How long battery works

1hp = 746 watts.

20ah x 48v = 960 watts-hours

So, you could get about an hour's worth of full load operation..

I'm sure I have something wrong, but I got motor resistance of 3.089Ω (V²/P)>>> 7.769 A at 24 V >>>> 2.57 hours. I s'pose motor/battery characteristics come into it......I'll just fade away like the battery.

If R = V²/P, then R = 24²/746 = .77Ω

oops - 48²/746 = 3Ω,

it's early yet.

so, 48V/3Ω = 16A, 20ah/16A = 1.25h

.....I didn't like to say about the 24² thing. So.....the 24V battery has to work against a reisistance of maybe about 3Ω...........

Hello "Guest".

You have a "DC" Motor which has a normal rated voltage of 48Volts.

You are supplying it from a "battery supply" 24V 20AH = half the rated Voltage.

<"....runs at 2500RPM at free-load and 1750RPM at 80% load.....">

• Is that above quoted speed the speed at the 24Volt supply?
• Is it the rated speed of the motor at the "normal" 48 Volt supply?

What type of windings are in the Motor:

1. Series wound
2. Shunt wound
3. Compound wound
4. Other - Advise please.

Also advise what type of battery you have:

1. Lead-acid
2. MiMH
3. NICd
4. Other - Advise please.

Please note that until all the variables above are made definite, no proper answer except guesses may be made.

Reply here to clarify the above, with

Kind Regards....

Hi,

Motor: No Idea about winding type, Brushed, PMDC Motor, 48V rated, 1HP, 2500RPM. But connected to 24V battery 40Ah.

Battery: Lead Acid, Deep Discharge. 12V.

No. I'm working on a project for my agriculture land where this system would be used.

Thanks

A

Can you wire up the battery and tell us the answer ? It sounds like it's only going to be a case of an hour or so. Is it a car battery ?

How will I know by wiring battery to Motor's winding type? please let me know what needs to be observed.

We took motor to shop to test the RPM which read about 1750RPM whereas Motor rated at 2500RPM. We did not hear from Manufacturer why this difference what label states and what was measured. Or it's possible that they have quoted wrong RPM on the motor.

Yes it's a CAR battery.

Thanks

If you want to know how long the battery will last, run the motor until the battery dies. You wont get the max rated rpm because your battery lacks the 'oomph' - it's only half the required voltage.

Is this a thinly veiled advertisement, for the battery factory in China: How Long Battery Works?

Kind Regards....

You haven't provided enough information to give a certain answer, but typically, a 48 volt motor will produce half its continuous hp rating at 24 volts. So this motor at 24 volts is likely to be a .5 hp motor, (or you would be running it at a higher current to get 1 hp, and that condition is likely to be time-limited.)

So, .5 hp = 373 watts. A 24 volt, 20 AH battery supplies 480 watt hours. However, the required current would be 373/24, or 15.5 amps. This is high enough that the AH capacity would be substantially reduced by Peukert's factor (Google) if the battery is lead acid. Depending upon the battery, you might be down to about 80% capacity. The battery should not be discharged to below 20%, (80% depth of discharge) so 80% x 80% x 480 = 307 watt hours available. Therefore, you could guesstimate about 3/4 hour. If your battery is one of the lithium technologies, then you'd be able to get nearly the entire 480 watt hour capacity out, giving about 1 1/4 hours.

To be more certain, you'd need the motor's performance curves and the battery's performance specs.