AGM Battery Charateristics?

54d1854d18 Posts: 67Solar Expert ✭✭
I have a line on some new batteries, Ritar RA12-100 for use in my small off grid
system.  The spec sheet is attached.

I have never used AGM's before, and am curious as to controller setup.
Basically, I am not sure what the cutoff for bulk or absorption charge is.
When setting up for FLA I had to enter the setpoint for charge current
to switch to Float mode, and a max time value.

Thanks,

T

Comments

  • EstragonEstragon Posts: 2,056Registered Users ✭✭✭✭
    These appear to be designed for standby (float) service in a UPS-type application, and may not handle deep-cycling for long. That said, they can sometimes be had for cheap.

    You may have to experiment a bit with end amps to terminate absorb - typically it's ~1-2% of 20hr capacity, and a timeout of 3-4hrs or so.

    Temperature compensation (preferably using a sensor attached to battery) is important, especially with AGMs. Too high voltage can make them vent gas, potentially ruining them.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • westbranchwestbranch Posts: 4,995Solar Expert ✭✭✭✭
    Based on the table in that doc you should start charging, when new, at ~ 14.6 V ( cycle service) and if not enough increase at 0.1V increments.. Float  at 13.6V -13.8V... and as previously stat above End Amps at 1% to 2% of capacity...
    You want a good Charge controller that will allow these values to be adjusted  EASILY as you learn about your new batteries.

    I am not familiar with this brand, and ,as far as I have experienced, the higher the price and length of pro-rated warranty period (7 years is average AGM warranty ) , the better the product...

     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Raj174Raj174 Posts: 581Solar Expert ✭✭✭✭
    I agree with @Estragon, these are designed for UPS/float service. I have a friend using similar batteries for about 4 months now. The spec sheet does state an equalization and cycle service charge rate of 14.6 to 14.8V, but I suggest something  more conservative by setting absorb at 14.2 to 14.4V because you want to charge, not equalize. 
    Hopefully your charge controller can be configured with these settings. Since these are really not made for deep cycling you may only get 150 to 200 cycles out of them.

    Rick
    12 x 300W Renogy PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH HI Power LiFePO4 no BMS, 4000W gen.
  • westbranchwestbranch Posts: 4,995Solar Expert ✭✭✭✭
    here is a very informative document from the maker of my AGMs or more properly named Valve Regulated Lead Acid batteries.... it has a good description about  FLAs , AGMs and how to charge AGMs...  I reread it on about a yearly basis to refresh my foggy brain.... http://www.cdtechno.com/pdf/ref/41_2128_0212.pdf 


    Note some  of the AGM makers do not use the term " FRESHENING Charge"  when they should as AGMs can NOT be EQUALIZED! due to their very nature, they are sealed and you can not add water if the valve vents O2 and Hydrogen. A  not enough to freshening charge gets the voltage up but not high enough to cause venting..

    Happy reading
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Raj174Raj174 Posts: 581Solar Expert ✭✭✭✭
    Yep, looks well worth the read. Thanks westbranch
    12 x 300W Renogy PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH HI Power LiFePO4 no BMS, 4000W gen.
  • westbranchwestbranch Posts: 4,995Solar Expert ✭✭✭✭
    Here is a whole page of VRLA  documents if you have a few hours

    http://www.cdtechno.com/resource/support_doc.html

     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • 54d1854d18 Posts: 67Solar Expert ✭✭
    Wow, as usual, a lot of very good info.
    It would appear that these may not be what I am after in the way of battery storage,
    I'll likely replace my old ones with FLA's like I had before.

    Thanks everyone...
  • westbranchwestbranch Posts: 4,995Solar Expert ✭✭✭✭
    If the price is really good compared to retail, don't be scared off, there is lots to learn...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • EstragonEstragon Posts: 2,056Registered Users ✭✭✭✭
    I agree with @westbranch - telcos etc sometimes swap them out based just on time in service, and they can sometimes be had for a bit over scrap value. In a standby application, they HAVE to work. The cost of replacing batteries in that application is less than routine load testing, and the implicit cost of risk of failure, so they get replaced.

    They aren't ideal for deep cycling, but for the right price might make sense (assuming it isn't a giant PITA to install/remove them when they have to be replaced). At the right price, just sell any duds for scrap value and use the good ones until they're scrap too.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • 54d1854d18 Posts: 67Solar Expert ✭✭
    These were supposedly new, not sure where the individual got them, likely from a UPS,
    and price was close to half of retail.

    My old FLA's were 225AH 6v, and lasted me 13 years, they were configured for 12v,
    and were likely not cared for the best for the first few years of their life as I didn't have
    an MPPT controller at the beginning.
  • mcgivormcgivor Posts: 1,544Registered Users ✭✭✭✭
    54d18 said:
    These were supposedly new, not sure where the individual got them, likely from a UPS,
    and price was close to half of retail.

    My old FLA's were 225AH 6v, and lasted me 13 years, they were configured for 12v,
    and were likely not cared for the best for the first few years of their life as I didn't have
    an MPPT controller at the beginning.


    FLA are generally  way more forgiving than AGM, it doesn't really matter wether they are charged with PWM or MPPT, get the settings wrong with either, problems will be the result. AGM are better suited to installations where maintenance cannot be performed regularly, but this doesn't mean they are maintenance free, complacency can result in unexpected issues. If checking the electrolyte level plus adding a little water now and again is too much of a chore then go for it, but these regular checks provide the opportunity to take meter readings across batteries, terminals and feed conductors all of which can avoid the proverbial Jack in the Box problems, if one depends on a system for daily life, it's a small price to pay to perform regular maintenance.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • Raj174Raj174 Posts: 581Solar Expert ✭✭✭✭
    @54d18

    I would not use a percentage of the manufacturers retail price as a point of value. I would estimate 20 to 25% of the cost to replace your current FLA bank. At this price they might be worth the considerably shorter life span, but your call.

    Rick  
    12 x 300W Renogy PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH HI Power LiFePO4 no BMS, 4000W gen.
  • EstragonEstragon Posts: 2,056Registered Users ✭✭✭✭
    Personally, I wouldn't pay much over local scrap value, but as Rick says, your call.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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