PV backup system using 48V golf cart?

Hey everyone:
I'd like to design a 6K or 7K PV grid-tie backup system, and use my 48V golf cart as the backup battery pack. It has 8 Trojan T-105 deep cell 6V batteries, 240 AHrs each.
By calling both Outback and Xantrex I've been told that the inverter/chargers need the battery pack to operate. This means if I disconnect the golf cart for even a few minutes, the whole system goes down. Can anybody come up with a way this idea will work? I want the backup for emergencies, but that may only be once or twice a year during brownouts. I've already got the golf cart, and I also have an EV conversion with 18/8V deep cell batteries which I could pull out and wire in the system if a prolonged outage occurred. My thinking is, why buy a whole new bunch of batteries to sit there all year, just to keep the PV system operating?
Anyone have any clever ideas to make this work?
Greg

Comments

  • BB.BB. Posts: 27,886Super Moderators, Administrators admin
    Re: PV backup system using 48V golf cart?

    Not quite clear on what you want to do... But, you can do several variations--depending on exactly what you want to do.

    First, assuming no solar panels. Then, it is as simple to properly connect (wire gauge, fusing) the right voltage inverter to the battery bank. The inverter will supply AC power to your load via extension cords.

    And, the inverter does need battery power to operate.

    There are inverter chargers where you wire home AC to the inverter, then wire the AC output to a local "emergency power" panel in the home. And wire your DC connection to a plug on your golf cart. When Home AC power if present, the inverter simply passes AC In to AC out and also uses the AC power to charge your golf cart batteries. When the AC fails, the inverter turns on and supplies AC out--just a giant UPS. The problem may be what happens to this type of Inverter/Charger when you disconnect the 48 VDC battery bank. Does the AC in to AC out function still work OK? You probably need a switch to turn off the DC power plug before you plug/unplug to reduce the chance of arcing your DC power plug. You would need to call the Inverter Company and see what they say (safety, reliability of the inverter).

    If you have solar panels... No, you cannot simply connect solar panels to a standard inverter and get emergency power during the day (even if the array larger than the inverter). However, you could connect the a solar charge controller from the panels to the 48VDC battery plug of the golf cart and charge it during the day (when the golf cart is plugged in). You can probably simply connect it to the same circuit as the 48 VDC inverter battery connections--but I would check with the Vendor(s) and make sure that they are OK with this (solar charger + inverter connections, but battery bank disconnected at times--aka golf cart).

    Lastly, if you have Grid Tied Solar array/inverter--this, so far, has been a difficult beast to use during emergencies. The standard Grid Tied inverter is designed to only work with Utility Power and for safety, shut down during brownouts/power failures. And, a Grid Tied inverter uses much higher voltages than a MPPT type solar charger (~200-600 VDC vs ~72-140 VDC). So you are kind of out of luck being able to directly connect a MPPT controller in emergencies to your Grid Tied Solar Array.

    There are a couple of solutions possibly--one is to have a jumper panel / switch where you can "rewire" your Array's output voltage to be compatible with a MX-60 type solar charge controller. Or, there are a few installations out there where you can have an Off-Grid type system with inverters that can also perform grid tie type functions too... But even this hybrid system requires the battery bank to be 100% connected all the time.

    In the end, using an Electric Vehicle as a handy battery bank is possible--but not always real handy.

    And there are folks out there than have even converted a Toyota Prius into a hybrid generator (connect the low or high voltage battery packs to a UPS type inverter). Just leave the "key on" and the Prius gas engine will automatically cycle on and off to keep the battery bank within voltage/charge specifications (I am sure that it violates the warranty 10 different ways).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?

    What I'd like to have is some power available during the day if a prolonged outage occurred. With a GT system, as you said, Bill, the solar array is useless when the grid goes down. A GT system with backup is the solution, except it requires a large bank of batteries (which may never be utilized if the grid stays up, or used infrequently if there's a 5hour brownout twice a year).

    Optimally, the system setup I'm searching for would be my 6K or 7K solar panel array would be grid-tied under normal conditions. If the grid goes down, I plug in the golf cart, which keeps the fridge running and perhaps a tv for news. The solar panels keep the golf cart batteries charged up during the day, and I keep the load low from the house at night, so as not to deplete the golf cart batteries too much.

    During the 2003 California fires, grid power was off in my area for eight days. If something like that happened again, but this time I have a solar PV system, and a golf cart with 48V sitting there, it seems it would be worth a little extra expense to find a way to keep minimal home power going for the duration.

    I know I could buy a simple inverter to run from the cart with extension cords going into the house, but that wouldn't solve the problem of charging the cart back up. Is that what you meant by adding a charge controller to the PV array? Then it would be a matter of throwing a switch to go from grid-tie to charging batteries?
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?

    Greg:

    Gaia Technologies (http://www.gaiapowertechnologies.com/) makes a charge controller that will connect to a high voltage solar array & charge a 48v battery bank. The controller is rated up to 600Vdc, 3Kw. It is self current limiting, meaning that you could connect it to your 6 or 7 Kw array with no problem. Or, you could connect two of these controllers (6Kw total) to your array for more offgrid power. This would connect directly to your high voltage solar array & would charge your 48 volt battery bank. Just put a 600V DC rated disconnect between the charge controller & the solar array. You would switch the disconnect on or off as needed for charging the batteries. You will still need to get an inverter to make the 120Vac for your appliances, etc.

    The link to Gaia above does not show their charge controller, but it does have the 800 number to call them. The last time that I spoke with them, the list price on the contoller was $1300. They are in the process of getting UL approval.

    JB
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?
    gregmk wrote: »
    I'd like to design a 6K or 7K PV grid-tie backup system, and use my 48V golf cart as the backup battery pack. It has 8 Trojan T-105 deep cell 6V batteries, 240 AHrs each.
    By calling both Outback and Xantrex I've been told that the inverter/chargers need the battery pack to operate. This means if I disconnect the golf cart for even a few minutes, the whole system goes down. Can anybody come up with a way this idea will work? I want the backup for emergencies, but that may only be once or twice a year during brownouts. I've already got the golf cart, and I also have an EV conversion with 18/8V deep cell batteries which I could pull out and wire in the system if a prolonged outage occurred. My thinking is, why buy a whole new bunch of batteries to sit there all year, just to keep the PV system operating?
    Anyone have any clever ideas to make this work?
    Greg


    That sounds like a great use for a golf cart.

    How much use does the golf cart see: daily, weekly, monthly...? It could affect the ability to keep it charged with solar.

    Is the 6-7K solar array kw or k$? If kw, then it is way too much for your requirements to run a TV and fridge during grid outages. If you are trying to sell back to the grid as much RE as possible then a 6-7kw array would require more charge controllers, more inverters, more breakers, wiring, etc. The cost would rise substantially.

    If you are only looking to power emergency loads and sell back nominal power to the grid, a 1kw - 2kw array would be more appropriate. The array, a single 48v inverter, MPPT charge controller plus installation incidentals would be required. If you use brand "O", you would need to get a Mate to disable the charger in the inverter unless you don't mind the inverter charging the battery. You also need the Mate to optimize your system.

    Although brand "O" recommends a 100ah minimum battery, I'd get four small VRLA UPS type batteries to connect to the system while the golf cart is in use. You could get four for under a hundered bucks, think deer feeder batteries, ~$15 each. Set charge rate of the MX-60 to the max that the small battery would support when you use it and back to the cart charge rate when using it, a simple process with the MX-60.

    If the grid happens to go out while you're using the cart, battery voltage will drop rapidly in the little battery and the inverter will simply disconnect. When you put the cart back online, the inverter will be able to power the emergency loads, the solar array and controller will be able to charge the cart battery.

    Use a DC battery selector switch to switch to/from the cart battery and make a super heavy duty (like 4/0) extension with Anderson connectors (WW Graingers stocks them) to connect/disconnect the cart battery. Here http://www.outbackpower.com/pdfs_wiring_diagrams/ps2ac-dcsingle.pdf is a link to a wiring diagram comprised of array, charge controller, battery and inverter.

    I created a little Excel solar calculator that will help with some of your component selection. You should be able to find it on my profile here, if not, I can repost it.


    Cheers

    Bad Apple
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?

    Hi, JB:
    I do like your idea for the Gaia charge controller, since it would limit all that power coming of the large solar array. I want to offset my 1400Kwhrs per month electric bill as much as possible, so I need that large of an array.

    Let's suppose on my 7Kw Pv system I use a SunnyBoy SB6000US inverter for grid-tie. Would the Gaia charge controller be something that is disconnected from the system until an emergency arose, then I'd flip a disconnect to take the Sunnyboy inverter off line, and flip another disconnect to start charging the golf cart? Or could the Gaia controller stay hooked up all the time, keeping the cart battery pack charged after use? Also, regarding the inverter to operate appliances from the cart during emergencies, would that inverter be hooked up to the cart at the same time the charge controller is charging the batteries during the day? Do you have any recommendations for an inverter that would supply perhaps 3Kw for the appliances by using the golf cart bpack?

    Regarding use of the golf cart, I live on a 4 acre property and use it to drive down to get mail, newspapers, and occasionally to haul clippings and such. On average three or four times a week for times usually five minutes (for the mail and newspaper) or up to an hour at a time for yard work. That means it's usually just sitting around.
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?

    Hi, Bad Apple:
    To answer your question, I'm wanting a 7Kw system to send as much back to the grid as possible. As I mentioned above, my current electricity usage is about 14Kwhrs a month. The golf cart is used sparingly (see my reply to JB).

    To simplify what I'm trying to do, imagine you have a 7kw grid-tie PV system and while the grid is working everything's rosy (maybe you already do). Then the grid goes down for a day, week, or month. You have this expensive solar system just sitting there as you walk around in the dark and the milk you bought yesterday spoils. You have plenty of batteries in your golf cart, but how can you use them? You hook up a cheap inverter and run an extension to the fridge and maybe the TV and a few lights, but the batteries run down in a few hours. Then what? How to charge the golf cart batteries from the solar?

    So I'm trying to look ahead and think of a way to handle emergencies without having a typical battery backup system which would have idle batteries sitting there for years at a time. In addition to the 8/6V batteries in the cart, I also have 18/8V batteries in my EV conversion. I'm thinking enough already with the batteries, I've got plenty. How can I use them if the grid goes down?
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?
    "Hi, Bad Apple:
    To answer your question, I'm wanting a 7Kw system to send as much back to the grid as possible. As I mentioned above, my current electricity usage is about 14Kwhrs a month. The golf cart is used sparingly (see my reply to JB).

    To simplify what I'm trying to do, imagine you have a 7kw grid-tie PV system and while the grid is working everything's rosy (maybe you already do). Then the grid goes down for a day, week, or month. You have this expensive solar system just sitting there as you walk around in the dark and the milk you bought yesterday spoils. You have plenty of batteries in your golf cart, but how can you use them? You hook up a cheap inverter and run an extension to the fridge and maybe the TV and a few lights, but the batteries run down in a few hours. Then what? How to charge the golf cart batteries from the solar?

    So I'm trying to look ahead and think of a way to handle emergencies without having a typical battery backup system which would have idle batteries sitting there for years at a time. In addition to the 8/6V batteries in the cart, I also have 18/8V batteries in my EV conversion. I'm thinking enough already with the batteries, I've got plenty. How can I use them if the grid goes down?"

    That was considered in my reply, I just didn't have certain specifics that you have now provided. I offered suggestions of how to accomplish the connections and how to allow the solar to operate in the absence of the cart.

    "Let's suppose on my 7Kw Pv system I use a SunnyBoy SB6000US inverter for grid-tie. Would the Gaia charge controller be something that is disconnected from the system until an emergency arose, then I'd flip a disconnect to take the Sunnyboy inverter off line, and flip another disconnect to start charging the golf cart? Or could the Gaia controller stay hooked up all the time, keeping the cart battery pack charged after use? Also, regarding the inverter to operate appliances from the cart during emergencies, would that inverter be hooked up to the cart at the same time the charge controller is charging the batteries during the day? Do you have any recommendations for an inverter that would supply perhaps 3Kw for the appliances by using the golf cart bpack? "

    The SB6000US is not a battery backed inverter, it will not power loads when the grid is down: http://download.sma.de/smaprosa/dateien/4182/SB6000U-13_SE2506.pdf

    The energy path for the system you want to build is >sun >array >charge controller >battery >inverter >AC loads. Think of it as a capital "T" with the sun, array and charge controller on the left of the horizontal bar, the inverter and AC loads on the right side of the horizontal bar and the battery at the bottom of the vertical leg. If the battery is fully charged, the array output "bypasses" the battery and feeds directly into the inverter. In that case, if the AC loads exceed array output (disregarding inefficiencies), the inverter offsets the loads by partially feeding them, the grid provides the remainder. If your AC loads are lower than your array output, your inverter powers those loads and sells the excess power to the grid. To produce power in the absence of the grid, you must use a battery backed grid tied inverter.

    Cheers,

    Bad Apple
  • BB.BB. Posts: 27,886Super Moderators, Administrators admin
    Re: PV backup system using 48V golf cart?

    I think, that the On-Grid / Off-Grid power requirements are so different, that you would be better off building your "main system" as a Grid-Tie and a small system as Off-Grid with an MX-60 inverter--using either using part of the original array ("center tapping" one or two strings for the MX-60 type controller--and using switches to totally isolate the sub array when you need off-grid charging) or simply budgeting 10-20% of the array to the dedicated MX-60 + Inverter system (you could always run a few loads like Fridge/computers to make your system a big solar charged UPS--and the inverter(s) can be tied to the Grid to provide utility "backup" and backup charging)...

    The reason I am suggesting this is that a 7kW Xantrex Grid-Tie with battery backup will probably require a heafty battery bank for normal operation--something that you are not really into at this time.

    Lastly, just use a backup generator for your backup power... Not as handy as the solar--but probably more cost efficient. Somewhat depends on what you are "protecting against" would suggest your fuel type... I am protecting against earthquakes, so I am using ~25 gallons of stabilized gasoline with a Honda eu2000i 1,600 watt generator--will last me a week or two--plus I have a portable generator for emergency/other uses.

    Natural gas powered generator would be nice if you are not expecting gas interruptions... Ideally, using propane would solve many issues with safe, long term, fuel storage (if allowed in your area).

    If there is a system that is a MX-60 type controller that handles 600 VDC panel power--I would really like that for my system.

    The Gaia Solar did not seem to list the components individually--I will take a bit more time to go through their website.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?

    Hi, Bad Apple:
    I considered using an inverter/charger system from Outback with a MX-60 charge controller, but when I talked to Outback they said the MX60 couldn't handle the input from such a large array. If that's so, my array's output is too large to use that charge controller. Perhaps the setup you describe but with the Giai controller JB mentioned that has current limiting? Then use the deer feeder batteries you mentioned to keep the system running when the golf cart is being used?

    I took a look at the Giai website and found the following info:
    http://www.gaiapowertechnologies.com/Charge_Controller.html
    It sounds like I could use any normal GT inverter, tie in their charger controller, and the existing typical GT inverter would work normally until the power went out. Then their charge controller would take over and charge the 48V battery pack. I'm not sure, but it sounds like it wouldn't matter if the golf cart was plugged into the system or not, unless of course the grid was down. I would hope that in that event, I could drag out some 4/0 cable and plug the cart in as you suggested, then be up and running off the solar array.

    Does this sound right?

    Thanks for your help,
    Greg
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?

    Hi Greg,
    It sounds like I could use any normal GT inverter, tie in their charger controller, and the existing typical GT inverter would work normally until the power went out. Then their charge controller would take over and charge the 48V battery pack.

    Looks like you just about have it. Just use a normal GT inverter, & the Gaia charge controller will charge your batteries at the same time as your grid tied inverter is feeding into the grid. When the grid fails, it simply will disconnect itself from the grid. The charge controller will continue to charge the batteries as long as the solar array is producing power. The charge controller is connected to the PV array wiring in parallel with a GT inverter.

    You will still need an inverter for you off grid loads. I suggest that you use a pure sine wave inverter so that you won't damage any appliances, computers, etc that you will be using. Most (if not all) newer refrigerators (and other appliances) are actually processor controlled.

    I haven't seen one of these Gaia charge controllers yet, but I plan to use one for a project I am working on. I don't know about leaving the controller energized without the battery bank connected, but a call to Gaia should get you the answer. I would recommend that you install a disconnect (600Vdc rated) ahead of the charge controller for safety & code compliance. If you don't shut down the charge controller before connecting the cables to the batteries, you will produce one healthy electrical arc. And, just as a reminder, NEVER make the last cable connection at the battery!!

    JB
  • BB.BB. Posts: 27,886Super Moderators, Administrators admin
    Re: PV backup system using 48V golf cart?

    Remember too that most (all?) Grid Tie controllers ground one side (usually, but not always) the Negative side of the Solar Array and, for example, the Xantrex GT series uses a 1 amp fuse in the ground lead to detect "ground faults"...

    So, you have a real issue if you choose to parallel a Grid Tie inverter (no isolation switch(es) with a solar battery charger like the Gaia unit... It would appear that you need to 1. ensure that the ground polarities are the same (negative/negative or positive/positive with Sunpower panels), and 2. that both controllers connect to one and only one DC ground--at the same location. --Unless, of course, the Gaia (or equivalent controller) has an isolated PV In to DC out connection...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?
    gregmk wrote: »
    Hi, Bad Apple:
    I considered using an inverter/charger system from Outback with a MX-60 charge controller, but when I talked to Outback they said the MX60 couldn't handle the input from such a large array.

    For large systems you can connect multiple MX-60's in parallel at the battery. DISREGARDING TECHNICAL DETAILS FOR NOW, the MX-60 can output 60 amps at battery voltage. 60v X 48a = 2880 watts. Let's say this is what you can expect to put into the MX-60. Three MX-60's would cover your 7kw array.

    I took a look at the Giai website and found the following info:
    http://www.gaiapowertechnologies.com/Charge_Controller.html
    It sounds like I could use any normal GT inverter, tie in their charger controller, and the existing typical GT inverter would work normally until the power went out. Then their charge controller would take over and charge the 48V battery pack. I'm not sure, but it sounds like it wouldn't matter if the golf cart was plugged into the system or not, unless of course the grid was down. I would hope that in that event, I could drag out some 4/0 cable and plug the cart in as you suggested, then be up and running off the solar array. Does this sound right?

    Yes and no. Yes, it will charge your cart but if you are calling the Sunnyboy SB6000US a "normal GT inverter" then, no, it will not work. The SB6000US MUST SEE THE GRID TO OUTPUT AC.

    The press release at the url referenced leaves out a lot of information but looking at the products' brochures etc., they are RE powered UPS systems. I didn't see any reference to selling back to the grid.

    Let's assume you already have the SB6000US and the cart battery. If you look at the "Residential Systems" tab and then the "Power Tower M", here, http://www.gaiapowertechnologies.com/download/Gaia7200M.pdf It assumes you have a "normal grid tied inverter" and solar array. Their system comes with a cabinet, charge controller, battery and inverter. This looks like a run of the mill UPS with a high input voltage DC charge controller for use with RE. Basically you will have one system to sell to the grid (SB6000US) and another (the gaia system) for backup power. Going this route, you would not even need the cart battery.


    What I can envision (draw it on a piece of paper if it helps):

    Three parallel solar arrays, each with its own circuit breaker to the respective charge controller.

    Wiring from charge controllers to circuit breakers to the common of a battery selector switch.

    Terminal A of the BSS goes to 4/0 cable to circuit breaker then to the cart battery. Anderson connectors make up at the battery (leaving a little pigtail under the seat)

    Terminal B of the BSS goes to the small battery, fused and permanently connected.

    Another set of suitable large cables goes from the BSS common to a circuit breaker and then to the DC side of the inverter/inverters.

    Inverter AC input from grid

    Inverter AC output to sub panel for critical loads.

    Other than the small battery, it's connected as a "T" as is described earlier.

    Here's a more or less turnkey system that would do what you're trying to accomplish: http://www.outbackpower.com/pdfs_brochures/PS2%20System-Final.pd
    You may need to add another MX-60 or two depending on final system configuration and regional WX conditions.

    Cheers,

    Bad Apple
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?

    As explained to me by Gaia, the Gaia charge controller for use with an existing (or new) "high voltage" solar array is available separately. It does not come with their PowerTower, unless you order it. It is not shown on their website. You can order just the "high voltage" solar charge controller (600Vdc max input/48Vdc nominal output). Your existing (or new) GT inverter remains connected to the grid. You only connect the charge controller to the wires coming from the solar array to the GT inverter, a parallel wiring configuration. You will need an inverter with a 48Vdc input & 120Vac output. You don't need to buy the Gaia PowerTower.

    Call Gaia at 888-424-2669 to answer your questions.


    This is from an email that Gaia sent me:

    3000 W Battery Charger for Photovoltaic Applications

    Benefits
    - Keep your array producing power even when the grid is down
    - Extend the power capacity of your battery system in blackouts
    - Have power available for days in good solar conditions

    Features
    - Compatible with all 600 VDC arrays and inverters, new or retrofit
    - Wide input voltage range (65 - 600VDC)
    - Advanced maximum power point tracking (MPPT) software
    - Advanced battery charging algorithms

    General Specifications
    Power throughput - 3000 W continuous (self-limiting)
    Peak efficiency - 92.8%
    Inverter Technology - High-frequency pulse width modulation with proprietary
    control algorithms

    Electrical Specifications
    Input voltage (solar) - 600 VDC open-circuit
    - 200 – 400 VDC full power range
    - 65 – 600 VDC operating range
    Output voltage (battery) - 48 VDC nominal
    - 40 – 60V operating range
    Max continuous current - 60 amps (self-limiting)
    Max power point tracking- 65 – 480 VDC range
    - Proprietary MPPT algorithm
    Array configuration - Monopole negative grounded
    Max. DC ripple (solar) - <5 %
    Max. DC ripple (battery) - <5 %

    Environmental Specifications
    Size - 7.25 W x 4.5 D x 16.25 H
    Weight - 10 lbs
    Temperature - Operating: -20 to 40°C
    - Storage: -40 to 60°C
    Humidity - 0 to 95% non-condensing
    Cooling - Forced-air cooled
    Elevation - 6,000 feet without derating
    Enclosure - NEMA 1 indoor

    Safety and Protections
    LED Monitors - Power-On / Running / Fault
    Automatic Faults - Over current, over voltage, under current,
    under voltage, over temperature

    JB
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?

    Sounds great, you guys. Bad Apple, you're right about the Giai page I sent you referring more to their complete backup system. I think there was somewhere where I read a news release of theirs that described just the charge controller, and it's ability to limit current from larger solar arrays. If so, and it can be bought individually, then it might be the way around installing multiple MX60s. I'll call them Monday and see. I appreciate the details you provided on the hookup.

    Funny, but speaking directly to tech guys at both Xantrex and Outback, they seemed intelligent about their products, but fairly baffled at using a golf cart as an ocassional battery pack.

    Glad I thought to post to this forum. Thanks to all.
    Greg
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?

    By the way, here's the url for the news article regarding the Gaia charge controller. Still not much in the way of technical info, but intriguing...
    http://www.gaiapowertechnologies.com/Charge_Controller.html
    Greg
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?
    gregmk wrote: »
    ...., then it might be the way around installing multiple MX60s. I'll call them Monday and see. Greg

    The gaia controller press release states it's a 3000 watt charge controller, which is about what the MX-60 is rated for. You would still need three of them for a 7kw array.

    Cheers,

    Bad Apple
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?
    Bad Apple wrote: »
    The gaia controller press release states it's a 3000 watt charge controller, which is about what the MX-60 is rated for. You would still need three of them for a 7kw array.

    On second thought, it requires three controllers (MX-60's or the gais's) only if you were trying to capture all of the solar to charge the battery or power backup inverters. Bill's second reply on the first page of this thread might be what you should do.

    I guess that the reason that I would prefer Brand "O"'s solution is that even with the modest battery in the cart, during an outage with good solar production, you could use most of that production - if the battery is fully charged, the battery is bypassed except for starting large loads.


    Cheers,

    Bad Apple
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?
    Bad Apple wrote: »
    it requires three controllers (MX-60's or the gais's) only if you were trying to capture all of the solar to charge the battery or power backup inverters.

    If the proposed 7kw system is rated 7kw STC, the CEC rating would be ~5.9kw. Then two 3kw controllers would capture most, if not all, of the solar output.

    JB
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?
    jbsolar wrote: »
    If the proposed 7kw system is rated 7kw STC, the CEC rating would be ~5.9kw. Then two 3kw controllers would capture most, if not all, of the solar output.

    JB

    One technical issue avoided earlier regarded just that. Because an array can produce voltage and amperage that can exceed controller specifications on clear, cold, sunny days, you should not connect more than 48 amps STC to the MX-60 (page 9 of the MX-60 manual here: http://www.outbackpower.com/pdfs_manuals/MX60_REV_B.pdf ). The actual limit should be based on local/regional WX extremes.

    I would be surprised if the gaia controller doesn't have a similar restriction but do not know that as fact. Other than their "glossies", I could not find gaia system documentation online. The multiple charge controller solution may be moot though.

    I realize greg isn't interested in gaia's inverters but according to their brochures they are either "square sine wave" or "sine wave 34 to 52 steps per cycle". That says alot to me, but I'm just a hack.

    Good luck with the system greg, keep us posted.

    Cheers,

    Bad Apple
  • System2System2 Posts: 6,290 admin
    Re: PV backup system using 48V golf cart?

    Greg,

    Did you ever get this backup system working? Please send us a quick update, as I am thinking of doing something similar with my 36v Ez-go and a 5.1Kw solar electric system.

    Thanks,
    Cabinman
  • petesuzpetesuz Posts: 2Registered Users
    edited September 16 #22
    Hey - I'm designing just such a system now - but only going for about 3kw of solar and using my Club Car and it's 48v battery pack (might have to beef up the internal charge port to battery wiring though to handle the 50-60 amps I'm thinking of putting through it).  And I'm sourcing a hybrid inverter / charger/ MPPT  controller (all in one) from China, as they seem to have some designs (and yes - some will do 240 vac split phase) with auto transfer switch and solar prioritization for consumption over grid, then finding one that has AC bypass when battery is disconnected. But even if the last few I have it narrowed down to doesn't meet all requirements I'm going to simply use a manual transfer switch between the main load center and the inverter and the subpanel - so I can switch AC source to the subpanel before unplugging the Golf Cart. Oh and the reason I'm looking to China is that the Schneider Conext SW 4048 is almost twice as much, But it would work too, but you need to also buy a separate MPPT charge controller etc. So you're looking at more than twice as much. Will try to remember to post as I progress. 
  • NANOcontrolNANOcontrol Posts: 78Registered Users ✭✭
    Is the controller external or part of the golf cart? I'm kinda reminded of some of the golf cart chargers I've seen.  They have a relay that won't power the charger until it sees battery voltage.  A lot of charge controllers do not want to see panel voltage till the battery is connected.  Some switching may be a consideration. 
  • mike95490mike95490 Posts: 7,902Solar Expert ✭✭✭✭
    Does your 48V golfcart use 4, 12V batteries, or 8, 6V batteries ?

    Either way, your nightime use will be quite limited because of the small battery 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 ,

  • littleharbor2littleharbor2 Posts: 1,027Solar Expert ✭✭✭✭
    Some are known to use 6, 8 volt batteries.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • petesuzpetesuz Posts: 2Registered Users
    edited September 17 #26
    Hi All, Well yes - it's a relatively small battery bank, if it were true off grid use, but I'm just wanting to supplement with solar, and offset the daylight hours use. And maybe a little backup for the rare grid failure - a giant UPS. We do get a lot of sun here in AZ, and so it will help, I figure it'll cut down the bill by about 1/4 to 1/3 - if I select the appropriate circuits for the sub-panel. And it will charge my cart for "free". I"m also getting a d/c pool pump from China, and will be running it off a set of panels. That will help quite a bit too. All still in the works though. Will update as I do.  Oh, and the batteries are 8v Trojan T-875's. And the Charge controller will be an MPPT ~ 60 amp -  and either stand alone or in the inverter. I may wire a separate direct to battery line of large gauge for that - maybe use an Anderson type connector. Still shopping and planning. 
  • MrM1MrM1 Posts: 277Registered Users ✭✭✭
    edited September 17 #27
    I think 1/4 to 1/3 might be optimistic IMHO unless Ur not running AC (from grid) and Ur current kWh from the grid is around or under 25 kWh. 10-15% has been my experience the past year  
    REC TwinPeak 2 285W 3S-3P 2.6kW-STC / 1.9kW-NMOT Array / MN Solar Classic 150 / 2017 Conext SW 4024 Inverter latest firmware / OB PSX-240 Autotransfomer for load balancing / Trojan L16H-AC 435Ah bank 4S connected to Inverter with 7' of 4/0 cable / 24 volt system / Grid-Assist or Backup Solar Generator System Powering 3200Whs Daily / System went Online Oct 2018 / System, Pics and Discussion
  • chuckklr98chuckklr98 Posts: 2Registered Users
    edited September 17 #28
    I'm already ahead of ya. 1080 watts solar, 3000 watt 36v inverters. 6 t105's. taylor dunn 148b is a beast.
    https://www.youtube.com/watch?time_continue=1&v=FSaTFt_0PU4
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