GlowBoy

Longtime rider, but new to these forums, and what a great thread! I've learned a lot already Could you guys critique my planned build?

I'm currently running a TurboCat S25headlight (10W+15W MR11s at 6V) plus the usual assortment of blinkies, LED headlamps, etc., but would like to upgrade to a homebrew system. Having entirely rewired my previous home, I'm quite comfortable working with electrical stuff, though I still definitely want to keep the system as simple as possible while still getting the functionality I'm looking for. After reading the Starlight 78 page, I'm thinking of putting together a 12V system with the following components:

- 20W MR16 high beam (which would be on most of the time), using the Optronics holders. In a living room test, an el-cheapo GE 20W MR16 (that doesn't seem that well made) noticeably outshines my current 25W system, and I expect the Philips energy saver 20W to be substantially brighter.
- Two Night-Sun Xenon strobes, amber front and red rear. 12V version, since they go through batteries pretty fast.
- Luxeon III low beam. Still working on how to make this work, but I have a Princeton Apex headlamp using the same emitter and I'm impressed with the output for situations where I don't need a ton of light.
- NiMH Battery pack in the 4000-4500 mAh range. Although it would be tempting to over-volt to bump up the output of the high beam, I'm thinking of sticking with 12V because a lot of the12V-ready LED products I've seen look like they wouldn't be able to handle the extra voltage.

Looks like with everything on, this system should draw just a hair over 2 amps from the battery, for a theoretical burn time of nearly 2 hours, though I realize actual burn time may be a bit less. My evening commute is only an hour, but I've heard NiMH batteries don't like being drained much harder than that, and if I push them harder I might not end up running my lights optimally. So it seems like a good idea to have a little "extra" battery capacity.

Also, here's an interesting question. After reading about people hooking up horns, cellphone chargers and other 12V car-like accessories to their light batteries, I got to thinking about cars' electrical systems, which hook the negative terminal of the battery to the frame, requiring only 1 wire to be run to each (grounded) component.

So why not do the same thing on a bike? It would be really elegant to run a single wire to each component, with each item's other pole firmly grounded to the bike frame. Anyone tried this? Since my front lights would be attached to the handlebar, I'd be running about 2A of current through my expensive King headset. Would that damage it? Or would I be risking accelerated corrosion by running current through my (steel) frame?

Thoughts?

- Dan

Map tester

I have been using my frame as ground for over 6 months and it seems to work fine. I really like the simplicity of just running the positive lead where you need it. After having a over-complicated setup last year, I have moved to the other end and tried to make mine as simple as possible. My power switch is located on my underseat bag which holds my battery, so I only have one wire running to my front light and one to my rear light setup. So far, it has not let me down. I have an aluminum frame, steel fork, aluminum seatpost and rear rack, and the ground seems to work fine through all of these components.

Old Dirt Hill

Alright, I'm pretty new to this stuff, but am looking for a cheap way to get started. I already have built my lighting system which basically includes a couple of 20w halogen bulbs. Would this battery be good enough to power my lights for a 2 hour/day commute?

https://www.batteryspace.com/index.as...OD&ProdID=2142

LittleBigMan

I would advise you to get a 5 AH SLA battery and recharge it when you get to work. It will support your 40W very well for an hour, but won't last 2 hours. If you want 2 hours straight run-time without recharging, you'll need at least a 7AH SLA battery.

The formula is basically this:

Watts = Volts X Amps or Amps = Watts / Volts

So for every hour ("Amp/hr") of battery power you need, divide the total watts you are using (40 watts) by the voltage (12.)

40 / 12 = 3.33 or 3.3 Amp/hr. So you would need at least a 3.3 AH battery for each hour of run-time you want.

BUT--

There is a problem. The smaller the battery, the less it can carry higher wattages. For example, a battery that supports 20W for an hour might not support 40W for half an hour; it might run for 20 - 25 minutes. So you have to use "overkill" when selecting an SLA battery for your needs.

40W / 12V = 3.3 AH
2 hours X 3.3 AH = 6.6 AH
"Overkill factor" -- minimum of 7 AH (or even more.)

Remember that SLA batteries, while cheap and reliable, don't like to be completely drained. It shortens their life. ALSO--always buy a fuse for safety reasons, even a 12V battery can start a fire. You can get details from your local battery store.

William, if you don't like the idea of such a large battery, and you must have 2 consecutive hours of run-time, you can put separate switches on each of your 20W lights. That way, you can use 20W most of the time, and use the second 20W as a "high-beam" for special needs. Even with a larger battery, two switches will allow you to conserve power as you need to.

Wheels4

Littlebigman, thanks for that formula... i needed it. i'm right on track.

20w with 5ah battery will give me my 2hr run time with no problems. heck, i might even add another 10w light just because i can. then i can switch between them like you suggested.

thanks again.

Old Dirt Hill

Thanks for the information. I would be able to charge the battery at work, so I'd really only need about an hour (or less if I switch the lights seperately, as you mentioned) of 40W runtime. I'm sure there are better ways to make this work, but right now I'm really only looking for a cheap way for me to get setup. Once I get my feet wet and know a little more about what I'm doing, I would plan on buying different (more expensive and better) batteries.

Can this type (SLA) of battery be 'overcharged'? The last thing I want to have to worry about while I'm charging at work is whether or not I left it on the charger too long.

Thanks for all your help.

Old Dirt Hill

Ok, so it looks as though SLA batteries can be overcharged. This can easily be solved by using a common timer...but how do you know how charged the battery really is? How can I tell how long to even set the timer for?

Old Dirt Hill

How do you recharge this system? How often do you recharge it?

SpecialKev

First off, thanks to some of the folks in this thread for so much great info and advice. This is one of the things that makes the Internet great.

I accidently bought a MR16 20w without the front glass. Can I run that on my bike in wet weather? Do you have any suggestions on a cover. I am using the Optronics driving lights housings.


Thanks

Kevin

Oh, and what can I do with the 55w bulbs that came with those lights?

jz19

Unless you have a commute well over an hour replace I would suggest that you make that second bulb a 35W Solux. I like my Solux bulb, very nice white light.

jz19

I would not try it. Just go and buy one with the lense. The Optronics housings work fine under the rain. I tested the black plastic one by leaving them under the rain for 90 minutes without problems. The metal ones should work fine too.

Wheels4

jz, my commute is one way... 22.5miles. it takes me between 1hr30min's and 1hr50min's. if i move up to a 7AH battery, i could go with more watts in the bulbs... but, for now i'll stick with the 20 and maybe add a 10watt in the mix.

thanks for the suggestion though.

by the way.... does anyone know what an H3 bulb is as far as wattage?? i've got some little driving lights that i was going to put on my mini-dune buggy but i'm not putting them on there.

thanks.

DCCommuter

H3 comes in a variety of wattages, but it's mostly used for things like fog lights that are far more powerful than typical bike lights --55 and 100 are common wattages. I seem to recall seeing a 27-watt version, but that's the lowest.

DannoXYZ 

I've got a 10w MR-11 light right now. Don't have a regular commute or anything, so I've been using for afternoon rides where I get caught up after sunset. Probably about 1-1.5 hours a day. I have put a female DC socket at the end of a 12" lead on the battery and a matching plug on the light. I put the same plug on my 12v smart/trickle motorcycle-battery charger. So I just unplug the light from the battery and plug in the motorcycle-charter. This way I can also use the AC/DC brick 12v transformers that's common as well. Recharge about once a week overnight, about 8-hours on the smart-charger.

vrkelley

FREE to a good home

I have 3 [Gone] 12V markers Gone!

Ho Ho ho!

Wheels4

ok, with this in mind... i decided to add another 10W bulb. now i've got a bouble lighting system, 30W total and i can use them together or seperate. the best part is the fact that i can use both for 75% of the time and then just the 20W(which is plenty) for 25% of the time AND still have the over kill factor of .45( 4.55 needed from a 5AH battery). that's some good stuff....

Wheels4

after posting, i decided to go downstairs and take a pic.....(it's obvious i'm procrastinating with my studies)

the first pic is what i started with... the second two pics are what i have now. funny thing is, i haven't even ridden with the lights yet. i'm looking forward to it though.

LittleBigMan

If you have a "smart charger," that is, a charger that knows when the battery is charged and will cut down to a "trickle charge" from full charge, you can leave it plugged in overnight, or all day. A good smart charger will have indicator lights that signal when the battery is charged and is now in "trickle charge" mode.

I forgot to mention another option to cut back on the size of your battery (or increase your run-time, if desired.) There are "energy saver" bulbs available (I use one) that allow you to get more light per watt, much like those bulbs you see for your home that draw 14 watts but put out the equivalent of 60 watts of light. Mine supposedly draws 20W but puts out ~ 35W.

In addition, the focus of the beam can make a lower wattage light seem brighter. You sacrifice some peripheral visibility, but as long as you can see what's in front of you, that's what's important. On the other hand, too wide a beam sacrifices precious visibility where you need it most.

I just about drain my battery on the way to work (one hour,) then I spend the next 7 hours recharging. I will probably go with a 5 AH eventually (like I used to have) because I like having "spare" battery power in case I need it unexpectedly.

ItsJustMe

Some of those energy savers are just overvoltaged. If you run overvoltage, the filament is hotter, and you get more light per watt burned. Tradeoff is shorter bulb life. Energy saver 12v bulbs are probably just made as 10v bulbs.

MR16 bulbs seem pretty durable. I have a ride that goes over 4 miles of bumpy gravel twice a day, and I used the same bulb for a year (still have it, but my primary is now an HID). So the "shorter life" may still last a year, and if you get significantly more light, it's worth it.

LittleBigMan

ItsJustMe, check this bulb out--5,000 hrs.

https://www.bulbs.com/products/produc...ucts&class=840

GlowBoy

Are there any "Energy Saver" MR16s other than the Philips?

Old Dirt Hill

I like your setup here and think I'm going to try to build something comparible for my power source. I think I'm going to go with a 5ah setup, so I'll probably buy these: https://www.batteryspace.com/index.as...OD&ProdID=1158

They're cheap and I think they'll provide plenty of power for my commute if I charge every day at work. A question I have is why you built your power brick to supply 13.2V instead of a flat 12V. Is there something I'm missing here? Should I buy 11 of these batteries so that I can get 13.2V or can I get by with 10? Also, what smart charger do you recommend for this type of setup (assuming I go with the C batteries instead of your D's).

Thanks everyone for all of the great information. I'm learning a ton (and having a great time).

GlowBoy

Another question for the regulars here:

Any reason (other than price) not to go with Li-ion over NiMH? BatterySpace has a sweet deal on a prebuilt 11.1V 7200mAh water bottle battery, 100 bucks including the charger:

https://www.batteryspace.com/index.as...OD&ProdID=2217


It's a little more capacity than I "need", but it's only 20 bucks more than I'd spend on the NiMH battery I "need" plus charger. Plus it has lots more capacity, weighs less, and is less work than making a water bottle battery out of cells or packs myself. Any "gotchas" I should be aware of with Li-ion? Should I add an extra inline fuse between this thing and my lights just to be on the safe side?

DannoXYZ 

If you're driving a 12v halogen at 11.1v, you'll be losing A LOT of light, much more than -9%, probably closer to -15%. Better to run another cell to get 14.8v and use an efficient, nearly-lossless regulator to keep it around 13v. Then you'll get brighter light and longer capacity due to the extra cell and the regulator will provide a longer run-time of a fixed brightness. Rather than super-bright at first that fades faster into a dim 2nd half of the charge.


I got 13.2v so that I can overdrive the halogen light by about 10% and get 20% more light out of it. The charger I use is a Battery Tender that detects full-charge through a voltage-plateau I believe. So it stops at 12v or 13.2v or 13.8v for SLA batteries, varies depending upon what's hooked up. Another source for smart-chargers are the Black & Decker chargers for cordless-drill batteries. Some of the smart-chargers even have an adjustable trigger-point for when they switch from charge to trickle mode.

Old Dirt Hill

So let's say that I use a battery pack similar to the one you setup. Although the Battery Tender looks like a pretty nice (and expensive) charger, could I get by using something like this?:

https://www.batteryspace.com/index.as...OD&ProdID=2051

Sorry for the dumb questions, but I'm pretty new to this stuff. I'll make sure to get some pictures up once this is completed as is looks pretty cool on my bike so far.