Battery charging

[Kantara]

I’m slowly going bananas. Please help me, but be gentle.

I have a 20 year old Westerly with the original engine, a VP2003T and, according to the workshop manual, a 14V 50A alternator. This feeds through a rotary ‘Off’, ‘1’, ‘Both’, ‘2’ switch into 3 120AH maintenance free batteries, one of which is connected to the ‘1’ position and is used as engine start, the other 2 of which are linked together as the Services Bank.

The boat is on a swinging mooring and we are very careful of power usage, only running the fridge when under power, for example, and using only one light in the cabin when anchoring overnight. The long summer evenings in the West of Scotland help there! However, we hope to extend our cruising this coming year, spending much longer under sail and at anchor, and I have been considering ways of boosting our electric efficiencies.

I was pretty convinced that an alternator regulator was the answer, having read the Sterling and Adverc websites. However, the recent thread on Alternator Regulators pointed me in the direction of SmartGuage where the view was that Alternator Regulators weren’t really needed these days and their version of Charge Splitting was the bees knees.

I realise that this is similar to starting an ‘anchors’ thread, but what does the team think? Are Smartguage right when they say that Alternator Regulators are old hat? If it is considered that a SmartBank is all that is required, is a Standard sufficient, or is the all singing and dancing Advanced version more than just a ‘nice to have’?

 

[Billjratt]

I googled Smartguage, and it seems to be a battery condition monitor. So it will tell you all about the state of charge, or otherwise, but it won't DO anything about it.
Smart controllers add a little intelligence to the existing alternator circuit, and "force feed" the batteries, thus bringing them up to a "fuller" level than normal, and quicker. All this means that you can run the engine for shorter periods to achieve a good charge (or replace what you used overnight). The products appear to complement each other rather than the "either-or" situation you infer above.

 

[theforeman]

can i humbly suggest that i think you have misunderstood the smartguage / bank position. as i understand the position the smartbank makes the rotary battery switch " old hat " rather than the alternator regulator. for what it is worth the smartguage / bank manufacturer advised me last year that, so far as they were concerned, there was no difference between any of the smart alternators on the market - all would work equally well with their products.
i have a second hand adverc alternator controller to be fitted before lift in. i also intend to fit a smartguage battery monitor at some point.
from your intended change in cruising mode should you not also be considering a wind genny and / or a solar panel ?

 

[halcyon]

If you have a alternator regulating around 14.3 volt, a smart regulator will not do lot of good.

If your regulator is running at 13.6 volt, then a smart regulator will do a lot.

For the last 25 years I have told people, if you do not have a problem, then a new alternator regulator will not make it any better, if you have a problem buy one.

The Smartgauge charging system is a VSR.

Brian

 

[sailorman]

I Have One of These

Under £70.00

 

[halcyon]

[ QUOTE ]
I Have One of These

Under £70.00

[/ QUOTE ]


I started building those in 1978. /forums/images/graemlins/smile.gif

Brian

 

[sailorman]

yes you said b 4 & jolly good they are 2 /forums/images/graemlins/wink.gif

 

[mldpt]

Hi I know little about this subject but I would say that if you alternator is the original 50amp Paris Rhone then it will not output much more than 25 amps, and as I understand it you can not hope to fully charge 360amphours of battery with it. when I had my Westerly corsair it had two 60 amphour batteries and the same alternator as yours, and it was a struggle to charge them. A smart charger will I don't think make your 50amp charge any more than that and it would still take ages to put back 360 amhours back in. I have got an Adverc alternator 90amp and smart charger with three 100Amp batteries a wind generator, and mains charger, and still run short of volts and amps. However i have loads of toys on board. You are doing well to still be useing the original alternator after so long.
Regards Mike

 

[William_H]

Battery charging current is usually limited by the inherent voltage of the battery but under some conditions can be limited by the rating of the alternator. An alternator is usually rated at eg 50 amps but giving barely more than 12v due to internal losses. So into a huge battery bank it would produce much less current at 14v. As the current of the alternator rises the voltage falls (when running at full; capability) so current into the batteries fall. This is in practice the limit of the alternator

If you have a large alternator which is not current limited. If you have an alternator giving 13.75 volts then into each 110AH battery if half discharged you would initially get 20 amps which after 5 mins would fall to 10 amps and after 30 mins would fall to 5 amps.
If the alternator gives 14v then you would start at 20 amps and after 5 mins fall to 15amps then after 30 mins to 8amps.
A smart regulator will in effect charge at 14.7 volts so start at 20 amps but still push in 20 amps after 5 mins and 15 amps after 30 mins. When it considers the battery is charged it will reduce the voltage so reduce current dramaically to avoid overcharging the battery.
Note here that 3 batteries in parallel will each take this much current so the 50A alternator is likely to self limit the current anyway to perhaps 30 amps total.
These figures are really only typical to show how a smart regulator may be a good thing for you in getting more Amp hours into the batteries for a limited engine run time. But you may need a bigger alternator to get the real benefit.
What you really need is am amp meter or as described a totalising AH meter which can show when engine running is puting a lot into the batteries and when further engine run will have little benefit.
I suspect that you may find with your large battery capacity and limited alternator power that you are probably doing OK as is. Perhaps a wind gen or maybe solar would help more. just a few thoughts olewill

 

[lw395]

As a start, I would sort out a decent Voltmeter. Depending on your alternator, much of your motoring may be at too low revs to feed both the fridge and two hungry batteries. A more modern alternator will give more amps at low revs.
If the volts rise when you switch the fridge off, then the alternator is limiting the system.
In the Yanmar manual there is a graph of Alt. current vs RPM, which shows that a typical old-style alternator will barely do the fridge at tickover. This will get a bit worse if you have splitter diodes. A modern alternator e.g, Bosch from a mondeo (scrapyard, £25), has a much different curve, plenty of amps at low rpm to cope with heated screens, seats and whatever.
On the other hand, there are limits to how fast you can charge a battery.
When it comes to spending money, its a choice between more batteries, alternative generation or smart controller.
The voltmeter should help you see what's happening!

 

[halcyon]

[ QUOTE ]
Battery charging current is usually limited by the inherent voltage of the battery but under some conditions can be limited by the rating of the alternator. An alternator is usually rated at eg 50 amps but giving barely more than 12v due to internal losses.

[/ QUOTE ]

Alternators are normally rated at 14 volt, and were rated in watts not amps.

The one thing is that the alternator load from the boats services ( lights, nav equip, fridge etc ), is different to that with charging a battery. This can limit the voltage you see if the service loads are high, and this limits charge voltage. The alternator regulator has no effect on this voltage, as it only limits top end voltage, thus does not work till you get there.

So first job is always, ...... what voltage do you regulate at.

Brian

 

[Robin]

A lot depends on what you are trying to achieve but for sure your current setup could be improved. Firstly look at what you really want to achieve and how far you will go to do it.

Some basic comments:-

1) A fridge is not a fridge unless you can run it 24/7, other wise it is only a cold box.
2) Running an engine long periods under no load merely to charge batteries is not good for the engine.

We had a similar arrangement to yours on our last boat a W33 Ketch which when we bought it had only a 27A (memory) alternator but that was irrelevant because after 10 minutes it was charging only at a few amps. It was pointless changing the alternator because it was the regulator that was holding the charge rate down, so we bought a smart regulator( a TWC) and now we had some amps, OK no more than 20A of the theoretical 27A but what we had stayed and didn't vanish after a few minutes.

Then we re-engined and the new engine came with a 55A alternator so we did some system changes overall. First of all we dumped the 1-2-both-off setup and added a split charge diode system and secondly we added a small engine start battery so that the others could all be used for services. The small cranking battery was a car type, cheap enough and put in a plastic battery box in a nearby locker. We fitted a new Adverc regulator which controlled the alternator output via the split charge diode to the batteries, most of the charge going to the service batteries as the small engine start one was charged in minutes after a start. The sense lead for the regulator was connected to the service bank and the Adverc reacted to the voltage found there and adjusted the alternator accordingly to set that around 14.4v initially and drop to 13.6v float with a full battery. At least now when the engine was running it was charging pretty good.

We then added an Aerogen4 wind generator. We were on a mooring then and if we returned with low batteries on a Sunday they were full by the following Friday. At anchor the wind genny helped with the load including the fridge which always ran 24/7 when we were on board.

For when we had shorepower we had a 25A smart charger. We bought a small Kawasaki petrol generator that would just run this if needed as well so at anchor after a day or so an hours run would top up what the wind genny hadn't.

Later we added a 110W solar panel which we kept in the stern cabin storehouse on the W33 (we slept up front) and put on deck as needed. We were now pretty well self sufficient, never ran the engine unless motoring and the Kawasaki was taken home.

Our current boat has enough power capability to run the street! We have two alternators (1 x 60A and 1x 90A) both with Adverc regulators. One charges the engine start battery and one service bank and the other charges the other service bank. Either or both service banks can be switched to start the engine if needed. We then have a fixed 75W solar panel on a gantry and a big Aerogen6 wind genny, plus the 110W solar panel we kept from the old boat. There is also a 40A smart shorepower charger for when we are plugged in. In practice now the wind genny isn't used much unless we are at anchor for very long periods, for a Friday/Sunday weekend the fixed solar panel is enough on it's own. At anchor for days on end with the 110W panel out as well we frequently have to turn off or disconnect some of the power to avoid overcharging because from choice the solar panels are regulated by me and switches although the wind genny is regulated.

So just how far do you want to go to suit your plans? I think whatever you do you need information so a good voltmeter and ammeters are essential. We have ammeters on each solar panel and the wind genny as well as the alternators and voltmeters on each battery bank but we don't have one of the modern totalising ampere hours meters that measures what is taken and what is replenished. Personally I prefer the split charge diode system with no moving parts to the relay VSR types but maybe I'm a Luddite.

BTW we used to cruise our W33 with friends who had a Westerly Seahawk and we would keep their food in our fridge for them so we could anchor out, otherwise they had to be plugged in to run their fridge, very restricting!

 

[lw395]

[ QUOTE ]

Some basic comments:-

1) A fridge is not a fridge unless you can run it 24/7, other wise it is only a cold box.


[/ QUOTE ]
Unfortunately a lot of new yacht builders and buyers are prepared to believe this. With adequate heat capacity and insulation it is possible to design a fridge that doesn't need this. But the boats that sell well seem to have huge fridges with little insulation, often close to the cooker, engine or the fridge compressor.
It's worth looking at the demand side of the equation too!

 

[Robin]

[ QUOTE ]
Unfortunately a lot of new yacht builders and buyers are prepared to believe this. With adequate heat capacity and insulation it is possible to design a fridge that doesn't need this. But the boats that sell well seem to have huge fridges with little insulation, often close to the cooker, engine or the fridge compressor.
It's worth looking at the demand side of the equation too!

[/ QUOTE ]

Sadly very true.

On our old W33 we had a factory option small top loading cabinet under the starboard bunk which we had to fit a new compressor to get working. We also added a better lid seal and clamp to hold it tightly closed and filled the entire area around it with insulation.

On our current one the fridge is top loading and huge but Jeanneau insulated it pretty well. What we have done however is to cut some expanded polystyrene blocks to shape, covered with foil, and fit them under the two wire baskets in the bottom which provides additional insulation and reduces the volume. For weekend use we also take on board with us a bottle of frozen water (or tonic..) which gets the fridge off to a good start when it will not be anywhere near full. Once in longer cruise mode the fridge is kept pretty full and once everything is cooled down it stays like it using much less power. Adding lots of newly acquired bottles at ambient temperature takes ages to chill down!

 

[William_H]

Hello Brian my claim on rating of alternators is really based on cycnicism rather than actual knowledge.
It is nased onn the fact that an alternator is generally made for a motor vehicle where the demand is to drive systems ie lights heaters ignition etc.
These systems will run on 12v although really designed to run on 13.75 to 14v regulated system voltage. (A suitable voltage to float a battery long term.) So an alternator on a vehicle is likely to max out with load (not normally battery charging) hence my reckoning that max current would be at 12v output. Of course I could be wrong and makers could rate their alternators conservatively at max current at 14v output. (but I doubt it)
Hence my suggestion that max current while holding up 14v (needed for battery charging) might be a lot less than the rated current. No I havn't heard of them being rated in watts but then I have been away from the industry for some time. olewill