Looking for advice for on the go charging of battery packs

HazeElctrc

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I have a light I set up I put together , it can be powered by a 12 to about 16v pack. Problem is I have to make pack with around 12 AHs capacity. I cant think of a way to legit charge it while on cycling trips. Id have to bring my charger and find a wall, But if Im in the woods or rural area its not a very reliable option.

I cant really use a USB power pack like I do with my lesser lights. I could down grade to an 800 lumen or 400 lumen , which is fine but Id feel better if I could hit 1000 lumens with a 3.4v cell. Maybe you could suggest some options.

I am guessing I will just have to leave my 2000 lumen light behind and just settle for the lesser ones. But I wondering if anyone has suggestions or pointers for a build and a way to tune the light. Thanks in Advance .
 

Lynx_Arc

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I'm not really sure what you are realistically wanting as if there is no power source at all either you have to bring along a lot more battery power or downgrade the power usage. The only alternative is to bring along a huge portable solar panel and hope you can charge it in the mid day sun and if you are cycling likely that isn't realistic either. I don't think that using a bike powered generator is an option as it sounds like a huge amount of power is needed likely you won't be able to supply about 200watts of power or so to recharge it. As for a battery pack.... adapt it for a 20v tool battery by incorporating a buck circuit inline with it you can get various sizes of these batteries and chargers for them. I have seen a PD type charger for USB devices I think may be bidirectional.
 

hamhanded

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12 AHr at 12 volts is 144 WHr, that’s a lot of juice. My 37Ahr power bank is about 8”x2”x3”, and I don’t think there’s much extra space anyone could cut away there. You’re looking at a pretty sizable pack for a bike

Can you give some details on how this 12v light is configured?
 

Poppy

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12 AHr at 12 volts is 144 WHr, that’s a lot of juice. My 37Ahr power bank is about 8”x2”x3”, and I don’t think there’s much extra space anyone could cut away there. You’re looking at a pretty sizable pack for a bike

Can you give some details on how this 12v light is configured?
I'd ask the same question, in fact, WHY a 12-16 volt light? Why not use LEDs that'll run on 3-4 volts, within the parameters of LiIon cells?
 

HarryN

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For a trip like that, it might make sense to consider using a roll up solar panel approach. Might need at least 100 watt size panel to be useful as the don't produce what they are rated for.

I have used some panels from a company in the midwest called power film solar to trickle charge my cars since we don't drive nearly as much as we did at one time. They are a "its rugged" company not a "its cheap" company. I would give you a link but IIRC that is frowned upon.

There used to be some small generators that were driven by bike wheels. Maybe there is a way to charge this way.
 
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DIWdiver

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An XHP50B-00-0000- 0D0BJ440E (XHP50.2) configured for 12V should produce 1000 lm at 625 mA. This LED is 4000K, 70 CRI, and currently in stock at a distributor I use often. Vf should be around 11.2V at this current. This is 7W and over 140 lm/W.

With a 4S LiIon Pack, an LDO linear regulator could do this job. 12 A-h/0.625A = 19.2 hours run time. That's an average efficiency of about 80%. You should be able to do better with a switcher. At 90% efficiency I calculate 21.6 hours run time.

Do you need to run this all night for several nights in a row? That's the only reason I can think why I'd want to recharge on the go.

A 4S4P pack with 3000mAh Cells would be about what you are talking about. If it were driving a switching regulator, I would say the average input voltage is 14V, and calculate 14V*12A-h = 168 W-h. 7W at 90% efficiency means 7.8W load on the pack, giving the above stated 21.6 hours.

Because of the lower currents involved, I would consider this a more optimal configuration than trying to run a 3V-ish LED from a 1S16P pack, but that would work too.

Building on what you and others have said, there are several ways to get longer run times.
1. Lower the output.
2. More efficient LEDs. I believe 200lm/W is possible today, giving a 43% increase in run time.
3. Build a bigger battery pack.
4. Have multiple packs - can support personnel carry these to swap out?
5. Recharge your pack.

Since you specifically asked about recharging on the go, let's talk about that.

Your pack is around 168 W-h. This would take about 200 W-h input to recharge from fully depleted (less if not fully depleted). The large difference between 168 and 200 is not because of the battery charge efficiency, which is quite high. It's because of the efficiency of the charger, which isn't likely to be quite as high.

Given the battery life numbers, if you could charge every day you would only need to charge to around 70%.

If you had access to a sufficiently powerful charger, you should be able to do 70% in about an hour. This would take 120-140W. With appropriate preparation, you could get this from a 12V vehicle battery. Just plugging into a DC outlet in a vehicle, you should probably plan on a good bit less than this, and maybe 2 hour charge. With line power, 1-hour charge to 70% is easy.

A 50W solar panel could provide enough power to fully charge in 4 hours, 70% in 2.8 hours. A 20W panel running all day could probably keep the battery charged, but even this is pretty big to carry on a bike. Unless you are talking about many days, more batteries is probably cheaper, smaller, and lighter.

Wheel-powered generators have been mentioned. I haven't looked at these in decades. What I remember from back when was so inefficient that I wouldn't even consider it. If modern versions are available that are well-engineered and well-integrated into the bike, this could be a solution. You'd need up to 20W for 10 hours depending on how much charge your battery needs. But even this small a load, even if pretty efficiently drawn from the wheel, would represent a substantial increase in drag on the bike. I think it would be far easier to carry 5 times the battery than it would be to charge one off the wheel.

In summary, I'd say that the only way I'd consider trying to recharge batteries on the go is if there are no support personnel or vehicles along your route, high light output is needed, and there's a need to run the lamps 50+ hours on your trip. Otherwise, I'd carry sufficient batteries, or swap them out along the way.
 
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