Uprating 12V service system

[Magic_Sailor]

OK – the Jeannau website is absolutely no use, so here is a question. Posted on SB and PBO – sorry for any inconvenience.

Boat: Jeanneau Fantasia
Engine: Yan 1GM10

I plan to uprate the 12V system by the addition of an extra 75Ah service battery. Currently the system is as follows

Alternator – charge splitter – 1 engine battery (75Ah) – 1 service battery (75Ah).

I do not have a circuit diagram and/or specifications for the alternator or charge splitter. So the question is, am I going to be safe, merely connecting an extra 75Ah battery in parallel with the current service battery? Specific points

1. Can the charge splitter cope.
2. Ought I to lay in extra cable from the charge splitter (companionway) all the way to the service battery (forepeak). Current cable is 4mm squared cross section. I see from the RS catalogue that its rating is 32A, so I suspect its OK.

Thanks in advance

Magic

 

[ccscott49]

I reckon you need to check. How old is the other battery? They really should be changed in banks, that is to say, you should renew the old service battery at the same time as adding the new. The old battery will drag down the new one. You should check with the manufacturer of the charge splitter, (is it an alternator controller or just a splitter) also what is the ouput of your alternator, these are things you need to know, it's not as simple as you would first expect. The cabling is just one aspect. Uprating any system, I would fit an alternator controller as a first step. Then think about battery banks etc. Alsdo one final thing, why would you want a battery in the fore peak?

 

[Aeolus_IV]

When I installed a split charger I also installed an external alternator regulator. This manages charging of the batteries more effectively than the alternator on its own, and taks into account 0.7v drop that the diode splitter induces (unless you spend serious money on the splitter). Key thing to know is rated output of alternator, as this dictates the minimum cross-section size of your charging leads, and the rated capacity of splitter (ensure splitter is over rated as these do not like running hot or being installed in a warm location - ie by the engine).

ccscott49 is right about mixing batteries of different ages, the best advice is don't, you'll simply end up with two tired batteries, and utimatley end up replacing both eventually.

As a thought I believe I have seen a three way splitter, which might suite your purposes, if the third battery is for auxilary equipment like a windlass rather than simply expanding the available capacity of the service bank?

Another 2p worth.

Regards, Jeff.

 

[Magic_Sailor]

I was vainly hoping for a simple answer!

Thanks for replying - I thought I'd need all this type of info you mention but your general comments are helpful anyway.

Why a battery in the forepeak? - I dunno, that's where Jeanneau put it. Seems a bit silly considering voltage drops. Maybe it was a trade off with storage space further aft being more useable for clothes, food etc.

I'm not concerned about the other battery - I renewed it last year - I've checked, its still in good nick.

I think its a simple charge splitter - looks a bit like an old HT coil on the outside. I'll try to have a read this weekend but I suspect any markings are long gone.

Seems to me that if the charge splitter can provide the current and the cabling won't have a large voltage drop - I shouldn't have a problem.

Magic

 

[ccscott49]

The charge splitter doesn't provide the current, the alternator does, if it's not up to the job, two things could happen, it could take a long time to charge completely your batteries, if ever and much worse, the alternator could be forced to put out it's maximum rating for a long time and burn out. you pays yer money and takes yer choice. I wouldn't add a battery to a bank a year old, but thats just me.

 

[Magic_Sailor]

I appreciate that the alternator supplies the current - I'm currently (oops) assuming it will cope. What I meant was, the splitter diode must be capable as well.

I'm going to look into that alternator controller though.

Cheers

Magic

 

[Trevethan]

I wondered that too. Seems expensive in terms of cable to from charger/alternator etc, and if an invertor is fitted would need pretty hefty cable. plus the danger you get when the batteries are at different charge states and you join them up and they equalize.. Can see lots of very cable in those circumastances.. or blown fuses.

I don't know about his boat, but my forepeak is the wettest part of the boat, must make some cork plus fthat fit around the anchor chains and close of the chainpipes. Would not keep anything electrical in there.

Besides which, I figure I have enough weight in the bows already and wouldn't want to add any more there, and in a comparative light boat like a Jeaneau, sure not a great idea?


Nick

She had a deep, throaty, genuine laugh, like the sound a dog makes just before it throws up

 

[Magic_Sailor]

I might have used the wrong term. By forepeak I mean up the pointy end ender the V berth. Perfectly dry, but withing 5 feet of bow I 'd say. You might have a good point over weight.

Magic

 

[ccscott49]

You are talking three batteries of 75 amp/hr, thats a total of 225 a/h, you need at least 22.5 (10%) amps from your alternator to fully charge them from flattish in ten hours, plus a bit more for internal resistance etc, lets say 30,so thinking about it, to charge them up pretty fast, you need twice that, we are now up to 60 amps, So I would have a good look at the alternator. I would definitely fit the controller, I don't know why they are not standard fitment these days.

 

[ccscott49]

If it was put there as standard, I think it may well be balance balast, so you don't really want to put another heavy lump up there, without putting an equally heavy lump at the other end. IMHO

 

[Aeolus_IV]

I'd always assumed that this was the prefered location for a battery used to power a windlass. This gives shortest lead lengths to a windlass motor, important when a 1200W motor takes 100Amps. Other than that I could see no other reason, weight ideally needs to be centralised amidships forward/aft where possible.

Jeff.