Batteries recommendation

MT1912MT1912 Posts: 17Registered Users ✭✭
Hello, I'm looking into batteries and I really like the Sun Extender from Concord, AGM batteries. They are on the expensive side but quality batteries. Anyone can recommend anything else with a good price/quality ratio? I prefer AGM over other tech., but I'm open to other suggestions. System will be either 12 or 24V.
Thanks.

Comments

  • littleharbor2littleharbor2 Posts: 914Solar Expert ✭✭✭✭
    Fullriver deep cycle AGM's are some of the best.

    http://fullriverbattery.com/product/batteries/DC250-6

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • MT1912MT1912 Posts: 17Registered Users ✭✭
    Nice, haven't heard of these yet, thank you, I'll add them to the list to get more info.
  • BB.BB. Posts: 27,433Super Moderators admin
    As always, the question is how are you going to use the batteries and what are your expectations?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MT1912MT1912 Posts: 17Registered Users ✭✭
    edited June 12 #5
    What do you mean "how am I going to use them" ? What I am going to power by them? How much I am going to discharge them? Or are you asking where they will be stored ? Please clarify.
  • BB.BB. Posts: 27,433Super Moderators admin
    Sort of all that... AGMs have their strengths. Don't gas, very clean running, are more efficient, have higher surge current capacity, can be mounted on their sides, can take some freezing without cracking the case, can be shipped air/as non-hazardous materials. In many ways, they are almost the "perfect" Lead Acid battery.

    But they have their weaknesses too... They do gas when they get old/end of life/over charging, are sensitive to overcharging, have (very roughly) a couple year shorter service life than similar quality flooded cell lead acid batteries, are something like 2x as expensive as FLA. It can be difficult to "know" the state of charge of an AGM/Sealed battery (cannot check specific gravity). more sensitive to over charging (overheat catalyst, cause cells to vent, no way to "replace" lost electrolyte). Because you cannot check electrolyte, cannot replace electrolyte, sensitivity to over charging--AGM tend to be easier to "murder" by their owners.

    Batteries are designed for different types of operation... Standby/float service (mostly charging, shallow 15% "daily" discharge, with a few deep cycles--such as computer/telecom backup power). Or they can be designed for daily cycling use (typically using ~25% of capacity on a daily, or regular cycle).

    Some are designed for short lives (typical UPS batteries may be replaced every few years). Traction/forklift flooded cell batteries can have 15+ year daily cycling life (and are less efficient, need somewhat larger solar array, and use a fair amount of distilled water).

    If this is your first time going off grid/battery power--Many times "golf cart" (6 volt @ ~200 AH) flooded cell batteries are nicer to use. More forgiving and you can add electrolyte if you over charge them by accident/system settings issues. And they are cheap/easy to replace.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MT1912MT1912 Posts: 17Registered Users ✭✭
    BB. said:
    Sort of all that... AGMs have their strengths. Don't gas, very clean running, are more efficient, have higher surge current capacity, can be mounted on their sides, can take some freezing without cracking the case, can be shipped air/as non-hazardous materials. In many ways, they are almost the "perfect" Lead Acid battery.

    But they have their weaknesses too... They do gas when they get old/end of life/over charging, are sensitive to overcharging, have (very roughly) a couple year shorter service life than similar quality flooded cell lead acid batteries, are something like 2x as expensive as FLA. It can be difficult to "know" the state of charge of an AGM/Sealed battery (cannot check specific gravity). more sensitive to over charging (overheat catalyst, cause cells to vent, no way to "replace" lost electrolyte). Because you cannot check electrolyte, cannot replace electrolyte, sensitivity to over charging--AGM tend to be easier to "murder" by their owners.

    Batteries are designed for different types of operation... Standby/float service (mostly charging, shallow 15% "daily" discharge, with a few deep cycles--such as computer/telecom backup power). Or they can be designed for daily cycling use (typically using ~25% of capacity on a daily, or regular cycle).

    Some are designed for short lives (typical UPS batteries may be replaced every few years). Traction/forklift flooded cell batteries can have 15+ year daily cycling life (and are less efficient, need somewhat larger solar array, and use a fair amount of distilled water).

    If this is your first time going off grid/battery power--Many times "golf cart" (6 volt @ ~200 AH) flooded cell batteries are nicer to use. More forgiving and you can add electrolyte if you over charge them by accident/system settings issues. And they are cheap/easy to replace.

    -Bill
    Thanks, this is not my first time, I built my off grid solar generator years ago and while my Sun Extender batteries still have some life in them I'm looking into getting new ones and adding more capacity, so thinking about at least 500-600 Ah total, I'll be discharging them to about 50% daily (maybe less if I increase total Ah). I've been doing it with my current setup and they hold up pretty well. Going strong 6+ years. I'm not in a hurry, just exploring what's out there.

    My batteries power my home office, 2-3 monitors, 2 PC's, charging some other gadgets etc... I think I should stay with sealed type since they are indoor not very far from where I sit.
    Do you think flooded are pretty safe to have indoor ?
  • BB.BB. Posts: 27,433Super Moderators admin
    edited June 12 #8
    Flooded Lead Acid batteries need to be vented... Not so much for hydrogen gassing (which is an issue, but hydrogen floats up and will generally go through any permeable surface/cracks/gaps in roof/ceiling/etc.). Not like propane or gasoline fumes which tend to sink and collect in low spots--Just waiting for an ignition source.

    The bigger issue (in my personal opinion) is that the FLA batteries vent electrolyte mist which will corrode anything nearby (venting during charging/EQing to get mist away from battery connections/nearby electronics/personal items). FLA batteries can crack (freezing, dropped, small H+O explosion in cell, etc.) and they need to be in a container or area where acid leaks will not be (overly) expensive. AGMs don't leak if cases fail.

    All batteries should be treated as if they are a source of explosion or fire. Most batteries will tend to do very nasty stuff if over charged (long time, boil electrolyte away, venting, possible fire, etc.). I would suggest not placing AGM's under the bed (for example--We actually get a fair number of people asking this question). Keeping batteries "secure" so that metal things don't drop on them, kids cannot get to them, etc.

    Appropriately rated (for size of wire) Fusing or Circuit Breaker(s) on wiring from batteries to loads (nothing like a red hot wire going into a short to ruin your day) is also critical for safety.

    Are batteries "safe" indoors... With proper planning and operation they are relatively safe (I park a car with a 20 gallon gas tank in the garage under my kid's room--How safe does that sound?).

    My major concern is that off grid solar power system run 24x7 all year round--And if something goes wrong while nobody is home--Things happen.

    It sounds like however you have been using your present battery bank--You have been doing well by them. 6+ years on daily cycling duty for AGM (or inexpensive FLA)--Be happy.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bill von novakbill von novak Posts: 731Solar Expert ✭✭✭✭
    BB. said:
    Flooded Lead Acid batteries need to be vented... Not so much for hydrogen gassing (which is an issue, but hydrogen floats up and will generally go through any permeable surface/cracks/gaps in roof/ceiling/etc. Not like propane or gasoline fumes which tend to sink and collect in low spots--Just waiting for an ignition source.

    The bigger issue (in my personal opinion) is that the FLA batteries vent electrolyte mist which will corrode anything nearby (venting during charging/EQing to get mist away from battery connections/nearby electronics/personal items).

    Second this.  I once did an off-grid system with a large T105 based battery bank.  I vented it with a fan that pulled air out through a vent to the outside.  Within a year the fan was corroded to almost nothing; even the plastic frame was degrading.

    I switched to two external vents with one fan pushing air in one vent and that worked.
  • BB.BB. Posts: 27,433Super Moderators admin
    Bill V.

    Good comment... I will have to remember to recommend that the fan(s) push fresh air into the box--Not draw out "misty" air.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Posts: 3,690Solar Expert ✭✭✭✭
    I will give you the opposite opinion based on 100's of apps. There can be some corrosion especially if the set-points are too high.

    If done correctly in a large room (garage size) it really is not an issue. If it were, I would see evidence in XW's that vertically ventilate from within 5 or les feet of LA batteries. It may be a problem on systems that are slow to charge (insufficient charge current) and take too much time to go thru the cycles. 

    If you only bring in fresh air to the box and the room is too small you may have other problems ;)
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

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