Battery for homebrew??

[bikeoutback]

So I've got the homebrew and it works for about 45 minutes or so with my RC car batteries which is not long enough. They are also a pain to charge since my charger runs on DC only (it's all from back when I raced them so never needed AC charger). Therefore what am I looking for as far as batteries, I'm not so inclined to take my chances making battery packs and chargers since I don't think I know enough of what I'm doing and seems like I could waste quite a bit of $$ trying to figure it out along with possibly hurting someone, therefore I was thinking I'd just go the buy route. I've been searching on batteryspace.com but was wondering in general what's my best route and anyone know of any good deals out there currently? Thanks in advance

Nichols

(and after posting this I'll be rereading the homebrew document on batteries, hope the links still work where it's hosted, but advice still would be appreciated, maybe on batteries only in this thread)

[bikeoutback]

Also will be carrying in seat bag or camelbak so not restricted to the water bottle type batteries either.

[JBergland]

I just got a set of these in the mail today.
http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=413

JB

[bigwheel]

I just got a set of these in the mail today.
http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=413

JB

Those look like a decent set of batteries. They will run for about 1:45 or so on a 20-watt bulb. If that's not long enough, you can either go with lower wattage, or bring along an extra set of batteries.

My guess is that your old RC car batteries have had a rough life, and probably don't have nearly their original capacity.

[bikeoutback]

Those look like a decent set of batteries. They will run for about 1:45 or so on a 20-watt bulb. If that's not long enough, you can either go with lower wattage, or bring along an extra set of batteries.

My guess is that your old RC car batteries have had a rough life, and probably don't have nearly their original capacity.

My old RC one's actually performed exaclty as expected being they were 7.2 volt, 1500mAH packs, so 2 in series gave me about 40-45 minutes. Not bad after about 2-3 years of constant running in the RC truck. In any case I was looking at the following:

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=1299

and then picking up a set of the one's linked before in this thread as a second set. Question is am I safe running these one night, cooling them overnight charging them the next day and running them the next night? I'm sure it will lower life expectancy but can I get away with this in the event that I do ride a few days a week. I'm also gonna "upgrade" my homebrew to high/low switch and add a helmet light in addition to the handlebar this year.

Nichols
And Thanks Bob for the write up on those lights, couldnt' have done it without it. Also just a note, the homebrew2 thread had 180 replies!

[dopey048]

Ordered a pair of these for my homebrew, they will see action at the 24 hours of Afton.

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2627

Hope they will last atleast 2 hours each.

[bigwheel]

In any case I was looking at the following:

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=1299

and then picking up a set of the one's linked before in this thread as a second set.

That will work, but why would you not just pick up two sets of the same pack? Also, from what I've read, the quality at all-battery is slightly better than that at batteryspace.

Question is am I safe running these one night, cooling them overnight charging them the next day and running them the next night? I'm sure it will lower life expectancy but can I get away with this in the event that I do ride a few days a week.

Yes, that should be no problem. By the time you get home from a ride, your batteries should be cool enough to drop onto the charger.

I'm also gonna "upgrade" my homebrew to high/low switch and add a helmet light in addition to the handlebar this year.

Cool. It isn't that much more work, and it gives you a lot more versatility for long rides.

And Thanks Bob for the write up on those lights, couldnt' have done it without it. Also just a note, the homebrew2 thread had 180 replies!

You're welcome. Now that summer is half over, the topic of homebrew lights is getting dusted off again.

For the last year or so, a couple of us have been running Li-Ion homebrews, with PIC microprocessors doing real-time voltage regulation. These are way cool, but you are going to have to deal with building circuit boards and stuff that is not for the faint of heart.

When you get something up to your liking, post a picture of your setup.

[mara]

stuff that is not for the faint of heart.

Those of us who are severely faint of heart and absolutely un-electronically inclined are still hoping you will do a tutoring session. Is beer an acceptable form of payment for tutors these days?

[robc]

Hey Bob,
Do you happen to still have the info for that guy we bought the 6Ah li-ions from on Ebay? I'd like to email him and see if he has any more. I lost some of my old emails and don't have his info any more. He had some that were not listed on ebay last year. Those packs were crazy cheap and fit so nice in a camelbak.

Thanks,
Rob

[bigwheel]

Hey Bob,
Do you happen to still have the info for that guy we bought the 6Ah li-ions from on Ebay? I'd like to email him and see if he has any more. I lost some of my old emails and don't have his info any more. He had some that were not listed on ebay last year. Those packs were crazy cheap and fit so nice in a camelbak.

Thanks,
Rob

A while back, I tried emailing the guy about those packs, but he didn't answer any of my emails. I've since lost his address.

I check about once a week, and have never since found anything even close to the deal we got on them. I'm seriously wishing I had bought a bunch more.

Mara, I was trying to come up with some kind of tutorial, but I can't figure out how to pull one off. There are such a variety of electrical skill levels, and some of the stuff (e.g. soldering) requires some practice before you get good at it. Plus, everybody wants a different setup, so there really is no "standard" homebrew light. I am considering getting a few people together, and building a bunch of wiring harnesses, then letting everyone get their own components. No promises, (yet) though.

[MikeMoneymaker]

I say you build a bunch of cheap, but bright ones. then sell em. you'll be rich! :D

[bikeoutback]

The Li Ion route is in the back of my head also, I'll have to check the document about building the soft start circuit. Also I was looking at the two different sets only cause I need the charger but I found the same deal on all battery also with charger so may go that route but who knows, so many decisions and choices.

[Sevadari]

Those of us who are severely faint of heart and absolutely un-electronically inclined are still hoping you will do a tutoring session. Is beer an acceptable form of payment for tutors these days?
Here, here! I'll second that! I too am likewise un-electronically inclined, but am not so faint at heart and am also hoping that Bob will do a tutoring session.


Mara, I was trying to come up with some kind of tutorial, but I can't figure out how to pull one off. There are such a variety of electrical skill levels, and some of the stuff (e.g. soldering) requires some practice before you get good at it. Plus, everybody wants a different setup, so there really is no "standard" homebrew light. I am considering getting a few people together, and building a bunch of wiring harnesses, then letting everyone get their own components. No promises, (yet) though.
Bob, I completely understand what you are saying. However, if you have the patience to deal with us, I'm sure we could find a sufficiently large enough number of similarly "un-electronically inclined" folks that would like to get our hands dirty and be tutored by the master!

To simplify things, perhaps there could be some pre-discussion between yourself and said group about what kind of setup we would go with and everyone either decides they are in or out with that ONE setup.

Not sure if you've already tried this approach previously, but I can bet there are plenty of us that would like something to get us rolling with night riding that doesn't have to be the cadillac model. I've done two night rides so far on borrowed Niterider Storm lights and had a blast. I'm hooked now, but unfortunately don't have the cash flow to shell out for a production light or the technical skills to build my own homebrews.

Please don't feel any undue pressure, but what think ye?

[crux]

Be careful of what you ask for.

Playing with Lithium packs wile they will yeild higher capacity at a significantly light weight have a tendancy when they fail to burst into flames.

Lithium Ion is a decent choice for the $$ but needs to be constantly monitored and if the cell takes an impact discard it. Lithium Polymer is safer but the cost factor is greater. I'm thinking about running one of my 40V packs this season if I can find a lamp that can handle it. Otherwise I have a few 8000mAh packs at 12V to use.

Going to build/modify a lamp for helmet cam use as well once I can figure out how to swith the camcorder to recognize an external video input for this years night rides.

[bigwheel]

I'm thinking about running one of my 40V packs this season if I can find a lamp that can handle it.

They do make 24-volt MR-16 halogen bulbs. Check out bulbs.com.

The problem with anything much more than about 30 volts is that you get shocked when you touch both leads.

Sharp makes a chopper regulator chip that can be used as a precision step-down dc-dc converter, and can handle about 3 amps. They run about 95 percent efficient. They are fairly easy to use. I've built a bunch of stuff using them. Go to digikey, and enter "chopper regulator" in the search window.

[bikeoutback]

I've spent the last couple hours to try and figure this out and I think I'm just not quite getting something... maybe I shouldn't have slept through physics class? Any case I'm trying to buy bulbs and batteries for my homebrew and match them up well. General questions are as follows:

How does wattage of bulb affect battery life and drain, I'm just not quite getting this? will going higher wattage be better, currenlty I'm using a 20 watt.

Beam angle, I currently have the home depot 20 watt, 12 volt, 15 degree bulb on handlebar mount. For handlebar I'm thinking of going to a 30-40 degree bulb and then get say an 8 degree for a helmet homebrew, sound about right?

I'm going to try and run the high/low beam at least on the handlebar and not sure on the helmet, will probably get to the high/low on that too. I was looking at 7.2 volt battery packs, but also see various ranges higher up yet. Would running two 8.4 volt (high beam 16.8) or two 9.6 (19.2) work better yet? I'm assuming at some point I'd just be sacrificing battery time and bulb life if using a 12 volt bulb, but what about a higher volt bulb or not worth it?

And finally I was looking at this bulb: http://www.bulbs.com/products/product_detail.asp?page=products&inventory=11649
which replaces the masterline 35Watt bulb, but they also have a 35watt bulb on the website, is it either or, I guess this is dependent on how the wattage affects the battery life. Currently looking at some 3300 or 3500 mAH 7.2 volt batteries, figure with current set up should get about 1.5 hours. With two sets thinking I could do 2 laps (ha ha ha, me do 2 laps in one night... maybe next year).

Thanks.

[tedsti]

Wattage and battery life -
More watts is brighter but also drains the battery faster. A 20 Watt, 12V bulb uses 20/12 about 1.7 amps. A 35 Watt, 12V bulb uses 35/12 about 2.9 amps. Overvolting will increase you current draw. If you run a 12V bulb at 14.4V your current will increase about 20%. So a 20Watt, 12V bulb run overvolted at 14.4V will use about 1.7*1.2 = 2 Amps. Overvolting more than 20% is pretty hard on bulbs, so your 2 x 7.2 V battery setup is where you want to be.
Now it you have a 3300 mAh (3.3 Ah) battery and you are drawing 2 amps you will get a run time of 3.3/2= 1.65 hours. Now take your calculated run time and take away at least 30% for a margin of safety. This will give you how long of a ride you should plan.

Beam pattern -
helmet - 10 to 15 degree is a good target. 8 can be a little narrow.
Bars - 20-30 degrees.

[bikeoutback]

Wattage and battery life -
More watts is brighter but also drains the battery faster. A 20 Watt, 12V bulb uses 20/12 about 1.7 amps. A 35 Watt, 12V bulb uses 35/12 about 2.9 amps. Overvolting will increase you current draw. If you run a 12V bulb at 14.4V your current will increase about 20%. So a 20Watt, 12V bulb run overvolted at 14.4V will use about 1.7*1.2 = 2 Amps.

I think this is where I was getting confused hopefully I can type this out correctly to make sense:

20 watts / 12v = 1.7 amps. Now when I go to 14.4 volts I take that 1.7*20% to get to 2 amps roughly. Is 12 volts the benchmark for some reason or just because that's what the bulb is rated at? Why not:
20 watts / 14v = 1.3 amps - I knew this was completely wrong by common sense but wasn't sure as to why? Sorry if this all sounds stupid. I guess I shoudl spend less time messing with lights and more time riding with lights.

[tedsti]

The bulb will use 20 watts if you give it 12 V. This is a rating. The same bulb at 14.4 V will use 14.4/12*20=24 watts.

[jkalla]

The bulb will use 20 watts if you give it 12 V. This is a rating. The same bulb at 14.4 V will use 14.4/12*20=24 watts.

Wouldn't 24 watts generated by a 14.4 volt battery draw 1.7 amps, not 2 amps (24 / 14.4 = 1.7 amps)?

[bigwheel]

Using ohms law from High School physics will get you close, but not exact. Light bulbs don't strictly follow ohms law. The more voltage you put into them, the more efficient (higher resistance) they get. Also, the different brands of bulbs vary with resistance.

Here's how you get the ballpark estimate:
Vb = bulb design voltage (i.e. 12 volts)
Va = actual voltage (i.e. 15.5 volts for a 14.4 volt setup without regulation)
Wb = bulb design wattage (i.e. 20 watts)

Then,
Ib = rated current (That's I (eye), even though this font draws a one)
Ib = Wb / Vb
For a 20 watt, 12 volt bulb, Ib = 20 watts / 12 volts = 1.67 amps

Then, to calculate bulb resistance:
Rb = bulb resistance
Rb = Vb / Ib
For our bulb, that means Rb = 12 / 1.67 = 7.2 ohms

When you change voltages, you can sort-of assume that the resistance is constant. (NOTE: As I explained earlier, when the voltage goes up, the bulb resistance tends to drop. I'll ignore this for these rough calculations)

To calculate current draw at a different voltage
Ia = Actual current draw
Ia = Va / Rb
For our bulb, running at 15.5 volts, that means Ia = 15.5 / 7.2 = 2.15 amps
(In reality, a 20 watt Masterline at 15.5 volts draws about 1.9 amps)

So, to get battery life, divide the battery capacity by the current draw:
For a 3600 mAH pack, with a bulb that draws 1.9 amps,
Run Time = 3.6 / 1.9 = 1.89 hours

Batteries:

In reality, battery pack capacity varies with the amount of draw, the temperature, how old they are, etc. Plus some brands of battery tend to lie more about their capacity than others. You will almost never get the full amount of capacity advertised by the manufacturer. From what I've seen, the batteries from batteryspace.com are really bad. Again, you'd better measure it to be sure.

Bulb Life:

As Ted mentioned, overvolting your bulbs gets you a lot more light, because overvolted bulbs are more efficient. However, you will drastically shorten the bulb life. If I remember correctly, a 20% overvolted bulb will only have about 5-10% of its rated life. However, when a Masterline is rated for 5,000 hours, that still leaves a life span of 250-500 hours, which is enough for several rides.

[bigwheel]

Wouldn't 24 watts generated by a 14.4 volt battery draw 1.7 amps, not 2 amps (24 / 14.4 = 1.7 amps)?

No. You need to calculate resistance first, then calculate what the current draw will be at the new voltage.

Ib = 20/12 = 1.67 amps (rated current)
Rb = 12 / 1.67 = 7.2 ohms (rated resistance, which we assume - for estimates - is constant)
Actual current
Ia = 14.4 / 7.2 = 2.0 amps
Actual power used:
P = 14.4 * 2.0 = 28.8 watts

[bikeoutback]

I picked up Two 7.2V 3300mAh High Power NiMH Batteries with A Smart Charger (http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=414) along with 4 more of the batteries, totalling 6 batteries and one charger. Anybody else use this charger at all? It started beeping on my but the light was still indicating charging. I unplugged everything thinking this was probably a warning. Since all battery hasn't responded to my email figured I'd ask here? This was also when I decided to try the batteries and realized that all 6 came charged, is this normal and do they put a full charge on them before sending them? I'm afraid that if I go hit a night ride that I may run out of juice so I may carry the old batteries also, but carring 12 NiMH/NiCd batteries seems like alot of extra stuff to be carring. easy way to discharge the batteries to charge them full again, maybe just hook it up to the homebrew and let it sit, kinda a waste but...? I'm also wondering why the charger didn't stop charging the battery if it thought it was full, or maybe it just kept going till it go too hot then started beeping?

[bigwheel]

I don't have the complete answer, but here are a few tidbits.

First, they probably do charge up the battery as part of their test before shipping. One way to know that a battery is bad is if it charges too fast.

A NiMH battery will lose about 2% per day, just sitting around. So, even if it came fully charged, you should top it off again before a ride.

It is difficult to tell the state of charge of a NiMH battery. Different batteries often have different charge characteristics (peak voltage, etc). So, they can't simply look at voltage to see if it is charged. Instead, the "smart" chargers typically put in a constant current, and monitor the change in voltage. As it turns out. NiMH batteries will actually have a slight drop in voltage when they near full charge. (I don't know why) So, the smart charger looks for the voltage drop, and stop the bulk charge at that point. The really good chargers also monitor time and temperature, but it doesn't look like your charger has any way to know battery temp.

Because of the way smart chargers detect a full battery, they can sometimes get confused when you give them an almost-full battery. I don't know the specifics of your situation, but it wouldn't surprise me if this is what happened.

Personally, I just use the trickle chargers, and use a timer to cut off charge after it has been connected for the proper amount of time. This means that I need to guess as to what is the charge, but I don't have to be exact. Just over-charge it a little bit. With a trickle charger, it won't hurt much to leave the charger on for a little bit longer.

What I would do is on your first ride, bite the bullet and throw the spare set of batteries in your camelback. That'll give you some confidence that your batteries are okay. After that, keep the spares in your car. If something goes wrong, you can limp back and make the switch between laps. Also, carry some kind of emergency spare, such as a mini mag light and a roll of electrical tape to connect it to your handlebars. It won't be great, but it will be enough to let you finish a ride.

[bikeoutback]

Thanks Bob. I thought about a trickle charger but wasn't sure if I wanted to compute cutoff time and all that so went with the smart charger. Got a decen deal on it all, but of course zero instructions on the charger. I just assumed the batteries would be dead, never even tried them just put it one on the charger. I've got 6 of them though, 2 for my bar mount homebrew, 2 for the helmet mount homebrew (yet to try) and 2 spares so I should be alright with that, at least I'll have two lights if one goes out on me. I've also been using the batteries about 30 minutes at a time which I'll continue to do more than likely riding the roads getting used to the clipless pedals and trying to get in bit better shape.

I also picked up a new seat bag two days ago at REI, it's a novaro. I paid more than I wanted ($25) but it fits a spare tube, my 15 in 1 alien tool, patches, spare bulb, tire levers in one pocket with some room to spare. Then has a lower pocket that fits batteries for homebrew perfectly. My $8 Walmart Bell one tore on one side, figured I'd spend for the nicer one that fist a bit more and if it tears use the REI 100% satisfaction garauntee.

[bigwheel]

When you are charging your batteries and not sure what's going on, just grab the battery and feel if it is hot. The quick charge will generate some heat, but if it starts getting hot, you are probably over-charging it. That won't solve the under-charge problem, but at least you won't be hurting the battery.

Also, when you are using it, don't run your bulb down to nothing. When it starts to get pretty dim, shut it down. Otherwise, the weaker cell in the string will end up with a reverse-charge, which damages the battery. You will probably only be missing about 30 seconds of light. This goes for almost anything that runs on battery.

[crux]

Not sure if this has been posted yet, but noticed a 75W MR16 Halogen option from these guys. It would be bright, but how many amp hours would you need for a 2 hour ride? and could you fit that big of a battery in your pack?

http://trailtech.net/store/single_halogen_mr16.html

[bigwheel]

Not sure if this has been posted yet, but noticed a 75W MR16 Halogen option from these guys. It would be bright, but how many amp hours would you need for a 2 hour ride? and could you fit that big of a battery in your pack?

http://trailtech.net/store/single_halogen_mr16.html

I think that's the same company that makes the 30 watt HID that BatterySpace has converted into a bike light.

The problem with 75 watts is that the fixture gets really hot.