Starter Battery - what size ?

[Tiger Lily]

Can you help here ?
I need a new starter battery. The engine is VP 170 HP (D3) but I am not sure what the AH needs to be. I have known a battery to last much beyond 3 years.

 

[MoodySabre]

It doesn’t need big Ah, what it needs is high CCA rating. Cold Cranking Amps. Choose one on that basis.

 

[Chris_d]

According to google you need 760 CCA min

 

[Momac]

The first thing is to ensure the new battery will physically fit and the terminals are compatible with the terminal clamps on the boat,
I have used Hankook batteries which are sold as dual purpose and have a high cca rating as well as good Ah rating.
Example below , if it will fit on your boat.

 

[Tranona]

Use the same battery that would be used for that size engine in a car, probably around 95Ah. No need for a so called "leisure" battery if it is a dedicated engine start. For longer life (10 years+) choose an AGM. Just make sure it is kept charged over the winter

The recommended AGM for Volvo cars fitted with the same engine is this tayna.co.uk/car-batteries/exide/ek960/ or a basic LA is this tayna.co.uk/car-batteries/varta/g3/ The 30% price premium for AGM will give at least 50% longer life, maybe up to double in my experience for engine start

 

[LittleSister]

Can you help here ?
I need a new starter battery. The engine is VP 170 HP (D3) but I am not sure what the AH needs to be. I have known a battery to last much beyond 3 years.

I wonder whether you intended to write you have never known a battery to last much beyond 3 years?

Battery life will largely depend on -
(a) how often they are severely depleted. For an boat engine start (only) battery of adequate size with a good charging system/regime this should be almost never; and
(b) whether they are overcharged (excess voltage - largely dependent on the regulator or 'smart' charger working correctly);
(c) whether they are left uncharged for long periods (the battery will slowly self-discharge when not in use and not being charged), or have some extraneous load on them when not in engine use.

I have had both car and motorcycle batteries last up to 8 years, and even once had boat batteries last about 10 years, but also in other circumstances when 'domestic' batteries were regularly severely depleted, had inadequate charging (from an outboard 'lighting circuit', left uncharged for long periods, an alternator regulator had failed giving excess charging voltage, or there was an overlooked small load draining the battery when the boat was not in use, they have understandably failed before even 3 years.

I am not convinced that an AGM battery is worth the additional cost for use as an engine start (only) battery (but I am open to persuasion). My understanding is that the AGM advantage is it copes better with repeated severe discharges. This should never happen with an engine start battery - starting requires huge currents but only for seconds and hence actually only a very small proportion of the battery's Ah capacity. Once the engine starts it is fully recharged in very little time. I have bought AGM as boat domestic batteries, as in my case these often do get severely discharged when the boat is in use but engine not running (no shore power or solar), but intend to buy non-AGM when I soon replace my engine start battery.

My advice for engine starting (only) use would be to buy a decent quality (name brand, rather than budget priced) lead acid (non-AGM) battery, with a CCA capacity above the bare minimum specified (batteries will inevitably slowly lose some capacity over time). Were this to fail in less than, say, 5 years, there is probably something wrong with the charging system/regime, or some stray load on it, as outlined above.

 

[Tranona]

You are right that the advantage of AGM is less obvious for a start battery, but the lower self discharge rate is a benefit. AGMS are used on vehicles with stop start because of their better tolerance of regular charge discharge cycles and higher acceptance rates. As to life, the EGM in my Morgan lasted 19 years with a similar usage pattern to a boat - short periods of activity followed by long periods of inactivity. Plugged into a trickle charger in the winter like now when it has not been out for over 2 months. I had AGM start - the same Exide I linked to in my Bavaria. Not really needed for a 30hp, but guess Bavaria got a good deal as all 5 batteries were the same. All still sound after the 6 years before I sold it.

 

[Tiger Lily]

Thank you everyone for your comments

 

[VicS]

Can you help here ?
I need a new starter battery. The engine is VP 170 HP (D3) but I am not sure what the AH needs to be. I have known a battery to last much beyond 3 years.

Your owners manual will specify the capacity and maybe the CCA for the particular variant of the D3 170 which you have.

Be sure to check the external dimensions and compare with your battery space. Also check the terminal layout i.e. left or right handed

If you have mislaid your manual you can download one from Manuals & handbooks | Volvo Penta UK & IE

 

[Plum]

Can you help here ?
I need a new starter battery. The engine is VP 170 HP (D3) but I am not sure what the AH needs to be. I have known a battery to last much beyond 3 years.

If you are only getting 3 years from a regular LA starter battery then something is wrong. I regularly get 8 years and my last LA starter battery on a 200hp engine lasted 10 years.