I guess me sounding like a dumb ass goes without saying...

Thanks for the link, BTW.

lol more like ive never seen you say anything where you didnt know what you were talking about

did tha make sencE?

I usually try to answer my own questions, but sometimes it is easier to ask! I do tend to investigate things myself before relying on others to inform me.

I'm zip-charging a pack of the new smaller A123 cells (black and decker VPX... 1100mah) but I have not had a chance to monitor the current yet. It's not for R/C... it's for a cordless light I use for work. I charge it while driving straight off a lighter socket.

It's a 4s pack... so the vehicle's @14-14.5 volt system is perfect. That's a common voltage with the alternator running. The only bad part is that if my 123 pack is fully charged, and I leave it plugged in with the engine off... it's probably discharging back into the car battery. So I only plug it when while driving.

I'll bet you only get about 80% charge on that VPX pack. But that does not matter as long as you don't run out of juice on the job, Ever consider a 3s pack and a DB terminator. Might be a better solution.

Highfier

Maybe true. Are you on rcgroups btw?

Well...it may not get a 100% charge, but 3.6v x 4= 14.4 and my vehicle system runs at 14.5-14.7 so I think it's getting a pretty good charge. Some vehicles (alternators) may run a little lower voltage though. Even going by 3.7v/cell it's getting pretty close.

Anyway... the idea for this application is to keep it charged all the time... and charge quickly and easily. So far it's been pretty cool.

If your cig lighter circuit turns off when you shut the car off, then it won't back feed into your car battery. However, even if this was true, that pack could still be powering your radio and other accessories. :smile:

while driving is smart.

so hold on.

if i get a cig lighter converter (converts it to a normal ac outlet) and plug in a outlet thingy then clip off the ends and solder deans to them i can charge the pack through that?

do you guys get what im sayin?

YES Highflier is an account on RCgroups and it is ME :)

There are some reports of people using PC power supplies to charge a 3s A123 pack.

I get what your saying about the adapter for cig lighter, But I'll bet they put out 12 volt not the 14.4 an alternator is doing. Thus you are back to a 3 cell pack.

There is one downside to all of this stuff and that is remember to disconnect the pack when it is charged, ( we are slightly over charging them and they seem to handle that just OK, But I don't think you want to hold it at that voltage for hours) that is where the handy little circuit called DB terminator comes in. It is a automated cutoff when the pack reaches full charge.


The whol trick to this thing is trying to find a voltage supply that is greater then 3.7 per cell and less then 4.2 per cell. So a cleaver guy can play with a PC Supply and do lots of cool things.

PC supply ex. thought
-5 Volt and +12 Volt = 17 volts... Hmm that is 4.2X volts to a 4 cell pack.
or
+5 and +12 = 7 volts..... 3.5 volts for a 2 cell pack.... that would get you a 95% charge :)


I am not responsible for any results just throwing some thoughts out there...... Proceed with data in this post at your own risk. I have used only 3s and deep cycles batter so far.

After I get my DB terminator working I may expand my tests!

Highflier

ok so most of this makes sence.

what can i get to watch the volts and mah while it is charging?

the wattsup thing?

I have used 2 solutions.

1) Astro watt meter. It nice since it shows Amps volts and MAH charged into pack.

2) I made this.. (see link) Cost me under $10.00. By watching volts you know when it is charged. It's a dedicated system for me... I use the Astro for a second system when I want to charge 2 at a time.

http://www.rcgroups.com/forums/attac...mentid=1544395

Thats a $2.99 voltmeter from harbour frieght, wired in paralel near the deans plug.
Thats important as you want voltage near A123 not 15' up towards the Deepcycle.

Total cost was about $7.00 It gets me a charge in about 15 min. Chop 5' off the wire and it would probably be 10 min charge.

Highflier

Yes
 

It will work just fine. make sure you get source -> dest proper. byt default it may be reversed as they are usually setup for discharge from a flight pack not charge into a flight pack. Astro works both directions. My feigo only works 1 direction.

Highflier