# Rechargable battery question **URL:** \ **Category:** Factual Questions\ **Created:** [May 15, 2002, 10:16pm UTC](https://boards.straightdope.com/t/rechargable-battery-question/109288 "2002-05-15T22:16:11Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [May 15, 2002, 10:16pm UTC](https://boards.straightdope.com/t/rechargable-battery-question/109288/1 "2002-05-15T22:16:11Z")
Do I need to put in as many batteries as there are ports to complete some sort of circuit? My friend ripped apart an old remote controlled car for me - it takes 8 double a rechargable batteries, and it’s meant to be plugged into the wall (the car with adaptor) to recharge it’s batteries. If I only stick 2 in there, will it charge them properly? ---
**Author:** ![Tedster](https://avatars.discourse-cdn.com/v4/letter/t/4491bb/32.png) [@Tedster](https://boards.straightdope.com/u/Tedster)\ **Post date:** [May 15, 2002, 10:25pm UTC](https://boards.straightdope.com/t/rechargable-battery-question/109288/2 "2002-05-15T22:25:06Z")
Doubtful, 8 “AA” batteries in a series string = 12 volts. Without a full battery complement, no 12 volts to charge. ---
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [May 15, 2002, 10:45pm UTC](https://boards.straightdope.com/t/rechargable-battery-question/109288/3 "2002-05-15T22:45:28Z")
Is it possible it’ll charge, just at a slower rate, given the lower voltage? ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [May 15, 2002, 11:35pm UTC](https://boards.straightdope.com/t/rechargable-battery-question/109288/4 "2002-05-15T23:35:42Z")
Most rechargers will recharge them in parallel not in series so chances are it will recharge any number you put in. ---
**Author:** ![Tedster](https://avatars.discourse-cdn.com/v4/letter/t/4491bb/32.png) [@Tedster](https://boards.straightdope.com/u/Tedster)\ **Post date:** [May 16, 2002, 12:18am UTC](https://boards.straightdope.com/t/rechargable-battery-question/109288/5 "2002-05-16T00:18:40Z")
That could be, check the pin voltages with a VOM to be sure… ---
**Author:** ![Chris\_Luongo](https://avatars.discourse-cdn.com/v4/letter/c/7cd45c/32.png) [@Chris\_Luongo](https://boards.straightdope.com/u/Chris_Luongo)\ **Post date:** [May 16, 2002, 2:29am UTC](https://boards.straightdope.com/t/rechargable-battery-question/109288/6 "2002-05-16T02:29:57Z")
I don’t think I’ve ever seen a consumer device that uses multiple batteries in parallel. SenorBeef, the way the radio controlled car worked is this: All eight batteries were strung together in series, to make a 12-volt electrical system. If you have a two-battery flashlight handy, take it apart to see what I mean. The - lead of one battery goes to one of the contacts on the bulb. The + lead of that battery butts up against the - lead of the second battery. The + end of the second battery goes through the switch, and then to the other contact on the bulb------looking at the flashlight should give you an easy-to-understand example of a series circuit. (Here’s a little trick to get another hint to verify that the RC car wires the batteries in series: Look at the power-pack that charges the car, how many volts does it put out? I’ll bet it’s in the neighborhood of 12 volts.) What are you trying to do? Are you trying to find a way to charge two AA rechargable batteries without purchasing a charger? If so, try this: Get a 2-gang AA battery box from a broken toy, or buy a new one at Radio Shack. Find a power pack that puts out 3 volts DC. Wire the battery box as a series connection, and hook it to the power pack. ---
**Author:** ![bbeaty](https://avatars.discourse-cdn.com/v4/letter/b/c0e974/32.png) [@bbeaty](https://boards.straightdope.com/u/bbeaty)\ **Post date:** [May 16, 2002, 4:31am UTC](https://boards.straightdope.com/t/rechargable-battery-question/109288/7 "2002-05-16T04:31:15Z")
> [@](#): > > \*Originally posted by Chris Luongo \* > What are you trying to do? Are you trying to find a way to charge two AA rechargable batteries without purchasing a charger? If so, try this: Get a 2-gang AA battery box from a broken toy, or buy a new one at Radio Shack. Find a power pack that puts out 3 volts DC. Wire the battery box as a series connection, and hook it to the power pack. But if you leave such a thing plugged in, it might destroy the batteries through overcharging if it doesn’t just wreck them from overheating. (NiCads are around 1.2v, two in series are 2.4v) You need a resistor in series so you create a “trickle charger.” I don’t know what the value would be, since it depends on the actual voltage of the power supply. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [May 16, 2002, 4:38pm UTC](https://boards.straightdope.com/t/rechargable-battery-question/109288/8 "2002-05-16T16:38:16Z")
> [@](#): > > Most rechargers will recharge them in parallel not in series so chances are it will recharge any number you put in. This is correct for separate rechargers. It sounds to me like **SenorBeef** has a car with adapter where the batteries aren’t meant to be removed, but are recharged in place. This means they can’t be switched from series to parallel for recharging. If this is the setup, don’t try to use the car adapter to recharge them without the right number of batteries in series. ---
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [May 16, 2002, 5:27pm UTC](https://boards.straightdope.com/t/rechargable-battery-question/109288/9 "2002-05-16T17:27:16Z")
You guys are right, although it’s an 18 volt charger rather than 12. Out of curiosity, would trying to charge result in no charge because of an incomplete circuit, or blown up batteries because of a high voltage charge not having anywhere to go? ---
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [May 16, 2002, 5:32pm UTC](https://boards.straightdope.com/t/rechargable-battery-question/109288/10 "2002-05-16T17:32:45Z")
You guys are right, although it’s an 18 volt charger rather than 12. Out of curiosity, would trying to charge result in no charge because of an incomplete circuit, or blown up batteries because of a high voltage charge not having anywhere to go? Btw, I’m not trying to be _that_ cheap. I went out looking for chargers expecting them to be in the $10 area, but just a little charger that was basically a plug and 2 battery ports was $30. Yeesh. ---
**Author:** ![AndrewL](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@AndrewL](https://boards.straightdope.com/u/AndrewL)\ **Post date:** [May 16, 2002, 5:39pm UTC](https://boards.straightdope.com/t/rechargable-battery-question/109288/11 "2002-05-16T17:39:45Z")
It sounds like the batteries are wired in series in it. In that case having less than the full number of batteries will result an open circuit. The car won’t run, and the batteries won’t charge. If you somehow jumpered out the spots where no batteries go, you’ll complete the ciruit. In that case you’ll be trying to charge the remaining batteries at too high of a voltage and destroy them. The same can occur if you stick a mixture of discharged and charged batteries in at the same time. ---
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [May 16, 2002, 5:48pm UTC](https://boards.straightdope.com/t/rechargable-battery-question/109288/12 "2002-05-16T17:48:22Z")
Woops, didn’t think that first post went through.