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Normanby 13-09-2013 23:49

Are my batteries knackered?
Please forgive the newbie question, and i have had a search through CF and I'm still clueless.

Are my batteries dead or am i just not using the charger or the switch right?

My new/old boat has two batteries and one of those off/1/both/2 switches. One battery looks to be 100ah AGM, the other is 60ah and has water in it (i can see it through the little round window).

There was no power when i took delivery of the boat and we had to start the motor with another battery.

I left the batteries on charge using my C-Tek charger (which i know how to use, 'coz i read the manual this time!) for four days.

When i returned to the boat the C-Tek charger still had the "charging" light on, not the "charged" light. I disconnected it, turned the switch to "both" put the key in, turned it and pressed start button.

The starter motor turned the Yanmar over a couple of times, it nearly caught, then gave up.

Measuring the voltage with my meter the answer came back at 8.5 volts.

So i guess that means the batteries are knackered.


Could i have tried to charge them wrong?
To charge them i simply put one clip onto the negative of one battery, then the other clip onto the positive of the other battery.

The two batteries are next to each other, and a cable goes from the negative of one to the negative of the other. Then a cable from each of the positive terminals goes into the back of the off/1/both/2 switch.

While i still had the C-Tek aligator clips on the battery terminals (the negative of one and the positive of the other) i stuck the multimeter into the C-Tek plug and got 8 volts.

Then i disconnected the negative terminal of the 'wet' battery and still got 8 volts from its terminals.

I also spent some time reading this:
1/BOTH/2/OFF Switches Thoughts & Musings -
I think i absorbed some of it, but not enough...

Maybe i didn't charge them right?
Maybe i didn't have the off/1/both/2 switch in the right position for charging, or the right position for starting?

Is there anything dumb I've forgotten?
Or are my batteries just dead?


monte 13-09-2013 23:57

Re: Are my batteries knackered?
they soiud knackered mate :)

rebel heart 14-09-2013 00:00

Re: Are my batteries knackered?
If I ever saw 8.5, or honestly even less than 12.0 on my batteries, I'd be shopping for a new set. No matter how you slice it, it's pretty terrible for batteries to be sitting in a discharged (<12) voltage for that long. I doubt it's the first time they've been neglected.

To give you an idea, I've never seen under 12.3 on my lead acids (T105), under load.

smac999 14-09-2013 00:02

Re: Are my batteries knackered?
you only charged one of the batteries. after 4 days it should have started off of that one. (you'd have to figure out which was battery 1 and which was battery 2 to put the swtich to the one that was charged)

that one is probably dead. try charging the other one and see what happens.

you need to charge one at a time. put the charger on the pos and neg of the same battery. then do the other one. or put the switch to both while charging. but with that small charger. I would do one at a time. with the switch off.

they are probably weak though. and might not last too too long.

Normanby 14-09-2013 00:40

Re: Are my batteries knackered?
Righto, thanks. This is boat number 5 for me, and it seems that every time i acquire a new boat the batteries need replacing.

Battery neglect seems to an epidemic (or perhaps it's because i always buy the cheap boats!).

Before giving up, I'll take the terminals off both batteries, then try charging the AGM for a day or two - see what happens.

I had the switch on "off" when charging, then on "both" when trying to start the motor. So i guess it's possible i only charged one battery, and it was the dead one.

Or, by trying to start on "both" the dead one sucked life out of the good one?

Anyhow, that's me going in circles. I'll try charging, then starting off, each battery individually and see what happens. Just to make sure I'm not throwing away a useable battery.

Fingers crossed that the 'wet' one is dead and the AGM is revive-able.

This, by the way, is my charger:


GoPack 14-09-2013 01:59

Re: Are my batteries knackered?
Take the batteries to an auto parts store and have them check 'em.
(Here it would be NAPA, AutoZone, Advanced Auto and the like.)

colemj 14-09-2013 06:40

Re: Are my batteries knackered?
8.5V after a charge means that two of the cells in a battery are internally shorted - it's knackered.

I'm surprised that battery did not get VERY hot and gas while charging.


sabray 14-09-2013 06:45

I think I would take them off the boat . You could play around with trying to salvage the Agm in a ace that can't burn down or sink. Or have them tested at a shop.

Normanby 14-09-2013 06:59

When tested in a shop, can they do it on the spot or do they charge them overnight then test?

skipmac 14-09-2013 07:23

Re: Are my batteries knackered?
smac999 caught the main problem with your charging plan. The way you charged; connecting charger neg to one battery and charger positive to the other only charged that battery. You pointed out that the two battery negatives are connected but the battery positives go to the 1-2-Both switch. Unless that switch is turned to Both, the two batteries are electrically separated even though the negatives are connected.

So to charge both batteries you need to connect to both battery positive terminals by some way. Some chargers have two outputs so you can connect one output to each battery or you can connect the charger to one battery but leave the selector switch to Both when charging.

All that being said, due to the long storage in a discharged state your batteries are probably knackered. A good strong charge and equalization might bring them back enough to use for a while but I would go for new ones.

Normanby 14-09-2013 07:33

Ah ha!

That makes sense.

BTW, it's nice to see non-Aussies embrace the term knackered.

Badsanta 14-09-2013 08:09

When you replace them you should get them the same and not mix agm with flooded.
One trick I just learned from my battery shop. I had a new battery in the car and left my lights on. I put my portable charger on it and it said it was bad well the computer display on it did. So I took it back to the battery shop and he said it was fine just needed a charge. He said that the problem was with my fancy charger that once the battery gets discharged to a low point the charger wont charge. To fix that I had to put jumper cables from a good battery to the bad one then put charger to bad one. The smart charger will sence power and start charging then remove jumpers and good battery from the system.
Had to fake out that smart charger and Bobs your uncle.

skipmac 14-09-2013 09:15

Re: Are my batteries knackered?

Originally Posted by Normanby (Post 1339463)
Ah ha!

That makes sense.

BTW, it's nice to see non-Aussies embrace the term knackered.

Well in my case I spend a bit of time hanging with Poms and they seem to speak a similar dialect. :D

deckofficer 14-09-2013 09:23

Re: Are my batteries knackered?
The number 1 killer of batteries is for them to be left in a discharged state for any length of time.

Zil 14-09-2013 10:56

Re: Are my batteries knackered?
i have recovered batteries left for dead. Geet a good charge into each independently and see what happens. The auto stores use a load tester to evaluate batteries. They must be fully charged for that test. NAPA does not have a fee for the test, but will have a fee for charging the battery.
If you do recover they are only good for temporary use. Plan to replace. Don't trust them.

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