AGM batteries upgrade

[Pedro Morais]

Hi All,

this may have been discussed many times, but since I'm still in the learning curve I would like to get your bright brains around my questions.

I have a 2008 Beneteau Cyclades 39.3 with a ENAG Charger (SEEL 008377) and an Hitachi Alternator. It came with standard lead acid battery (2x 140) from Varta (https://www.varta-automotive.pt/pt-p...se/930-140-080)

Ok, after 36h on anchor I start to get the bat alarm buzz while by Victron smart shunt sill provides 12.2, 12.3 V. After some more hours the buzz starts a continuum beep... not pleasant.

My plan is to upgrade for AGM Bat and for that I'm already studding how to do it .

1- ask ENAG if that charger accepts AGM profiles. I doubt... so plant to buy a Charger with 40amp for a potential 400 amph service bank

2 - installing some solar panels with Victron MPPT. (ongoing)

3 - my big concern : Alternator for AGM... Should I buy a Alternator Controller (Sterling) and change also the starting bat for AGM, or buy a DC to DC charger and keep normal bat for starting and AGM for service. Here my concern is the shore charger, because I'll have difference bat profiles, lead acid and AGM.


Any hints or ideas on how you tackle this project?

thanks in advance

[OldManMirage]

We have been discussing this exact topic in a forum, you don't need AGM batteries, you just need more battery capacity. That batteries you have now are actually "dual purpose" according to the link you gave. This means they are not true deep cycle batteries.

You need real deep cycle batteries. If you have a battery selector switch the easiest thing would be to use one of your original batteries for a "starter" or reserve battery and add a pair of larger deep cycle batteries for a "house" bank.

You do not need AGM

[ranger58sb]

Originally Posted by Pedro Morais

Ok, after 36h on anchor I start to get the bat alarm buzz while by Victron smart shunt sill provides 12.2, 12.3 V. After some more hours the buzz starts a continuum beep... not pleasant.

My plan is to upgrade for AGM Bat and for that I'm already studding how to do it .

1- ask ENAG if that charger accepts AGM profiles. I doubt... so plant to buy a Charger with 40amp for a potential 400 amph service bank

2 - installing some solar panels with Victron MPPT. (ongoing)

3 - my big concern : Alternator for AGM... Should I buy a Alternator Controller (Sterling) and change also the starting bat for AGM, or buy a DC to DC charger and keep normal bat for starting and AGM for service. Here my concern is the shore charger, because I'll have difference bat profiles, lead acid and AGM.

First, I'd guess 12.2-12.3VDC is approaching approx. 50% depth of discharge (DoD), and most battery makers recommend you not discharge below 50% DoD for best longevity. One simple solution, no new batteries required, is to recharge when you get to 12.2-12.3V.

Second, if those are wet batteries and they're easy enough to service, switching to AGM may or may not be an improvement. AGM isn't magic. And you can read about AGMs and PSOC in other threads around here. If you DO decide to buy new batteries, and if these are only for house service, then real deep cycle batteries (versus dual purpose) would likely be better. If these are also used for starting a relatively small engine, deep cycle batteries would generally be no problem.

Third, the batteries will probably care more about exact bulk/absorption and float voltages from your charger -- then they will about the name of a given charging profile. Learn what voltages Varta recommends, then see if the charger can do that -- probably without strict regard to profile name.

And finally, your alternator probably won't care what kind of batteries you have, and your batteries probably won't care what kinf of alternator you have... as long as the voltages are within appropriate range.

-Chris