Battery Size?

[coromar]

Hi All,

What size battery do I need to start a 5.7lt, 6 cyl, turbo diesel.

At the momement I have a 90AH, 480CCA which does not always turn the engine over fast enough. I have cleaned and tightened all the contacts, but it is still slow.

Best wishes,

Paul

 

[Cliveshep]

I used to run coaches, and these used a bank of 4 big 6v units. You don't say what your voltage is, 12v would struggle and I'm assuming 24v? Try a pair of 12v 120 AH batts. These will suit whether coupled 12v or 24v I'm guessing. Main thing is to have enough power for starting, consistant with charging output, as you can't kick start the lump at sea!

Edit: googling the 480CCA battery it seems to be used for Mini Coopers? Def far too small then?

 

[coromar]

Battery size?

Hi.

My system is 12v

Paul

 

[VicS]

I agree thats is way too small.

likewise would suggest a pair of 110Ah batteries in parallel.

However the CCA figure is more important that Ah capacity. What is the engine and what battery is suggested by the manufacturers.

If space is an issue the alternative is to look at some of the specialised starter batteries that can deliver high starting currents from relatively small batteries. They'll be more expensive but peanuts compared with the running costs of an engine that size.

 

[coromar]

Hi Vic,

Engines are Hino W06-DTI. The handbook and the workshop manual do not state the battery requiments.

Space is there, but as I have two engines and a diesel genny, smaller batterys would be better.

Paul

 

[tobble]

any idea what the starter motor is rated at? the CCA of the battery should be a comfortable margin more than the rated current of the motor.

In terms of capacity, 110 Ah is probably OK but a bit more won't do any harm.

 

[Refueler]

Hi All,

What size battery do I need to start a 5.7lt, 6 cyl, turbo diesel.

At the momement I have a 90AH, 480CCA which does not always turn the engine over fast enough. I have cleaned and tightened all the contacts, but it is still slow.

Best wishes,

Paul

6 ltr Mercedes Diesel Truck had as standard 2 x 100 A/hr heavy duty jobs with a lot higher CCA than you quote. 760 CCA And it turned over lovely but was 24V. BUT even so - the capacity and CCA is not greater because of being 24V.

I suggest that your A/Hr cap is ok - but your CCA is way too low. Even my Inspectors cars have CCA batterys higher than that and they are only standard hatchback / estate cars ...
Maybe use existing low CCA as extra domestic where CCA is not important.

 

[VicS]

Its a pity the manuals do not give any indication of the required battery size. Its the engine manufacturer who should provide this information! Look at any of the Volvo Penta manuals and you find a recommended battery size.

Taking Refuelers contribution as a useful guide

He says 760CCA for a 24 volt system. To produce the same power at 12 volts will require twice the current so around 1500 CCA may well be the figure to aim for. I'd think quite adequate, maybe more than enough as you presumably wont be starting in arctic conditions as Refueler's trucks are required to do.

If space is an issue then look at Red Flash Starter batteries , there may be alternatives and there may be better alternatives, but taking those as examples the range is 420, 850, 925, 1150, 1200, 1400, and 1700 CCA at prices from £85 to £255. The capacities in Ah, and hence the physical size, are very small ( only 13Ah to 70Ah) but it is CCA that counts for a dedicated engine start battery.

 

[Refueler]

Its a pity the manuals do not give any indication of the required battery size. Its the engine manufacturer who should provide this information! Look at any of the Volvo Penta manuals and you find a recommended battery size.

Taking Refuelers contribution as a useful guide

He says 760CCA for a 24 volt system. To produce the same power at 12 volts will require twice the current so around 1500 CCA may well be the figure to aim for. I'd think quite adequate, maybe more than enough as you presumably wont be starting in arctic conditions as Refueler's trucks are required to do.

If space is an issue then look at Red Flash Starter batteries , there may be alternatives and there may be better alternatives, but taking those as examples the range is 420, 850, 925, 1150, 1200, 1400, and 1700 CCA at prices from £85 to £255. The capacities in Ah, and hence the physical size, are very small ( only 13Ah to 70Ah) but it is CCA that counts for a dedicated engine start battery.

My Engineer guy who looks after this sort of stuff - says that it is not strictly correct doubling the CCA as you've done. He reckons a standard 760~ at 12V is suitable. He was surprised that such a power plant is not 24V, as I was.

So taking his advise and he does it as his job ... just get a decent CCA value battery of 760 about or more if you have the pennies !!

 

[VicS]

My Engineer guy who looks after this sort of stuff - says that it is not strictly correct doubling the CCA as you've done. He reckons a standard 760~ at 12V is suitable

I wouldnt argue about the doubling being not stricly correct but 760 amps at 12volts is only half the grunt of 760 amps at 24 volts.
As you say though surprising that an engine that size only has a 12volt system. Cliveshep was obviously expecting 24 volts as well.

My original suggestion of two 110Ah batteries in parallel was based on what Volvo Penta say for a similar sized engine but you have to think in terms of CCA for the likes of Red Flash batteries.

 

[bedouin]

I wouldnt argue about the doubling being not stricly correct but 760 amps at 12volts is only half the grunt of 760 amps at 24 volts.
As you say though surprising that an engine that size only has a 12volt system. Cliveshep was obviously expecting 24 volts as well.

That only really applies if you are talking about resistive loads - and a starter motor is anything but that. If you think about it 760 CCA at 12V would be about 9kW - whereas the starter motor is unlikely to be rated at anywhere near that (perhaps 1.5kW at most?).

 

[earlybird]

[QUOTE. If you think about it 760 CCA at 12V would be about 9kW - whereas the starter motor is unlikely to be rated at anywhere near that (perhaps 1.5kW at most?).[/QUOTE]
That calculation doesn't really apply. A starter motor is a series wound motor with very heavy windings. At initial start up, ie low rpm, they can take a massive current, well into the hundreds of amps, esp for a cold engine. The battery has to be able to supply that surge and still maintain a reasonable voltage. As the motor speeds up, the current will drop.

 

[coromar]

Hi all,

Thank you for all the replies so far.

My starter motor is rated at 2.5 KW so I think I will look at batterys of 760 CCA. The Red Flash seem a possibility. I will visit Barden Batteries at the boat show.

Best wishes,

Paul

 

[VicS]

I am quite convinced that 760CCA is not enough.

My car, 2.1 litre 4 cyl petrol engine, starter rated at 0.81 kW, has a 540 CCA 70Ah battery.

On that basis you'd expect to need something in the order of 1500 CCA whether you look at the size of the engine or the power of the starter motor.

The fact that Volvo are saying 2x 12 volt 110Ah batteries for a 5.5 litre diesel engine supports my argument. A 110 Ah heavy duty commercial Lucas battery is rated at 750CCA so two of them makes 1500 CCA

However see what Barden say, but I would not limit my enquiries to Barden.
A call to Lucas batteries techincal department might be a good idea.

If you knew what trucks that engine was fitted to you could find out what batteries would be fitted to the truck.

 

[Cliveshep]

I'm with VicS on this and offer this suggestion, find a skip lorry or a dustcart, engine size similar, and ask the guys what batteries they have because that'll show you the ball park of what you need.

For me, and if it was my boat, with a 12 volt system on a 5.7 litre TC diesel I'd def not want less than a pair of 12 x 110AH and probably bigger if I could fit them in. It's a lot of lump for 12 volts and some serious starting power is needed to turn it over on a cold day!

You could of course fit a recoil starter or a kick starter...........? (joking)

 

[VicS]

find a skip lorry or a dustcart, engine size similar

I thought you were going to say, "nick the batteries".

 

[bedouin]

[QUOTE. If you think about it 760 CCA at 12V would be about 9kW - whereas the starter motor is unlikely to be rated at anywhere near that (perhaps 1.5kW at most?).

That calculation doesn't really apply. A starter motor is a series wound motor with very heavy windings. At initial start up, ie low rpm, they can take a massive current, well into the hundreds of amps, esp for a cold engine. The battery has to be able to supply that surge and still maintain a reasonable voltage. As the motor speeds up, the current will drop.[/QUOTE]
Yes - that is the point I was trying to make. Ohms law doesn't really apply for inductive loads

 

[Refueler]

having rechecked with my guys ... they say that 12v will have an initial hard job getting the engine to start turning over. But once it starts to turn momentum will take over and assist the starter in it's job. So you have high initial demand and then steady lower power demand to keep it spinning.

You also have to take into account that a diesel engine is not using battery to also power ignition side. Ok it's having a far higher compressive engine to turn over ... but it's purely that.

I do wonder if the OP boat has a 24v starter system that may have been misread to be 12V ? But then again - if everything else is working correctly - then wiring should be correct.

 

[VicS]

12v will have an initial hard job ........... lower power demand to keep it spinning

Pretty well sums it up.

a diesel engine is not using battery to also power ignition side

But a modern diesel has electronic systems that will need to be powered up, possibly a solenoid in the fuel supply and if it has glow plugs they can take the "zing" out of the battery before you get to the cranking phase.! And the high compression of a diesel certainly does impose a heavier load on the starter than a petrol engine would.

do wonder if the OP boat has a 24v starter system

maybe but he says not. Even if it is 24 volts the battery requirements are more or less the same. 2x 12 volt, 110Ah or 760 CCA but connected in series rather than parallel.

 

[Anthony]

From experience and comparing to similar sized engines I would be looking at 800-900CCA for that type of engine. there are plenty of batteries around that will offer that easily.

Ants