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Old 21-12-2022, 10:46   #1
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Location: Tampa, Fl
Boat: Hanse 458
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Whatís the best daily charging regimen for new AGMíS?

Hello all,

Iíve read a bunch, researched a bunch and learned a bunch but, Ö I still have questions. So, letís get into it.

Iíve already ordered the Victron AGMís. Theyíre the same size and amp hours so no construction or rewiring is required. Itís the easiest solution for me now and a lot cheaper than the LiFePo conversion now. So letís skip that discussion.

My current, dying batteries were factory installed in Europe (I think Q batteries) and are about 3 years old - 2 160ah 4d size AGMíS. Theyíve been mostly charged from 50 amp marina shore power. This past summer I added 390 watts of solar. Most of the load has been from one or two fridge units drawing about 4 amps each which exist mostly to keep beer and ginger beer cold. I have A/C and keep it on because itís hotter than Hades down here in the summer and a tad on the humid side as well. In the winter I can turn those off or only run moisture control. None of that affects the battery but itís why I keep shore power hooked up and on. I can turn the charger off and leave the batteries with only the solar. We donít use the boat as much as Iíd like. Currently, we occasionally take her out for a one or two night anchor out.

One thing Iíve learned is that the Florida heat doesnít help the battery longevity much, which is another good reason to keep the A/C running at the dock. Iím hoping to make the new batteries last a little longer though. I think perhaps I could have done better by my current pair.

Looking for charging technique. I know thereís a lot of diverse thought here and that if ten people chime in, there will be 12 opinions. Iím open to suggestions. What do you guys and girls think is the best way to maintain new AGMís? Should I just leave shore power plugged in and on with solar charging as well, or leave the shore power off and just charge with the sun until I need to get them back up to 100% or, possibly, just turn everything off and let the boat sit and not charge until I need to. I donít really have to run the fridges - just a luxury. I have a Victron battery monitor and Globalink and use the Victron Connect and VSM apps to keep tabs on everything.

Thanks in advance for any help.
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Old 21-12-2022, 11:14   #2
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Re: Whatís the best daily charging regimen for new AGMíS?

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Originally Posted by Mike32 View Post
Looking for charging technique. I know there’s a lot of diverse thought here and that if ten people chime in, there will be 12 opinions. I’m open to suggestions. What do you guys and girls think is the best way to maintain new AGM’s? Should I just leave shore power plugged in and on with solar charging as well, or leave the shore power off and just charge with the sun until I need to get them back up to 100% or, possibly, just turn everything off and let the boat sit and not charge until I need to.

I can tell you what we did with Odyssey and Lifeline AGMs... but can't speak to implications of solar.

We first learned specific recommended bulk/absorption and float voltages for each battery... float being especially important. We set the chargers for those voltages. Shore power on all the time. We left the chargers on all the time. Everything on the boat (freezer, fridges, etc.) on however we wanted. Done.

We got 11-12 seasons from the Odyssey banks. Didn't have as much time with the Lifeline bank (before we traded boats), but would have expected pretty much the same.

-Chris
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Old 21-12-2022, 11:33   #3
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Re: Whatís the best daily charging regimen for new AGMíS?

For any lead-acid chemistry, as long as the float voltage is appropriate, the best thing you can do is to have a constant charging source (shore power) keeping them in float when not in use.
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Old 23-12-2022, 06:05   #4
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Re: Whatís the best daily charging regimen for new AGMíS?

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Originally Posted by rslifkin View Post
For any lead-acid chemistry, as long as the float voltage is appropriate, the best thing you can do is to have a constant charging source (shore power) keeping them in float when not in use.
Do you think having solar running up the voltage every afternoon will be detrimental or a non-issue?
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Old 23-12-2022, 07:27   #5
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Re: Whatís the best daily charging regimen for new AGMíS?

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Do you think having solar running up the voltage every afternoon will be detrimental or a non-issue?

I haven't found it to be an issue on my boat, although my solar controllers end absorption based on amps going into the batteries. So when the sun comes up in the morning, the voltage gets pushed up to absorb for about a minute, then drops back to float for the rest of the day.
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Old 23-12-2022, 07:44   #6
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Re: Whatís the best daily charging regimen for new AGMíS?

Been off the grid for 5 years, 4 4d deep cycles running only fridge when not on board. 630 w solar. Batteries last longer, don't need constant water, zincs/anodes last longer not being connected to shore. I have no AC however.
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