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Old 30-11-2020, 09:33   #1
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Help pls: Will this tester show me anything

Trying to help a friend who has 3 AGM 130 Ah batteries on seawind. Batteries are about 4.5 yrs old.

https://www.westmarine.com/buy/maste...97?recordNum=9

When he uses his windlass recently, electronics reboot. He has used these batteries pretty heavily, been discharged down to low 11s when I was with him last winter sailing, though came back to pretty good health with solar and dockside charge, no problems through the spring and summer, but this situation is now occurring. But now even after being plugged in for a week, and voltage showing charged, electronics still rebooting when windlass is used.

He bought this item to test them: I am not sure this will tell us anything as it is CCA, not Ah being measured.

https://www.amazon.com/gp/product/B0...0?ie=UTF8&th=1

My thoughts are that the batteries are at the end of their life and just replace them? Will this tester show anything before spending $1.5K?
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Old 30-11-2020, 14:41   #2
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Re: Help pls: Will this tester show me anything

The links aren't working for me so I can't comment on the products, but the symptoms sound like dead batteries to me.

One thing I learned when going through the same exercise last year was that batteries showing "charged" actually mean "charged to their current capacity." In my case it was nominal 210 Ah AGMs that, fully charged, turned out to have about 25 Ah actual capacity.

I found this out by building my own device to do the 20 hour test (look it up); cost me about $100.
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Old 30-11-2020, 15:04   #3
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Re: Help pls: Will this tester show me anything

Quote:
Originally Posted by jbinbi View Post
Trying to help a friend who has 3 AGM 130 Ah batteries on seawind. Batteries are about 4.5 yrs old.

https://www.westmarine.com/buy/maste...97?recordNum=9

When he uses his windlass recently, electronics reboot. He has used these batteries pretty heavily, been discharged down to low 11s when I was with him last winter sailing, though came back to pretty good health with solar and dockside charge, no problems through the spring and summer, but this situation is now occurring. But now even after being plugged in for a week, and voltage showing charged, electronics still rebooting when windlass is used.

He bought this item to test them: I am not sure this will tell us anything as it is CCA, not Ah being measured.

https://www.amazon.com/gp/product/B0...0?ie=UTF8&th=1

My thoughts are that the batteries are at the end of their life and just replace them? Will this tester show anything before spending $1.5K?
The causes of that electronics reset could be:
  1. the batteries have increased internal resistance (end of life)
  2. there's resistance in a connection between the batteries and where the power splits off to go to the DC panel and the windlass
Check the obvious stuff like the battery terminal connections are tight.

I have a similar cheap battery tester, and it can sometimes be helpful detecting a bad battery. A better test might be to measure DC voltage right at the battery, run the windlass and observe how much the voltage dips. If your testing points to a bad battery, take it/them to a good battery place and have them test again with their better test equipment.
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Old 30-11-2020, 15:28   #4
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Re: Help pls: Will this tester show me anything

^^ Good advice - check the basics first. If a voltmeter directly at the battery terminals shows significant drop then the problem has to be the batteries themselves.
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Old 01-12-2020, 09:31   #5
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Re: Help pls: Will this tester show me anything

Is the engine on when using the windlass? It should be, and his problem can be explained by the voltage drop if using the windlass on batteries alone.
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Old 01-12-2020, 09:46   #6
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Re: Help pls: Will this tester show me anything

Can a tester designed to measure CCA measure AH? No. Can a cheap Chinesium $35 tester work like a $300+ decent quality battery tester? Also no.

Likely your batteries are shot if he runs them to 11V to 11.5V a lot and they are that old. Take them to someone that has a real tester and check but he probably needs batteries.

Could be another issue as others have posted.
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Old 01-12-2020, 10:57   #7
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Re: Help pls: Will this tester show me anything

engine on, but this is a seawind with 20hp outboards, i think they have like 20A alt. But yes.

Decided that should just buy new batteries at this stage.
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Old 01-12-2020, 12:03   #8
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Re: Help pls: Will this tester show me anything

I agree with others that a 'battery tester' is not needed just a voltmeter. If the voltage dips below 10.5v at the battery that is what is shutting down the electronics. This means that either the windlass is drawing more current for some reason or the batteries are struggling to supply it. It is possible that corrosion or something is increasing the load on the windlass motor but from what you say it is most that likely that the battery bank is dead. 4.5yrs is a reasonable life for AGM's and they are sensitive beasts so any over discharge or over charge significantly shortens life. If he wants longer life go for 'open' cells that can be topped up and use 2 x 380a/h 6v cells instead of multiple 12v batteries. 6v cells usually have much longer life than 12v ones.
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Old 01-12-2020, 12:16   #9
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Re: Help pls: Will this tester show me anything

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use 2 x 380a/h 6v cells instead of multiple 12v batteries. 6v cells usually have much longer life than 12v ones.
Nice big batteries, can you pick one up? I struggle with type 31 batteries using the dinghy to reach the yacht, then up on to the deck and finally down below. Not forgetting the final lift over the fare side of the battery box to drop it in.

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Old 01-12-2020, 13:01   #10
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Re: Help pls: Will this tester show me anything

I would not dream of lifting a battery by hand onto a boat from the dock let alone from a dingy that's what tackles are for. Super high risk of injury or dropping the battery. Ideally your battery compartment should be in a place where you can lift them with the boom and drop them in direct. If not use a skate board or similar to move them along the sole and fit a strong point in the deck head for the final lift. On my boat I have a boom tackle set up as part of the MOB gear and use this for batteries or other heavy lifts onto the boat.
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Old 01-12-2020, 13:21   #11
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Re: Help pls: Will this tester show me anything

I have a similar battery condition tester bought at Harbor Freight. I am satisfied with how it works. Good advise from other posters, check voltage at battery terminals with vom meter while operating heavy draw, winch, starter ECT. Also check voltage at the winch or other draw to see if the readings are fairly close. I replaced battery, starter, alternator only to find the problem was bad connection between battery terminal and cable on a truck.
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Old 01-12-2020, 13:41   #12
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Re: Help pls: Will this tester show me anything

I don't think that is a true (resistive) load tester. It uses some type of algorithm to do a simulated load test. Some people will use a dedicated windlass battery. Even a good battery bank can cause problems with electronic cut outs during engine cranking. This is a real load tester: https://www.amazon.com/OTC-3180-Batt...omotive&sr=1-5
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Old 01-12-2020, 15:54   #13
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Re: Help pls: Will this tester show me anything

I have a similar tester and believe it is useful. It seems that an approximate conversion factor from ah to cca is x7. That is not completely accurate but near enough for this purpose. Batteries must be fully charged, disconnected then left at rest for a period, no charge or discharge. When testing care must be given to getting a good connection on the terminals, even a slightly less than clean or perfect connection changes the result. so go through the process 2 or 3 times each battery to be confident of result.

This does not replace a proper load tester, but does give you an idea of where you are at.
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Old 07-12-2020, 18:15   #14
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Re: Help pls: Will this tester show me anything

Some more testing info. Connections at battery look good. Ran the windlass without charger or solar connected.

Showed low to mid 12ish volts to start. Dropped about 25' of chain. V dropped to about 11.8. Then dropped another 2' and everything reset. Now I am thinking there is an issue with the windlass and not the batteries? There is a foot switch by the windlass, that doesn't work, I haven't buzzed it out. Having been dropping with the switch by the helm. Have not looked for loose connections etc at windlass.
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Old 07-12-2020, 18:29   #15
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Re: Help pls: Will this tester show me anything

Quote:
Originally Posted by Thumbs Up View Post
I don't think that is a true (resistive) load tester. It uses some type of algorithm to do a simulated load test. Some people will use a dedicated windlass battery. Even a good battery bank can cause problems with electronic cut outs during engine cranking. This is a real load tester: https://www.amazon.com/OTC-3180-Batt...omotive&sr=1-5
This. I can tell you from 50+ years in the auto repair industry that a cheap capacitive discharge battery tester will not accurately diagnose an AGM battery. You would be much better off using a resistive load tester. If you want to use a capacitive discharge type on an AGM for loads you better get ready to part with several hundred dollars.
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