Battery Set Up + Extra Alternator??

[Posset]

The boat I have just purchased has 1 starter and 2 leisure batteries which are linked to a large round knobbed isolator which will select starter battery only, leisure batteries only or all at the same time. It only has one alternator to charge all or some of the batteries depending on what is selected on the isolator.

 

I was informed that if all batteries are selected and the engine is not running the starter battery will get drained along with the leisure batteries. I have also found the engine will start from either bank of batteries which are selected.

 

 

 

Questions are-

 

Is this a normal single alternator set up?

Can it be set up like a twin alternator set up but with only one alternator (like a split charge system on say a caravan)?

Would it be difficult to add a second alternator and have two isolators like other boats I have hired?

 

BTW, The engine is a Throneycroft Mitsubishi

 

Regards

 

Simon

[RobinJ]

Questions are-

Is this a normal single alternator set up?

Can it be set up like a twin alternator set up but with only one alternator (like a split charge system on say a caravan)?

Would it be difficult to add a second alternator and have two isolators like other boats I have hired?

Common especially on GRP cruisers!

Yes, you could fit either a dplit charge relay,

or dual alternator set up to charge both banks.

 

Advantage of present system, engine can be started form either battery bank, can charge banks together or independantly.

Disadvantage, have to remember to alter switch!

[Posset]

 

 

Advantage of present system, engine can be started form either battery bank, can charge banks together or independantly.

Disadvantage, have to remember to alter switch!

[/quote

 

The problem is my memory is rubbish and I am bound to end up stuck somewhere lol.

 

I don't know if I fancy a split charge relay type system as from past experience they aren't to reliable and you don't know if its working correctly until something stops working, unless they have improved in recent years

 

Has anyone got any wiring diagrams for a twin alternator set up?

[Tony Brooks]

 

The problem is my memory is rubbish and I am bound to end up stuck somewhere lol.

 

I don't know if I fancy a split charge relay type system as from past experience they aren't to reliable and you don't know if its working correctly until something stops working, unless they have improved in recent years

 

Has anyone got any wiring diagrams for a twin alternator set up?

 

 

I have to disagree about split charge relays. They probably are unreliable if the rely is not suitably specified and/or the main charge goes to the engine battery but as long as you have a quality relay and feed the main charge to the domestic bank it should be fine - is 12 years without a problem reliable enough? And that's with a simple Lucas split charge relay.

 

If you occasionally stick a voltmeter between both bank's positives at first start it will read voltdrop across the wires and relay so you know when the contacts start to play up. I would suggest every couple of months or so.

 

If you want to build in charging redundancy then go for twin alternator setup and I think you will find the diagrams you need on my website but on many engines getting the second drive is not that easy or cheap. The engine alternator will spend most of its time doing not a lot.

 

If you are experiencing lack of charge then I would go for a larger alternator (Max about 80 amps on a small V belt) or fit twin alternators. If you just want reliable charge splitting then an Albright relay and suitable wiring modifications would be the easiest way to go. If you want redundancy then just carry a spare alternator because that way you avoid the cost and hassle in extra mountings, pulley, and drive belts.

[Timleech]

 

 

Advantage of present system, engine can be started form either battery bank, can charge banks together or independantly.

Disadvantage, have to remember to alter switch!

 

The problem is my memory is rubbish and I am bound to end up stuck somewhere lol.

 

I don't know if I fancy a split charge relay type system as from past experience they aren't to reliable and you don't know if its working correctly until something stops working, unless they have improved in recent years

 

Has anyone got any wiring diagrams for a twin alternator set up?

 

Mine will have separate start and 'domestic' batteries and alternators, with a Voltage sensitive relay to connect the two when running, which will in effect roughly double the alternator capacity of the domestics most of the time. The particular relay can also be switched in manually to provide emergency starting. I don't see any real downsides to what is a fairly simple setup, but others might pick holes in it? It's not a normal narrowboat liveaboard or floating cottage arrangement, rather it's a small simple boat with occasional high demand, but I don't see why it wouldn't work in either case.

 

Tim

[Posset]

Thanks Tony I will look at your website. I think I could wire up a split charge system if I had a diagram lol.

 

I don't suppose you have a diagram Tim?

 

The boat only has a 12v system at present but I am thinking about putting my 3kv generator (which also has a 12v output) on it somewhere if I can find a suitable space.

[Keeping Up]

Just to ensure that you are certain of the correct way to use your existing setup - which used to be very common indeed:

 

You should start the engine on the starter battery only.

 

Once the engine has been running for a few minutes, switch over to charge both batteries.

 

When you stop the engine, change to just the domestic batteries.

 

In emergency, if you have flattened the starter battery, you can try to start the engine on the domestic batteries. But don't make a habit of it.

[Posset]

Just to ensure that you are certain of the correct way to use your existing setup - which used to be very common indeed:

 

You should start the engine on the starter battery only.

 

Once the engine has been running for a few minutes, switch over to charge both batteries.

 

When you stop the engine, change to just the domestic batteries.

 

In emergency, if you have flattened the starter battery, you can try to start the engine on the domestic batteries. But don't make a habit of it.

 

I was thinking exactly that but the isolator says not to change the setting with the engine running as it could damage the alternator.

[Keeping Up]

I was thinking exactly that but the isolator says not to change the setting with the engine running as it could damage the alternator.

 

 

Does the isolator go all the way around so that it passes in sequence through batt 1, both, batt 2, neither, and back to batt 1 again? Most of them do that. If so, it should be perfectly OK to change from either battery to "both" while the engine is running; but don't ever change from one battery to the other via "neither" because that will blow the alternator.

[Posset]

Does the isolator go all the way around so that it passes in sequence through batt 1, both, batt 2, neither, and back to batt 1 again? Most of them do that. If so, it should be perfectly OK to change from either battery to "both" while the engine is running; but don't ever change from one battery to the other via "neither" because that will blow the alternator.

 

I don't know, I will try it at the weekend. If the sun comes out lmao.

[Timleech]

Thanks Tony I will look at your website. I think I could wire up a split charge system if I had a diagram lol.

 

I don't suppose you have a diagram Tim?

 

The boat only has a 12v system at present but I am thinking about putting my 3kv generator (which also has a 12v output) on it somewhere if I can find a suitable space.

 

No diagram, sorry.

Essentially two separate charging systems, with the VSR wired between them following maker's instructions.

 

I'm not sure whether the one I have, with the manual override switch, is still available (from BEP)?

You can always arrange your own 'override' by adding an extra isolating switch between the two battery banks.

 

Tim

Edited January 23, 2013 by Timleech

[by'eck]

Mine will have separate start and 'domestic' batteries and alternators, with a Voltage sensitive relay to connect the two when running, which will in effect roughly double the alternator capacity of the domestics most of the time. The particular relay can also be switched in manually to provide emergency starting. I don't see any real downsides to what is a fairly simple setup, but others might pick holes in it? It's not a normal narrowboat liveaboard or floating cottage arrangement, rather it's a small simple boat with occasional high demand, but I don't see why it wouldn't work in either case.

 

Tim

 

Just one potential issue - will the VSR, switched on manually or automatically, be able to carry a large part of the starter motor current in the case of a flat starter battery?

[Timleech]

Just one potential issue - will the VSR, switched on manually or automatically, be able to carry a large part of the starter motor current in the case of a flat starter battery?

 

The one I have has a pretty high rating, can't remember but maybe two or three hundred amps, I'll check when I get a chance, plus it's on a 24V system. It looks like this, but it's actually a VSR. I wouldn't expect the whole starter current to pass through it, though I suppose a situation could arise where someone unfamiliar with the system took the starter battery off for recharging & still tried to start 100% via the VSR.

 

Tim

[by'eck]

You will probably never have a problem, but I tend to look at worst case scenario's. Even with a near flat starter battery present, most of the current will pass through the relay when its switched on and connected to a charged service battery bank.

 

I know you can't compare but FWIW my 12 volt 9hp Nobels bowthruster blew a 500 amp fuse when it was partially jammed by remnants of a re-enforced plastic sack. This after a few seconds of use and before the thermal cut-out tripped.

[Arthur Brown]

If you intend to cruise a lot then the single alternator setup will be fine, just remember to separate the starter battery before you settle for the night. If you will end up running the engine to charge batteries then a better plan would be to have an additional alternator fitted to the engine to make more use of the fuel used while the engine is only lightly loaded.

[Timleech]

You will probably never have a problem, but I tend to look at worst case scenario's. Even with a near flat starter battery present, most of the current will pass through the relay when its switched on and connected to a charged service battery bank.

 

I know you can't compare but FWIW my 12 volt 9hp Nobels bowthruster blew a 500 amp fuse when it was partially jammed by remnants of a re-enforced plastic sack. This after a few seconds of use and before the thermal cut-out tripped.

 

I've just dug out the ratings for my VSR, 300A continuous, 1500A for 10 seconds. It is specifically intended for emergency paralleling for engine starting.

 

Tim

Edited January 23, 2013 by Timleech

[Posset]

Thanks Tim, that VSR looks like a decent bit of kit and will probably be the way I will go if I have any problems .

[Timleech]

Thanks Tim, that VSR looks like a decent bit of kit and will probably be the way I will go if I have any problems .

 

I dropped lucky in that I got mine as ex-demo for a fraction of list price. Sometimes there are side benefits to a 24Volt system, slightly better chance of picking up bargains.

Some big-selling stuff from the chandlers it works the other way.

 

Tim

[Fred_Smith]

I have Durite VSR's, that can be bought for £30 to £40 12v 300 Amp, from a vehicle parts distributor however if you buy the same kit, possibly under a different name but identical they will cost considerably more as you are paying for the word "marine"

[ditchcrawler]

I have Durite VSR's, that can be bought for £30 to £40 12v 300 Amp, from a vehicle parts distributor however if you buy the same kit, possibly under a different name but identical they will cost considerably more as you are paying for the word "marine"

http://www.google.co.uk/products/catalog?q=Durite+VSR&rlz=1C1CHFX_enGB519GB519&um=1&ie=UTF-8&cid=5943206536556374210&sa=X&ei=ZSQBUY_yNMOU0QGtqoGwDA&ved=0CFIQ8wIwAg

[Timleech]

http://www.google.co.uk/products/catalog?q=Durite+VSR&rlz=1C1CHFX_enGB519GB519&um=1&ie=UTF-8&cid=5943206536556374210&sa=X&ei=ZSQBUY_yNMOU0QGtqoGwDA&ved=0CFIQ8wIwAg

 

Note that one is rated at 140A, & is a basic VSR without the emergency parallel facility.

The BEP equivalent is here.

 

Tim

[vicafloat]

The Smartgauge website has a good reputation;I have one 70amp alternator and a Smartbank fitted by Nick Bancroft

of the Paintshed. This works fine but I have had problems with standard split charge relays over-heating.

[Tony Brooks]

The Smartgauge website has a good reputation;I have one 70amp alternator and a Smartbank fitted by Nick Bancroft

of the Paintshed. This works fine but I have had problems with standard split charge relays over-heating.

 

 

However the question is how was it and the main charging system wired?

 

Most single alternator boats wire the alternator output to the main battery terminal on the starter so all the charge flows to the engine battery (as one would expect). Ideally the main charging cable would run straight to the engine battery master switch but to save cable cost and minimise the complexity of fitting the engine most are wired as I said.

 

When a split charge relay is fitted all too often it is simply connected between the two batteries with no other work done to the charging circuit. Unless there is a fault on the engine/engine battery the engine battery will all but always be well charged BUT the domestic battery will usually be well discharged. This means that virtually ALL the alternator output plus some of the engine battery's charge will flow through the relay and in all too many cases cause overheating.

 

What should have been done is to move the main alternator output cable to the DOMESTIC battery master switch (assuming best practise positive switching) or battery if you want to risk the BSS. Now what happens is the flat domestic battery takes virtually all the charge from the alternator. The engine battery will have a higher volatge than the domestic bank so the domestic bank can not try to charge the engine battery meaning the current flow through the relay will be low.

 

We can argue about how we energise the split charge relay and what implications that may have but to be honest I am getting a bit fed up with people (not directed at Vicafloat) who should know better bad mouthing relays because they had not been fitted correctly. As I have said in other posts, a 120 amp Lucas relay (looks like the Durite one to me, both inside and out) in use for about 12 years with no problem so far.

 

The reason the Smartbank setup is so reliable is that the relay supplied is far superior to any "off the shelf" split charge relay and is really more of a solenoid - although I have seen one of these fail. It also hold off energising the relay for a time after charging starts.

[Posset]

Well we finally managed to get the boat out for our maiden voyager yesterday and returned to the marina this morning.

 

We had the engine running with the isolator set to both for around 4hrs yesterday, last night when we moored up I turned the isolator to the leisure batteries only. Whilst watching tv last night the leisure batteries started to get low and the tv went off. All we had turned on was a couple of small 10-12" fluorescent tube lights, the fridge and the TV and the batteries only lasted about 4.5hrs tops.

 

How long should they last without the engine running? I noticed last week whilst at the marina that the voltmeter on the boat doesn't go much above 12v with the engine running, so I took a multimeter with me yesterday so I could test things.

 

Last night when the batteries died I started the engine with the isolater set to just the starter battery and it measured 13.6V, I then turned the isolator to the leisure batteries and it only read 13V with the engine running.

 

Surely the alternator should be pushing 14+ Volts with the engine running no matter how flat the batteries are???

 

I checked the belt tension and condition and its appears fine and the alternator pulley doesn't get hot so the belt isn't slipping.

[Tony Brooks]

Well we finally managed to get the boat out for our maiden voyager yesterday and returned to the marina this morning.

 

We had the engine running with the isolator set to both for around 4hrs yesterday, last night when we moored up I turned the isolator to the leisure batteries only. Whilst watching tv last night the leisure batteries started to get low and the tv went off. All we had turned on was a couple of small 10-12" fluorescent tube lights, the fridge and the TV and the batteries only lasted about 4.5hrs tops.

 

How long should they last without the engine running? I noticed last week whilst at the marina that the voltmeter on the boat doesn't go much above 12v with the engine running, so I took a multimeter with me yesterday so I could test things.

 

Last night when the batteries died I started the engine with the isolater set to just the starter battery and it measured 13.6V, I then turned the isolator to the leisure batteries and it only read 13V with the engine running.

 

Surely the alternator should be pushing 14+ Volts with the engine running no matter how flat the batteries are???

 

I checked the belt tension and condition and its appears fine and the alternator pulley doesn't get hot so the belt isn't slipping.

 

 

I would expect any post 1980 alternator to be charging at between 14 and 14.6 volts, about 14.2 probably the most common.

 

I suspect your battery switch was turned through OFF at some time during or prior to sale and the alternator was damaged.

 

A well discharged battery can pull the alternator output down to 13 volts (although normally I would expect a bit more) until the batteries start to charge. Then the voltage will gradually rise. The same will apply to a battery with shored cells but in that case you would probably have been talking about horrible smells and the battery boiling.

 

No one can answer the "how long should they last" question because as batteries age they loose capacity so a 110Ah battery that is a few years old may only be a 20 Ah one - or even less.

 

I think that you need to take the/a batteries home and charge each one for a couple of days or until the charger says it is charged. Then let it stand for a day and measure the voltage. Expect 12.7 to 12.8, if less either it was not fully charged or it is faulty. If the voltage is around that figure take a hydrometer reading. Expect 1.275 or more. If it is less that battery has sulphated and lost capacity.

 

Hopefully that will tell you if it is a battery problem or not. Then take the alternator off (noting/photographing the connections) with the master switch turned OFF. Take it to your local specialist (car & Truck ones will be fine) for testing.

 

If this were my boat I would also do away with that rotary switch and fit a good quality split charge relay (wired as described earlier) plus a pair of good quality master switches in the POSITIVE battery cables.