question

bite avatar image

How to limit the current in a 48V alternator?

For a project the customer has a 48V 150A alternator.

I recommended, the following solution

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As the Cyrix at 48V only allows 80 A, can I put two in parallel?

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The ideal to protect the alternator would be to have a current limiter. Unfortunately, victron only has current limiters for 12 and 24V.

Does anyone have a suggestion for a better 48V solution?



alternatorcurrent limit
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what is the modal of the alternator? is it a pma or does have field coils

@mt_geek I do not have this information. My idea is to have a solution that works independently of the alternator

4 Answers
safiery avatar image
safiery answered ·

@bite we have completed many 48V alternator powered projects. Use a 48VDC Alternator controller . The thing to avoid is a load dump and so keeping the alternator connected at all times to the 48VDC target battery to be charged is essential. There is no need for Cyrix units. We supply 48VDC alternators at 5kw in a compact frame as the second power source for large USA SUV’s and Sprinters. We supply 12Volt-48volt (or 24v) 3000W bidirectional DC to DC with charging capability or to supply chassis loads from a 48V alternator. This unit also successfully captures up to 250A from outboard alternators to charge 24V victron lithium banks running gyros while keeping the 12Volt pin active for all the 12Volt loads.

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Thank you @safiery, I was coming back to this thread for the express purpose of tagging you!

@safiery if it allows you to control the charge current of victron lithium batteries at 48V, it would be the recommended solution.

can you send me the datasheet?

@bite I purchased a 24v alternator and controller from @safiery to charge my 400A 24 Smart Lithium bank (constructed from 4 x 12,8/200 batteries). Very happy with it and they do a 48v version as well. The Wakespeed regulator is very flexible and a great piece of kit. In fact I have managed to get

Being able to connect the Wakespeed to the Charge Disconnect signal and drop it's output to float voltage means that there is no sudden load disconnect from the alternator, to damage the diodes.

Alternator 5kW 54V

Wakespeed 500 Alternator Regular for Marine

Great service and very knowledgable.

These are shots from two separate occasions.1604593193015.png

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So with your wakefield alternator controller you can 'upgrade' any existing alternator to an 48V one with added benefits of current control? Or does it only work on specific alternators?

bathnm avatar image bathnm marijn-achterkamp ·

Unfortunately not. The Wakespeed is an intelligent alternator regulator. So the alternator needs to be able to be externally regulated and must be designed for the target voltage. Such an alternator is not cheap, but it is worth it.

Thanks, OK so for your solution I need a new alternator + your wakespeed... Indeeed expensive but might still be worth it. cheaper then a 2nd generator still.

bathnm avatar image
bathnm answered ·

Have you considered an external alternator regulator, something like a Wakespeed 500. This can take a Charge Disconnect signal from the BMS and trigger the alternator to drop to float.

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I think the solution will come through here.

Thanks for sharing.

Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

The best solution is to have the alternator controller limit the alternator, and also to control the alternator controller by the BMS

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Justin Cook - Bay Marine Supply USA avatar image
Justin Cook - Bay Marine Supply USA answered ·

@bite, I'll confess that I don't immediately have a better Victron-centric alternative (other than an Orion DC-DC Converter in the 48/48-8A range), but I will point out that the "80A breaking limit" of the Cyrix at 48v does not mean it's a current limiter.

Just because that's all it can handle doesn't mean that it's going to stop more than that from flowing through it. In this case, I would continue sourcing other solutions, because the Cyrix isn't it.

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@Justin Cook - Bay Marine Supply USA, Thanks for the feedback, I also think that cyrix is not the best solution.

if you have a solution to this problem. I'm open to suggestions ...

@bite, I encourage you to check out @safiery's answer -and products- as they have a much better handle on this exact scenario than I'm used to dealing with!