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Old 12-02-2018, 13:36   #1
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New lead acid batteries replaced fairly new 2AGMs- now what?

Hi-
Fairly new to this boat, so replaced the house bank batteries at the first sign of "trouble." Pulled into a marina on the GICW with house batteries not coming up to full charge with my alternator/engine running all day. Bought 2 of the recommended lead acid deep cvcle batteries and wired them in place of the two AGMs. Works great.

Now- the previous owner said one of the AGMs was a year old and the other one only a couple years old. He kept the boat at a dock and the batteries were float maintained (he knows what he's doing). So... I put the two AGM batteries in the bilge secured in battery boxes but not hooked up to anything or each other until I could figure out if there was a valuable use for them.

Is there?

I will be putting about 250 W of solar panels with an MPPT controller on the boat before our next adventure. Have read I should only parallel batteries through switches (as the current bank is connected) and should only have batteries of the same type and history in a bank. So can/should I create a second house bank with the older AGMs and put another A/B/Both switch between the two house banks?

The new Lead Acids are good sized for moderate use Type 27, about 150 Amp-hours. If I created the second house bank I would leave it in the bilge about 6 feet from the current house bank in the port lazarette.

Fred
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Old 12-02-2018, 14:45   #2
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

Most people scrap the old bank, replace with new.

Might get $50-100 for them on CL

Load test each batt is really the only way to know if they're still good for deep cycling usage.

If not may work as a Starter batt for a while, long as you've got easy backup.

If they actually help as ballast? Most boats are already too weighed down.
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Old 12-02-2018, 14:52   #3
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

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Originally Posted by john61ct View Post
Most people scrap the old bank, replace with new.

Might get $50-100 for them on CL

Load test each batt is really the only way to know if they're still good for deep cycling usage.

If not may work as a Starter batt for a while, long as you've got easy backup.

If they actually help as ballast? Most boats are already too weighed down.
Thanks for the reply- The reason I replaced them was the tech said the "load testing" would take all day and we wanted to get going. What's involved in load testing?
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Old 12-02-2018, 19:16   #4
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

"house batteries not coming up to full charge with my alternator/engine running all day"

how do you know they were not getting full? that is normally not an issue of a bad battery. a bad battery will get full. but have less capacity once you start discharging. unless you have a bad cell.

personaly I would ditch the old ones. if you want a bigger bank. buy 2 more of the exact same flooded 27's. they are probably only $100 each.

the proper way to test them is a c20 test. you'll need shore power and charger.
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Old 12-02-2018, 20:02   #5
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

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What's involved in load testing?
Search for

20 hour capacity test here

https://marinehowto.com/programming-a-battery-monitor/

Better yet read it all,* and check out the rest of the site.
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Old 13-02-2018, 08:45   #6
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

Fred,
Since you've already changed from AGM to Lead Acid, you may want to check the regulator between the alternator and the batteries. Don't know if you have an external or built into the alternator type but there are different settings for AGM and FLA batteries, especially if you are utilizing an external type of regulator.
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Old 13-02-2018, 09:14   #7
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

picking nits I know, but AGM and FLA are both lead acid chemistries.

FLA is usually robust enough to handle alt output, very few VRs have any adjustability.
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Old 13-02-2018, 09:24   #8
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

Just because the alternator was charging all day means nothing if it is a basic auto type internally regulated unit. I would be suspect
Of your alt being able to do the job unless you have good reason to believe the batteries are toaste.
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Old 13-02-2018, 09:33   #9
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

Fred, stick the AGMs on a shore power battery charger and give them a nice long soak and then try the battery test.

Whilst that is going on you need to work out how much electrical power you need at anchor and under sail including any night sailing. That will tell you the size of the bank you need and how many more batteries you need etc.

No point in buying batteries you don't need and you don't want to kill the new batteries because you drain them right down each night. There is a balance, you just need to find that sweet spot.

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Old 13-02-2018, 09:44   #10
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

Thanks SMAC-

I concluded they weren't to full charge because their voltage didn't go above the 50% calibration on my voltmeter.

Fred
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Old 13-02-2018, 09:46   #11
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

Thanks John, the c20 test was my next question.
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Old 13-02-2018, 12:53   #12
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

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Originally Posted by SailRocyPoint View Post
Just because the alternator was charging all day means nothing if it is a basic auto type internally regulated unit. I would be suspect
Of your alt being able to do the job unless you have good reason to believe the batteries are toaste.
It is the Automotive type alternator- Old Westerbeke 4-107 diesel and I'm dis-inclined to change the pulleys for a Balmar type big guy. I'm putting on a fairly good sized solar panel array- what else would you think I should consider that would "do the job?"

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Old 13-02-2018, 12:58   #13
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

Well a 70 amp balmar does not need a replacement belt. I had one on last boat yanmar 3HM35f engine and it would do just fine charging 3 group 31 agms and no problems with the belt
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Old 13-02-2018, 17:53   #14
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

With lots of propulsion motor runtime, a well regulated alt can make a huge contribution to overall power.

To the point that very little solar may be required.

Balmar's MC-614 does a great job, can be shifted to a higher output alt later, will accommodate any future chemistry including LFP.
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Old 13-02-2018, 18:33   #15
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Re: New lead acid batteries replaced fairly new 2AGMs- now what?

Of course the 614 is not cheap, and it requires either your current alternator to be modified to be externally regulated, or another alternator to be bought.
Big $$$,but worth it, if your going to be motoring often, if you almost never motor, donít waste your money, buy a Honda generator instead and a good shorepower charger.
250 W of Solar will of course help, but unless you have very modest energy consumption, itís not likely to be enough by itself.
If you already have a good shorepower Charger, a little Honda is hard to beat, cause of course you donít have to run your main engine just to charge batteries.
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