Solar power battery charger

[flygning]

I hike a lot, and I'm planning a backpacking trip, and my camera battery always seems to die waaaay too quickly. I can, and will (one of these days) buy an extra battery, but that doesn't help me much when I'll be in the wilderness several days at a stretch and each battery lasts only half a day. I've been looking into making a super lightweight, portable charger for my camera battery, along the lines of this but, obviously, for the camera battery and not an Ipod. My main goals are to keep costs and weight down and to not fry the battery.

Does anyone have any thoughts on how to make a project like this work for a camera battery charger? Or, failing that, does anyone know of a *cheap* solution to my problem?

 

[Garbz]

That is a bad idea unless you want to charge through the camera (like the guy charges through the iPod Dock). Charging the battery directly is something difficult as lithium ion batteries have a tendency to burst into flames if not charged very carefully.

If your camera has the ability to charge the battery via a power socket then all you would need to do is provide the regulated power to the camera and you're set. If not you would need a lithium charging controller (in case you know what you're doing DS/Maxim make some good ones which can be catered to a wide set of lithium batteries).

I would really look into the former solution first. Just note that solar panels are not cheap.

 

[Overread]

I can't comment on the design of the solar charger, but you say your battery only lasts half a day?
Out of interest would you take shots by looking at the LCD screen on the back - because that will drain a battery very quickly. If you can I would shift to using the viewfinder for taking shots and turn off the LCD.

 

[CanadianMe]

Half a day? As Overread said are you using live view and do you spend a lot of time reviewing your photos on your LCD screen? And when you say half a day, is that whether or not your using it? How many photos do you get?

 

[flygning]

I've been trying to use the LCD screen as little as possible, but I'm still at the point in my photography where it really does help me, composition wise, to just step back and look at the picture from a distance. The electronic viewfinder is nice, just more difficult to use. It does last longer when I use the LCD less, but still not enough to last for several days on 2 batteries. I get 300-400 pictures on one charge, and I take a lot of pictures

As far as the design of the solar charger goes, some places have come out with extremely well priced 5v panels. If I needed more than that (I haven't figured out numbers yet), the 12v panels are super expensive, and it would be worth it to look into a commercial charger. I was hoping I could do something along the lines of connecting the solar panels to a plug converter for a car, and just plugging the wall charger for the battery into that. Wouldn't I just be able to provide regulated power to that?

 

[eravedesigns]

I am planning on doing the same thing for future camping trips. As long as you get resistors and some transistors it should work. I have some electronics knowledge but even I would need to research this a lot more.

I did notice though on the site that sells the solar panels that you want to have a panel that has a voltage output higher than what you battery needs. The one the guy used for the ipod wont work for me at least because my camera battery needs an input of 8.4V.

 

[flygning]

The closest I have found to the 8.4 is 12V. That is no problem-- a charge controller would ensure it wasn't overloaded. However, what about the amperage? Would it have to be more or less than the battery charger normally supplies? It has been so long since I've taken any physics classes, it almost hurts my head to start trying to recall what all of these things mean.

 

[Phranquey]

However, what about the amperage? Would it have to be more or less than the battery charger normally supplies?

It can be less than what your battery charger supplies, but that will extend your charge time. If you have a 2000mAh battery, and your charger puts out 1000mAh, your batery will charge in 2 hours, in an ideal world. Some of that 1000mAh energy is required to overcome the resistance of the battery to accepting the charge, so it is realistically accepting about 850mAh. If you "build" a charger that puts out, say 500mAh, then your battery will take about 5 hours to charge...

But, Garbz is correct. Be very careful with LiIon batteries if you do make a homemade solar charger...never exceed the mAh rating in charging..i.e. for your 2000mAh battery, never exceed 2000mAh charge rate. This can have, um, rather dire consequences. Trust me, I have had LiIon batteries for my RC aircraft go up in flames with little warning, which why I charge them in the garage. These were open cells, not encased in a plastic housing like our camera batteries, but be careful anyway. Your factory charger is set at a specific rate for more than one reason...safety, liability, etc.

 

[flygning]

Thanks for the info on the amps. That really helps-- lower amperage makes the panels much cheaper, and I don't mind a longer charge time, since I'll have another battery.

I've never charged my camera using an AC charger-- would this be safer than trying to set up something with the actual battery charger? Also, since I would just be charging it while I'm hiking and not taking pictures, would it affect the overall battery life since I would be plugging it in and unplugging it quite a bit? Going that route really seems to be the simplest and cheapest setup, but I don't want to end up just having to replace the battery later on down the road.

 

[Overread]

Battery life does lessen over time - however provided that you fully drain and recharge the battery each time it should last as long as possible - its when people half drain and then recharge that the life in a battery is lost.
The other things to consider is temperature - for your solar cell make sure your battery is under cover in your bag and not getting cooked - direct sunlight can buildup heat overtime and that can damage batteries

 

[flygning]

Yeah, the heat is definitely a problem in AZ. I've also read that most of the solar panels actually put out less energy when they are over a certain temperature. Yikes.

Can one use the camera as it is being charged via the AC adapter? If I can, that'll be the way to go.

 

[Phranquey]

Battery life does lessen over time - however provided that you fully drain and recharge the battery each time it should last as long as possible - its when people half drain and then recharge that the life in a battery is lost.

That was the case with NiCd. NiMh and LiIon are not nearly as bad, but towards the end of their cycle life, they do go downhill fast...LiIon are pretty self-evident of when they need replaced.