Powering motor while charging batteries

[jstewa04]

Hi,

I am building an electric vehicle that will be charged using solar panels. I have a few questions still after researching the topic.

some system details:
48V PMAC motor, 6-15 hp
3-series connected optima yellow top batteries--38 Ah @36VDC
520 watts from solar panel

I am wanting to use the power the motor first with the solar then charge the batteries with any remaining power (although there might not be any). I am looking for a way to charge the batteries at 45V (15V/battery) while powering the motor at 48V. Is there such a device that would allow me to do so?

I'm a newbie to this but I'm hoping to learn a lot.

Thanks,
Josh

[Mike90250]

Welcome. First, let me be sure I understand a term you are using 48V PMAC motor, 6-15 hp Translates to 48V Perm Magnet AC motor ?

Will your DC-AC motor drive controller handle the voltage step up from 36VDC ? Why not add another battery and make a standard 48V bank ? What is the voltage from the PV panel and what will you use as a charge controller for the batteries ?

[Sunking]

What you want cannot be done. There is no remaining power period. Your panels, which you do not have enough room on a golf cart for 520 watts of panels, 200 max will not generate enough power for 15 minutes of run time. Secondly I have no idea where you are coming up with 6/15 hp on a 36 volt motor is nonsense. Your batteries are not capable of delivering 400 amps, nor is even a 1000 watt panel cannot do that.

You have a 15,000 motor trying to power it with a 520 watt panel that cannot deliver 520 watts. Common sense ought to tell you this is nonsense. FWIW I have built several racing golf carts. Solar is pretty much worthless on a golf cart. Park it out in full sun all day gives you about 2-3 miles extended range if you are lucky. But it is impossible to run any cart on panel power alone. .

[jflorey2]

some system details:
48V PMAC motor, 6-15 hp
3-series connected optima yellow top batteries--38 Ah @36VDC
520 watts from solar panel

I am wanting to use the power the motor first with the solar then charge the batteries with any remaining power (although there might not be any). I am looking for a way to charge the batteries at 45V (15V/battery) while powering the motor at 48V. Is there such a device that would allow me to do so?

Not easily. Most people choose battery voltage, run the motor inverter at that voltage, and then choose the charge controller to charge the batteries - not the other way around.

At (say) 12 horsepower you will need about 200 amps at 48 volts. That's about 9600 watts. So if you use you 520 watt PV array, then the battery will be supplying ~9080 watts.

To put it another way, the solar you propose will provide about 5% of the power you need. The rest has to come from the battery. And if your panels are at all draggy, they will increase the power you'll need to move the vehicle - and your range will likely go DOWN after you add solar. That's why none of the commercial EV's out there have a solar panel that charges the traction battery.

[Sunking]

To put it another way, the solar you propose will provide about 5% of the power you need.

Not even that much once you consider the panel only peaks for an hour per day around noon. I know what motor he is talking about, as their is only one such motor on the market made for golf carts. It requires a 500 amp motor controller with 48 volt input.

His plan really falls apart if you take a look at his battery selection using 12 volt Optima batteries. I can only assume he would be using the Largest Blue Top Optima 75 AH battery which would require 4 of them to make 48 volts trying to push up to 400 amps. No way can the batteries do that much current without excessive voltage sag. 48 volt golf carts made today use 160 to 190 AH batteries using a 5/10 hp AC induction motor with a 275 amp controller. The only way to do what he wants with that small of a battery is to use lithium batteries. But even if he did that the panel is pretty much useless. I have no idea how he expects to put 520 watts of panels on a golf cart as the roof area is only large enough for 200 to 250 watts.

[DanKegel]

Have a look at some commercial systems, maybe.
http://www.solarmotorsystems.com/pro...battery-backup says a 5 HP motor requires "18 panels" (presumably they mean full sized 250-ish watt panels).

Are you thinking of putting the panels on the vehicle, or on your house? If you want to put them on your vehicle, that's way, way harder, probably beyond an individual's ability; see e.g. https://en.wikipedia.org/wiki/Solar_vehicle

Time to rethink. You need a radically light vehicle with a much smaller motor, and probably lithium batteries.
http://www.electric-bikes.com/ might have some ideas.

[Sunking]

Stop it Dan you do not know squat and do not even have a clue what you are responding too.

[HadrianKross]

1kw battery bank...
not unheard of, but only 1 hour.

2kw? 3kw?

LiFePo might not break the bank.

Li will.

solar panel(s) sounds feasible, but will primarily charge.
slight boost when running on that motor.

Decide what you want to keep, panel? battery? motor? and what needs to change.

If you’re stuck on the motor then you need better battery tech. you may want better solar tech...

edit: if an hour works for what you’re doing then just focus on the solar I guess...

[PNPmacnab]

There are people doing this re powering boats with electric. A linear current booster would supply as much power to the motor as can be generated. Batteries just for return to dock when sun dissipates. Cruising on a lake at 1mph is relaxing. Lots of examples of this. The boat RA has traveled the inter-coastal waterway many times on just solar. It went by my house one time and I about couldn't stand the whine from 800 feet away. I asked him one time if he was deaf. He looked at me strangely and told me his drive didn't make any noise.

[HadrianKross]

it’s currently over 1kw, so 1 hour, all solar goes to the motor, only charges when there’s no draw... everything works, but if they want excess? from 1kw solar?? /shrug check out solar prototypes over the years...

i’m going to play around with turbines and super caps...see if new very efficient (no drag?) can overcome real drag (at least it will charge when i stop in high wind areas...at night) but that’s the power trailer prototype NOT the vehicle. and yes a solar roof. wonder what force is created when wind spins off rather than curves off?? force is up? down? negative?? centripital says down right...wonder if engineering could force that upward...that would create lift right? (maybe just stow it till nightfall...or a bunch of small computer fans for cell phones)

wiring should be: motor -> speed controller/throttle -> solar panel -> charge controller -> (bms) -> battery bank (depending on your speed controller, it may block charging while turned on...so might have to bypass or other rewiring...though i don’t know anything about pmac motor controllers...only dc. I do know there’s a loss at every step up/down and every conversion...)

edit: lift reduces friction on the wheels of the trailer...plus energy production...out of theoretics, time to test.

edit: mosfets handle speed/motor voltage; cc handles battery voltage; only concern is current/amps and speed/charge controller(s) rating...minor concern for life of speed controller if max volts over time from pv...