using a car battery charger as a power source? - RC Groups
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Jan 05, 2002, 01:17 AM
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using a car battery charger as a power source?


I was wondering if I could use my car battery charger as a power source for my dymond peak charger. The battery charger can provide 2 or 6 A (selectable) at 12 V, while plugged into the wall. Will this work, or am i going to burn the house down?!


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Jan 05, 2002, 01:29 AM
Registered User
I've found/heard that most peak chargers don't like car chargers as a 12V source... what you may find is that they false-peak. The reason for this is that the 12V they supply is very "dirty". If you look on an Oscilloscope, you'll find a lot of "noise". They also don't produce a clean 12v. (more like 15-16V).

Personally, I use an old AT-type PC Power supply with the 5V side loaded with a 5 Ohm resistor (don't use ATX). --There are lots of threads on this discussion.

I have used a 12V car charger on my Hitec peak charger, but it was hooked up to a battery at the time. (The battery would act like a filter, and smooth out the noise to some degree...)

What seems to work the best is any regulated source... You can readily find 12V 2A power supplies at the local electronics store...

Best of Luck!

Jan 05, 2002, 02:16 AM
Registered User
The 5V side of what loaded with a 5 Ohm resistor? The MotherBoard connectors? Or the HDD connector? I have lots of AT PS's. Thi would come in handy.

Jan 05, 2002, 08:24 AM
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Andy W's Avatar
What they said, for the most part. Many have had success using old power supplies, by putting a bulb or two across the 5V output and using the 12V output for their chargers. The load is needed on the 5V side for the power supply to function correctly, in most cases..
Jan 05, 2002, 11:48 AM
Vice President at MultiGP
Admiral_Red's Avatar
Or you can go to Radio Shack and pick up a 12V power supply with the built in cigarette adapter and 12 volt push in terminals, that is what I use...seems to work well albeit I don't have an oscilloscope to check for dirty power, no false peaks though!

Jan 05, 2002, 12:00 PM
Registered User
Thanks for the help!

Im not sure what you mean when you say put a bulb on the 5 v leads. My charger (everstart basic 6) only has one set of output leads, which can be switched to 6 v-6A, 12v-12A, or 12V-6A. My charger also claims to have an internal DC regulator, so it can use voltage from 8 to 15 V. I havent tried it yet, so I cant comment on the false peaks, but that explains why my father and law was getting so many false peaks (his is a older power source/charger).

Would putting a bulb in line on the 12 setting work here too? Any other way to clean up the power, or are these newer chargers cleaner?


Jan 05, 2002, 04:53 PM
Registered User
Andy W's Avatar
I was referring to old PC power supplies. They have two sets of outputs - 5V and 12V. The 12V doesn't work (in most cases) unless there is a load on the 5V output.
Jan 05, 2002, 05:16 PM
Registered User
Computer power suuplies are high frequency switching suppies... very efficient and light... the only problem is that without a load on the primary voltage source (5V), they won't properly deliver voltage to the other outputs... 1-2A is normally enough to load the circuit... use a 2-5 ohm power resistor rated for at least 20W. (they will get hot).

Some people have reported mixed success, but my hitec will deliver 5A to 12 cells without issues...

good l.uck...
Jan 05, 2002, 05:17 PM
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Peter W's Avatar
i also did a post on this subject and the consensus was that it isn't a bright idea due to the already mentioned, un-constant output. i now use a pc power supply which outputs 12v at 5A and connect THAT to my supernova and it works fine.
i used to use a car battery charger plugged to a lead acid field battery then plugged my charger accross the batt terminals before i grabbed a powersupply off a friend.

Jan 06, 2002, 03:42 AM
Registered User
I guess this is a no brainer. I did try my battery charger and it seemed to work ok with no false peak. But i was only charging at 700 mah. Ill see if I can find a power supply and some resisters. Thanks guys!

Jan 06, 2002, 09:24 PM
Registered User
Is there anyway using a car charger can result in a flase peak thats too late rather than too early?

I just charged a new 700 mah nimh at approximately 700 mah and it took 70 min...the pack is warm-hot, and it could have charged less than 700 mah resulting in less time, or the pack could have taken more, but could the false peak be too late?


Jan 07, 2002, 04:36 AM
Registered User
We tend to use the term "false peak" to mean switching off too early i.e. the charger thinks it's seen a peak but the battery hasn't really peaked yet.

It's certainly possible for a charger to miss the end of charge peak and overcharge but I don't think you have a problem. 700mA for 70 min to charge a flat 700mAh battery is exactly what you would expect. The charging isn't completely efficient so you always have to put in a little more than you might expect. You might think that 700mA for 1 hour would charge a 700mAh battery but it's not so.

HTH - Steve
Jan 07, 2002, 01:36 PM
Registered User

Thanks for the info.

Im wondering if the false peaks are more prevalant at higher currents....or maybe ive just been lucky twice in a row. Do the false peaks tend to happen later in the charger, or can they ocurr anytime?

This is a brand new car charger so maybe theyve cleaned up the power enough....?

Jan 09, 2002, 11:24 AM
Registered User
I use a car charger connected to a car battery with my Electric flight charger (Infinity ll) also connected to the car battery - so far no problems.

Jan 10, 2002, 10:56 AM
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buckeyes1997's Avatar


i am also using a car charger to a 12v motorcycle battery without any problems. im using smaller packs though. i understand that the battery actually filters and somewhat regulates the voltage from the "noisy" charger. great idea.