HELP...Intermittent start battery charging!

[davenrino]

I have a Yanmar 3YM20 and 150A alternator with 91 hours on them. I have 2 Group 27 deep cycle batteries in parallel for the house and a Group 27 Start battery. They are all FLA installed three years ago and well maintained.

Yesterday the engine started but the engine panel buzzer and Batt light remained on 3.6 (batt voltage) on the engine panel as pictured in the bottom 2 pictures.


Power from the alternator goes to an Isolator having the top 2 pictured lights after a normal start and 14.2v showing on the engine panel.

The buzzer and light only stay on after about half of the starts.

Any ideas what the problem may be?

[Stu Jackson]

Any time anything electrical is intermittent, it is 99% of the time a connection. Otherwise it's an equipment issue.

[smac999]

13.6v is charging and a battery light certainly should not be coming on at 13.6v

in the 2nd picture only one battery is charging with one light on. if only the house is charging then you mixed up the 2 battery cables on the isocharge.

I've had a lot of the proisochargers fail.

[Dsanduril]

The ProIsoCharge is telling you what is going on. In the upper picture all three upper blue LEDs are on indicating the charge is being sent to all connected batteries.

In the second photo the red “priority charge” light is on and only the top upper blue LED is on indicating that the ProIsoCharge has separated the batteries and only the battery connected to #1 is getting charged. I’m guessing that’s not the start battery and so the instruments set off the alarm. Alternatively, the start battery is #1 and there is a draw greater than the alternator’s output, dropping the voltage. Solenoid not opening properly on the starter? Stuck glow plug relay (if the engine has them - I’m looking at the electrical side)? Low alternator output? (field problem through ignition)?

One bank is attempting to discharge another. This can happen when a large load such as an inverter or bowthruster is operating on its connected bank and due to high amperage draw, the neighboring battery banks are being discharged. The ProIsoCharge will isolate the discharged bank and direct charging to that bank only until it reaches 13.3V. The ProIsoCharge will then begin charging normally, beginning with the start battery.

Either way, it is an indication that there is a load somewhere that exceeds the alternator output (or a faulty ProIsoCharge thinks so).

Or maybe, as Stu said, a bad connection (probably on the negative/common side) is affecting the measurements made by the ProIsoCharge.

[davenrino]

Originally Posted by Stu Jackson

Any time anything electrical is intermittent, it is 99% of the time a connection. Otherwise it's an equipment issue.

I agree, but I have double checked all connections.

[davenrino]

Originally Posted by smac999

13.6v is charging and a battery light certainly should not be coming on at 13.6v
My normal charging volts are 14.2-14.4.


in the 2nd picture only one battery is charging with one light on. if only the house is charging then you mixed up the 2 battery cables on the isocharge.
The one light that is on is for Bank #3 and I don't have a Bank #3. Bank #1 is the stater and Bank #2 is the 2 house batteries. I think we can rule out incorrect wiring, as it has worked flawlessly for the 3 years since it was installed.


I've had a lot of the proisochargers fail.
Were the indications of failures similar to mine? I already ordered a new proisocharger as it is #1 on my possible culprit list.

Thanks for the reply

[davenrino]

Originally Posted by Dsanduril

The ProIsoCharge is telling you what is going on. In the upper picture all three upper blue LEDs are on indicating the charge is being sent to all connected batteries.

In the second photo the red “priority charge” light is on and only the top upper blue LED is on indicating that the ProIsoCharge has separated the batteries and only the battery connected to #1 is getting charged. I’m guessing that’s not the start battery and so the instruments set off the alarm.

The uploaded picture is not very clear and the top light is actually Bank #3 which has nothing connected to it. Probably why the No Charge light comes on. The bottom blue light is on indicating power coming from the alternator.

Alternatively, the start battery is #1 and there is a draw greater than the alternator’s output, dropping the voltage. Solenoid not opening properly on the starter?
Possibly but only the starter and windlass are connected to the start battery.

Stuck glow plug relay (if the engine has them - I’m looking at the electrical side)?

No glow plugs.



Low alternator output? (field problem through ignition)?
The altermator puts out 14.2-14.4v when I don't get the light.


Either way, it is an indication that there is a load somewhere that exceeds the alternator output (or a faulty ProIsoCharge thinks so).
I am leaning towards a faulty ProIsocharge so new one arrives Monday.


Or maybe, as Stu said, a bad connection (probably on the negative/common side) is affecting the measurements made by the ProIsoCharge.

Thanks for your thoughts.

[CharlieJ]

I am late to the party but I would load test the house batteries to ensure they are still behaving as FLA batteries and have not become ballast!

No load tester-swap house and start batteries on the isolator and see what happens.

[davenrino]

Originally Posted by CharlieJ

I am late to the party but I would load test the house batteries to ensure they are still behaving as FLA batteries and have not become ballast!
I am planning to load test the start battery today. Am I correct in thinking that the charge light on the engine panel should only come on if the start battery is not receiving a charge or will it also come on with no charge to the house bank?


No load tester-swap house and start batteries on the isolator and see what happens.

Thanks for your suggestions.