Why is my alternator only producing 30amps?

[Otter]

This is a weird one on a new to me LM30. Volvo Penta 2030 with the alternator going to a three way split charge jobbie to house bank, starter and thruster/windlass battery. The house bank is 330amps in total, all new. The starter and windlass batteries were fully charged.

Running the engine the last few days the NASA battery monitor said there was never more than 30amps going into the house bank, even for example after 18 hours of fridge, lights, iPad, Eberspacher heater etc etc. Is it possible that the split charge device is limiting each of the three banks to 30amps and that even if the engine and thruster batteries are full, never more than 30amps of the alternator can go to the house bank? If so that’s bananas and what do I do about it?

 

[geem]

60A alternator?

 

[Otter]

60A alternator?

Yes at least - should put 50+ Amps into a moderately depleted bank?

 

[Tranona]

This is a weird one on a new to me LM30. Volvo Penta 2030 with the alternator going to a three way split charge jobbie to house bank, starter and thruster/windlass battery. The house bank is 330amps in total, all new. The starter and windlass batteries were fully charged.

Running the engine the last few days the NASA battery monitor said there was never more than 30amps going into the house bank, even for example after 18 hours of fridge, lights, iPad, Eberspacher heater etc etc. Is it possible that the split charge device is limiting each of the three banks to 30amps and that even if the engine and thruster batteries are full, never more than 30amps of the alternator can go to the house bank? If so that’s bananas and what do I do about it?

The amount of amps is determined by what the battery can absorb NOT what it is capable of producing. You don't say what size your bank is but 30A is high unless the bank is large or the SOC is low. You will get higher absorption with low SOC but once you get over 80% it tails of. AGMs generally have higher absorption rates than LA - 35-40% maximum compared with 20-25% for FLA. These are however maximum for flat batteries so when you are only "topping up" absorption will maybe half that. I don't think I have ever seen a charge as high as 30% on a 270Ah bank. After an initial 25A when first starting the engine it typically falls to 12-15A and once at absorption cycle down to 1-2 A.

So nothing weird at all. Lithium will take much higher charge rates but even then unless you have a large bank it is normally limited to 30A as any higher means you have to run the engine at high revs and risk overheating the alternator. Clearly if you change to a 100A alternator as on the later D1 engines you can up the charge rate for lithium, but even then 50A is normally the limit. Fitting a larger alternator to your existing set up won't help and anyway you would need to change the pulleys and belts to deal with the higher outputs. One sensible move would be to fit some solar which reduces the net usage and ensures the batteries are always fully charged when you are not there. Plugging into shorepower achieves similar but does not help when at anchor and consuming.

 

[rotrax]

Yes at least - should put 50+ Amps into a moderately depleted bank?

I would not hold your breath on that!

So many things can affect theoretical output under ideal conditions to what happens in real life.

We had a 110Amp Balmar with the Balmar 'Smart Regulator', fitted as OE by Island Packet.

44O AH AGM house bank, two fridges running 24/7 when we were aboard, often a Dometic 40 litre freezer box too.

Never saw more than 35 amps going into the house bank. As we were never short of battery power, even pre our modest Solar install, never considered it an issue. It was enough to keep everything up to scratch.

If it aint broke, dont fix it!

 

[Otter]

The amount of amps is determined by what the battery can absorb NOT what it is capable of producing. You don't say what size your bank is but 30A is high unless the bank is large or the SOC is low. You will get higher absorption with low SOC but once you get over 80% it tails of. AGMs generally have higher absorption rates than LA - 35-40% maximum compared with 20-25% for FLA. These are however maximum for flat batteries so when you are only "topping up" absorption will maybe half that. I don't think I have ever seen a charge as high as 30% on a 270Ah bank. After an initial 25A when first starting the engine it typically falls to 12-15A and once at absorption cycle down to 1-2 A.

So nothing weird at all. Lithium will take much higher charge rates but even then unless you have a large bank it is normally limited to 30A as any higher means you have to run the engine at high revs and risk overheating the alternator. Clearly if you change to a 100A alternator as on the later D1 engines you can up the charge rate for lithium, but even then 50A is normally the limit. Fitting a larger alternator to your existing set up won't help and anyway you would need to change the pulleys and belts to deal with the higher outputs. One sensible move would be to fit some solar which reduces the net usage and ensures the batteries are always fully charged when you are not there. Plugging into shorepower achieves similar but does not help when at anchor and consuming.

Original post says 330amp domestic bank. I would have guessed it had used about 110amps by the time we started charging.

What caused the confusion is that each of the four times we charged it only ever showed 30amps max.

 

[Otter]

I would not hold your breath on that!

So many things can affect theoretical output under ideal conditions to what happens in real life.

We had a 110Amp Balmar with the Balmar 'Smart Regulator', fitted as OE by Island Packet.

44O AH AGM house bank, two fridges running 24/7 when we were aboard, often a Dometic 40 litre freezer box too.

Never saw more than 35 amps going into the house bank. As we were never short of battery power, even pre our modest Solar install, never considered it an issue. It was enough to keep everything up to scratch.

If it aint broke, dont fix it!

Thank you that’s very reassuring to know

 

[Tranona]

Original post says 330amp domestic bank. I would have guessed it had used about 110amps by the time we started charging.

What caused the confusion is that each of the four times we charged it only ever showed 30amps max.

Sorry I saw that but the 270 was my boat with 115A alternator. I used that to show that a larger alternator does not make any difference.

110A out means SOC is well above 50% so acceptance rate will be much lower than the maximum. 30A is 10% roughly and quire normal.

 

[Otter]

Sorry I saw that but the 270 was my boat with 115A alternator. I used that to show that a larger alternator does not make any difference.

110A out means SOC is well above 50% so acceptance rate will be much lower than the maximum. 30A is 10% roughly and quire normal.

Thank you

 

[BabaYaga]

I would have guessed it had used about 110amps by the time we started charging.

As already mentioned, the relatively high state of charge explains the charging current seen.
For comparison, below is over 50 A going into my well depleated AGM house bank of 270 Ah. 70 A alternator and the engine running at about 2 000 rpm. Battery voltage just before charging began was 12,27 V with all loads turned off, so probably a SOC of around 30 percent or so.
As can be seen from the low voltage reading, the charging is clearly in bulk phase.

 

[William_H]

So many factors will limit the charge from an alternator in to LA batteries. To get a large charge in to batteries will usually require 14 .5 volts or so. Your alternator may not be able to maintain 14.5 volts at the high current you hope for. (alternator claimed rating)
Alternator output is determined by alternator RPM (engine speed and pulley ratios) and may be temperature limited. Then there is the wiring and the splitter which may limit current flow. I would not imagine your splitter will deliberately limit current flow but may provide some restriction. (all assuming it is a no volt drop splitter)
So your 30 amps actual delivery might be good. ol'will

 

[VicS]

This is a weird one on a new to me LM30. Volvo Penta 2030 with the alternator going to a three way split charge jobbie to house bank, starter and thruster/windlass battery. The house bank is 330amps in total, all new. The starter and windlass batteries were fully charged.

Running the engine the last few days the NASA battery monitor said there was never more than 30amps going into the house bank, even for example after 18 hours of fridge, lights, iPad, Eberspacher heater etc etc. Is it possible that the split charge device is limiting each of the three banks to 30amps and that even if the engine and thruster batteries are full, never more than 30amps of the alternator can go to the house bank? If so that’s bananas and what do I do about it?

What is this three way split charge jobbie ?

If it's a diode splitter is the alternator battery sensed ( and sensing the house bank). If not then perhaps it should be ,

Or do you in fact have a modern low loss device such s a Victron Argodiode or Argofet