesterday and ride in today!! Yippee!!

Of course I didn't really use it yet. It wasn't dark on the way in....but going home will be the true test.

Bumping this thread up to help others wanting to build their own lighting systems.

I'm in the process of making a web page about my bike light project, but until that's done, here's a few pictures of the finished product. It was completed last Sunday so I was able to ride in to work 4 days this week! It's working great, no problem with burn time whatsoever. I even rode one day with 40watts burning all the way home and it wasn't dimming at all when I got there.

One minor problem with the lens popping off over some bumps but luckily I was able to recover the pieces (lens, rubber seal and housing) and put it back together. Nothing that a little electrical tape won't fix.

Attached are the front and rear views, the NiMH battery pack, and the $6 Wally World seat bag that the battery fits perfectly inside of.

Drool...12V That battery looks so light. How much does it weigh? And where did you get it?

Wow - looks great!

simplygib, is that a piece of 2x4 wood painted black as part of your light/switch mounting bracket? Eager readers would like to know more!

I'm not exactly sure of the weight, but my best guess is maybe a pound and a half?? I can hold it between my thumb and index finger without much effort and I really don't notice the weight of it at all when riding. I got it at https://www.batteryspace.com for $31, and to not kill it by overcharging with a cheap charger, I also got a smart charger from the same place for $35. I'm really happy with it so far, and it recharges in about 3 hours. EDIT: Looks like the battery price is now $32.95. And they list it as 2.2 pounds, but it feels lighter to me. It is here: https://www.batteryspace.com/index.as...ROD&ProdID=432

Becca - thanks!

Map Tester - you have keen eyes. Yes that is a piece of redwood 2x4 that I cut down and hollowed out. I kind of like my homemade projects to have a "Clampett" aspect to them and that fit the bill. :-)
Actually a metal box probably would have been better but I didn't have anything onhand to tweak so opted for the redwood. To hollow it out I started by drilling several 1" holes, then used hand chisels the rest of the way. I don't have a regular woodshop so had to improvise. That's ok - I like improvisation. :-)

The back part of the 2x4 is open so the wires can connect inside there, then I used a spare computer drive bay cover I had laying around to make the cover that also holds the two switches. I cut it down a little to fit, then just painted everything black.

Proud to see it. Mine was almost exactly the same--two modified 20W Malibu landscape lights from Home Depot and a 4.5 AH SLA battery. Should give you about an hour of run time with both lights on continuously.

Right now, I'm running just one of those lights with a 2.3 AH SLA battery, and a 0.2 AH amber xenon rear flasher. I get just over an hour run time.

Take a look at those "energy saver" MR16's at bulbs.com. Mine puts out the equivalent of 35W with only a 20W draw.

Next time, I'll consider spending the extra cash on a new charger just so I can get a 4.5 AH battery as light as yours.

NEXT TIME? Sounds like Santa might need fill that stocking with some new light bulbs --instead of coal this year

My first test got about an hour and 15 but that was inside at 70 degrees. When I ride home it's not terribly cold but it does get down to maybe 45 or so. Not sure if that will have an effect or not. Just in case, I wrapped the battery in cotton for insulation and taped it up.

I remember reading earlier in this thread about those "energy saver" MR16's (yes, I actually did read this ENTIRE thread, pant, pant, pant...). They sound great. Next time I need a bulb I'll remember those.

Just out of curiosity, how much does your SLA battery weigh? At 2.3 amp hours I'd guess it's also pretty light? And if you remember, how much did the 4.5 amp hour one weigh?

My 7Ahr SLA battery weighs 5.85 lbs. Being a clydesdale, that is only 2.4375% of my body weight (lets not talk about the stuff in the panniers!). I have been running by 25w halogen floodlight (from Home Depot), rear amber strobe, and rear beehive LED taillight full time both commutes (about 3 hours total) with probably at least one more commute time to spare. I know it seems like a lot of weight, but is nice knowing I don't have to worry about running out of juice. I just ordered (for two other bikes-my 2nd backup commuter and my son's new bike) a couple of 5 Ahr SLA from zbattery at 4 lbs each. Going to try the seat bag route to store the battery to streamline the build this time.

Not sure about either, never weighed them. But I know the 2.3 is much lighter than the 4.5, and your 4.5
(what was it, NiMH?) is much lighter than my 4.5 was. I went with SLA because they're cheap, but yours seemed like an amazing bargain. I was quoted $150 for a NiCd setup for my 12V!

Oooh, check this out. This might work, and cheap!

https://www.batteryspace.com/index.as...ROD&ProdID=816

I got one of those and one of the cells blew while I was using my laptop on a coffee shop. :/ It had me ****ting my pants for a minute.
I'm waiting for the RMA replacement, but my confidence is a bit shot after that unpleasant experience. Apparently they didn't match
the cells too well and one of them got very unhappy. I think I will use the replacement strictly for bench testing projects.

Wow a defective battery Yeah, just a reminder for anyone else who's considering geek-lights. You might want to use some extra caution when handling the smaller batteries. They look harmless but *interesting* zaps and "episodes" happen.