AGM battery recommendations

I'm narrowing down on my solar needs, I think I'm going to go with the 200w renology kit that rvbob has recommended because it seems pretty reasonable in price, and this is all new to me. Now I need to figure out which battery to buy.

I don't have space outside for the battery, so it will live under my bed, which means an AGM for safety.

For ease of mind it makes sense to just go with a single 12 volt 200ah AGM battery, such as this http://www.amazon.com/200Ah-Sealed-...=1428090766&sr=8-6&keywords=AGM+12+volt+200ah

Is there any advantage to getting 2 6 volt batteries instead of a single 12 volt? (Other than size and weight)

If I get 2 6 volt should I look for 100 ah batteries (I assume that 2 100ah batteries add up to a total of 200ah, yes?)

Does anyone have any specific recommendations for AGM batteries that have worked well?

Thanks

My concerns are that a lot of people use trickery to get real numbers but aren't what we all mean.

The bottom line is batteries need a certain amount of lead to store a certain amount of power. A 200 ah 12 volt battery should still weigh about 120 pounds or they are deceiving you. The battery on Amazon weighs 120 pounds. It's probably an 8D and I've owned one 8D and swore I would never own another. First time you pick it up and move it, I think you'll swear also.

I'd get golf carts! It's a lot easier to pick up a 60 pound battery one at a time than two at once. I've had good luck with my Full River AGM golf carts but they are expensive, $250 each. You can save a lot of money with flooded and building a vented box.
Bob

If you are set on an AGM, please read the following:

http://forums.sbo.sailboatowners.com/showthread.php?t=124973

If premature failure is not that big a deal, I would still recommend two smaller batteries in parallel.

TOP DOG agm is Lifeline and they want minimum 20 amps per 100 ah of capacity charge current when deeply cycled

Odyssey and Northstar should also be fed hi recharge rates when cycled deeply. Odyssey says 40 amps per 100AH of capacity minimum.

Batteries+ rebadges NorthstarAGM as X2power

So these do not make good solar only batteries.

Trojan makes an AGM
US battery make an AGM
EastPenn Deka make an AGM. A Deka intimidator is rebadged as Sears die hard gold AGM. Sears Diehard platinum is a rebadged Odyssey, but not for much longer.

There are the Asian AGMs available too, which of course are cheaper.

Universalbattery is the predominate Asian AGM we see in North America. These are rebranded by dozens of labels.

The less pricey AGM's do not have some of the desirable attributes of higher$$ AGMs, like very low self discharge and ability to accept high recharge currents and hold higher voltages under heavy loads. Granted these attributes are not really required in a vandwelling existence.

many of these lower$ AGM batteries cannot be fed with more than 30 amps per 100 AH of capacity.
The voltages the battery be brought upto and then held for X amount of time, to attain full charge, also varies widely among AGM's so charging sources need to attempt to meet these requirements

Any battery you buy should be a fresh battery from a battery distributor who moves a lot of batteries. Buying internet batteries has the risk of old batteries arriving that have already lost a portion of their capacity, and then there is the shipping.

So how much you expect from your agm battery, any battery, is directly related to how well it is recharged.

The BEST battery available treated poorly will fail before the worst constructed battery treated well.

Treating a battery well can be taken to extremes, and not make financial sense to do so.

Make your batteries work for you, not the other way around, but setting this up to yield acceptable performance in the first place, is not just a matter of slapping any charging source on any battery.

""If I get 2 6 volt should I look for 100 ah batteries (I assume that 2 100ah batteries add up to a total of 200ah, yes?)"" No. Two six volt batteries connected in series will give you 12 volts at the amp hour rating of the six volt battery. Most six volt deep cycle batteries are in the area of 220 amp hour. So two 220 amp hour six volt batteries in series will give you 220 amp hours at 12 volts.

Unfortunately with my setup it really isn't possible to vent a box to the outside, and I'm also wary of sensitivities and allergies so I think the cheaper flooded batteries are out of the question. Rvbob can you explain what 8d means? The big ones are pretty heavy, but once it's in place what would be the need to have to move it? From a price standpoint it's much cheaper to get a single 12v agm for $360 than 2 6 volts at $250 each.

Here's some links to show some comparative prices.
An 8D Lifeline (165lb, 255AH 12V high quality AGM battery) sells for $640.
A 4D Lifeline (135lb, 210AH 12V high quality AGM battery) sells for $540
http://www.batteryplex.com/lifeline.cfm

A Chinese 8D (167lb 250AH 12V) is $435
http://www.batterystuff.com/batteries/upc-telecom/UB8Dagm-45964.html
A Chinese 4D (123lbs 200AH 12V) is $355
http://www.wholesalesolar.com/products.folder/battery-folder/upg-ub-4d.html

Yes, it is cheaper to go with a single 12v AGM than 2 6V AGMs of equivalent output.

Chip

Considering that keeping the AGM battery charged properly etc I'd have to think that the cheaper Chinese would be a better choice.

The LINK that SternWake posted is a must read! It's a bit techy at times but if you take the time to read and then ask questions you will be much better informed to making the best choice.


To clarify using one or more batteries and capacity. 

When connecting two or more batteries in SERIES of the same capacity the TOTAL capacity will be equal to one of them. 
Therefor taking two GC batteries at 6 Volts 225 AH rating will yield 12 Volts 225 Ah. 

When connecting two batteries of the same capacity in PARALLEL  the capacity will be added up. 
Therefore taking two 6 volt 225 Ah GC batteries will yield 6 Volts and 450 Ah. 

Make sense? 

I just want to add that I thought I had made a good choice when I purchased a Sears Die Hard AGM starting battery. This is a battery manufactured in the US and see's duty in out military.

I don't think that I did make a good choice and I spent more than I needed to. Why?
One because the charging systems in my 2007 Ford E-150 does not meet the needs of an AGM battery!
Two because I leave my Van sit for a week at a time with no use.
Three because I have let it (unintentionally) go flat and I mean KAPUT a couple times now.

It's three years old and I may get a little credit if I go back to Sears. IF!
It starts my van fine right now and I routinely pull 10 to 25 AH out of it every Saturday and Sunday(it's a power source for low voltage battery chargers) then drive it back home for about 30 minutes..

After leaning what I have in the last few months it will be replaced with a FLA type battery that I can check with a hydrometer and maintain with a moderately priced battery charger.

Sorry for being a bit off thread here. Thought it might be of interest. 

Mike R

Yes the Sears Diehard Platinum is a Rebadged Odyssey, and while an excellent AGM battery, they require huge initial charging currents when depleted, and then be held at 14.7v for 4 hours or until current to hold 14.7v drops below a certain threshhold.

It is an expensive battery to not at least come close to the manufacturer recommendations.

I have a Northstar AGM, which is very similar to Odyssey in construction. I can notice when it is not fed High recharge currents when depleted, it does not have the same gusto when starting the engine, which is its main duty.
If I only take 10AH from it and recharge it from there it does not regain that gusto.

When I take it down to 50% then recharge it at 40 + amps until 14.7v is reached and held as amps taper to less than 0.4a, then all that impressive engine starting gusto is back. If I do not have a high amp charging source available, I will not discharge My AGM battery. My 200 watts of Solar is much too little current, despite it easily being able to replenish the amp hours used if i were to deplete it to 50%.

There are lots of reports of people buying these high$$ AGM and expecting incredible life from it despite not meeting the manufacturer recharge recommendations then blaming the battery. To me this is like buying a New expensive car, never changing the oil, then blaming the car maker when the engine seizes, saying such an expensive car should just not need such attentions, merely because it was expensive.

Flooded batteries appear to be more tolerant of improper/incomplete charging and are much less expensive to boot.

The name 8d is just a universal designation of a battery size. It literally is the size of two batteries in one case. I don't know the background of the name. It's commonly used in almost all very large diesels like construction equipment and semis.

I wouldn't want one, too big. But it's a personal decision, I know smart people who prefer them. Lot's of times they are labeled as deep cycle, but I question that. I suspect they are marine batteries (a hybrid of starting and deep-cycle battery) and not true deep cycles. I'd only be certain if they were a trusted brand like Lifeline and they are too expensive for me to consider.

You're wise to worry about allergies. I have a friend with allergies and she bought a pair of flooded wet cell golf carts and put them in a box. She didn't get home before her nose stuffed up so she turned around, returned them and got AGMS and has never had a problem since.

if you're like most people, you're going to wreck your first battery bank. It makes sense to buy cheap and get the most bang for your buck. When you replace them you won't be so sad!
Bob

AGM's tend to be heavier than their flooded counterparts too, yet also tend to have lesser capacity ratings.

My group27 AGM is ~ 12x7x8.5 inches, rated at 90 amps hours, and weighs 74LBS
My group31 Flooded is ~13x7x9.25 " rated at 130 amp hours , and weighs 65.5 LBS

2 flooded batteries of the same size, the heavier one will be a better battery in a deep cycle application.

Cant really directly compare AGM to flooded in the weight department.

I just heard Costco has a group 31 AGM for 169$ and it is an EastPenn Deka intimidator, rebadged to a duracell or energizer battery.

A good deal on a good AGM from a respected manufacturer.

Internecting cables for paralleling two of them are hardly bank breakers.

From here:
http://www.genuinedealz.com/custom-cables/custom-battery-cable-assembly

Two one foot long interconnecting 2 awg cables of the highest build quality and components are 18$ delivered

Even an 8d under a bed needs to be properly fastened to the floor. Properly Fastening two group 31s is no more difficult.

If the 8d fails, you are screwed. If one group31 fails, you still have one left.

I understand the desire for one large battery instead of two with interconnecting cables.

But it comes at a cost.

Good grief! I had no idea AGM batteries weighed so much! I'm trying to keep the weight down in my tiny, underpowered little Transit Connect, but that's not going to be possible with those monsters!

Weird, my Lifeline GPL31XT AGM are rated at 125AH and are only 74 pounds.  What brand is it that weighs 79 pounds at only 90AH?

Lifeline batteries are built like Mil Spec tanks.

IGBT said:

Weird, my Lifeline GPL31XT AGM are rated at 125AH and are only 74 pounds.  What brand is it that weighs 79 pounds at only 90AH?

Lifeline batteries are built like Mil Spec tanks.

Click to expand...

I did not realize Lifeline had 2 versions of a group31 battery.  The GPl-31T only claims to have 105AH, and weighs 10Lbs less than the XT version rated at 125AH capacity.

I have the highest respect for Lifeline AGM and believe them to be absolute best AGM in deep cycle applications, and their price matches this.

Their CCA ratings, not important in deep cycle applications, except perhaps those powering huge loads and are worried about the low voltage alarm on the inverter,  are not really important.

The Lifeline 31 AGM are rated at 600 CCA for the 105 AH version and 650 for the 125Ah version.  They also have the thickest positive plates in the AGM world, and this an indicator of how well a deep cycle battery can be expected to last in such an application.  This lesser CCA figure is to be expected of a true deep cycle battery with thick plates.

IGBT I hope you can recharge that battery according to Lifeline's recommendations and they say minimum initial amps are 0.2 of the capacity which for your battery is 25 amps.

http://www.lifelinebatteries.com/manual.pdf

Please scroll down to page 20 for their recommended charge profile.

Odyssey's group 31 only claims to have 100 AH capacity and weighs 77.8Lbs, but has a rather astounding 1150 CCA.

This battery requires a minimum of 40 initial amps to recharge when deeply cycled

NorthStar, which is very similar to Odyssey, and the AGM brand I own, their group31 also claims to have 1150 CCA, 102AH and weighs 76lbs

And I apologize, my group 27 weighs only 68 LBS, not 74 as I previously typed. It has 91AH capacity and 930CCA.

Both Northstar and Odyssey tout their thin plate pure lead technology.  They probably make for a better dual purpose battery than Lifeline, and if drawn down to the same state of charge, likely have more ability to crank an  engine fast enough to start, but this is a guess.

My Northstar AGM has a fully charged resting voltage of 13.06 volts.

Odyssey claims to have a fully charged resting voltage of 12.84 volts

So while there are similarities between Northstar and Lifeline, there are some differences too.

I don't think my Northstar is superior to Odyssey, but Northstar's list of approved chargers is larger, and this influenced me to go with NS.
however i found that it does not enjoy the Low and slow Solar recharge.

I spoke at length with an Odyssey engineer about their group31s ability to behave  when primarily recharged by my 198 watts of solar.
  He recommended against it, as the plate material was too dense and compressed too tightly for lesser amperages to feed them properly in a deep cycle application, and I would not get my money's worth.

He recommended against any AGM for my intentions, and my observations have proved this to me.  My Northstar simply loves huge charging currents.  It holds higher voltages during discharge when it is fed at 41 amps, compared to a maximum of 10-13 amps for a longer period.

So I use it mostly as my engine starting battery, a duty in which I find it to be impressive, but I am not afraid to cycle it, as long as I have 30+ miles to drive, or have grid power so my 41 amp power supply can feed it properly.


The OP should be aware that AGM's can offgas if overcharged, and flooded batteries offgas only during charging at higher states of charge, from about 75% to 100%, and do not offgass during discharge.  if ventilation is adequate during charging at high states of charge, offgassing is much less of a concern, and not a concern during discharge.

VW vanagon enthusiasts place flooded batteries in their passenger compartment and most all Skoff at the possible dangers of doing so, and few even consider it as an issue and get quite defensive if the issue is brought up on 'the samba' forums.

I'll not tell you it is safe, but the dangers might be overblown.

Technically, AGMs need to vented as well to be completely safe.

Yes, I am aware that my Lifeline AGM want a hefty charging current.   I feed them 40 to 50 amps during bulk charge but could go as high as 125 amps.

It is one reason  I have 1080 watts of solar.

I plan to work them pretty hard, draining down to 50%.   Lifeline tells me to expect about 1000 cycles or three to four years.   That sounds fine to me.

Can someone elaborate a bit on what the initial charging amps ratings mean? It sounds like some batteries require more amps to charge than others, which could be an issue if only charging off solar (maybe too low?)

Also, I'm wondering if most people have their batteries hooked up to both solar and the alternator to charge, or if it's common to just use solar. Thanks

I can verify that Lifelines do not hold up well when just charged by a small solar array. A friend bought two Lifeline AGM 12 volt deep cycle and charged them with his 200 watts of solar. After just a year they wouldn't hold a charge and he didn't abuse them.

He called Lifeline and asked for warranty service. They asked if he bought them at the same time and he said no, they were 3 months apart. They said that voided the warranty and they couldn't help him. They did say to take it to the nearest dealer (100 miles away) and get them equalized. He did and that brought them back to a very good state. Only time will tell for how long they stay good.

I'm sure it's exactly what Sternwake is talking about, my friend isn't charging them fast enough and so they failed prematurely.

I think the lesson is don't buy AGMs for solar only charging. Except I have Full River AGMs charged only by 195 watts and they are like new after 3 years. Maybe the lesson is don't buy LIfeline, buy the cheap Full River instead.
Bob

marigold said:

Can someone elaborate a bit on what the initial charging amps ratings mean?  It sounds like some batteries require more amps to charge than others, which could be an issue if only charging off solar (maybe too low?)  

Also, I'm wondering if most people have their batteries hooked up to both solar and the alternator to charge, or if it's common to just use solar. Thanks

Click to expand...

A depleted battery can accept very large charging currents from a high amp plug in charging source, or an alternator.  Battery manufacturers tend to assume these will be the charging sources used, and their recommended charge profiles are for the plug in charger.

Trojan battery recommends that their depleted battery be charged from depleted at a 10 to 13% rate.  10 to 13% of the battery capacity, or a minimum of 22 amps for their golf cart batteries in series that are rated at 220 AH.

At the other end, Odyssey recommends a minimum of 40% be applied to their depleted battery, and this is 40 amps for a 100AH battery

I do not know how much an Odyssey's cycle life would be shortened by recharging at a much slower rate, but with the rather extreme price paid for their batteries, I would not want to find out.

As the battery charges, its voltage rises toward the Absorption voltage.  As the voltage rises to this maximum allowed voltage of the charging sources regulator/controller, the amps will taper.  The higher the state of charge of the battery, the less amps are needed to hold it at these absorption voltages.  When the amps taper to very low levels the battery can be considered fully charged and automatic charging sources drop to float voltages, which require much less amperages to maintain.

Different battery manufacturers have different recommended absorption voltages, and these are listed for when the batteries are 77F degrees.  Higher ABSV's are needed at lower temps and lower ABSV's at higher temps.

Meeting this ABSV  for a certain amount of time is important, not just for maximizing battery life, but for preventing premature failure.  If a battery never gets high enough, for long enough, premature failure will happen.  How premature it fails is the unknown variable with many contributing factors.

Since Solar is not an instant type of charging source when the sun rises, but ramps up slowly, peaks and then lowers throughout the afternoon, the recommended charge profiles cannot be matched.  However it is wise to at least have the minimum recommended rate be approached at Noon in the summer.  This is closer to a 2 to 1 ratio than the usually recommended 1 to 1 ratio.  1 solar watt per 1 AH of storage.

The higher the ratio the happier the battery when deeply cycled day after day.  When not deeply cycled, but shallowly cycled to say 85% then this ratio becomes less important.

Lower$ AGMs tend to recommend charging rates not exceed 30% or so.  These AGMs are likely much more suited for a Solar recharge regimen.

The recommended rates by battery manufacturers are quite helpful when deciding what Amperage plug in charger to buy for the battery capacity, but they are not so helpful when the charging source is to be solar.

My personal experience has shown that  for best battery longevity, it is not merely about replacing the amp hours used plus a little more, but having a higher charge rate available by the sun to get the batteries up higher quicker in the day.  While My underbody battery box is capable of holding two group 27 batteries for 230AH of capacity, and did so for 3 sets of batteries, after the last set of 27s failed, I replaced them with a single group31.

While I am cycling this single 31 battery deeper than two 27's in parallel, it is being recharged at a higher rate via my solar, which is my primary charging source, and I am already ahead on the $/cycle ratio, and I have never come close to not having enough battery capacity. 

My previous 27s likely could have benefitted from higher absorption voltages, and more frequent equalization cycles, but they were a PITA to access the cells to check specific gravity, and electrolyte level, and the level was a contributor to their earlier demise as I let it get low on two sets.

One can surely set up a house battery system so it need not ever hook to the alternator, but then it is more important to have a higher solar wattage to battery capacity ratio.  On a cloudy day, an alternator can replace in 15 minutes what would take the solar all day to do.

Wiring up a solenoid to charge the house batteries I know seems quite complicated to 12v newbies and i know not needing to do this is quite desirable, but I recommend against it, as the alternator is very capable of returning a battery to 80% charged quite quickly when properly cabled to the house bank, and can and will greatly extend its longevity and can be much more a reliable system.

One can always add a solenoid and cabling at a later date. If one wires up their own solar system, then they will see that pulling power from the alternator is no more complicated than that.

Again, one need not strive for absolute battery charging perfection, but achieving acceptable battery longevity also require that some minimums are met.  Reaching Absorption voltage and maintaining it for long enough for the battery to get to the 95% range, as often as possible, need not be complex or complicated.  Just get as much solar you can afford and fit on your roof, and do not get too much battery capacity for this amount of solar.  If other charging sources are also to be incorporated, and regularly applied, then the solar wattage to battery capacity can be lowered.

It is quite difficult to have too much solar when one is deep cycling their batteries daily, but it is quite easy to have too much battery capacity for ones amount of solar.

Ok, so for 200w of solar, maybe I should be looking for a 100 or 150ah battery, if I plan to just use solar for charging?

Is it easy/possible to overcharge an agm battery using the alternator?

When you talk about deeply cycling a battery, this means running it down to its low capacity (50 percent ish) and then back up towards 100, as opposed to using just a little bit battery power before recharging?

Getting the cheaper agm is fine by me, I like this advice!

I appreciate all the detailed info, I'm starting to get a grasp on it, thanks.