Electrics for a battery locomotive

Hello,

This is probably going to be a very simple question but I am not familiar with electrics and need some help.

I am building a 5 icing gauge battery locomotive. I have 2 12volt motors fitted which will be powered by a 12volt 24ah battery. The control unit is a 1x Motor Speed Controller Forward Reverse Switch PWM Governor 12V 24V 36V TE952. I think I should add a fuse and a circuit breaker but I do not know which one or how to go about calculating the right ones.

Many thanks,

Tim

Do you know what the motor ratings are Tim?

The controller is rated for 250 Watts at 12V, so it would be protected by a 20A fuse or circuit breaker like this example. 30A would be OK if you are a little braver. But if the motors are rated less than 125 Watts each, then the fuse or breaker should be reduced to Total Motor Watts divided by 12.

Dave

Hi Dave,

Many thanks for the reply, I'll look into this tonight. Can I ask how you calculated the right fuse? Its just I'll probably build a second in time and would like to understand every little aspect.

Many thanks, Tim

Tim, as Dave says the device advised will protect the controller but the motor current details are needed to perhaps provide sizing of fuse for each each motor to give protection from overloads.

Emgee

Based on what I have seen go wrong recently,

1 Dont copy road vehicles with their chassis earth return.

2 Keep wiring runs neatly tied up with cable ties and well away from moving parts like wheel flanges.

3 Always have main fuse or isolator.

4 Consider keeping an on board battery nut spanner

5 Watch out for horns, some are 2 wire, OK, but some are 1 wire, NOT OK, since this type relies on a chassis return.

6 Make sure control board is not directly beneath a roof top ventilator fan mesh, because when it rains...........

Good luck, hope it all pans out successfully.

John

Many thanks Dave, Emgee and John.

The motors do not have any information on them, I've looked at every part of the body but nothing. The chassis I am using is the remains of a sadcastings dock shunter which uses two of these

http://www.sadcastings.org.uk/accessories/standard-part-detail/electric-motor#

I can only assume these are the same type as I have.

very best,

Tim

Edited By Tim Ellis on 19/05/2019 21:05:07

Hi Tim,

It's from the equation Watts = Volts x Amps

Thus:

Amps = Watts divided by Volts

The specification of the TE952 says it can dissipate 250W and you have a 12V, battery so

Amps = 250 /12, rounded down to the nearest standard size = 20A.

I suggested 30A if you're brave because the TE952 can certainly withstand short bursts of higher current, so rounding up to 30A isn't foolhardy. An accidentally shorted battery could deliver several hundred amps - enough to melt the wires - so you want to size the fuse to deal with normal operation, about 20 to 30A, and to pop quickly if more than that is drawn due to a fault.

sadcastings website doesn't give any clues about the motor ratings, bit anti-social possibly it's tucked away on the plans! But judging from the price and photos, 10 amps each looks reasonable, and 20A total would be compatible with the controller.

Dave

Tim, those motors are listed as 12/24 volt 120 watt 3000rpm but it doesnt say if the 3000rpm is from 12 volt or 24. I dont know if you have a means of measuring the RPM but its needed to get the gearing something like correct, unless of course the gearing is already sorted on the chassis you have.

Ron

Hello Everyone,

I just wanted to say thank you for all the help unfortunately I've been in hospital and recovering from an operation so hadn't been able to reply sooner. I managed to wire up the locomotive today and fitted a 20amp fuse and circuit breaker. Everything ran perfectly on the rolling road.

. Many thanks, Tim

It's a really good idea to fit an isolator switch like this:

https://www.ebay.co.uk/itm/Universal-12V-Battery-Isolator-Switch-Kill-Switch-Winch-Isolator-DA2037/371193793900?epid=1326302701&hash=item566cdfcd6c:g:Z8wAAOSw0vBUbP7f&frcectupt=true
(random ebay item also available from motor factors and the like)

close to the battery.

Apart from an emergency cut out for a electrical fire or motor controller runaway they are a handy security measure. If you leave the loco for even a minute, take the key with you. You can it on an expanding key chain so you have to take it with you.

Robert G8RPI.