Trojan Batteries. 12 volt or 6 volt ?

[cygnusv]

Which is better:-

2 x 12 volt x 105AH or
2 x 6 volt x 225 AH

Both batteries are about £300 the pair

Seems to me that the 6 volt version has more poke and only half the topping up!

Thoughts anyone?

PS. For 12 volt system

 

[macd]

Which is better:-

2 x 12 volt x 105AH or
2 x 6 volt x 225 AH

Both batteries are about £300 the pair

Seems to me that the 6 volt version has more poke and only half the topping up!

Thoughts anyone?

PS. For 12 volt system

A pair of 6V wired for a 12V system offers 225Ah (not 2 x 225), so less than a 10% improvement over a pair of 12V batteries. Of more interest to you may be the T105's longevity. Trojan's own figures state it offers roughly twice the cycles of the 12V. (1100 cycles v 600, or thereabouts, IIRC.)

P.S. As regards topping up, yes, you'd have half the cells to deal with, although the total volume may prove similar. Our 4 x T105 take around 0.5 litre per month between them (usually in hot conditions). I'm not sure about the recommended charging regime for the 12V Trojans, although their web site will tell you. For T105s, you're advised to charge at up to 14.8V. Plevier, the forum battery expert, suggests a little lower than this might increase longevity, but you'll need a charging system that can reach more than a typical alternator provides to really look after them. If you're regularly on shore power, no reason a good charger can't attend to this (preferably one with an equalization cycle). Routinely undercharging isn't good for them.

 

[Bobc]

6v every time.

 

[cygnusv]

A pair of 6V wired for a 12V system offers 225Ah (not 2 x 225), so less than a 10% improvement over a pair of 12V batteries. Of more interest to you may be the T105's longevity. Trojan's own figures state it offers roughly twice the cycles of the 12V. (1100 cycles v 600, or thereabouts, IIRC.)

P.S. As regards topping up, yes, you'd have half the cells to deal with, although the total volume may prove similar. Our 4 x T105 take around 0.5 litre per month between them (usually in hot conditions). I'm not sure about the recommended charging regime for the 12V Trojans, although their web site will tell you. For T105s, you're advised to charge at up to 14.8V. Plevier, the forum battery expert, suggests a little lower than this might increase longevity, but you'll need a charging system that can reach more than a typical alternator provides to really look after them. If you're regularly on shore power, no reason a good charger can't attend to this (preferably one with an equalization cycle). Routinely undercharging isn't good for them.

Yes, my thoughts too. I have 4 x 105's on my 24 volt system with Victron charger and Victron mppt solar looking after them. Later Victrons can be adjusted via a phone app. This is perfect for correctly adjusting charge protocols.

I asked the question for a friend because I have no experience of 12 volt Trojans but love my T105 6 volts.

Thanks

 

[macd]

Yes, my thoughts too. I have 4 x 105's on my 24 volt system with Victron charger and Victron mppt solar looking after them. Later Victrons can be adjusted via a phone app. This is perfect for correctly adjusting charge protocols.

I asked the question for a friend because I have no experience of 12 volt Trojans but love my T105 6 volts.

Thanks

You're very welcome. As you'll know there's a bit more faff changing to x 6V. I hope your friend has a friend with a decent heavy-duty crimper

 

[Minchsailor]

6V, as I reckon the cells are bigger. I'm not sure if that affects longevity, but a gut feeling tells me so.

 

[KellysEye]

I used 6v they lasted for five years used every day when long distance sailing.

 

[DuncanHall]

I use the 12V because they fit. The 6V units are too tall for my battery compartment.

 

[sailinglegend420]

Redundancy is the best reason for going for 2 x 105Ah instead of 2 X 6v Golf carts.

If one of the 12v 105Ah fails then just disconnect the faulty one and you can still get home.

If one of the GC 6v fails you are stuffed.

Just make sure the 12v 105s are the same deep cycle quality as the 6v Golf Carts.

More smaller batteries in any installation is always better than less big ones.

 

[macd]

Just make sure the 12v 105s are the same deep cycle quality as the 6v Golf Carts.

The OP doesn't specify which models he's considering, but on Trojan's own figures the commonly available 12V "deep cycle" jobs offer much fewer lifetime cycles than the ubiquitous T105 6V range (cf post #2). There is no such thing as a 12V T105.

 

[Mikedefieslife]

Trojan now do true deep cycle AGMs. You might prefer them (if not the price) over FLA. No maintenance, no worries. Think they come in 6v.

I have the 6v T105 FLA because they came with the boat, and they do seem to be great batteries. If/when I come to buy again (provided I don't go LiFePO4), I'd get the 12v AGM instead.

 

[crisjones]

As always the selection of batteries is not a simple choice!!.

As Mac says the Trojan 12V batteries are not the same as the 6V - ignoring the obvious voltage difference. The 6V are much more designed and built as proper deep cycle batteries for heavy duty use, this is why they are commonly called golf cart batteries - they are charged overnight and then power a golf cart all day before being charged again.
The 12V batteries are not designed and built for the same type of application so you are not comparing apples with apples.
The best choice of batteries on a boat depends on many factors and a simple question like should I have Trojan 12V or 6V is impossible to answer without much more info about your usage and requirements - they are very different batteries.

If you are a "marina type" boat then probably the 12V batteries will be ok, if you spend lots of time at anchor without shore power then the 6V golf cart batteries will probably be more suited to your needs.
Whatever you choose it is wise to consider that batteries are never a fit and forget choice, you will still need to manage your batteries according to the usage you are asking of them.
If you give us more info about your sailing/cruising style then you are likely to get a more appropriate answer.