Sterling Alternator to Battery Charger

[Symphony]

As I said in an earlier post...I am confused! And still am.
To confuse things more there seems to be a case to not have big banks of batteries!
As a base assume the boat uses 100 AH per day and charges once per day.
If the boat has 600 AH battery capacity the voltage will be down very little and charging will be low on amps delivered.
If the boat has 200 AH battery capacity the voltage will be well down and charging will be high on amps delivered.
Cheaper too!!! On batteries.
But the batteries will not last as long!!!
It's enough to make you jump overboard!

Not confusing at all. If you want to use your battery capacity efficiently you carry out an audit of your average daily use and size your domestic bank such that you do not normally discharge the bank more than 50%. You then look at your charging capacity and configure this to be able to normally replace the battery capacity you use.

How you do this depends on your individual style of cruising. For example a  typical weekend cruiser will likely be able to manage just with engine charging or shorepower, particularly if they have a modern alternator. Older style alternators may benefit from one of the booster as discussed here. Liveaboards or long term cruisers are more likely to need alternative charging capacity such as solar or wind - or even a generator.

So, there is no one best way of configuring your electrical system. You just have to apply the basic principles to your pattern of usage. Even then there are often more than one way of achieving your objective.

It is worth pointing out that standard electrical systems on newer boats are way better than in the past. For example the the latest 33 which started this thread has 270AH domestic bank (compared with the standard 110AH on my old 37), an oversize alternator and mains charger - plus dedicated engine start and bow thruster if fitted. This is more than enough for typical weekend cruising, but of course if you intend living aboard without visiting marinas regularly you will need to upgrade both capacity and charging.

[tiger79]

It is worth pointing out that standard electrical systems on newer boats are way better than in the past. For example the the latest 33 which started this thread has 270AH domestic bank (compared with the standard 110AH on my old 37), an oversize alternator and mains charger - plus dedicated engine start and bow thruster if fitted.

Very true, there have been major advances in the standard of 12v systems in boats in recent years.  I have a similar system to yours, with a standard 115A alternator on a D1-30 engine.  It delivers 14.35v to the terminals of the AGM batteries.  As I've said already, the benefit of fitting an A-to-B charger to increase this to 14.4v is so minimal it's pointless.

[ANTREVELL]

Hi

I agree with jonrarit . My understanding of the way they work is as you describe . When I ran the engine with AB connected all the batteries were fully charged by my shorepower which showed a float voltage of 13.6volts. When I disconnected this and ran the engine the battery monitor and my voltmeter showed 14.4 volts . I spoke with Sterling and they said they would expect to do this for at least one hour while tops up the batteries to not around 80% but more like 95%.
Time will tell but it does appear to be doing that and where the batt monitor shows 85% charge it crept up to 95%.
At the moment I am pleased with what I see.

Regards Tony Revell Cruiser 33 Pegatha

[tiger79]

I agree with jonrarit . My understanding of the way they work is as you describe . When I ran the engine with AB connected all the batteries were fully charged by my shorepower which showed a float voltage of 13.6volts. When I disconnected this and ran the engine the battery monitor and my voltmeter showed 14.4 volts .

I'm afraid there's some misunderstanding.  The Sterling unit can't, as jonrarit claimed, "stops this drop off and keeps the alternator pumping out it's maximum until float is reached", all it does is deliver 14.4v at the terminals.  The charge current is dependent on the charge voltage.  And 14.4v delivered by the A-to-B charger is the same as 14.4v delivered any other way; the charge current will be identical.  If the alternator doesn't run anywhere near to 14.4v, there will be a benefit from fitting an A-to-B charger, with my standard alternator delivering 14.35v, it wouldn't give me any benefit.

[ANTREVELL]

I am no expert which is no doubt obvious but Sterling state the AB has a voltage amplifier . It also states it loads the alternator so the maximum voltage is achieved when in normal circumstances the battery would achieve a certain charge and then the alternator regulator would reduce the voltage output thus the batteries would be considered charged and the system would float.

In my instance when the shore power charger is connected the monitor shows a float voltage of 13.6volts the battery monitor shows the batteries at around 85% charge and the light on the shore  power show float has been achieved.  In these circumstances I would assume the alternator would replicate this situation.

When I run the engine I would expect the alternator  to produce a float voltage of 13.6 volts because the batteries are full .
With the AB installed the alternator is producing 13.9volts measured on the input of the AB  the output on the AB shows 14.4volts if the AB does not have a voltage amplifier where does the 0.5 volts come from.  After running the engine for little while the battery monitor shows the batteries to be at 100%.  This seems to confirm there claim that the AB loads and fools the alternator to produce more volts than 13.6 float which in my instance it increased by 0.3volts and it has a voltage amplifier which produces the extra 0.5volts.

Regards Tony  Cruiser 33 Pegatha

[tiger79]

Ordinary alternators only have one voltage setting, generally between 14.0 and 14.5v.  They can't reduce their voltage output to a float setting, despite what you think Mr Sterling might have claimed.

[JEN-et-ROSS]

Much of the information in this thread appears to have been obtained from the SmartGauge Electronics site. A very informative and easily understood source of advice and fine detail for the layman, like me, regarding this topic.
 However, the author of the SmartGauge Site clearly doesn't like A2B chargers, possibly because SmartGauge don't make their own version.
 As ANTREVELL indicated the A2B also creates a multi-stage charger out of a basic car alternator, this must be it's main advantage.

 We have a Merlin multi-stage shore power charger that charges much more efficiently than our alternator (Beta, 5 years old, so it's 'modern')
If the A2B can mimic this performance, I'm all for it.

[MarkTheBike]

Like some, I suspect, I'm struggling to understand the tech side of this thread, gripping though it is. 'Figaro' has the original MD2030 engine/alternator/splitter setup (but with 2x2013 AGM + 1 wet batteries) - how do I measure the various voltages referred to? Do I measure at the splitter? At the batteries? If not then where? I have a couple of digimeters that agree with eachother when measuring voltages, so are reasonably accurate (well, consistent at least). I am in the middle of fitting a battery monitor, which may help me understand a little more but any info gratefully received.

[JEN-et-ROSS]

Like some, I suspect, I'm struggling to understand the tech side of this thread, gripping though it is. 'Figaro' has the original MD2030 engine/alternator/splitter setup (but with 2x2013 AGM + 1 wet batteries) - how do I measure the various voltages referred to? Do I measure at the splitter? At the batteries? If not then where? I have a couple of digimeters that agree with eachother when measuring voltages, so are reasonably accurate (well, consistent at least). I am in the middle of fitting a battery monitor, which may help me understand a little more but any info gratefully received.

Hi Mark.
 Just measure the voltage at the output of the alternator.(probably 14v or more) Then measure the voltage at the battery terminals, it will be less.
It's how much less that is important. With an older style diode splitter you will lose at least 0.5v there alone.

It amazes me that we all go out and buy mains powered Multi-stage chargers at great expense and tell each other how great they are.
Then when Sterling bring out a device that does exactly the same thing but uses the alternator output instead. we call it a waste of money......................Bill

[tiger79]

It amazes me that we all go out and buy mains powered Multi-stage chargers at great expense and tell each other how great they are.
Then when Sterling bring out a device that does exactly the same thing but uses the alternator output instead. we call it a waste of money......................Bill

An A-to-B charger isn't necessarily a waste of money, it all depends on the voltage setting of the existing alternator.  With modern alternators, there's virtually no benefit; with older alternators, there may be.

[JEN-et-ROSS]

An A-to-B charger isn't necessarily a waste of money, it all depends on the voltage setting of the existing alternator.  With modern alternators, there's virtually no benefit; with older alternators, there may be.

I think you've missed my point Tiger79.
 While I agree with all you've said,
I was really wondering why we all want 'smart' chargers for our shore power? but when it comes to our alternators we should be happy to accept the constant 14.4v or thereabouts that they belt out.
 If that's the case why bother with 'smart' multi-stage mains chargers at all? when any old transformer/rectifier combination that will produce the same 14.4v or so will do the job just as well.
 Like many others in this thread.............I'm still confused.....Bill
 

[tiger79]

I think you've missed my point Tiger79.
 While I agree with all you've said,
I was really wondering why we all want 'smart' chargers for our shore power? but when it comes to our alternators we should be happy to accept the constant 14.4v or thereabouts that they belt out.
 If that's the case why bother with 'smart' multi-stage mains chargers at all? when any old transformer/rectifier combination that will produce the same 14.4v or so will do the job just as well.
 Like many others in this thread.............I'm still confused.....Bill

OK, understand what you're saying.  I think the reason is that many people leave their mains chargers switched on for long periods, when they're not at the boat, and so want the charger to drop to a float voltage.  On the other hand, engines tend to be used for much shorter times (especially in sailing boats), so the more complex regime of float voltage isn't such a priority.

It's easy to add a "smart" multi-stage regulator to an alternator - some of them (eg Balmar and Ample Power) are quite sophisticated.  But for most leisure boaters it's not a great advantage.

[Jeff Jones]

If you have shore power the charging your batteries that seem quite easy - fit a decent electronic charger (bulk, top off and with float charge settings) you can pretty much forget about them.

but if off grid, (I am) on a swing mooring, or if cruising then running the engine to charge the batteries is pretty much guess work..

You cant tell for sure:-
- How long to run the engine? or when the batteries are recharged or IF full?

- If you don't look after and recharge the batteries properly, are we shortening the life of the batteries or are we not getting the best usable energy out of them before each recharge?

Battery monitors help - but can give a false indication what's happening with the batteries - just after charging when the surface charge is still high +13v for example.
You will need to run a electrical load after charging so that the battery monitor can properly calculate the actual power is the battery - I turn on my deck light for about 1min and with the load it show better what is in the batteries.

I also find, that when charging my batteries the monitor never shows more than 80- 85% with the engine still running but the current going to the batteries has dropped to <5amps (showing nearly full), but after the charging stops the capacity keeps raising up to 100%.

A good rule of thumb -
What I do find is when the current drawn by the charging batteries is about 3-5% of the total Amp/hr installed you are as full as its going to get.
After turning on a load my monitor shows the battery voltage drops to  around 12.7v and capacity drops to about 95%..

An Example, of how miss leading they can be..
last weekend I charged the house battery on the Saturday and the monitor said the battery had received 30Amp/hr and that the battery was at 95% 12.7v - I ran the Eberspacher for a total of about 4hrs @ 3Amps/hr  total used 12Amp/hr and had the radio / TV on for a short while say a total of about 20Amp/hrs used - (my battery is 140Amp/hr) at the end of the night the battery was showing 12.1v or 40% ie that I had used 84Amp/hr. This is because the condition of the battery plays an important part of how well it accepts a charge and also how well it can deliver sustained power..

These types of battery monitors use an equation to calculate the State of Charge% - which is how good the battery can keep up the voltage for a given current drawn by a load - (my deck light is 10w halogen).

Personnel, I am going down the route of having a good sized house battery bank +450A/hr, a good sized alternator (115A) to bulk charge as quick as possible (25% of the installed Amp/hr to bulk charge), I will use my batteries down to around 50% SOC or to 12.2v and then recharge up to around 90%. The battery monitor has a Amp/hr 'counter' so I can keep a check of what Amp/hrs 'go in' and 'what is used' as another guide to how long to run the engine for.
This based on new batteries, over time an sure I will have to adjust my guide

Anything to do with batteries and charging (off grid) isn't black and white - As i am finding it seems to be a compromise for sure and the best way forward is not always clear. 

The main idea is not to have to run our engines any longer than needed to recharge the house batteries to a good state. - but am not sure that with a modern alternator and decent batteries whether a smart charger or A-B charge will make things any easier or add any benefit - off grid. 

I think it needs a mixed approach - So now I am planning the next step to install a solar panel to take care of the trickle / float charge - and hopefully with some sun (returning to my boat on a Friday I should find the batteries somewhere near fully charged) and only to have the engine running a short while each day.   
 

[Jeff Jones]

FYI - I have found these web site useful     http://batteryuniversity.com/learn/article/how_to_measure_state_of_charge

[JEN-et-ROSS]

OK, understand what you're saying.  I think the reason is that many people leave their mains chargers switched on for long periods, when they're not at the boat, and so want the charger to drop to a float voltage.  On the other hand, engines tend to be used for much shorter times (especially in sailing boats), so the more complex regime of float voltage isn't such a priority.

Fair comment tiger79.
Like Jeff Jones we have a swinging mooring and since pontoon berths are few and far between up here we rarely have access to shore power.
To counter the problem we have a Rutland 913, a couple of solar panels and a smelly/noisy old diesel generator built into a large forward locker. ( not something you would be popular for firing up in an picturesque anchorage) We also use Sterling Powers' Pro Split R to minimise losses from the alternator...........So I guess in our situation we are doing all we can.....and yes, the A2B would not achieve very much. Thanks for the advice........Bill