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Old 15-09-2013, 21:20   #16
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Good news (maybe).

As I removed the batteries the neg-to-neg lead crumbled in my hands.

Soooo, maybe when I was 'charging' the batteries i was charging nothing.

I've taken both batteries to an auto electrician who is going to charge them up and test them.

Fingers crossed the AGM is salvageable.

Thanks for the tips.

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Old 16-09-2013, 10:36   #17
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Re: Are my batteries knackered?

First of all -- most used boats will have knackered batteries. Batteries are consumables like filters and belts, and hardly anyone selling a boat bothers to keep the batteries in good condition, hence they die. The absolute most basic items to do on a new to you boat will be replacing all the batts, full service of engines on board, cleaning fuel tank, etc. That's just the very beginning of course

Just because batteries were discharged to zero a few times doesn't necessarily mean they're ruined. It depends a lot on what kind of batteries they are. I had a new set of Vartas which were knackered after a single incident of being run out and left like that. I got less than two years out of them. My current batteries are Trojans. As a result of various mishaps, they have been run out dead flat twice and left like that for several weeks. After being brought carefully from the dead both times, they are still good as new. Literally -- I regularly measure the capacity with an Argus battery tester, which shows that they are still holding more charge than when they were new (before being broken in), despite those two incidents, and being almost two years old. That's the difference between a car-type battery (even if it's sold for marine purposes, as a "semi-deep discharge" or "leisure" battery) and a battery with thick plates and heavy internal construction.

That being said, being left dead for a few weeks is probably the limit. Few batteries will survive being left dead for months, as so often happens to boats which are for sale.

So if I were you, I wouldn't faff about with it -- just go buy a couple new batteries and move on.

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Old 16-09-2013, 10:46   #18
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Boat: Cascade, Sloop, 42 - "Casual"
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Re: Are my batteries knackered?

Caution! Don't try to start your engine while the batteries are really low. It can cause problems with your starter motor.

Hang in there. You'll get it sorted out.

kind regards,
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Old 19-09-2013, 21:35   #19
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Good news (maybe)!

Took the batteries out as I said, auto electrician charged them for two days, and they tested okay, 12.75 volts each and the rated Amp hours.

Put them back in the boat, put the switch to "both" and the motor started just fine.

I let it run for 20 mins, checking the exhaust water and put the multimeter on the terminals. Both batteries look to be getting 14 volts from the alternator.

Turned the motor off, both batteries still showing 12.75 volts.

Left the boat for 48 hours and did the same as above, got the same results.

Looks like I might just have resurrected them. That's a tentative "woo hoo!"
Time will tell.

I'd happily just replace them if they're suspect, but with a new/old boat the shopping list is very long, I have to dole out the $ sparingly.

And while my boat spending has been well inside the initial budget, chiseling the teenager out of the nest has drained the coffers down to almost zero.

Ah parenthood; certainly the most expensive activity I've ever engaged in...

I'm moving the teen into her own apartment next week, them I'll move aboard. Getting rid of possessions as we speak.

Thanks for all the tips,
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Old 19-09-2013, 22:33   #20
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Location: Currently Tasmania after Pacific crossing
Boat: Catalina 42
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Re: Are my batteries knackered?

Looks like you have had a couple of wins there Matt! Keep an eye on Mainsails terrific website too...lots there!

I've replaced all my batteries recently and never see below 12.5v now. Check out BatteryValue....Brisbane for great value and price!

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