How do I figure out how to charge my battery? *Pictures* - RC Groups
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Sep 21, 2009, 10:25 PM
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How do I figure out how to charge my battery? *Pictures*

Hello, everybody. I'm brand new here, and essentially just starting out in RC. I've dabbled for years, but now I have a serious car. Thing is, I got this vehicle second hand and, while I'm pretty sure all the parts are there, I don't know how to charge the battery to even see if it works.

Here's the setup: The car came in what looks like a homemade box with a built-in charger. All the radio parts are Futaba (pretty old, I think). The charger is JoMac and features a timer, amp-meter, and switch to select 4 or 6 cell batteries. Power is supplied through a pair of clamps that look like they were intended for a 12-Volt battery. The battery pack on the car consists of two sections wrapped in heavy paper and with a wire soldered across one end.

So here's the question for all you experienced geniuses out there: how do I know how long to charge my batteries for, and how can I figure out whether it's 4 or 6 cell? The better I describe this, the more I feel like I'm going to have to disassemble this car or the battery pack in order to see what I'm doing. The whole things feels very much homemade, so I don't think I'm going to encounter any 'no user serviceable parts' warnings. Or maybe I should just replace the entire battery? If so, how do I know what to replace it with? If you need any more information to answer these questions I would be happy to provide it. Pictures perhaps?

Any help you guys can give me would be very much appreciated.
Last edited by tofor; Sep 22, 2009 at 09:30 PM.
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Sep 21, 2009, 10:57 PM
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kistner's Avatar
pictures would help. It sounds like you have a timed charger; i'd skip it and look for a peak charger. peak charger will automatically determine when the battery is done charging.

using the timed charger requires knowing the capacity of the battery. it sounds like you do not, plus if the battery is as old as the charger, it may not take a charge.

if you take the capacity of the battery and divide by the current supplied by the charger you end up with the time required. ie: 5000mah battery (or 5 amp hours) with a 5 amp current would be fully charged in an hour. keep an eye on it, check the temps of the battery. they should get very warm by the end of charging, but not burning hot.

also its not a bad idea to stay within a 1 amp hour to 1 amp ratio or less. meaning i would NOT charge a 2500mah battery at 5 amps, but I might charge a 5000mah battery at 2.5 amps (for two hours or until its very warm/almost hot).
Last edited by kistner; Sep 21, 2009 at 11:03 PM.
Sep 21, 2009, 11:01 PM
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Thanks kistner. I'll try to get some pictures tomorrow.
Sep 22, 2009, 09:30 PM
Registered User
Here's some pictures. Hope you guys can tell me more from these pictures.
Sep 22, 2009, 09:48 PM
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kistner's Avatar
well, it is a 6 cell battery. other than that, every thing there is serious vintage, I have not seen any transmitters like that. It may actually be valuable to a collector. I don't think I would trust the charger, has that homemade look to it.

the car itself is some sort of pan racer I think, not really my thing but I have seen them around. It has a mechanical speed controller and I have not seen one quite like that either. There does not appear to be any transmission, it's direct drive. I am not so sure this is a car for the road, it may have more value as a collectible.
Sep 22, 2009, 10:04 PM
Rampage's Avatar
Woow, that is old. Yeah, I would look into upgrading it to modern electronics if it's something you're serious about keeping. And I would sell the radio on ebay and put the charger up on a shelf for people to look at..Lol.

That's awesome tho..The TX is a Futaba FP-T2F from the early 1970s.

You've got a time capsule there.

You probably can't charge the battery. It's so old it probably wouldn't hold a charge anyway. Your best bet is, like I said earlier, if you intend on driving the car, updating it to modern electronics/battery/charger/motor.

Personally, I would keep it the way it is and put it under glass and think about "Wow. This hobby has come a LONG, L-O-N-G way since the 70s!" every time I walked past it. Very, very cool.
Last edited by Rampage; Sep 22, 2009 at 10:11 PM.
Sep 22, 2009, 10:31 PM
Registered User
Haha, I knew it was older, but I didn't really expect that reaction. Anybody want to buy? Since this does look like a home-built-from-scratch I doubt a serious collector would want it. I would be interested in making it run, but I don't think I want to put all new electronics in it, I might as well build a new car from scratch! This one came out of a dumpster at my grandma's apartment complex. A new battery/charger would be about as far as I'd want to go. What would be the secret formula for what battery to get?
Sep 22, 2009, 10:57 PM
Rampage's Avatar
Well, any 6 cell battery will work.

If you just want to see if it works, go with the cheapest of the cheap.

1500MAh battery, $8.99

A nice lower-end charger just incase you decide to stick around in the hobby.

And then some new connectors to use on the speed control to hook up the battery to the speed control.

And that should get you running again assuming everything else works.
Sep 23, 2009, 05:30 PM
Registered User
Hmm, that charger is a bit expensive just to see if the car works. Is there any kind of bare-bones charger I could get that would be 'just good enough'?
Sep 23, 2009, 05:42 PM
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kistner's Avatar
to 'see if it works' you could use 6 regular c batteries all in series. might be a pain to rig up, but if you are just testing it and do not want to spend any money on it . . .
Sep 23, 2009, 07:36 PM
Rampage's Avatar
Go to Radio Shack and see if they've got anything on sale. I know the store I work for has a 6 cell 1,500mah battery and charger on sale for $9.99.
Sep 23, 2009, 07:43 PM
Registered User
Ah, cool. That would tell me if it's worth the investment in more parts. What's so magical about 6 batteries? I don't have C batteries on hand, but I've got dozens of AA's, any chance those would give me enough power?
Sep 28, 2009, 07:34 PM
Registered User
Hey Rampage, any chance you could give me a model number or something? I stopped at my local Radio Shack and there was nothing even close to that!
Sep 28, 2009, 09:42 PM
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kistner's Avatar
check the voltage on your camcorder battery if you have one, if its 7.2 to 7.4 you can use it to test. and yes, if you have 6 really good aa batts you can probably test it with those, i wouldn't run it too much like that.
Sep 29, 2009, 05:52 AM
Rampage's Avatar
I'll see what I can do about a CAT number for that battery and wall charger.

But if you're going to use AA cells, use 5. 6 AAs is 9 volts, with each cell being 1.5 volts instead of 1.2 of NiMH cells. So 5 will be 7.5 volts, which is closer to the 7.2 volts those old electronics are rated for.

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