Are separate service and starting batteries really necessary?

Are you happy with you triax ufo

  • Yes you should buy one

    Votes: 0 0.0%

  • No get the glomex

    Votes: 0 0.0%
  • Total voters
    0
Re: One battery .... no problem.

[ QUOTE ]
Bit of S&M never hurt anyone

[/ QUOTE ] So what would be the point? /forums/images/graemlins/grin.gif
 
Re: One battery .... no problem.

Shorting the two banks together, does not neccessarily drag the good bank down, just gives the starter a boost to get the engine started, just as you would, by jump starting a car, boat etc, with jump leads.
Remember this is emergency time, not an everyday occurance, if the engine start batteries are flat, and I have time, just start the genny and re-charge them.
By the way, it would take quite a bit of discharge to flatten my 440ah 24v domestic battery bank.
This is an acceptable method, approved by lloyds.
 
Shorting batts ....

Given the size you quote - no problem .... but also note that many boats go araound with far smaller batterys ... often a couple of 80 a/hrs etc.

The comparison with jumping cars is not on honest - as when jumping a car - no-one in their right mind has both engines stopped when doing it. Jump supply car has engine running at fast tickover to help the battery start the dead car ....

So therefore given average yottie battery banks - I still say shorting both is not a good idea ... IF you have humongous great 440 a/hr jobbies like you have - then I don't think it makes a rat's ar** whether you short both or just change to other to start .....
 
One battery is crazy for all the reasons others have said. IMHO the optimum setup is:
- 6v deep cycle golf cart batteries in series for house
- cranking battery for engine
- cranking battery for anchor winch (placed forward close to winch, gets rid of long cabling and the associated problems)
- cranking battery for generator if you have one
 
Aside from the obvious risks, the main problem is that the starting ability of a diesel is more dependant on cranking speed than any other factor. Most engines like the starting battery to be as fresh as a daisy - which it won't be after a night of domestic or navigational service.

The idea of fitting only one battery in a cruising production yacht is crazy. I would expect their insurers to have concerns about their product liability. I suppose it would be OK to supply the boat with only the one battery but with the box and terminals all ready to go for a domestic battery.

There might be exceptions; I only have one battery bank as I could get more Ah in my vented battery box that way. But, I do have a diesel generator with its own battery so could always start that to charge the main battery if needed, or jump across from the genset battery to the engine. I have never needed to do either - my engine is an excellent starter, we liveaboard and we are in a warm and reasonably dry climate. A single battery on a boat that is used as a weekend boat in UK coastal waters? No.

Fifty years ago it wouldn't have mattered so much as skippers used little or no electronic nav aids and every sailor could anchor in a harbour, or pick up a mooring under sail. But electronics was not available and harbours were not so crowded. Just for the hell of it, here is a little survey for sailors..skippers only, please.
 
Re: One battery .... no problem.

Agreed, I am configured in the same way.

Edit - I misread your post, no, I am not configured like you. I have one bank only plus a diesel generator with its own start battery.
 
Re: Shorting batts ....

What about the "power packs" folk use to start their engines? They dont have an engine!

I cant use the other bank, there is no way to use it, without using the solenoid, belt and braces, I cant flatten those, unless I keep my finger on the button.

Your engine running at fast tickover, to "Help" the battery is rubbish, fast tickover with an alternator, might help, if you leave it running like that for an hour or so, to put a charge in the other battery, but the average car alternator, putting out 25-30amps, Max, is not going to help the required 300amps for starting.

Even 80ah batteries are not going to come to much or any harm, in an emergency starting regime.

Sorry to disagree with you.
 
I started my 23 yo Bukh DV20 with the starting handle this summer, when on an own boat Dazed Kipper course- both to my & tutors amazement. Truth to tell, it was not too diificult and having done it, very reassuring re poss battery probs. I also have 1 domestic, 1 start battery set up, but very tempted by Red Flash start battery, leaving the 2 orig batteries as domestic bank. One day!
 
Re: Shorting batts ....

I think you'll find that with the engine running the "helper" car's battery voltage will be higher. Higher voltage, faster starter spin, more chance of starting.
 
Thanks for all your replies.
The yacht I was referring to was the new First 25.7 which is fitted with one 70amphour battery! Unfortunately the engine Beneteau fit is the new 2-cylinder Yanmar designated 2YM15 which does not have a hand-starting facility whereas the old 2GM engine did - so much for progress. I suppose things could have been worse, it could have been a Volvo.
I have a friend with a Sabb engine and like the Bukh it has a massive flywheel so he always starts it on the handle very easily - again so much for progress.
 
Re: Shorting batts ....

He's right about that...even a very short period of charge, at very modest rates, makes a useful difference terminal voltage hence cranking speed. It is not an 'energy' issue, i.e. you are not getting something for nothing, so the laws of Physics are not being broken.

As a matter of interest, I have often wondered whether given two marginal batteries, neither of which would start the engine due to marginal cranking speed, if you used a mains inverter from one to drive a charger to boost the other, you would get the engine started. I'm sure it's worth a try, in extremis. The problem is likely to be that inverters drop out when battery volts fall too low.
 
hand starting yes

I have started an MD 2B with a handle once - but it was a long time ago and I know I cannot do it now.
Your Powerbank has a small capacity high CCA battery.
I have fitted a small Red Flash battery also with low capacity and allegedly 1100 amp CCA. It will fit in a very small space c.100 x 200 x 200 mm. It's sealed and could be used flat. It also works very well. It is not used for any other purpose.
I also have one general purpose battery and another just for the fridge so running down the fridge battery has no effect on the rest of the boat - though the skipper gets grumpy when there's no cold beer.
 
Re: hand starting yes

I think I could get into most harbours, but I have enough trouble getting into my berth under power right now, doubt I'd have any fun without it, so I voted doubtfully. Think I'd cheat- pick up a mooring and scoot in on the dinghy to pick up a car battery!
 
Lemain - the poll is flawed ...

I knwo I can get into my harbour under sail and also pretty close to my berth ..... done it under real conditions when engine was seized.

BUT your poll doesn't allow for those who would inform CG and make harbour .... I would be able to make harbour .... but I would inform CG of the situation. You never know when things will go T's up !!
 
Re: hand starting yes

One note from someone who has never had a seperate starting battery, but who always switches the fridge off at night!! I find that cleaning and lubricating the bendix gear at start of season drastically improves starting! And if the battery is struggling, decompressing the engine almost always enables enough revs to start. I can't do it by hand though.
I will eventually fit a seperate starting battery though, when I have deciphered Advercs wiring diagram for the diode.
 
Oh dear ....

Manuals ..... manufacturers etc. all advise tro run jump cars engine while aiding another .... are you now saying that all the millions who do this are wrong ?

The Power pack situation is completely different and not comparable.

I still and am adamant that average boat with smaller a/hr batts than you have is risking having both dud batts in shorting together. I can see the logic of giving a short burst of both together ..... having the "punch" of two batts to try to start ... but NOT once one is flat from failing to start the engine ..... both while both are still in good condition and isolate them before both are flat and useless .......

Your batts are far way and above size of average boat ... so feel you are out of average boaties league on batt states ..... I have two average size batts and have on many occasion been over zealous on domestic ..... and occasionally forgot to change from start batt - depleting it to below start capability. Even with my wheezy lazy starting Perkins ... I would NEVER put both batts together ... unless it was a do or die attaempt ... and to be honest - that is not a situation that I even want to contemplate.

I disagree with you again .... but I think we normally do anyway !!
 
Re: hand starting yes - Decompressing ....

Can someone please tell me where the decomp lever is on my 4-107 ?? There was on the Lifeboat engines I was in cahrge of on ship !! But I always made sure I was NEVER the silly sod who had to swing the handle !!

Honest - there is no way I will ever start my Perk 4-107 by hand !!!!!! There is no provision .......
 
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