Generator start battery question

[Deleted User YDKXO]

Just spent last night at anchor and tried to start the generator this morning but it wont start and the generator control panel is showing a low battery message. The generator was running for several hours on and off yesterday and started perfectly every time

I'm trying to understand how the generator battery is charged. Is it likely that it is part of the battery charger circuit that charges the services and engine start batteries or will it only be charged from the alternator on the generator itself? If this happens again would there be any problem with hooking it up to a service battery with jump leads and jump starting the generator?

I have tried starting the engines to see whether the engine alternators charge the generator battery but they dont seem to

 

[Jegs]

I can't see why jumping from another battery would be a problem, provided that the voltage is the same, starting an engine from a 2000 amp battery bank shouldn't make any difference. Specifically, the diagram for my 30+ years old genny shows a feed from the alternator via a regulator which connects to the positive post.

ATB,

John G

 

[baylabayla3288]

Just spent last night at anchor and tried to start the generator this morning but it wont start and the generator control panel is showing a low battery message. The generator was running for several hours on and off yesterday and started perfectly every time

I'm trying to understand how the generator battery is charged. Is it likely that it is part of the battery charger circuit that charges the services and engine start batteries or will it only be charged from the alternator on the generator itself? If this happens again would there be any problem with hooking it up to a service battery with jump leads and jump starting the generator?

I have tried starting the engines to see whether the engine alternators charge the generator battery but they dont seem to

On my Ferretti the Kohler genset has its own alternator and this is the only charging option for it. The Mastervolt shore power charger inverter combo on my boat has two charging outputs, one 100 A for the services side an one 5 amp (only) for the starting side but using the parallel switch more charging power can be directed to the starting bank. Jumpstarting the genset should not be a problem but connect the negativee first. You might have a dying battery or a lose cable clamp. The genset's alternator could also be broken off course. What is the battery voltage? Does it click when trying to start or is it compleately dead?

 

[Hurricane]

Just spent last night at anchor and tried to start the generator this morning but it wont start and the generator control panel is showing a low battery message. The generator was running for several hours on and off yesterday and started perfectly every time

I'm trying to understand how the generator battery is charged. Is it likely that it is part of the battery charger circuit that charges the services and engine start batteries or will it only be charged from the alternator on the generator itself? If this happens again would there be any problem with hooking it up to a service battery with jump leads and jump starting the generator?

I have tried starting the engines to see whether the engine alternators charge the generator battery but they dont seem to

On my boats, the generator battery has always been separate.
i.e. not connected to the ships battery charger or the engines.
It seems to me that boat builders expect the generator to run more often that it does and that the generator's own alternator should keep its battery charged.

I have always installed a separate battery charger for the generator - even to the extent of isolating everything from the generator's battery whilst it is being charged (from shore supply).

So, in your case, it may be that your generator battery is suffering from never being charged (other than its own alternator).

It seems that you are away on holiday so maybe the quick solution is to replace the battery now and look into how it is wired later.

 

[Hurricane]

I can't see why jumping from another battery would be a problem, provided that the voltage is the same, starting an engine from a 2000 amp battery bank shouldn't make any difference. Specifically, the diagram for my 30+ years old genny shows a feed from the alternator via a regulator which connects to the positive post.

ATB,

John G

There is a potential problem.
Mike might be tempted to "jump start" the generator from his house or engine batteries.
The generator battery is likely to be a 12v circuit whereas everything else is likely to be 24v.
Obviously it is possible but the neg on the generator will probably be the neg for the rest of the boat.
The positive to jump from would have to come from the middle of the battery bank.
Just take care - thats what I say.

 

[MapisM]

Absolutely. That's the only thing to be careful about - and of course, detaching the jump leads as soon as the genset is started.

Ref. the connection logic, fwiw also in my old tub the 12V genset battery was only kept charged by the genset alternator, but several years ago I fitted a small dedicated 12V battery charger, which I turn on occasionally whenever I'm not using the genset for long periods.
And again fwiw, that's exactly the setup which I was glad to find on the DP - where it was standard, as I'm told.
In fact, while you would expect the "genset alternator only" setup on my old tub, considering the commercial boats heritage of the yard, I am a tad surprised to hear that Ferretti (and also Princess and Sealine, if I understand what Hurricane said?) skimp on a small 12V charger which costs peanuts, on boats which by their nature are prone to stay unused for long times... :nonchalance:

 

[jimmy_the_builder]

Mike, did you get it sorted? We're only a couple of hundred metres away from you if you need any help.

 

[Hurricane]

but several years ago I fitted a small dedicated 12V battery charger, which I turn on occasionally whenever I'm not using the genset for long periods.

I'm probably too cautious but when I fitted mine, I made sure that it didn't create any unwanted earth loops that could effect my galvanic protection.
Thats the reason that I isolate my generator battery when the extra battery charger is connected.
All done with battery isolators so that it is easy to do - the positive should already have an isolator so there should only be a need for an isolator on the neg side of the battery.

Probably a waste of time but I didn't know if it would effect the galvanic circuit (anodes etc) - completely isolating the battery should eliminate any risk.

 

[Deleted User YDKXO]

What is the battery voltage? Does it click when trying to start or is it compleately dead?

Thanks. The generator was clicking and now its stopped which suggests that the battery has died

 

[Deleted User YDKXO]

So, in your case, it may be that your generator battery is suffering from never being charged (other than its own alternator).

Possibly. The boat hasnt been used since last October and to be honest I always assumed (wrongly as it turns out) that the gennie battery was charged by the main battery charger but if it isnt then its not been charged all winter. However it did start yesterday which is a bit odd

Good point on 24V v 12V

 

[Deleted User YDKXO]

Mike, did you get it sorted? We're only a couple of hundred metres away from you if you need any help.

Hi Jimmy didnt notice you come in. No its not sorted but we're going back to PV now anyway but thanks for the offer. Jo has already sorted an engineer for tomorrow already

 

[MapisM]

I'm probably too cautious but when I fitted mine...

I see your point M, but if my experience is anything to go by, yep, that was probably too cautious.
Not sure yet about how the genset battery charger was factory wired in the DP, but in my old boat there wasn't even an isolator on the positive - just a 12V battery permanently connected to the genset, period.
When I installed a small and cheap 12V charger, I just connected its output to the battery. Again, just a straight and permanent connection, nothing else.
But so far, so good - never had any problems.
Admittedly, it's a basic installation - for instance, I must remember to turn off the charger before turning on the genset, though in principle there's no reason to turn the genset on while connected to shore power. And I never leave it permanently connected with the boat unattended: I just turn it on for a day or so, every few weeks, whenever the genset is not used regularly.
But it works (I believe the genset battery, which was replaced when I installed the charger, is by now 6 or 7 years old)...

 

[MapisM]

I always assumed (wrongly as it turns out) that the gennie battery was charged by the main battery charger

M, just in case you wish to check further, you should look if by chance there's a separate 12V charger somewhere, which might not be working for some reason.
I believe there's no such thing as a charger with separate lines AND different voltages (24V for domestic and engines, 12V for genset).

 

[BartW]

Mike, perhaps you had some nav gear or other 12V systems left on all night ?

Also in BA, the genny's DC system is 12V on a separate batt bank, (I thought that this was rather a exception but apparantly this is common on Ital boats ...)

we have a small 12V charger, and the 230V supply for this charger comes from invertor or shore power
actually we leave that alway's "on".

if you have the engineer around, it makes sense to work out the boat's block diagram of your DC systems,
so that in such a case, you can alway's save the day with jumper cables...

good luck with it.

 

[MapisM]

Also in BA, the genny's DC system is 12V on a separate batt bank, (I thought that this was rather a exception but apparantly this is common on Ital boats ...)

I would think that's actually the only logical choice, B.

I mean, also leaving aside separation/redundancy considerations, the two alternatives are:
1) a genset with a 24V starter motor and alternator, or
2) a step down converter
But 1 would be very unusual - I believe that most gensets, at least up to "normal" pleasure boat sizes, are 12V.
And 2 would require a helluva converter, to handle the power required by the starter motor...

Can you think of any other setup, by chance? Just curious...

 

[BartW]

I would think that's actually the only logical choice, B.

I mean, also leaving aside separation/redundancy considerations, the two alternatives are:
1) a genset with a 24V starter motor and alternator, or
2) a step down converter
But 1 would be very unusual - I believe that most gensets, at least up to "normal" pleasure boat sizes, are 12V.
And 2 would require a helluva converter, to handle the power required by the starter motor...

Can you think of any other setup, by chance? Just curious...

Long ago, I had a comment on here that a 24v genny alt and starter is much more common in a 70ft boat, but I don't really know

 

[MapisM]

Well, I suppose that mostly depends on the genset rather than the vessel size - though of course they are somewhat related.
Fwiw, I've seen up to 35kVa Onan gensets which were 12V, but happy to stand corrected is any of the small ship folks has a 24V gennie onboard...

 

[mjf]

Deleted User. This is infesting as I established over the winter that the genset was not putting the volts back that it took to start when oil cold. The genset is stand alone with seperate 12v battery no charger other than alternator
I noticed that after a two hour under load run the volts when stopped were 0.5v+ less than at start

After a week of summer running at anchorages it was defiantly not spinning in the spirited way it ought to after multiple warm oil starts.

I found a smart charger that shows voltage and that is now a permanent fixture so genset has its own 240v charger and this runs when the genset runs so both alternator and smart charger feed the battery. Bingo good voltage remIning after a genset run, and always a full battery when genset started.

You can see the charger working when genset started from cold, and voltage under12.4v and rising as genset run so 13.4v indicated at shutdown.

Also of course over non use periods the 240 shore power keeps the start engine, hotel, and genset bank(s) at full voltage

 

[henryf]

The first place I would look is the battery. If it's over 3 years old then I would almost change it as a matter of course. It won't be an expensive job. The fact it's gone from clicking to not clicking means it's self discharging. Batteries can fail just like that.

See if you have something fitted on the charging circuit which requires a minimum voltage at the battery before it will allow charge to pass through to the battery. This would prevent gassing on a failed battery.

We always have a small portable battery charger on board which is handy for topping up the generator battery when it hasn't been used for a while. Run it overnight then put it away. That does of course assume you are on shore powe

Henry

 

[Deleted User YDKXO]

M, just in case you wish to check further, you should look if by chance there's a separate 12V charger somewhere, which might not be working for some reason..

We do have 2 chargers on board but there is a switch which only allows one or other to be used at any one time and they both charge the main batteries so I dont believe that either one charges the generator battery.