Puzzled by new alternator low output

[LifePart2]

I have just installed a new Delco 24SI 180amp alternator. It came with test results that showed it worked, and produced 111 to 178 amps at 12.8v, the exact current depending on speed. The regulator voltage is at 14.07v according to the bench test.

Having installed it, I am getting just 40 amps from it, which is no better (in fact identical) to what I am getting from my Hitachi 55 amp alternator on the other engine. Both of these are outputting at 13.5v at that current, and both are internally regulated.

So, I am rather disappointed that I am not getting more output from it.

But, here is the kicker. If I increase the revs from idle, the current output goes DOWN instead of up - down to 35 amps at engine speed of 2000 compared to the 40amps at 1000 rpm. When I reduce the engine speed, the current goes back up again.

So, can anyone help me understand:

1) why does the current go down instead of up at faster revs?
2) why am I getting just 40amps (same as my 55 amp alt)
3) what can I do about (2)

I do have a Sterling advanced regulator which was previously connected to an old Leece Neville 90amp alt. But that alternator has now burnt out - probably because it was producing a nice 70amps for long periods (maybe 3 hours) of time. And the engine room blower wasn't working (fixed now). So I am reluctant to connect the Sterling to the new alternator as I don't want to burn this one out too. However this new alternator is large case, hot rated, and should be much more sturdy. And the engine blower now works.

I am using 300aH LiFePO4 batteries, which means they can accept high current charging all the way to full. I am not looking for 180 amps. Just 100 amps and not burning out the alternator would suit me fine. That means I would rarely be charging for longer than an hour.

Suggestions please?

Thanks

Noel

[skipmac]

Hi Noel,

First question, what is the SOC (state of charge) of the batteries when you tested the new alternator? If the batteries were already in a higher state of charge then the alternator will not be dumping full output into a charged battery.

Also I think from your description the new alternator is also internally regulated and if so, it is a dumb regulator and outputs at a fixed voltage. If you plan to use the new alternator as one of your primary sources of battery charging you would do well to go with a setup that uses and external, smart regulator. These are generally programmable so you can limit the output to avoid burning up an alternator by running it at max output for long periods.

I know some alternators can be modified to disable the internal regulation and use an external regulator but not sure if that applies to yours.

[Suijin]

May sound like a dumb question, but are you sure your belt is not slipping? Would potentially explain 1 & 2, particularly 1. Look for glazing on the belt.

I'm assuming your engine is @ 35 hp. That's a pretty big alternator for that engine. Did you add a double belt? If not when it loads up I'd not be surprised if it was slipping. As you up your RPMs, and load up the alt more, if it is slipping it's going to slip more, lowering your output.

[john61ct]

If it's easy take to a pro shop put on a bench and load test it vs specs, especially the rpm output curve.

That big an alt with a big empty bank will load a lot of the engine's HP, install a switch to unload the field current for times when you need it all for propulsion. Best would be an external VR like MC-614 Balmar.

And yes double belts likely not enough, may need to covert to serpentine?

[senormechanico]

+1 for all of the above.
LiFePo4 cells do charge much faster with less current taper at the end, but there still is a bit of taper depending on the final voltage.
I run mine to 13.8.
Solar is my main source.

[LifePart2]

Wow, three answers already! Thanks!

I am pretty sure the single belt is not slipping. It is not getting particularly hot. Nor is the pulley. It is a brand new belt - do they take a little time to settle in? i know I had to retighten it alreay.

The batteries are at about 50% - sitting at about 13v. When full, they sit at 13.2v

Yes it is the 39 hp yanmar. It should be able to handle the hp drawn by the alternator easily. I get that the belt might slip, so I was watching for that. But I don't think it is the case. Also, I had the previous alternator running at 70 amps without any belt problems, also on a single belt. As I said, I am only looking for 100 amps from this one. Even 70 would be good. Being rated much higher than that, it should be able to handle the lower output for long periods.

I know the built-in regulators are not as good but still I am surprised that it is only putting out 40amps. The current is unlikely to be dropping as a result of the internal resistance of the battery, as the LiFePO4 can take high current right up to full charge, unlike the lead acid that gets slower and slower. So I guess it must be the regulator dropping the charge? Yet it is still well below the 14 v set point of the regulator.


Noel

[Suijin]

My point regarding your engine HP was not that the engine was not adequate, but rather that it almost certainly had a single belt. I have a 44 hp Universal, and was told by a mechanic that I highly respect that if I wanted to go bigger than the 80 amp Balmar I put on it I would need to upgrade to a double belt.

If it's slipping it can be hard to see and it might not get anything more than warm; it's still turning the alt, just not as fast as it should.

One easy test would be to crank on the belt tension, temporarily over tensioning it, and run it for a bit and see if your results are any different. If the belt is the issue either your amps are going to go up or the belt is probably going to squeal.

[john61ct]

Originally Posted by senormechanico

LiFePo4 cells do charge much faster with less current taper at the end, but there still is a bit of taper depending on the final voltage.
I run mine to 13.8

That's a **perfect** voltage level for longevity.

Ideal would be to simply STOP when current gets down to about .025C (2.5A on a 100Ah bank).

To verify every once in a while, rest no load or charge for 3 hours, then test for 13.6V (3.4vpc). That's full.

Any "floating", even very low say 13.2, may well be harmful to longevity.

Personally I'd divert the charge output to a stock lead starter is the source can't disable float.

[john61ct]

Originally Posted by LifePart2

I am pretty sure the single belt is not slipping. It is not getting particularly hot. Nor is the pulley. It is a brand new belt - do they take a little time to settle in? I know I had to retighten it already.

If it really isn't slipping, it should be, unless the belt & pulley is something special, a single non-serpentine just won't push the torque of that amp feeding your LFP 150+A, need double just to go a little higher, for that HO likely need serpentine.

Originally Posted by LifePart2

Also, I had the previous alternator running at 70 amps without any belt problems, also on a single belt.

70 no problem.

Originally Posted by LifePart2

As I said, I am only looking for 100 amps from this one. Even 70 would be good. Being rated much higher than that, it should be able to handle the lower output for long periods.

You won't have that level of control without a good VR like the MC-614, see Balmar's "belt manager" and "small engine" mode.

Ordinary VRs just feed as much as the LFP is demanding, to the point some say LFP can burn undersized alts right up.

Originally Posted by LifePart2

Yet it is still well below the 14 v set point of the regulator.

A little too high for maximum bank longevity, 13.8 better. And divert the float to a lead starter.

In any case, if you're sure it isn't belt slipping or pulley ratio, get a marine or auto electrician to bench test the alt and VR, compare to mfg specs.

[Maine Sail]

Originally Posted by LifePart2

I have just installed a new Delco 24SI 180amp alternator. It came with test results that showed it worked, and produced 111 to 178 amps at 12.8v, the exact current depending on speed. The regulator voltage is at 14.07v according to the bench test.

Having installed it, I am getting just 40 amps from it, which is no better (in fact identical) to what I am getting from my Hitachi 55 amp alternator on the other engine. Both of these are outputting at 13.5v at that current, and both are internally regulated.

So, I am rather disappointed that I am not getting more output from it.

But, here is the kicker. If I increase the revs from idle, the current output goes DOWN instead of up - down to 35 amps at engine speed of 2000 compared to the 40amps at 1000 rpm. When I reduce the engine speed, the current goes back up again.

So, can anyone help me understand:

1) why does the current go down instead of up at faster revs?
2) why am I getting just 40amps (same as my 55 amp alt)
3) what can I do about (2)

I do have a Sterling advanced regulator which was previously connected to an old Leece Neville 90amp alt. But that alternator has now burnt out - probably because it was producing a nice 70amps for long periods (maybe 3 hours) of time. And the engine room blower wasn't working (fixed now). So I am reluctant to connect the Sterling to the new alternator as I don't want to burn this one out too. However this new alternator is large case, hot rated, and should be much more sturdy. And the engine blower now works.

I am using 300aH LiFePO4 batteries, which means they can accept high current charging all the way to full. I am not looking for 180 amps. Just 100 amps and not burning out the alternator would suit me fine. That means I would rarely be charging for longer than an hour.

Suggestions please?

Thanks

Noel

Your problem is most likely inaccurate voltage sensing and voltage drop. The regulation circuit positive and negative must see actual terminal voltage of the LFP battery.

There is very little room with LFP for incorrect voltage sensing. Internal regulators are very problematic in this regard unless you can tap into the sensing circuit and correct for any voltage drop between the alt B+ & B- and the LFP pos & neg terminals..

Most of the large Delco's also have a thermal gradient that will cut back regulation voltage if the alt gets to a certain temp. The Hitachi's have the same, hence the 13.5V when hot as opposed to the factory 14.3V +/-.

How were you planning to stop charging when the bank was full at 14.+ volts??

Unless that test bench was measuring the regulation voltage at a very low current your voltage set point could be a bit higher. A Delco 24SI 12V reg is set to 14.2V though some aftermarket regs (re-builders, Chinese knock offs etc.) can be as high as 14.8V. With a 180A 12V 24SI I don't think you have a genuine Delco as they only offer a 160A version in 12V.

[FionaJC]

Batteries only tend to take what they need and most alternators are just adapted (if you are lucky) car and truck versions. I had a similar problem. I could never bring any batter to what I would call "full Charge". They didn't last as long as I expected. I even tested the charge levels with a hydrometer.

The first part of the answer as I fitted a battery monitor the BM1 from NSAS marine. Clipper BM-1 Battery Monitor - Nasa Marine Instruments

I then fitted a charger regulator. I opted for the Adverc. Adverc Battery Management - Product Catalogue Adverc Systems

To top it all off I added a VSR. This waits until the starter battery is charged, when it reaches 13.7 it connects to the domestic and it disconnects when the voltage reaches 12.8 leaving the starter charged and disconnected and the domestic charged.

I now have bliss, - well no worries about charging and low starter batteries anyway.

[seabreez]

Originally Posted by LifePart2

I have just installed a new Delco 24SI 180amp alternator. It came with test results that showed it worked, and produced 111 to 178 amps at 12.8v, the exact current depending on speed. The regulator voltage is at 14.07v according to the bench test.

Having installed it, I am getting just 40 amps from it, which is no better (in fact identical) to what I am getting from my Hitachi 55 amp alternator on the other engine. Both of these are outputting at 13.5v at that current, and both are internally regulated.

So, I am rather disappointed that I am not getting more output from it.

Noel

When bench testing the conditions are deal for loading and the battery voltage is variable on the input side. Having said this when installing on an engine and trying to recreate these conditions is very difficult. To satisfy your self the charging voltage should and will be variable from 13.7 volts to 14.7 volts depending on the condition of the battery. I measure directly at the output terminal of the alternator. Now for the amps you need to set the condition that the alternator will sense that it needs to pump out that amperage. To do this you need to draw 180 amps from the battery for the alternator to pump in 180 amps. This is very difficult to simulate on a boat. On a car or truck you can try and do this by having all accessories on like lights, heaters, air conditioning etc, and even then you still cannot come close to drawing out your amperage rating of the alternator. Conclusion... if the battery voltage is correct during variable speeds of the engine and you get some amperage and you have no noticeable problem like dead batteries... then leave the alternator alone... it is doing it's job. It will adapt to all your variable conditions... especially a 180 amp alternator. On the tug that I operate we have two 60 amps alternators (one on each side) and charge six batteries and never have problems. With an 180 amps alternator you might recover sooner and the benefit of this alternator is that it might heat up less... (a man doing a boy's job).
I rebuilt alternator for 25 years and many times it was simply replacing bearings and educating the customer and understanding when is amperage is ever at maximum.

[Ding Duck]

Hi Noel, perhaps the Regulator of the new Altenator works on a slightly different curve to the existing Hitachi Alt?
As others have mentioned the Altenator will only produce the Amps required depending upon the load. I would suggest if you run the Alt at 1000 rpm (producing approx 40A) and bring in other loads . The Altenator, having a higher terminal voltage will start to deliver Amps to drive these loads. Be mindful of cooling of Altenator at low speeds.
If you have a large load you can 'dump' onto the altenator, may also help to determine if there is belt slip? Obviously, if it makes a squeal, you have some slip. Also, keep an eye out for any excessive rubber dust. This is certainly belt slippage. You may also want to double check the drive pulley on the Altenator is correct for what is installed eg, A or B section belt etc. Wouldn't be the first time people have been caught by this.
Good luck

[john61ct]

Possible to fit a tach driven by the engine itself, compare to the one sensing from the alt?

That will show the slippage with no guesswork at all.

[jreyn1944]

A quote from the Balmar website:
The problem with multiple charging sources is they tend to fool one another. Say your battery is at 12 volts. You start one engine and its alternator begins charging the battery, raising the voltage to 14 volts. When the second engine/alternator starts up it sees not the true State of Charge of the battery (12 volts) but 14 volts from the other alternator. The second alternator thinks the battery is fully charged and puts out the minimum current possible. The result is only one alternator is doing all the work and the other is just coasting. This isn’t damaging but it is inefficient charging. Balmar’s CenterfielderII is designed to solve this problem by acting as a “traffic cop” and combine the output from both alternators.

I have experienced this situation on our twin engine trawler with both engines equipped with 24SI alternators. What happens is that both regulators eventually supply one half of the current into the battery, which results in each alternator supplying about half of what it should be supplying. To fix the problem I modified the alternators to use external regulators, and installed Balmar MC-614 regulators with a Centerfielder. The Centerfielder detects when both alternators are running, and then applies the field current from the starboard alternator to both alternators, thus assuring essentially equal output from both alternators.