Deep Cycle Battery Ratings (AGM)

[Steve1]

hi - I am sure this is on the forum somewhere but I could not find it in a search. I will need to buy a deep cycle battery for an inverter (with a smart charger). I am not going to go Lithium yet, so was looking at AGM. My space constraints limit me to a group 31 size or smaller. There are all sorts of brands out there. Any suggestions of brands to prefer or avoid? Thanks very much

 

[ranger58sb]

Lifeline and Odyssey have good reps, I got very good results -- 11-12 years service -- from Odyssey Extreme TTPL G31s (named PC-2150s at the time), and Lifeline 31XTs offer even slightly more capacity (125Ah, IIRC).

Firefly Oasis Carbon Foam G31 AGMs (116Ah) have been building a decent rep and are said to offer more usable capacity, i.e., discharging below 50% is considered OK. More $$$.

-Chris

 

[DavidM]

I decided to go with cheap, but not cheaply made G31, AGM batteries I purchased on Amazon. I chose WindyNation, but Renogy a well known seller on Amazon is about the same price: $200 each.

I have been researching this question for years: Like FLA batteries, are there specific design or manufacturing things that can make AGM batteries work better in a deep cycle environment. I have never been able to find anything, so I concluded that an AGM battery is an AGM battery.

FWIW the physical details of the WindyNations were great: solid case, good mounting terminals. They have been in service for more than a year and fully charge after each discharge. I haven't done a load test though to determine if they still put out 100 Ahs.


David

 

[Bacchus]

Steve - welcome aboard TF
Not a bad idea to add your boat info to your profile when you have time. It can be useful at times for those answering questions.

I have used and been very satisfied with East Penn / Duracell and find Sams Club prices for Duracell (both FLA & AGM) hard to meet or beat.
I have looked recently and find stock is rather low in some sizes & locations.
My 3 EP 8Ds aboard (2 house & 1 thruster / start) are going on their 8th season in NE (use 6 mos / store w/o power 6 mos) and doing OK with s light drop in V over the 6 mos storage vs when checked other years.
My plan is to replace each 8D with a pair of GP31 AGMs as they are less $, equal or higher CCA/MCA and AH... AND A LOT EASIER TO HANDLE.

GP31s are a fairly common size produced in reasonable qtys and at reasonable $ - I'd go as large as you have room for.

 

[ranger58sb]

My plan is to replace each 8D with a pair of GP31 AGMs as they are less $, equal or higher CCA/MCA and AH... AND A LOT EASIER TO HANDLE.

FWIW...

Until I saw the Lifeline 31XTs (125 Ah) and until Firefly upped their G31 capacity rating (to 116 Ah). (I've not tried either of those.)

I didn't find any other 2x G31s that would provide similar Ah as most single 8Ds (usually somewhere between 220-245 Ah).

-Chris

 

[Bacchus]

FWIW...



Until I saw the Lifeline 31XTs (125 Ah) and until Firefly upped their G31 capacity rating (to 116 Ah). (I've not tried either of those.)



I didn't find any other 2x G31s that would provide similar Ah as most single 8Ds (usually somewhere between 220-245 Ah).



-Chris

You are right as for AH 31s are a little less than the 8Ds. If AH needed I would add an additional GP31 to the bank

 

[Gdavid]

I bought 4 Duracell 31 AGM's through my local Batteries Plus last year, 2 were in stock and I had to wait for the last two and there was a brief additional delay but I was very satisfied with the communication from Batteries Plus and there were pretty liberal with what they accepted as cores. I like the fact that I have a physical address to walk into and someone to speak for support if needed.

 

[TBill36]

You may want to look into what you intend to run with the inverter. Start-up amps can be a problem. I don't know of any data, but I suspect a single or low amp-hr bank has less start-up capability than a larger bank. I have a 220 amp-hr bank that has difficulty starting a small chest freezer and apartment size refrigerator at the same time. My inverter has the capability, but I don't think the bank does. They both pull 5 amps each when running, but start-up pulls about 60.

Also, for AGMs and FLAs, the battery that weighs more is usually better.

 

[Seevee]

hi - I am sure this is on the forum somewhere but I could not find it in a search. I will need to buy a deep cycle battery for an inverter (with a smart charger). I am not going to go Lithium yet, so was looking at AGM. My space constraints limit me to a group 31 size or smaller. There are all sorts of brands out there. Any suggestions of brands to prefer or avoid? Thanks very much

Steve,


First, how many batteries do you want, and what's your power requirements?
I might argue that the 6v golf cart batteries give you more ah for the buck, and take up less space than the Group 31, unless you're only buying one.


I like Lifeline batteries, but not the cheapest but excellent quality and support. There are some cheaper ones out there. I considered an AGM 225ah one from Tampabaybatteries.com 813-917-0331. Had friends buy them and are happy. They sold me the Lifeline 6v GPL-4CT (220ah) for $339 and are delivering them today free, but they are local.


I also considered the Lifepo, but at $6500 for about the same power, just didn't make sense for my operation.

 

[CMS]

With Firefly out of the US market you have a few choices,. Not all AGM BATTERIES ARE CREATED EQUAL...


Good Quality AGM's
Odyssey
Northstar
Lifeline
Rolls
Full River

East Penn 105Ah G-31 AGM 4/2018 DATE CODE, TESTED 11/2018 @5.25A = 67.42Ah

 

[ranger58sb]

Glad you're back, Rod!

Firefly gone? Hadn't heard.

Looks like Enersys acquired Northstar (or maybe the other way around?), and it seems like some of their Odyssey/Northstar product naming is overlapping and/or merging...

-Chris

 

[DavidM]

Have you had any bad experiences with other AGM batteries? Yes, those are the premium brands, but I can't see any differences between how those are built and the cheap, online brands like Renogy and WindyNation at about half the price.

David

With Firefly out of the US market you have a few choices,. Not all AGM BATTERIES ARE CREATED EQUAL...


Good Quality AGM's
Odyssey
Northstar
Lifeline
Rolls
Full River

East Penn 105Ah G-31 AGM 4/2018 DATE CODE, TESTED 11/2018 @5.25A = 67.42Ah

 

[ranger58sb]

Have you had any bad experiences with other AGM batteries? Yes, those are the premium brands, but I can't see any differences between how those are built and the cheap, online brands like Renogy and WindyNation at about half the price.

David

Taking a stab at interpreting Rod's graph... I think it's saying an East Penn AGM battery that started at (and is advertised with) a nominal 105Ah capacity now only tests at 67.42Ah after only 7 months. (No hint as to how many cycles that represents.)

East Penn usually being described as one of the most reliable "normal price" brands.

Compared to Lifeline, for example, who rates their deep cycle AGMs at 1000 cycles to 50% DoD. (That being lab conditions, though, and I think Rod has said elsewhere that lab conditions and actually reality are widely disparate concepts. Still...)

-Chris

 

[timb7734]

One also needs to pay attention to the age of the battery on the shelf, and purchase the freshest battery (newest) available. The mfg date is the last numbers of the battery serial number. AGMs sitting on a shelf at a dealer should be charged at least monthly or suffer life degradation before even getting in a boat. Most dealers do not do this.

 

[Steve1]

Hi,

thanks for all of your replies. Here is some more info. My boat currently has a battery box that holds 3 group 31 sized batteries. there are two starter batteries currently in the box, one for each engine. They have a dedicated battery charger and (I assume) are also charged by their respective engine alternators when they are running.
These batteries currently also power the 'house'. All of the house lights have been converted to LED, BTW. When I look at my ammeter with all of the lights in the boat turned on, I am drawing less than 2 amps. Of course, water pump and toilet are much heavier hitters.

My aim is to work my way into a separate house system, solar, etc. But I am not going to do it in one go. So my phase one will be to add a single Group 31 battery in the empty battery box slot and an inverter/charger wired to some new outlets that I will install. The inverter is oversized at 3K. I know that 1 battery will not supply that that kind of wattage for very long but I did want to plan for the future and make sure I had start up amps for a small fridge or something like that if I every added it.

 

[ranger58sb]

thanks for all of your replies. Here is some more info. My boat currently has a battery box that holds 3 group 31 sized batteries. there are two starter batteries currently in the box, one for each engine. They have a dedicated battery charger and (I assume) are also charged by their respective engine alternators when they are running.
These batteries currently also power the 'house'.

My aim is to work my way into a separate house system, solar, etc. But I am not going to do it in one go. So my phase one will be to add a single Group 31 battery in the empty battery box slot and an inverter/charger wired to some new outlets that I will install. The inverter is oversized at 3K.

If the two separate G31 banks also split your house loads roughly in half... you could consider adding a third G31 to each bank to add immediate whole-house capacity for life at anchor.

If you add an inverter/charger to one of those banks, it'll power a certain amount of stuff easily enough. If it happens you could eventually replace (that) one bank with 4x 6V GC2s or the taller versions, or even L16s if you have available height, that would be a boatload of capacity. Depends on your available space, but 4x GC2 don't take up much more footprint than 3x G31s, depending on how they're laid out.

If you usually use your original charger for the non-inverter bank, and the inverter/charger for the inverter bank, that'll likely increase your overall recharging speed -- within the capability of the batteries. If you leave it so your original charger can also charge the invert bank at the same time at your discretion, that could be a useful option at anchor if you've sometimes depleted the inverter bank more than usual.

Just thoughts...

Oh, wait... rereading yours... it's a single battery box, only one G31 per bank now... never mind... I'm probably off the mark...

-Chris

 

[CMS]

Have you had any bad experiences with other AGM batteries? Yes, those are the premium brands, but I can't see any differences between how those are built and the cheap, online brands like Renogy and WindyNation at about half the price.

David

Yes plenty of bad experiences.. I listed the only batteries that routinely perform well. Until all the off-shore AGM'S started showing up the only consistently bad AGM's we saw were East Penn. Now we see bad results from Victron,Mastervolt, any JCI made AGM, RENOGY, V-MAX ETC. ETC. ETC...