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Thread: Converting an UPS to solar power system

  1. #1
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    Question Converting an UPS to solar power system

    Hi

    I have got me an old UPS PowerWare 9305 15KW and that is an 3 phase in and out with an internal battery pack there is 288Vdc

    my idea is to add some extra batterys to it and then by using diodes for the extra pack it will be the UPS is changing the internal "small" battery pack and then solar panels are changing the external batterys, then there will be an extra control board there is disconnecting the AC input(via relays) when the battery pack is fully changed and when the battery gets down to some thing like 30% left then it connect the input line again.

    I have the UPS with battery and all the AC stuff like relays, bypass panels, fusebox and so on.


    so how can i smartest connect some solar panels to batterys with 288V ?

    can i put MPPT controlles in series with diodes between them to get 288V ?

    What do you guys think ?



    What i dont have now is the solar panals and extra batterys.



    Thanks
    Thomas

  2. #2
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    Quote Originally Posted by Tooms View Post
    Hi

    I have got me an old UPS PowerWare 9305 15KW and that is an 3 phase in and out with an internal battery pack there is 288Vdc

    my idea is to add some extra batterys to it and then by using diodes for the extra pack it will be the UPS is changing the internal "small" battery pack and then solar panels are changing the external batterys, then there will be an extra control board there is disconnecting the AC input(via relays) when the battery pack is fully changed and when the battery gets down to some thing like 30% left then it connect the input line again.

    I have the UPS with battery and all the AC stuff like relays, bypass panels, fusebox and so on.


    so how can i smartest connect some solar panels to batterys with 288V ?

    can i put MPPT controlles in series with diodes between them to get 288V ?

    What do you guys think ?



    What i dont have now is the solar panals and extra batterys.



    Thanks
    Thomas
    Wow! This is one of those times when you have such neat stuff that it seems that there has to be a way to use it. But it may not make sense anyway. A few questions and comments to start:

    1. What is the capacity (watt hours) of the internal battery pack of the UPS? Or alternatively how long can it deliver its full rated load before running out of battery? What type of batteries are they and are they in good condition right now?
    2. Are you envisioning a total off-grid solution or just an extended backup for utility power failure?
    3. You cannot stack mppt controllers, and trying to find a controller which can charge a 288v battery stack and treat it properly is going to be very hard. Your best bet (although inefficient) would be to make use of the built-in charger circuitry in the UPS by providing it with AC from an inverter connected to your external battery pack. Can the UPS be used with only a single phase AC input?
    4. A depth of discharge (DOD) of 70% will kill just about any type of battery very quickly. A UPS is designed to go that low on the battery pack a very limited number of times, not on a daily cycle basis.
    5. Delivering 15Kw to a load for any great length of time will take a ginormous battery array. The inverter in the UPS may not be particularly efficient when delivering less power, so it may not make sense if you will not really be handling that large a load.
    6. Can the battery charging circuitry inside the UPS be made to operate from a DC source? Using a DC-to-DC converter from a lower voltage external battery array may be the best way (if any) to go.
    7. 288 volts DC is extremely dangerous to work with. Are you skilled in high power electronics, do you have arc-flash protective gear to wear, and is your life insurance paid up?

    I am sure that others on the forum will add a lot more questions and may just advise you to forget it.

  3. #3
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    Thomas I am familiar with this UPS. The show stopper is the 288 volt battery. There is no Charge Controller that I know of that can charge a 288 VDC battery. Currently 96 volts is about the limit. It would be a custom build and that means very expensive. Unfortunately you cannot cascade Charge Controllers to build up the voltage to where you need to go.

    I can think of a work around but very expensive and very inefficient. I will keep thinking but I have nothing at the moment.
    MSEE, PE

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    Quote Originally Posted by inetdog View Post
    Wow! This is one of those times when you have such neat stuff that it seems that there has to be a way to use it. But it may not make sense anyway. A few questions and comments to start:
    yes that is what i am thinking and it size will easily fit the complet home.

    1. What is the capacity (watt hours) of the internal battery pack of the UPS? Or alternatively how long can it deliver its full rated load before running out of battery? What type of batteries are they and are they in good condition right now?
    The UPS is rate as 15KVA and around 10-11KW, from the datasheets it is saying that it can run 10min at 100% load.
    it is an older UPS but the batterys seems to be good.

    It is for my parents house and the gear is there, so i can first do an fully check up on it in the weekend.

    i have an good PSU so i can chage the batterys and then i have an BK precision DC load there is having an battery test function so i am planning to test and verify the batterys.

    2. Are you envisioning a total off-grid solution or just an extended backup for utility power failure?
    the first idea is the UPS is having grid input and output to the house.

    and battery pack change up via solar, so when there is power on the batterys then it will disconnect the grid input

    3. You cannot stack mppt controllers, and trying to find a controller which can charge a 288v battery stack and treat it properly is going to be very hard. Your best bet (although inefficient) would be to make use of the built-in charger circuitry in the UPS by providing it with AC from an inverter connected to your external battery pack. Can the UPS be used with only a single phase AC input?
    i dont think it can run on one phase, it is designed for 3 phase system.

    4. A depth of discharge (DOD) of 70% will kill just about any type of battery very quickly. A UPS is designed to go that low on the battery pack a very limited number of times, not on a daily cycle basis.
    the internal battery pack in the ups can be used until it dies but the external pack must be some there works good with solar

    5. Delivering 15Kw to a load for any great length of time will take a ginormous battery array. The inverter in the UPS may not be particularly efficient when delivering less power, so it may not make sense if you will not really be handling that large a load.
    i know the UPS it not an very good option for an solar setup, but i got it for free i like to try use it.

    6. Can the battery charging circuitry inside the UPS be made to operate from a DC source? Using a DC-to-DC converter from a lower voltage external battery array may be the best way (if any) to go.
    I dont know, have to look into this but i am hoping to do this setup by not modifying the UPS in any way other then connection an external battery pack(and changer via solar)

    7. 288 volts DC is extremely dangerous to work with. Are you skilled in high power electronics, do you have arc-flash protective gear to wear, and is your life insurance paid up?
    yes i am an eletrician and i know when to back off the project if the design/setup gets dangerous or/and gets unsafe.

    i will also add also of extra safety functions like fuses every where and grounding.


    I am sure that others on the forum will add a lot more questions and may just advise you to forget it.
    I am hoping so and the reason why i am asking here even that i am an eletrican is to be safe and to be sure that i do this by an safe path.



    Thanks for replying and i will in the weekend do some testing of the gear and verify it, also take some photos so your guys can see how it looks like.


    Thomas

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    Quote Originally Posted by Tooms View Post
    yes that is what i am thinking and it size will easily fit the complete home.
    The first idea is the UPS is having grid input and output to the house.
    and battery pack change up via solar, so when there is power on the batteries then it will disconnect the grid input

    If you have grid power, then anything you do to try to use solar power directly to go off-grid will be far too expensive to make economic sense even when you have the UPS free to start with. The biggest costs will be in the batteries and the solar panels.

    If the grid power is unreliable and you have some reason not to go with a backup generator, a hybrid system might be justified. But to save money for you parents, the way to go is to grid-tie your solar panels and go without batteries. If you do that, the only use you will have for your UPS will be to provide short term backup as it was originally designed to do.
    The difference in cost between a grid-tie inverter and a hybrid inverter will not make up for the hassle of integrating the UPS into the design of the system. (My opinion only....)

  6. #6
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    The batteries that come with it are not deep cycle batteries. They are made to be discharged in excess of 4C and only have maybe 50 cycles in them if that much. The batteries are not made for cycling, just emergency standby to be used only a few times in their 5 year life cycle. They are hybrid AGM batteries made to be charged up in as short as 1-hour and be fully discharged in 15 minutes.
    MSEE, PE

  7. #7
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    Very interesting challenge.

    What quickly comes to mind, (as I've seen it before) is a moderate PV array and a 3 phase grid tie inverter, and the UPS at that point becomes an 'AC Coupled Battery Backup'.

    But there is no way to charge the batteries from the PV in the event of a downed grid.

    Where you are hung is your requirement of -what's going to end up being- a custom mppt charge controller. A completely unique system which is going to be pretty tricky to get through code inspection.

    All in all, a cool, but pretty much untenable idea. Not cheap either.

    Nice find on the UPS though.

  8. #8
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    Quote Originally Posted by Tooms View Post
    can i put MPPT controlles in series with diodes between them to get 288V ?
    Yes but they would be custom, which means expensive. There's no problem technically though, MPPT's work at any voltages they are designed for.

  9. #9
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    Quote Originally Posted by Sunking View Post
    Thomas I am familiar with this UPS. The show stopper is the 288 volt battery. There is no Charge Controller that I know of that can charge a 288 VDC battery. Currently 96 volts is about the limit. It would be a custom build and that means very expensive. Unfortunately you cannot cascade Charge Controllers to build up the voltage to where you need to go.

    I can think of a work around but very expensive and very inefficient. I will keep thinking but I have nothing at the moment.
    yes it is high 288v and it will not be easy or cheap to get some thing to working with that.

  10. #10
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    Quote Originally Posted by inetdog View Post
    If you have grid power, then anything you do to try to use solar power directly to go off-grid will be far too expensive to make economic sense even when you have the UPS free to start with. The biggest costs will be in the batteries and the solar panels.

    If the grid power is unreliable and you have some reason not to go with a backup generator, a hybrid system might be justified. But to save money for you parents, the way to go is to grid-tie your solar panels and go without batteries. If you do that, the only use you will have for your UPS will be to provide short term backup as it was originally designed to do.
    The difference in cost between a grid-tie inverter and a hybrid inverter will not make up for the hassle of integrating the UPS into the design of the system. (My opinion only....)
    The thing is that my parents house is two houses, one have the private house and the other one is business, the main fuse panel is in the business and then there going an long cabel over to the private house so it will be very easy to split them and then run the full privat house from this ups setup.

    why do this ups thing...
    In Denmark there is an limit on 6kw solar systems there grid-tie and my father is planing to have an 6kw solar grid-tie installed on the bussiness house, so in order to do more then it has to be off grid and here is where the ups is coming in because the ups+solar+battery setup will not feed any power back to the grid.

    The other resaon is that i just like to try an use all this free gear that i now got and i think it will be an shame if it is not used in any way.

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