Regen LiFePO4 with PM motor

Gottdi, thanks but I am not sure I understand your points/questions.
Here is more info:

When in generator (powered by the Diesel engine at 3200 rpm), the PMG132 might turn at approx up to 5800 rpm (reductor between the 2 engines). So I suspect it can generate voltage around 100 V into the controller.

In that case the 1st question is: What happens if the Kelly controller receives 48V from the battery but 100V from the generator:
(a) can it send only 58V of it to the battery pack,
(b) does it send nothing =0V in the case it exceed the 58V limit,
(c) does it damage the controller

2nd question: Whatever is the voltage produced by the generator: 15V, 20V, 30V, 40V, 50V, ... can the regen voltage coming from the controller to the battery be set precisely to a constant voltage (Lithium requirement), in my case 58,4 Volt or so (16 LiFePO4 cells of 3,2V that have to be charged at 3,7V) ?

3rd question: Of course it could overcharge the cells. It is not regen braking, but regen with Diesel powering the generator, it can last for hours. When the battery pack reach the 58V voltage, I guess the BMS sends an order to cut the charge. Since the charge is not coming from chargers talking with the BMS, Do I have to put a relay somewhere or is that max voltage managed by the controller?

4th question: if the voltage is too low, reaching about 40V, can it disconnect the electric engine (in order to respect the minium voltage of 2,5V / cell or so).

Last: the controller has to be reliable; I dont want to take the risk to blow the battery, or loose the $6000 of the LiFePO4 cells because of a controller bug...

So anyone actually doing regen with LiFePO4 and PM motor?

Thanks!

arn0 said:

When in generator (powered by the Diesel engine at 3200 rpm), the PMG132 might turn at approx up to 5800 rpm (reductor between the 2 engines). So I suspect it can generate voltage around 100 V into the controller.

Click to expand...

Hi arn0,

I think this will be a big problem. All of the available controllers for brushed PM motors are basically a buck converter for motor mode and a boost converter for regeneration. In motor mode, V_motor < V_bat. In generator mode, V_motor < V_bat. The same. If the motor voltage (as a generator) exceeds the battery voltage, the controller will fault, meaning shut down to protect itself. When the generator voltage is too high the controller has no means to regulate it.


Options:

• Don't run the generator that fast.
• Use a different controller for the generator designed to operate with high voltage input.
• Change to wound field machine.

I don't think you will be pleased with the durability and service life of that motor running long periods at high RPM. 5800RPM may exceed the mechanical limit for that armature.

Interesting project. Where are you located (what nationality)?

major

Sorry guys, my assumptions were wrong: voltage during regen is only 18V with diesel at 1800 rpm and 32V with diesel at 3200 rpm, with linear progression.
So I don't have overvoltage during regen, even if I slightly change the reduction ratio between the elec and diesel engines. Sorry for that.

I had my controller Bellmann CPM110-48 updated with lithium parameters and it works well. Still it is limited to 110A continuous and 150A 1 minute peak, I may upgrade in the future for more power (200A peak).
But this would be quite an investment for gaining only 50A peak.

And my main problem now is actually to reduce the load (size of the propeller) because the controller doesn't deliver the full voltage now (25V instead of 48, to limit the rpm due to the max torque under 110A).
So I am now actually using only 2.8kw instead of 5kw of the Perm PMG132.
Huge potential power gain here!

But... If I reduce the propeller it will be too small for the diesel and I would lose top speed under diesel mode.

Two solutions:
- higher reduction ratio between the 2 engines
- or install a controllable pitch propeller (smaller pitch with elec engine)

The two have their costs and difficulties.

I'll update you if interested

Thanks again for your help,
Arnaud

arn0 said:

Thanks for your comments and ideas.

I am French, from France.

I ordered the LiFeYPO4 Winston batteries at EV-Power.eu, waiting for them.

Sevcon replied they do not have a powerfull enough controller (200A 48V)

I think the solution is actually to disconnect the Motor (as a generator) if it reach a certain voltage, as it is what my current controller is doing.

I'll investigate and let you know

Click to expand...

Hi,

I have a similar setup running a sevcon gen4 controller and a Motenergy PMAC in parallel with a 12hp combustion engine. Regen is tricky and I still have issues with regulating voltage and current. You should know that if you go for Sevcon there is almost no information to be found on how to program them and the CAN interface used for programming is $900.

The setup I'm running now uses 36V and during regen I get about 15Amp's, this could be a lot higher but I don’t have the skills to program the controller.

I'm working on a second drive train and I'll go for the Kelly this time. I'm also going for 48V but I only need aprox. 80 Amps of nominal power.

Im using the LiFeYPO4 Winston batteries in my fiat, luigi500.blogspot.com, together with the akumon from ev-power. And I'm getting four more for the boat. The akumon board can be used as a safety switch durin regen. If the voltage of each battery exceeds 17V the akumon will trigger a 12V signal that can trigger a relay that in turn disables regen.

Please keep us updated on your findings.

Best regards

Rikard