I just purchased an E-flite apprentice and it comes with a LiPo charger with only alligator clips as a hookup. So I also purchased a rechargable Hangar9 12Volt 7Ah battery (han102) to supply the power to my LiPo Charger.

I have 2 questions.

1st. Roughly how many times I can charge my 3 cell 3200mAh 11.1V LiPo Battery using this 12Volt 7Ah battery source before the 12Volt Battery is depleted and would need recharged again?

2nd. I have a good volt meter with a lot of options. I know that if I switch it to vdc, I can get a reading off the battery to see it at about 12.77 volts. Is there a way to use a volt meter to see roughly how much capacity is remaining in the battery to know when its full, half or empty?

Question 1: Once, unless it's a deep cycle battery and you're still pushing it then.

Question 2: Yes. There is about a 1 volt difference between fully charged and empty, so when you get a volt lower than you were after a full charge you're done.

If you use the charger much, you might consider converting a computer power supply. There are guides here on RCU on how to do it.

I just did a little research. My 12v battery has 7 amp hours on it and my lipo charger needs 3 amps for a single hour for a full lipo charge. So it will take 3 amp hours for each full lipo charge letting me use this 12volt battery twice before its mostly depleted. This will suffice for field charging when I need it.

Just charge off your car battery

You can always pick up a 12v power supply and power your LiPo charger from wall power instead of a battery:

http://www.hobbypeople.net/gallery/158300.asp

I bought one of those electric cooler converters for using the 12 volt cooler inside the house. I cut the female cig lighter and put on eyelets so my alligator clips on my charger clip on to it. It says 5 amps output but I never charge over 3 amps. Use it on a Triton Jr. Paid about $15. Be careful with the lead acid battery's. They do not like to be brought down to far and even one time discharging it will take away most of it's life.

I have one of these and it works fine. Only $16:

http://www.hobbycity.com/hobbyking/s...ly_100~240v_5A

I also converted a PC power supply for about $5. It also works fine, but it's not much to look at.

Your car battery is really the best way to charge your LiPo's. I've topped off packs with my field box battery, but it doesn't last long doing that.

Good luck

Here are the instructions I used for building my power supply:

http://web2.murraystate.edu/andy.bat...owersupply.htm

It's easier than it looks, especially if you only need 12V. I had an odd Dell PS that none of the colors matched, but I was able to sort it out with a voltmeter.

All you really need to buy is the resistor (2 for $1.85) and the banana jacks (about $1). The switch and the LED are not really necessary.

if you want to charge out in the field, take your plug in charger, and get yourself a good power inverter. i have one that i keep in my vehicle, and it makes life so much easier for everything. no rigging something up, or having concerns about battery life. just plug it in to a power port, plug the charger in, and youre ready to go!

I also use a modified PC power supply. Here are the instructions.-BW

You guys are innovative. I bought a "battery eliminator" from Radio Shack. 13.6 volts DC (nominal) on two separate outputs.. one is banana plug the other is a typical car type "cigarette lighter" type port. It works well up to 25 amps continuous, from the wall, of course.

I plug in my Triton II EQ charger as well as my Duratrax IntelliPeak ICE charger. Both are programmable for just about any type of battery,

The ICE works from 12 volts input only where the Triton II EQ works from either AC or DC source.

But they are not cheap.

As I said, you guys are so innovative... hey.. if it works go for it!!!

I also bought a neat gizmo from Sears several years ago. It's an emergency car starter kit. It contains a sealed gel-cell high-current 12 volt pack inside of a case that has a handle on it, and has a pair of banana plugs plus the usual car cigarette lighter jack. It has an internal charger so I plug it in to the wall when I'm done for the day and charge it. I use it for my starter as well as a source to charge my glow driver, and, at the field, can plug my ICE charger into it and get my LiPo's charged in an hour (1C charge rate).

CGr.

I use a Triton Jr. for charging(old one with a seperate balancer). The PC power supply is what I use for 12 volt power at home. Its only rated for 350 watts. I use a deep cycle marine battery at the field. I am gonna need a new charger and power supply as the electrics I fly get bigger.-BW

That Sears emergency car starter gizmo works just great. It has a little handle to carry it around, and plugs right into the wall for re-charge. Charges overnight. It isn't a deep cycle pack, but it does the job. But, I end up re-charging it after a flying day.. just plug it in the wall along with all the other battery chargers and wall warts..

CGr.

My cousin uses one of those to power his charger. I think it even has an air compressor on it.-BW

Yeah, the one with the air compressor came out after I bought mine. That's ok.. it works and that's all I care about.

Now, when this one starts to give me trouble, I intend to get one with the air compressor and a higher capacity battery. It seems that if I use mine to charge batteries for my electrics, well, the drain is enough that it has a tough time spinning my electric starter for my glows. I guess I get lazy with the electric tools handy....

But I can tell you that these things are really handy to have out there. I power just about everything that needs 12 volts.. my fuel pump, TX and RX chargers, starter, glow driver charger, electric plane battery charger, all sorts of stuff... no wonder it doesn't last all day.. [X(]



CGr.

My next power supply is gonna have a 6 hp gas engine. I think Menards has them for about $299.00

a seven amp battery isn't much. i wouldn't use it maybe a couple of charges that's it. you can buy a motorcycle type battery of maybe 15 - 20 amp hr. or better yet a lawn tractor battery. they are high rated around 75 amp hr. these will last awhile in the field. put a strap, clothsline rope etc......non -conductive, from post to post for carring it. like a handle. they ain't that heavy or cumberson. they have power for charging for electrics also will supply enough amps to turn over bigger four strokes, even with a standard or h-d tower hobbies or hobby-co starter. also buy a battery maintainer for you battery. plug it in and leave it on the battery all the time. won't over charge and you will have a fully charged battery every time you go to the field................my .02...............................happy flying and charging................................RON

That charger is intended to be used from the battery of your car. That is why it has clips.

You can probably take 20 charges off your car battery without any concern at all, and likely much more.

I have flown multiple electric planes at the field for 6 hours, running 2 chargers to charge battery packs in the 900 to 2200 mah range andNEVER had a problem with my car battery. I have done this when there have been 5-10 electric pilots at the field and I can't remember anyone needing a jump start.

Now if you are charing multople 6000 mah packs to get one fiight with a large plane, then maybe Imight get concerned after 4 or 5charges, but not for your airplane. And if you are concerned, then start your car and run it for 15 minutes after 5 charges to refresh the car battery.

The only use for that 7A batteryis for your benchtop. I use an auto "jump start" booster box for my bench side charging. I pult the charger in for the "jump start" box, then I attach the battery charger to the jumper clampsand I charge in my shop. But that is only for a limited time, if I am doing work in the shop. Otherwise all my charging is done from my car battery.

You can get comments from electric airplane pilots in the electric airplane forum.</p>