CCA for volvo md1b

[pikeyrm]

I would like to treat my engine to a duel battery system and as i have a leisure battery i would like to add a specific one for starting the engine, does anyone know what the cold crank is for the volvo penta md1b and suggest the best battery for the job

 

[VicS]

This sort of question has been asked before regarding batteries for small VP engines. All they ever seem to specify is a max of 60Ah.

MD1B has a Dyna-starter ? If so the current is relatively modest. Any small vehicle starter battery should do the business.

 

[pikeyrm]

so what would it do if you use i bigger Ah battery do. As i am currently using a 110ah one

 

[VicS]

I think, I only think I do not know for sure, if you use a larger battery than than that specified it could deliver a much higher current if the starter was stalled and perhaps then burn out the starter.

 

[pikeyrm]

thanks vics so for peace of mind i would be better buying a new battery of a max Ah of 60 and use that one for engine and then use the other for the electrics.
The manuel says that 60 is max for the electrics but nothing about the engine.
i am in limbo over this

 

[sailorman]

buy another leasure battery

 

[aluijten]

Battery capacity is something else than CCA (Cold Cranking Amperes). Typically for a starter battery the capacity is of no real importance. It's the CCA that makes the difference. This will tell you the number of amperes that the battery can supply during starting. On the top of my head your engine has a 1kW starter motor, meaning something like 100 amps (at approx 10 volts across the battery during the start).
Basically even a small 45 Ah battery can supply around 300 Amps (CCA), so any (car) battery will do.

Arno

 

[VicS]

I would not lose any sleep over it. You dont need much capacity for engine starting, just need to be able to supply enough amps for a few seconds and any small starter battery should be able to do that. You can then use a larger battery as your domestic battery. Must bear in mind though that if you do only have a Dynastarter your recharging capabilities are rather limited (just as I have forgotten the starting current I have also forgotten the output current of a Dynastarter) You cannot run a big battery flat with fridges, ice makers, radars, plotters and other computers. underwater lighting etc and expect to recharge it in 5 minutes.

Might bear in mind though that using a battery intended for a particular vehicle application to start a MD1B might just invalidate its guarantee. The alternative is to pay through the nose for a battery recommended by a marine battery specialist.
Got you by the short and curlies!

 

[pikeyrm]

mine has a cca of 700, the real question is
is too much cca a good or bad thing?

 

[aluijten]

Having a very high CCA means the voltage drop will be lower compared to a smaller battery. That might imply that your starter motor is working at higher power ratios than anticipated by Volvo. The net effect will be that you might fry it during prolonged starting. If your engine fires without too much time starting, I would not worry about that. What you could do to test is feel the temperature of the starter directly after the engine started. If it's boiling hot you could run into trouble, but I'd be surprised if this is the case
If I remember correctly most starter motors are specified for 9 volts, so you could also measure the voltage across the starter during the actual start. If that is above 10 volts it might be wise to use a smaller battery.

Arno

 

[pikeyrm]

sorry to sound stupid but electrics are not my strong point (yet)
but does it make i difference that it is dyno start?

 

[ump010]

I have an MD1a its starting current (dynastart) is 190A inrush current (only for the first second or so) then a steady 90 - 100 A.

The dynastart will output about 9A into a receptive battery. The reason VP say a max battery size of 60AHr is that if the dynastart tries to charge a larger battery it can overheat, it is not ventilated.

I have fitted an alternator to my engine, not that difficult. The dynastart is used for starting and charging the engine battery (60Ahr) and the alternator is used to charge the domestic batteries (2 X 85Ahr).

Because the alternator can use quite a bit of the engine's rated power I have fitted a switch in the alternator field circuit so that I can turn the alternator charging off when I need all the engine power. To do this you must switch the field circuit and not the alternator output.

Hope this helps.