Newbie question on batteries

Im as green as green can be when it come to solar systems, so please bare with me:

I have a little cabin up north off grid, and i bought a couple of 15 watt solar panels to charge bateries which i have only bought a deep cycle battery from Costco. I need the solar system to power a low wattage light for a few hrs at night and a tv and satelite systems.

I will only use the cabin on the weekends so it would have all week to charge the batteries.


so heres the question, i seen Walmart has 6v 200 cranking amp batteries on speacial for 9 bucks each. There not deep cycle, but the price is too good not to at least ask the question.

wondering if I bauy enough of them if they would do the trick

Thanks in advanced

john

Comments

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Newbie question on batteries

    30W nameplate (2, 15W panels) will realistically, only put out about 20, maybe 25 watts, for 4 hours a day. Another 2 hours at 10W, if you are lucky. So that's maybe 110W hours per day.

    Running a pure sine inverter (the Morningstar 300W SureSine comes to mind) for 2, 25W CFL lights, a TV @ 100W and a sat box @ 50W, you won't keep up, and it may take 2 weeks to get charged back up. (charging is not a 100 % efficient process).

    http://www.morningstarcorp.com/products/SureSine/index.shtml

    So you need more solar panels, less lights.

    For the 6V 200A batteries, $9 is a bargain.
    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 ,

  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Re: Newbie question on batteries

    Good Evening John--a little ccccooollllddd up there?

    OK, to answer your first question... a 15 watt panel is just about the right size to float two "car sized" deep discharge batteries for 9 months out of the year...

    I am guessing that "up north" is north of Belleville, ON--so you have some short winter days up there--so you might be a little short of power then.

    Regarding the battery--do not even bother to use a battery designed for starting cars/trucks. In general, the plates are thin and don't take well to discharging any more than 15% of capacity (state of charge 85% left).

    Of course, these sound cheap--perhaps if you baby them, you will still get your money out of them?????????

    The longer answer is you need to choose devices that are low power (conservation) and you need to know how much power these devices will use (amp*hours or Watt*hours or kWatt*hours).

    A Kill-A-Watt meter is a good place to start. You could plug your lights and electronics into one at home--run them for a typical cycle over a few days or weeks--and use the watt*hours of your AC appliances to define how much power you will need.

    I am guessing that you will be very surprised at how much power a TV + Satellite receiver will use.

    Just a guess..
    Lights=4 hours * 13 watt CPFL * 2 lights = 104 Watt*Hours
    TV=4 hours * 170 watts = 680 WH
    SatRcv=4 hours * 40 watts= 160 WH
    ==================Total WH====== 944 WHours / day

    Assuming that you want ~3 days of power (a good mix of cost+performance for a battery bank design--also takes care of that occasional three day weekend) and you will only use 50% maximum depth of discharge over those three days. And you will be using an 85% efficient AC inverter, plus an 80% efficient wet cell deep cycle battery--the size of your battery bank would be:

    Bank W*H=W*H-load*3 days*(1/50% discharge)*(1/85%)*(1/80%)
    Bank W*H=W*H * 8.82 (3days+50% batt+efficiencies)
    Bank W*H=944*8.82=8,326 WHours or 8.3 kWhrs of storage batteries...

    Say you do this with 12 volt battery bank:

    A*H = 8,326/12 = 693 Amp*Hours worth of batteries (roughly 7 car sized batteries).

    To calculate how much solar panel you will need (your 15 watt panel would be about enough to trickle charge two car batteries--storage, no loads)... Take a look at how much sun you get for your location. Once place to look is here. Looking at Toronto, I see you get about 2-5 hours of sun per day (winter-summer)...

    So, depending on which season--lets assume the "nice" months were you get 4 hours per day with a 77% derating factor (fudge factor is the technical term--close enough for us here).

    And, lets assume that you want to charge the batteries up over three days (after three days of use with cloudy weather).

    Solar panels = 944 W*Hour / (0.77%*0.85 inv eff * 0.80 batt eff *4 hours of sun)
    Solar panels = 944 W*Hour / (0.52 * 4 hours of sun)
    Solar panels = 454 watts of solar panels for March thru September use...

    The above is purely a guess and your numbers will be different--but it does give you some guidance on what you need to know and how to calculate your needs.

    Load drives panel and battery sizes. The numbers I used are conservative but reasonable. You could cut the number of batteries by 1/2 and even the panel by almost 1/2 and still have a reasonably working system for sunny weather.

    Or, if your TV+Sat+Lights are much less power hungry than I guessed (everyone wants a 32" flat panel in their summer cabin--right?)--your system can be downsized a lot too.

    Lastly, look at a small Honda eu1000i or eu2000i generator (Yamaha and others also make similar units) for winter/bad weather recharging of your battery bank. Will also be a nice addition (quiet and pretty fuel efficient).

    There are other things to discuss too (type of solar charge controller, pure sine wave inverters, battery types, temperature sensor, panels, panel mounting, etc.). But I will stop for the moment--my fingers are getting tired.

    Hope this helps...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Newbie question on batteries

    Hi jjjooohhhnnn, hows it goin down south , eh?

    I thnk Bill has it just about right on the money, use a Honda 1000i for the TV and Sat. hookup... these will be the big power users, and you will probably only have it on for a couple of hours per night, less than 1 liter of gas, probably about .5 L... then you will also have something to power the battery charger you might need on dark days .

    For the lights try to use '12v' lights, I use MR 16 LEDs in a track light configuration... very low consumption and nice and bright, can be a bit pricey, (you have to shop around, try Ebay...) you will need heavier wiring though if the cabin is more than 500 ft square and you want to hide the wire a bit...

    If you go this route you can ease into the solar crowd but keep an eye on your final objective when buying a Charge Controller and panels, get good ones from a reliable supplier so when you want to expand the # of PV 's you can get similar panel specs..

    enjoy the latest snow... ;)
    Cheers
    Eric
     
    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
  • System2
    System2 Posts: 6,290 admin
    Re: Newbie question on batteries

    Wow, you guys are great, didn't expect such a response, Thanks

    Anyways i should have given you guys the full story.

    I do have a 3600 watt generator, (which I love). My cabin isn't really a cabin more of a glorified shed. I just purchased the property early last year and built the shed late last year. Its 100 square feet. The shed is there just so I have a place to sleep over the next couple of years while I build the cottage which will also have a solar system.

    The property is only assecible during the summer months, May 24th to Nov at the latest. So I'm not worried about the winter months. Oh and the property is just east of Parry Sound (not sure if that makes a differents.

    I already have a 12" 12Volt colour Tv (don't know from where, but anyways)
    350 watt inverter for the satelite and 12 v lights.

    Really I should only need one light bulb to light the whole shed/cabin and the TV is only for the nights I don't get overly drunk and just pass out. so at the best 4hrs on a long weekend, unless my wife comes up, which means 12 hrs a day.

    I always bring up my generator, so if I need to charge the batteries, not a big deal. Also I will most likly pick up at least an additional 3 15 watt solar panels.

    So all in all, will the 9 buck batteries from Walmart if I buy 6 of them in conjunction with my deep cycle battery do the trick. Is it worth it or will the 6V 200 cranking amp batteries not work at all or just can't deliver the power for what I need.

    If the answer is staring me in the face in your posted comments, I apologize.


    And to answer your questions, get me the heck out of here, its too cold.
  • System2
    System2 Posts: 6,290 admin
    Re: Newbie question on batteries

    Forgot to mention, i have a 6 amp charge controller, cheapy i got off ebay.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Newbie question on batteries

    So all in all, will the 9 buck batteries from Walmart if I buy 6 of them in conjunction with my deep cycle battery do the trick.

    Is it worth it or will the 6V 200 cranking amp batteries not work at all


    Don't even try to mix battery types/brand/model Deep cycle batteries run about a volt higher voltage than starter batteries. (subtle chemistry changes) Only mix batteries from the same lot, from the same Mfg.

    Can you find a capacity for the 200 cranking amp batteries ? the CCA is just an instant rating, do they have a 96AH or 35AH rating marked anywhere - are they full size car batteries, or lawn mower battery size ? ( group 24, group 27 ? )
    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 ,

  • System2
    System2 Posts: 6,290 admin
    Re: Newbie question on batteries

    Unbelivable, I am trying to find any info on this battery at the energizer website, which there is none. Not sure if they make the battery just for walmart or not.

    Called Walmart, and 20 minutes later, i'd be surprised if the people I was talking too, will even be able to find there way home.

    Anyways, i can't find any additional info on the batteries. They are the 6V riding lawn mower batteries and thats all i can find out.

    Sorry for tha lack of info.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Newbie question on batteries
    They are the 6V riding lawn mower batteries and thats all i can find out.


    Forget them, they will be too small to be useful. maybe as a $20 backup pair, but I would not bother if you already have a deep cycle battery.
    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 ,

  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Re: Newbie question on batteries

    Well, your power use is probably a lot less than my "guess"... But you still need to figure out how much power you need to really size the number of panels+batteries you will need.

    Regarding the solar panels, if these are "amorphous" style panels (usually appear as one large uniform black panel, instead of those round or square shaped disks), you should instead look for poly or mono-crystalline solar panels as they will usually last longer and generator more power over their lifetime...

    And look for one 60 watt panel instead of 4x15watt panels. $$/watt for larger panels can be cheaper than getting a bunch of the little ones and wiring/mounting them (if the single larger panel size is OK for you).

    And forget those riding mower batteries... They may last you a year if you are lucky.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Newbie question on batteries

    John, doont underestimate the SWMBO factor lad, ;)

    as my Scot F-in-law used to say... ( she who must be obeyed)...

    It can be huge, as soon as you get a new gizmo installed there will be an automatic and increased demand for another, soon you will need a new genset or a lot of panels... and bigger batteries...

    All fun aside get a good battery, match the panels rated amperage to produce ~ 5% of the batterys amp capacity, eg 5 amp PV to 100 ampH battery, then get a Charge Controller to handle the PV output... batt sized to handle the projected loads as Bill said... get a Kill-a-watt, they are a great tool.

    Cheers
    Eric
     
    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
  • System2
    System2 Posts: 6,290 admin
    Re: Newbie question on batteries

    Thanks for the help, I will not buy the cheap batteries.

    One additional question. Walmart Canada (not availible in the US as far as I know) sell 15 watt panels for $74.99 when on special, 97.99 regular price.

    So on special 74.99 + Tax = 84.74 per 15 watt panel

    84.74 / 15 = $5.65 dollars per watt.

    I know thats pretty good, but do all the inefficientcies of connecting multiple panels outway the inexpensive cost of the panels.

    BB said to buy a 60 watt panel opposed to 4 * 15 watt panels, is there really that much of a difference?

    Thanks again, this site is great
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Newbie question on batteries

    if prices are equal (cost per watt) then there are other small factors that could offset it or sway you to the larger pvs. when going with many small pvs there are extra costs and efforts to wire and mount that many small pvs as opposed to 1 larger pv. i also doubt those small pvs have as good of a warranty like the bigger pvs have and who makes them is also a factor as i'd trust some of the more common longterm companies over those just getting into it with small pvs. know who makes those small pvs if you go with them.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Re: Newbie question on batteries

    Partly that depends on what kind of panel you get...

    From our host:

    Kaneka 60 Watt Solar Electric Panel for $265 (thin film, $4.42 per watt)

    Kyocera KC-65T 65 Watt Solar Panel for $325 (poly crystalline $5 per watt)

    So--for a thin film panel (which is probably what you are looking at) price (without shipping) is not bad.

    I normally try to steer away from thin film panels--but if our host has had good luck with this brand--may be OK to try (Wind-Sun has the experience with their customers--I do not).

    Of course, there is shipping and you are in Canada--so there are other issues that will impact your price.

    Check the warranty for both (as Niel suggests) and it is usually better to have fewer large panels to wire and mount (and keep sealed) than a bunch of smaller panels.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Newbie question on batteries



    http://www.icpsolar.com/4105/backup_maintenance.asp. they aer now tied in with Sunsei ?? whoever they are...

    I have a 15w one for my trolling motor, seems to work great

    Eric
     
    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