Author Topic: Looking at switching from standard flooded 6 volt Batteries to 2 Volt AGM's  (Read 896 times)

Solar trucker

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I have a 12V battery bank in my RV at present that is made up of 6 - 6 volt (232 AH) US Battery
standard flooded units for a Total of 696 AH...These batteries are approaching 5 years old and are
still operating very well with no signs of deterioration...I'm not adding an excessive amount of distilled
water to the bank yet and they still are working very well with 5 of the batteries almost identical in
resting voltage, and 1 battery only deviates .20 volts from the other 5...
In the back of my mind, I do know that 5 years is pushing it for standard flooded antimony based units!
Economy tells me to use them till they crap out and get as long a service life as I can with them...

They all sit in a home made battery box with good venting but I am getting a little tired of checking the
cells for electrolyte depth and I'm also not fussy on all that exposed lead on top of the batteries at the
terminals, environmentally speaking!
This set up also requires a system of series - parallel connections to achieve my 12V necessary for the RV...

Here's my question:  I'm thinking of going to a set of 6 - 2V Lifeline AGM 660 AH batteries.  That will
give me 36 AH less than the standard flooded 6 volt batteries!  The AGM's will recover faster than the
flooded batteries after a set discharge and the AGM's will also charge better because of the lack of any
parallel cable connections (I think)...Also there is no hassle of adding water and I should get more than
5 years from AGM's...I typically don't go under 90 to 92 % DOD on these flooded batteries (that's
probably why they are still in really good shape after 5 years!

I'm also under the understanding that AGM's have considerably more cycle Life than flooded batteries
The next higher capacity 2V Lifeline battery is 900 AH but they are 30 lbs more than the 660 AH unit and weight is a bit of a concern (not cost) for my choice of the 660 AH unit...Given a similar DOD
percentage with the AGM's, will I miss the extra 36 AH's that I'm presently getting from the flooded units?  I think probably not, but would like an opinion from the battery guru's and the like here on this
forum.
For most of the 5 year service life of my standard batteries, I used a MorningStar Tristar MPPT-60 for
charging, I recently changed the controller to the Midnite classic 150 at the beginning of this (2016)
year...I thought my MorningStar was doing a pretty good job of maintaining the battery bank, but since
switching to the Classic I'm finding a little higher level of resilience to my 6 volt flooded units...Typically
now with the classic I'm seeing at least  .2 volts more in the morning before sunrise as opposed to the
MorningStar, so I am very impressed with the design parameter and algorithms in the classic!
even though I used an absorption phase of 14.8, and 13.4 float, similar values on both controllers, the
classic is doing a better job of maintaining the bank...I also used Temp comp on both controllers but I
feel the Classic is that much better than the MorningStar product, which by the way is a good controller.

I appreciate any and all comments!
1.65 KW-RV 12V system of Sunpower Panels Classic 150 with BTS and WBJR and a Kid-6 x 6V US Batteries, 696 AH FLA-Magnum Energy MS-2812 Inverter, All Interior and Exterior Lights in the RV were replaced with LED's

Ottawa Canada (Summer) - SW Arizona (Winter)

mike90045

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AGM's have exposed lead terminals
AGM's cost at least 2x flooded
AGM's have half the cycle life as flooded
  The only upside you have going to AGM, is you know how to care for batteries, but have to reset your controller for the new AGM voltages.

Stick with flooded, and get 2V flooded versions instead of AGM.  Yes, you still have to check and add distilled water, but you know how to do that already
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Classic 200| 2Kw PV, 160Voc | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph )| Listeroid 6/1, st5 gen head | XW6048 inverter/chgr | midnight ePanel & 4 SPDs | 48V, 800A NiFe battery bank | MS-TS-MPPT60 w/3Kw PV

zoneblue

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Nah id go the other way. On a RV flooded batterys are a bit of a pain. The real benefit of AGM batterys is they can take higher charge and discahrge rates. But for an RV/motorhome wieght and volume are up there in terms of criteria. For all of the above reasons theres only one logical next more, wait until the FLAs die, then go straight to LFP.
6x300W CSUN, ground mount, CL150Lite, 2V/400AhToyo AGM,  Outback VFX3024E, Steca Solarix PL1100
http://www.zoneblue.org/cms/page.php?view=off-grid-solar

Solar trucker

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Mike I welcome all advice and I do agree with you that AGM's are at least twice the price of flooded units..I'm a little confused about the exposed Lead Terminals and the cycle life issue that you give comparing the two technologies of batteries!  I'm specifically thinking in regards to the Lifeline 2V-RV Battery Line...or the Sun Xtender AGM 2V which are both made by Concorde Corp in Ca..
Both designs show a picture of the battery and also they describe the battery as having totally enclosed Terminals. Also from any Limited data that I have seen on the web regarding cycles, it seems for that
AGM's are given 1000's of cycles when properly charged and maintained and not driven below 50%DOD
US battery, the maker of my present flooded units give a conservative estimate of 500 cycles when using the 50% DOD figure!
Also I'm under the understanding that AGM's are much more shock and vibration resistant, which for my RV use may be a good feature! I'm also wondering that if AGM's recharge quicker than conventional
units due to less internal resistance, that could benefit me with limited sunlight hours!
1.65 KW-RV 12V system of Sunpower Panels Classic 150 with BTS and WBJR and a Kid-6 x 6V US Batteries, 696 AH FLA-Magnum Energy MS-2812 Inverter, All Interior and Exterior Lights in the RV were replaced with LED's

Ottawa Canada (Summer) - SW Arizona (Winter)

Solar trucker

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Zoneblue thanks for the feedback...Yes weight and volume does require great consideration when living
out of a vehicle...Also I tend to think that you just might be right about using my present flooded till they
crap out...
1.65 KW-RV 12V system of Sunpower Panels Classic 150 with BTS and WBJR and a Kid-6 x 6V US Batteries, 696 AH FLA-Magnum Energy MS-2812 Inverter, All Interior and Exterior Lights in the RV were replaced with LED's

Ottawa Canada (Summer) - SW Arizona (Winter)

RossW

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For an RV application, seriously consider LFP.
They are smaller, they are MUCH lighter, they require virtually zero maintenance.
Four cells in series wil give you your nominal 12V. You will probably need some sort of management for them, but they're getting more common and less expensive.
No lead, no acid, no hydrogen or venting requirements.
I replaced my AGMs with LFP and my only regret is not doing it sooner.
If I was in a mobile situation, it would be streets ahead (in my view) than any variation of lead-acid.

(Please note, LFP is not just any old "lithium ion" cell, LiFePO4 is lithium IRON phosphate, or Lithium Ferro-phosphate, and is much better behaved than most of the lithium-ion technology cells)
3600W on 6 tracking arrays.
7200W on 2 fixed array.
Midnite Classic 150
Outback Flexmax FM80
16 x LiFePO4 600AH cells
16 x LiFePO4 300AH cells
Selectronics SP-PRO 481 5kW inverter
Fronius 6kW AC coupled inverter
Home-brew 4-cyl propane powered 14kVa genset
2kW wind turbine

mike90045

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Mike I welcome all advice and I do agree with you that AGM's are at least twice the price of flooded units..I'm a little confused about the exposed Lead Terminals and the cycle life issue that you give comparing the two technologies of batteries!  I'm specifically thinking in regards to the Lifeline 2V-RV Battery Line...or the Sun Xtender AGM 2V which are both made by Concorde Corp in Ca..
Both designs show a picture of the battery and also they describe the battery as having totally enclosed Terminals. Also from any Limited data that I have seen on the web regarding cycles, it seems for that
AGM's are given 1000's of cycles when properly charged and maintained and not driven below 50%DOD
US battery, the maker of my present flooded units give a conservative estimate of 500 cycles when using the 50% DOD figure!
Also I'm under the understanding that AGM's are much more shock and vibration resistant, which for my RV use may be a good feature! I'm also wondering that if AGM's recharge quicker than conventional
units due to less internal resistance, that could benefit me with limited sunlight hours! 


Mfg's cycle life charts are fine and all, but real life, it's not as long.  Can't do a "true" EQ cycle, if anything goes wrong, you can't replace vented electrolyte.   As for exposed terminals, all PbH2So4 batteries I've seen have lead terminals you bolt your cable lugs to. What you describe is new to me.
I'll agree as to being able to take shock and vibe better than flooded.  And with their low internal res, they can be recharged faster.
http://tinyurl.com/LMR-Solar

Classic 200| 2Kw PV, 160Voc | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph )| Listeroid 6/1, st5 gen head | XW6048 inverter/chgr | midnight ePanel & 4 SPDs | 48V, 800A NiFe battery bank | MS-TS-MPPT60 w/3Kw PV

Solar trucker

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Ross thanks for pointing out another option.  I'm a little concerned and overwhelmed by the accessories
required for Managing the individual cells and Battery Bank...or am I reading too much into it and it's
relatively easy to take care of that technology?
I like the fact LiFePo4 is considerably lighter with much improved cycles and recycle stats...
1.65 KW-RV 12V system of Sunpower Panels Classic 150 with BTS and WBJR and a Kid-6 x 6V US Batteries, 696 AH FLA-Magnum Energy MS-2812 Inverter, All Interior and Exterior Lights in the RV were replaced with LED's

Ottawa Canada (Summer) - SW Arizona (Winter)

Westbranch

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Look for some posts by  PNJunction on NAWS forum, there are some rather long and detailed threads that have a lot of the info you are probably looking  for.  He is a proponent of bottom balancing...

sample :  http://forum.solar-electric.com/discussion/comment/298620#Comment_298620
KID FW1811 560W >C&D 24V 900Ah AGM
CL150 29032 V.2126-NW2097-GP2133 175A E-Panel WBjr, 3Px4s 140W > 24V 900Ah AGM,
2 Cisco WRT54GL i/c DD-WRT Rtr, NetGr DS104Hub Hughes 1100 Sat. Modem
Cotek ST1500 Inv  want a 24V  ROSIE Inverter
OmniCharge3024  Eu1/2/3000iGens
West Chilcotin 1680+W to come

Solar trucker

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Thanks West Branch, I actually deal with NAWS in Flagstaff for some of their stuff..They are pretty
good people...very knowledgeable and not pushy. It never occurred to me to check out their forum
to see if there was something in there on batteries!  I've read some of the posts and will do a lot
more reading before jumping on a new set of batteries!

I'm also adding another 315 watts on the RV roof for a Total of 1653 watts and one Classic Lite
to interface with my present Classic 150...Actually I got away with using a standard 25ft phone cable
to remotely mount my Classic MNGP in the RV Kitchen area....works like a charm!
1.65 KW-RV 12V system of Sunpower Panels Classic 150 with BTS and WBJR and a Kid-6 x 6V US Batteries, 696 AH FLA-Magnum Energy MS-2812 Inverter, All Interior and Exterior Lights in the RV were replaced with LED's

Ottawa Canada (Summer) - SW Arizona (Winter)