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Regen LiFePO4 with PM motor

15332 Views 12 Replies 4 Participants Last post by  riwe
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 ?

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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!
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!
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?

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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).
Thanks for your comments and ideas.

I am French, from France.

I ordered the LiFeYPO4 Winston batteries at, 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
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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,
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