Alternator to battery charger

[bobbynell]

Oh dear, didn't mean to open a can of worms...

 

Thanks for the replies, I can see that this device could have a use, but might not be as important to install as I thought.

 

As long as I can be sure that alternators have the ability (I'm sure they have the capacity) to efficiently charge domestic baterries then I'm just looking for the method/means.

 

I'd definately be keen to hear of the 'other systems' that are often alluded to. My main challenge is obviously the myriad of different products that are available, but their purpose not being immediately apparent/comparable with each other.

 

The Sterling device says quite clearly on the tin what it does - obviously whether it ACTUALLY does it is up for debate!

 

First make sure that your existing alternators (especially the 110A one) are optimally installed. For example if you have one of the popular modern engines then wiring the domestic alternator directly to the domestic batteries with a decent size of cable thus bypassing the original engine harness and connection stud will help a lot.

 

Then, if you really want to soup it up, fit a battery sensed regulator system. As Sterling themselves state on their site "The Digital Advanced Alternator Regulator offers the best low cost technical solution to increase the output performance of your alternator" and for "The Digital Advanced Alternator Regulator" you can read "battery sensed regulator" to all intents and purposes.

Thanks, that is very helpful and gives me some confidence in stepping forward.

 

Although far from an expert I'm happy with electrics as long as I have the basic information to start with, and has started to feel like one aspect that is quite hard to see the wood for the trees!

[charles123]

This is more of a question than an answer because my knowledge of the black at of boat electrics is limited however, Bobby has 2 alternators and I assume that the smaller one feeds the starter battery only and the bigger one feeds the domestic batteries only. Someone correct me if wrong as I dont fully understand this product but I thought where you had 2 alterators on the engine it had the capability of taking the output of both alternators adding the outputs together and then sending the output to starter and domestic according to need

 

So at present Bobby has a 110 amp theoretical output into the domestics but with the alternator to battery charger its 110+70 = 180 amps or does it not work that way?

 

Charles

[Billypownall]

Let's have a quick look at how it works, some technical facts (not opinions) and the inevitable results..........

 

An alternator is, to a first approximation, a constant current device. That means, if you take a 70 amp alternator, load it up to full output it will be producing 70 amps. Load it a little bit more and it will continue to produce 70 amps but the output voltage will drop slightly. Continue to increase the load and the output voltage will drop more. But the output current will remain at 70 amps.... to a first approximation

 

So, we have a 70 amp alternator with an internal reg running at 14.6 volts (a common alternator output voltage). Just before acceptance it is producing 70 amps into the batteries at 14.6 volts. Thus 14.6 volts * 70 amps = 1,022 watts is going into the batteries.

 

The alternator to battery charger loads up the alternator so its output drops to about 13.5 volts. The device then, internally, ups it output voltage (not the input voltage obviously) to the batteries (subject to current limits) to 14.8 volts. The output of the alternator will still be 70 amps. Thus 13.5 volts * 70 amps = 945 watts is going into the device.

 

Conservation of energy means we can't get out more than we put in so we instantly know that the output of that device is less than it would have been if it wasn't there!

 

Now, I don't know the efficiency of it but I do know, from the size of the unit, and the cooling fins, that it cannot possibly be any higher than 90%. So, going into the batteries is 945 watts * 90% = 850 watts as an absolute maximum. That's 83% of what we started with. The other 17% is heating the device up. Thus the huge fins and cooling fan.

 

Strapping the alternator directly to the batteries will (not might) result in more charge!

 

The device was designed because many modern vehicle alternator simply will not allow an external reg to be connected. It can throw the engine management system into error mode. So you simply can't put one on. Which means you can't install split charge diodes.

 

In a boat, there is simply no reason to install one. It is pointless. All it will ever do is reduce the available charge.

 

Make sure the alternator charges at a proper voltage (14.4 to 14.6 volts is about right) and put on a split charge relay. 60 quid tops. And the results will be better.

 

The above is a gross over-simplification and there are other different scenarious during the charge cycle where the figures won't come out quite so bad but it deals with facts that cannot be argued against. The reality is that as long as the alternator produces the correct output voltage (usually a simple matter of changing the reg/brush pack) that device will never result in an increase in charge rate.

 

But there again, that's not what it was designed for.

Edited July 19, 2010 by Billypownall

[WotEver]

This is more of a question than an answer because my knowledge of the black at of boat electrics is limited however, Bobby has 2 alternators and I assume that the smaller one feeds the starter battery only and the bigger one feeds the domestic batteries only. Someone correct me if wrong as I dont fully understand this product but I thought where you had 2 alterators on the engine it had the capability of taking the output of both alternators adding the outputs together and then sending the output to starter and domestic according to need

Yes, but as Gibbo has already pointed out,a 60 quid split charge relay will do just that (parallel the alternators & batteries).

 

Tony

 

For £235 you can get a Smart Gauge Advanced which will not only do intelligent paralleling of the batteries but will also tell you your true state of charge and a whole lot more.

 

As already stated, replace the wimpy wiring loom charge cable with a nice new fat one, then fit a SG Advanced and you'll know what's happening and all will be well with the world.

 

Tony

[Arnot]

I thought where you had 2 alterators on the engine it had the capability of taking the output of both alternators adding the outputs together and then sending the output to starter and domestic according to need

Not really, it can't control what battery takes power or how much it takes.

 

So at present Bobby has a 110 amp theoretical output into the domestics but with the alternator to battery charger its 110+70 = 180 amps or does it not work that way?

This is the myth that sells the product and those who propound the concept of paralling alternators accept. Unless you have a massive battery bank which is fairly flat it wont actually accept 180A for more than a minute or two and shortly after this the current demand would fall to less than 110A. If the battery bank would accept high currents for long periods then the answer is to fit a more appropriate alternator rather than trying to force the smaller pair to operate harder than they were designed to.

 

Regards

 

Arnot

[Billypownall]

Yes, but as Gibbo has already pointed out,a 60 quid split charge relay will do just that (parallel the alternators & batteries).

 

Tony

I am sure Gibbo is right with his calculations. However in our case I have to say that the Sterling Alternator to Battery Charger appears to have solved all our problems. Last year we had nothing but low battery problems mainly because the voltage from the alternator reaching the batteries rarely reached 14 volts. Barrus checked the alternators and deemed them OK. Following Gibbo's advice on this forum we had the cable from the domestic alternator increased in size. This helped and we did see 14.15 volts but no more than this even after a full day's cruising. Mostly the most we saw was 14 volts.A somewhat crude clip on ampmeter would show a charge rate of about 55 amps when the batteries were fairly low dropping to 25 amps as they became charged.The inevitable smartgauge was fitted which seemed to verify that the alternator would take forever to charge our batteries (660 amp). The wiring to and from the batteries was changed as Gibbo recommends. Input and output from one end from one end of the battery bank and negative from the other.This maybe helped a little. The Sterling unit appealed as it seemed so simple to fit ( I would not have a clue how to fit a relay) and the idea of the engine alternator doing a bit more work appealed. It would not futhermore void the guarantee on the alternators. Well why or how I do not know but the Sterling has worked. We now get 14.7 volts at the batteries. The ampmeter shows a much increased reading and the Smartgauge will show 100% in about 4-5 hours. Maybe we have been robbed as to the cost but the result to us has been worth it.

[Gibbo]

(big snip)

 

We now get 14.7 volts at the batteries.

 

And this is the whole point............

 

The part quoted above is the only thing that has changed. How much is that devce? You could have increased the charge voltage for about a tenth of the price.

 

And believe me, that really is the only difference that device has made. All the other changes you have seen are as a direct consequence of increasing the charge voltage. There is no magic.

 

This is the myth that sells the product and those who propound the concept of paralling alternators accept. Unless you have a massive battery bank which is fairly flat it wont actually accept 180A for more than a minute or two and shortly after this the current demand would fall to less than 110A. If the battery bank would accept high currents for long periods then the answer is to fit a more appropriate alternator rather than trying to force the smaller pair to operate harder than they were designed to.

 

There is a lot of truth in this, but, and it's a very big but, paralleling alternators that aren't spinning fast enough (a very common problem on narrowboats) is a damned site easier than repulleying, and also achieves the objective of increased charge current. It also gives built in redundancy. It also (assuming the correct relay is used) adds the option of emergency parallel starting. Admittedly not a major bonus when, to use your phrase, safety is merely a short jump away.

[churchward]

Just to put my two penneth in as a user of the Sterling ABC.

 

As others have said I have found the unit does pretty much what it says it will and has done so for over two years. I am not a live aboard but use the boat for holidays. We have just one alternator (70amp) and find that we recharge the batts in about 4+ hours after a normal nights use. The batts are a modest (by today's stds) X3 110 Amp/hr but they are enough as I find that the SG shows 65-70% SOC in the morning.

 

The Sterling ABC does simplify the wiring and means you don't have to modify the alternator thus avoiding any warranty issues.

 

Having said all that if I knew then what I know now I doubt I would have bought it and wouldn't replace it if it went phut! I found the alternator pushes out between 14.4v and 14.6v all by itself. If I were replacing I would buy the Smartbank advanced to go with my Smartgauge and if needed a cheap as possible solution to boosting the charging voltage.

[bobbynell]

Yes, but as Gibbo has already pointed out,a 60 quid split charge relay will do just that (parallel the alternators & batteries).

 

Tony

 

For £235 you can get a Smart Gauge Advanced which will not only do intelligent paralleling of the batteries but will also tell you your true state of charge and a whole lot more.

 

As already stated, replace the wimpy wiring loom charge cable with a nice new fat one, then fit a SG Advanced and you'll know what's happening and all will be well with the world.

 

Tony

Thanks Tony, that is looking like the best option as I was planning to purchase a Smartgauge anyway, but hadn't appreciated that the Smartbank would cover all the charging needs. To be honest I had just seen it as a split charge relay and not fully understood the rest of it.

 

What I still can't tell though is will it use both alternators? It would be handy to know as I have two available. The diagrams on the Smartgauge website only show one and I don't see any mention of paralleling.

[Gibbo]

Thanks Tony, that is looking like the best option as I was planning to purchase a Smartgauge anyway, but hadn't appreciated that the Smartbank would cover all the charging needs. To be honest I had just seen it as a split charge relay and not fully understood the rest of it.

 

What I still can't tell though is will it use both alternators? It would be handy to know as I have two available. The diagrams on the Smartgauge website only show one and I don't see any mention of paralleling.

 

Yes it will use both alternators. Though as Arnot points out, that doesn't always make the huge difference people expect. It depends on the size of the alternators in relation to the size of the battery bank and whether they are spinning fast enough.

 

It does however give a built in back up in that once installed, if any one part (ie the split charge system or one of the alternators) packs in the entire system continues to function albeit with reduced charge capability. But that's better than no charge at all.

[bobbynell]

Yes it will use both alternators. Though as Arnot points out, that doesn't always make the huge difference people expect. It depends on the size of the alternators in relation to the size of the battery bank and whether they are spinning fast enough.

 

It does however give a built in back up in that once installed, if any one part (ie the split charge system or one of the alternators) packs in the entire system continues to function albeit with reduced charge capability. But that's better than no charge at all.

Thanks that's perfect. Even if it's just a small difference using both I think it's better than making one of them redundant.

[colin stone]

My 2 euro cents.

 

1. Change alternator(s) pulleys to get alternator to reach max speed, often from 8000 on large 24v Leece Neville alts up to 16000 rpm on car alts, at max engine revs. This will increase amps from alternator at idle and canal trundling speeds. I changed my pulley ratios from 2:1 to 4.35:1.

 

2. Fit SBank/Sguage and relay.

 

3. If still after more volts/quickest recharging do the alternator mod with diodes as described on SG website - this may well require electrician to get inside alternator(s). Agree wait a few months until warranty has expired if neccessary.

 

4. One advantage of having lots of alternator amps is that power hungry consumers can run whilst motoring - washing machine/tumble drier/oven/hoover/iron without taking amps out of the battery.

 

Simple solutions with no power wasted.

[bobbynell]

That makes a lot of sense, and something to get sorted quickly.

 

This may be obvious when I get back to the boat - but how can I tell what the pulley ratio is now?

[RLWP]

That makes a lot of sense, and something to get sorted quickly.

 

This may be obvious when I get back to the boat - but how can I tell what the pulley ratio is now?

 

to get a rough idea measure the diameters of the pulleys. So, if the crankshaft pulley was 4" and the alternator was 1" you'd have a ratio of 4:1.

 

Richard

 

I made those figures up by the way to make the sums easy.

[Gibbo]

I made those figures up by the way to make the sums easy.

 

Isn't that what politicians do?

[RLWP]

Isn't that what politicians do?

 

I'll ignore the mortal insult in that statement

[Helga]

This topic is of considerable interest to me as I plan to have a boat built very soon and become a 'grey nomad'. I've looked at specifying a Sterling ABC but am now wondering whether there might be a better option?

 

My plan is to have three battery banks (starter battery 12v AGM 135AH; bow thruster 2 x 12v AGM 135AH; and domestic bank 6 x 6v 395AH). My proposed engine has 1 x 175A and 1 x 50A alternator and I'd like to combine the alternator outputs; primarily for the large domestic bank. I was concerned the Sterling 210A ABC might be underpowered and don't really understand whether the SmartBank can cope with the combined output. Interested in which option to select?

[GSer]

A generator and combi is probably not a good way to go, as you acknowledge it adds complexity as well as this is increases cost and lowers reliability. Combi's are great as long as you have a shore line and better yet if the boat is left unused for lengthy periods but if you have to power them from a generator is is not always very successful and unless you have a massive battery and combi, not as quick to charge the batteries.

 

 

This is getting me worried, so apart from complexity, what sort of performance can I expect from my set up? I'm livaboard and I tend to be away from shorelines for most of the year. I have a Kholer 7kva genny, a Victron Quattro 12/3.5kw/120amp combi, a SmartBank/SmartGuage setup, 6x110ah service pack. The boats engine, a Gardner 2LW, has a 140amp alternator fitted. Charging times are limited to approx 1.5 hrs a day most days after work and the whole weekend to catch up if needed(I hope).

 

I didn't fancy running the old engine for battery charging on a regular basis while moored, hence the genny. We are going back to having a washing machine again! (long story ) and are going to utilise the genny running time to operate two 1kw immersion heaters in the two calorifiers for hot water when the main engine is resting, hence the 7kva (still over the top but it was the same price as a 4.5KVA unit to buy)

 

I was hoping this would be an improvement over my last boats set up of, no generator, a 50 and 70 amp engine driven alternators, an adverc, a 660ah service pack, 120watt solar array, A stirling 12v 2.5kw 50 amp combo was fitted. We were always playing catch-up with this setup and it was rare to go more than a day or two without charging the service pack. It was also strange that it appeared there was an opimum charge time, to much would lead to a poorer charge condition later the following week.

 

I would appreciate your views on the suitability of the new boats setup.

 

Paul

[WotEver]

I'll ignore the mortal insult in that statement

Oh, but you shouldn't

 

This topic is of considerable interest to me as I plan to have a boat built very soon and become a 'grey nomad'. I've looked at specifying a Sterling ABC but am now wondering whether there might be a better option?

 

My plan is to have three battery banks (starter battery 12v AGM 135AH; bow thruster 2 x 12v AGM 135AH; and domestic bank 6 x 6v 395AH). My proposed engine has 1 x 175A and 1 x 50A alternator and I'd like to combine the alternator outputs; primarily for the large domestic bank. I was concerned the Sterling 210A ABC might be underpowered and don't really understand whether the SmartBank can cope with the combined output. Interested in which option to select?

My opinion, others may disagree...

 

You don't mention an inverter. Assuming you'll have one then the easiest way to recharge the bow thruster batts and avoid huge runs of huge, hugely expensive cables to them will be to have a small local intelligent charger located next to them, fed by the inverter's 240V. (The first time I've managed to get two huge and a hugely all in one sentence.)

 

A Smart Bank will parallel the batteries (and hence the alternators) intelligently so you will have a potential 225A for recharging your domestic bank. However, if the bank will take 225A for more than a few minutes then the batteries ain't going to last that long, so the benefit is dubious. Nevertheless it will achieve the result you're after.

 

:::awaits incoming:::

 

Tony

[GUMPY]

This is getting me worried, so apart from complexity, what sort of performance can I expect from my set up? I'm livaboard and I tend to be away from shorelines for most of the year. I have a Kholer 7kva genny, a Victron Quattro 12/3.5kw/120amp combi, a SmartBank/SmartGuage setup, 6x110ah service pack. The boats engine, a Gardner 2LW, has a 140amp alternator fitted. Charging times are limited to approx 1.5 hrs a day most days after work and the whole weekend to catch up if needed(I hope).

 

Set the Victron up correctly an use the genset every day for as long as you can.

I manage with a similar system but it takes about 2.5hrs to charge every day, that's from 75-80%. SG gets to 100% after about 1.75hrs but as I have 2.5hrs I use it.

My charge voltage is 29.8v so in 12v terms that's 14.9 quite high I know, but it works for me because I am not doing it every week as I spend a lot of time on a shore line.

Its quicker and simpler for me to charge from the genset and combi than to use the engine.......

[Arnot]

This is getting me worried, so apart from complexity, what sort of performance can I expect from my set up? I'm livaboard and I tend to be away from shorelines for most of the year. I have a Kholer 7kva genny, a Victron Quattro 12/3.5kw/120amp combi, a SmartBank/SmartGuage setup, 6x110ah service pack. The boats engine, a Gardner 2LW, has a 140amp alternator fitted. Charging times are limited to approx 1.5 hrs a day most days after work and the whole weekend to catch up if needed(I hope).

 

I didn't fancy running the old engine for battery charging on a regular basis while moored, hence the genny. We are going back to having a washing machine again! (long story ) and are going to utilise the genny running time to operate two 1kw immersion heaters in the two calorifiers for hot water when the main engine is resting, hence the 7kva (still over the top but it was the same price as a 4.5KVA unit to buy)

 

I was hoping this would be an improvement over my last boats set up of, no generator, a 50 and 70 amp engine driven alternators, an adverc, a 660ah service pack, 120watt solar array, A stirling 12v 2.5kw 50 amp combo was fitted. We were always playing catch-up with this setup and it was rare to go more than a day or two without charging the service pack. It was also strange that it appeared there was an opimum charge time, to much would lead to a poorer charge condition later the following week.

 

I would appreciate your views on the suitability of the new boats setup.

 

Paul

Sounds pretty good to me... As far as I can see you have all bases covered and the way you intend to operate it should be fine.

 

The comment I made on generators was more aimed at the portable plug in type, the built in ones. I am not familiar with the Kohler 7kVA unit and can't find any information on it, do you have a URL? Also I am not familiar with the Victron Quattro 12/3.5kw/120amp combi, I know of a 12/3000/120 and a 12/5000/200...

 

It would probably be a good idea to use the battery sense feature on the Victron Combi to reduce charging times and have the unit set up using the VE Configure software once installed. The settings as they are shipped could almost certainly be improved.

 

You might also want to consider a rather better battery bank. Given the amount you have allocated for the charging systems, six boggo leasure batteries seem a bit out of place. Traction cells would give better performance and despite the initial hit would cost less over time.

 

Regards

 

Arnot

[Arnot]

This topic is of considerable interest to me as I plan to have a boat built very soon and become a 'grey nomad'. I've looked at specifying a Sterling ABC but am now wondering whether there might be a better option?

 

My plan is to have three battery banks (starter battery 12v AGM 135AH; bow thruster 2 x 12v AGM 135AH; and domestic bank 6 x 6v 395AH). My proposed engine has 1 x 175A and 1 x 50A alternator and I'd like to combine the alternator outputs; primarily for the large domestic bank. I was concerned the Sterling 210A ABC might be underpowered and don't really understand whether the SmartBank can cope with the combined output. Interested in which option to select?

If the engine is the one I thnk it is - Beta 43? - then the alternators fitted are pretty damn good. Just improve the cable from the 175A alternator direct to the domestic bank and leave the charging at that. You could combine the outputs but I honestly think that the cost and complexity will not be justified by the marginal improvement in charging time. Despite this, if you do want to go ahead with this one, I wouldn't bother with the Sterling. The SmartBank can easily cope and is far better suited to the application.

 

I definitely think you could do with a reconsider of the batteries. A 135Ah AGM for the starter is a lot larger than is necessary unless I have my engine guess a really long way out. I takes typically about 0.2Ah fo start a small diesel and the 50A alternator could replace this in minutes. AGM's give a longer service life and usually better starting current but it's debatable if the benefit is cost effective over a standard lorry battery. Taking it to a ridiculous extreme, the other day I did show someine that it was possible to start a narrow boat engine with a 1Ah battery about the size of two fag packets, it was warm though.

 

Two of the AGM 135Ah batteries for the bow thruster is IMHO well over the top. Once you have got over the fun of playing with it, my experience of bow thrusters is that they are rarely used and even then only for a very short time. I did once monitor the current that one was taking and it was only about 100A, even if you use it 5 minutes a day to do pirouettes, this is still less than 10Ah of battery capacity. Perhaps a single and possibly smaller battery would do the job.

 

Now the domestics, It looks as though you have specified semi traction batteries and at 1185Ah when connected for 12V this should give you all you need.

 

Hope this helps

 

Regards

 

Arnot

[nb Innisfree]

Said it before so it's getting boring but we have a large frame 100a 24v Leece Neville alternator, pricey but runs from a LP Alpha Canalstar at 2:1 pulley ratio, nice big 3" double alt pulley gives plenty of grip so no need to keep adjusting tension, a good charge from low rpm, no messing with small alt pulleys with attendant grip probs. Simple system with OTT alt cables, just charges domestics and works a treat without a charge controller, though we do a daily bulk charge from alt and weekly 8hr absorption charge from Victron and Kipor genny. Done.

 

We have 2 x 160 ah AGM's for our bowthruster and when it was working (don't ask) there was more than enough power and I think just one battery would easily have sufficed, as previously said you can only use BT for short periods and it will overheat long before batts discharge. Just make sure you have a decent 3 stage charger run from a decent inverter and give them a long recharge, saves a lot of bother with voltage drop etc trying to charge from an alternator. IMO

Edited July 20, 2010 by nb Innisfree

[Helga]

If the engine is the one I thnk it is - Beta 43? - then the alternators fitted are pretty damn good. Just improve the cable from the 175A alternator direct to the domestic bank and leave the charging at that. You could combine the outputs but I honestly think that the cost and complexity will not be justified by the marginal improvement in charging time. Despite this, if you do want to go ahead with this one, I wouldn't bother with the Sterling. The SmartBank can easily cope and is far better suited to the application.

 

I definitely think you could do with a reconsider of the batteries. A 135Ah AGM for the starter is a lot larger than is necessary unless I have my engine guess a really long way out. I takes typically about 0.2Ah fo start a small diesel and the 50A alternator could replace this in minutes. AGM's give a longer service life and usually better starting current but it's debatable if the benefit is cost effective over a standard lorry battery. Taking it to a ridiculous extreme, the other day I did show someine that it was possible to start a narrow boat engine with a 1Ah battery about the size of two fag packets, it was warm though.

 

Two of the AGM 135Ah batteries for the bow thruster is IMHO well over the top. Once you have got over the fun of playing with it, my experience of bow thrusters is that they are rarely used and even then only for a very short time. I did once monitor the current that one was taking and it was only about 100A, even if you use it 5 minutes a day to do pirouettes, this is still less than 10Ah of battery capacity. Perhaps a single and possibly smaller battery would do the job.

 

Now the domestics, It looks as though you have specified semi traction batteries and at 1185Ah when connected for 12V this should give you all you need.

 

Hope this helps

 

Regards

 

Arnot

 

Thanks for the reply and you're correct... I'm considering the Beta 43. I was considering AGM batteries for the starter and bow thruster because of their low maintenance and they may be in a location that is slightly difficult to access. The cost of the second bow thruster battery is small when compared to the overall build cost. However I'd certainly consider a single battery if space becomes a critical issue. My major concern is the ability to keep the 1185Ah domestic bank charged. Assuming the charger needs to be a minimum of 25% the size of the bank, then I need to supply 300A. Hence the intention to combine the alternator outputs. However finding a suitable charger appears to be an issue. Sterling have the largest charger (210A) and I don't really understand the operation of the SmartBank. If it is capable of handling the maximum combined alternator output then it looks like a better option.

[Gibbo]

If it is capable of handling the maximum combined alternator output then it looks like a better option.

 

Yes it will handle it. Easily.

 

In reality all it has to handle is the extra charge from the engine start alternator going into the domestic battery. The charge from the domestic alternator goes directly to the batteries so doesn't go through the relay. The relay that comes as standard is 200 amps continuous (that's a real 200 English amps not 200 asian amps).