Realistic lead acid battery life expectancies?

[john_morris_uk]

I’ve just been quoted $680 for a 125aH AGM battery.

 

[Plum]

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?

I don't work my batteries very hard, standard flooded lead acid type, and usually get 8 years.

 

[Sea Change]

I’ve just been quoted $680 for a 125aH AGM battery.

Just FYI, last summer in Grenada I imported the components for a 280Ah lithium battery (equivalent useable capacity to around four of those AGMs) for $550.
Prices have fallen since then too...

 

[Goldie]

I too, am in a similar scenario to the OP - 5 or 6 months live aboard, wind, solar, big alternator etc. and my domestic bank has just died a couple of months short of its 10th birthday. FWIW, those 4 batteries were ‘Intimidator’ AGMs fitted in the Caribbean. They’ve given excellent service!

 

[westernman]

For a reference point, the lead acid 12V battery in our Toyota Yaris Hybrid which is now about 5 years old has just failed and had to be replaced.
I am guessing that these batteries are much more stressed in a hybrid with numerous starts.

 

[ctva]

I replaced our three domestic LA batteries last year at 7 years old with lithium. Surprised to find the single LA engine one was 12yo and still working fine on a Yanmar 3GM.

 

[Tranona]

I replaced our three domestic LA batteries last year at 7 years old with lithium. Surprised to find the single LA engine one was 12yo and still working fine on a Yanmar 3GM.

That is quite normal if you look after your batteries. In typical UK leisure use you maybe do 50-60 cycles a year. Good FLA batteries suggest cycle life in the 3-500, so 5-10 years, AGMs generally 50% greater. engine start batteries have an easy life. My Morgan which leads a similar life to a yacht start battery - short periods of intensive use followed by long periods of no use lasted 19 years. It was a Red Flash AGM and I use a trickle charger when it is not used for more than a couple of weeks.

The OP is a 50% liveaboard with heavy demands so has done well with his current batteries.

 

[Frank Holden]

I think 6 years is reasonable. I have had good results out of flooded Trojans. Poor results from AC Delco sealed lead acids on several occasions. Had to buy new batts in Valdivia in late 19.
2020 to mid 2022 laid up ashore on solar through a Victron MTTP. 2 batteries toast after less than 3 years.
Now coming up to 3 years on Ecuadorian manufactured Bosch SLAs - US$500 each - ouch.
They better last .......

 

[NBs]

Hi,
My boat has three separate battery banks with Life Line AGM batteries installed first.

2*start batteries died after 10 years of use.

I replaced the house bank last spring, they didn't die, but I decided to replace them with Lifepo4 batteries, they lasted 15 years.

I still have the original batteries in the bow prop/anchor winch bank and they are still good. Life Line is good brand, but Expensive to acquire.

Looks like I will have to replace the starter batteries again, the exide dual didn't give, like 6 years.

NBs

 

[john_morris_uk]

An update. One of the house batteries in under a bunk and close to the Sterling 50 amp 230v charger. I noticed that it was VERY warm and disconnected it leaving two batteries running the fridge, anchor light, cabin fans etc overnight. I woke this morning to find an extremely healthy pair of batteries with 12.6 volts showing.

 

[Cardinal]

An update. One of the house batteries in under a bunk and close to the Sterling 50 amp 230v charger. I noticed that it was VERY warm and disconnected it leaving two batteries running the fridge, anchor light, cabin fans etc overnight. I woke this morning to find an extremely healthy pair of batteries with 12.6 volts showing.

So you will replace the duff one with a smaller one giving room for insulation and/or ventilation!

 

[Sea Change]

So you will replace the duff one with a smaller one giving room for insulation and/or ventilation!

If it were me, and knowing John's plans, I would wait until I reached the States and buy a replacement at a more sensible price.

(Well actually I would never buy another lead acid house bank for a liveaboard boat, I'm not wealthy enough)

 

[john_morris_uk]

If it were me, and knowing John's plans, I would wait until I reached the States and buy a replacement at a more sensible price.

(Well actually I would never buy another lead acid house bank for a liveaboard boat, I'm not wealthy enough)

We’re looking at two or three options. One is to update to lithium FePo4 but importing everything from the USA to Sint Maarten. Most costly and a probable two week wait for the parts. Second is to change batteries to Lead Carbon which are available here but at $480 each. Third would be to do a straight swap to new wet lead acid again available locally at a price. Cheapest but doesn’t solve the problems with the charger heat damaging the battery adjacent to it.

I’m l also looking at adding ventilation to the underbunk area where the charger is located or fitting a new charger in a better place.

 

[vyv_cox]

We’re looking at two or three options. One is to update to lithium FePo4 but importing everything from the USA to Sint Maarten. Most costly and a probable two week wait for the parts. Second is to change batteries to Lead Carbon which are available here but at $480 each. Third would be to do a straight swap to new wet lead acid again available locally at a price. Cheapest but doesn’t solve the problems with the charger heat damaging the battery adjacent to it.

I’m l also looking at adding ventilation to the underbunk area where the charger is located or fitting a new charger in a better place.

Not sure about the heat damaging the battery. It would need to be at a considerable temperature for long periods. My Red Flash starter battery is right alongside the gearbox in the tunnel, very confined space where I imagine it gets pretty warm. The battery is just about surviving, on its last legs but 10 years old.

 

[davethedog]

We had a similar problem on our previous boat (we had 3 x 140ah AGM batteries on that} and we discovered that one of the batteries had failed and caused the whole system to not hold charge well at all. After we removed the defective battery from the system it was fine, though of course with a reduced capacity.

 

[Pete7]

John, we have had LFP for 3 years and I am really pleased with it, but don't push it if someone isn't ready for a change. However, in your circumstances think worthwhle.

You had 405Ah Lead acid when new. You now have considerably less. 300Ah of LFP will probably fit your need and mean only one LFP battery. Now lets look at the charging methods because that is were you are not convinced.

1. You have a Victron MPPT, presumably with the latest software it has a LFP setting or a custom setting were you can set your own parameters? Solved.

2. You have a wind mill but don't use it often. Wire it to the engine start battery and then buy a single Victron 50A DC>DC charger to the LFP.

3. You have a 50A sterling 240v charger. Wire this to the engine start battery and use the new Victron D>DC charger for charging the LFP.

4. Engine alternator, you haven't given us any details but how about put this on the engine start battery and use the DC>DC as well.

Some thoughts. You only need one LFP battery which makes things simple. You will need cables, lugs and a new fuse box to connect this all together and a single large fuse for the battery just in case. Probably Class T given your location. Buy a couple of spare fuses. Some switches. The Sterling battery monitor can stay and help to give you confirmation what the BMS Bluetooth app is telling you. Ours does.

You won't have to fully charge ever again. A couple of hours to put a good whack into the LFP will do, then turn off the generator and go out. So what if its only 80%, that will do.

Start by pricing it up and compare to say 3 lots of lead acid batteries and the hassle of changing them.

 

[Sea Change]

John, we have had LFP for 3 years and I am really pleased with it, but don't push it if someone isn't ready for a change. However, I do think in your circumstances think worthwhle.

You had 405Ah Lead acid when new. You now have considerably less. 300Ah of LFP will probably fit your need and mean only one LFP battery. Now lets look at the charging methods because that is were you are not convinced.

1. You have a Victron MPPT, presumably with the latest software it has a LFP setting or a custom setting were you can set your own parameters? Solved.

2. You have a wind mill but don't use it often. Wire it to the engine start battery and then buy a single Victron 50A DC>DC charger to the LFP.

3. You have a 50A sterling 240v charger. Wire this to the engine start battery and use the new Victron D>DC charger for charging the LFP.

4. Engine alternator, you haven't given us any details but how about put this on the engine start battery and use the DC>DC as well.

Some thoughts. You only need one LFP battery which makes things simple. You will need cables, lugs and a new fuse box to connect this all together and a single large fuse for the battery just in case. Probably Class T given your location. Buy a couple of spare fuses. Some switches. The Sterling battery monitor can stay and help to give you confirmation what the BMS Bluetooth app is telling you. Ours does.

You won't have to fully charge ever again. A couple of hours to put a good whack into the LFP will do, then turn off the generator and go out. So what if its only 80%, that will do.

Start by pricing it up and compare to say 3 lots of lead acid batteries and the hassel of changing them.

Agree with all of the above.
There is no longer much of an argument for lead acid on cost alone.