12v or 6v house batteries

[Mistroma]

I'd agree that the Trojan 6v batteries are probably the "best" you can get.
However, capacity = volume available, so it's likely that you'll get in more amp-hours using 12v batteries, but if you do that you'll have to rewire. A circular argument...

My experience is that the cheapest, open-cell, lead-acid batteries have the lowest total cost of ownership - You'll be able to replace them 3 times for one replacement cycle of the Trojans and there's little to be gained by using a "named" brand, where you get stung for the name. When in doubt go for the heaviest you can get, there's no substitute for lead.

Still can't agree with the idea that you'll fit in more Ah capacity with 12V than 6V. All comparisons I made showed that T105s and 12V batteries were of similar volume for similar capacity for a pair of either type. The difference was usually around 4%. Shape of box and height available were usually more of an issue.

I guess that I was lucky with price of my T105s as they were around 40% more than cheapest leisure batteries I saw. Nothing like 3 x cost of a leisure battery. Perhaps T105s are sold at a much higher premium in other parts of the world.

I know that prices vary a lot here in Spain but I have seen T105s online recently (incl. del.) for around 147 Euros. I haven't checked to see if I can get a 110Ah leisure battery for under 50 Euros.

 

[Rigger Mortice]

My experience is that the cheapest, open-cell, lead-acid batteries have the lowest total cost of ownership - You'll be able to replace them 3 times for one replacement cycle of the Trojans and there's little to be gained by using a "named" brand, where you get stung for the name. When in doubt go for the heaviest you can get, there's no substitute for lead.

For most of us I would agree with that. But OP is a liveaboard and I suspect that most liveaboards would say that they need to rely on their batteries and therefore need the best that are available.

 

[KellysEye]

.Thank you Kellyseye.. Is it best to stay with 4 6v or change to 4 12v...?

Many long distance boats have 6v Trojan T105s for the simple reasons they are used 24x365 work well and last five to six years. I'd stick with them.

 

[GrahamM376]

Thank you to every one for their help and advice. Looking at the options and room available I think the best thing for me would be to go with the T105's 6v and increase the batteries from 4 to 6 to give me the extra power.
Again thank you for all your replies and advice.

If you want to maximise capacity in the same footprint as T105, go for the slightly taller T125. At 20 hour rate T105 are 225AH, T125 240AH. I got mine from Tayna and they will post anywhere including discount for mixed pallet loads if you can find others wanting to order batteries.

 

[AngusMcDoon]

For the same 'volume' of batteries in the battery compartment, you will have - very roughly - twice the amount of power available from 12v than 6v.

The maximum power available from a battery or bank is Cold Cranking Amps multiplied by voltage. This value is of little importance for house batteries, only engine starting batteries. For house batteries the total energy needs to be maximized. There is little difference in this energy capacity whether pairs of 6V batteries in series then in parallel are used or just 12V batteries in parallel for the available volume.

Energy is what is needed to do work. Power is the rate at which energy is supplied or used. You need lots of energy in your house batteries to keep the fridge running all weekend, but little power. You need lots of power to start your cold engine on a frosty morning, but little energy. That's why we have different battery types for these different needs.

 

[Richard10002]

There seem to be some misconceptions here:

A 6v battery of 225Ah is roughly the equivalent of a typical 110Ah 12V battery. You obviously have to buy the 6v batteries in pairs, and there are some slight size differences that might mean rearranging the space so that 6V batteries will fit.

Now that you can buy Trojan T-105 for £107.50, there is no real difference in price between a couple of good brand 12V 110Ah batteries, (e.g. Varta), and a couple of Trojans.

You can buy 3 cheap 12V 110Ah batteries for about the same as a pair of Trojans - I think it is now a false economy.

When I replace my batteries later this year, it'll be with a pair of Trojans - hopefully that'll be the last replacement for a few years.

 

[GrahamM376]

Now that you can buy Trojan T-105 for £107.50, there is no real difference in price between a couple of good brand 12V 110Ah batteries, (e.g. Varta), and a couple of Trojans..

On a pure price comparison I could agree but deep cycle batteries have a cycle life 4-5 times greater than so called leisure. Unfortunately, some people are strapped for cash so go for the cheaper shorter life option.