Yet another 'which battery to buy' topic

Right. I think I will go with @Plum recommendation and will buy Hankook. 2 for redundancy. Now thinking - should I go with 65 ah or 85 ah or 110 ah per battery. My energy needs are rather low, I am not planning any extensive journeys and I wonder if going for bigger is not a waste of money and material.
 
slawosz said:
Right. I think I will go with @Plum recommendation and will buy Hankook. 2 for redundancy. Now thinking - should I go with 65 ah or 85 ah or 110 ah per battery. My energy needs are rather low, I am not planning any extensive journeys and I wonder if going for bigger is not a waste of money and material.
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This is the spreadsheet I used to help me decide on battery capacity plum electrical loads 3.xlsx

Www.solocoastalsailing.co.uk
 
If weight isn't an issue, I'd go for the biggest you can comfortably lift in and out. You'll enjoy the extra capacity long after you've forgotten the pain in the wallet. All the same, unless you've got regular access to mains power for recharging, I'd go for less battery and solar power.
 
I can fit 2 110 ah on my Sadler 25. But charging is the issue. I will have only solar and most of the trips would be day trips, or racing so not much engine. Depending on available leave I might spend few days pottering around the cost, but in such case I can recharge in marina.
 
Plum said:
This is the spreadsheet I used to help me decide on battery capacity plum electrical loads 3.xlsx

Www.solocoastalsailing.co.uk
Click to expand...
Very useful and illustrates perfectly why 2 large capacity batteries and a 1 2 B switch is not the way to go. The demands on the engine battery are tiny and almost immediately replaced by the alternator. So makes sense to have a small battery (my new installation will have a 32Ah) and a split charge system so the engine battery is charged first then all the charge goes to the house. Crucially though, there are no other loads on the engine start battery. If you try and do the same with a 1 2 B switch and select one battery for starting, it is also taking house loads so will take longer to recharge before manually switching to the other battery. If you are using solar you can then connect just to the house which is the one that needs it - the engine start is always fully charged. You can if you wish install a parallel switch so that in an emergency you can use the house battery to start the engine, although in the 25 years I have had such a system I have never needed that.

A small car battery of around 45Ah for the engine and a leisure battery of +/-100 Ah is more than enough for a small 25' boat with basic electronics.
 
Tranona said:
Very useful and illustrates perfectly why 2 large capacity batteries and a 1 2 B switch is not the way to go.
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It illustrates why doing it wrong with a 12B switch is not the way to go. Doing it right, with a split charging relay of some kind, gives you the option of using the domestic battery to start the engine if the starter battery decides it doesn't want to play any more, which is always inconvenient and sometimes potentially dangerous.
 
Tranona said:
Very useful and illustrates perfectly why 2 large capacity batteries and a 1 2 B switch is not the way to go. The demands on the engine battery are tiny and almost immediately replaced by the alternator. So makes sense to have a small battery (my new installation will have a 32Ah) and a split charge system so the engine battery is charged first then all the charge goes to the house. Crucially though, there are no other loads on the engine start battery. If you try and do the same with a 1 2 B switch and select one battery for starting, it is also taking house loads so will take longer to recharge before manually switching to the other battery. If you are using solar you can then connect just to the house which is the one that needs it - the engine start is always fully charged. You can if you wish install a parallel switch so that in an emergency you can use the house battery to start the engine, although in the 25 years I have had such a system I have never needed that.

A small car battery of around 45Ah for the engine and a leisure battery of +/-100 Ah is more than enough for a small 25' boat with basic electronics.
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Speaking as a liveaboard for 6 odd years

I switch to starter on startup, then straight to B for the run, by which time all batteries are full, then starter off

Never a problem, 2 starters, one 8+ years, the other 3, house bank 4 years old
 
SandyP said:
Speaking as a liveaboard for 6 odd years

I switch to starter on startup, then straight to B for the run, by which time all batteries are full, then starter off

Never a problem, 2 starters, one 8+ years, the other 3, house bank 4 years old
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That is OK if you have a daily routine and are not prone to forget - but when there is an automatic system that removes the need to remember why not use it? Particularly as it automatically apportions the charge to the battery that needs it most. Why do you want to be trying to charge the start battery alongside the house when it will be fully charged within minutes of the engine starting? By paralleling both batteries you are drawing on your start battery for house loads. The engine start does not need to be large - many people fit batteries that are larger than needed and with modern engines the drain on the battery is minimal. Small capacity high amps dedicated start batteries are readily available and you can use the extra space for a bigger house bank which is surely what you need as a liveaboard. Never need to remember to switch over banks again.

I can see you are trying to make the most of an existing and perhaps inappropriate system but surely if you have to live with it permanently it is worth going back and working out a more efficient system?

Sorry for repeating the post you replied to and of course feel free to ignore!
 
Tranona said:
That is OK if you have a daily routine and are not prone to forget - but when there is an automatic system that removes the need to remember why not use it? Particularly as it automatically apportions the charge to the battery that needs it most. Why do you want to be trying to charge the start battery alongside the house when it will be fully charged within minutes of the engine starting? By paralleling both batteries you are drawing on your start battery for house loads. The engine start does not need to be large - many people fit batteries that are larger than needed and with modern engines the drain on the battery is minimal. Small capacity high amps dedicated start batteries are readily available and you can use the extra space for a bigger house bank which is surely what you need as a liveaboard. Never need to remember to switch over banks again.

I can see you are trying to make the most of an existing and perhaps inappropriate system but surely if you have to live with it permanently it is worth going back and working out a more efficient system?

Sorry for repeating the post you replied to and of course feel free to ignore!
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I crewed on an old Macwester a while ago which was equipped with a 12BO switch hidden beneath a bunk in the rear cabin. Needless to say, the switch was often left on B due to not being able to see the switch properly, memory lapses, other duties taking precedence, etc.
It was only luck that saved us from flattening both batteries and being unable to start which could easily be avoided by fitting an automated charging system but the owner was too stingy to shell out £50.
 
Tranona said:
That is OK if you have a daily routine and are not prone to forget - but when there is an automatic system that removes the need to remember why not use it? Particularly as it automatically apportions the charge to the battery that needs it most. Why do you want to be trying to charge the start battery alongside the house when it will be fully charged within minutes of the engine starting? By paralleling both batteries you are drawing on your start battery for house loads. The engine start does not need to be large - many people fit batteries that are larger than needed and with modern engines the drain on the battery is minimal. Small capacity high amps dedicated start batteries are readily available and you can use the extra space for a bigger house bank which is surely what you need as a liveaboard. Never need to remember to switch over banks again.

I can see you are trying to make the most of an existing and perhaps inappropriate system but surely if you have to live with it permanently it is worth going back and working out a more efficient system?

Sorry for repeating the post you replied to and of course feel free to ignore!
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As the engine is running how am i using my starter for house loads?

Once the starter is charged, as you say, quickly, what difference does it make, then the house batteries will be soaking up the available charge from the alternator?

Is better start start the engine from the starter rather than the house bank so i do
The engine doesn't start itself so a special routine is hardly necessary, nor special automated systems
When i shut down I only have to turn off the start bank, as you would anyway during closedown

If i can't remember to throw the right switch at the right time, I really shouldn't be on a boat

I don't really see your objection, simple fact, it's worked very well for me, batteries lasting well
 
How do you know when your start battery is fully charged? When you set your switch to B then both banks are feeding the house circuits. A split charge system always keeps the 2 banks separate and allows the VSR to make the decision when to stop charging the start battery. Therefore no need to isolate it because it is already isolated. For emergency if your start fails, you can have a means of either connecting the house to the starter or paralleling the 2 banks - never had to do that in the 30 odd years of having a split system.
 
If someone is set in their ways and confident that they will NEVER forget to set the switch appropriately, no logical persuading will change their mind. You can only hope they don't get caught out.
As for me, I'd rather have an automatic system.
 
ghostlymoron said:
If someone is set in their ways and confident that they will NEVER forget to set the switch appropriately, no logical persuading will change their mind. You can only hope they don't get caught out.
As for me, I'd rather have an automatic system.
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I would get caught out, so I definitely want an automatic system!

On Jazzcat, though, I have two independent systems, port engine and domestics, and starboard engine only. Each engine charges its own battery, while the solar panels charge both through a dual battery controller. I have isolating switches for both, plus another to allow each battery to start the other engine.
 
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