Alternator Voltage Regulation or not?

[Mouton]

Hi All
I have a puzzle I'd like to run by you all.
Volvo Penta D2-55. Mitsubishi 115A alternator.
Starter battery directly connected.
600Ah LiFePo house batteries (Renogy 300 x2) behind a Cyrix-Li.
I put a manual switch on the Cyrix thinking it would be nice safety to be able to disconnect the house from the engine when i want to, thinking about lithium safety ultimately but the Renogy management seems to be ok with persistent charge voltage.

I go to try the switch yesterday and things are +/- fine before. I hit the switch, and quickly my starter battery goes north of 15V. Volvo alarms. I shut it down.

Tried starting with them disconnected and i get the alarms.

So...is that regulator done or what?
I am confused how the Li is keeping it out of the red..
Is that just CC/CV charging at work?
So when the lithium ultimately fills up it will disconnect and I go back to over voltage alarms?

What would you do?

TiA
Alex

[Johan Leopard51]

High odds alternator regulator is not working like it should. Not same motor or alternator but recently in my old landcruiser the smell of rotten eggs guided me to find starter and aux battery gassing off at 17V as the old Cruiser has no fancy warnings. I replaced with a 150 or 180 amp Denso that supposedly has temperature compensation so that at idle RPM and flat aux/house you don’t damage the alternator.

[Mouton]

No funny smells yet.
Before adding the switch I had done a test of the system, charging the house batteries from 80% to full. Alt got up to temp but the Mitsu has built in temp regulation that seemed to work great. I got to 100% and left it for a few minutes but didnt push it. Seemed like it did basically a CC/CV charge on its own, except for amperage dropping with temperature.

[wholybee]

The Cyrix is the wrong device to put between a Start and Lithium battery. It should be a DCDC charger. The Cyrix provides over/under voltage protection, which is redundant because the BMS does that as well. But it doesn't provide any current limiting or regulation which is needed to protect your alternator.

I don't know what is wrong with your alternator or if the lack of a proper DCDC has anything to do with it. Or if it was related to the sudden disconnect of the Cyrix. When an alternator outputs too high of a voltage, it is usually because the "sense" wire is disconnected or connected to the wrong place. Example, if the sense wire was connected to your Lithium battery, then when the Cyrix was open the alternator would keep raising voltage trying to get the voltage on the Lithium higher, which could never happen.

Some alternators don't have an external sense wire and it is all internal. In that case, something internal might be damaged.

[Shrew]

Could you elaborate on the exact Cyrix device you have? Their documentation shows a variety of products:

Cyrix-Li-Load: This will disengage when its control input becomes free-floating

Cyrix-Li-Charge: This will connect a battery charger with 3 seconds delay

Cyrix-Li-CT: Charge Controller for LiFePO4 and FLA batteries

Referring too the device as the "LI" confuses things even worse.

I also personally hate that they refer to it as LI (Lithium) which is different than LI-ion (Lithium Ion) and LiFePO4 (Lithium Iron Phosphate). These things are not typically interchangeable.

[Mouton]

Im in a very good position here to eat my hat, but I respectfully disagree.
This is the prevailing talking point on the internet to be sure, but an alternator with temperature regulation does not need DC/DC guarding. I ran the test and successfully charged fully 20% with no blue smoke. Alternator temperatures peaked in the upper 70s (Currenty 63A)

I also think LiFePo batteries clamping off has gotten better in recent years so the protection is not as important going the other way either (But have nothing to back this up really, I have my starter battery as "protection")

[Mouton]

Originally Posted by Shrew

Could you elaborate on the exact Cyrix device you have? Their documentation shows a variety of products:

I have a Cyrix-Li-Ct. The Li is largely to say that the range of voltages to connect are slightly higher, and the signal line is more complex, allowing for explicit disconnect via BMS (or switch like I have)

[FPNC]

IF applicable. Disconnect any shore power battery charger and solar. Regulators do not play well with second and third charge sources.

[Kiwi Dave]

HI

On my previous cat I got the Mitsubishi 115A alternator.s converted to external regulation, used Balmar external regulators to directly change the LiFePO4 house back, then charged the engine start AMGs with Balmar Digital Duo Charge DC-DC chargers.

[Mouton]

Originally Posted by FPNC

IF applicable. Disconnect any shore power battery charger and solar. Regulators do not play well with second and third charge sources.

I did just add a grip of solar but its on the house side of the Cyrix-Li-Ct so it would have been disconnected when I saw the over voltage, and connected when things were working?

[wholybee]

Originally Posted by Mouton

Im in a very good position here to eat my hat, but I respectfully disagree.
This is the prevailing talking point on the internet to be sure, but an alternator with temperature regulation does not need DC/DC guarding. I ran the test and successfully charged fully 20% with no blue smoke. Alternator temperatures peaked in the upper 70s (Currenty 63A)

I also think LiFePo batteries clamping off has gotten better in recent years so the protection is not as important going the other way either (But have nothing to back this up really, I have my starter battery as "protection")

This is true, but the Cyrix still seems redundant to what the BMS does. I'm not sure I fully understand what the point of that device is. I expect maybe it's purpose is for use with Victron branded batteries, with an External BMS and external cutoff device, as opposed to the Renogy drop-ins which are self contained.

Look for where the alternator regulator senses voltage from. Either internal to the alternator, or an external wire, I bet that is where your problem is.

[PippaB]

This exact alternator, in all of its Volvo and other implementations, has been discussed many (many) times on CF.

Where does the yellow voltage sensing wire go? While the alternator is internally regulated, it has a separate small yellow voltage sensing wire. Depending on where it goes it can lead to under or over voltage in various scenarios. By default it goes to the starter post, which is rarely the correct location for multi-battery installations.

In conjunction with the voltage sensing wire, what does the negative wire connection look like? Have you chased it through the entire system, including under the engine to make sure all connections are clean and secure? And the alternator mount itself, which is part of the typical negative circuit?

[Mouton]

Originally Posted by PippaB

This exact alternator, in all of its Volvo and other implementations, has been discussed many (many) times on CF.

Where does the yellow voltage sensing wire go? While the alternator is internally regulated, it has a separate small yellow voltage sensing wire. Depending on where it goes it can lead to under or over voltage in various scenarios. By default it goes to the starter post, which is rarely the correct location for multi-battery installations.

In conjunction with the voltage sensing wire, what does the negative wire connection look like? Have you chased it through the entire system, including under the engine to make sure all connections are clean and secure? And the alternator mount itself, which is part of the typical negative circuit?

Aha! This is exactly it. Sense wire was on the wrong side of the relay, so with it turned off the sense wire was effectively open! Thank you

It was the abundance of penta/mitsubishi threads here that got me to join. Heres to one more =)

[Jweyndling]

I have the same engine and alternator and 1200 Ah of Li PO4 batteries. I use a Balmar 6018 external smart regulator with a temperature sensor attached to shut things down if alternating get as too hot. Yiu can also add a Balmar APM 12 which will shut the alternator down if the batteries get disconnected. You have to get your alternator modified to use the Balmar but it just involves soldering two wires to the brush connectors I believe. I then have a Victron battery isolator which allows the alternator to charge the start battery and the Li house battery

[CarinaPDX]

With the V-P Mitsubishi alternator I recommend using the Nordkyn Electronics VRC-200 regulator. It was designed to work especially with that specific alternator, and for lithium batteries although works for lead as well.

When I read the first post I thought that the sudden disconnect probably spiked the alternator output voltage, although I was thinking that the alternator could have been putting out maximum current into the lithium batteries and when disconnected from them the lead battery's high internal impedance and likely full charge wouldn't be able to suddenly absorb the current. Of course disconnecting the sense wire might cause the regulator to go to maximum output but I am not at all certain of that. Anyway, changing the alternator output circuit while it is operating is fundamentally a bad idea; best to shut it down before re-configuring.

As good as the Mitsubishi alternator is, I would not use it to directly charge 600Ah of lithium batteries without an external regulator that limits current to something much less than 115A. Nordkyn's engineer told me that the internal regulator does a very good job of sensing temperature and limiting output, so I guess that is what has kept it from overheating, but better to just set a hard current limit in an external regulator such as the VRC-200. [Edit: the VRC-200 works with the internal regulator, not as a replacement, so all of the protections still function. That is why I think that it is superior to other regulators, which do not have internal temperature sensors inside the alternator.]

Greg