Views on alternator to battery charging systems?

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To respond to Amazoncats query.....

The a to b charger basically fills 2 jobs. It acts to boost the output from the alternator and thereby decrease charging time. Secondly it acts LIKE a VSR in that it charges two batteries. It is not a VSR as a VSR will not switch charging to the domestic bank until start voltage gets high enough. The A to B just chucks some charge in for a few minutes then switches to domestic. In practice this is fine as engine start shouldn't need much charge.

It is very simple providing you already have two separate batteries with separate switches and a VSR / split charging regime rather than 1-2-both-off. If you have 1-2-both-off simply rewire to separate them and fit.

I've had mine for a year and has transformed our experience. Previously there was a nagging fear that the domestics would die and we would find that under heavy load we would need to run the engine every few hours under way, to the extent of thinking we needed a much bigger domestic bank. With the AtoB charger, that is not an issue and don't really monitor the voltage when underway anymore.
 
jac said:
The a to b charger basically fills 2 jobs. It acts to boost the output from the alternator and thereby decrease charging time.
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How does that work, then? If it increases the volts to push more charge in it'll decrease the amps, so less charge will go in and if it increases the amps it'll decrease the volts, so less charge will go in.

I've had mine for a year and has transformed our experience.
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i wonder - and I am not trying to be mean or contentious here - how much of that is psychological. You have the same alternator, I presume, so you have the same charging power available, but now with a complicated box of electronic involved as well. I suppose it can do complicated things with charging regime, but these have never convinced me, particularly, and when ones goes to huge lengths to get that last 5% of possible charge in ... well, it's still only 5%. Want to store more? Buy a bigger battery. Want to charge faster? Buy a bigger alternator.

I confess that I have an Adverc fitted, but only because I rather naively bought it when I got the boat and thought I might as well fit it. I don't kid myself that it does anything useful.
 
JumbleDuck said:
How does that work, then? If it increases the volts to push more charge in it'll decrease the amps, so less charge will go in and if it increases the amps it'll decrease the volts, so less charge will go in.



i wonder - and I am not trying to be mean or contentious here - how much of that is psychological. You have the same alternator, I presume, so you have the same charging power available, but now with a complicated box of electronic involved as well. I suppose it can do complicated things with charging regime, but these have never convinced me, particularly, and when ones goes to huge lengths to get that last 5% of possible charge in ... well, it's still only 5%. Want to store more? Buy a bigger battery. Want to charge faster? Buy a bigger alternator.

I confess that I have an Adverc fitted, but only because I rather naively bought it when I got the boat and thought I might as well fit it. I don't kid myself that it does anything useful.
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Not sure I 100% understand it but my simplified understanding is this.

The smart regulator in the charger fools the alternator into thinking the battery is lower than it is so makes the alternator work harder than it would otherwise. Within the module itself, it works the same as a smart battery charger in terms of changing voltage - amperage to match the stage it is at.

Re the psychological impact. That is true but i think is driven by experience.

In 2013 we had the instruments die twice and so had to start the engine. One of those happened after a fairly short sail. In 2014 it didn't happen at all despite some longer passages. Same batteries, same demand. Only change was the AtoB.

I have put it down to the fact that the motoring we have done, (e.g. In and out of harbours) has put in much more charge than the alternator alone would have done the previous year.
 
The Sterling A-to-B charger is an interesting device. It does load up the alternator, and has a real multi-stage charging regime for the domestic batteries - including the ability to drop to a float voltage (which ordinary add-on smart regulators can't do). It acts as a blocking diode to isolate the engine start battery. And the output to the start battery is unboosted, so as to avoid excessively charging it. On top of all that, it doesn't need any alterations to the alternator. If I needed better charging, I'd certainly be tempted by it.
 
I fitted a Sterling A2B two years ago along with beefing up the harness to the domestic bank. I eliminated the VSR that had kept the starter and domestic banks isolated from one another because the A2B does that job.

It was simple to fit and has boosted the alternator output by about 75%. I have no idea as to how the box works but it does: the only uncertainty is that because I beefed up the wires to the battery how much of the improvement is down to the wiring and how much to the box of tricks?
 
duncan99210 said:
I fitted a Sterling A2B two years ago along with beefing up the harness to the domestic bank. I eliminated the VSR that had kept the starter and domestic banks isolated from one another because the A2B does that job.

It was simple to fit and has boosted the alternator output by about 75%. I have no idea as to how the box works but it does: the only uncertainty is that because I beefed up the wires to the battery how much of the improvement is down to the wiring and how much to the box of tricks?
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I kept most of the same wiring - just new leads but same size from AtoB to batteries so in my case I think the improvement was down to the AtoB.
 
JumbleDuck said:
How does that work, then? If it increases the volts to push more charge in it'll decrease the amps, so less charge will go in and if it increases the amps it'll decrease the volts, so less charge will go in.

The amount of charge going into a battery depends on the battage applied to the battery. The voltage and hence the current may be limited by the capacity of the charging source to maintain that voltage at the current going into the battery.
Now generally the current capability of the alternator is NOT a limiting factor in the charge going into the battery. It an be on really big battey systems so just check.
The A to B charger takes the DC as found at the starter battery /output of alternator say 13volts under charge. By rapid switching transforming and rectifying it produces a voltage of about 15volts. * This voltage does push a larger current into the domestic battery. However the current being taken from the alternator/engine battery will be higher by a factor of the ratio of volts in to volts out and the inefficiencies of the converter. Perhaps 90% efficient. So typically 20 amps intot he battery will take 25 amps from the alternator. The a to B charger looks like any other electrical load to the alternator like lights on a car ie current is only slightly (ie linearly) dependent on voltage.
So assuming your alternator has the capacity then the a to B charger can push more current into the domestic battery than the hard wire connection via switches. VSR or 1,2,both switch)
The alternator regulator should maintain the normal charge voltage so charging the engine battery to about 13.75 or 14 volts but this may sag a bit with the load of the a to b charger. The a to b charger only begins charging when the engine batttery gets over about 13 volts so only when alternator is charging.
*The voltage the a to b charger actually presents to the battery to push the current in is actually set by algorythms and on the basis of the charge state of the battery. So initially high then down to float etc. The same as alternator controllers of mains chargers. good luck olewill
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William_H said:
*The voltage the a to b charger actually presents to the battery to push the current in is actually set by algorythms and on the basis of the charge state of the battery. So initially high then down to float etc. The same as alternator controllers ...
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This misunderstanding is often repeated. Add-on "smart" alternator regulators (Sterling, Adverc, etc) work in parallel with the alternator's internal regulator and can only increase the output voltage - they can't reduce the voltage to float level (unless the internal regulator is set at float level, which is unlikely).
 
William_H said:
The A to B charger takes the DC as found at the starter battery /output of alternator say 13volts under charge. By rapid switching transforming and rectifying it produces a voltage of about 15volts. * This voltage does push a larger current into the domestic battery.
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Heck of a lot cheaper and simpler to buy a better alternator. Mine give 14.4V, traditional ones 13.8V. A 13V alternator is knackered.
 
This is an old thread and the Sterling A2B charger still has the same old problems.

The Sterling is a clever BODGE for alternators that would otherwise have to be taken apart and modified to be able to control the field wires.

It works by dragging the alternator voltage down to 13v and sucking out all the power it can and then provides a higher voltage to charge the batteries. This will over stress and over heat the maybe already OLD alternator whose overall power output would then be much reduced and it may well fail earlier than it should.

Read Mr Sterling's product description and you will see the A2B is designed to only run for 15 minutes before "resting" for 2.5 to 3 minutes. So 15% of it's running time it is not charging the house bank, only gently topping up the starter bank - great design Mr Sterling!!!!!!! This must be to allow the alternator to cool down, although Mr Sterling doesn't use those words, he calls it resting. In old product brochures he had graphs that clearly showed this feature. He has modified these graphs now to hide the true operation of the unit.

So it is designed with an inefficiency of 15% from the start. If you then add the inefficiency of a high current DC to DC converter to get the 13v alternator output up to 14.8v that is another 10-15% wasted. So the A2B charger has an extra built-in inefficiency of maybe 30% over a traditional external regulator, so it would take 30% longer to bring a battery bank to the same state of charger as an external regulator controlling the field wire.

It does the job, but is designed, as Mr Sterling says, for those who can't or won't remove the alternator to get it modified.

You get what you deserve in life.
 
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sailorman said:
BUT how many amps after 5 minutes.
with my newly acquired Adverc i still get 20 amps after 1/2 hr if the batts are low
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I have an Adverc too. It does nothing at 14,4V, because it can't, but after an hour of the alternator heating up and the temperature compensation kicking it, it starts to have an effect. A better alternator would remove the need for it.
 
I have used Sterling's digital alternator regulators on a motorhome and boat and they do work well and if they fail, the alternator will continue to work. But I would never buy any expensive item from them....

I spent £279 on their 30amp triple output mains charger which blew up (literally) about 10months out of warranty. No spare parts were available so the best Sterling offered was a discount off its replacement. (another £229)

When Sterling increase their warranty to 3 years on expensive products then I might reconsider, but no way would I risk several hundred pounds on anything with a 1 or two year warranty when its likely that any repair won't be possible.

(You'd be even more mad to think about fitting an inverter-charger - if that fails, you've lost your inverter and your battery charger.)
 
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