charging boat batteries via a timer

[RIN]

Looks like I will have to try and get down to the boat in the next two weeks which is going to be difficult. I am still not up to speed with all the 12v bits and have spent the morning looking on the internet for a schematic of how the the batteries, starter motors, alternators and diodes (if I have any) are connected an a twin engined boat. If anyone knows of one please send the URL

 

[PaulGooch]

Looks like I will have to try and get down to the boat in the next two weeks which is going to be difficult. I am still not up to speed with all the 12v bits and have spent the morning looking on the internet for a schematic of how the the batteries, starter motors, alternators and diodes (if I have any) are connected an a twin engined boat. If anyone knows of one please send the URL

Not that hard really, but a few possible variations.

All battery negatives should be connected together, to both engines and to the domestic negative busbars/posts.

Engine battery positive to both starter motor positive terminals. (via isolator)

Domestic positives linked, then connected to the domestic circuits. (via isolator)

A third isolator can be fitted to parallel the two banks, for emergency starting, by running a cable from the positive on the engine battery and the positive of one domestic battery to a 3rd isolator switch.

That's all easy enough for you to check and correct yourself.

Charging can have a host of possibilities. Given your boat, the most likely possibility is a pair of split charge diodes (approx 3"x2"x1.5" lump with a finned heatsink). The charging cable from an alternator will go directly to the diode and a pair of output cables will go to the two battery banks. Repeat for the second engine.

You might have a single diode pack, with two alternator inputs and two battery bank outputs. It's also possible that someone may have fitted one of several other systems, or that they may have just bodged something up.

Short of getting someone to look at it for you, the best solution is to get down to the boat when you can and take all the negative cables off to prevent the batteries going flat. Whilst there, trace the positive battery cables and charging cables and write down where they all go. Sort out as above, or post back for further assistance.

 

[supersparky]

We have 2 x110AH leisure batteries and a starting battery on the boat. We live quite a long way from it and have installed a timer on the shore power input so the batteries retain charge in case we cannot visit the boat for an extended period.

The timer was set to switch on four times a week for 15 minutes each time

It was last used at the start of November, but we went down the boat yesterday to check for damage after the storms and to change the oil. Unfortunately the engines would not crank and we only had 6V on the gauge.

Leaving the batteries on charge for 4 hours just about turned the engine over and started the engines

So the question is how much charging should I set the timer to give? It is now set to give 2 hours four times a week

Anyone have a view if this will damage the batteries or still will not be enough? The main battery switches are left on and all domestic 12v breakers are switched off

In 2005 I crewed on a boat with a Newmar changer with 3 outputs. I cannot remember if it took any drain when left connected but I think it took a little. It was a 3 stage charger as described by Spi D and was designed to be left on continuously. If batteries are charged right up to 99% plus then they will normally stay up all winter if isolated unless they are nearing end of life. Do not leave them in parallel as if one goes down it will take the other with it. Any battery below 2.03v per cell (12.2v) may be in danger and needs a 24hr charge to get it up fully. They will deteriorate if not left 99% plus. Each type of battery has it's own characteristics, and voltages will change with age and temperature so it is difficult to generalise, but if the battery gets hot or you can smell acid spray then it is end of life for either the battery or the changer.
Changing the subject, I now think that AGM batteries are now cost effective because they last longer, but don't leave them in parallel with other types because the voltages may be slightly different. Good luck

 

[RIN]

Trip down to the boat organised for Thursday. Will be out of the country then until middle of March so have to make this count. I'm going to test for draw on the batteries, state of batteries, charging voltages etc.etc.

I still haven't found a diagram on the internet of how the battery/engine/charging system should be so last night in the pub with a mate and armed with an empty fag packet we drew this. I have never found a diode block on the boat so assume that this diagram represents what I should have. (I know it isn't because somehow the batteries are permanently bridged but will have to sort that out as part of the investigation. I will have to install the bridging switch)

Note on the KAD32 the starter motor and the alternator share the +ve cable as part of the engine wiring.

Any comments? This is what I hope to leave behind me when I come home

Many thanks
Richard

 

[Dave_Seager]

The way you show things on your sketch one engine charges the starter battery and the other charges the domestic battery bank.

I would surprised if this was the way Princess wired it originally as have a Princess 32, about 10 years older than your boat, that is wired so that each engine charges both sets of batteries. I am sure that this is original as it is shown on the circuit diagrams from Princess.

On mine, at that back of each alternator there is a finned metal casting which I assume contains the splitter diodes. Then there are two separate output terminals to charge the two sets of batteries.

 

[PaulGooch]

Richard, what you have drawn will work, but as Dave says, doubtful that's how it was built. It's also not the best way of doing it. Given your time constraints, it would do for now, with an update when you return to the Country. If you don't get it all done on Thursday, just leave the negative leads off of the batteries to prevent further discharge (take them off before you do anything, to prevent shorts etc).

The starter side of things is correct in your sketch, but the charging diagram from the alternators isn't how you want it. One charges the engine battery, the other charges the domestic bank, in your sketch. Starting the engines will use little power, so after a very short time the engine battery will be fully charged and that alternator will be doing very little, the domestic alternator will be working hard, on it's own, to charge the domestic bank. More importantly, a failure of an alternator would mean no charging at all to one bank. If you wire the charging as per the diagram i've drawn below, you overcome both of these issues.

If you are correct that the alternator output cable goes to the +ve terminal on the starter motor, you would have to disconnect that at the alternator and completely remove it, or insulate it and run a new cable to the split charge diode. It is also possible to get a diode pack that has two alternator inputs and two outputs, though it might give better backup protection to use two separate ones, as in my diagram.

I've drawn the diagram with the BlueSea switch i mentioned earlier, but you can substitute that for three separate ones if you wish. I've also left out the mains charger, that's wired as per your sketch.

 

[RIN]

If you are correct that the alternator output cable goes to the +ve terminal on the starter motor, you would have to disconnect that at the alternator and completely remove it, or insulate it and run a new cable to the split charge diode.

Thanks for that, it might come to disconnection (but then there is the worry of the bilge pumps not working)
I have just checked in the volvo manual and if it is readable, you can see a 10mm cable linking the starter motor and the alternator (called a generator by volvo). To be honest this has been the most confusing point because even with diode splitters or similar, I do not see how you can isolate one bank of batteries from the other if the alternator and starter motor are linked.

 

[Peanuts]

Hi Richard

Have only just come in on this post.

I was surprised by some of the posts saying that the charger you have is "antique", it is the same as mine on a 2001 S28 and I have worked on later models that still have this model. It must be capable of doing it's job as I am still on the original batteries, now 12 years old!

Regarding the wiring I will have a look when on the boat this weekend for the wiring diagram from Sealine to see if it can help. My electrics book is also there so I'll have a look in that as well.

I don't recall any diode packs when hanging upside down in your engine bay but I wasn't looking for them at the time.

I hope this maybe of some help.

Steve

 

[PaulGooch]

Thanks for that, it might come to disconnection (but then there is the worry of the bilge pumps not working)
I have just checked in the volvo manual and if it is readable, you can see a 10mm cable linking the starter motor and the alternator (called a generator by volvo). To be honest this has been the most confusing point because even with diode splitters or similar, I do not see how you can isolate one bank of batteries from the other if the alternator and starter motor are linked.

Although the diagram from Volvo shows it wired that way, it's very unusual for a boat with twin engines or anything with twin banks to be left like it. It would usually only be that way in a single engine/single bank installation. In all probability, that 10mm cable is either disconnected and insulated, or completely removed. If it isn't, you need to do so to make the best job of your charging system.

You can isolate the banks, as you have done in your sketch. It's just that it isn't the best or common way of doing it.

If you're worried about bilge pumps, just take the negative cable off of the starter battery, so at least that one doesn't discharge.

 

[halcyon]

The way you show things on your sketch one engine charges the starter battery and the other charges the domestic battery bank.

I would surprised if this was the way Princess wired it originally as have a Princess 32, about 10 years older than your boat, that is wired so that each engine charges both sets of batteries. I am sure that this is original as it is shown on the circuit diagrams from Princess.
.

That was the way most boats were wire in the 1990's, cirtainly Princess. Because we altered all the Sealine equipment from three battery banks to two to match Princess.

I remember Volvo bringing in the alternator with split diodes fitted, there was also a big problem in service with system.

Why fit diodes anyway, it only creates problems in volt drop, a split charge fault can mean no charge to engine battery.


Brian

 

[PaulGooch]

Why fit diodes anyway, it only creates problems in volt drop, a split charge fault can mean no charge to engine battery.


Brian

That's incorrect Brian. If wired according to my diagram (which is how the vast majority of boats with diodes will be wired) and one diode pack fails, the remaining alternator/diode will continue to charge both banks.

With a VSR system, a failed VSR will prevent one bank from being charged.

The voltage drop is a red herring. There are zillions of boats out there fitted with diodes and have been so for decades, all happily charging the batteries without issue. Yes, there is a voltage drop. But, if one does the calculations, taking away the voltage drop from a decent diode away from the charging output of a reasonably modern alternator, what's left is more than enough to fully charge a battery.

I accept that there are now lots of boats out there with VSR's fitted. But, they have their own possible issues. There are also plenty of other systems, better than VSR's or diodes, but in my opinion, for a cheap solution on the average mobo, the diode is still king.

 

[RIN]

Managed to get down to the boat on Thursday and for those still interested, here are the findings.

Original problem: timer was on 15mins 4 times a week, but batteries were flat. Also starter/leisure batteries seem permanently connected.

The first test was to check the battery voltage 12.18v for both

second test to see if there was a draw on the batteries form something on the boat. Disconnected both batteries then measured current from starter then leisure batteries. Initially a shocking 0.89A. but further investigation revealed that an auto bilge pump cut in for 20 seconds when the battery was connected.

This settled down to a constant 0.17A this equates to a draw of 28.5AH per week, far too high.

On investigation, it transpired that the helm indicator and the fuel gauge were both permanently on. These we re-routed to a busbar activated when the ignition on the port engine is switched on.

New test of draw revealed 0.02 amps - a draw of 3.4AH per week. We could not find anything else so assumed that this was current flowing back through the charger but in any case this looks a very small figure.

Second problem, how are the alternators and battery charger connected to the batteries? This all hinged around the connections in the engine and auxiliary battery switches in the engine compartment control box (mounted on the bulkhead). No splitting diodes, no splitting relays, very simple, but not possible to protect one battery if the other suffers a collapse. From the diagram below you can see that both alternators were only connected to the auxiliary switch. This looks a little bizarre, but when you consider the alternator and starter motors are joined in the volvo wiring then it is obvious that if both switches are on, all batteries are going to power the starter motor, conversely, all batteries will power the boats systems

That's as much I can do for now, may look to provide some sort of upgrade to the 12v system in April.

The shore power is now on a timer giving two hours, four times a week.

OK peanuts, I've shown you mine, now show me yours

Richard

 

[PaulGooch]

That wiring is very wrong, very wrong. I find it very hard to believe Princess would have built it this way. Looking at your diagram, a flat engine battery will mean the starter motors will draw their full load from the domestic bank, via the charging cables, you could very easily start a fire here.

A single battery failure will take out all the batteries.

Any one bank going flat will drain the other and leave you without a way to start the engine.

A flat engine battery will also mean the winch will draw its power from the domestic bank, via the charging wiring, another risk of fire or permanent wiring damage if you're lucky.

This system seriously needs correcting. I'd fit the diode as per my diagram. Very, very easy to do. Disconnect one alternator output cable and remove it from the starter too, if not possible, insulate it. Fit a new cable from the alternator to a diode, then from each output of the diode to each battery bank. Repeat for the other alternator.

Fit a 3rd isolator switch to link the two battery banks as an emergency way of starting the engines from the domestic bank.

Fitting a better charger and scrapping the timer would be a good move. How about this one : http://www.ybw.com/forums/showthread.php?t=301120

If you don't want to spend any money, a much safer way of wiring things would be to have the engine battery start one engine and that engine charge the engine battery. The other engine would be started by the domestic bank and would also just charge that bank. The 3rd switch for emergency starting would still be a sound idea, especially since you already have the switch.