Which batteries to use?

Are special batteries required or advisable for solar systems? The batteries I see at various places on the internet seem expensive compared to an average 12 volt car battery. Can I just get an array of car 12 volts and a standard 120 volt inverter not designed particularly for solar?

Are there safety issues associated with keeping any type of batteries indoors? I have 3 computer servers that run 24/7 that I want to run off of solar during the day and batteries charged by solar at night. I'd be keeping the batteries in my office, but would put outside if there are any issues with inside.

Thanks!

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Which batteries to use?

    There are very good reasons for using <I>true</I> Deep Cycle batteries as opposed to standard 'automotive' batteries or even the 'hybrid' RV/Marine 'deep cycle' types.

    Check this Battery FAQ to begin with: http://www.windsun.com/Batteries/Battery_FAQ.htm

    Issues with keep batteries indoors are mainly associated with the 'vented' type of flooded lead-acid cell; they emit hydrogen sulphide in small quantities and also hydrogen and oxygen when charging. Two other types, AGM's and Gel cells, do not have that issue. But they are more expensive per Amp/hour.

    Also, unless your office is out in the middle of nowhere (like mine) you probably not find any reason to go "off-grid". Utility rates are lower than the over-all cost per kW/hr almost everywhere. This begs the question "Why do you want to do this?" If the answer is "To save money" you're looking at the wrong solution.
  • System2System2 Posts: 6,290 admin
    Re: Which batteries to use?

    Cariboocoot, thanks for the info. It's definitely not to save money. The main reason is for general interest and sort of eventually "show case" solar that's getting to be important in Northern California.

    The off grid aspect has to do with 2 things:

    1. Hooking up to the grid requires a permit and a specialized electrician + an expensive inverter, something that I don't want to invest in right now. I'll eventually hook up to the grid, but I want to experiment with the equipment at my location before investing in a large system.

    2. My internet servers need a way of handling power interruptions from PG&E, which are quite common at our location. At this point it's either getting a gas powered backup generator or a solar/battery solution.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Which batteries to use?
    horton wrote: »
    Cariboocoot, thanks for the info. It's definitely not to save money. The main reason is for general interest and sort of eventually "show case" solar that's getting to be important in Northern California.

    The off grid aspect has to do with 2 things:

    1. Hooking up to the grid requires a permit and a specialized electrician + an expensive inverter, something that I don't want to invest in right now. I'll eventually hook up to the grid, but I want to experiment with the equipment at my location before investing in a large system.

    2. My internet servers need a way of handling power interruptions from PG&E, which are quite common at our location. At this point it's either getting a gas powered backup generator or a solar/battery solution.

    Then you're looking at the "other kind of grid-tie"; where the gird is the back-up power for the solar.

    The first question you need to answer in designing a system is: How much power do you use?
    There's a handy little device called a Kill-A-Watt meter which can be plugged in between your servers and the outlet (one at a time). It will measure how much power each one uses, both while running and over time. You need numbers like that so that you can size the system.

    Basic design:

    Size the inverter to handle the maximum total load. Maximum Watts in use all at one time = minimum inverter size.
    Size the batteries to handle the load over time between charging. Watts used in 20 hours (4 hours of charge time) * system Voltage = 1/2 minimum Amp/hour rating for batteries.
    Size the solar array to charge the batteries. Target current of 5%-15% of the total battery Amp/hour rating.

    That's the three very basic rules. Once you have that information you can begin "fine tuning" and getting all the details worked out - before you start spending the money.

    As Tony (Icarus) always says: Avoid "Ready, Fire, Aim!"
  • System2System2 Posts: 6,290 admin
    Re: Which batteries to use?

    Thanks Cariboocoot. I got a Kill A Watt. I can't check the actual servers until this weekend when there's less traffic.

    I checked a similar computer and found the maximum power to be around 120 watts. That's with the hard drive working hard. I think probably 2 of the servers will be at 150 watts because they have dual RAID drives. The other only a single drive.

    I guess this exercise is good if for nothing else to try to reduce IT power usage.

    Thanks again.
  • bryanlbryanl Solar Expert Posts: 175 ✭✭✭✭✭
    Re: Which batteries to use?

    If anyone can come up with an objective measure that is actually meaningful and useful for making battery purchase decisions for a "true" deep cycle battery as contrasted to a 'not true' deep cycle, please let me know.

    It looks like there are two factors surfacing here so far. One is the size of the battery bank needed and the other is the specific battery recommendation.

    For size, a good rule of thumb is that you need enough battery to last a weekend (2 days, 3 nights) without going below 50% DoD of rated battery capacity (20 hour rate).

    For specific battery recommendations, you need to look at factors such as planned environment, charge rate expectations, use profiles, cost efficiency, and marketing hype (e.g. "true deep cycle" ;-) ). The type of battery (flooded, sealed, AGM, gel) is the first decision and then you get into voltage, sizes, and other specs before you get into brand and model.
  • www.HyperionLED.comwww.HyperionLED.com Registered Users Posts: 7 ✭✭
    Re: Which batteries to use?

    I assume everyone here may have heard that there are some partnerships starting with the big auto manufacturers to recycle the batteries of electric cars and hybrids to be re-purposed as off grid battery packs.

    Here is an article about nissan:

    http://green.autoblog.com/2009/10/21/nissan-and-sumitomo-launch-venture-to-reuse-automotive-batteries/

    I hear recyclers have a $200 finders fee for these old batteries.

    Has anyone heard of a source for these batteries. Do you know the voltages of different car makes? What will be the challenges of these advanced batteries for off grid storage?
    And what will they cost? Could be a huge new source of affordable battery storage for off gridders.

    Thanks
  • mike95490mike95490 Solar Expert Posts: 9,089 ✭✭✭✭✭
    Re: Which batteries to use?

    Problem is, the batteries need special chargers, that don't exist at the RE level. 48V is the "max" consumer voltage, car batteries are 200 - 300V so they would have to be broken up out of their management pack.
    I suppose there could be a market for a Solar charger for them, but not yet. Some talk about the homebuilt EV LiFePh batteries and charg shunts working from standard RE charge controllers, but nobody's "done" any that I know of.
    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 ,

  • RWBRWB Solar Expert Posts: 168 ✭✭✭✭✭
    Re: Which batteries to use?

    Lithium Iron Phosphate LFP Batteries are the way to go if you want the best batteries. See our LFP Battery thread for all the info. They basically work the same as regular 12V AGM batteries, except 200Ah 12.8V batteries weight 54 pounds vs 150 pounds and they last up to 10 times longer if you discharge them to 80% DOD every day. Tons of advantages over lead acid. I use the LFP batteries every day.
  • mike95490mike95490 Solar Expert Posts: 9,089 ✭✭✭✭✭
    Re: Which batteries to use?
    RWB wrote: »
    ..... I use the LFP batteries every day.

    I've missed where you have described your system - do you have a web page or something somewhere?
    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 ,

  • Renewable RayRenewable Ray Registered Users Posts: 4
    Re: Which batteries to use?

    Are special batteries required or advisable for solar systems? The batteries I see at various places on the internet seem expensive compared to an average 12 volt car battery. Can I just get an array of car 12 volts and a standard 120 volt inverter not designed particularly for solar?

    Are there safety issues associated with keeping any type of batteries indoors? I have 3 computer servers that run 24/7 that I want to run off of solar during the day and batteries charged by solar at night. I'd be keeping the batteries in my office, but would put outside if there are any issues with inside.

    Thanks!





    Please....friends don't let friends use car batteries or even Marine batteries. the "cheap" solution is golf cart batteries. There is no saving money buying car batteries. It's just a waste of time Horton, hopefully you have not found this out the hard way since your post. :cry:
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