Q re the physics and mechanics of a failing led acid battery.

[vas]

morning all,

yesterday went to help a friend bring his boat back to port from his summerhouse mooring couple of hours away. He did mention on the way that last week went there and nothing was working on checking out service batteries were at 17V (boat is a P45 and 24V) And that was with close to 700W of solar and two almost brand new 220Ah LA service batteries.
Surely when we arrived batteries was at 17V again, started the generator had it running for almost half an hour in order to get the batteries to almost 24 and the engines to fire up (with difficulty being V8 CATs), tried to turn gen off when underway and Victron BMV was reporting -20A (whereas was only reporting a measly 20A with gen running) and voltage was dropping quickly so left it on for the duration of the short anyway trip.
When safely moored in port brought my battery tester kit from my boat which is nearby and sure enough one of the two starting engine LA batteries was at 9V. Quickly disconnected the bridge from one to the other starter bank battery and unsurpisingly BMV started reporting 3+A with generator off and 45+A with gen on (wasn't particularly sunny). Quick check and one of the two solar banks was dead (but that's going to be dealt separately, pretty sure the mppt is dead). Left the gen running for another 2h while we went to eat coming back to it charging at 20A and battery bank stable at 25.something with gen running and 24.something with gen off. He's going to visit the boat again today and charge it more, but looks like the batteries are recovering (how well, we'll probably know next season!)
it's obvious the two banks (starter service) are permanently linked on this boat (by some idiot that worked on the electrics and fitted a OFF/1/2/BOTH stupid thing). Was worried and didn't touch it (was in OFF position btw which I'm not sure what it might mean...), will remove it during the winter and will try to restore the cabling (hope @PaulRainbow will help). If I now (with service bank open circuit) I toggle the el.panel Vmeter it will show 24.something on either service or starter bank...

The point of this post is to ask what is the failing process of a sealed LA battery. I assume that's shorted hence the 9V, does it slowly drop from being at 13.something fully charged to 12, 11, 10, 9 or does it go bang 12.5 to 9 in a day or so? Mind no sulfur smell or anything odd in the battery area
Trying to figure out if his complaining after his midAugust week long trip to the nearby islands that system wasn't holding charge that well is related to that or to the probably already failed solar subsystem. No shorepower where he had it moored over the last couple of months.

cheers

V.

 

[rafiki_]

morning all,

yesterday went to help a friend bring his boat back to port from his summerhouse mooring couple of hours away. He did mention on the way that last week went there and nothing was working on checking out service batteries were at 17V (boat is a P45 and 24V) And that was with close to 700W of solar and two almost brand new 220Ah LA service batteries.
Surely when we arrived batteries was at 17V again, started the generator had it running for almost half an hour in order to get the batteries to almost 24 and the engines to fire up (with difficulty being V8 CATs), tried to turn gen off when underway and Victron BMV was reporting -20A (whereas was only reporting a measly 20A with gen running) and voltage was dropping quickly so left it on for the duration of the short anyway trip.
When safely moored in port brought my battery tester kit from my boat which is nearby and sure enough one of the two starting engine LA batteries was at 9V. Quickly disconnected the bridge from one to the other starter bank battery and unsurpisingly BMV started reporting 3+A with generator off and 45+A with gen on (wasn't particularly sunny). Quick check and one of the two solar banks was dead (but that's going to be dealt separately, pretty sure the mppt is dead). Left the gen running for another 2h while we went to eat coming back to it charging at 20A and battery bank stable at 25.something with gen running and 24.something with gen off. He's going to visit the boat again today and charge it more, but looks like the batteries are recovering (how well, we'll probably know next season!)
it's obvious the two banks (starter service) are permanently linked on this boat (by some idiot that worked on the electrics and fitted a OFF/1/2/BOTH stupid thing). Was worried and didn't touch it (was in OFF position btw which I'm not sure what it might mean...), will remove it during the winter and will try to restore the cabling (hope @PaulRainbow will help). If I now (with service bank open circuit) I toggle the el.panel Vmeter it will show 24.something on either service or starter bank...

The point of this post is to ask what is the failing process of a sealed LA battery. I assume that's shorted hence the 9V, does it slowly drop from being at 13.something fully charged to 12, 11, 10, 9 or does it go bang 12.5 to 9 in a day or so? Mind no sulfur smell or anything odd in the battery area
Trying to figure out if his complaining after his midAugust week long trip to the nearby islands that system wasn't holding charge that well is related to that or to the probably already failed solar subsystem. No shorepower where he had it moored over the last couple of months.

cheers

V.

Vas, others will give you a better reply than me, but this is my experience on my Azi 39. I had left the boat with the shore power off for a week, but the fridge on. There were 2 12v service LA batteries. We took the boat from her home berth, Portishead, to Penrith. About 90 mins. Moored up, shore power on. All appeared ok. Woke up in the morning to an awful smell all over the boat. Tracked this down to one of the service batteries, which was very hot, probably not far from thermal runaway. Switched everything off, and eventually the battery cooled, so I disconnect from the service circuit, leaving the other battery in place. Enjoyed the weekend and returned to Portishead on the Sunday. I purchased 2 new LA batteries and changed them both. As you know, once the voltage drops below 11.5 ish, the plates start to build a coat of sulphur, which bridges the gap to the next plate and shorts out.

 

[vas]

P, thanks, I've got the smell and the busted LA battery t-shirt already on MiToS rebuilt

this is different though, no smell, nothing left on (apparently) so curious how a short develops...
having said that, he called me an hour ago having visited the boat (charge/voltage fine apparently) but he did mention that one of the three bilge pumps was constantly on (he'd turned it off last week, I turned it back to auto yesterday that I noticed) Possibly that's related and helped the already tired starter bank to go too low and self destruct/short.
we shall see...

V.

 

[vas]

small update, went by, to pick something from my boat, he was there so I checked again the starter batteries, now showing 6 and 8V respectively, so both dead, service ones seem to have survived with gen off where 25.4V with 3A solar going in.
He did use the geny for one hour, started with 20A and dropped to 9A when he turned it off. No shore power on our dock obvs.

 

[Refueler]

Deterioration of battery surely depends on what you do with it - the use etc.

If you try to start an engine with a true deep discharge leisure battery - the plates will often buckle due to the excessive load put on it ... giving a quick death ! (I know some will argue that - but they will quote 'their' leisure battery - which will be a compromise battery designed for RV life).
Overcharging any battery can cause decline over a relatively short time if not sorted ...
Overdischarging a battery - cranking LA should not really be brought down to 50% too often .. if done - get it charged up as soon as possible .. deep cycle can go to 50% more often ... but still being LA - it is not recc'd too often.

Sulfation of plates is a time based matter ... that often occurs with batterys that have a sedate life !! Because they are not subjected to bursts of high demand .. or high charge .. the plates start to get coated. This is where the De-Sulfation units are supposed to operate and help cure ... they do if you catch it early enough - but as soon as the battery is observed as reduced capability - the unit will usually fail to recover the battery.

Allowing a LA to be stay discharged in freezing conditions can lead to battery failure ... always charge fully if it will stand in winter. In fact a LA battery should be charged fully if going to left to stand ...

The essence of all this ? Lead Acid batterys are designed to be worked ... they are not designed as standby - do nothing batterys - despite we often make them do just that ! But that work is to be within the design parameters of the specific battery ...

Many of us - myself incl - put a cranking batterys into a boat and expect them to a) start the engine .. b) run the domestics .. whether via 1-off-2- both switch or via later VSR / switched banks .. In doing that - we must pay regard to how to maintain the batterys above the 50% mark and to ensure that 50% only occurs rarely ..

How long should batterys last on board ? Really its a 'how long is a piece of string' question ...

I have had 2nd hand breakers yard batterys last 5 - 6 - 7 yrs ... I've had new batts last 2 - 3 yrs on the same boat ! It all comes down to how they are used / abused.

I've just removed one of my good domestic batterys from my 38 - to replace the 4yr old #2 battery on my 25 that has given up ... Why ? Its been on the auto charger for about last 2yrs while boat repaired ... it has not been 'exercised' .... all it did whejn trying to start my engine was sause the starter solenoid to go CLICK CLICK CLICK ...

I realise that I will probably be challenged on some or even all of above - but its my observation and experience over more than 50yrs of boats ... and I freely admit - I still haven't solved the puzzle of how to really create long life of batterys given the abuse we dish out to them !

 

[Refueler]

P, thanks, I've got the smell and the busted LA battery t-shirt already on MiToS rebuilt

this is different though, no smell, nothing left on (apparently) so curious how a short develops...
having said that, he called me an hour ago having visited the boat (charge/voltage fine apparently) but he did mention that one of the three bilge pumps was constantly on (he'd turned it off last week, I turned it back to auto yesterday that I noticed) Possibly that's related and helped the already tired starter bank to go too low and self destruct/short.
we shall see...

V.

Auto bilge pump ..... mmmm I also have the T shirt on that one !

I have killed a couple of batterys with that !! Unless there is a reasonable regime of charging to the batterys - that auto pump can over time kill any battery. Very few have any built in cut-off to protect battery and maintain at least engine starting capabilty.

 

[vas]

tbh, with electrics on a boat, you either have a decent 1m interval monitoring able to pinpoint potential problems (and email/sms/whatever you), or you are playing some sort of roulette by turning off subsystems that MAY kill your batteries, but MAY also keep your boat afloat.
I'm on on the 30s monitoring of way too many parameters (all going on a DB at my office computer via a 4G Teltonika router onboard, but I can now sleep relaxed at night even though boat is 6min walk from home.
Needless to say it's not a proper marina, just Volos port open to anyone, no support no marineros, nothing.

Re my mate, a solar panel cable connector was broken, technician replaced it, all solar working, quite sunny today, midday service bank was at 27.3V or thereabouts charging at 7A.
Will leave them till the w/e on this diet and then we'll start turning on fridges and see how system behaves, got two (and a third on inverter) to play with

cheers

V.