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Old 07-20-2019, 11:42 PM   #1
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AGM Battery advise in 2019

Hi all, I've read several threads on here and know there is a lot of debate on this subject, but I am mainly looking for contemporary opinions on the issue of a quality AGM battery that won't break my bank (no pun intended). All the articles I found on line are thinly veiled marketing ads for a specific battery, and many of the threads on here are a few years old already.

My setup: I have 200 watts of solar with a MPPT controller, a "freedom" 1800 watt inverter/charger that is compatible with AGM batteries, and currently (2) 6 volt excide GC-135s joined in a series. I want to switch to AGM Batteries for maintenance reasons and am committed to this plan. I boon dock for a week at a time (with a backup generator I only use if necessary) and mostly am using the batteries and inverter to recharge my two electric bike batteries (36 Volt systems). I am looking for something affordable, maybe something like the Odyssey PC680 Battery for around $130 each.
Thoughts???
Should I get two and then run them in parallel? How would this compare to my old set up (amp hours wise)? I know I won't be starting any motors with my set up, but because I will be using my inverter a decent amount, should I consider a dual purpose battery???
Looking for wisdom here with the components I already have.
Thanks
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Old 07-21-2019, 03:56 AM   #2
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First, I am not an expert, just an informed user. Not much has changed about lead acid batteries in a long time. Your batteries are designed for deep discharge, the AGM's should not be taken below 50%. Yours are 226 amp-hours, I think, but I do not know what size AGM's you can fit. Whatever you do fit, I suspect your will have less capacity. But, as you point out the AGM's will have less, almost zero, maintenance and will easily last longer.
I don't think you need to worry about inverter use as long as you don't discharge below 50%. I advocate parallel 12v, always, so just fit the biggest ones you can.
Larry
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Old 07-21-2019, 05:30 AM   #3
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I also should have said that over the years the Odyssey batteries have shown more failure reports than others, but it could also be that there are more of them out there. I don't know. Lifelines are the gold standard so, of course, they are the most expensive. I ran Lifelines on my boat for many years with no problems. After about 6 years on a set, though, you could see that capacity was diminishing. Those batteries saw many cycles because I did use them a lot.
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Old 07-21-2019, 07:32 AM   #4
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AGM Battery advise in 2019

Lifeline are the way to go for our use as house batteries

Based on years of marine experience
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Old 07-21-2019, 07:38 AM   #5
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Our grp 27's lasted 11 Seasons and are still in service as sump pump back-up.

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Old 07-21-2019, 07:39 AM   #6
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Hi

There is a tradeoff making a battery. You can really pack everything in (thin plates) and get a lot of amp hours in a given size - or - you can be a bit more conservative, have fewer amp hours, but more reliability.

This was the issue with the original DieHard's and it's the issue with several batteries today. If you are after max power per in a given size ... fine. Otherwise, go with something else.

Cost wise, a good set of good AGM's are going to hit the credit card pretty hard. When they were the only alternative to flooded, that's just what you did. Choice A or choice B , pick one.

Today, there *is* another choice - Lithium's. Before I put down a big pile of cash on AGM's, I'd certainly consider them as an alternative. That's not to say they are the right decision, only that you should consider them. They likely will outlast the alternatives by a wide margin .... They also give you the full capacity rating as "usable" energy. If you buy 200AH, you can use 200AH. No more buy 200AH, but only use 100AH.

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Old 07-21-2019, 07:51 AM   #7
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Love the concept by dang they are expensive
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Old 07-21-2019, 08:24 AM   #8
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Trojan T-105 Flooded Lead Acid 6 Volts Golf Cart Batteries are still the standard but then you are installing them into a trailer and a trailer may diminish the life span due to the movement. I typically get 6-7 years in my motorhome ('82 Newell).
I put a West Marine AGM motorcycle size in an Avon inflatable. Then when I got my '59 Glasspar Avalon I bought a West Marine Group 24 AGM & put the 1st one as a backup. The 1st one lasted an amazing 13 years while the #24 only 10 years.

Not trying to reinvent the wheel I bought 2 size 24 AGM Batteries from West Marine for our 1958 Airstream Traveler. We have gone 7 days Dry-Camping with ample power but then we do live simple when Dry-Camping.
My best advice to you is to be sure that you have and setup the Charging of the Batteries.
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Old 07-21-2019, 08:53 AM   #9
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While you didn't say exactly why you wanted AGMs, other than to charge your bikes (a assume a low draw charger?), AGMs may have several benefits to your use.

Benefits - quicker charging, better high load support (and capacity) for your inverter uses, less maintenance

Are you mounting these in the stock location in the battery box? This roughly limits you to a Grp 27 form factor, which are generally rated ~95Ah. Yes, this is a smaller number than most 6V form factors, but possibly a wash. This is because AGM batteries are capable of supporting higher C-rate discharges without as much of a draw penalty. I would not hesitate to run AGMs harder to a DoD of ~70-80% in a pinch, as they are generally higher quality just like golf cart batts.

AGMs from any of the major brands will work great. They generally run 60-70% more cost than flooded lead acids.

Personally, I'd spend the money on doubling the size of you solar. May even be cheaper to do that if you can DIY.
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Old 07-22-2019, 06:44 AM   #10
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Hi

There *is* data out there on depth of discharge and battery lifespan on lead acid batteries. You are very much trading off the number of cycles before they die vs the depth you cycle them to. That may be fine in one case and problematic in another.

We talk a lot about "lasts for X years". Indeed there are a few things that scale by years. The biggest issue with batteries that actually are used is the cycle count. If you only go camping for 30 days a year and maintain the batteries in storage, you might rack up 5 full cycles a year. Going from an 800 cycle life to an 80 cycle life in that case is not a big deal. You still would see > 10 years of cycles.

The flip side is somebody who really uses things hard. Some people seem to go through a full cycle every day or two when out camping. They also seem to camp 90 days a year. That
can get them into the 60 cycles a year range. Now, your "10 years" on cycle life is at 600 cycles. That *is* indeed in the range that 50% vs 80% *will* impact pretty hard.

Lots of variables ....

Bob
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Old 07-22-2019, 07:55 AM   #11
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I got 9 years out of the last set of Lifelines with the lousy AS electronics. I bought the same kind again, and hopefully they will last as long with better electronics. I boondock 3 weeks at a time, but my 12v side is never plugged into an AC charger. It charges from solar only no matter what the conditions. Sun shade summer or winter. I have yet to run out of power boondocking.

I've got 300 watts of solar with a cheap PWM controller. I did upgrade the wiring from the factory wiring that came with the 2 50 watt panels.
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Old 07-22-2019, 12:58 PM   #12
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Quote:
Originally Posted by uncle_bob View Post
Hi

There *is* data out there on depth of discharge and battery lifespan on lead acid batteries. You are very much trading off the number of cycles before they die vs the depth you cycle them to. That may be fine in one case and problematic in another.

We talk a lot about "lasts for X years". Indeed there are a few things that scale by years. The biggest issue with batteries that actually are used is the cycle count. If you only go camping for 30 days a year and maintain the batteries in storage, you might rack up 5 full cycles a year. Going from an 800 cycle life to an 80 cycle life in that case is not a big deal. You still would see > 10 years of cycles.

The flip side is somebody who really uses things hard. Some people seem to go through a full cycle every day or two when out camping. They also seem to camp 90 days a year. That
can get them into the 60 cycles a year range. Now, your "10 years" on cycle life is at 600 cycles. That *is* indeed in the range that 50% vs 80% *will* impact pretty hard.

Lots of variables ....

Bob
In the real world, everything has a life expectancy.

Like the owner that buys a Corvette to putter around. Never using the capability they paid a premium for. Afraid that every time they step on the gas, it wears it down a bit more.

Why buy a Corvette when a Camry would have done the job?

No need to instill fear to using a battery. AGMs are well and capable to discharge beyond 50%. It's not going to be the nominal case, especially with solar anyways. Rather the rare occasion which will not tax a battery in the least.
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Old 07-23-2019, 06:50 AM   #13
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Originally Posted by pteck View Post
In the real world, everything has a life expectancy.

Like the owner that buys a Corvette to putter around. Never using the capability they paid a premium for. Afraid that every time they step on the gas, it wears it down a bit more.

Why buy a Corvette when a Camry would have done the job?

No need to instill fear to using a battery. AGMs are well and capable to discharge beyond 50%. It's not going to be the nominal case, especially with solar anyways. Rather the rare occasion which will not tax a battery in the least.
Hi

Indeed it's very much a *that depends* sort of thing. If "rare" means once in the life of the battery then indeed it will have little impact. If "not tax in the least" means less than 10% damage then indeed that fits as well. Since nobody ever actually *measures* their batteries for capacity they really don't know what condition they are in.

It's important to understand just what does wear out a battery. There are a lot of people out there getting two or three years out of a set. That's not because the batteries were defective. It's because of something they did.

Bob
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Old 07-23-2019, 07:46 AM   #14
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Quote:
Originally Posted by Danny Z View Post
Hi all, I've read several threads on here and know there is a lot of debate on this subject, but I am mainly looking for contemporary opinions on the issue of a quality AGM battery that won't break my bank (no pun intended). All the articles I found on line are thinly veiled marketing ads for a specific battery, and many of the threads on here are a few years old already.

My setup: I have 200 watts of solar with a MPPT controller, a "freedom" 1800 watt inverter/charger that is compatible with AGM batteries, and currently (2) 6 volt excide GC-135s joined in a series. I want to switch to AGM Batteries for maintenance reasons and am committed to this plan. I boon dock for a week at a time (with a backup generator I only use if necessary) and mostly am using the batteries and inverter to recharge my two electric bike batteries (36 Volt systems). I am looking for something affordable, maybe something like the Odyssey PC680 Battery for around $130 each.
Thoughts???
Should I get two and then run them in parallel? How would this compare to my old set up (amp hours wise)? I know I won't be starting any motors with my set up, but because I will be using my inverter a decent amount, should I consider a dual purpose battery???
Looking for wisdom here with the components I already have.
Thanks
Hi Danny,
First I will say that I love my AGM's I have 4-Lifeline GPL-4CT (6-V, 220 ah) batteries that I have used for 7+ years with zero issues with multiple charge cycles. The battery you listed seams a little small in size as well as (ah 16). I would find a size that fits the space you have and get the most ah (amp hours) as possible for that space.
7 or 8 years ago AGM's were the best choice for me as the Lithium Iron Phosphate were still un-proven technology. However today if I were to start over or I had to replace my AGM's I would think about building my own Lithium batteries. Still twice the initial cost of AGM's but the life span and usage profile are far superior and make the Lithium's much more cost effective than AGM's over time. Here is a cool link to building your own.
https://www.mobile-solarpower.com/de...o4-system.html
Check our the other thing on the website also pretty cool.

-Dennis
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