What is my alternator doing?

[Na Mara]

That is a point newhaul, I’ve only charged from about 70% SOC thus far. In the southern Baltic shore power is ubiquitous and anchorages not so.

I’ll try it from a lower SOC and see what happens. Maybe the slightly lower battery voltage will mean the alt needs to work harder to get the charging voltage to the recommended 13.5V and I’ll see higher field percentages.

[newhaul]

Originally Posted by Na Mara

That is a point newhaul, I’ve only charged from about 70% SOC thus far. In the southern Baltic shore power is ubiquitous and anchorages not so.

I’ll try it from a lower SOC and see what happens. Maybe the slightly lower battery voltage will mean the alt needs to work harder to get the charging voltage to the recommended 13.5V and I’ll see higher field percentages.

Let us know how it goes

[Nicholson58]

Originally Posted by CharlieJ

OP: This is a programming change for the WS500.

Note that per Balmar the continuous rating for their alternators is a max temperature of 85C. And, make sure that the alternator temp sense is at or very near the hottest point on your alternator.

Unfortunately, the hottest point is in the rotor windings, not the case. Better to keep it cool than a burn out. We’ve lost two. I now run at 50%

[Dockhead]

Originally Posted by Na Mara

I checked the charging voltage on the BMS today and it’s 13.5V. Full charged my bank sits at 13.47V. I’m pretty sure that you are right hjohnson. I think the BMS is limiting the alternator to not exceed the recommended charging voltage. Not sure how, or even if it is a good idea to try, to change the charging voltage from the recommended value.

Ballsnall, the alternator merrily puts out 100A when there is a large load on the system. It just won’t charge the batteries at that, which is a bit of a shame.

If you want your alternator to last for more than a year, it's not a shame at all. It's rather doing just what it should.

If you want to charge faster than that you will need a large case real heavy duty, hot rated alternator.

[Epikur]

I think, the batteries can‘t take more current. There is a saturation in the chemistry of lead batteries (actually any battery).

During charging the electrolyt (sulforic acid) on the surface of the lead electrodes is „used up“. It takes time for the electrolyt to replenish by diffusion. That will limit the maximum accepted charging current.

You can‘t exchange a 35A alternator by a 500A alternator and expect to charge the batteries in say 35 A/500A=no time.

[Na Mara]

The other day the batteries were 60% SOC and I ran the alternator. It initially supplied 90% field which slowly dropped to 70% as the battery SOC climbed to 70%. I think the BMS is moderating the charging voltage and pegging the field to keep it at precisely 13.5V. That is probably what it should be doing.

But here is a follow up question: the nominal charging voltage for my LFP batteries is 14.2V and that is the voltage targeted by the multiplus charger and the future renewable chargers that I will be installing. Why then is the BMS restricting the alternator to 13.5V?

[newhaul]

Originally Posted by Epikur

I think, the batteries can‘t take more current. There is a saturation in the chemistry of lead batteries (actually any battery).

During charging the electrolyt (sulforic acid) on the surface of the lead electrodes is „used up“. It takes time for the electrolyt to replenish by diffusion. That will limit the maximum accepted charging current.

You can‘t exchange a 35A alternator by a 500A alternator and expect to charge the batteries in say 35 A/500A=no time.

Actually that is the biggest plus for lifepo4 batteries they can take just about all you can throw at them. My bank is 250ah. My bms limits the charge to 200amps. By my build choice.
The main limiting factor for charging is the manufacturer recommendations and the bms.

[newhaul]

Originally Posted by Na Mara

The other day the batteries were 60% SOC and I ran the alternator. It initially supplied 90% field which slowly dropped to 70% as the battery SOC climbed to 70%. I think the BMS is moderating the charging voltage and pegging the field to keep it at precisely 13.5V. That is probably what it should be doing.

But here is a follow up question: the nominal charging voltage for my LFP batteries is 14.2V and that is the voltage targeted by the multiplus charger and the future renewable chargers that I will be installing. Why then is the BMS restricting the alternator to 13.5V?

What bms do you have ? If owner build
What drop in batteries? If not.

What alternator and regulator?

[motion30]

13.5 v seems a little low when you're saying full charge voltage is 13.47 volts

[newhaul]

Originally Posted by newhaul

What bms do you have ? If owner build
What drop in batteries? If not.

What alternator and regulator?

Just went back and looked at your initial post . Sounds to me like you need to adjust the charge acceptance voltage to 14v . Which is the default for your BMS.
What are your dip stitches set to ( see attached)

[smac999]

by default the lynx bms won't allow a bulk charge if the battery stays over 70% or so. or once a month. which is why it's charging at 13.5v it's probblay in float.

change the rebulk % setting up to 85-90% or whatever it's called. so it goes into bulk at a more realistic soc

[Na Mara]

So now I am totally mystified.

The alternator is now running 100% of field all the time. The only difference is that on the last two outings when it did this I had the engine at 2500rpm instead of the Yanmar recommendation of 2800rpm.

What gives?

Did it have a "run in" protocol in the regulator? Is the temp regulation easier at the slightly lower rpm? I am happy but mystified.

[hjohnson]

Originally Posted by Na Mara

So now I am totally mystified.

The alternator is now running 100% of field all the time. The only difference is that on the last two outings when it did this I had the engine at 2500rpm instead of the Yanmar recommendation of 2800rpm.

What gives?

Did it have a "run in" protocol in the regulator? Is the temp regulation easier at the slightly lower rpm? I am happy but mystified.

Ok, so if it is driving your field to 100% and you’re not getting anywhere near full power out, then something is definitely wrong. I’d check all the wiring between the wakespeed and the alternator field input, in particular look for bad crimps and what not. You might have a high resistance connection somewhere.

Failing that, take your alternator to an alternator shop and have them look at it, if possible. They should be able to tell you if the field is good or not.

[Na Mara]

The batteries are seeing an input of about 1kW minus loads. The rated output at 100% field should be 1200W, so there is a little mismatch but not much. Again, I’m now happy enough but don’t really understand what the earlier behaviour was about.

[rbthorson]

Originally Posted by Na Mara

With my new electrical system I can see in real time exactly what my alternator is doing and I am a bit perplexed.

Its a Balmar 100A alternator that is regulated by a WS500 regulator and it charges a 3x200Ah LFP 12V victron Smart batteries managed by a lynx 500 BMS.

What it is doing is that it is charging at between 60 and 70% of its max capacity (field input is between 60 and 70%) and seems to be targeting an alternator temp of 70C. If, however, I put a big load on the system (boil a kettle through the inverter say), then all of a sudden it goes to 100% output and it doesn't have a problem with allowing its temperature to go all the way into the 90's. I would very much like it to charge at 90-100% and can't really see why it isn't doing that as the temp limit on it is set, according to recommendations if memory serves, to 95C. It seems that the BMS is limiting the changing amps for some reason and I can't figure out why. The batteries can easily take, and regularly do take when we hook up to shore power, 120 charging amps.

So why is my alternator not outputting as expected?

It seems that your alternator is operating as should be expected. You have not mentioned the state of charge of your batteries. The closer the batteries are to fully charged, the less current they will accept at the specified charging voltage.
Lets assume your heating appliance for your kettle is 1,000W. That is 83A at 12V not even taking losses into consideration. The kettle is requiring 83% of the alternator's maximum output and that only leaves 17A to charge the batteries and operate any other equipment powered by 12V. In reality, when heating the kettle you are likely to be discharging the batteries while the alternator is trying to keep up with the heating appliance and the other demands from the 12V system.
If your alternator is maintaining 13.5V at the batteries with no load, it is working properly. If the load goes above 100A the voltage will drop because the alternator cannot provide any more current.