Realistic lead acid battery life expectancies?

john_morris_uk

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We have three 135 aH wet lead acid batteries to run the domestics on our boat which we live aboard full-time for five or six months of the year. They never discharged more than about 25% and they’re charged through several hundred watts of solar and a Victron MTTP controller. There’s also a super wind generator plus a small diesel generator that whenever it’s on is charging the batteries through a Sterling three stage battery charger. Then whenever the main engine is running, there’s a 100 amp alternator that confects to domestics via a VSR.

Power and voltage and aH used are monitored by a Sterling battery monitor. I never really worry about the state of the batteries as there’s so much charging potential and the sophisticated charging systems usually have them on float soon after any bulk charge is finished.

We can’t quite remember when we last replaced the batteries, but we think it’s at at least six years ago. However they’ve suddenly decided to stop holding charge and overnight the fridge turns itself off as battery voltage drops below 11.7 V. The change has been sudden and I’ve removed all the batteries and checked the voltage on them thinking perhaps a cell on one had gone short circuit and was dragging the whole bank down. But each battery was showing 12.5 or 12.7 V offload and I could see no damage or particular problem with any of the cells when I looked down into them. (I appreciate that’s not a very good test!)

I know that some people will be suggesting we change to lithium as it looks as though we’re going to have to buy new batteries but that’s really not practical as there’s too many charging systems involved that would all have to be changed and parts availability and costs make it an probitive task to do here in the Caribbean. Fortunately, we’re in Saint Martin at the moment where there are several very large Chandlers with good stocks of deep discharge batteries. It looks as though new AGM batteries are the way ahead. (Although prices are eye watering: list price for three AGM is over $2000)

Is it unreasonable to expect the batteries to last longer than six years also even though they’re treated (as far as I’m concerned) so Kindly? What’s a reasonable battery life expectancy?
 

Alex_Blackwood

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We have three 135 aH wet lead acid batteries to run the domestics on our boat which we live aboard full-time for five or six months of the year. They never discharged more than about 25% and they’re charged through several hundred watts of solar and a Victron MTTP controller. There’s also a super wind generator plus a small diesel generator that whenever it’s on is charging the batteries through a Sterling three stage battery charger. Then whenever the main engine is running, there’s a 100 amp alternator that confects to domestics via a VSR.

Power and voltage and aH used are monitored by a Sterling battery monitor. I never really worry about the state of the batteries as there’s so much charging potential and the sophisticated charging systems usually have them on float soon after any bulk charge is finished.

We can’t quite remember when we last replaced the batteries, but we think it’s at at least six years ago. However they’ve suddenly decided to stop holding charge and overnight the fridge turns itself off as battery voltage drops below 11.7 V. The change has been sudden and I’ve removed all the batteries and checked the voltage on them thinking perhaps a cell on one had gone short circuit and was dragging the whole bank down. But each battery was showing 12.5 or 12.7 V offload and I could see no damage or particular problem with any of the cells when I looked down into them. (I appreciate that’s not a very good test!)

I know that some people will be suggesting we change to lithium as it looks as though we’re going to have to buy new batteries but that’s really not practical as there’s too many charging systems involved that would all have to be changed and parts availability and costs make it an probitive task to do here in the Caribbean. Fortunately, we’re in Saint Martin at the moment where there are several very large Chandlers with good stocks of deep discharge batteries. It looks as though new AGM batteries are the way ahead. (Although prices are eye watering: list price for three AGM is over $2000)

Is it unreasonable to expect the batteries to last longer than six years also even though they’re treated (as far as I’m concerned) so Kindly? What’s a reasonable battery life expectancy?
It is difficult to put any specific figure on battery life, so many variables. However, as a ball park figure, if you are looking at a car battery an average of six years is about right. As you say you are in the Caribbean where the weather tends to be a tad warmer than UK. That can be detrimental to battery life:cry: All in all I wouldn't be too disappointed at six years. No doubt the theorists and experts will be along to tell you exactly what is what.:eek::ROFLMAO:
 

john_morris_uk

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Six years is a very good life for a liveaboard. I know many who replace after three years regardless. Mine failed recently after five years but they stood unused for a long time during lockdown.
Thanks for making me feel better. I was unrealistically thinking that because we look after the batteries with so much care and I’ve tried to engineer a charging system that doesn’t abuse them, I (perhaps foolishly) thought they’d last a lot longer.
Looks like we’ll just spend some more of the children’s inheritance on some new AGM’s….

We’ve now got the interesting problem of manoeuvring several 35 kg batteries around in a dinghy plus on and off the boat.
 

Graham376

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Thanks for making me feel better. I was unrealistically thinking that because we look after the batteries with so much care and I’ve tried to engineer a charging system that doesn’t abuse them, I (perhaps foolishly) thought they’d last a lot longer.
Looks like we’ll just spend some more of the children’s inheritance on some new AGM’s….

We’ve now got the interesting problem of manoeuvring several 35 kg batteries around in a dinghy plus on and off the boat.

On and off the boat into the dinghy shouldn't be too hard if you use the boom. We lifted engine out that way with some ply to rest it on.
 

Refueler

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Given your regime .... anything over 5yrs is good ....

Think of like your car .... rarely does a car battery drop below about 75% charged level ... its charged straight back up again when you drive ...

At 5 - 6 - 7 yrs its not unusual to then find that the battery can fail to start the car if left for a few days ... but all looks ok when you test voltage etc. The problem is the internal resistance / plates have deteriorated and no longer can the battery deliver the power ... the voltage drop is too great.

I've had batts last well over 7yrs ... but later batts I've had rarely last more than 4 - 5yrs ...
 

Sea Change

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There are few applications where a lead acid battery will still be performing well after seven years. Even in a car, where they live the most mollycoddled life possible, it's common to replace them around that age (especially modern cars with lots of voltage sensitive equipment).

I know you're ruling out lithium, but if you consider you might never have to replace them, and you will cut your generator running hours substantially, will they really be all that expensive? And your back will certainly thank you!
 

vyv_cox

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I have seen quoted 300 deep cycles lifetime for lead acid batteries.
May be 500 cycles if you treat them right.
I bought Winner Solar batteries that claimed 600 cycles. Unfortunately covid prevented long term testing.

I believe Winner are Europe wide. The batteries functioned perfectly before lockdown and even gave us a season after 3 years unused.
 

john_morris_uk

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There are few applications where a lead acid battery will still be performing well after seven years. Even in a car, where they live the most mollycoddled life possible, it's common to replace them around that age (especially modern cars with lots of voltage sensitive equipment).

I know you're ruling out lithium, but if you consider you might never have to replace them, and you will cut your generator running hours substantially, will they really be all that expensive? And your back will certainly thank you!
I’d really like lithium, but I’m not sure how the charging regimes of the Sterling 230v battery charger that we use off the generator or when we’re along side can cope? I’m also not sure how the wind generator which has its own regulator would manage? I’m really not clued up enough about lithium charging regimes to know what to do so perhaps I’m just shying away from the whole idea and taking the easier option.
 

Blueboatman

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I’d really like lithium, but I’m not sure how the charging regimes of the Sterling 230v battery charger that we use off the generator or when we’re along side can cope? I’m also not sure how the wind generator which has its own regulator would manage? I’m really not clued up enough about lithium charging regimes to know what to do so perhaps I’m just shying away from the whole idea and taking the easier option.
My only suggestion . If you’re still in St M and environs there must be a lot of knowledge, both ashore and amid the sailing community, about the realities of going lithium and dc dc charging..
 

RunAgroundHard

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... Is it unreasonable to expect the batteries to last longer than six years also even though they’re treated (as far as I’m concerned) so Kindly? What’s a reasonable battery life expectancy?

I get 7 years on T105s. First set were of an unknown quantity as they came with the boat and lasted me 4 years before failing by not retaining charge. I am on my second set at 6 years and still going strong. Usage is UK, WCofS all year round (fridge and auto helm biggest users), shore power when plugged in, usually, but not always, twin 24 alternators running through split charging, which are not very efficient.
 

Sea Change

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I’d really like lithium, but I’m not sure how the charging regimes of the Sterling 230v battery charger that we use off the generator or when we’re along side can cope? I’m also not sure how the wind generator which has its own regulator would manage? I’m really not clued up enough about lithium charging regimes to know what to do so perhaps I’m just shying away from the whole idea and taking the easier option.
The wind generator is unlikely to fit well with lithium. Ours just charges the engine battery, and when we eventually get around to fitting a DC-DC charger it will then be able to contribute to the lithium too. Tbh we usually have it on brake mode because of the noise. 'Silent' Wind my ****!

How old is the Sterling? Anything produced in the last few years is likely to have a lithium setting. And actually, even if it doesn't, you can still use it for bulk charging. It will eventually try to overcharge the lithium, whose BMS will prevent that from happening. Not an ideal long term system but not really a big problem either.

The bigger issue is alternator charging, where the BMS kicking in can and will damage your alternator. Easiest way around this is a DC-DC charger.

Swapping over to lithium is certainly not a five minute job, there is definitely a bit of commitment to do it properly. And it's easy to get stuck down a rabbit hole where you try to replicate the exact functionality you are used to with your previous system- like being able to charge rapidly from a variety of sources. This makes the conversion harder.

I've been fortunate in that my last couple of boats have had sufficient solar (1350w on the current one) that I simply don't have to worry about all these fancy charging sources- I just use the solar on its own. We cook entirely on electric, run a 200l fridge, and our batteries are back to 100% every day. Selling the generator paid for the solar panels 🙂
 

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"The bigger issue is alternator charging, where the BMS kicking in can and will damage your alternator"

mmmm usually alternators suffer damage from being switched OFF when engine running ... unless batts have reached near full charge and alternator regulator is near off itself ..
 

Supertramp

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The table below suggests that using a low depth of discharge (DOD) significantly extends lead acid battery life. It also suggests that after 6 years of 180 charging cycles a year you're probably reachng the limit.
Screenshot_20250121_141146_Chrome.jpg
Agree about the complexity of changing to Lithium - if lead acid works for you, stick with it.
 

Sea Change

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"The bigger issue is alternator charging, where the BMS kicking in can and will damage your alternator"

mmmm usually alternators suffer damage from being switched OFF when engine running ... unless batts have reached near full charge and alternator regulator is near off itself ..
'Kicking in' as in 'doing its job'.
The BMS determines that the cells have reached the high voltage cut-off point, and it stops accepting charge. Some sources dislike this more than others, and as you say alternators can be damaged when this happens.
(MPPTs can too, so you have to get your settings right).
 

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Because of the ease of Lead Acid installations and charging etc - I shall be fitting LA setups into two boats of mine that need sorting. They are small 5 - 6m river stuff - so nothing serious. But LA just works. That's a single 70 - 80 A/hr each.

My main sailboats .. 25ft and 38ft and my 234ft MoBo - all use Lead Acid ... and they shall continue to do so ... I need change the two domestics on the 38 ... one of the two on the 25 and maybe both in the mobo ... that's 2x 80 A/hr, 1x 90 A/hr and 1 or 2 90 A/hr
To ease the pain on my pocket - they shall be done in stages ... in fact I could probably use a couple of these in the two smaller boats as they don't need starter batterys ... only low power demand for plotter, depth / speed etc.
 

Refueler

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'Kicking in' as in 'doing its job'.
The BMS determines that the cells have reached the high voltage cut-off point, and it stops accepting charge. Some sources dislike this more than others, and as you say alternators can be damaged when this happens.
(MPPTs can too, so you have to get your settings right).

I know what BMS do ....

As I say ? Its often the switch OFF that does the damage.

With regard to Solar Controllers .... all the ones I have say they must have the battery connected BEFORE the solar panel .... and disconnected AFTER the panel ..
 

Sea Change

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Agree about the complexity of changing to Lithium - if lead acid works for you, stick with it.
At Caribbean prices, even a cheap lead acid starter battery can cost $200US. Importing lithium starts to look like a very sensible option at these sorts of prices. But yes, it's not always the simplest process to make the change.
 
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