Solar Electric Car & Computer Battery Backup

I'm new to actually working with solar and batteries. I have a solar panel and batteries. The solar panel goes on an electric car which is to be built in the coming months. In the mean time I'd like to hook up the panel and charge several 12 volt batteries (in parallel) and use the batteries as battery backup for my computer system. The solar charges 12V.

Recommendations of what size wire to use, what connectors to use, what circuit breaker to use and other parts are much appreciated.

1. I need to make up a cable from the car to house - 50 feet male male 240v connectors (so it can't be mistaken for 110v) - to plug in to car and run cable to house and plug into house. In the interim the cable will go direct to the batteries connected to the panel near where the car will be parked.

2. Another cable for inside the house, 10 feet male 240V plug - to battery clips that connect into my computer's battery back up system. This replaces the 12V motor cycle battery and should allow the computer system to run much more than the few minutes the motor cycle battery does. When the car batteries are in use the 120v will be unplugged so the car batteries will be in use.

3. Hopefully there is a simple way to put a switch in to turn off the alarm for no 120v power. What is an appropriate switch for this?

4. Also is there a simple way to make a switch so I can switch between the car batteries and the motor cycle battery of the battery backup system?

5. I assume there should be a circuit breaker for when there is a short circuit. I assume the circuit breaker should be located with the car batteries. What kind is appropriate?

Once I have mastered this, and as funds are available I'd like to add solar panels to the house and run more of the house with solar. So I want to allow for expansion. The 50' cable will be the main line into the house from all the batteries. From there electric devices can be added.

For now, suggestions for the actual parts to use for the two cords, switch and circuit breaker are much appreciated.

Suggestions for a viable alternative to the 240V plug/receptacle on the car and house for the 50' extension cord are welcome too. And suggestions for anythings I've over looked are much appreciated.

I see I have much to learn.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,408 admin
    Re: Solar Electric Car & Computer Battery Backup
    Easyabcd wrote: »
    I'm new to actually working with solar and batteries. I have a solar panel and batteries. The solar panel goes on an electric car which is to be built in the coming months. In the mean time I'd like to hook up the panel and charge several 12 volt batteries (in parallel) and use the batteries as battery backup for my computer system. The solar charges 12V.

    Oh boy... You ask lots of questions--but some are difficult to answer--assumes lots of facts that we don't know from your initial post.

    But, generally, an electric car is not very efficient (or powerful) on 12 volts.

    Also, a single 12 volt solar panel is typically less than a 100 watts. Even in sunny areas, that is going to be good for a mile or two per day worth of electric charge--if you are in Seattle--could be much less.

    You are planning on using the 12 volt batteries as a backup to your utility power for your computer system? Do you have an Inverter that will work as a UPS--or is this just to run the system for a few hours after the lights fail? In any case, make sure the batteries are well ventilated and that you use a charge controller to ensure the batteries are probably charged (lots of options here--depends on the size of the panels and such). Also, depending on the amount power your computer system uses, a single solar panel may not provide much "computer run-time". Make sure you don't undercharge your batteries while using the computer on solar power--a very good way of damaging the batteries for long term use.

    Recommendations of what size wire to use, what connectors to use, what circuit breaker to use and other parts are much appreciated.
    1. I need to make up a cable from the car to house - 50 feet male male 240v connectors (so it can't be mistaken for 110v) - to plug in to car and run cable to house and plug into house. In the interim the cable will go direct to the batteries connected to the panel near where the car will be parked.

    Make sure you have a good insulation (or conduit) for the wire... And/or make sure you use a direct burial and/or UV rated insulation for your wire.

    Use this Voltage Drop Calculator (Excel Spreadsheet) to decide the gauge of the wire you want to run (typically, no more than 1-2 volts of drop for a 12 volt run).
    2. Another cable for inside the house, 10 feet male 240V plug - to battery clips that connect into my computer's battery back up system. This replaces the 12V motor cycle battery and should allow the computer system to run much more than the few minutes the motor cycle battery does. When the car batteries are in use the 120v will be unplugged so the car batteries will be in use.

    Sounds like you may be replacing the batteries in a UPS... The UPS should have its own internal charger... You will want to check the charging voltage to ensure it is compatible with your "car batteries".

    And your "car batteries" are Deep Cycle type, I hope (perhaps AGM?). Proper charging (and watching battery electrolyte levels) will go a long way to ensuring long battery life. Placing much larger batteries on the UPS--make sure you have some fuse or breaker in the battery lead to prevent meltdown/fire in case the UPS or wiring fails.
    3. Hopefully there is a simple way to put a switch in to turn off the alarm for no 120v power. What is an appropriate switch for this?

    Mine has an Alarm Silence switch--but just cutting the pezo electric transducer lead and installing a simple Radio Shack Switch will probably take are of the problem.

    Also, be very careful when wiring up your inverter--it is very possible that your battery leads may have 120+ VAC on them (from the wall outlet and/or inverter connections). Check carefully with a voltmeter that you don't accidentally end up "energizing" your "12 volt" solar panels with 120+ VAC relative to ground.
    4. Also is there a simple way to make a switch so I can switch between the car batteries and the motor cycle battery of the battery backup system?

    Look for a Marine Battery Transfer switch (don't know anything about the vendors or products). Not too expensive and should do what you need.
    5. I assume there should be a circuit breaker for when there is a short circuit. I assume the circuit breaker should be located with the car batteries. What kind is appropriate?

    Yes, a fuse or CB is appropriate--as close as practicable to the battery (so that the chances for other shorts are much less). You want to use a DC rated breaker/fuse... Depending on your power requirements, a simple car fuse (or look for fuses used in large audio systems for cars), or marine will work fine. You can also use a breaker (much more expensive), and there are a few sold here. The Square D QOU breakers might be your best bang for the buck and available locally (can be used in Home CB panels--IIRC).

    Remember the breaker/fuse protects your wiring--so it should never be larger than the wire ampacity it is protecting.
    Once I have mastered this, and as funds are available I'd like to add solar panels to the house and run more of the house with solar. So I want to allow for expansion. The 50' cable will be the main line into the house from all the batteries. From there electric devices can be added.

    For now, suggestions for the actual parts to use for the two cords, switch and circuit breaker are much appreciated.

    Suggestions for a viable alternative to the 240V plug/receptacle on the car and house for the 50' extension cord are welcome too. And suggestions for anythings I've over looked are much appreciated.

    Once suggestion on the 240 VAC plug... Many people tend to use twist lock plugs because they are never found around the typical home. However, if you are plugging into a vehicle/movable device (battery on trailer, etc.)--I would suggest that you use a "straight blade" version of the plug...

    Nobody plans on driving away and forgetting to unplug the vehicle--but everyone does (my first hearing of this story is from our local fire department some 45 years ago--firemen kept tripping on cord and unplugging the engine heater/battery charger--"fixed" that by changing to twist-lock--and almost immediately thereafter, ended up pulling the outlet out of the wall on their next emergency run--heard of other stories involving elk, deer, moose and such and engine block heaters in the northwest).

    Good Luck and let us know how the electric car goes!
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Solar Electric Car & Computer Battery Backup

    Article:
    Use your EV / Hybrid car as a UPS for your house
    http://www.priups.com/exec-summary.htm

    One way it's been done.
    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 ,

  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    Re: Solar Electric Car & Computer Battery Backup

    Another thing to keep in mind most UPS systems are not intended to run for any length of time. They assume whatever the load is will run the battery dead before overheating the electronics. So say it's rated for 400watts, if you’re running 200watts on it, it might last 20 minutes at which time the battery would go dead and the small inverter would be at the point of overheating.

    Some of the larger units, especially ones with external batteries are made to run constantly since you could whatever batteries you wanted.

    What is the battery bank in your electric car? What voltage and how many batteries?
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI