DIY Electric Car Forums banner

AC or DC Configuration

2479 3
Hi to all.
I am Alberto from Italy and I am new to the forum.
I have a big question...

Which is the best configuration for a small EV power plant in order to maximize the system overall efficiency? AC or DC configurations. The vehicle will integrated by photovoltaic system.

System voltage 48V
Batteries voltage 48V
Battery energy 1 Kwh
DC PV-Battery regulator 48V 60A
PV peak power 1.5 kw
Motor :48V 3Kw with different work speeds from 400-1000 rpm.

The question is:

It is better convert by an AC controller and drive an AC 48V brushless motor or use a DC-DC SEP-EX converter with SEP-EX motor? and Why?

Which the most efficiency solution? I am think about Curtis controller...there is any suggestion in order to improve the configuration.

1 - 4 of 4 Posts

· Registered
7,793 Posts
Hi Alberto,

Tough question. Strange vehicle. There probably is not a simple answer. Efficiency seems to mean different things to different people. To you is it the classical power out over power in? An instantaneous value. Or is it a drive cycle type of thing? Total energy consumed for a specified distance.

AC or DC? A lot depends on the particular equipment in question. If money (and time) was no object, AC could likely prove the more efficient. But you always have constraints. So what you can actually obtain may not be clear as to the efficiency winner.

I don't often recommend PM motors. But you have a small vehicle. You might consider a brushed DC PM motor with a minimal control. Like a starting resistor and run direct to the battery, or PV, without a controller in the circuit.

And, 400-1000 RPM for the motor is probably not an efficient choice for motor speed. Yeah, you can get motors designed for that speed in the power you need. But they are likely to be several times the mass of a higher speed motor and reducer combination. So, does the mass of the drive system enter into you efficiency figure? Not if you use the Power out/Power in. But it would for energy per mile if you have accelerations or hills to contend with.

No easy answers from me, but maybe some things to think about.


· Registered
2 Posts
Discussion Starter · #4 ·
Dear Major and 1Clue really thanks for your post.

The strange vehicle is not a car but a 24 ft solar race boat...i really hope that You can help not a car...I know

The best result for me is to maximize the overall efficiency in order to use the sun energy and battery energy in different load condition and maximize the propeller rpm.
If I understand well it is better a gear reduction to the low RPM 400-1000 and high rpm motors. Which is the best rpm value for motors?
It is not a problem of time or complex solution: my aim is reach the best ratio between efficiency and weight.

From Curtis data it seem that the controller AC or DC are quite similar change only the motor connection, so right now I do not Know what i have to do: it is enough to find the best efficiency AC or DC motor on the market? there is other parameter to check.

My problem is the different propeller speed rotation that depends from the sun and race time so inmy opinion the best is the AC solution because i can change the speed on motor and at low speed the magnetic loss are reduced then a DC PM. but it is really true? or I am speaking about little thing difficult to compare in the practice....

Please give me Your best help...

Kindest Regard from Italy
1 - 4 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.