House Batteries, AGM vs gel?

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House Batteries, AGM vs gel?

April 19, 2019, 05:16:02 pm

Our 3 MK, model 8G8D batteries are nearly 9 years old and no longer holding a charge well so I think I need to replace them soon. I've been looking for new ones online (batterystuff.com) and am surprised that their MK, model 8A8D (AGM) batteries are about $38 cheaper than their gel batteries. Also, their AGM batteries weigh about 7 pounds more. This seems counterintuitive to me as I always thought that AGM's were better and costlier than gels. Are there any reasons why I shouldn't I replace my gel batteries with the AGM type?
As a side note, I'm using 3 Optima AGM starting batteries in my coach.
Thanks, Robert

Re: House Batteries, AGM vs gel?

Reply #1 – April 19, 2019, 05:43:10 pm

You will hear a variety of opinions, but from everything I've read AGM is the superior technology for our use. I will be replacing my AGMs with the same technology whenever the need arises.

Re: House Batteries, AGM vs gel?

Reply #2 – April 19, 2019, 05:45:04 pm

Discharging either type of battery to 50% of its capacity is considered the maximum discharge. Continuous deep discharging like that leads to the shortest possible battery life. In very deep discharges the gels might have a few more percent cycles before they are useless. If you only discharge to 75% of total capacity the total number of cycles available are very similar. The battery technology has changed a lot since your coach was built and had gel batteries a original equipment. AGM batteries today have slightly more total capacity. Gels have some other characteristics that some find attractive.

Either would be a good choice. How you ue your coach might tip the teeter totter a bit one way or the other. AGM batteries may be easier to find and perhaps less expensive. I am sure you will get more opinions.

Shop around. Many get good batteries at O'Rileys. A FMCA Diesel Powerclub membership will save you more than it costs.

Re: House Batteries, AGM vs gel?

Reply #3 – April 19, 2019, 05:53:06 pm

Here is a good read for AGM vs. Gel Batteries. According to the article, AGMs outsell Gels 100 to 1. I've always thought the Gels were more prone to damage from incorrect charging.

BatteryStuff Articles | Compare and Contrast Between AGM and Gel Batteries

Pierce

Re: House Batteries, AGM vs gel?

Reply #4 – April 19, 2019, 06:17:06 pm

Quote from: Roger & Susan in Home2 – April 19, 2019, 05:45:04 pm

Many get good batteries at O'Rileys.

X2 on O'Reilly AGM8D

https://www.oreillyauto.com/detail/b/fleet---heavy-duty-5000/battery-accessories-16452/deep-cycle---marine-batteries-17354/220f7dcd7121/super-start-fleet-heavy-duty-group-size-8d-top-post-battery/agm8d/4742645

Re: House Batteries, AGM vs gel?

Reply #5 – April 19, 2019, 09:34:20 pm

Why don't you get the Fire Fly carbon foam batteries and let us all know if they are as good as claimed.

Re: House Batteries, AGM vs gel?

Reply #6 – April 19, 2019, 10:41:14 pm

Rob and Di, I too am looking at the Baterystuff.com site for the MK, and posibly the Oriellys for lower initial (not overal) expense. I thought you'd appreciate the following.

Best in detailed information by East Penn regarding depth of discharge follows, by both the mfg of orig BK gel used in FT and also the mfg of the Oriellys agm. (see attachment)

I especially liked the following depth of discharge vs life of each agm and gel. Watch the lovers of AGM come out of the woods. I'm too a "lover" of AGM. Gel just fit RV use better, it is in the "facts", not just campfire hear say. I've also heard this from wheel chair mfg that recommended the gel over the less expensive agm.

Typical* VRLA Battery Cycling Ability vs. Depth of Discharge. East Penn
Typical Life Cycles (this chart is from 2007, and is approx the same as the two current brochures from 1/2016 downloaded 4/2019, see update column)
Capacity Withdrawn / Gel / AGM. From 2016 Gel / AGM. Brochure
100% 450 150. 450 200
80% 600 200. 600 250
50% 1000 370. 1000 500
25% 2100 925. 2100 1100
10% 5700 3100. 5700 3100

......and if your budget permits, and temperature use permits, your use demands:
And Victron lifepo4
CYCLE LIFE (capacity ≥ 80% of nominal)80% DoD2500 cycles70% DoD3000 cycles50% DoD5000 cycles.

And Battle Born lifepo4
Battle Born claims 3K cycles at DoD at or below 50%, increasing that to ~5K cycles with shallower DoD; while still retaining 80% capacity.

Life Blue claims 2.5K cycles to 100% DoD, and increases that to 6K cycles if DoD is kept below 50%; also while retaining 80% capacity.

Plugged in most of the time, or have adequate solar and conditions, buy the Oreillys AGM.

Boon dock mostly, definitely look at other options.

Since I know not my use or demands, I am leaning towards Oriellys AGM or MK gel.

I've owned multiple sets of Lifeline AGMs, respect their place, never wore out a set, are no longer for me now, as I look at my posible needs, the price of the Oriellys, and the the price of the MK.

https://www.oreillyauto.com/search?q=Agm8d

8G8D | MK Battery 12v 225 AH Deep Cycle Gel 8G8D Battery

Re: House Batteries, AGM vs gel?

Reply #7 – April 19, 2019, 11:31:21 pm

There is a new player in the Lithium game, but a very established manufacturer of deep cycle lead acid batteries. Trojan has three new entries, two 12 volt and one 24 volt. Their cells are made in China, but Trojan claims to be overseeing the quality control. They are calling them Trillium.
They are claiming a life of >5,000 Cycles @ 80% DOD
Trillium | Trojan Battery Company
The 12 vdc options are 110 AH and 92 AH. It will be interesting to see how that plays out. Not cheap, to be sure, but maybe a sign that the technology is finally going mainstream. But to bring this back on topic, I think if I needed batteries right now, I would go for the O'Reilly 8D AGM house batteries with the idea that they will last until the lithiums are more common place and there for more affordable. Lithium battery chemistry is now the cycle life leader in products you can actually buy, but there are other things on the horizon which may blow it away. But when? I bought my four O'Reilly 8D AGM's almost four years ago. They are still going strong, seldom having been discharged below a SOC of 80%. I expect they could easily go another four years or more, but I really thought there would be more good options by now. That is okay, I can wait...
Don

Quote from: Jack Lewis – April 19, 2019, 10:41:14 pm

...And Victron lifepo4
CYCLE LIFE (capacity ≥ 80% of nominal)80% DoD2500 cycles70% DoD3000 cycles50% DoD5000 cycles.
And Battle Born lifepo4
Battle Born claims 3K cycles at DoD at or below 50%, increasing that to ~5K cycles with shallower DoD; while still retaining 80% capacity.
Life Blue claims 2.5K cycles to 100% DoD, and increases that to 6K cycles if DoD is kept below 50%; also while retaining 80% capacity.

Re: House Batteries, AGM vs gel?

Reply #8 – April 19, 2019, 11:55:04 pm

Every Unicoach made had mk gels in it. Every one.

Gels are not damaged from incorrect slow charging and cycling them before being fully recharged.. Agm's, if not charged at 1/5th of capacity, sulphate their plates. ONLY Lifelines can be equalized. The others cannot.

Once damaged they are not restore able. Maybe with a desulfurization device over long run?

Batteries labeled "gels" may or may not be "gels" some sellers think agm's are "gels.

If you are perfect and fully charge your batteries without fail at 1/5th C or the optional 1/20th C they are ok.

If you do not there lifespan is reduced.

9 years of mk gels should have had a light come on over your head in my opinion.

Better reliability and longest life is more important to some like Foretravel new.

Others are "price" buyers from need or habit.

Whatever makes your tennies squeak.

After 35 years in the rv biz if there are not redtops to start the motor that test well and mk gels or lifeline agm's in the coach I recycle the bstteries and start over. Less hassles.

I did the recycle the batteries after we bought our coach six years ago. I am a man of my word and experience.

The coach IS the 12 volt system FIRST.

Re: House Batteries, AGM vs gel?

Reply #9 – April 20, 2019, 07:33:21 am

The PO of my FT did an excellent job taking care of the 13 year old MK gels! The only reason I changed them is for our Alaska trip. I didn't want to have them go out up in the frozen North since we'll be doing a lot of dry camping. If not for this trip I'd probably have used them longer.

Re: House Batteries, AGM vs gel?

Reply #10 – April 20, 2019, 09:24:15 am

Look at Manufacturers specs for information about life cycles vs depth of discharge and battery capacity.

Coach batteries

There is no reliable evidence for a 3x life expectancy increase for gel batteries vs AGM batteries except maybe for 100% discharges. Treat your batteries well and they will last a long time.

Re: House Batteries, AGM vs gel?

Reply #11 – April 20, 2019, 10:07:47 am

I read lots of claims about gel's longer life expectancy and yet when I review a large body of independent data it always appears as if there isn't any significant difference in the number of normal discharge cycles either one can withstand. I really wish someone would supply a compilation of independent data to support their claims about gel technology.

Re: House Batteries, AGM vs gel?

Reply #12 – April 20, 2019, 11:22:32 am

Quote from: Roger & Susan in Home2 – April 20, 2019, 09:24:15 am

Look at Manufacturers specs for information about life cycles vs depth of discharge and battery capacity.

Coach batteries

There is no reliable evidence for a 3x life expectancy increase for gel batteries vs AGM batteries except maybe for 100% discharges. Treat your batteries well and they will last a long time.

Quote from: Roger & Susan in Home2 – April 20, 2019, 09:24:15 am

Look at Manufacturers specs for information about life cycles vs depth of discharge and battery capacity.

Coach batteries

There is no reliable evidence for a 3x life expectancy increase for gel batteries vs AGM batteries except maybe for 100% discharges. Treat your batteries well and they will last a long time.

Since there was little difference between Roger's two agm and gel charts, I suspected an error. MK is a division of East Penn, and since I will be purchasing batteries from them I went to their site and downloaded current literature. As I expected the chart you posted was incorrect, at 50 % state of discharge, MK and East Penn are showing a difference off 1000 cycles to 500 or double the life for the gel on their current site downloads. At a 25% state of discharge, the difference is 2100 to 1100 for the agm and so on, huge difference. The agm 8d weighs 158 lbs, the gel 166.5 lbs. (These weights are reversed by retailer batterstuff.com)

Please read the attached PDF in my prior post or the ones below, definitely a detailed document from East Penn.

Also it may benefit forum readers to read for them selves the differences to make up their own minds. Also I would read the three attachments that follow, two are from marketing and one is from engineering. Also please remember, I too am a fan of AGMs and am considering buying a set of AGMs. I especially agree with Roger's comment "Treat your batteries well and they will last a long time." Too many RV owner's do not monitor their 12v systems as they should. I, like you Roger, know the importance of this, and do.

FAQs | MK Battery
Especially, I read, before my above comment, "What are the advantages and disadvantages of both types of Sealed valve regulated batteries, and then I downloaded the files below, on the MK manufacturer's website.

The following three files, on the document, are dated, on the two brochures 1/2016 and on the 0139 pdf dated from 2007, interesting to me, the charts are almost identical for state of discharge vs life. (See updated chart on my 1st post)

Re: House Batteries, AGM vs gel?

Reply #13 – April 20, 2019, 01:23:18 pm

Lots of posts here about over ten year service life of mk gels. Mk engineer said he had had lots of Foretravel owners who reported 12 year service life's

The chart jack showed showing overcharging of a mk gel .7 volts resulting in a 60% reduction in service life backs up the statement here to run your alternator at 13.6 volts at the batteries.

As most here's alternator is not ttemp compensating its it voltage during hot weather running down the road and heating the batteries anything higher than the 13.6 would be seriously overcharging the engine batteries.

At 13.6 it's overcharging already just not as much.

Float at 77 degrees on mk gels House are 13.6.

Probably why Foretravel has equipped every unicoach made with spiral wound Optimas.

They can take an overcharge better than most batteries and can handle the vibrations and heat from/the engine.

Re: House Batteries, AGM vs gel?

Reply #14 – April 20, 2019, 01:58:40 pm

Jack, look again. Both of the upper charts in my post are from MK and are from 2015. One chart is for GEL and one is for AGM.

The AGM chart you are referencing are from 2012. MK AGMs appear to have improved.

FullRiver AGM Batteries go well past 2000 cycles at 25% depth of discharge. Better warranty. That is why I bought them.

Everybody gets to read whatever they want, interpret however it suits them and select what they think is best.

Just because FT put in a GEL battery 15-20 years ago (it might have been the best choice at the time) that doesn't mean it is the best choice for some one today. How you use your coach, what equipment you have installed and your time horizon have a lot to do with your choice.

Re: House Batteries, AGM vs gel?

Reply #15 – April 20, 2019, 02:09:35 pm

I just want to remind all concerned that AGM, Gel, and flooded all use the same chemistry. The only difference is how the electrolyte is stored. Well, that and the AGM batteries are considered starved electrolyte because they only have 95% of the, we'll call it electrolyte for aguements sake, electrolyte to fully charge the battery preventing overcharging and internal corrosion.

Re: House Batteries, AGM vs gel?

Reply #16 – April 20, 2019, 02:35:26 pm

Quote from: Roger & Susan in Home2 – April 20, 2019, 01:58:40 pm

Jack, look again. Both of the upper charts in my post are from MK and are from 2015. One chart is for GEL and one is for AGM.

The charts you are referencing are from 2012. MK AGMs appear to have improved.

FullRiver AGM Batteries go well past 2000 cycles at 25% depth of discharge. Better warranty. That is why I bought them.

Everybody gets to read whatever they want, interpret however it suits them and select what they think is best.

Just because FT put in a GEL battery 15-20 years ago (it might have been the best choice at the time) that doesn't mean it is the best choice for some one today. How you use your coach, what equipment you have installed and your time horizon have a lot to do with your choice.

My brochures both show 1/2016 on the documents, your agm 2015 and the gel (which is the same as mine) 2017. So my 2016 agm brochure replaced yours from 2015. This is not yours or my errors, but web misinformation, which we all need to watch out for. All need to do their own research and then spend the $$$.

Also I found the weights of the two batteries reversed from the retailer batterystuff.com and the mfg, East Penn., I tend to trust the mfg, but who knows, more web misinformation. I remember years ago taking a scale with me to shop for batteries, after being surprised how light Trogen AGMs were compared to Lifeline.

Re: House Batteries, AGM vs gel?

Reply #17 – April 20, 2019, 02:48:54 pm

Quote from: Roger & Susan in Home2 – April 20, 2019, 01:58:40 pm

Jack, look again. Both of the upper charts in my post are from MK and are from 2015. One chart is for GEL and one is for AGM.

The charts you are referencing are from 2012. MK AGMs appear to have improved.

FullRiver AGM Batteries go well past 2000 cycles at 25% depth of discharge. Better warranty. That is why I bought them.

Everybody gets to read whatever they want, interpret however it suits them and select what they think is best.

Just because FT put in a GEL battery 15-20 years ago (it might have been the best choice at the time) that doesn't mean it is the best choice for some one today. How you use your coach, what equipment you have installed and your time horizon have a lot to do with your choice.

Roger I agree with your prior paragraph, and no mfg. guarantees their data for depth of charge to life. I hope our combined effort to bring out the truth or "facts" makes it easier for others to make an educated decision.

Roger knows my truth. I've only had my RV two years. I have no data, as Roger has on his, on how I will use my RV. Plugged in, boon docking, using solar or camping in the shade, etc. As a forum member, you will have choices, do your research and choose with confidence, based not on hear say from a fire side chat, but on those that have done the research and documented their findings for us to save precious time. If you go thru the previous posts on this subject, on this forum, you will find the experts, like Roger with valuable information.

The in depth of discharge 139 pdf from East Penn is from 2007, with data almost identical to what is in their current 2012 agm brochure and gel brochures from 2016 on the BK website. Both of my brochures I downloaded today from BK web site. Rogers shows it is from batterystuff.com, BK's retailer, from 2015, confusing, yes. These are not yours or my errors, but are web misinformation which we all need to watch out for. All need to do their own research and then spend the $$$. East Penn bought MK in 1995, 24 years ago, whom at that time they were building the batteries for. East Penn Manufacturing | Global presence in all corners of the world

Re: House Batteries, AGM vs gel?

Reply #18 – April 20, 2019, 03:07:21 pm

The mk engineer mentioned pre testing of the plates and a different design plate separators when I talked to him. He thought it might double the cycle life.

Maybe I am wrong but agm's can be damaged from not charging them at 1/5th or 120th C. Or short cycling them.

Gels are not as sensitive to different charge rates and short cycling.

A new Foretravel has 6 mk gel 4D's as far as I know. 1300 amp hours or so and two sealed outback inverters to charge at the 1/5th C rate recommended. 260 amp=20% of capacity

The only AGM'S that are equalizable are Lifelines. A Magnum inverter has a built in specific profile with .2volt lower charge voltage for the bigger and quicker charging Lifeline internal connectors. And the Magnum allows equalization on that profile.

The equalization on the gel profile is disabled as they do not need it.

Lifeline states their AGM'S charge 20% faster because of this construction.

Mk states:

The "acid-starved" condition of gel and AGM batteries protects the plates during heavy deep-discharges. The gel battery is more starved, giving more protection to the plate; therefore, it is better suited for super-deep discharge applications.

Do read the chart jack posted

Re: House Batteries, AGM vs gel?

Reply #19 – April 20, 2019, 03:39:12 pm

Foretravels still use Gel Cell house batteries.
Liberty Coach, Marathon Coach, and most other Prevost converters, Newell, and Newmar's top of the line, King Aire, use either AGMs or Lithium Ion house batteries.

Re: House Batteries, AGM vs gel?

Reply #20 – April 20, 2019, 05:12:08 pm

MK AGM document is from 2012.

Lots of battery choices out there, choose what you want.

Re: House Batteries, AGM vs gel?

Reply #21 – April 20, 2019, 05:14:10 pm

MK AGM document is from 2012.

Lots of battery choices out there, choose what you want.

Re: House Batteries, AGM vs gel?

Reply #22 – April 20, 2019, 05:47:53 pm

Quote from: Jerry Whiteaker – April 19, 2019, 09:34:20 pm

Why don't you get the Fire Fly carbon foam batteries and let us all know if they are as good as claimed.

Be a guinea pig for the group

Re: House Batteries, AGM vs gel?

Reply #23 – April 20, 2019, 06:16:43 pm

Quote from: bigfoot – April 20, 2019, 05:47:53 pm

Be a guinea pig for the group

Problem with trying something new like the Fire Fly in this case is that it will take a few years to find out the result.

Re: House Batteries, AGM vs gel?

Reply #24 – April 20, 2019, 07:39:04 pm

Let's not forget, FT used the weights of various batteries to equalize the four corner load. If changing over, I'd be checking the weight of each of the proposed change-overs to see if they are close. Otherwise, I'd have the coach 'four corner weighed'.

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