battery size

[PabloPicasso]

I have one 85ah battery for both engine start and domestic use.

I intend to add another battery, so what should i do here. Get the biggest one I can afford and find space for? It will be a lead acid type as I can't justify the expense of anything else for the amount of use it will get.

How much will my single cylinder volvo 2001s alternator realistically be able to charge? the run up the river to the mooring is about an hour usually.

 

[VicS]

Calculated your power useage (in Amp hours) if from the current consumption times the number of hours use for every item of equipment.

Size your battery bank so that it is not less than double the total.

The VP 2001 I believe has a 50 amp alternator. Within reason there is no limit to the size of the battery it can charge , but the more power you use the longer it will take.

If you use a lot of power you made need a fancy regulator to get the maximum out of the alternator, or even a larger alternator, in order to recharge the battery within a reasonable time.

 

[William_H]

Battery size

realistically something around the 100AHA will be big enough and physically manageable. Bigger the battery the more charge you will get from alternator if the battery is discharged. but of course bigger the battery the less % it will be discharged. But then bigger the battery the more expensive to buy and replace.
So it is up to you. Buy what is on special. olewill

 

[blackbeard]

If you rely on just one battery for both domestic and engine start, you are really pushing your luck (especially if you can't do hand starting).
Dedicated engine start battery doesn't need lots of capacity (amp hours Ah) but does need to supply lots of amps (A) to give cranking capacity. Car batteries are good at this. At a rough guess you might need about 400 A to crank the engine, and quite a small (in terms of dimensions) battery could do this.

See innumerable threads on this topic, also on switches. A simple Battery 1 / Battery 2 / Batteries 1 and 2 / Off switch will do the job, as with ANY main switch don't turn OFF with engine running. You can go fancy if you wish.

If you want to add another domestic battery, and can do so easily, then just do it. The more capacity the better. Most of the time, limit to charging current is what batteries can accept rather than what alternator can give.

 

[the_branflake]

I have the same engine charging a 55amp starter battery and approx a 110amp service battery via a VSR. The engine alternator appears to be upto the job and as VicS says it is a 50amp alternator as standard.

I am going to add a solar panel soon as i'm on a swing mooring.