# Battery power usage with weight?

How is battery usage calculated? if i have a battery powered golf cart and it has qty(10) 125ah 12v batteries and the golf cart weighs 1000lbs how far can i drive on a flat plain. NOW tie another 1000lb golf cart to it in tow, how far can i drive?

NOW.... with the same array of batteries in this question. say i have 37 sq meters of 100w solar panels, how long will it take to fully recharge the qty (10) 125ah 12v batteries

Please try to be as simple as possible in your answers as i am new to this field. Thanks

Update:

ok so if i wanted to INCREASE the power of the electric motor AND add 100 times more weight to the vehicle how would these calculations change? Also With the solar panel charging setup, does it extend the hours of usage since its being charged while its being used?

Update 2:

ok so if i wanted to INCREASE the power of the electric motor AND add 100 times more weight to the vehicle how would these calculations change? Also With the solar panel charging setup, does it extend the hours of usage since its being charged while its being used?

Update 3:

ok so if i wanted to INCREASE the power of the electric motor AND add 100 times more weight to the vehicle how would these calculations change? Also With the solar panel charging setup, does it extend the hours of usage since its being charged while its being used?

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• 8 years ago

A Disney employee, told me that they found one of their rental golf carts, smaller to yours, abandoned 12 miles from the rental station, so that may be close to maximum range. I'll guess 6 miles towing a similar golf cart. The texture of the surface makes a considerable difference, for my smaller scooter = shorter range on grass or gravel. Old batteries are not nearly as good as new batteries.

On an unusually bright sunny day in mid to late June, ten hours on 37 square meters will produce about 14,000 watt hours. 140 volts at 100 amp hours = 14,000 watt hours, so ten hours is minimum charging time. Two days, all day is typical, and that is optimistic. Almost a week near Christmas time, unless your solar panels are facing closer to the Southern horizon than to straight up. That is especially true if you live farther North than Atlanta, Georgia. Charging time will increase considerably if you are using your solar panels to power other loads.

I used 100 amp hours as you will shorten the life of your batteries if you use more than about 100 amp hours = the battery rating is likely slightly exaggerated. Old batteries tolerate less charging, so you should stop charging when the voltage gets to about 126 volts, not charging, and no load. 130 volts is ok for new batteries. The voltage while charging may never reach 140 volts, but we need to allow some for the efficiency of the batteries which gets worse as they age.

Are you sure you don't have ten 6 volt batteries instead of 12 volt batteries? That would be 1/2 the charging time. If you are in a hurry, you can likely charge from the electric power company or a generator set at the same time the solar panels are charging.

Edit: The other numbers are quite different, so perhaps the average is closer to reality. 37 square meters is about 3.7 meters wide by ten meters long, which is too big for a trailer, plus the sun angle will be very unfavorable in December unless you live South of The Panama Canal.

Surely you don't want to increase the weight 100 times from 1000 pounds to 100,000 pounds = 50 tons? I think we have you rattled.

Very expensive alternatives are available = battery packs for electric and hybrid cars which are about the size of your present battery pack, less than half the weight and more than double the range. Most of them are more than 120 volts dc, so that helps keep copper cost, the weight low and more power than your wheels have traction. Neil

• 8 years ago

The problem has far too many variables for a simple calculation.

First, the average 100AH 12V battery is close to 100 lbs. By itself.

Second, you need the power consumption of the motor, accessories, and accelerations involved.

Assuming you had 1250 AH (unlikely) and a motor which draws 12.5 Amperes at 12 Volts (unlikely),

you would divide 1250AH by 12.5A to get 100 hours.

If solar panels delivered 100 Watts at 13.6 Volts, you would divide 100 Watts by 13.6 Volts for 7.35 A.

37×7.35= 272 Amperes

1250 ÷ 272 = 5 hours

This all hypothetical. For advice, formulae, and general ideas, see source below.

• 8 years ago

Those batteries ratings mean each battery will put out 125 amps at 12V for one hour...theoretically. Since a battery starts dropping off in power once it passes about 50% decharge, I would rate the batteries at this, or about 65 amps at 12V for each battery before recharge is needed. Ten batteries gives you 650 amps at 12V for one hour or any multiple of that like 325 amps at 12V for 2 hours.

Watts are the power. Just like a microwave needs 900 watts of power or a 1hp electric motor needs 746 watts of power.

Watts = amps x volts

So for your storage capacity you have Watts = 650 amps x 12V = 7,800 watts

7800 watts / 746 watts/hp = 10.5 hp

That is plenty of power to drag around two golf carts. The weight doesn't make as much difference once it gets rollin, but the overall rolling resistance is hard to guess at. I look at how hard it is to push the cart manually in neutral by yourself and also hooked together with the other one. Rolling resistance falls off somewhat when it gets moving. But the higher the rolling resistance (air is negligible at under 15 mph) the more of the motors power will all be used to overcome this resistance. Once you get moving the main draw on your batteries will be the rolling resistance, so the lighter the load on the wheels and the more air pressure in your tires the easier it will roll

On a flat surface and as long as you don't stop and start a lot, it might only take about 3 hp of the available 10 hp to maintain speed. So you might go 7 or 8 hours on a charge. The lower the load, the longer the batteries will last before recharge

Sunlight falls on the earth with about 1000 watts per square meter. Solar cells are about 15% efficient in midday. So figure about 150 watts/m^2

with 37 sq meters you then have 5550 watts of power available. I don't know if you meant your panels have 100 watts per square meter or not, if so then you have to cut this power by 50% and then you are down to 3700 watts.

That is a lot of power..even the 3700 watts.

3700 watts / 12V = 308 amps

Most lead acid batteries don't do well with heavy recharge rates. So the good news is you probably don't need that many panels. A 12V battery usually does best with no more than a 10 amp at 12V charge rate, so you only need about 100 amps to charge all ten of your batteries and it would take about 6.5 hours to recharge , based on you drawing down 50% battery level of 650 a-hr capacity at 12V.

But here is an idea. If you had that many solar panels mounted on a lightweight trailer behind the cart, you could have enough running amps to run the golf cart motor DIRECTLY wiithout using the batteries. 3700 watts of power is almost 5 hp electric and that is strong. It should pull both carts easily when the sun is out. You could have the batteries for backup and only charge them when power output falls lower due to clouds or sunset