Help! - Battery Holder Melting

shrewdPanther46
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Help! - Battery Holder Melting

Postby shrewdPanther46 » Tue Nov 28, 2017 3:24 am

When I place my five, 1.2V Nimh in a typical plastic AA battery holder (series), the plastic starts melting. I think this is because the springs in the case can't handle the current from the batteries and that is converted to thermal energy and everything is melting, although I am not really sure. I do know that this is not a result of the typical short-circuiting error. Can anyone please give me a solution to this issue, and any possible battery cases/holders that would work?



Thanks!
salty

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Re: Help! - Battery Holder Melting

Postby kinghong1970 » Tue Nov 28, 2017 3:43 pm

check if you have a short within the battery holder.
take a multimeter and do a continuity test.

shrewdPanther46
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Re: Help! - Battery Holder Melting

Postby shrewdPanther46 » Wed Nov 29, 2017 4:13 am

I tried and looked for other possibilities today. Nothing.

Could someone please point me to a battery case they are using to connect their batteries to their motor/switches (in series)?

Sorry for asking so much.
salty

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Re: Help! - Battery Holder Melting

Postby builder83 » Wed Nov 29, 2017 9:28 pm

I assume you are using a 6volt motor?

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Re: Help! - Battery Holder Melting

Postby shrewdPanther46 » Thu Nov 30, 2017 12:17 am

correct
salty

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Re: Help! - Battery Holder Melting

Postby retired1 » Thu Nov 30, 2017 2:54 am

I do not understand. Your car should only be under power for 5 seconds or less. That is not enough current draw to cause your problem

That said, what amperage is your motor rated at for 6 volts?

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Re: Help! - Battery Holder Melting

Postby shrewdPanther46 » Thu Nov 30, 2017 9:53 pm

retired1 wrote:I do not understand. Your car should only be under power for 5 seconds or less. That is not enough current draw to cause your problem

That said, what amperage is your motor rated at for 6 volts?

I am not entirely sure. I wasn't able to find a spec sheet for my motor. Is there a way to come up with an approx. with a multimeter?
salty

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Re: Help! - Battery Holder Melting

Postby retired1 » Fri Dec 01, 2017 11:37 pm

What is your motor name and number? I might be able to find something equivalent.

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Re: Help! - Battery Holder Melting

Postby shrewdPanther46 » Sat Dec 02, 2017 12:39 am

retired1 wrote:What is your motor name and number? I might be able to find something equivalent.


It's a non geared stock motor... my coach gave it to me, so idk anything about it. I know it's a 12 turn motor. I ran 8 batteries on it once and it melted. On five it also melts(I mean the springs on the case)
salty

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Re: Help! - Battery Holder Melting

Postby dmis » Sat Dec 02, 2017 5:18 am

To clarify, does the case start melting when the batteries are in the connector, but the connector is not connected to the motor? If so, you have an internal short in the battery connector. If not, post some pictures so we can get a better idea of what you have.

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Re: Help! - Battery Holder Melting

Postby shrewdPanther46 » Sat Dec 02, 2017 1:00 pm

While I am running the vehicle, the plastic near the springs of the battery case are melting(the side where the negative terminals of the batteries go). So yes, it's connected to the motor. I am 100% sure there is no internal short.
salty

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Re: Help! - Battery Holder Melting

Postby shrewdPanther46 » Sat Dec 02, 2017 1:04 pm

Sorry for double posting.
I can post some pics next time we practice because I think we disposed of the ones that were melted.
salty

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Re: Help! - Battery Holder Melting

Postby retired1 » Sat Dec 02, 2017 9:52 pm

Your motor must have some markings on it. That will help to determine Its amperage.

For a 550 size motor at 6 volts, you will have about 2.5 amps NO load and up to about 15 amps loaded. Stall amperage can be as much as 125 Amps. If you do not have reasonable gears, you probably are reaching near stall current for a short period of time. Your battery box will not stand that. Your buggy should instantly take off very fast or spin the wheels or not turn (stall). Somewhere in between.

If your wire sizes are small, this will generate heat in the wire and run the load up further.

I have the same battery setup that you do and do not have that problem. My problem is that the poor contacts will regularly not make contact, This required putting some brass inserts in to make sure that it made contact.
Also cut the wire from the battery box and soldered in much larger wire.

If you believe that the steel springs are not carrying the load, but are heating like a toaster, You might want to try cutting some fairly thin 1" wide brass stock (from a big box store) about 1/2" tall and slide that between the adjacent contacts. Should take 4, 2 on each end with no contact between strips.
I have never done this, so do not know what problems that it might cause like burning your motor up.

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Re: Help! - Battery Holder Melting

Postby shrewdPanther46 » Sun Dec 03, 2017 7:23 pm

retired1 wrote:Your motor must have some markings on it. That will help to determine Its amperage.

For a 550 size motor at 6 volts, you will have about 2.5 amps NO load and up to about 15 amps loaded. Stall amperage can be as much as 125 Amps. If you do not have reasonable gears, you probably are reaching near stall current for a short period of time. Your battery box will not stand that. Your buggy should instantly take off very fast or spin the wheels or not turn (stall). Somewhere in between.

If your wire sizes are small, this will generate heat in the wire and run the load up further.

I have the same battery setup that you do and do not have that problem. My problem is that the poor contacts will regularly not make contact, This required putting some brass inserts in to make sure that it made contact.
Also cut the wire from the battery box and soldered in much larger wire.

If you believe that the steel springs are not carrying the load, but are heating like a toaster, You might want to try cutting some fairly thin 1" wide brass stock (from a big box store) about 1/2" tall and slide that between the adjacent contacts. Should take 4, 2 on each end with no contact between strips.
I have never done this, so do not know what problems that it might cause like burning your motor up.


I really appreciate how kind and helpful you have been to me. I just have one doubt. Could the motor draw a lot of current from the batteries because the car is too heavy and the vehicle doesn't have enough torque? Do you think that simply gearing lower would be a solution to the issue (or getting a motor with more turns)?
salty

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Re: Help! - Battery Holder Melting

Postby dmis » Sun Dec 03, 2017 11:44 pm

Both ideas you mentioned could be possible solutions. A motor draws more current when the motion of the shaft is resisted, and the most when the shaft is stalled so it cannot move. So yes, if the vehicle is too heavy and the motor is stalling, that will cause it to draw too much current.

Small wires will generate heat, and therefore reduce the current to the motor making it less powerful. But if your wires are not what are burning up, too small wires is not your problem. Small wires will have a higher resistance than lower gauge wires, so less current will flow out of the battery and less heat will be generated in the battery.

Another small thing that could help: clean the spring contacts. Dirty contacts will have a higher resistance, causing more power to be dissipated in the battery case than would be if the contacts were clean.

If this issue continues, it may be easier to just buy a pre-made battery pack where internal connections would be sufficient for the rated current and you wouldn't have to worry about this issue.


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