AGM Conversion

RonM · Jul 15, 2015

There's a few things you should consider. First, changing from wet cell to AGM's is not a significant issue since both have some (but not all) "wet" characteristics. To answer your question, this is not a major problem. However, it does require some caveats!

1) Do you understand what settings exist or can be changed with your "older model Guest charger"? Determine what charging voltage and levels of charge it can provide.
2) With an answer to #1, determine the charging requirements for your new AGM battery as outlined by the AGM battery manufacturer. If your charge controller (Quest) provides the voltage and charge levels (bulk, absorption, float for example) required by the battery specifications, you'll be fine.
3) I'm not sure what you mean in reference to "battery controller". Do you mean, your battery master switch? I'm going to assume this is what you're talking about. Most battery master switches include a "connect" before "disconnect" function. If your battery switch isn't too ancient, you'll be fine with changing from "house" to "engine". Some of these switches have a "both" function. If yours is this kind, keep it on "both" as the engine alternator will then charge both batteries while operating your diesel engine.
4) Yes, change your solar charge controller to an AGM setting once the new battery is installed.
Hope this helps.

Maine Sail · Jul 15, 2015

I guess the question I have is what do you expect to gain by switching from flooded to AGM..?

Also be aware that not all AGM batteries are created equal and there are huge quality differences in how they handle deep cycling (see May 2015 issue of Practical Sailor). Lifeline, Odyssey, Northstar and Firefly are the only AGM batteries worth spending premium money on, at this point in time.

For AGM batteries it is more than picking an AGM setting, you need to match manufacturer guidelines for both float and absorption voltages and you will need temperature compensated charge equipment. There is no such thing as an "AGM setting" that works for all AGM batteries.....

Chief RA · Jul 15, 2015

Norm: Good to hear something from you! I am with Maine Sail on this, wondering why you would change from wet cells. Chief

Maine Sail · Jul 15, 2015

Piratenorm said:
I was switching up only because I can get two East Penn (West Marine) AGM series 31's for the same price as two flooded, with my employee discount. My soon to be over-and-out West Marine employee discount, as they are withdrawing from Canada. (sniff...)
It stemmed from being out for an overnight the other evening and discovering my batteries were not able to sustain two reading lights, one other house light plus my anchor light, all LED, and the stereo. When I flipped on my battery indicator gauge it showed my house was down to somewhere around 8 volts. I just assumed that my six year old flooded batteries were Kaput.
But, after searching through past posts about this, after posting MY request for info, I discovered that my flooded batteries, thanks to my solar panel, might be evaporating fluid on charge. So brain scientist (rocket surgeon) that I am I checked my fluid levels and discovered...wait for it...I was damn near dry! Apparently the new solar panel causes premature evaporation at a rate heretofore unbeknownst to me! So I've topped up the fluids, will check next week when I'm off on a four day trip and see how things are before committing to new batteries. Flooded, not AGM's, by the info I've read, thanks to past posted advice. Humbly withdrawing request for info...
Again, Thanks all.

Even with your employee discount you're still paying too much for the Deka AGM. They are also rather poor performing AGM's in deep cycling applications. You can find Deka/East Penn batteries at other resellers for half what WM sells them for.......

Chief RA · Jul 17, 2015

Norm: Not a problem. I think you know we advise carefully, plus, you know we like you! Let us know how the old batteries hold up.
Your friend, Chief