Generator Battery

Wavey

Wavey

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My boat has its own battery for starting the generator, separate from the domestic and engine batteries. I guess the generator (Fischer Panda) in common with many small units has no means of charging its own battery. Problem is this battery is not charged by either engine alternator, and its not charged by the boats mains powered charger either. It has it's own charger which is a small trickle charger type, and is therefore unable to re-charge the battery in a short space of time if it goes flat. This to me seems a daft arrangement but apparently it's how the boat was originally built.

I'm thinking of getting rid of the generator battery and instead using one of the engine batteries. This has the benefit of reducing the number of batteries on board by one, and it also means the battery for starting the generator should always be in a good state of charge either via the alternator or the main charging system.

So, my question is, is this the usual arrangement for boats of my size (42') or do you use the domestics for the generator? Or is there some good reason why it was built the way it was?

The main charger doesn't seem to have space capacity to add another battery bank, and the generator battery circuit has no meter fitted so no way currently (pun) to check its state of charge. Invariably the only way you know the generator battery needs a boost is when it won't start it.

Any thoughts?
 
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Only thing that occurs to me is if the engine batteries were flat you couldn't start the generator to charge the engine batteries.
 
On my twin-engined boat the OE arrangement is one dedicated battery as engine start for the stbd engine, and a pair of batteries as port engine start, domestic, and generator. There's a switchable bridge between port and starboard.

The logic is that if you completely consume the domestic bank, you can start the stbd engine, then bridge start the port or the generator, as required.
 
Keeping the separate battery for the generator really only works if you've got some means other than its own less than adequate charger to keep it topped up when you're away from shore power.

James' battery to battery solution is one I hadn't thought of and certainly worth further investigation.

Domestics are 24v served by four big Trojan 6v jobs so can't see any obvious way of using them to help. Have spoken to Brooms who advise my set-up was only used on the early 42cls. Later builds did away with the generator battery and instead shared one of the starter batteries. I have two really hefty 12v batteries, one for each engine so that should work ok. And I quite like the idea of reducing the number of batteries on board.

Would still like to hear what set-up is used on other boats of my size with a generator on board.
 
24v system,

2X12V 180Ah batteries for starting engines (both)
4X12V 180Ah batteries for service
1X12V 45Ah battery for gen
Though I'm pretty sure my Mase does have a proper circuit to charge it's own start battery

I'd definitely keep the gen battery and would install a bridge system (a la parallel switch you get for engine start from service batteries) to be able to fire up the gen when its own battery is flat.
My neighbor on his P45 always has a charged, sealed unconnected battery in the e/r waiting for the unfortunate moment that all his batteries are flat (which I do find extreme...)

cheers

V.
 
I'm very surprised that the gennie doesn't have a 12vdc charging coil output - almost all do, and I recently fitted a FP to my friends Sealine 410 and it definitely did.

If it doesn't have a 12v output, it will be consuming power from the battery all the time it's running, which is a bit of a worry - battery goes flat, gennie stops.

Are you sure it hasn't just not been connected up?

Otherwise, ditch the battery and start off the engine bank, assuming you have some sort of battery bank link switch in case of flat engine battery. Then whilst the gennie is running the engine bank (and hence gennie) is charging off the ships charger. Again, I'd surprised if a 42' Broom didn't have a link switch already..
 
Very interesting post. Many thanks Ross.

My FP is a 2001 vintage (4000 series IIRC) and the engineer who serviced it last year said it had no means of charging its own battery. Could be though he was looking for an alternator (which the gennie on my previous boat had) and not a charging coil output. As it happens FP took the unit back to base on Thursday to cure a nasty oil leak and do an overhaul as its clocked up 1200 hours. I'll ask FP about the charging coil and if it doesn't have one then whether its possible to retrofit.

I'm not aware of any battery bank link switch and there's no mention of it in the Broom owners handbook but as you say it is the sort of thing you would expect to be present on a Broom. I'll ask.

Appreciate your help.:encouragement:
 
I deal with a lot of boat builders regarding generators and most use a dedicated start battery for the generator. In most cases the generator would be 12v starting and the service batteries would be 24v, for me it's never a good idea to pull 12v from a single battery of a 24v system.

In this case I would purchase a small multi stage charger for the generator battery so that is charging on shore power and when the generator is running.

Anthony
 
Just for info FP have confirmed my unit has no means of charging its own battery. Their suggested solution is to remove the generator battery and use one of the engine batteries instead, as Brooms did on the later 42cl's.
 
Fair enough :)

That's exactly what I did after melting the 12v charging winding on my gennie. £1000 to rewind alternator, probably £50 to reconfigure wiring!

Mine is a Zeise, same engine as your FP.
 
ARE said:
In this case I would purchase a small multi stage charger for the generator battery so that is charging on shore power and when the generator is running.

Anthony
Click to expand...

I think this is the way to go or keep it even simpler, fit a battery charger that is powered when the generator runs. Every now and again plug it in when on shore power and charge the battery overnight.

Having a separate battery is essential, it gives you another option in the event of battery drain. With the genny running the boats 12 volt charging system is powered and you've cooking !

I'm amazed people sell generators that don't charge their starting battery.

Henry :)
 
Why not put a small car battery charger wired to the mains output (with correct fuse etc ) near the enclosure. Auto charging when the genny runs.

Edit. Just been beaten by henry. That will teach me not to have lots of tabs open.
 
I think it is pretty standard in boats of our type not to have a mains charger for the generator, as standard.
Like a lot of people on here, I suggest that you just fit a simple mains charger and leave it charging from shore power whenever your main battery charger is working.

There is a big "however" though
I would check very carefully that you don't introduce some kind of earth loop that would compromise your anode protection (galvanic) circuit.
I think it is unlikely but I run a cheap mains charger for my generator battery and before connecting it, I completely isolate the generator battery from the rest of the boat.
It is a permanent arrangement of isolators to each side of the generator battery that I fitted when we first bought the boat.
These isolators also ensure that the mains charger is not connected at the same time that the generator is running.
The result is that my generator is as charged as any other battery on the boat.

I have similar chargers for the dinghy battery (and more recently the Jetski battery) but these two don't need to be isolated from the boat's galvanic system.

I could have bought specific marine chargers but I find these are as reliable.
http://www.optimate.co.uk/accumate.htm
Chargers need to be automatic so that you can leave them connected
I have used CTEC chargers in the past but they haven't been as reliable.

I like the idea of the battery to battery charger but there really isn't a point - why not just keep the one you have got fully charged using the mains?

I do agree with you though
There is nothing worse that a fully working bit of kit that won't start - just because the battery is flat.
You have to do something.
At least you understand the problem - I wonder how many people out there don't even know that they have this problem.
I should think that close to 100% of boats that have generators factory fitted don't keep their batteries charged.
 
Thanks Hurricane. I got caught out a few times with a flat battery when I first bought the boat. Mainly because my previous boat was fitted with a G&M unit which could charge its own battery. I just assumed (incorrectly of course) that they all did.

I'm not a fan of leaving chargers on for days on end when I'm not on the boat. As good as modern chargers are said to be they do seem leave the batteries requiring top ups more regularly. I haven't come across one yet that doesn't do this.

The three things I don't understand are (and Brooms themselves don't seem to know)....

1. Why wasn't it wired up to enable the generator battery to be charged when under way just the same as all the other batteries on board
2. Why did they fit a separate charger for the generator when wouldn't it have been a better idea to install a bigger main charger for the boat that could charge 4 battery banks rather than 3
3. Assuming there was good reason to fit a separate charger, then why fit one with such a small output it literally can take hours to get enough juice in the battery to start the generator
 
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