[Gonz]

Hi ... is it possible to power the magic shine light from a 6 VDC NIMH battery pack ? I have several 6 V packs from my niterider set up. (please be nice if this is a dumbass question)

 

[Infinity123]

As far as I remember, the driver will turn off the light around 5 V, so probably not the best combination.

 

[vroom9]

It should work. I would try it on a bench so you can see how long and well it runs. Don't forget a fan for the light.

 

[Turveyd]

You'll get 60% run time before the driver cuts it off I'd guess atleast you'll never over discharge your batterys.

 

[lidarman]

As far as I remember, the driver will turn off the light around 5 V, so probably not the best combination.

I thought the battery was the master here.

I'm curious about this. Does the driver in the lamp turn it off at 5v or the driver in the Li_ion pack turn it off on a normal setup? I was thinking it was the battery pack electronics that turns it off. The pack controlling this makes more sense because it's about protecting the battery, not the lamp. The lamp should be able to regulate below 5 v if the electronics work the way many do in other LED setups.

I hope the OP tests this and reports time and stats. Heck. I have a N.R. 6 v pack. Maybe I will test this myself for fun. If the Li-Ion pack it the limiting factor, the NiMH pack should work well.

I guess the OP is planning on just buying a head, otherwise, I can't see hauling around that heavy pack.

 

[dapedaler]

It should work.

Hi ... is it possible to power the magic shine light from a 6 VDC NIMH battery pack ? I have several 6 V packs from my niterider set up. (please be nice if this is a dumbass question)

I haven't tried it myself because my old nightrider batteries are so much heavier, but it should work. Here is a typical Nimh discharge curve.

This if for a AA 2000mAh cell so the capacities wouldn't apply, but the curve is the same. You can see that the cell holds better than 1v for over 80% of it's capacity. A 6v pack Nightrider pack is made up of 5 sub-C cells so it should hold over 5v for some time if it is still in good shape. The control circuit in the MagicShine cuts off somewhere around 5v. In any case it is safe to try it and see what you get. Just remember, if you are running it on high, it need air moving over it to prevent overheating.

Jim "dapedaler"
Nova Bike Lights
[email protected]

 

[lidarman]

A 6v pack Nightrider pack is made up of 5 sub-C cells so it should hold over 5v for some time if it is still in good shape. The control circuit in the MagicShine cuts off somewhere around 5v. In any case it is safe to try it and see what you get. Just remember, if you are running it on high, it need air moving over it to prevent overheating.

Jim

Where are you getting this "magical" 5 volt number now that we aren't using the Li-Ion pack anymore? I find it hard to believe that the lamp electronics have a 1.3 volt overhead to maintain 1.3 amps (full draw on the MS light).

 

[dapedaler]

I got the 5V number by hooking the light up to a DC power supply and slowly lowering the voltage until the light shut down. The battery pack is protected to not discharge below 4.8V, but the control circuit in the light stops functioning at about the same point. I can recheck my numbers in the lab on Monday, but I think there right.

Jim "dapedaler"
Nova Bike Lights
[email protected]

 

[dapedaler]

The P7 LED draws 2.8A at 3.6V for about 10W at max output. (The MagicShine control circuit actually only supplies 2.4A) The control circuit is about 80% efficient, so the battery must supply about 12W. W=VxA so at 6V the battery draw is 2A. At 5V that goes up to 2.4A. With the 7.4V Li-ion pack it is only 1.6A

 

[MtbMacgyver]

I thought the battery was the master here.

I'm curious about this. Does the driver in the lamp turn it off at 5v or the driver in the Li_ion pack turn it off on a normal setup? I was thinking it was the battery pack electronics that turns it off. The pack controlling this makes more sense because it's about protecting the battery, not the lamp. The lamp should be able to regulate below 5 v if the electronics work the way many do in other LED setups.

I hope the OP tests this and reports time and stats. Heck. I have a N.R. 6 v pack. Maybe I will test this myself for fun. If the Li-Ion pack it the limiting factor, the NiMH pack should work well.

I guess the OP is planning on just buying a head, otherwise, I can't see hauling around that heavy pack.

The driver in the magicshine light head shuts down at a little below 5 volts. The typical cutoff voltage for the protection PCB in 2.5 volt / per cell so it's probably random which one cuts off first. More details in this post.

http://forums.mtbr.com/showpost.php?p=6188937&postcount=2

 

[scouter]

Y not a 7.2v NiMh pack?

 

[Bryank930]

Y not a 7.2v NiMh pack?

I was just about to make a thread asking about a 7.2v NiMh pack. I have a feeling it should work just fine. Unless someone suggests otherwise, I'm going to try it. I'll order just the light head from geoman and grab a 5000 mAh pack from ebay (MS battery is 4400mAh). I'll wait to hear what others have to say before buying everything though.

Seems like it wouldn't be a bad thing to try since, from what I've read, the MS charger is pretty sketchy.

 

[MtbMacgyver]

I was just about to make a thread asking about a 7.2v NiMh pack. I have a feeling it should work just fine. Unless someone suggests otherwise, I'm going to try it. I'll order just the light head from geoman and grab a 5000 mAh pack from ebay (MS battery is 4400mAh). I'll wait to hear what others have to say before buying everything though.

Seems like it wouldn't be a bad thing to try since, from what I've read, the MS charger is pretty sketchy.

You're not going to get a definitive answer since I doubt that configuration has been tested extensively by anyone. Based on the testing I have done, it will function in that voltage range for at least a few minutes, the question that remains in my mind is what happens over the lifetime of the driver. It's clear that the MS driver runs very hot and contains components running way over their specs, so if running at a lower voltage increases the heat dissipation by the driver you will likely run into problems down the road. Generally speaking, a lower input voltage makes a buck driver more efficient and hence less heat. But it will increases the duty cycle for the pass FET, which in some circumstance could generate more heat.

I assume you're talking about a 5000mah nimh pack. In my opinion, the worst li-ion battery and chargers tend to work better than the best nimh packs and chargers. So, I'm not sure of the advantage of this approach. Yes, the battery pack has been the largest source of Magicshine failures, but my observation is those are caused by spotty assembly quality and water getting into the pack. So, as long as you get a pack that was assembled ok (hence why you want a relatively easy warranty path) and you waterproof it if you're going to be riding in wet conditions, the magicshine battery actually seems to work fairly well.

 

[Bryank930]

You're not going to get a definitive answer since I doubt that configuration has been tested extensively by anyone. Based on the testing I have done, it will function in that voltage range for at least a few minutes, the question that remains in my mind is what happens over the lifetime of the driver. It's clear that the MS driver runs very hot and contains components running way over their specs, so if running at a lower voltage increases the heat dissipation by the driver you will likely run into problems down the road. Generally speaking, a lower input voltage makes a buck driver more efficient and hence less heat. But it will increases the duty cycle for the pass FET, which in some circumstance could generate more heat.

I assume you're talking about a 5000mah nimh pack. In my opinion, the worst li-ion battery and chargers tend to work better than the best nimh packs and chargers. So, I'm not sure of the advantage of this approach. Yes, the battery pack has been the largest source of Magicshine failures, but my observation is those are caused by spotty assembly quality and water getting into the pack. So, as long as you get a pack that was assembled ok (hence why you want a relatively easy warranty path) and you waterproof it if you're going to be riding in wet conditions, the magicshine battery actually seems to work fairly well.

Exactly what I wanted to hear. Thanks Macgyver! I'll go with the full magicshine set and just plasti-dip the battery. What are you thoughts on the charger though?

 

[MtbMacgyver]

Exactly what I wanted to hear. Thanks Macgyver! I'll go with the full magicshine set and just plasti-dip the battery. What are you thoughts on the charger though?

I'm not terribly impressed by any of the inexpensive li-ion chargers I've found on the market. Most of the batteryspace and all-battery chargers have been fairly inconsistent in term of the accuracy of their voltage regulation. I've only tested 4 magicshine chargers and they were as good or even a little better than any other low cost charger I've tested in term of the accuracy of the voltage regulation. I haven't torn one apart and analyzed the actual circuit design, but I doubt it would be much different than the design of the driver in the light head. Which means it works, but doesn't follow the best design practices. Which is about what I've seen in all the other low cost chargers.

So I think the key question is what is your alternative? I would be comfortable saying the magicshine charger is as good or possibly better than any other low cost charger you can buy. But if you're going to invest 100ish dollars in a high end charger from the RC industry, then that'll be better.

I do use all the low cost charger / packs in a location where they aren't likely to burn my house down if they burst into flames. Which means on a concrete floor away from stuff that's flammable. But I do admit to being fairly conservative when it comes to battery / charger safety.