Battery, how much is too much

ShadowcatcherShadowcatcher Solar Expert Posts: 228 ✭✭✭
How much is too much, or not enough.
As covered earlier the AGM battery was boiled down to half its life. I now must replace it and have settled on a Lifeline AGM and I am looking at three different batteries and my inclination is "if some is good, more is better".
The choices are 105. 125 and 150 amp hour and 64 to 96 lbs and it is about $400 for the 150A
185 W panel into a Morningstar MPPT all LED lights Waeco, CF-40 refrigerator ~15 amp hours 24 hours. Eberspacher heater max draw on high 1.84A 7,500 btu. Stereo ~ 6A

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Battery, how much is too much

    Bit tied up just now, but short form is that 185 Watt panel won't be good for more than about 120 Amp hours.
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Battery, how much is too much

    The short answer is,,,, all battery sizing question stem from the load calcs. Define the loads, find the proper size battery bank for that load, and install the charging regimen to keep the battery properly charged. Looking at it another (but not ideal way) is since you have the PV, find a battery that is in the 5-13% range of AH capacity vs Charge current. Your 180 watts might like a battery of ~110 AH. The biggest mistake people make is too much battery and too little Pv coupled with too much load.

    Tony

    PS If this is an RV, and you have other charging options on a REGULAR basis,, like genny or driving, the battery could be somewhat bigger.

    T
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Battery, how much is too much

    Tony , IMSMC it is a teardrop trailer.
     
    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
  • techntrektechntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Battery, how much is too much

    I know most here recommend the load-battery-PV relationship that icarus describes. Personally I feel that a bigger battery is better - if and only if you can ensure that your loads don't increase to match the bigger battery (unless you also increase your charging sources and then you are back at step one). The first reason is the bigger your battery, the lower the depth-of-discharge and thus a longer battery life. Also, all system planning is still just a very educated guess even taking into account all the anticipated inputs and system losses. The best-planned system might still be "just a little too small", so having a little extra battery to start is one step towards correcting the design. Finally, the battery capacity will decrease over time and having too much capacity at the start will mean having just enough capacity at the end of the battery's life.

    I'm not talking about doubling or tripling the size, although I've heard of some systems where the planned DOD is 10% or less so some do go much, much bigger. Maybe go 5-10% bigger for a large system, and for a small system go 20% bigger. Especially with a small system that is only relying on one battery - by all means go larger. Why buy a 100 amp battery when you can get a 120 amp battery that is the same size and only a few dollars more? As long as you are almost always only taking out let's say 50 amps and always putting 50 amps back, with the 120 amp battery you have an additional 10+ amp reserve for those few days a year when your system design specs didn't quite measure up to reality. Granted, then those few days a year you are back to my first warning and you must be careful to then conserve or hook up a genset to replace that emergency reserve, but at least its an option you otherwise wouldn't have had with a 100 amp battery (without potentially discharging the battery too far). 50 amps from a 100 amp battery is a 50% DOD. 50 amps from a 120 amp battery is a 42% DOD, which will last longer. And that 100 amp battery wouldn't have enough capacity after just a year of service so continuing to take 50 amps from it every day will cause it to die quickly.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • mike95490mike95490 Solar Expert Posts: 9,582 ✭✭✭✭✭
    Re: Battery, how much is too much

    And the problem with a BIG battery, is when you have the 4 cloudy day event, and it's sitting below 70% full, and begins to sulfate, and loose capacity. You have to have a charging source that can bring it up quickly enough to not sulfate. Depending on a small solar array, may take 3 or 4 more days to fully recharge the bank.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • techntrektechntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Battery, how much is too much

    If you are referring to my post, I covered that. My big warning - repeated twice - was to not rely on the overcapacity as a reserve. And then I said if you do use it as an emergency reserve you gotta conserve or crank up a genset to compensate.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Battery, how much is too much

    As I have noted before. Battery size is an educated calc regarding battery performance VS battery life VS life cycle cost. When I built my current system, the debate was between 4 T-105s at $X vs 4 L-15s at $X.5. My conclusion was, that the smaller bank, properly loaded would most probably be cheaper in life cycle cost assuming 5 years on the T-105s and 8 years on the L-16s. If the smaller battery lasts longer than the 5 year expectation, (and then assuming the L-16s would also last longer) then the equation still sort of stands.

    Bottom line, battery life span is directly related (amongst other issues) to depth of discharge and number of cycles. Lower DoD will make a battery last more cycles. That said, if you don't have proper charge regimen, then all numbers are affected. And finally, keep in mind the cardinal rule: Loads will grow with time, how much is a matter of conjecture. Mine have quadrupled in 10 years,, because they could!

    Tony
  • ShadowcatcherShadowcatcher Solar Expert Posts: 228 ✭✭✭
    Re: Battery, how much is too much

    One of the mistakes I made when I was anticipating delivery of the trailer, it was a year and a half over due, is that I started accumulating things like the solar panel controller etc. However I did not do my home work and the panel was meant for grid tie and too high voltage for the PMW controller. The controller was installed before I found out the mistake, so it is still in there along with the Morningstar MPPT. There are a bunch of Uni-Solar PVL-144 flexible panels on ebay at a great price and one that could go through the PMW controller. Having a panel I can stake out in the sun is attractive.
    I do appreciate the thoughts and I will order the largest battery tomorrow. The DOD and diminishing capacity was kind of in my thinking but this kind of helped that gel.
  • SevenSeven Solar Expert Posts: 292 ✭✭
    Re: Battery, how much is too much

    The big problem with a big battery is making sure it can be recharged fairly quickly back to full charge. If e battery is in a trailer you may want to run a feed line from the vehicle to the batteries so that the alternator can help. That would give you a boost of charge as you drove to your destination and one when you headed back home to park it.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Battery, how much is too much

    i have to ask if these current readings are for 120vac or 12vdc. there is a big difference here. the big clue that you are mixing them up is that you list a 7500btu heater as 1.84a. heating with electric isn't a good idea in the first place, but there's no way a 7500btu heater is only going to draw 1.84a dc from 12v batteries. that heater is around 2400w and at 12v this would be well over 200a if using an inverter to power it. the ac amps would need to be multiplied by 10 in theory for a 12vdc to 120vac conversion from the 12vdc source. adding the efficiencies to that could cause another 20% or so to be drawn from the battery current.
  • BB.BB. Super Moderators, Administrators Posts: 32,639 admin
    Re: Battery, how much is too much

    Sounds more like a Propane heater with a small DC fan.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • telljftelljf Registered Users Posts: 20 ✭✭
    Re: Battery, how much is too much

    My experience shows that a bigger battery is better. Apart from the DOD factor mentioned above, a bigger battery can soak up more charge available from the sun. When I had a 200AH battery, it used to reach "full" charge at around 12 noon. Then the charging current drops off, even though the sun has just reached its prime position. After I doubled the battery capacity, it reaches full charge by around 2pm and hence is able to receive much more AH than was possible to extract out of the panels previously.
  • ShadowcatcherShadowcatcher Solar Expert Posts: 228 ✭✭✭
    Re: Battery, how much is too much

    There is a 10 ga wire with circuit breaker that runs from the TV battery to the trailer battery, that is good for 30 A from what I understand. If we are parked I have a set of one ought jumper cables to get an even better connection.
    I ordered the 150 AH battery today and have been looking for a battery box to fit. The Lifeline GPL 30HT is 13.46l X 6.77W X 11,95 T and there are a couple I can find that will almost fit (the height seems to be the problem).
  • mike95490mike95490 Solar Expert Posts: 9,582 ✭✭✭✭✭
    Re: Battery, how much is too much

    You will want to run a ground wire from trailer to tow vehicle. Counting on the ball hitch to carry serious return/ground power, is wrong.

    Better yet, spend the $, and get a connector, and make your own harness, it will be better then the factory wire.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Battery, how much is too much

    for the best (connectors and) wire go to a big rig service depot and ask for 'Phillips Arctic superflex' wire.http://www.phillipsind.com/product/417.html

    It's made for those HD trailers and is great stuff in the winter, not cheap but you get what you pay for.8)
     
    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
  • simagicsimagic Solar Expert Posts: 100 ✭✭✭✭
    Re: Battery, how much is too much
    westbranch wrote: »
    for the best (connectors and) wire go to a big rig service depot and ask for 'Phillips Arctic superflex' wire.http://www.phillipsind.com/product/417.html

    It's made for those HD trailers and is great stuff in the winter, not cheap but you get what you pay for.8)

    MODERATOR.............Am I allowed to recommend a site and person where I purchased my batteries ..or is that a conflict of interest on this site
  • BB.BB. Super Moderators, Administrators Posts: 32,639 admin
    Re: Battery, how much is too much

    Answering questions asked And on topic discussions are fine.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • simagicsimagic Solar Expert Posts: 100 ✭✭✭✭
    Re: Battery, how much is too much
    How much is too much, or not enough.
    As covered earlier the AGM battery was boiled down to half its life. I now must replace it and have settled on a Lifeline AGM and I am looking at three different batteries and my inclination is "if some is good, more is better".
    The choices are 105. 125 and 150 amp hour and 64 to 96 lbs and it is about $400 for the 150A
    185 W panel into a Morningstar MPPT all LED lights Waeco, CF-40 refrigerator ~15 amp hours 24 hours. Eberspacher heater max draw on high 1.84A 7,500 btu. Stereo ~ 6A


    Got my batteries from. http://centexbatteries.com/PVX-2240T.html Marc was very helpful and prices were good
  • ShadowcatcherShadowcatcher Solar Expert Posts: 228 ✭✭✭
    Re: Battery, how much is too much

    The heater is a Eberspacher diesel heater the only resistance heating is the glow pin when first starting, they are very efficient. All amperage's quoted are 12V and actual readings, (I don't trust published figures).
    The battery was bought from Tri State battery for $400 Centex wants $463.
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