Identifying a dud battery

[JumbleDuck]

Hello, folks.

My house bank died today. It's 2 x 60Ah (all that will fit) Varta lead acid, ten years old. Yes, I know, should have replaced them ages ago and will do so asap but ... I'm at Ulva Ferry, a long way from suppliers. If possible I'd like to continue until I am in easy reach of one of Tayna's couriers, and with care one battery will be fine.

There is a noticeable difference between the two batteries. With the engine running and the batteries linked the forward one is taking 11A and the aft one 3A. On a small mains charger, 3.3A fore and 0.5A aft. With the batteries unlinked, either separately takes 3.8A from the charger.

So ... is the battery taking the much higher charging current when they are linked the dud (perhaps because it is less charged) or is the battery taking the much lower charging current when they are linked the dud (perhaps because it has a higher internal resistance)?

If further tests are needed I have ... a standard multimeter, a clamp on DC ammeter, a 3.8A battery charger (Lidl!) and an electric outboard which draws ~30A from a well charged battery. Getting the batteries to the outboard with prop immersed would be fiddly but perfectly possible.

For now I have the aft battery on charge, but only because I am more suspicious about the amp hungriness of the other.

Advice and informed opinions would be very welcome.

 

[Tranona]

Knew you would be back once you had a problem! Can't help except to say chuck 'em and get decent batteries and live on the oil lamps, sounding lead, bit of wood over the side fir speed and a head torch for bedtime reading until the new ones arrive.

 

[JumbleDuck]

Luckily we have oil lamps, a Seafarer whirly with fresh PP9 (the old B&G is playing up), a handheld VHF, a handheld GPS and a 36Ah AGM for the outboard which can be charged from the engine and then used to charge USB things, so it's not quite the dark ages.

And I did post my improvements to the Nanni N2.14 exhaust elbow a while back!

 

[LadyInBed]

I did a battery check on my 3x110 ah bank the other week.
Disconnected 2 of them, charged the other by solar (2x80w), switched off solar, noted voltage then timed how long it took to discharge to 12.5v whilst running fridge constantly (on thermostat) and tv in the evening, plus a bit of led light.
Then repeated the process for the other two in turn.
They all performed about the same, within my expectations.

 

[William_H]

A battery is dead when it won't do the job you ask of it. So presumably deep cycle batteries. Isolate them from one another. Check voltage after standing for a bit. Use one with a load of some sort. Lights fridge etc. Observe voltage of battery after a while. Then connect up and do the same to the other battery. Voltage after some discharge will make it obvious if one or both batteries are dead. Use the best then if necessary use the other for domestic loads until such time as you replace one or both. Perhaps the charge current observed does not signify very much. Go for capacity test. ol'will

 

[sailaboutvic]

Welcome back JĎ all need a break from this place at times .
I found à quick check is to separate the batteries çharge both fully and leave over night , if there a drop then just replace it .

 

[RAI]

If they are wet cell batteries, a cheap hydrometer tells all. Usually one cell dies killing the battery.

 

[JumbleDuck]

Thanks, people. Unfortunately my hygrometer is 200 miles away and is have to find a way into the batteries to use it - I presume there are lids which come off.

Morning update: Having had 5 minutes of charging on the engine @ 11A and an hour on the charger @ 3A, then resting overnight, the forward battery is sitting at 12.7V. The aft battery had the charger to itself for ten hours and was showing as full on the charger display. It is reading 13.16V, though it only came off charge half an hour ago and hasn't had time to settle.

Plan A is therefore to charge the forward one today, if I can, then give them both a bit of a workout. Maybe try starting the engine a few times with each, with lots of glow plug.

Plan B is to do something cleverer if anyone can suggest something cleverer.

And Plan A-or-B is to call Tayna when they open and find out when they can get a pair of nice new batteries to Mull.

It's grey, windy and rainy. An excellent day to be tinkering at a friendly pontoon.

 

[VicS]

Thanks, people. Unfortunately my hygrometer is 200 miles away and is have to find a way into the batteries to use it - I presume there are lids which come off.
Morning update: Having had 5 minutes of charging on the engine @ 11A and an hour on the charger @ 3A, then resting overnight, the forward battery is sitting at 12.7V. The aft battery had the charger to itself for ten hours and was showing as full on the charger display. It is reading 13.16V, though it only came off charge half an hour ago and hasn't had time to settle.
Plan A is therefore to charge the forward one today, if I can, then give them both a bit of a workout. Maybe try starting the engine a few times with each, with lots of glow plug.
Plan B is to do something cleverer if anyone can suggest something cleverer.
And Plan A-or-B is to call Tayna when they open and find out when they can get a pair of nice new batteries to Mull.
It's grey, windy and rainy. An excellent day to be tinkering at a friendly pontoon.

12 7volts after siting overnight is encouraging . provided it
(a) holds its charge,
and
(b) can start the engine , assuming it is cabled adequately to do so.

13.1V immediately after coming off charge is difficult to judge. It may not be fully charged . Check it again after 12 hours. Aim to charge it to a point where it reads 12.7 ish after resting. Then provided it holds a charge and can start the engine there's a bit more life in it.

Your Lidl battery charger is too small. I have one but use it only for long term maintenance charging. If yours is the same as mine it drops down to 0.8 amps when the battery is about 75% charged ( when it gets up to 14.1 volts ) so it takes a long time to get up to full charge . Then it drops to 50mA float . There is a voltage,- which only a good new battery will get to, where it shuts off completely but I forget what it is

BTW, for the second time in 5 or so years its a hydrometer. (A hygrometer measures humidity)

 

[RAI]

A hydrometer for car batteries (not beer) cost very little and Amazon can deliver. Maybe you could borrow one from the proper yachtie next door. Sealed lead acid batteries can be opened easily and topped up with de mineralised water. You my be too late and one cell has dried and died. So regard batteries as consumable and buy a couple of new ones, plus a hydrometer.

 

[sarabande]

I am not sure that hammering a battery with engine starting and glow plug is as good a test as leaving lights on for a few hours, especially as engine starting and domestic use really need different types of batteries. Have you got the Varta type numbers ? Any VSR or 121 switches, or pernanently connected services such as bilge pump/VHF which may be bringing down one of the batteries, which do seem to be a bit on the small side.. Checking the asymmetric charge and residual figures as you are doing is the way forward.

 

[JumbleDuck]

12 7volts after siting overnight is encouraging . provided it
(a) holds its charge,
and
(b) can start the engine , assuming it is cabled adequately to do so.

Thanks Vic. It has good beefy cables, so wehn the other one is charged I'll get weaving with some tests.

13.1V immediately after coming off charge is difficult to judge. It may not be fully charged . Check it again after 12 hours. Aim to charge it to a point where it reads 12.7 ish after resting. Then provided it holds a charge and can start the engine there's a bit more life in it.

Alas I forgot to disconnect the solar charger, so it hasn't rested properly. Yet. The 13.1V was during an early morning rainstorm, so no solar then.

Your Lidl battery charger is too small. I have one but use it only for long term maintenance charging. If yours is the same as mine it drops down to 0.8 amps when the battery is about 75% charged ( when it gets up to 14.1 volts ) so it takes a long time to get up to full charge . Then it drops to 50mA float . There is a voltage,- which only a good new battery will get to, where it shuts off completely but I forget what it is

I have mine for the same reason. Between solar (100W) and engine the batteries normally stay charged without human intervention - I think this is only the second time in ten years that I have charged them from mains. Somewhere I have a 10A Mastervolt charger waiting to go in, but even now that can probably wait until I start using the boat outside the summer.

BTW, for the second time in 5 or so years its a hydrometer. (A hygrometer measures humidity)

D'oh. I am duly abashed and chastised.

 

[JumbleDuck]

A hydrometer for car batteries (not beer) cost very little and Amazon can deliver. Maybe you could borrow one from the proper yachtie next door. Sealed lead acid batteries can be opened easily and topped up with de mineralised water. You my be too late and one cell has dried and died. So regard batteries as consumable and buy a couple of new ones, plus a hydrometer.

New batteries from Tayna arriving at Tobermory Harbour Association offices on Wednesday, with luck, so as long as we can stagger on till then we're fine. Happily, we were planning to be in Tobermory next Thursday for the Highland Games.

 

[VicS]

New batteries from Tayna arriving at Tobermory Harbour Association offices on Wednesday, with luck, so as long as we can stagger on till then we're fine. Happily, we were planning to be in Tobermory next Thursday for the Highland Games.

You'll have your new batteries before you can fully assess the health of the existing ones without specialised equipment.

 

[JumbleDuck]

I am not sure that hammering a battery with engine starting and glow plug is as good a test as leaving lights on for a few hours, especially as engine starting and domestic use really need different types of batteries. Have you got the Varta type numbers ? Any VSR or 121 switches, or pernanently connected services such as bilge pump/VHF which may be bringing down one of the batteries, which do seem to be a bit on the small side.. Checking the asymmetric charge and residual figures as you are doing is the way forward.

And thanks to you too. The two batteries live permanently coupled, so anything which brings down one brings down the other. Which is why the charging asymmetry puzzles me. Unfortunately, for testing purposes, I have very little which draws much current. Ever light on the boat (bar the fluorescent tube over the galley and the compass bulb) is LED, so about the worst I can do to them is to put on the B&G instruments (2A) and take a full 4A out of the dual USB charger.

With new batteries ordered and on their way soon, my interest at the moment is in finding out which, if either, of the existing batteries I can keep in use for another five days.

Too small? Yes, definitely. Absolutely fine for summer sailing, but even then three cloudy days in a row without running the engine can deplete them and definitely not enough for the off-season sailing I plan when I retire (one year, ten months, three weeks, four days - but who's counting?) However, I have a moulded battery tray which constrains the length and width and it's in a shallow locker under my bunk, which means that I can only fit 190mm high batteries. The Big Idea is therefore to go lithium in due course - what are lump sums for? - but that will have to wait, because although I could get 2 x 100Ah in there, the thick end of a grand makes the prospect rather painful.

Still, I coped for years with a 40Ah car battery in my last boat (no engine) so the prospect of a few days on reduced power ain't too bad. Where Ido kick myself is in allowing the batteries to get so old. Ithough Iput them in 5 years ago and it was only when Ichecked my Tayna order history for the type that Irealised they went in in 2012. If Ihad realised that I would have replaced them before setting off.

 

[JumbleDuck]

You'll have your new batteries before you can fully assess the health of the existing ones without specialised equipment.

Yup. However, I am confident that my present ones are knackered - it's just a matter now of finding out whether one is a bit less knackered than the other. I shall be interested to see how long they last at Tobermory harbour skip - the place from which, as I am sure I wrote once, 3m of toilet outlet hose, reduced to 10mm internal diameter by impacted erm, waste matter, was swiped within ten minutes of me depositing it.

 

[Stemar]

3m of toilet outlet hose, reduced to 10mm internal diameter by impacted erm, waste matter, was swiped recycled within ten minutes of me depositing it.

Surely, that's what marina skips are for? I've had a few good bits from them, and left others in the hope that someone else can benefit from stuff the Admiral has told me I don't need.

 

[JumbleDuck]

Surely, that's what marina skips are for? I've had a few good bits from them, and left others in the hope that someone else can benefit from stuff the Admiral has told me I don't need.

I wish nothing but good to the new owner of my hose and I we ever meet I shall shake them warmly by the ... well, maybe not.

 

[Momac]

The two batteries live permanently coupled, so anything which brings down one brings down the other. Which is why the charging asymmetry puzzles me.

I have known exactly that to happen with no explanation.

 

[JumbleDuck]

I have known exactly that to happen with no explanation.

Thanks. Perhaps it's just demonic possession.

Having had a nice walk on Ulva and come back to find the forward battery fully charged, according to the charger, I have done a test. Each battery in turn was given full responsibility for everything, then asked to heat the glow plugs for 20s and start the engine.

Not much difference.. Both happily supplied the 20A needed, falling to 12.66V (aft) and 12.62V (forward) as they did so. I have left forward battery disconnected and am using the aft to charge my tablet and a phone with the gallery fluorescent tube and instruments on. Solar charger running, because this is to find out if using that battery is a viable proposition.

Oddly, the multimeter tells me that the battery is at 12.8V, both at its terminals and at the PV regulator, but the regulator remote display says 12.5V. Some attention needed there too. The regulator is brand new from Photonic Universe.