Alternator output?

dgadee

dgadee

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Had lowish amp output from new engine installation last year. Thought it was remedied by sorting bad connections, but now not sure.

At cruising speed (2.5k) output to mid charged battery (70%?) was 11a and voltage at battery 13.6v. Engine panel said around 14v coming out of alternator.

11a seems very low from a 120a alternator. Is that possible? Do I still have wiring problems?

Electrons are one of my many Achilles heels.

Would an alternator to battery charger help? Not sure what is required. Onboard 4 or 5 months a year, 320ah battery, 100 watt solar panel (no sun here at present - all back home). Eu20i generator and Sterling 60a charger. Fridge only real consumer of power.
 
dgadee said:
11a seems very low from a 120a alternator. Is that possible? Do I still have wiring problems?
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120A is the theoretical maximum current the alternator can deliver, which is only achieved at higher revs. However, an alternator can only supply the current which a battery bank is able to accept. If your battery bank was 70% charged, you won't see a huge current going into it. You could increase the charging current by increasing the charging voltage, using a "smart" regulator or an Alternator-to-Battery charger. You should aim for 14.4v at the battery terminals. If you are losing 0.4v between the alternator and the batteries, you should perhaps check/upgrade the wiring.
 
It sounds about right,a higher amp alternator will make little difference when the batteries are nearly fully charged.
 
The voltages that you quote seem rather low, with considerable drop between alternator and battery.
A modern alternator should output at least 14.2v measured at the output terminal. The charging current will be what the battery can take at the voltage it is seeing, hence it's also on the low side.
An A to B charger might help, at a cost, but I'd investigate the cause of your alternator voltage readings first.
 
I remade the connections (35mm cable) to earth and starter. The original positive from the alternator to positive on starter seems pretty puny (16mm?) Would that be a problem with voltage drop.

Not sure where any other voltage drop might be - only the on/off switch and I don't know if it can be opened to clean contacts.
 
dgadee said:
I remade the connections (35mm cable) to earth and starter. The original positive from the alternator to positive on starter seems pretty puny (16mm?) Would that be a problem with voltage drop.

Not sure where any other voltage drop might be - only the on/off switch and I don't know if it can be opened to clean contacts.
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With a digital multi-meter you should be able to determine where the voltage drop is occurring

Measure the volts between the alternator output terminal and the battery positive and between the alternator negative terminal ( which may be the case) and battery negative to determine if its being lost on the + or the - connection

Then break it down into smaller sections.

If the switch is the culprit you will be able to measure the volts drop across it.
 
2 house batteries, 160ah connected together. One starter 55ah connected to house batteries by vsr (alternator goes to this).
 
VicS said:
With a digital multi-meter you should be able to determine where the voltage drop is occurring

Measure the volts between the alternator output terminal and the battery positive and between the alternator negative terminal ( which may be the case) and battery negative to determine if its being lost on the + or the - connection

Then break it down into smaller sections.

If the switch is the culprit you will be able to measure the volts drop across it.
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I have done this and can see a voltage drop between the two connected house batteries - assumed these were fine (the fool!) Not sure if one house battery is dead ... But I'll take the connections between the house batteries apart and clean everything, recharge and see if that makes a difference.
 
Go and read the Sterling website (about the AtoB charger). There are graphs showing what an alternator does. It basically drops the amps after about 20 mins (after it has put back what it took to start the engine), and as has been said above, only puts out what it thinks the batteries will take.

The AtoB basicallly kids your alternator into thinking that the batteries are in need of more charge, and in addition is drops the voltage to boost the amps, and then amplifies it in the unit.

You wil find that that it gets your house batteries up to float charge pretty quickly (whereas your alternator with a splitter will never get it to float. IMH they are worth the money and simple to fit.
 
dgadee said:
I have done this and can see a voltage drop between the two connected house batteries - assumed these were fine (the fool!) Not sure if one house battery is dead ... But I'll take the connections between the house batteries apart and clean everything, recharge and see if that makes a difference.
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If there is a volts drop between the batteries there must be some resistance somewhere between the two. Hopefully the interconnecting cable is adequate in size to carry all normal current loads without significant volts drop which means there must the a bad connection between the two. It could be bad crimps if the bolted connections are clean and tight.
 
VicS said:
If there is a volts drop between the batteries there must be some resistance somewhere between the two. Hopefully the interconnecting cable is adequate in size to carry all normal current loads without significant volts drop which means there must the a bad connection between the two. It could be bad crimps if the bolted connections are clean and tight.
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Agree, made worse with non-tinned wire where a buildup of corrosion can gradually damage the electrical connection at the crimp.
 
Bobc said:
Go and read the Sterling website (about the AtoB charger). There are graphs showing what an alternator does. It basically drops the amps after about 20 mins (after it has put back what it took to start the engine), and as has been said above, only puts out what it thinks the batteries will take.

The AtoB basicallly kids your alternator into thinking that the batteries are in need of more charge, and in addition is drops the voltage to boost the amps, and then amplifies it in the unit.

You wil find that that it gets your house batteries up to float charge pretty quickly (whereas your alternator with a splitter will never get it to float. IMH they are worth the money and simple to fit.
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Sterling kit is useful to knock down voltage to float if running for hours on end. But the claimed boost to charging efficiency requires a hefty pinch of salt (P9 here)
https://cdn.shopify.com/s/files/1/0658/7343/files/AB12130.pdf?477

Sterling's numbers are based on open flooded batteries (like Trojan) requiring c.14.8V charging voltage (bulk + absorption), coupled with an old-style wheezy-alternator delivering 14.0V. If that's the boats combo, great :rolleyes:

But the Sterling AtoB will add little if the vessel sports the widely used sla batts (25C charging voltage 14.4V, gassing voltage also c.14.4V), combined with a modern machine-sensed alternator also set to 14.4V.

If that 14.4V is not seen at the batts I wld have thought Vic's sleuthing is the first and certainly most cost efficient step?
 
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dom said:
Sterling's numbers are based on open flooded batteries (like Trojan) requiring c.14.8V charging voltage (bulk + absorption), coupled with an old-style wheezy-alternator delivering 14.0V. If that's the boats combo, great :rolleyes:
Click to expand...

That's exacty what I have, which is obviously why it works on my boat.
 
Found the problem! Intermittent bad connection. Remade. Brill! Only took a year to find it.

Thanks for the advice.
 
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