Battery issues.

[Balbas]

We're just back from a fantastic family cruise in our new (to us, but actually 45 yr old) boat, during which I managed to completely drain the (single) domestic battery. We've finished our cruise and I'm trying to breathe life back into it with a smart charger - but that's by the by.

When starting, obviously I was switching to engine battery to start - to me it then makes sense to switch to 'both' in order to charge both batteries - is this correct?

When charging - noting that the (single) domestic battery was completely flat - the voltage at the terminals was never rising to the dizzy heights of 13v, staying more in a 12.5-12.7v range (admittedly I only ran the engine for 30 minutes or so at anchor, as the noise inside was quite annoying) - am I likely to have a goosed alternator, or is this a function of the battery being completely and utterly wiped out? How do I test the alternator in isolation?

As an aside, the rev counter (which I believe is run off the back of the alternator) is intermittent at best and I notice on this cruise that the hour meter has stopped ticking - I assume that's also likely driven by a signal from the back of the alternator? Its a Vetus 4.14 if that makes a difference.

Finally, I will be installing a larger domestic bank - I've space already for 2 batteries and may add a further 2. Hopefully this will reduce the likelihood of completely banjaxing the domestic batteries - and I'm also considering adding a solar panel - a 50W one would fit on the cover for the sliding hatch - how effective are these in UK weather? I would fit a wind turbine, but we have a ketch, so there's not much space.

 

[Ross f]

Hi
You are correct with the battery switch - when the engine is running have it on "both" to charge both batteries - when the engine is not running have it on the house battery only.
The charging voltage from your alternator needs to be 14.2 to 14.5V to effectively charge your batteries. If you are getting less it may be that at engine tick over the alternator is not turning fast enough and is not able to push out enough volts - put the engine in neutral and raise the revs a bit and measure the voltage at the battery terminals with a decent digital volt meter/multimeter set to DC volts. Do not run the alternator without the batteries connected to it or you will likely blow the alternator diodes.
The rev counter will (should) be fed from your engine ignition circuit - ie as soon as you turn the start key it should energise.
Solar and wind? Am sure you will get plenty of advice soon.

 

[oldharry]

Diesels don't have an ignition circuit so the rev counter usually runs off the alternator. Half an hour ticking over won't do much for a heavily discharged battery unless you have a charge controller and high output alt. Even then it takes several hours to recharge it. You can't put power back in all that quickly. It's the big problem with electric cars. 5minutes to refill a petrol tank. 5 hours to recharge a battery.

 

[MoodySabre]

I never put mine on Both. If you don't get them both right up then the start battery will get pulled down so that the charge in both is the same.

 

[Ross f]

Apologies I said rev counter when I was thinking about the engine hour meter and starter circuit not ignition.

 

[matthewriches]

Where in the lovely world are you?

 

[sarabande]

A quick check on the alternator belt tension might be a first step to eliminate slippage as a cause. Is there belt dust on the pulleys ?

It is not worth putting in additional batteries until you have found the reason for the low voltage. Flattening multiple dom batteries is not a Good Idea

When the dom battery is charged (green light) with the smart charger , what voltage across the terminals do yu have ? Does that voltage stay pretty constant (after the initial 1 hour drop) , or does it fall steadily ?

Do you have any systems attached directly to the battery ? e.g. gas detector, burglar alarm, bilge pump, radio ?


Grab yourself a tube of Contralube or similar (electrical connector jelly) and go through the connections to the hour meter, rev counter, etc. Make sure they are clean and strong, and add a tiny tiny blob of jelly to help ensure th e connectivity is reliable.

As for a 50W solar panel, it depends on your usage pattern and final battery bank size. If weekends and holidays only, a 50W stands a very good chance of keeping a couple of batteries topped up, especially if you run it through an MPPT controller like the baby Victron 75. ( I have a small 20W that is connected dreckly to 3 batteries, and keeps them smiling, though I also have a Merlin smart charger from the alternator).

https://www.ebay.co.uk/itm/VICTRON-...hash=item2f05338b23:m:mWFYKS2XGrdu_DMgT-0uxJQ

I think that wind turbines have had their day, with solar panels of increasing efficiency and size (more cost effective, also much less noise and worry)

 

[PaulRainbow]

Hi
You are correct with the battery switch - when the engine is running have it on "both" to charge both batteries - when the engine is not running have it on the house battery only.

You should not have the switch set to both, except for emergency starting. When the switch is set to both all batteries are in parallel, if one fails it can discharge the good battery.

The 1-2-B switch is a dinosaur, separate switches and a split charge system would be a huge improvement. At the very least, if keeping the 1-2-B switch, fit a split charge system, then you don't have to keep messing around with the switch to get all of the batteries charged up.

 

[PaulRainbow]

Where in the lovely world are you?

What relevance is his location ?

 

[matthewriches]

He asked about a solar panel and wind generator. And his profile doesn't mention where he is.

What relevance is his location ?

 

[Richard10002]

If a battery is fairly depleted, the voltage will start low, the Amps drawn high, and this is called the bulk stage of charging. Gradually, the voltage will rise to the regulated level of the alternator, (often 14.4V or so these days). When it reaches this level, it will stay there, and the Amps drawn will begin to fall, and this is called the absorption stage of charging. Eventually, the Amps should fall to 1% or 2% of Battery capacity, at which point a Battery bank can be considered full.

So it is not necessarily a problem that the alternator only charges at 12.5v to start with, as long as the amps are fairly high at the same time... it’s actually quite normal.

The whole process will take several hours, and 30 minutes will not have had much effect in terms of charging a depleted battery.

 

[PaulRainbow]

He asked about a solar panel and wind generator. And his profile doesn't mention where he is.

He said "I'm also considering adding a solar panel - a 50W one would fit on the cover for the sliding hatch - how effective are these in UK weather?"

 

[RichardS]

What relevance is his location ?

Edit: Overtaken by events.

Richard

 

[matthewriches]

By Joe, it does say UK. Funny how it is possible to skim read something and miss it on a phone. Although I tend to look next to someones profile or at someones profile for the location.

And, whatsmore, if the OP is local to Southwold or the river Orwell, pop in and we can lend you a battery tester and ammeter for a few minutes.

 

[PaulRainbow]

When starting, obviously I was switching to engine battery to start - to me it then makes sense to switch to 'both' in order to charge both batteries - is this correct?

This is not correct. A failed battery can discharge the good battery. Both is only for emergency starting.

When charging - noting that the (single) domestic battery was completely flat - the voltage at the terminals was never rising to the dizzy heights of 13v, staying more in a 12.5-12.7v range (admittedly I only ran the engine for 30 minutes or so at anchor, as the noise inside was quite annoying) - am I likely to have a goosed alternator, or is this a function of the battery being completely and utterly wiped out? How do I test the alternator in isolation?

You could try charging the engine battery on its own and monitor the volts and amps from the alternator. If you suspect the alternator isn't doing its job, take it off and get an auto electrician to check it.

As an aside, the rev counter (which I believe is run off the back of the alternator) is intermittent at best and I notice on this cruise that the hour meter has stopped ticking - I assume that's also likely driven by a signal from the back of the alternator? Its a Vetus 4.14 if that makes a difference.

The rev counter will take its signal from the W terminal of the alternator. Check the connections.

Finally, I will be installing a larger domestic bank - I've space already for 2 batteries and may add a further 2. Hopefully this will reduce the likelihood of completely banjaxing the domestic batteries

More batteries is a good idea, but you need to make sure you have the ability to keep them charged up. I'd also look into fitting separate switches, one for each bank and one for emergency starting, plus adding a split charge system.

and I'm also considering adding a solar panel - a 50W one would fit on the cover for the sliding hatch - how effective are these in UK weather? I would fit a wind turbine, but we have a ketch, so there's not much space.

Solar works perfectly well in the UK. I have 260w that will run the whole boat through the Summer months. Fitting a 50w panel would be a good idea and should ensure that you arrive at the boat to fully charged batteries (depending on usage pattern). It will also make a useful contribution while you are sailing.

 

[superheat6k]

From your comments about the rev counter flickering it sounds like the output from the alternator is less than sound, so as Sarabande suggests possibly slipping batteries, but possibly a poor condition voltage regulator or brushes within the alternator. The rev counter signal is actually the three phase AC output pulse inside the alternator before the power flows to the diodes, so if this is flickering then the alternator is repeatedly de-exciting / re-exciting.

I know some on here do not like Off - 1 - Both -2 - Off switches, but they are simple and work well if properly used, and do not have the issue of voltage drop for split charge diodes, nor the complexity of charge control relays, but that is not the issue here.

Several years ago when I moored without electricity the small solar panel the boat had kept the batteries well trimmed, so after a few days of the boat being moored all would be fully charged after a weekend of use.

I would have the alternator checked, and install a charge controller such as Sarabande mentioned or a Sterling unit.

If you do increase the size of your domestic bank make sure you have a means of keeping it charged, and a heavily loaded alternator on a small engine can take more than its fair share of the total available power.

 

[Stemar]

It sounds as though your domestic circuits are connected to the domestic side of your 1-2-both switch. If that's the case, the simplest upgrade to your charging system would be a voltage sensitive relay to connect the 1 & 2 terminals. Even cheaper would be a car headlamp relay doing the same job, but activated from the charge warning light connection on the alternator. I've had this arrangement for the last 15 years, but would use a VSR if I had to change it, as VSR prices have dropped considerably over that period.

As for Solar power, if you're fitting the panel(s) on the hatch garage, it's likely that some of the panel will be in shadow from the boom much of the time. In that case, consider a pair of smaller panels, as even a small shadow can bring down the output of the whole panel considerably. With a pair, it's likely that one will be in full sun, even if the other is shaded, so at least you'll get full output from one panel.

Our pair of 20w panels ensures that our batteries are always fully charged, keeping up with our use at anchor in the summer, provided we don't use the cold box and putting back what we used in a weekend working on the boat by the following weekend in winter (Snapdragon 24, with modest requirements)

You can get controllers for twin batteries. Ours is set to put the full output into the engine battery first, on the basis that a flat domestic battery merely means an early night, but a flat engine battery could be dangerous. Once the starter battery is full, it turns its attention to the domestic one.

 

[PaulRainbow]

I know some on here do not like Off - 1 - Both -2 - Off switches, but they are simple and work well if properly used, and do not have the issue of voltage drop for split charge diodes, nor the complexity of charge control relays, but that is not the issue here.

I stopped fitting diodes years ago, there are much split charge systems these days. A VSR could hardly be describes as complicated, neither could a FET based splitter.

I would have the alternator checked, and install a charge controller such as Sarabande mentioned or a Sterling unit.

I'd also have it checked, but if its a modern alternator that will charge at sufficient volts i don't see the need for additional charge controlling. You won't add a simple split charge device, but advocate charge controlling ?

 

[coopec]

Right now I am setting up my battery bank and starting system batteries. I've just bought a Dual Battery Controller switch. Is it possible to switch from battery 1 to battery 2 and then Both in series. Wouldn't that be handy as a last resort?

Clive

 

[superheat6k]

I stopped fitting diodes years ago, there are much split charge systems these days. A VSR could hardly be describes as complicated, neither could a FET based splitter.

I'd also have it checked, but if its a modern alternator that will charge at sufficient volts i don't see the need for additional charge controlling. You won't add a simple split charge device, but advocate charge controlling ?

Without a charge controller the alternator will only provide output to the terminal voltage of the battery, so its charge will diminish as the terminal voltage increases. A charge controller effectively converts the alternator to a multi stage battery charger.

I must admit it is a while since I had to think too closely about charge control, having enjoyed twin engine / alternator set ups the past 8 years. I never had a problem with the 1-both-2-off switches, but I can understand why others do. Perhaps I need to read up more on VSRs and FET splitters before giving my opinion, eh.

The principle issue here though is the alternator output I feel.