Low charge current from alternator, what am I missing?

[sailorboy1]

Originally Posted by Stu Jackson

Internal or external regulation? Voltage setpoint?


Seem to be important figures to include, if you would, please. Thx.

Well it would ramp up. But if at a low soc that be charging at only 13.6v still the batteries would take all a 100 amp charger could put into them till around 85% soc.

Nothing new with this and why in old days before solar cruisers operated in the50-85% range as acceptance would drop after that.

[GILow]

Well, quite a diversity of ideas about this one, thank you all.

Just some points to clarify:

1. To be totally clear there were no significant loads on the batteries at the time I tried this experiment. So the alternator had nothing to do other than charge the batteries. Now the engine battery might have been accepting a bit of charge and the battery monitor would not have picked that up, but I would be surprised if it were taking 15 amps on its own given it was in parallel with the house bank at that point. Possible, but unlikely.

2. In deference to the point above, I will see if I can get an actual measure of alternator output to be sure.

3. The additional load test is a good idea. I will try putting the kettle on, as I know exactly how much if draws and this will surely eliminate or confirm the voltage set point as the issue.

4. As SB has noted, these batteries should accept 100 amps or more at this SOC. His experience has been borne out by others with the same sized T105 bank. Even smaller banks of 4 T105s were accepting more than this.

5. I will have a closer look at the alternator. It was not a special option, just what Beta shipped as standard, but given everything else they got wrong I would be wise to double check.

6. Belt tension is good.

Thank you all for the ideas so far. You’ve given me plenty to get on with.

I will report back on the results as they are determined.

Matt

[Thumbs Up]

Are you engine charging with the solar also charging? (you would need to add the two to get the full acceptance rate).
When you parallel a fully charged engine start battery to a hungry house bank it could affect the acceptance rate because a high CCA battery can dump a lot of it's charge very quickly (much quicker than it can recharge). If you had a 1-2-both switch you could bypass this concern.

[Wotname]

Originally Posted by GILow

Well, quite a diversity of ideas about this one, thank you all.

Just some points to clarify:

1. To be totally clear there were no significant loads on the batteries at the time I tried this experiment. So the alternator had nothing to do other than charge the batteries. Now the engine battery might have been accepting a bit of charge and the battery monitor would not have picked that up, but I would be surprised if it were taking 15 amps on its own given it was in parallel with the house bank at that point. Possible, but unlikely.

2. In deference to the point above, I will see if I can get an actual measure of alternator output to be sure.

3. The additional load test is a good idea. I will try putting the kettle on, as I know exactly how much if draws and this will surely eliminate or confirm the voltage set point as the issue.

4. As SB has noted, these batteries should accept 100 amps or more at this SOC. His experience has been borne out by others with the same sized T105 bank. Even smaller banks of 4 T105s were accepting more than this.

5. I will have a closer look at the alternator. It was not a special option, just what Beta shipped as standard, but given everything else they got wrong I would be wise to double check.

6. Belt tension is good.

Thank you all for the ideas so far. You’ve given me plenty to get on with.

I will report back on the results as they are determined.

Matt

Yep, you have some more investigative work ahead of you .

I can't help much with the your expected battery acceptance current at 70% SOC but I suppose it you allowed the SOC to drop to 50% or less, you could be sure they should accept all the amps the alternator is willing to supply.

Regarding the alternator, the model number should allow research on the expected set point voltage (and max current) as well as any automatic current derating due internal temperature build up.

With such information, it should be reasonably straightforward to determine the health of the alternator as well as decide if anything in your battery charging arrangement needs 'fixing'.

[Dsanduril]

Matt,

if you want to get to the bottom of this simply it's time to crawl into your engine room with your voltmeter while watching out for all the spinning doo-dads and whirling thingamabobs.

Measure the voltage between the B+ output on the alternator and the alternator case. This is the voltage the alternator is actually putting out. If there is a separate voltage sense wire then measure from that connection to the alternator case - this would then be the voltage the alternator is controlling to (otherwise it is the previously measured B+ -> case voltage). Use the same voltmeter to measure voltage at the battery (to remove any discrepancies from using different measuring tools).

Case A - Voltage at alternator = voltage at battery (IMO this is less likely). Then your problem is 100% regulation and you have to deal with swapping out a regulator.

Case B - Voltage at alternator > voltage at battery (IMO most likely), then you are losing voltage in your wiring/connections. Remember E/I=R. From what I can surmise online Beta delivers the Iskra IA0883 internally regulated to 14V. If you measure 14V at the alternator then when getting 45A you are losing 0.4V. 0.4V/45A = 0.009Ω. A whopping 10mΩ of resistance in your wiring and connections can result in exactly what you see. In this case you could possibly chase wiring for some improvement, but your probably really again at the regulator stage.

The following is supposition:
I can't find a manual for the Iskra, but in pictures it looks like the "internal" regulator is mounted on the exterior of the case, which makes swapping it out pretty simple. It also looks like there is possibly a separate voltage sensing wire connected (and delivered with a jumper to B+ as many are). In that case one cheap workaround (which I have done on my Mitsu alternators so not just speaking hypothetically) is to install a diode in the sense line. If you find a diode with a forward voltage drop of 0.5V that converts your 14V to 14.5V and costs about $1.

[Edit]

Looks like probably an Iskra AAG Compact is the most likely family, two regulator options, found these specs:

[GILow]

Great stuff here, thank you. Just letting you know I am reading and absorbing.


I will take due care of spinny bits!

Originally Posted by Dsanduril

Matt,

if you want to get to the bottom of this simply it's time to crawl into your engine room with your voltmeter while watching out for all the spinning doo-dads and whirling thingamabobs.

Measure the voltage between the B+ output on the alternator and the alternator case. This is the voltage the alternator is actually putting out. If there is a separate voltage sense wire then measure from that connection to the alternator case - this would then be the voltage the alternator is controlling to (otherwise it is the previously measured B+ -> case voltage). Use the same voltmeter to measure voltage at the battery (to remove any discrepancies from using different measuring tools).

Case A - Voltage at alternator = voltage at battery (IMO this is less likely). Then your problem is 100% regulation and you have to deal with swapping out a regulator.

Case B - Voltage at alternator > voltage at battery (IMO most likely), then you are losing voltage in your wiring/connections. Remember E/I=R. From what I can surmise online Beta delivers the Iskra IA0883 internally regulated to 14V. If you measure 14V at the alternator then when getting 45A you are losing 0.4V. 0.4V/45A = 0.009Ω. A whopping 10mΩ of resistance in your wiring and connections can result in exactly what you see. In this case you could possibly chase wiring for some improvement, but your probably really again at the regulator stage.

The following is supposition:
I can't find a manual for the Iskra, but in pictures it looks like the "internal" regulator is mounted on the exterior of the case, which makes swapping it out pretty simple. It also looks like there is possibly a separate voltage sensing wire connected (and delivered with a jumper to B+ as many are). In that case one cheap workaround (which I have done on my Mitsu alternators so not just speaking hypothetically) is to install a diode in the sense line. If you find a diode with a forward voltage drop of 0.5V that converts your 14V to 14.5V and costs about $1.

[Edit]

Looks like probably an Iskra AAG Compact is the most likely family, two regulator options, found these specs:

Attachment 237580
Attachment 237581

[Wotname]

Originally Posted by GILow

Great stuff here, thank you. Just letting you know I am reading and absorbing.


I will take due care of spinny bits!

Let us know when you float...

[GILow]

Originally Posted by Wotname

Let us know when you float...

Six or seven hours of motoring and I didn’t even make it to absorption.

Current had tailed off to 14 amps by my first stop (four hours of motoring) and the battery monitor reckoned I was at 100% SOC (not a super smart monitor) and the last three hours of motoring saw around 10 amps when I actually had a chance to check.

Checking with the Victron controllers now, they reckon maximum voltage reached was 14.3 v and the solar spent nine hours in bulk.

I was too pressed for time to make any of the measurements I wanted to make, plus I seriously had my hands full navigating that unmarked channel for most of the trip, but I’ll set things up to monitor it all better tomorrow. (However, tomorrow actually looks like good sailing weather so I may not have to motor.)