Author Topic: Max amperage of BAC-0281, BAC-0282, BAC0283 controllers?  (Read 9444 times)

Offline Little-Acorn

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Max amperage of BAC-0281, BAC-0282, BAC0283 controllers?
« on: November 05, 2009, 03:54:03 PM »
On the Goldenmotor home page, there is a link to "Controllers" on the left side of the page. When I click on it, it jumps to a page showing several different controllers, and different flavors of each. The first one is the BAC-0281, BAC-0282, and BAC-0283, running on 24V, 36V, and 48V respectively.

That page says their max current is 50A. But if I click on the "Cruise controller user guide" link just below the picture, a user's guide comes up, and on Page 2 of that, it says their max current is only 30A.

Which is correct? 50A or 30A?

Offline Hardcore

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Re: Max amperage of BAC-0281, BAC-0282, BAC0283 controllers?
« Reply #1 on: November 05, 2009, 05:42:45 PM »
i think they can handle 50A but do 30A, because at 48v the wattage input would be 48*50=2400 watt and at 30 amps 48*30=1440 watt.


ps. many people report 1000 watt at 48v


Offline Little-Acorn

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Re: Max amperage of BAC-0281, BAC-0282, BAC0283 controllers?
« Reply #2 on: November 05, 2009, 06:18:58 PM »
I guess the question is, where does their current limiting kick in?

Some of the motors I've been gathering data for, draw nearly 40 amps at 48V as they get loaded down. And the data sheet stops at that point, not telling me where their current consumption goes as you load them even more at full throttle. That's approaching 2000W, as you pointed out.

If you do that for a long time, you'll probably fry your motor. But if you do it just briefly, like to speed up from 5mph to 20mph and then back off to cruise at 20, I have a hunch these motors would handle it fine, since they start heating up only briefly and then get a chance to cool off.

A controller with a current limit of, say, 20A, is somewhat "idiot-proof", in that you can give it full throttle endlessly, and it will automatically REDUCE the voltage going to the motor to keep the current consumption under 20A. But if the controller has a current limit of 50A, then you can accelerate much more readily from 5 to 20mph, still without harming your motor. But, if you go up a VERY long hill, you might fry the motor.

Current limiting is a trade-off.

So, I'm curious what these Goldenmotor controllers will do, if I go up a long hill and try to feed 50A to the motor for a long period of time. Will they overrule me and feed the motor only 30A, or will they feed 50A to the motor as I told them to, and risk a burnout of the motor?

Offline Hardcore

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Re: Max amperage of BAC-0281, BAC-0282, BAC0283 controllers?
« Reply #3 on: November 05, 2009, 09:10:48 PM »
ok ;D

Offline rolf_w

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Re: Max amperage of BAC-0281, BAC-0282, BAC0283 controllers?
« Reply #4 on: November 05, 2009, 10:37:00 PM »
I guess the question is, where does their current limiting kick in? ... So, I'm curious what these Goldenmotor controllers will do, if I go up a long hill and try to feed 50A to the motor for a long period of time. Will they overrule me and feed the motor only 30A, or will they feed 50A to the motor as I told them to, and risk a burnout of the motor?

The BAC controllers are specified for 50A but GM confirmed that the current limiting software sets it to approx. 30A. We did some measurement ourselves and we never recorded much more than 20A. This current, however, is enough to fry the MiniMotors (http://goldenmotor.com/SMF/index.php?topic=1324.0)! The MOSFET in the H-bridge of the controller are rated for 75V 120A (http://goldenmotor.com/SMF/index.php?topic=1151.msg6451#msg6451), thus way above the current limits set by software. Obviously GM is afraid that motors and/or controllers are fried and sets the current limits very conservatively; As shown above the BAC controllers could possibly provide much more current - but how much more? For that one needs to overrun the current limit and to do that, one has to manipulate the shunt resistor (internal current sensor). Doing so (http://endless-sphere.com/forums/viewtopic.php?f=2&t=11015&start=0&hilit=magic) one can draw currents up to 60A (90A peaks) before the BAC fries. We had difficulties with components desolder from the printed wiring board...

Another difficulty is the regenerative braking (http://goldenmotor.com/SMF/index.php?topic=987.msg6422#msg6422) which kills the controller at much lower currents...

It would be very helpful to have access to the BACs software and set parameters e.g.  max currents. It would also be very helpful to have temperature feedback from the motor windings back to the controller - or at least a smarter current limiting feature in software which models the temperature development in the motor and thus could adjust the current limits dynamically. r