Batteries - dead or just resting

[Twister_Ken]

Just returned to my boat after 18 months of lockdown and various other misadventures. Batteries flat. On investigation, seems there's a fault in the shore power lead - power is going at the shore end, but not coming out at the boat end. Are the batteries totally shot, or will they recharge with the right regime?

Thx for any advice.

 

[Rappey]

There is one way to find out ! Are they zero volts?
I would imagine if they have been flat for a long period then they will be scrap but no harm trying one to see what happens.
I had a 10.4v starter battery. Not sure why it went flat as it's got solar.
Ran the engine for an hour and it looked ok.
Turned the engine off and right before my eyes I watched the voltage go down to 10 again.

 

[LadyInBed]

Hi Ken, long time no hear!
How many batteries?
If more than one, are they isolated (diode/vsr) from one another?
If you haven't sorted out your mains issue, then take them/it home and recharge, then suck it and see!

 

[pandos]

If it is any consolation I have agms that are 15 years old now. Were totally flat for periods of more than a year several times. (Boat not used for 2 periods of 5 years)

Including this year when the solar panel did some thing strange.

I charged them up at Christmas and still holding the charge ...despite using lights and the radio frequently whilst I am on board and the standbye current for the gas alarm..

Much will depend on the batteries themselves...I found that a modern charger was not able to bring the completely flat batteries back to life so I used an old caravan charger...at home...(the one on the boat was fine for 11v ...)

 

[TiggerToo]

nice to see you back!
good luck with the batteries. Let us know how it goes

 

[Refueler]

You will need an old 'non-smart' charger to have any chance of results.

Smart charger will default out as voltage will be below its minimum value. So drag out Grandpa's old dumb charger and put that on ... leave it for a good while .... don't keep stopping and starting ... make sure fluid is topped up etc.

Wish you luck - but likelihood is scrap.

 

[parbuckle]

You will need an old 'non-smart' charger to have any chance of results.

Smart charger will default out as voltage will be below its minimum value. So drag out Grandpa's old dumb charger and put that on ... leave it for a good while .... don't keep stopping and starting ... make sure fluid is topped up etc.

Wish you luck - but likelihood is scrap.

Another method of kickstarting a charger when your battery is dead just rig it in parallel to a good battery with jumper leads for short while to get some juice in it maybe turn off before disconnecting avoid sparking

 

[bedouin]

You will need an old 'non-smart' charger to have any chance of results.

Smart charger will default out as voltage will be below its minimum value. So drag out Grandpa's old dumb charger and put that on ... leave it for a good while .... don't keep stopping and starting ... make sure fluid is topped up etc.

Wish you luck - but likelihood is scrap.

Some battery chargers, such as the Cetek one I use, have modes specifically designed to rescue dead batteries. I have not had to use that myself but from reports I have read they can sometimes bring batteries from the dead.

I am surprised they are totally flat even after leaving for 18 months was there some load on them?

I have left batteries that long on a couple of occasions and they have still had a reasonable charge in afterwards and have been fine to use.

 

[Twister_Ken]

Just returned to my boat after 18 moths of lockdown and various other misadventures. Batteries flat. On investigation, seems there's a fault in the shore power lead - power is going at the shore end, but not coming out at the boat end. Are the batteries totally shot, or will they recharge with the right regime?

Thx for any advice.

Some battery chargers, such as the Cetek one I use, have modes specifically designed to rescue dead batteries. I have not had to use that myself but from reports I have read they can sometimes bring batteries from the dead.

I am surprised they are totally flat even after leaving for 18 months was there some load on them?

I have left batteries that long on a couple of occasions and they have still had a reasonable charge in afterwards and have been fine to use.

The only load was the bilge pump circuit which is rigged outside of the main switched circuits. But I don't think the pumps will have kicked in, the bilge is bone dry.

 

[bedouin]

The only load was the bilge pump circuit which is rigged outside of the main switched circuits. But I don't think the pumps will have kicked in, the bilge is bone dry.

Have you measured the voltage? How flat is flat?

 

[Refueler]

Another method of kickstarting a charger when your battery is dead just rig it in parallel to a good battery with jumper leads for short while to get some juice in it maybe turn off before disconnecting avoid sparking

I suggest NOT to do this ... if the dead battery has shorted plates or damage internally - the current flow could damage the good battery ....
I would only think this ok - if the ailing battery showed moderate life of at least 9v or more.

 

[Rafiki]

Just returned to my boat after 18 months of lockdown and various other misadventures. Batteries flat. On investigation, seems there's a fault in the shore power lead - power is going at the shore end, but not coming out at the boat end. Are the batteries totally shot, or will they recharge with the right regime?

Thx for any advice.

Happened to me over this last winter. The small drain from the Navtex and radio reduced two house batteries to totally flat, reading 0.7v on battery meter. Re-charged them over a week or so and they now seem perfectly good, holding charge well. However they were brand new last September!

 

[capnsensible]

Gawd knows how many batteries I've changed on various boats over the years. Very rarely have been able to do a Lazarus.

Mostly, once gone they are.....gone and any respite normally turns out to be temporary.

Have tried lots of smarty chargers too. Cetek , as previously mentioned, has given best result.

Good luck!

 

[Twister_Ken]

Sad to report they are deceased. Fallen off the twig. Gone to meet their maker. Ex. Pushing up the daisies. In Boot Hill.

Ah well, it's only money.

 

[Norman_E]

Dead or just resting?

 

[thinwater]

A one-time draw-down certainly did not do them any favors, but it is different from an older battery that went flat. from years of use or years of undercharging.

My expereince is that it will take numerous charging cycles over a few months, and the battery will still have lost some capacity. Try it, with the understanding that it will take time and the battery has lost some capacity. The primary indicator of (relative) success is that the charged voltage is full (>13) and that it will stay about 12.5 for some time with a light load. If it does not come all the way up (voltage) within 3 cycles, it's toast.