inverter battery charging. and other questions

solarvic
solarvic Solar Expert Posts: 1,071 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
Is battery health and longevity the same when bieing charged by an inverter instead of a charge controler? Does a smart meter know if you are AC coupled? I plan on using a gti inverter to ac couple with an offgrid magnum inverter and hope the smartmeter can,t tell, :Dsolarvic:D
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #2
    Re: inverter battery charging. and other questions

    AFAIK, there are 3 ways to do AC coupling:
    a) Use an SMA sunny island + sunny boy which gives you a smooth charge the same as a regular charge controller
    b) Use a bidirectional inverter/charger that increases line frequency to knock GTIs offline when the batteries are fully charged (e.g. Xantrex XW, Magnum?, Victron multiplus)
    c) Use any bidirectional inverter and install a dump load across the battery to get rid of the excess power.

    I don't know if the Magnum supports option B, but there is a study saying that option B reduces the life of batteries because of micro-cycling: http://currentgeneration.co.nz/site/current/files/Partial%20AC-coupling%20in%20Minigrids.pdf

    Sooooo, if I were in your shoeI'd investigate option C :)
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  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    #3
    Re: inverter battery charging. and other questions

    Stephendv, I was planing on the option c. As you need the magnum model MS-pae series inverter that has software to use option b. I have the previous magnum model MS- AE series that don,t have the software. I have the understanding that I can use option c as you stated. My main concern is. Will the battery life be the same if I use grid power to charge battery thru magnum inverters battery charger as it would be if I used a charge controler? :Dsilarvic:D Ps I had a lot more info one the first post I typed last night but got disconnected from the forum before I could send it.
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,022 ✭✭✭✭
    #4
    Re: inverter battery charging. and other questions

    Any smart meter is smart enough to know when power is passing through it. You might, as others have found feeding power back to a "non-net meter" smart meter, that you're paying for the privilage (the meter still accumulates kwhrs). Any smart meter I found that has the word "net" on it will show a delivered and recieved number of kwhrs, they don't count up and down depending on which way the power flows.

    I have utility power available too. It's p;riced on time of use, so from 7pm to 7am is off peak and the cheapest rate. When I'm doing a charge from the utility through the inverter I limit the ac amps used to a low level over a long time. For me on my SW 4048 that's 10amps ac. This prevents the internal fans running and waking me up (via the female elbow). It may take all night, but it's a slow charge much like a solar charge.

    Ralph
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  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    #5
    Re: inverter battery charging. and other questions

    Ralph, I kind of have a unique set up. I hava a mobile home pole with the smart meter, 100 amp service panel and breakers in it to feed the grid and another set of breakers that feed into my inside service panel. It has been inspected and online for 2 years now. I have a magnum inside I am passing power thru from the grid. to my inside service panel. I can throw the grid feed breakers inside and the inverter will turn on. Sometimes I shut off the grid so the charger well charge a bulk charge. Otherwise all it ever does is go to float charge. I have an extra frinuis gti 1800 watt inverter I wanted to ac couple with the magnum offgrid inverter. I was thinking there wouldn,t be much power going back thru the smart meter from the ac coupled gti inverter. Probably would use most of the power in the house and to recharge the battery. I am not feeding the full amount of power back to the grid I was approved for. Approved for 4.7 kw feed back to grid. Most I ever saw was about 4kw so have a little leeway. I got thru december 29 with 200 kwh in my account to roll over for January. I want to get more power credit for the summer so I can use my air conditioners a little more. So what I propose to do probably won,t send much more power to grid but I won,t be using as much so my account should grow more. :Dsolarvic:D
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