I need some 12 volt help.. Daughter found this $3.00 kids ride on car with a couple of problems. The axle needed restraining because of broken plastic bit. Easy fix. The 6 volt battery was being charged with a 12 volt charger which wrecked the battery. I used an old genset 12 volt battery to get it going. Of course goes like a V8 now drawing approx. .75 amp at 12 volt. Now need to have some control over the speed. Slower for the learners and flat out for the older kids. I had saved an old variable speed cordless drill trigger so connected that and it worked so put a cable tie around it at approx. 3/4 speed.
What I would like to do is have two speeds selected by a switch. I am thinking that a resister in the positive line to slow it down and then a switch to bypass the resister.
The resistor will work but will waste power as heat. This will lead to a shorter battery life between charges and a hot resistor - perhaps very hot.
The car consumes 9W (12 x 0.75) and the motor equates to 16R (12 / 0.75). If you put a 15R resistor in series it will drop about half the power and generate around 4W. Use at least a 10W ceramic resistor and ensure it's protected from contact by children as it will probably burn them.
__________________
"I beseech you in the bowels of Christ think it possible you may be mistaken"
Oliver Cromwell, 3rd August 1650 - in a letter to the General Assembly of the Kirk of Scotland
The resistor will work but will waste power as heat. This will lead to a shorter battery life between charges and a hot resistor - perhaps very hot.
The car consumes 9W (12 x 0.75) and the motor equates to 16R (12 / 0.75). If you put a 15R resistor in series it will drop about half the power and generate around 4W. Use at least a 10W ceramic resistor and ensure it's protected from contact by children as it will probably burn them.
Thanks Mike. That is what I roughly reckoned. It is not like they ride it all day. The only 5 watt resister I had was 22R. Might even look at a home made pwm controller.
Many years ago my son had a electric trike given to him as a Christmas present. after about 12 months the batteries failed. Ended up replacing them with a 12 Volt 17 Ah gel cell battery, went like bat out of hell !!!. so ended up wiring the 2x 6 volt motors in series and worked for a further 2 years. Finely the little gear boxes gave out with stripped gears . Parts n/a.
