Best batteries for Dynastart...

[Will-1952]

In tiny print next to the wiring diagram for a MD2B with starter-generator in your owners manual it says " MAX,BATTERY CAPACITY 60Ah"

If your domestic power requirements need a large domestic battery adding an alternator would be a good idea to charge that .......... item 13 in the wiring diagram.

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Many thanks, this is really helpful, I now have a Yuasa Silver 60Ah starter battery and opted for a slightly larger 80Ah leisure battery.

 

[Will-1952]

Welcome.

Two different requirements. I assume you have 2 separate circuits, one for engine start and one for domestics with split charging. The engine start can be a simple FLA of around 5-60Ah of the type used on small diesel cars. For domestics which have a different cycle of operation the size will depend on the demands you put on it, but typical for that size boat would be a bank of between 100-200Ah. You can use FLAs, most commonly what are termed "leisure" batteries which have a reasonable life and modest cost at around £90 per 100Ah or AGMS which typically last up to twice as long for a 40% premium in initial cost.

However this assumes that you have adequate charging capacity and suspect that the Dynastart will cope OK with the engine start, but be limited in how much charge it can put into a house bank. Remember these engines were made when electrics on boats were very basic and you may well have to consider additional means of charging if you want to use modern things like electronics, autopilot, fridge etc.

 

[Will-1952]

Many thanks for your help. Yes, two separate circuits and I now have a 60Ah starter battery and an 80Ah leisure battery. Please see full details in my reply to Sarabande.

 

[Will-1952]

There was an alternator kit available at one time but very few of the major components are still available. It would be very much a DIY job now unless second-hand parts could be found.

Many thanks for your reply, much appreciated.

 

[Will-1952]

Many people with Dynastarts on old Volvos and simuilar now-vintage engines spun the engine up on the Dynastart then once the huge flywheel was spinning dropped in the decompressor lever or levers. I treated my Volvo's Dynastart as highly convenient in saving having to hand crank. It was always pretty rubbish at battery charging, but I was not running lots of electronics or a fridge.

I don't think any 12v battery can be "too powerful" for a Dynastart. A battery could though be too high AH capacity to be effectively charged in typical low engine hours of a sailing yacht.

Many thanks for your reply, much appreciated.

 

[Will-1952]

Dynastart ..... brings me back to days of Vire .....

As Tranona says - Dynastart hails from the days of limited demand on electrics. So they were actually poor on charging. The average Centaur in those days would potter along with one or maybe two modest standard Lead Acid batterys ....
I assume the boat still has the 1 - Both - 2 - OFF switch ? If so then I honestly wouldn't waste money on fancy batterys ... a couple of reasonable Lead Acids of 80 A/hr or more each is good. Its no good going too high on capacity as the Dynastart is usually not capable of fast / high rate charging.

The name Dynastart is an amalgam of the two words : Dynamo and Starter. That should give you a clue as to the vintage of such a device.

I know people who have relegated the Dynastart to start only function and modified engine to have a dedicated alternator - a much better solution.

Many thanks for your reply, very helpful.

 

[Will-1952]

Keep the Dynastart with a standard starter battery of around 60AH as VicS said, then add an Alternator to charge the ships batteries (leisure) , 3 to 1 step up from crank,almost any Alternator will be a big improvement.
Jim

Many thanks, much appreciated.

 

[Will-1952]

Many thanks to everyone for the help and advice. I have tried to reply to everyone individually too and hope I haven’t missed anyone.