[arn0]

hi guys,

I'm struggling to understand if Kelly PM 48V controller can regen Lithium LiFePO4 or LiFeYPO4 batteries.

I have an parallel hybrid boat with a 18HP diesel on the same axel as the PERM PMG132.
I asked Kelly but I am very confused by the answer:
- they replied that the regen tension is proportional to the generator speed
- they put on their website that the controller "boost the regen voltage to the battery voltage" but that it can't cap the generator voltage if too high.

Has anyone here has a working configuration with Regen and Reverse, a PM motor and 48V LiFePO4 batteries ?

Thanks!

[frodus]

Regen Current is proportional to the generator RPM

The motor voltage is boosted so that it matches the battery voltage and charges the batteries, so it doesn't matter what RPM you turn at, it'll still boost to pack voltage. But the higher the RPM, the more current you can charge the batteries.


What controller model are you looking at?

Careful going in reverse on the PMG motor, it's meant for one direction only.

[arn0]

Thanks for your input.

I am already using the PMG 132 in reverse with 48V LeadAcid. According to it's datasheet, 48V is actually the limit to use it in both directions.

My current controller is giving me some issues, has limited power, and is not able to regen Lithium so I wanted to buy a new one with 200Amp continuous since the PMG can deliver 200Amps for 10minutes, but use only 110 Amp most of the time (and limit the 200A to some safety situation).

Since I need Reverse and Regen for my PMG132, as well as half-way throttle reverse, I only found that at Kelly.
I was particularly looking at the PM48501B.

If you know other controllers that match that would be good news too!

[frodus]

Not a lot of regen controllers out there, honestly. Sevcon has one though.

Get a guarantee from Kelly if you buy one that they'll work with you on making it work and replace it if it blows up.

[arn0]

Thanks, I checked Sevcon, it looks like a very good design, unfortunately I haven't find 48V DC PM controller with enough Amps (200) - correct me if I am wrong, I'd be happy to investigate the Lithium question with them.

Buy the way I am not jumping on Kelly since I don't know if it actually regen Lithium, meaning charging at constant voltage, securing the high and low voltages.

I have currently... no solution!

[frodus]

200A peak regen?

yeah, talk to sevcon, not sure if that's doable.


Wouldn't 200A tend to load that engine down pretty good? that is a lot of regen.

[arn0]

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!

[frodus]

100V damages the 48V controller.

You need a 100V or higher controller. You rate it the same way in generation mode as you would with battery mode. Also, you can't boost to a higher voltage than the controller is rated. Also, you can't feed the controller voltage higher than it is rated. You CAN however take 50V input say, and boost it to 100V on a 100V controller.

5800RPM seems REALLY high for a Perm.

[arn0]

thanks guys,

From my understanding battery pack will be 51,2V nominal (16 cells x 3,2V) and has to be charged at 58,4V (3,65V / cell).

Frodus, what your wright is specific for Kelly or any controller ?

Because on my current system the 48V controller stops the regen when the regen voltage is too high (>58V).

[major]

Originally Posted by arn0

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.

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