Help Please.

System
System Posts: 2,511 admin
in General Solar Power Topics #1
Hello everyone. I'm new here but have been reading for a while. My question is I use Tripp*Lite APS PowerVerter Inverters for backup power at work and was wondering if I could use them at home for off line power sorce utilizing battery and solar PV. They are 3600 watt, 36volts input, 120 volts output. They have battery charging capabilities. I know they are "Load Switching" but at $900.00 for new ones I think I am getting a good price. Does the 36volts DC input make much difference? Also the say they are rated at 4800 watts for (1) hour and 7200 watts for 10 sec. surge. Could this be true? I also use 15watt solar panels that I purchased from Northern Tool for $63.00 per panel, are they any good and does anyone know who makes them. I measured the voltage and get 17 volts dc but have not checked the wattage. I only use them for some small lights but they seem to work fine.
Any feedback would be appreciated.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Help Please.

    Should work OK... You might want to check the efficiencies of the UPS. With solar power, conservation is a major goal of any installation.

    Regarding output... 3,000 watts is probably real. The 4,800 Watts may instead be 4,800 Volt*Amps which is not power but how inductive (or capacitive or non-linear loads like computer power supplies) loads are rated (need to size the wiring to handle the current from non-linear loads). A resistive load would have watts=V*A...

    Buying solar panels... Small 15 watt panels are only cost effective for installations where you only need 15 watt panels... In general, for larger systems (multi-hundred watt and larger), you are better off buying large panels so that you minimize wiring messes.

    Also, you need to check if the panels are amorphous silicon or mono/multi-crystalline silicon panels. In general, a m/m-crystalline solar panel will last 20-25+ years with a 20% guaranteed power loss due to aging. In general, amorphous silicon panels can lose 30% of their power in six months of sun--just the nature of Amorphous silicon...

    $4-$5 per watt for large panels (plus shipping and tax) seems to be the rough price... Small m/m-silicon panels typically cost a lot more.

    Back to your setup--you have to define how fast/how much power you want from your silicon panels. A 15 watt panel (plus, possibly a small charge controller--depending on the size of your battery bank) would be OK for float charging (maintaining charge) but will not recharge your battery after it has been used.

    To recharge your battery, the solar panels should probably be rated around 3%-10% (or a bit more) of your bank capacity. You should be able to recharge the bank after 3 days.

    Your UPS has an internal battery charger--do you want your lines to recharge the battery or the Solar Panels?

    Do you want to use the UPS as a UPS (AC in, AC out, auto switch over on AC failure) or do you want to use the UPS only in a power failure situation--many UPS's require manual intervention (button press) to start when AC power has failed.

    Also, the larger UPS come in different "flavors"... One type has a standby inverter (AC power simply sent to the load) which switches in ~8 milliseconds on power fail--and another continuous conversion type where the battery is always under "charge" and the DC is converted to AC to run the load.

    36 VDC is fine for a battery bank--you would have to add up the solar panels to equal 36 VDC (about 45 volts for float charging). 36 VDC seems to be a bit of an odd voltage for solar chargers--but there are units out there.

    In the end, UPS are generally pretty power hungry devices (both in standby and during conversion). If you are trying to either save energy and/or run on solar power, you might be better off getting dedicated solar/hi-efficiency conversion devices (from Outback, Xantrex, etc.). In the end you will save on solar panels and batteries (size, costs, thermal control of batteries, etc.).

    As a starting point for experimentation and learning about the components/issues... Go for it.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
    Re: Help Please.

    be aware that those backups are only tempory backups and not meant to run things continuously and may still only be a modsine inverter that one could buy cheaper seperately. i did get some backups for myself, but they generally will only be good for tempory relief of power loss. some cannot have that annoying beeping dissabled easily and the batteries are limited in their capability and won't last long under many stresses by calling upon them to perform high power applications far into their depth of discharge. research it more before buying the ups to be sure it will do as you wish it to do at a cost in line with what you may be able to get otherwise in piecing components together. my ups is a tripp-lite interoffice 500(got 3 of them at $25 each with new batteries) and it is a modsine rated at 280w for 5 minutes. that kills the battery doing that just so you know. it goes 17 minutes with 140w, but that still kills the battery. if you go full bore at 280w it is advisable with the internal battery to only go a minute or so. i don't remember the exact ah of my battery, but ideally it would be in the 1amp range for up to 10hrs with it only going 5hrs to keep battery lifespan. higher discharges should be figured accordingly to keep battery life. some ups can take larger batteries or banks of batteries and some can't. few are sinewave inverters with most being modsine so if that's a modsine with a small battery pack that can't be expanded upon and keeps that annoying beep going, you might want to piece it together from other components. and yes bargains are out there, but it doesn't sound like that one is a bargain to me imho.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: Help Please.

    I should add also--Some (all???) wind turbines require higher wind speeds to begin generating useful power when connected to higher voltage battery packs (difference between 12 volt and higher 24-48 vdc voltage packs).

    So, if you are serious into investing real cash into your new system (I mean this in the sense that nobody wants to waste money), check the power curves and make sure that the turbine unit you are thinking about will power a higher voltage battery bank in low wind conditions (or whatever your particular conditions are).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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