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Getting lost in Battery Land - What to do?

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  • Getting lost in Battery Land - What to do?

    I am getting really interested in doing something with Solar and want to start with my Travel Trailer. Initially I thought it would be great to be able to "Dry
    Camp" for days and use the AC, Microwave etc... but soon realized I would need another trailer to haul the battery bank required for such a thing.

    So now I am concerned with basics such as 12VDC systems (Lighting,Refrigerator & Water Heater ignition) and for AC ( Laptop, Phone, TV and limited Microwave usage, potentially Refrigerator on AC and not LP and/or Water Heater on AC not LP as an option in a pinch)

    I believe I have consumed enough information to understand everything except "Battery Storage". I have read a lot in this forum and others and understand enough to know what to do for bank sizing, setup, etc. But my concern is, which type should I invest in and for that type, I want to understand exactly how to monitor, service and take care of, in order to maximize whatever I end up spending on them.

    Almost everyone suggest SLA or True Deep Cycle, but I started wondering about the fact of travel and availability of replacing something that I would typically have to order. I like the Idea of using something that I can grab off the shelf at some Auto Parts store or near by Wal-Mart... and if SHTF I can grab something that is more readily found near by, especially near a lake for a hybrid battery.

    So am I thinking wrong? Should I really spend 30 to 60% more money on something like a Trojan Flooded or SLA large capacity?

    What I do understand about a Hybrid (which might be wrong?) is if I wanted to power my water heater at large DC Amp rates, the Hybrid sorta handles the surge and demand for short periods of time very well? The Refrigerator Compressor and Water Heater Elements are significant AMP users, however they are not running for long periods of time. They run for 5-10 minutes per cycle and the number of cycles depends on the usage and outside temp.

    So I really wonder if I would be really saving money on the advantage of Availability and Cost if I use a Hybrid, or will I find myself replacing frequently enough due to not servicing correctly or the inherited limited cycle life etc?

    Does anyone have experience in the RV/Travel Trailer RE usage that has been there done that?

  • #2
    I have designed and had successfully built, a lighting system for a exhibit using thousands of LED's and hundreds of watts of lighting.
    NSW - https://www.youtube.com/watch?v=Y8AsKhlct2I

    You are likely far beyond a 12V systems capability. But first, you need to add up your power budget. Forget about heating anything with electricity, except for 30 seconds with a microwave. Heating requires an even larger system or fuel of some sort.

    You can heat water on the roof with a solar water heater, or get it at least hot enough it take the pain out of finishing it with a bit of propane.

    They have small camping tankless heaters that use a "D" battery to spark the flame. Household rated ones use a 400W glow coil that stays heated up while the flame is on.

    Let's say your fridge, and other loads take you to 3,500wh consumed per day. You Need a battery bank at least 3x that size (other people say 5x, you can work out the math for that) to only stress the batteries to 33% discharge daily. The deeper the daily discharge, the shorter the battery life. So 10,500wh bank would be
    875Ah @ 12V
    440Ah @ 24V
    220Ah @ 48V (8, GC2 batteries in series. 6V, 200ah ea)
    and would need to be recharged with 4,550 watt hours each day (battery recharge losses) Figure 4 hours of sun (solar charging hours) and that gives you a 1,200 watt array

    Each system (12v, 24v, 48V) will need the same amount of batteries & watt hours, but the less parallel batteries, the better. http://www.smartgauge.co.uk/batt_con.html


    A 1200w array into a charge controller requires:
    12V = 100a controller Might possibly be done with a Classic 150 @ 90A, or use 2, 60A controllers
    24V = 50A controller Many 60 A controllers
    48V = 25A controller many more 30A controller options

    So it all depends on your loads.

    Batteries have a finite calendar lifetime, in use, or sitting on the shelf, look at the warranty sticker, 24mo, 36 mo, 72 month .
    Is a $500 6 year battery better than buying 2, $200 3 year batteries ?
    Last edited by Mike90250; 06-10-2015, 02:14 PM.
    Powerfab top of pole PV mount (2) | 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

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