Sterling A2B charger versus Pro Digital

[Cardo]

Ok, I know I've asked a very similar question in the past, but I just need to get this sorted in my head.
I'll shortly be upgrading the alternator charging on le bateau, seeing as it is simply dire at the moment.

The two options I'm looking at are:
Sterling A2B:
http://www.marinesuperstore.com/item/99197766/sterling-alternator-to-battery-charger
and
Sterling Pro Digital:
http://www.marinesuperstore.com/item/07519/sterling-alternator-regulator-pro-digital

There's a £110 difference between them, so I would rather go for the cheaper one if it'll be ok with my setup.

Currently, we have 500Ah of sealed lead acids in the domestic bank, and a single regular lead acid (80Ah I think) starter battery. Alternator charging is from built-in alternator regulator, through a split diode. Charging isn't exactly fantastic.

The A2B charger looks easy enough to wire up. Bulk of charging goes to the domestic bank, and the starter battery receives a trickle charge to get it back up and keep it running. No probs there.

The Pro Digital, on the other hand, only has a single output, which you would then run through a diode to supply domestic and starter batteries. This is what has me confused. If you're putting a load of amps in to charge up the domestics, how is the starter battery not cooked?
There's probably some obvious reason for this not being an issue, but I sadly lack the knowledge and would like to ensure this practice is not a problem before I go for this option over the A2B charger.

Advice, as always, very much appreciated.

 

[ianj99]

Ok, I know I've asked a very similar question in the past, but I just need to get this sorted in my head.
I'll shortly be upgrading the alternator charging on le bateau, seeing as it is simply dire at the moment.

The two options I'm looking at are:
Sterling A2B:
http://www.marinesuperstore.com/item/99197766/sterling-alternator-to-battery-charger
and
Sterling Pro Digital:
http://www.marinesuperstore.com/item/07519/sterling-alternator-regulator-pro-digital

There's a £110 difference between them, so I would rather go for the cheaper one if it'll be ok with my setup.

Currently, we have 500Ah of sealed lead acids in the domestic bank, and a single regular lead acid (80Ah I think) starter battery. Alternator charging is from built-in alternator regulator, through a split diode. Charging isn't exactly fantastic.

The A2B charger looks easy enough to wire up. Bulk of charging goes to the domestic bank, and the starter battery receives a trickle charge to get it back up and keep it running. No probs there.

The Pro Digital, on the other hand, only has a single output, which you would then run through a diode to supply domestic and starter batteries. This is what has me confused. If you're putting a load of amps in to charge up the domestics, how is the starter battery not cooked?
There's probably some obvious reason for this not being an issue, but I sadly lack the knowledge and would like to ensure this practice is not a problem before I go for this option over the A2B charger.

Advice, as always, very much appreciated.

The multiple outputs are in effect supplied via a built in diode splitter (using transistors) and each battery is NOT charged and monitored separately on most of these chargers whether mains or A2B.

The reason why this works without boiling the engine battery is because battery voltage rises in proportion to state of charge so the flattest battery will have the lowest voltage and therefore will take the most current. If the other battery was fully charged, its voltage would be high enough to ensure it received little charge. (standby for another flood of battery charging replies!!)

I have both Sterling pro digital regulators (on boat and camper) and they work well. I am not convinced about the benefits, if any of the A2B type.

 

[pvb]

As you have an ordinary wet lead acid starter battery, you can (if necessary) top up the electrolyte level. So either of your proposed systems would work. However, the A-to-B unit is superior as it has the ability to provide a float charge voltage. In contrast, the Pro Digital can only increase the alternator's voltage, not reduce it to float charge level. And, of course, the A-to-B also provides an unboosted output for the starter battery. Oh, and it doesn't require any mods to the alternator. I'd go for the A-to-B.

 

[Alpha22]

Current is not given, it is taken.

You cannot force current into a battery, it will draw current from the charger.

 

[ianj99]

As you have an ordinary wet lead acid starter battery, you can (if necessary) top up the electrolyte level. So either of your proposed systems would work. However, the A-to-B unit is superior as it has the ability to provide a float charge voltage. In contrast, the Pro Digital can only increase the alternator's voltage, not reduce it to float charge level. And, of course, the A-to-B also provides an unboosted output for the starter battery. Oh, and it doesn't require any mods to the alternator. I'd go for the A-to-B.

The Pro digital most certainly does reduce the alternator's output to float level, this being set with the dip switches inside it. From the Prodigital manual:

Open lead acid: max charging (absorption) voltage 14.8, absorption time 1-3hrs, float voltage 13.65 @20C,
Gel 14.4v/10-12hrs/13.8@20C
SLA 14.4v/4-8hrs/13.65@20C
AGM 14.1v/4-10hrs/13.5v@20C (USA spec batteries)

Don't put all your eggs in one basket. With a Pro digital and a separate diode splitter, either can be replaced for less than the cost of another A2B unit if it fails out of warranty.

PS buy the cheaper of the two digital regulators - about £99. I have one of each and the more expensive one offers no advantage (to me).

 

[pvb]

The Pro digital most certainly does reduce the alternator's output to float level, this being set with the dip switches inside it. From the Prodigital manual:

Open lead acid: max charging (absorption) voltage 14.8, absorption time 1-3hrs, float voltage 13.65 @20C,
Gel 14.4v/10-12hrs/13.8@20C
SLA 14.4v/4-8hrs/13.65@20C
AGM 14.1v/4-10hrs/13.5v@20C (USA spec batteries)

Don't put all your eggs in one basket. With a Pro digital and a separate diode splitter, either can be replaced for less than the cost of another A2B unit if it fails out of warranty.

When installed according to Sterling's instructions, the Pro Digital can only increase the standard voltage of the alternator. If the standard regulator on the alternator is set to 13.5v, then the float voltages you've quoted can be achieved. Otherwise, the float voltage will be the alternator's normal voltage, usually around 14v. It can't be any lower. As you've quoted the Pro Digital manual, take a look at the section which describes the LED indicators, and you'll see it says "Green: Float Mode: This indicates that all the high charge cycles are now over and should remain on after all the high charge lights are out. The system is now running at a standard charge rate only (about 14 volts) regulated on the battery."

It is possible to remove the alternator's standard regulator and just use the Pro Digital as an external regulator, in which case it will produce true float voltages, but this not what many people would do as it removes the fail-safe option.

 

[ianj99]

When installed according to Sterling's instructions, the Pro Digital can only increase the standard voltage of the alternator. If the standard regulator on the alternator is set to 13.5v, then the float voltages you've quoted can be achieved. Otherwise, the float voltage will be the alternator's normal voltage, usually around 14v. It can't be any lower. As you've quoted the Pro Digital manual, take a look at the section which describes the LED indicators, and you'll see it says "Green: Float Mode: This indicates that all the high charge cycles are now over and should remain on after all the high charge lights are out. The system is now running at a standard charge rate only (about 14 volts) regulated on the battery."

True, the float voltage can never be less than the alternators own output but why is this an issue? Also, the Prodigital does allow for the voltage drop across the diode splitter.

As far as removing the internal regulator, I have tried this but it doesn't work. The manual states not to proceed if the internal regulator is not working, though Sterling replied in an email that it can be removed. However I found that the Prodigital would go into fatal error mode with all leds flashing after about 20mins regardless of the state of charge of the battery. I have since fitted a new regulator to the alternator and the Prodigital is working as intended.

With any digital regulator you do need to check the electrolyte levels regularly - its the price you pay for aiming for 100% charge and the A2B won't be any different in this respect.

 

[pvb]

The Pro digital most certainly does reduce the alternator's output to float level, this being set with the dip switches inside it.

True, the float voltage can never be less than the alternators own output

Glad you now agree with me.

 

[ianj99]

Glad you now agree with me.

Happy to oblige!

 

[ianj99]

On the subject of alternator alteration to work with the Prodigital, if you have a Lucas A127 type alternator that uses this type of regulator/brush box.

http://www.ebay.co.uk/itm/NEW-12V-R...RNATOR-1150M-WITH-CHARGING-WIRE-/290714186281

This replacement comes with the required extra connection. (Bewarned, one seller is advertising a similar part for insulated return alternators. Do NOT fit one because they have failed to insulated the regulator return from the alternator casing - it needs more than 3 insulated bolts)

 

[ianj99]

A2B charger v Prodigital

The main advantages of the A2B products seem to be :
no alternator mods required
no engine / alternator warranty implications
multiple outputs
can be used with multiple alternators

However given that Sterling make much their battery charging products ability to increase charging currents for faster and more complete charging, I cannot see that this is as effective with any A2B unit. After all, the alternator output is still controlled by its own regulator and much is made of the limitations of this.
So if the alternator output is the same, where are the benefits other than those listed above?

http://www.sterling-power.com/datasheets.htm - down load the 'Must Read - advanced battery charging systems'

If you want more from your existing charging system, fit a digital regulator, if you can't, don't want to, its technically impossible or there are warranty implications, then fit an A2B unit.

 

[pvb]

However given that Sterling make much their battery charging products ability to increase charging currents for faster and more complete charging, I cannot see that this is as effective with any A2B unit. After all, the alternator output is still controlled by its own regulator and much is made of the limitations of this.
So if the alternator output is the same, where are the benefits other than those listed above?

"Smart" alternator regulators increase the alternator's output voltage. Higher voltage at the battery terminals produces a higher charging current (obviously depending on the alternator's ability to provide current and the batteries' ability to accept it). Instead of increasing the field voltage, the A-to-B charger uses a voltage amplifier to increase the voltage provided to the batteries. The benefits are as you stated, plus the fact that it will provide a true float voltage - important perhaps for those owners who use the engine for extended periods. For many buyers, the attraction is probably that there's no need to mess about connecting wires to the alternator brushes.
.

 

[GHA]

However given that Sterling make much their battery charging products ability to increase charging currents for faster and more complete charging, I cannot see that this is as effective with any A2B unit. After all, the alternator output is still controlled by its own regulator and much is made of the limitations of this.
So if the alternator output is the same, where are the benefits other than those listed above?

The data sheet shows voltage between the a2b and alternator as 13.5-14.1 so does the unit make the alternator regulator think its charging a fully discharged battery and put out max current?

 

[ianj99]

The data sheet shows voltage between the a2b and alternator as 13.5-14.1 so does the unit make the alternator regulator think its charging a fully discharged battery and put out max current?

After consideration, I believe you are spot on and this is how Sterling can claim 5times faster charging and twice as much charge in the batteries.

The load on the alternator will be much different to that of a battery so undoubtedly the alternator output could be maximised but is still dependent on the characteristics of the regulator to some extent.

I suppose the obvious conclusion is that Sterling have found that their regulators cannot increase the alternator output compared to using the alternators own regulator into a fully discharged battery.

 

[pvb]

Sterling say that "In order to maximise the alternator output current, the alternator-to-battery charger pulls the alternator output voltage down to about 13V. Then this low voltage is amplified to a higher voltage suitable for effective battery charging, i.e. 14.1V to 14.8V."

 

[Bobc]

Can't comment on comparisons, but I can share my experiences with you.

I had 675Ah of domestic bank, and a 60Ah alternator running through a diode splitter. I was only achieving 12.9v to the batteries, and simply couldn't get them charged properly even by running the engine all day.

Fitted an A-B charger, and now my battery monitor shows 14.6V to the domestic bank when on boost charge, and I can get the bank from 12.2v to fully-charged and on float (at 13.6v) in 2 hours. This is still with the 60A alternator.

The unit only took a couple of hours to fit (just replaces the diode splitter), and has absolutely transformed engine charging. It was worth every penny.

 

[garvellachs]

Can't comment on comparisons, but I can share my experiences with you.

I had 675Ah of domestic bank, and a 60Ah alternator running through a diode splitter. I was only achieving 12.9v to the batteries, and simply couldn't get them charged properly even by running the engine all day.

Fitted an A-B charger, and now my battery monitor shows 14.6V to the domestic bank when on boost charge, and I can get the bank from 12.2v to fully-charged and on float (at 13.6v) in 2 hours. This is still with the 60A alternator.

The unit only took a couple of hours to fit (just replaces the diode splitter), and has absolutely transformed engine charging. It was worth every penny.

Those figures seem a bit optimistic? 12.2V on the 675Ah bank suggests about half-discharged? So you need to put back at least 300Ah? So with a 60A alternator you need to charge for at least 5 hours to get back to fully charged?

 

[Bobc]

Those figures seem a bit optimistic? 12.2V on the 675Ah bank suggests about half-discharged? So you need to put back at least 300Ah? So with a 60A alternator you need to charge for at least 5 hours to get back to fully charged?

Simply the facts. Coming back from the Azores, we ran the engine for 2 hours in the morning, and again in the evening. The bank would normally get down to 12.2v. I suspect that had we turned everything off and let the batteries rest, they probably would have recovered to 12.4 or 12.5v. This was with the autohelm, instruments, and 2 fridges running 24/7, plus nav lights at night, and charging of laptops, ipods, etc.

 

[VicS]

Simply the facts. Coming back from the Azores, we ran the engine for 2 hours in the morning, and again in the evening. The bank would normally get down to 12.2v. I suspect that had we turned everything off and let the batteries rest, they probably would have recovered to 12.4 or 12.5v. This was with the autohelm, instruments, and 2 fridges running 24/7, plus nav lights at night, and charging of laptops, ipods, etc.

A large part of your problem was probably due to the voltage drop across the diode splitter ... unless you had a battery sensing alternator which would have compensated for that.

The voltage drop is round 0.6 to 0.7 volts minimum but it increases with increasing current flow.

 

[Bobc]

A large part of your problem was probably due to the voltage drop across the diode splitter ... unless you had a battery sensing alternator which would have compensated for that.

The voltage drop is round 0.6 to 0.7 volts minimum but it increases with increasing current flow.

Yes, indeed it was 0.7 I believe. The A to B unit just gave me a quick, simple, and effective solution to my problem, without having to muck about with regulators or soldring bits onto brushes (or paying a marine sparky).

I'm sure that if you have the time knowledge, and inclination, there is a cheaper solution.