Merged LiFeYPO4 1000Ah Winston prismatic cells and all electric galley...

[hellosailor]

arsene-
You might think you have a Hitachi alternator. But unless it was bought in a retail box that just said "Hitachi" on it, it was built to a price and a spec for a contract customer, typically an automaker. So typically it would not have any temperature compensation. That doesn't mean yours doesn't.
I once asked a simple technical question of one of the Japanese alternator makers, and their only reply was "That information is customer proprietary, you would have to ask the customer" who of course was the car maker, who would gladly sell me a new car but had nothing to say about alternator technology.
Which leaves you to either contact Hitachi with a specific model number, or try testing it yourself. All alternators typically have a maximum rating (which is the 80A number you have) and a lower continuous duty rating, which might well be half of that.
Put something on the alternator primary output to measure the current it is supplying, then fire it up with the heaviest load you can. See what it puts out, and use an IR thermometer to measure the diode temperature, or the case temperature close to the diode frame. After 10-20 minutes you should see the temperature get much higher than ambient, and then the question is, does the output also drop. Odds are it will.
Easier to try asking Hitachi first, I think.
Unlike the Delco's and Leece Neville, the Japanese alternator makers don't seem to enjoy publishing their data sheets online, but with the specific model number, you might find one anyway.

[john61ct]

Most stock alt setups, if they have overtemp protection at all

just drop voltage, in effect stop charging when the diodes get too hot.

My experience is that only the added-value VRs designed for deep cycle charging as above

Keep charging at the proper voltage setpoint, and just reduce current output to lower the loading and temperature.

In modern vehicles designed to maximize fuel economy, the ECU may be the VR, in which case only a B2B charger will allow for satisfactory charging of a deep cycle bank from the alternator.

And not void the warranty.

[hellosailor]

john-
wrt alternators designed for cars? I got lucky and got the chief engineer for a major battery maker on the phone one day. At one point he said "You have to remember, the alternator in a car is not designed to charge batteries." Huh? "No, it is designed to NOT OVERCHARGE an SLI battery, which is never designed or intended to go below 90% state of charge. And if you're taking an eight hour highway trip, you don't want the alternator to overcharge it for all that time."
So, yeah. Unseen priorities. And AAA claims the average car owner only gets three years out of a battery--which is being charged by one of those alternators.
But in cars they also have new tricks, like the ECU shutting down the alternator entirely if the battery is charged and the load is low (i.e. highway daytime driving) and then only starting it up again when the battery starts to dip. This, because you get better mpg when the alternator load is removed.
All invisible to the poor rube behind the wheel.

Makes you appreciate the Pardeys' philosophy on all that stuff, doesn't it?

[john61ct]

Makes **me** appreciate Sterling B2B chargers.

Even as a Quaker, I do not aspire to that level of sacrifice voluntary simplicity.

[CatNewBee]

The primary task of the alternator is to supply the power for lights and all other electric stuff on the way in a vehicle, usualy even calculated smaller as the potential highest load, supposing the battery will help to overcome peak demands.

The alternator needs only recharge what the starter has consumed, the board voltage is somewhere between 13.8 and 14.2V depending on the load.

This is a power source as others are, but not for clean 3-stage battery charging / maintenance. Completely fine for FLA start batteries, they are overdimensioned to crank in cold conditions, you'll barely notice a 40% degradation, because the alternator supplies everything once the engine is running. Completely different demand.

[CatNewBee]

What I know from RV cruising, most alternators, ACR and separator relays died, when people try to use a pretty large inverter of a pretty small FLA / AGM board battery bank and to not run into a voltage drop cut-off, run the engine to help the battery with the alternator.

Then there is a voltage drop below 11V, the alternator, the start battery are connected to the board battery and significant currents were drawn, ending up overwhelming of the electric system, usually intended to provide 10..20A charge current (relays rated for 50..70A) and thin wires.

With LFP, this is a +/- game. LFP are mostly unimpressed by inverter loads, so a full LFP bank will not have a significant voltage drop dragging high power from the start battery and alternator - but an empty LFP will be a significant load to the alternator for a long time (11.2..11.6V at cell voltage of 2.8...2.9V). And this of course can kill everything inbetween.

Using a ACR is not helpful either, the engine starts, the start battery quickly rises over 13V, the ACR kicks in and then a huge current drags on all components...

I guess, the least stressfull operation mode is to keep yor battery above 50% SOC, then it has about 13.2...13.4V, safe for the alternator and the other components. If you need to recharge from 20%, use a generator and regular battery charger to a voltage above 13V, then you can use the alternators too to get more Amps in quicker.

The advice in the forum to cycle the battery at low SOC can be a problem for the alternators.

[john61ct]

Sorry, truly not trying to be argumentative, but I fail to see the point of the last couple posts.

Describing as-built limitations of stock setups does not say anything about how a properly designed and built system performs.

Inverters are hardly an important factor, especially when AC current is not.

Big enough lead banks can also drive high current loads,

yes LFP is lighter and will do a better job holding high current discharge volts high at a lower AH capacity.

Alternators can deliver hundreds of amps for extended periods, and LFP can accept that output faster, allowing reduced runtimes.

[CatNewBee]

Hi John,

it was about potentially dying alternators because of LFP.
My experiance shows little issues when the battery is not too deep discharged.

I also tried to explain when problems come up and what mistakes lead to system damages, because the initial design has not considered some intuitive usage patterns.

A B2B charger effectively controls and limits this effects, thats why many system integrator do recommend using one between the board electric and the house bank. Usually they are designed to boost charging of a FLA house battery, with LFP they are an effective and desireable charge current limitation.

[john61ct]

Originally Posted by CatNewBee

it was about potentially dying alternators because of LFP

Again, not a problem when designed properly

A big alt that can produce all the amps the bank demands for many hours if needed

and / or a good VR to manage setpoints and heat issues.

or simply use any old stock alt setup and as you say, put a Sterling BB DCDC charger in between to control things.

Or another make, no need for any charge source to be designed for LFP, it just needs user programmability of setpoints.

I don't see how bank SoC pertains with LFP?

And what does "board electric" mean?

[CatNewBee]

I was referring to RV with similar issues, the board electric is a term for all car related installations - the start battery, alternator are used to supply all safety and driving power demands, the house batteries have a separate circuitry for the living space. Both systems are usually part-time interconnected for charging while driving.

On vessels, there is a different philosophy / setup, the house bank drives all the electric systems necessary for sailing, while only the start battery is separated to ensure the engine can be cranked at any time, even if the house battery bank is near empty.

[john61ct]

The US "RV" market holds little worth emulating. I use the same devices and design philosophy on land vehicles as for boats. Same with off-grid non-mobile dwellings.

Load circuits are separated by priority, how essential, with different LVD setpoints.

Alt goes to House, actually Main vs Reserve banks, no dedicated Starter batts.

When space is very limited, just one bank, with a Reserve subset isolated as SoC drops.

Thanks for explaining, US English vs Brit / commonwealth differences are still large in auto / mechanicals.

[Username25]

Originally Posted by CatNewBee

the start battery is separated to ensure the engine can be cranked at any time, even if the house battery bank is near empty.

You may crank an engine, but how surprised I was then charge regulator was dead due to house battery low voltage...

[arsenelupiga]

Originally Posted by CatNewBee

Hi John,

it was about potentially dying alternators because of LFP.
My experiance shows little issues when the battery is not too deep discharged.

I also tried to explain when problems come up and what mistakes lead to system damages, because the initial design has not considered some intuitive usage patterns.

A B2B charger effectively controls and limits this effects, thats why many system integrator do recommend using one between the board electric and the house bank. Usually they are designed to boost charging of a FLA house battery, with LFP they are an effective and desireable charge current limitation.

What is your current thinking re alternators ? I have done bit more research and there is no temp protection in alternators.

I do not use engines much, especially not for charging, so really not interested in complete solutions but need to be able to charge in emergency. One way to do it, is simply finding revs at which alternator produces roughly 50 % ~ 40A. Else manually switch off alternator to house battery charging.

[CatNewBee]

Hi,

in my setup, the alternators will be disconnected based on SOC, however during my passages with very little wind I was motoring for many hours day and night on one engine and my charge regime does connect the alternators for a long time to the LFP with no issues at all.

The Lagoons are built that way, that the alternator outputs go to a FET power distribution device, that delivers separate current to the start battery and the house battery. Disconnecting the house battery does not harm the alternator, it still runs under load charging the start battery.

The load from my LFP bank to the alternator was not too bad, there were between 30..40A coming from the alternator to charge the battery. I guess this is due to the higher voltage the LFP batteries have above 50% SOC.
Running both engines produces around 80A to the LFP. We run one engines at a time between 1500 and 2000rpm to save fuel running at 5kn SOG, also once a day we run that engine with 3000rpm for 5-10min to clean it up. Average consumption is 1.6 l/h.

I would allow a permanent connection to the house bank, the alternator seem not to exceed the critical voltage to trigger the BMS protection, but I prefer not to over-strech it and turn off legacy sources for two reason. I have plenty of solar, that can take care of the remaining 5% charging to the LFP, it is even better to not push it too high. The solar absorption is set to 15 minutes at 14.2V (14V at the battery - 3.500V per cell) allowing some balancing, then it goes to float at 13.6V (13.5V at the battery / 3.375V per cell), what lets the battery rest most of the time during the day without a charge current - but supplies the house with solar energy.

The alternator would hold the battery at 14V+, I do not think it is necessary - it won't trigger the BMS OVP (3.65V threshold or 14.6V), but it is an unnecessary stress for the battery. Also while disconnecting the house bank, the voltage can rise quicker giving the full power and voltage for a absorption to the start AGM battery.

I have no concerns burning my alternators with that load pattern - compared to what the former FLA bank has used.

[john61ct]

Originally Posted by arsenelupiga

there is no temp protection in alternators

Poppycock. Most do so, just not well.

Perhaps some vehicle you have looked at does not allow for modification?

But on 99.99% of boats, the existing alternator can be adapted and fitted with an external voltage regulator that offers temp protection.


> I do not use engines much, especially not for charging, so really not interested in complete solutions but need to be able to charge in emergency.

In other words, you don't want to spend the money.

> One way to do it, is simply finding revs at which alternator produces roughly 50 % ~ 40A.

Actually lowering rpm can make overheating worse, since the alt's fan is more effective at higher rpm.

The key is reducing the amps demanded by the loads.

A DCDC / B2B charger does that, without changing the alt setup.

> Else manually switch off alternator to house battery charging

Yes, either isolate the LFP from the alt

or stop the alt charging via a kill circuit on the VR field current.

Either can easily be automated based on temp