Domestic battery bank: lowest life cycle cost?

[Kelpie]

OK I've done enough Googling on this to make my brain start to hurt a bit.
I'm pricing up the cost of a decent domestic battery bank (400+ Ah) and finding it a bit of a minefield.
At first I came across cheapo sealed Pb-Ca batteries, 110Ah for about £60 a pop, but apparently only good for 250 cycles- seems pretty poor.
Or similar thing but with a decent brand name stuck on the side, e.g. Varta- for maybe double the price.
Or something more serious looking like the Trojan 6v range, claimed to be good for 1200 cycles, but we're now talking a sixfold increase in purchase cost.

And then there's the AGM/Gel/FLA debate...

And of course there's Li-ion with the different charging regime required, and far better charge efficiency, but absolutely eye-watering prices.

So... I'm hoping that somewhere, someone has worked all this out already. For full time liveaboard use, where the batteries are being maintained by a big solar array but also being cycled daily, which option works out the cheapest overall?

 

[Trident]

It depends how long you intend to keep the boat and how much you will use it. I went with Trojan 6 volt as they have a proven life span of over 15 years if treated well - that is to say don't discharge too deeply and top up the water correctly. I never went below around 30% discharged (70% full) and lived aboard full time for 5 years with them with no issues whatsoever and the new owner of the boat when I sold it has done so for another 2 so far and doesn't seem to have any problems either. They are expensive but when you look at the cost over 15 years they work out lower than anything else.

The downside is of course that technology moves quite quickly and 5 or 10 years from now you may want to change to some newer better super lightweight battery system that has suddenly become affordable...

 

[sailaboutvic]

We used cheep batteries for as long as we been liveaboard but just lately I found we having to pay over 150€ for a 110 ah and they just not lasting so we bit the bullet this year and brought 6v Trojan if you still in the UK I suggest you buy them there , we had to pay near on 900€ with delivery for a set of four , only time going to tell if we made the right choice but as full time liveaboard we relie on our batteries for 9 months each year without shore power .
If I was asked the question two years ago I would had said buy cheap batteries but with the last lot only lasting two years it just don't add up any more .

 

[GHA]

Not sure there is an answer out side of lab testing. Trojan t105s have long been a favourite of cruisers as they will take a lot of abuse and keep coming back for more. Quick google looks like about 150 each so 2.5 times the cost of your cheap one for similar Ah.
As the saying goes, most boat batteries don't die, they are murdered higher end batteries might last living with not being fully charged which would kill the cheap ones very quickly. Also living abourd for me t105s will be top of the list unless something better comes along, firefly are getting very good reviews from peeps who know and look to handle partial state of charge but do cost a posh arm and a leg. Another benefit of the likes of the trojans is they will handle high voltage charging which might trash cheapies quicker, takes such a long time to really really get back all the way to fully charged, a few more 100 mV can make a difference between 99% and 100%.
Hard or impossible to quantify but i think paying the extra is worth it, they'll take a bit of maltreatment which would trash a cheapie quickly. One day i might splash out on a firefly as well and switch lver to that when not getting back to 100% is likely like on ocean passages, well pricey though :nonchalance:

 

[TQA]

6 volt golf cart batteries are the way to go. Trojan T 105 are the gold standard. They are good for 1400 cycles. lots of cruisers claim more. Traditional wet cell technology so need topping up with distilled water.

My 6 need about a liter a month in the tropics.

 

[macd]

6 volt golf cart batteries are the way to go. Trojan T 105 are the gold standard. They are good for 1400 cycles. lots of cruisers claim more. Traditional wet cell technology so need topping up with distilled water.

All true, but I'd urge anyone considering them to factor in the type of use the batteries will be put to. T105 (and anything else with antimony alloyed plates) have a substantial rate of self-discharge. That's not an issue if you're on the boat 10 months or so of the year, but may be for extended absences. In that case, calcium-alloyed plates may be more attractive.

 

[Mistroma]

Almost everything like this is a compromise and depends on how much you value price, time, effort, performance etc.

I went with T015s in 2012 as they weren't that expensive in UK vs. other options and worked out at £1.08/Ah. I knew I'd look after them and thought they'd be much more expensive in most places I'd visit. AGM, gel were more expensive and top end ones represented a much higher financial risk. They'd need to last a lot longer to make financial sense and low maint. wasn't a big benefit. I've seen someone lose 5,000-6,000 euros worth of batteries in little more than a year as a result of a charging fault. He went back to using cheap batteries.

It's possible that I'll end up with really cheap batteries if my T105s fail, though they show no signs of any issues yet. Solar is such a game changer that I don't deep-cycle for much of the summer nowadays. I'm getting on a bit and even cheap batteries might outlive me

Different story if you live on a boat over the winter and likely to discharge more deeply. Usage and charging system will have a huge impact on battery life and benefit of T105 vs. cheap sealed battery (assuming they actually are a lot cheaper now).

 

[RobbieW]

Almost everything like this is a compromise and depends on how much you value price, time, effort, performance etc.
... Usage and charging system will have a huge impact on battery life and benefit of T105 vs. cheap sealed battery (assuming they actually are a lot cheaper now).

+1 Battery value is a function not only on the price of the battery, it includes the ability to charge back to 100% regularly whilst managing the depth of discharge to maximise the life of the bank

 

[Kelpie]

Thanks for the replies.
As to usage- I've posted this in the liveaboard section as the intention is to become full time liveaboard cruisers. We expect to have a decent wattage of solar panels, but hope to get by without a genny or wind gen. The main consumers of power will be the fridge (SWMBO would love a freezer too but I don't know if that's realistic) and charging laptops etc. We're unlikely to have a watermaker, microwave, or air con. We expect to be cruising mainly in quite sunny places, and living on the hook most of the time.

Self discharge shouldn't present a problem as the boat would be in continuous use, unless stored in a yard or marina for a few weeks, where there would be access to shore power anyway.

Would I be right in thinking that going down the cheap route would probably mean having to have a bigger bank? If you can't discharge them very far, e.g. only to 70%, without damage then you obviously need more Ah compared to true deep cycle batteries that can go below 50%. So that helps even out the cost difference a little, before you've even factored in the lifespan. But when refitting a boat for liveaboard use there's a lot of things to spend money on and buying cheap batteries at 60p/Ah is very tempting, compared to Trojans at £1.60/Ah.

I've been really surprised at the low number of cycles for the cheap Pb-Ca batteries- how is this figure arrived at?

 

[Kelpie]

Ok just found a lower price on the T-105s, works out at £1.28/Ah.
The cheap batteries are rated for 250 cycles, the Trojans for 1200.
So although the Trojans are twice the price per Ah, they should last nearly five times as long. Certainly seems to make sense...

 

[geem]

Trojans would be my choice but when my last set of batteries died we were in the Caribbean and the Trojans were not easily available. We have a huge battery box so I opted for four big truck batteries. We rarely discharge below 90% so they get an easy life. They are about 1000 amp hour and weigh a 1/4ton. With solar, wind, towed and a diesel gen they never suffer from lack of charge. They have been in two years so far as full time liveaboards in hot temperatures continually with no signs yet of loss of capacity. Even so, I would love some Trojans

 

[Graham376]

Self discharge shouldn't present a problem as the boat would be in continuous use, unless stored in a yard or marina for a few weeks, where there would be access to shore power anyway.

Would I be right in thinking that going down the cheap route would probably mean having to have a bigger bank? If you can't discharge them very far, e.g. only to 70%, without damage then you obviously need more Ah compared to true deep cycle batteries that can go below 50%. So that helps even out the cost difference a little, before you've even factored in the lifespan. But when refitting a boat for liveaboard use there's a lot of things to spend money on and buying cheap batteries at 60p/Ah is very tempting, compared to Trojans at £1.60/Ah.

I've been really surprised at the low number of cycles for the cheap Pb-Ca batteries- how is this figure arrived at?

If you have solar, self discharge isn't a problem whether on board or not.

70% discharge will knacker batteries quick time and 50% is the sensible bottom limit for Trojans. Life depends on number cycles and the smaller the discharge level, the longer they will last.

 

[TQA]

One of the key factors that make golf cart batteries a good buy for a liveaboard is their ability to tolerate the occasional deep discharge.

As for the higher self discharge rate leave a solar panel connected to provide a float charge.

 

[Bitterend]

Coincidentally, I just watched a you tube video from 'Sailing Emerald Steel'

https://www.youtube.com/watch?v=9H7a1Jz-Phc&t=616s

the couple have lived aboard for 30 years and are on their 4th set of batteries!!! It's a very interesting video about battery type and management.

 

[BobnLesley]

It depends how long you intend to keep the boat and how much you will use it. I went with Trojan 6 volt as they have a proven life span of over 15 years if treated well ...

Also where you are: Throughout or time in the Med we invariably went with cheap & cheerful 'leisure' batteries - usually managing 2-3 seasons, deeming the Trojans too expensive. When we reached the western side of the Atlantic we discovered that it's cheaper to buy Trojans (about £100 apiece in the US) there than Leisure batteries. Having changed to Trojans if we ever ended up back in the Med I'd probably now deem them worth the investment even at European prices; our original set were 5-years old and seemed perfect - they've since sailed to Norway - when we swapped them out in Panama ahead of the Pacific.

 

[overstag]

I just installed an "eye watering" Lithium battery from Mastervolt.. It is very expensive. But you get thousands of cycles out of them and you can discharge them very deeply. Zero maintenance. It is the last battery I'll ever have to buy and I like that idea. In the end, it is the cheapest battery by a big margin, because of the long lifespan. Sterling power did a very nice comparison test between lithium and various brands of AGM and wet batteries. Lithium won hands down. In the end they stopped the test, because all the batteries had died, but the Lithium didn't even show the slightest deterioration.
You can find the film on youtube.

 

[Kelpie]

I just installed an "eye watering" Lithium battery from Mastervolt.. It is very expensive. But you get thousands of cycles out of them and you can discharge them very deeply. Zero maintenance. It is the last battery I'll ever have to buy and I like that idea. In the end, it is the cheapest battery by a big margin, because of the long lifespan. Sterling power did a very nice comparison test between lithium and various brands of AGM and wet batteries. Lithium won hands down. In the end they stopped the test, because all the batteries had died, but the Lithium didn't even show the slightest deterioration.
You can find the film on youtube.

Thanks, I am intruiged by the lithium option but expect that I might run out of pennies.
I've been following Delos in their upgrade to lithium, and it is a very impressive performance increase- they say that their new bank takes up the same space as their old bank of eight lead acid batteries, but provides the equivalent of 24 batteries worth of usable power, and is half the weight. They have switched to induction cooking and happily use a kettle, toaster, and microwave, which would have been unthinkable before.

One of my worries about lithium is that if you do damage the bank somehow- e.g. faulty charger, or accidental short etc- then you are writing off several thousand pounds worth of batteries. With cheaper batteries, the risk is much lower.

Perhaps by the time I come to actually sail away (two or three years from now) the price of Lithium cells will have dropped sufficiently to make it more affordable.

 

[TQA]

Two questions for Lithium battery users.

1) What provisions do you have for balance charging your battery bank.

2) How would you deal with a battery fire.

View attachment 74768

 

[overstag]

1-BMS. Battery Management System. And use chargers that have a lithium program.
2-basically, you prevent it. Just like you prevent your diesel tank cathing fire, or your gas bottle. If any of these catch fire anyway, the best option is probably your liferaft..

 

[BobnLesley]

...Lithium battery...very expensive...It is the last battery I'll ever have to buy...(QUOTE]

I just love optimists, Good luck with it.