Battery Inquiry

For how long must this motor run on this supply?

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Is there a reason for using a battery of 24 volts, such as some competition where that is required? Everything is easier with higher battery voltage: cables can be smaller, no boost circuit is required, etc. The current coming out of your 24 volt batteries will need to be double that coming out of a 48 volt battery for a given power output.

3 Hp mechaninal load equals to 2200 W mechanical load equalt to +/- 2500 W electrical load (if efficiency = 85%) ...

Take care of the starting current. The internal impedance of a full charged battery is very low. This gives a very high start current motor armature and creates a strong magnetic field. This magnetic field demagnetizes the permanent magnets in the motor. If you need to start frequently, you surely need a kind of soft start.

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Probably cheaper and easier to simply double the number of batteries than to design and build a voltage doubling circuit that can handle such high amperage.

I'd guess that your truck batteries are 80 AH energy capacity, rather than 80A current capacity. A typical truck battery will have a current capacity of 600 A or more (much more for a very short period of time.)

746 watts = 1 hp x 3 = 2238 watts. Ditch the truck batteries and get marine deep cycle as those at walmart. Truck and car batteries are thin plate and not intended for more than a few seconds of operation, especially at one or more hp. 4 12V 100A marine D27's will do just fine in series and should run the motor full blast until it overheats. Get the heat range for the windings and a thermometer to make sure you do not damage the motor. TEFC motors (totally enclosed fan cooled) usually have the best insulation values. Are you using a pulse width motor controller, resistance or stepping the voltage? Do not pull the batteries down more than 20% from full charge or their life will be progressively reduced - more - each time. Keep them clean, always charged up and filled correctly with distilled water. Hope this is helpful.

TO GET 48 VOLT YOU NEED TO CONNECT 4 NOS. 12 V BATTERIES IN SERIES.

3HP WILL BE ABOUT 2250 WATTS. WITH 80 AH BATTERIES YOU WILL GET 80X48V= 384O WATT HOUR. YOU CAN SAFELY RUN UPTO 45MINUTES ONLY, AS VOLTAGE DROPS OF BATTERIES WILL INCREASE AMPERE AND MOTOR CAN GET DAMAGED. YOU NEED TO RECHARGE FOR FURTHER USE. SHOULD NOT GO BEYOND 50% DEPTH OF DISCHARGE,AS BATTERIES ARE WITH THIN PLATES. IDEALLY TUBULAR BATTERIES WITH 48 VOLT ARE BETTER OPTION IF YOU WANT TO RUN 90 MINTUES OR SO.

A useful answer. Thank you. But, please, the etiquette of the net makes all caps a form of yelling. Unless you really intend to yell, please use normal caps and punctuation.

Save ink. Or our eyes!

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Please say how the motor's starting current is handled, it is crucial to the booster's design.

If a tapped series (armature) resistor is used; a 'late 1950's' DC-DC converter circuit will suffice. This would consist of a centre tapped inductor fed with the centre tap to the +24V line with a substantial decoupling capacitor bank across the 24V supply. The ends of the winding will each connect to a NPN transistor collector and a rectifier anode. The rectifier cathodes are joined together to a large capacitor with it's -ve end to the -ve supply and the motor and starting resistor across that capacitor. The transistors' emitters are joined to the the -ve line.

A (separate) base drive tranformer's primary will be fed via a resistor between the ends of the inductor. The secondary feeds (via a resistor) the transistor's bases each with a diode's cathode to each base. The base diode's anodes go to -ve. The inverter commutates when the base drive transformer core saturates.