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Old 13-09-2019, 10:46   #1
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Home Battery Charger for AGM Batts?

I'll be storing the new AGM boat batteries indoors for the winter and would
appreciate suggestions on a suitable charger.

Will any charger work, or does it need to be specifically for AGM?


Lastly, would a charge every 4-5 weeks be adequate to maintain charge?

These are 100 amp batteries.

Thanks!
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Old 13-09-2019, 11:33   #2
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Re: Home Battery Charger for AGM Batts?

I stored our AGMs over a winter -- connected, in the boat, without charging at all -- for 5 months with no significant self-discharge over that whole period.

-Chris
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Old 13-09-2019, 11:42   #3
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Re: Home Battery Charger for AGM Batts?

Thanks, Chris, and I should have mentioned that I have no electrical
connection near the boat when it's on the cradle.
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Old 13-09-2019, 12:35   #4
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Re: Home Battery Charger for AGM Batts?

Quote:
Originally Posted by Sailon1 View Post
Thanks, Chris, and I should have mentioned that I have no electrical
connection near the boat when it's on the cradle.
I also have left Oddessey AGM batteries on the boat and in my garage without charging. The first time I stored on the boat they discharged to an unacceptable level i.e. 70% SOC within 6-8 weeks. The solution was to completely disconnect the batteries and under that scenario both on the boat and in my garage the batteries never dropped below 95% SOC over the course of a winter.
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Old 13-09-2019, 12:42   #5
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Re: Home Battery Charger for AGM Batts?

Thanks, SciSail, for the very useful information.
Judging from the forum input so far, I may not have to
lug the batteries home and then reinstall in the spring.

Installing the batteries in the spring is one of my least favorite
tasks for boat prep.
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Old 13-09-2019, 13:17   #6
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Re: Home Battery Charger for AGM Batts?

If I were you, I'd do some research on "What do AGM batteries need to stay healthy?"


In addition to this fine forum.


Here's some starting material for you:


AGM Batteries - Making The Choice (from Maine Sail)

https://forums.sailboatowners.com/in...choice.124973/

AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
https://forums.sailboatowners.com/in...teries.133773/

Additional Observations on the Limits of AGMs Electrical Systems 101
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Old 13-09-2019, 13:42   #7
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Re: Home Battery Charger for AGM Batts?

Every battery discharges, some quite a bit in one month, definitely hurts their longevity.

Volts are volts amps are amps, charger brand does not matter long as you know the mfg specs and are monitoring.

It would not be hard to rig connectors so the charger you usually use on the boat can be also used at home.

Topping up every week or two is better than just leaving on float unattended.
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Old 14-09-2019, 04:16   #8
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Re: Home Battery Charger for AGM Batts?

Quote:
Originally Posted by sogin View Post
I also have left Oddessey AGM batteries on the boat and in my garage without charging. The first time I stored on the boat they discharged to an unacceptable level i.e. 70% SOC within 6-8 weeks. The solution was to completely disconnect the batteries and under that scenario both on the boat and in my garage the batteries never dropped below 95% SOC over the course of a winter.

That's a point. I'm able to easily just turn off a few potentially parasitic loads -- CO detectors, shower sump, stereo memory, etc. -- that would otherwise cause some battery drawdown if left on. Once there are no hidden loads, AGM self-discharge has seemed negligible.

-Chris
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Old 14-09-2019, 04:22   #9
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Re: Home Battery Charger for AGM Batts?

Is the boat on the dry or in the water?
Think about the bilge pumps if in water!
A solar panel with a regulator can keep them up over the winter without shore power.

I have AGM spiral cell starter batteries, we use our engines rarely, only for docking and maneuvering in tight anchorages, they are charged by the alternators. Recently one battery was empty, so I needed to charge it by a 4 state charger (CTek 10A MXS 10 https://www.nootica.fr/accastillage/...0-12v-10a.html).

I have to reconsider the topping up of the start batteries even under way. The onboard instruments from the manufacturer are worthless for estimating SOC and SOH on the start batteries. They read 12.8V to 13V, but this is not the reality.
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Old 14-09-2019, 04:38   #10
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Re: Home Battery Charger for AGM Batts?

Most decent home chargers have an AGM setting. Quite a few higher end cars use AGM's.
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Old 14-09-2019, 04:43   #11
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Re: Home Battery Charger for AGM Batts?

I just bought this one, 240 volt, Pulse Battery charger, $36-00 Delivered,
Its also 110 Volts, It has both plugs, USA and Australian, 240 volt,
12 and 24 volts, automatically picks the voltage and turns itself off when the battery is charged,

I bought it specifically for my AGMs as I didnt have one, Just in case I needed to charge them up,

I am very impressed with it so far, It has put a full charge in two of my dead batterys, Lead acid types,
One has been dead for 7 years, the other one for at least 15 years,
I currently have it on a dead 200 amhr lead acid battery, 8D, Its been dead for 6 years and sitting outside in all weathers,

Cheers, Brian,
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Old 14-09-2019, 04:56   #12
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Re: Home Battery Charger for AGM Batts?

Quote:
Originally Posted by CatNewBee View Post
Is the boat on the dry or in the water?
Think about the bilge pumps if in water!
A solar panel with a regulator can keep them up over the winter without shore power.

I have AGM spiral cell starter batteries, we use our engines rarely, only for docking and maneuvering in tight anchorages, they are charged by the alternators. Recently one battery was empty, so I needed to charge it by a 4 state charger (CTek 10A MXS 10 https://www.nootica.fr/accastillage/...0-12v-10a.html).

I have to reconsider the topping up of the start batteries even under way. The onboard instruments from the manufacturer are worthless for estimating SOC and SOH on the start batteries. They read 12.8V to 13V, but this is not the reality.
Those CTEC chargers are $95-00 on Fleabay,
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Old 14-09-2019, 08:10   #13
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Re: Home Battery Charger for AGM Batts?

I take my AGMs home every winter, November to.May and top up the batteries regularly with a Motomaster Eliminator smart.tech charger. It shows charging amps and decreases amps as.it gets close.to.full charge. It shows Full when topped up and I disconnect. Bought at Canadian Tire in Canada. The batteries are 8 years old and still holding 95%. We charge with only solar on the boat. The.pain of moving batteries twice a year is off set by the lack of pain in the.pocket😉.
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Old 14-09-2019, 09:26   #14
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Re: Home Battery Charger for AGM Batts?

Quote:
Originally Posted by Sailon1 View Post
Thanks, Chris, and I should have mentioned that I have no electrical
connection near the boat when it's on the cradle.
OP says he's got no access to power when his boat is put up for the season, and doesn't want to remove and reload batteries from the boat.
From my experience AGM batteries do need a program for charging, equalization, and maintaining a float charge, that is different

As far as whether they will suffer damage from sitting unattached or not, if they remain in a discharged state they most certainly will have a reduced life expectancy.
Possibly a 100watt solar panel and a regulator that can be used with this battery set up is available?
Cheers,
SV Cloud Duster
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Old 14-09-2019, 10:00   #15
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Re: Home Battery Charger for AGM Batts?

Indoors implies taken off the boat, and solar not likely a practical option.

But yes whatever the source, even 20W is more than enough to counter self-discharge, as long as the bank is otherwise **fully** isolated, no parasitic loads at all.
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