# overvolting



## illuminateddan (Dec 19, 2009)

poprock1 said:


> Question for anyone: What is the maximum volts allowable for a 36v st marys cray brand forklift series wound motor?


Hi Poprock, I know this may be a silly answer, but for a 36volt motor the max voltage is 36 volts! You may be able to push the voltage higher but you'd need to watch the temperature of the motors windings (coils of wire inside) as they may melt, short circuit and blow! Ouch  Really the best thing to do would be to contact the manufacturer and ask them what the absolute max voltage is, and how long the motor can sustain that. Often 'overvolting' a component will shorten its life span as its no longwer working as intended.



poprock1 said:


> Another query about low amperage batteries. One contributor stated that lower amp batteries in series give better results than a minimum requirement of high amp batteries.


I think this may be a little confused.... Basically it is about basic electrical theory:

1) Batteries in *series* (lined up +ive to -ive like in a torch) add voltages but keep the same current rating, so for example, 

three 12 volt 1 amp batteries connected in *series* will provide 36 volts at 1 amp.

2) Batteries in *parallel *(all the +ives connected together and all the -ives connected together) keep the same voltage but add current. for example,

three 12 volt 1 amp batteries connected in *parallel *will provide 12 volts at 3 amps.

So for your 36 volt motor you really need 3x 12v batteries connected together in _series_. 

An easy rule is this.... The volts provide the speed, the amps provide the distance.

It would probably be worth your while checking out this page... http://www.batteryuniversity.com/partone-24.htm

Also, check out the wiki here for info.... 

Hope this helps!

Dan


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## DavidDymaxion (Dec 1, 2008)

Many EVers run their motors well above the nameplate Voltage. Typically the rated numbers are for continuous operation, like for a forklift running 24/7. A typical street vehicle does just short bursts of high power, and can't run for much more than 1/2 hour anyway due to battery capacity, so the motor can be run well past the continuous rating. This is unlike gasoline cars, that are usually rated at peak horsepower. Hopefully you can find someone who has run that exact motor. You can look at http://www.evalbum.com and http://www.nedra.com to see what kinds of voltages folks are running (caution, many of the NEDRA guys have motor mods to allow higher voltage).

Ideally it wouldn't matter whether you got your power from higher Volts or from higher Amps. In practice, it is a bit more efficient to go higher Volts, as losses scale as current squared, and fixed drops become a smaller fraction of total Voltage. This is a small effect, though, don't feel like you have to do a 336 V megabuck AC machine, a 144 Volt conversion can also have good range.


poprock1 said:


> Question for anyone: What is the maximum volts allowable for a 36v st marys cray brand forklift series wound motor? I have read what appear to be contradicting opinions. Another query about low amperage batteries. One contributor stated that lower amp batteries in series give better results than a minimum requirement of high amp batteries. My electrical knowledge is nil +2 %.( i can tell pos from neg) so could you dumb your answers down, thankyou.


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## 9852 (Jan 17, 2010)

you could take the motor to a local motor repair shop the have it looked at. most forklift motors can be overvolted a little bit, but to get higher voltages, the repair/rewined shop can adjust brush timing. they will tell you what can be done with the motor you have and in most cases for cheap.


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## illuminateddan (Dec 19, 2009)

I totally agree, I run a 72v rated motor at 125v nominal and the magic smoke hasn't come out yet. However, I would definitiely try and get your head around the electrical basics before you pump 100v into a small motor.....


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