Summer Camp

[ergo46]

Hello, I work for 7 weeks at a BSA Summer Camp during the Summer. We have power in a cabin that we use to charge our phones but in our tents we don't. I would like to use a small solar panel on the side of my tent to charge a battery ( I think it will be a 12v ). From the battery I would need to charge this flashlight . But I also would like to power a small lamp for 10 minutes at the most. What products should I buy to make this happen?

[inetdog]

Hello, I work for 7 weeks at a BSA Summer Camp during the Summer. We have power in a cabin that we use to charge our phones but in our tents we don't. I would like to use a small solar panel on the side of my tent to charge a battery ( I think it will be a 12v ). From the battery I would need to charge this flashlight . But I also would like to power a small lamp for 10 minutes at the most. What products should I buy to make this happen?

Nice looking flashlight. (I am partial to Olight myself.) Streamlight offers a nice variety of charging options for this model.

1. The instructions do not mention the size/capacity of the battery pack that the light uses, so I am relying on the 12 volt charger adapter information: 12 hours at .2 amps to fully recharge.
The 12 volt cord may be as simple as a cigarette lighter plug to USB adapter, or it may have voltage reduction built in, but in either case all that it does is supply power to one of the usb-plugin chargers.

2. To fully charge one battery pack will take 2.4 amp hours from the 12 volt battery using the standard charger over 12 hours. The fast charger will take between 2.0 and 2.8 AH, spread over a four hour period.

3. A small but bright lamp (LED, of course) could take as much as .5 amp at 12 volts, so for ten minutes that would less than .1 AH.

4. To be able to discharge 2.5 AH over the course of one night, without discharging more than 20% would require a 10-15 AH battery. For portability you would want that to be an AGM type lead acid battery or maybe something exotic like LiFePO4. The lowest cost battery for good life would be AGM, possibly of a type used for alarms, fence chargers, etc. Try to avoid a GEL battery.

5. To replace the 2.5 AH, you should plan on putting 3AH back. Assuming that the number of effective solar hours (not the daylight hours, since the panel will not be doing much most of those hours) is 3, you will need at least a 20 watt nominal 12 volt panel and a suitable small charge controller. I do not have any recommendations for those. Let's see who else answers up on that.

6. This assumes that the panel will be hung clear of all shade or overcast and facing due south at an angle of roughly 45 degrees from vertical. Any other conditions will require a larger panel.

7. In actual use, you may never need to recharge a fully discharged light, in which case you could get by with less panel and less battery. YMMV.

8. If the battery weight is a major issue, you could go to a deeper discharge level and use as small as a 6 AH battery, but the same size solar panel. However this could have problems with the higher current used by the fast charger.

[PNjunction]

5. To replace the 2.5 AH, you should plan on putting 3AH back. Assuming that the number of effective solar hours (not the daylight hours, since the panel will not be doing much most of those hours) is 3, you will need at least a 20 watt nominal 12 volt panel and a suitable small charge controller. I do not have any recommendations for those.

What I use for nearly the same purpose. Get ready for sticker-shock. Costly, but I'm not worrying about reliability after dinking around with lesser quality stuff.

PowerFilm F15-1200 foldable 20W panel (fits inside large cargo pant pocket)
PowerFilm AK-1 Assurance Kit.
12aH agm battery
Digital voltmeter. Have a spare battery on hand!

The AK-1 kit contains various cables and most importantly, a Morningstar Sunguard 4.5A pwm controller with water-resistant connectors that tops out at 14.1v. So this should pose no problem with the streamlight charger if you decide to charge the light while the solar is connected to the battery during the day. Of course charging at night would present no problem right off the 12v agm.

You could part this out yourself if you want to construct a little project based around the Morningstar Sunguard CC I suppose.

[bonaire]

Because of the deeper discharge, wouldn't this be great for LFP batteries (LiFEPO4) and their ability to use almost their whole state of charge? Whether it is the cells in DeWalt type tools to flat-cells. It would seem they offer the most power/weight ratio and drainability. Some lawn tools are now starting to be sold with such cells (trimmers and blowers). It just seems that small-scale LFP isn't all there yet for many rechargeables. I'm not suggesting LiPoly cells (RC-grade) due to their volatility, just the LFPs.

I just googled around and did find some rechargeable Lithium-based lanterns using LED which could be coupled to a 12V energy source for recharging. You could possibly make a 12V solar panel output into a charger from some commercial products using a little ingenuity.