Need to match new batteries with old panels

DmitriDmitri Posts: 5Registered Users
What we have: 12 each Suniva Optima 60 cell 260W panels (38.6 Voc) wired in 4 strings of 3 each. We just fried a bank of batteries (human error!). I would like to replace batteries with 8 each Rolls S6-460 AGM batteries (6V, 415Ah) in series for our 48v system. We use the system only on weekends, and sun averages 5 hours in winter, 7 in summer. Load is about 8amps/hour for 7 hours each weekend day, then almost nothing during the week. 
Would the system be well matched? For a 48V system should the panels be changed to 6 strings of 2 each? Thanks for your help! We cannot add to or change the panels, but we can purchase different batteries if recommended.

Comments

  • westbranchwestbranch Posts: 5,112Solar Expert ✭✭✭✭
    edited March 2016 #2
    lets step back a bit and tell us how you believe the fried batt bank happened.. it may give us clues to prevent it reoccurring...and also why you want to go to AGM, which have their own issues...
     
    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,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • DmitriDmitri Posts: 5Registered Users
    Good question. Someone set the charger on equalize and left it that way for a couple days. Batteries (Trojan L16 flooded)  fried. We're not great at maintenance, so I'm hoping AGM will be a little more forgiving.
  • VicVic Posts: 2,933Solar Expert ✭✭✭✭
    edited March 2016 #4

    Hi Dmitri,

    Welcome to the Forum.

    Those Flooded Trojan batteries should be able to accept many hours of EQ,  if they do not run low on water,  and the battery temperature is kept below about 46 degrees C.  AND,  one must use a Battery Temperature Sensor with all charge sources,  this is especially important when EQing a battery.

    You should appreciate,  that much of battery maintenance,  is really paying attention to them,  and giving them what they need,  approximately when they need it.  AGM batteries are sensitive to charge voltage,  Absorb and Float times,  as well as proper temperature compensation values and Limits.

    If you have an MPPT Charge Controller (CC),  and we assume that you do,  you will be better off keeping the four strings of three PVs.

    As you know,  sizing the battery bank,  and PV power really depends upon the loads,  and the time of day that these loads occur. 

    FWIW,   Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • DmitriDmitri Posts: 5Registered Users
    Thank you Vic and Westbranch for your input. The building is remote and not occupied for 1 or 2 weeks at a time, so monitoring is difficult. It's a garage/classroom inside a wilderness park. That was the impetus to go for AGMs.
  • vtmapsvtmaps Posts: 3,738Solar Expert ✭✭✭✭
    What brand and model is your charge controller?  As Vic pointed out you need a temp sensor for your controller. 

    Whatever it is that happened to your flooded batteries, it will be MUCH easier for it to happen with AGM batteries. 

    There is no reason you can't have flooded batteries... they will do just fine for a few weeks at a time without attention.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • DmitriDmitri Posts: 5Registered Users
    Charge controller is Outback FM80-150V MPPT. Is there a temp sensor available for it?
  • BB.BB. Posts: 28,139Super Moderators, Administrators admin
    Here is one (I think it is the right one--no other options):
    RTS - Outback Power Remote Temperature Sensor

    RTS - Outback Power Remote Temperature Sensor

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • VicVic Posts: 2,933Solar Expert ✭✭✭✭
    BB. said:
    Here is one (I think it is the right one--no other options):
    RTS - Outback Power Remote Temperature Sensor

    RTS - Outback Power Remote Temperature Sensor

    -Bill


    YES,  Bill that is the correct RTS for the OB FM CCs,   and well worth the price!

    Dmitri,  it is quite possible that a major issue with your Trojan Flooded batteries was that there appears to have been no RTS on the FM-80.

    During an extended EQ, the battery temperature can rise significantly.   This temperature rise requires that the EQ voltage be reduced ...  a further temperature rise requires yet further reduction in the EQ voltage,  and so on.   Without the RTS,  this required automatic voltage reduction does not occur.   Without this compensation,  battery current and temperature rise can increase above values that the batteries can tolerate,  and can approach Thermal Runaway.   This may well be the main factor in the issues with the Flooded batteries you have seen.

    Sealed batteries,  like AGMs are more sensitive to proper charge voltages and Absorb time,  and they need a reasonable amount of time in Float,  to attain proper full charge.

    AND,  with AGM batteries it is often  difficult to determine if they are being fully charged,  as one cannot measure the SG of the cells.  So,  in time,  these batteries can deteriorate from chronic undercharging.  On the flip side,  overcharging AGMs is also not good for them,  if this is done over an extended time period.

    Also,  AGMs are more expensive,  and have about half the number of discharge  cycles,  compared to Flooded batteries.

    What is the nature of "fried" condition of the present battery bank ...  did the plates become exposed to air from low electrolyte levels,  or ... ??

    Please carefully consider your choice for replacement batteries.

    Thanks for any additional details,    Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • petertearaipetertearai Posts: 362Solar Expert ✭✭✭
    Not sure if the fm 80 adjusts the voltage via the temp compensation during eqilisation . It is my understanding it will shut down eq  if battery temp reaches 50 deg  C . 
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . victron battery monitor . 24 volts 450 ah surette batterys . off grid  holiday home 
  • petertearaipetertearai Posts: 362Solar Expert ✭✭✭
    discussion about fm 80 eq temp compensation    http://www.outbackpower.com/forum/viewtopic.php?f=29&t=5087
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . victron battery monitor . 24 volts 450 ah surette batterys . off grid  holiday home 
  • DmitriDmitri Posts: 5Registered Users
    Thanks to all for the great information. Anyone know an expert in my area? Joshua Tree, California. 
  • VicVic Posts: 2,933Solar Expert ✭✭✭✭
    Not sure if the fm 80 adjusts the voltage via the temp compensation during eqilisation . It is my understanding it will shut down eq  if battery temp reaches 50 deg  C . 


    Hi peter,

    Yea,  I DO know that the MX-60 definitely did NOT compensate Veq,  but have never run any FM CCs,  had hoped that OB would have added that important function.

    The MidNite CCs DO allow the user to select weather or not the Veq is compensated -- have been using Classics for five years,  or so.   Compensation of Veq is important on longer EQs,  and for Automatic EQs,  otherwise,  for one or two hour EQs  the user can manually compensate at the beginning,  and perhaps again at the mid-point.

    Thanks for that info,  peter,     Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • westbranchwestbranch Posts: 5,112Solar Expert ✭✭✭✭
    edited March 2016 #14
    Dmitri said:
    Thanks to all for the great information. Anyone know an expert in my area? Joshua Tree, California. 
    well you are not far from the  Host of this site , Northern Arizona Wind and Sun... they might know someone...

    Our Fall and Winter office hours are from 8 AM to 4 PM, MST, Mon-Fri. We are closed for major holidays. If you are in the Flagstaff area, please stop by our store and visit - map link: Get Map to Store


     
    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,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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