Dynastart; suitable battery

DavidTocher

DavidTocher

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I'm replacing the dud car starter battery in my boat (the only one fitted). As a dynastart is small as starter motors go (1HP) can I use a leisure battery or a deep discharge battery for starting? Will it have enough umph or shall I use a cheap starter battery as before.



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You have a bit of a conflict here, IMHO

If you use the batery for starting the engine, then the load will knacker a leisure battery PDQ.

OTOH, starting batteries do not like to be cycled through discharge/charge too often, hence your problem.

If you want the cheapest option, then go for the cheapest car battery you can find, and try to keep it topped up as far as possible. It will probably last a couple of years at least.

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Starting batteries need to supply loads of amps in a short bursts (measured as Cold Cranking Amps CCA) . Deep-cycle batteries (which are substantially more expensive) supply low amps for a long time and can support a greater level of discharge without damage, using them for inappropriate uses will shorten their life substantially and will be a waste of money. Buy a good quality car battery, look after it and it should serve you well - you get what you pay for.

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Although, unfortunately, we don't have info on your boat or engine, I think you're worrying unecessarily. A 110Ah 'Leisure' battery (£39 from TowSure) should easily start your engine and have enough spare for moderate use..............though I'd always prefer to keep a dedicated battery for engine starting (a typical car battery).

Vic

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Volvo used to specify 60AH batteries for their MD11 engines,and the reason was that if the battery was too large it could overload the dinastart when on charging mode .So I don't think that you should fit a battery much larger than 60 AH.
Dinastarts aren't the most efficient devices.

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Hi David

As BOAT30 has stated you cannot use a large battery (90 - 110AH) with a dynastart. The starting is not the problem but the charging side is. The Dynastart will only put out between 8 - 11 amps therefore if you happen to flatten that battery and the dynstart tries to charge it flat-out then the windings will burn-out leaving you with an expensive bill. I know this as the Albin Vega was fitted with teh Dynastart as standard and this has happened many, many, many times. Keep below 60AH battery or face the expense of a rewind on the dynastart.

<hr width=100% size=1>Albin Vega "Southern Comfort" V1703
 
I think dynastarts give a MAXIMUM of 8 amps or so. This means that you are unlikely to be able to charge a large capacity battery properly and most electrical loads will be a problem. Nav. lights and instruments will leave very little over for replenishing the battery.
On the other hand its perfectly possible to make up a bracket to hold a car alternator, make a pulley to go on the flywheel and get a reasonable charge rate. Do not have the dynastart output in parallel with the alternator. I did and the high intermittent voltage from the dynastart did for the alternator regulator

<hr width=100% size=1>Roger
 
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