switch to AGM?

tinkerreknit · 02-16-2018, 01:10 PM

I need to replace my flooded cell batteries and I am considering AGM. I've read that AGM's require 14.1 or less voltage. My converter is a 3 stage unit, and it outputs 14.4 V in the middle or "Bulk" stage. Will this significantly harm AGM batteries?
I am interested AGM for the longer lifespan and the faster charging time. Plus, I have gobs of money (haha).
Thoughts on this?

I currently use 2-group 24 batteries. I have a 100W solar panel and a MMPT controller.

Cypressloser · 02-16-2018, 01:56 PM

I have 6 AGM batteries almost 5 years old, I see the voltage going as high as 14.4 Volt on occasion. The concern IMO is the heat that comes with high Voltage since AGM batteries are sealed and can not vent.
Otherwise I love mine, they are pretty much out of sight out of mind, don't need to be installed in a vented compartment and never ever are the cause of corrosion.
If you do go that route do not equalize them as you would other flooded batteries.
My 2cts.

RB19RR · 02-16-2018, 01:58 PM

I have two group 31 AGM batteries from Sam's Club (paid $189 each a couple years ago)

I've been charging at 14.5 volts for near three years with zero detrimental effects. Batteries are still excellent.

Bluepill · 02-16-2018, 02:26 PM

Century recommends 14.6 to 14.8 volts WITH CURRENT LIMITING for deep cycle AGM.

LINK:

https://www.centurybatteries.com.au/...y-charging.pdf

wharfrat48 · 02-16-2018, 02:35 PM

I am in the market to get new batteries as well and am curious as to why you are leaning towards AGM vs flooded? Besides that they are much easier to maintain, I have not been able to find many benefits of AGM over flooded to justify the 2-3X additional cost. My current bank of flooded 6-volts batteries has lasted 6+ years, but I am noticing a decrease in storage capacity. Thanks

tinkerreknit · 02-16-2018, 04:15 PM

Thanks for the responses! I appreciate the input, and you guys taking time to reply.

About a possible switch to AGM the possible benefits to me would be:
Longer battery life in years - my current flooded batteries last 2-3 years and cost ~$100 each. AGM's last several years longer.
They charge faster.
They can dip lower into the charge without suffering damage.

I don't mind the flooded cell maintenance and I have adequate venting, so these aren't considerations.

As mentioned before, I have deep pockets and can spend $$$$ (very much haha!)

larry2c · 02-20-2018, 08:08 PM

If you really have deep pockets go this route - lithium ion

HangDiver · 02-20-2018, 08:12 PM

Following...

NMWildcat · 02-20-2018, 09:33 PM

I am friends with a fella that works at an Interstate battery shop whom I trust. I went with AGMs in my truck years ago due to problems with flooded batteries eating away my fender wells. Problem solved.

So when it was time to replace the two I have in the RV I asked my friend's advise about switching them to AGM also. He advised that it wasn't worth the $$$ for an RV type of application. We mainly boondock and my flooded deep cell batteries last an average of five years for half the cost. So I took his advise.

tinkerreknit · 02-20-2018, 09:43 PM

I went ahead with AGM batteries. I'll install them in a few days.
This was mostly a financial decision, because at 4 years I will break even. After that point, I will save money. And the AGMs should last at least 7 years. Well see..

wharfrat48 · 02-21-2018, 09:18 AM

I'm still looking and evaluating. I had two flooded 6V battery banks (2 batteries/bank) since 2003. Both banks have lasted about 7 years which seems to be about average when researching the lifespan. First set were Trojan T-105s (about $110 each-225 amp hours) and the second set were Duracells (about $90- 215 AH). Most of the research I did recommended a max 50% discharge before recharging for either type. I have not found anything claiming that AGM charges faster, but they definitely "self" discharge slower than flooded (not an issue for me).

I'm leaning towards flooded again, as I just don't see how AGM's can be cost effective for my application (which is almost always boondocking with 200W solar). If price was not an issue, I think Lithium is the way to go (lighter, smaller, higher capacity, lower discharge, etc.). Unfortunately I'm not there yet

Tinker--- are you using 12 or 6v in series? I wonder if that has something to do with the short lifespan of your batteries?

tinkerreknit · 02-21-2018, 09:29 AM

Quote:

Originally Posted by wharfrat48

I'm still looking and evaluating. I had two flooded 6V battery banks (2 batteries/bank) since 2003. Both banks have lasted about 7 years which seems to be about average when researching the lifespan. First set were Trojan T-105s (about $110 each-225 amp hours) and the second set were Duracells (about $90- 215 AH). Most of the research I did recommended a max 50% discharge before recharging for either type. I have not found anything claiming that AGM charges faster, but they definitely "self" discharge slower than flooded (not an issue for me).

I'm leaning towards flooded again, as I just don't see how AGM's can be cost effective for my application (which is almost always boondocking with 200W solar). If price was not an issue, I think Lithium is the way to go (lighter, smaller, higher capacity, lower discharge, etc.). Unfortunately I'm not there yet

Tinker--- are you using 12 or 6v in series? I wonder if that has something to do with the short lifespan of your batteries?

Two 12V in parallel. When I bought the camper there was only 1, so I soon added a 2nd. I stuck with 12V thinking that if I had a problem with one battery. I could still have 12V from the other.

Cypressloser · 02-21-2018, 09:57 AM

I think AGM batteries make perfect for those that want peace of mind knowing their batteries won't die prematurely because they forgot to check the fluid level a few times as it can drop quite quickly in a high use solar setup. Another reason to go with AGMs is they are sealed, don't off gas causing corrosion, they could theoretically be installed under the bed even laying on the side.
I don't think there is a break even point financially compared to flooded GC batteries but the few benefits I pointed out above are huge IMHO.

tinkerreknit · 02-21-2018, 03:13 PM

I've done the flooded cell maintenance for years on many vehicles, so that wasn't a big selling point for me. I've never minded that, this is what most people say is the reason they switched. But yes, the off-gassing, deterioration of my many wire labels, and corrosion of anything exposed were factors. I've always hated the wet condition of everything in the battery boxes.

TitanMike · 02-21-2018, 03:58 PM

Quote:

Originally Posted by tinkerreknit

I went ahead with AGM batteries. I'll install them in a few days.
This was mostly a financial decision, because at 4 years I will break even. After that point, I will save money. And the AGMs should last at least 7 years. Well see..

At my age, longer battery life for twice the cost may not make any sense.

I don't buy long term subscriptions either. I do however still buy green bananas

tinkerreknit · 03-01-2018, 11:06 AM

Quote:

Originally Posted by TitanMike

At my age, longer battery life for twice the cost may not make any sense.

I don't buy long term subscriptions either. I do however still buy green bananas

Got them installed. One of the battery boxes is small, and even though I measured it, I was worried about the group 27 fitting. Worked out and even had a millimeter to spare.
I've got lots of wiring in those 2 boxes, with everything labeled. In the past, the offgassing deteriorated the labels. Shouldn't have to ever label again.

CHICKDOE · 03-01-2018, 07:23 PM

I have to ask. our trailer came with 'maintenance free' batteries. they ae sealed without any caps to add water. i'm sure they are sealed lead acid as opposed to being sealed AGM. the are size 27 and are labelled as deep cycle. I believe they are centennial model dc27mf. I know they won't be deep cycle like the 6 volt deep cycle batteries but they seem to work for us. how would you rate these vs lead acid that require checking the water level vs agm?

TitanMike · 03-02-2018, 01:55 PM

Quote:

Originally Posted by CHICKDOE

I have to ask. our trailer came with 'maintenance free' batteries. they ae sealed without any caps to add water. i'm sure they are sealed lead acid as opposed to being sealed AGM. the are size 27 and are labelled as deep cycle. I believe they are centennial model dc27mf. I know they won't be deep cycle like the 6 volt deep cycle batteries but they seem to work for us. how would you rate these vs lead acid that require checking the water level vs agm?

If they are conventional maintenance free batteries they should still have caps that can be removed so you can check and add water (distilled only) as needed. The maintenance free "caps" are flush with the top of the battery and you need to pry open with screwdriver. A rectangular piece with three individual caps will pop out and you can check electrolyte level. It should only come up to the bottom of the tube that extends down from the cap area.

As you use your batteries, discharging and charging, eventually they will need to have water added, especially if they get warm when charging.

These batteries aren't really "Maintenance Free" and should be more properly named "Low Maintenance".

To answer your last question as to how I would rate the regular "maintenance free" to a similar AGM, the lead acid have always done a great job for me with regular terminal cleaning and "water checking". Never saw the need for AGM's. Maybe I'd use AGM's if I had an off-road 4x4 that spent a lot of time upside down. Then I wouldn't have to worry about the battery leaking it's life fluids.

During warm weather camping my batteries have always lasted several days before charging was necessary. During cold weather they kept the furnace going all night and then I just started the generator after "quiet time" expired. By night fall the batteries were good to go for the night.

If I ever make the change from Lead Acid Deep Cycle batteries it will be to the LiFePO4 Deep Cycle batteries. 100 Amp hour batt only weighs 29 pounds compared to at least twice that for a similar Lead Acid/AGM.

Expensive as heck but good for up to 5,000 charge cycles. That's over 13 years if you discharge and recharge every day of the year.

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