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  • EV batteries for energy storage

    I am putting this here so we don't clog poor WH6's "emergency ham radio power" thread with EV topics.

    A few weeks ago I was approached by a guy who works at a renewable energy company to buy the last EV this dealership had. They were discontinuing them and this one had a few scratches (it was their test drive vehicle) and they were selling it for $6000. It was going to be listed as new (hadn't been sold before) which meant it qualified for the $7500 tax credit. In other words, I would make money on the deal, even after sales tax/title/registration/insurance for a year etc.

    It was a Smart Fortwo pure EV - a two seater with battery, inverter and motor. No ICE engine. (Which also means no gas tank, alternator, exhaust system etc.) It was not a very good car - it had a range of about 70 miles and could barely hit 70mph on the freeway (a requirement around here.) I was tempted because 1) it was free; 2) it had an 18kwhr battery which I could use for other things. But the wife didn't want another car we don't have room for which I can see, so I passed it on to someone else at work.

    There are several ways to use an EV for grid storage. (This is something that a local company, Nuuve, is working on.) The way that works right now is to use the DC charging connector to connect directly to the HV battery. This gives you access to the ~400 volt bus of the vehicle and you can then charge (and discharge) the battery directly. 400V is close enough to the voltage of many inverters (like the StorEdge) that it will work directly. So you need a DC charger, the inverter and some control hardware to make this work. Nuuve has built half a dozen of these in San Diego already.

    The second, on the drawing board, uses the J1772 plug (standard EV charging plug.) You need to add a grid tie or hybrid inverter to the vehicle to make this work. This is harder in terms of hardware (need to add something to the car) but far easier in terms of the regulatory environment, since automotive equipment is certified and tested to different standards than normal inverters. The idea would be that:

    1) manufacturers would add this to their vehicles
    2) some EVSE companies (like Blink or Chargepoint) would then offer free charging to such vehicles, provided they can use 10% of their battery on occasion to power the grid
    3) during heavy load times, Blink would become a generation resource, and the local POCO would pay them peaker rates to provide that energy to them.

    The third is to just disassemble the car and use the modules. The Smart modules are great for home storage use - they are 15S15P, which means they are 54 volt nominal, and work well with 48 volt inverters. (Note that these are available in the EV aftermarket now and are pretty popular because they are cheap. But you still have to add a BMS.)

    I couldn't do 1) since the Smart doesn't have a DC connector, so I'd either have to hack the car to do 2) or disassemble it completely to do 3). I also thought that it made a little more sense to sell the car to someone who would actually use it, rather than just take it apart for the battery - which wastes 90% of the car. And those modules are available anyway.



  • #2
    Originally posted by jflorey2 View Post
    There are several ways to use an EV for grid storage.

    Sure it makes sense to use your Prius as a DC power source when the grid is down, being a hybrid it is also a great generator. I seem to recall that solaredge was working on that upgrade with their EV charging inverter.
    Those who do, do it!

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    • #3
      As I mentioned on the other thread, did you check to make sure the battery was included? Smart often leased the battery, at least that was what happened in my case.
      9 kW solar. Driving EVs since 2012

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      • #4
        Originally posted by Ampster View Post
        As I mentioned on the other thread, did you check to make sure the battery was included?
        Yep. Battery included; straight sale.

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        • #5
          The overall idea is pretty sound. There are some planned vehicles like Sono Motors which are designed more for V2G. The Nissan Leaf Chademo port also has more working V2G projects (though the official Nissan V2G system is ludicrously pricey). Not sure about the Smart, but the Leaf can drive a 2kw inverter from its 12v DC-DC converter. For off-grid use, some people can squeeze their power use into 2kw. I think the best-suited vehicle for this would be a totalled Leaf.

          If you decide you don't want it, PM me. I may be interested in a range-limited, speed-limited EV.
          Last edited by specialgreen; 03-26-2019, 12:26 PM.

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          • #6
            Originally posted by specialgreen View Post
            The overall idea is pretty sound..
            EV batteries are extremely expensive and takes a huge amount of energy to manufacture. The cost 3 to 7 times more than Pb batteries are only last a fraction of cycles as Pb. What that means morons and green mafia do not want you to know is your electricity wil cost many times more and make you a very heavy polluter not to mention robbing our stupid kids of resources. You rbest EV batteries on the market only have 500 cycles. A decent Pb battery 2000 cycles at 1/4 the cost and even Pb batteries are stupid to use because despite the fact th eare less expensive and last longer, means you are still paying 5 to 10 times more for electricity than necessary.
            Last edited by solar pete; 03-27-2019, 09:32 PM.
            MSEE, PE

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            • #7
              Originally posted by specialgreen View Post
              If you decide you don't want it, PM me. I may be interested in a range-limited, speed-limited EV.
              How about a GEM for $1500?
              Attached Files
              Those who do, do it!

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              • #8
                Originally posted by motorcyclemikie View Post
                How about a GEM for $1500?
                Most GEMs have lead acid batteries. Used lead acid batteries that have sat around for a while for $1500? No thanks!

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                • #9
                  Originally posted by Sunking View Post

                  You rbest EV batteries on the market only have 500 cycles.
                  I am not quite sure how you get there with cycles...

                  As an example, the battery in a Chevy Volt has 14kWh usable (out of 16kWh pack), and an all EV range of 53 miles, and it comes with a 10 year 100,000 mile warranty for less than 30% degradation.
                  Worst number of cycles would be 100,000 / 53 = 1887 cycles for less than 30% degradation.
                  Many volt owners have reached over 300,000 miles with no noticeable degradation, which means 5660 cycles and still going strong...

                  An LG Resu10H has a 10 year warranty for 40% max degradation which is at least 3650 cycles.

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                  • #10
                    Originally posted by motorcyclemikie View Post
                    How about a GEM for $1500?
                    No, the minimum I would accept to haul it away is if you pay me $2000 to make the problem go away.

                    MSEE, PE

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                    • #11
                      Originally posted by scrambler View Post
                      An LG Resu10H has a 10 year warranty for 40% max degradation which is at least 3650 cycles.
                      You do not even know what a cycle is or how it is measured. If you did, you would not have stuck your foot in your mouth and showed your ignorance. .
                      Last edited by solar pete; 03-27-2019, 09:33 PM.
                      MSEE, PE

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                      • #12
                        Originally posted by Sunking View Post
                        Complete Green Mafia propaganda BS. You do not even know what a cycle is or how it is measured. If you did, you would not have stuck your foot in your mouth and showed your ignorance. .
                        I was merely asking a question on how you arrive at your cycle number.
                        Too bad you are not the kind that likes to educate ignorant people

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                        • #13
                          Originally posted by scrambler View Post

                          I was merely asking a question on how you arrive at your cycle number.
                          Too bad you are not the kind that likes to educate ignorant people
                          I think SK has been around Lead a long time. He knows what he is talking about when it comes to Lead Acid batteries. Less so with Lithium. He has the same attitude on another DIY EV forum and his Lead Acid views are largely ignored there. Most posters are getting more cycles out of Lithium than he wants to admit. Welcome to the Ignoramus Club. I wear it as a badge of honor. Begin Flame War. LOL
                          9 kW solar. Driving EVs since 2012

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                          • #14
                            EV batteries get their many cycles by de-rating the battery capacity and only using the middle portion (30-80% ) of the cell capacity, as I understand it, the deeper the cycles, the less cycles you get.
                            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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                            • #15
                              Indeed, whenever possible, Lithium Ion battery are never fully charged or fully discharge to maximize their life span
                              The volt for example only uses 14kWh out of its 16 kWh pack for that very reason (never fully discharging nor fully charging the pack)
                              So you will never see true full discharge cycle for them.
                              But that is of course irrelevant in terms of evaluating the real use condition lifespan of the battery.

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