charging from dc adaptor

[betty.k]

i was wondering if i need to add a resistor or something when carging from a 500 ma 3-12 V power adaptor. i m charging nimh and nicad, and single cell and dual cell bcg s. i d like to be able to save using batteries if i can:8ball:

[Admin]

Hi! I just recently started doing the same thing. I am using a 1000 ma 3-12V and I am not using a resistor and am charging a single cell 150 mah for about 2 1/2 minutes. I have charged several times and am happy with the results. I tried 3 1/2 min. but the battery got a little too warm and appeared to leak a little white stuff…, but is still working fine. I read somewhere else from some guys that did several tests that 1000 ma was the best at charging our micros.

Quote:

i was wondering if i need to add a resistor or something when carging from a 500 ma 3-12 V power adaptor. i’m charging nimh and nicad, and single cell and dual cell bcg’s. i’d like to be able to save using batteries if i can:8ball:

Edited by – HyperHat on 18 December 2003 11:48:26

[micro_Amps]

3&1/2 minutes is way too long, the cell has boiled inside and the electrolyte has leaked out. That electrolyte is corrosive, so clean out the chassis tub on your car or the battery contacts will corrode and stop conducting.
A simple way to to use a 3v power supply to charge BCGs is to use a series load resistor. A 2 ohm 5 watt resistor in series with the positive wire that is connected to the battery will trim down the initial charging voltage and make the charging current a little more constant throughout the charging period.
I would guess not more than 2 minutes, but when you first charge this way, monitor the cell temperature, once you have a noticible MINOR rise in temp, then thats enough. Check the charging time (in seconds), and use this time for charging from then on.
Its not the scientific way to charge a NiCd or NiMh, but it will do. Those litle cells are pretty robust, although once they leak the are on a quick path to death.
:)uA

[betty.k]

so d’ya reckon i could use a light globe, being a resistor of sorts? it would help to have an indicator light:8ball:

[leonli17]

U can add a LED or globe for an indicator. But i don’t really think u need it unless u add a timer with the charger.
And i’ve use custom Power Adaptor chargers since i got my first Dual Cell. I used outputs range from 300mA to 1A. And from 3V-6V. The chargers are definitaly good when u r at home and u want a quick charge on a multi cell car. And it saves u a lota money from buying batteries.

[HACHI-RYOKU]

Hey, anybody got any ideas for my quad-cell beast (4 x 1.2volt/110nimh/digi-q batts/-1/4aaa)? Nothing I have will properly charge it. I also don’t have a peak charger. Anybody have any quick and easy ideas. I tried a wall-mount with selectable voltage. It’s rated at 300ma, and can select any voltage 1.5~12 in incriments of 1.5.
If I do the math, then; 4 x 1.2 volt, 110mah batts = 4.8 volts, 110mah.
If I want a good charge I will need to select 4.5 volts at 300ma, right?
For time to charge; Then 110/300=.36 + 20%= about .43hours. Or about 26 minutes.
Well, when I put it on the charger the the chip on the pcb gets extremely hot. Why???!!!
If I set the voltage down to 3 volts, it doesn’t get hot, but I dont think it will charge. After about 10 minutes it only twiches a little.
And of course, if I set the voltage to 6 volts it just gets hot faster.
Any ideas would be greatly appreciated.

[HACHI-RYOKU]

Another thought- would reversing (screwing it up) the current on the charging station give me these symptoms? It’s something I just thought of. I did test and double check, but I may have gotten the + & – backwards.

[micro_Amps]

The chip in your charger is getting hot because the cells are trying to draw about 700mA upon initial connection, and your charger can only deliver 300mA, therefore overload results in shutdown.
I charge triple cell cars with 9 volts, the series load resistor limits current to about 700mA and they are on the charger for around 2 minutes. But you need to be careful because a voltage that high, connected incorrectly, will fry your cells reasonably quickly.
You might want to try a 9v battery to charge your quad cells as well. Remember + to +, and – to -.
:)uA

[HACHI-RYOKU]

OOOIII! Thanx MA. I didn’t think I mixed up the + & – ‘s, but I couldn’t think of anything else.:smiley16:

[HACHI-RYOKU]

AAARRRGH!!!! It’s still not working. Tried the 9 volt and a box setup with 4 x AA’s. The 9 volt and the 4 X AA’s did give a mild charge to the batts, but I had to take it off the charger after about 5 seconds because the pcb on the car was getting hot again. Does anybody elses pcb get hot while charging? This can’t be normal.

This car is about to be the fastest thing into the trash can. It might break all previous records if it keeps on like it is. Damn quad cell! Thinks he’s a real hard case he does!! Thinx he’s so bad!!!

I’ll try 4 x AAA’s next, but I’m about out of ideas. Anybody got any fresh ones?

[z-beam]

are you holding the pcb with your fingers?

they conduct elec. and could be shorting the curcuit.

[HACHI-RYOKU]

No. I wait a few seconds, then I touch one side. It’s the black dot (chip right?) that gets hot, and the same spot on the opposite side.

I’m pretty sure that if I leave it charging I’ll loose the smoke inside. If it looses it’s smoke, it wont work.:)

[micro_Amps]

You are using a super BCG arent you.?

[HACHI-RYOKU]

No. I’m using a fet modded 2-speed bit pcb.

I talked to an electronics guru today and he said it’s probably the gauge wire I’m using. I use some pretty thin wire that normally works well with the dual cells, but may not have the capability to keep up with the higher voltage and current from the charging system for the quad cells. I’ll swap all that stuff out tonight and get with you guys when it’s done.

[micro_Amps]

Goodluck, but I am a bit doubtful it will be the gauge of wire. Even the tiny stuff can carry plenty for the tiny motor.
:)uA

[HACHI-RYOKU]

Oh, I agree. But running the car is not the problem. Just the recharging part, witch is done at a higher voltage and current.

The larger gauge wire doesn’t really sound like a solution when I put all the symptoms together, but it’s worth a try. I may have just jacked it up in the first place with wiring somehow, and ripping the wiring out and replacing it will show me the way. Although that doesn’t really support the signs/symptoms either. I’m lost and guessing at this point. Oh-well, to work I go.

[micro_Amps]

It sounds like you have a wiring problem, and yes, rewiring may show up the problem. It sounds odd that something is getting hot but only when charging. Something is not right, either there is a short circuit on the board, or you have a solder blob touching somewhere it shouldnt be.
Let us know what you find.
:)uA

[HACHI-RYOKU]

Replaced all wiring with CATV. Same symptoms. Fried two fets this time.

[micro_Amps]

Thats strange because there arent any fets actually in circuit until you press one of the drive buttons on the controller.
Which 2 fets did you fry?
(This is one of your own fet modded pcbs right?)
:)uA

[HACHI-RYOKU]

Two of the fets on the side. The first two that deal with forward and back in the line of 5 fets. Not the steering fets, but the next two after them. Sorry if this doesn’t explain it very well.

The batts didn’t get hot, just the pcb. Also, I was charging it while open with the pcb away from the batts, so I could monitor the batts temp, as well as the pcb. MA I p.m.’ed you.

[micro_Amps]

Yep, I got your PM, (no problem there)
There MUST be a short on the pcb somewhere.

:)uA

[HACHI-RYOKU]

I’m sending this thing off to MA. If anyone can get this thing running, it’s him. I’ll post a new topic on it’s return if he doesn’t do it first. I don’t see any reason it’s not working. Other people have made quad cells. I don’t know if they had fets on the pcb though.

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