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Please suggest me UPS
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Please suggest me UPS

Hey guys, I have home router + two raspberry, all consumes 17W. I would like to run this setup for up to 24 hours in case of electricity outage. How many VA I need?

Comments

  • pikepike Veteran
    edited April 2021

    VA = Watts
    You wanna run 17W for 24h you need 408 Wh or 408000 mWh or 0,408 kWh.

    Thanked by 1dodheimsgard
  • VA is a measure of power, not capacity

    Thanked by 1dodheimsgard
  • deankdeank Member, Troll

    Do note that lead acid battery used in traditional UPS have less than what it advertises.

    If Pike Trickfoot is correct in that you need 408Wh, you will probably want 800Wh UPS.

    Or you can go with power stations (AKA solar generators).

    Thanked by 1dodheimsgard
  • @tetech said:
    VA is a measure of power, not capacity

    Yes multiply it with power factor and you will definitely get wattage

    Thanked by 1dodheimsgard
  • @tetech said:
    VA is a measure of power, not capacity

    Yes multiply it with power factor and you will definitely get wattage

    Thanked by 1dodheimsgard
  • @noaman said:

    @tetech said:
    VA is a measure of power, not capacity

    Yes multiply it with power factor and you will definitely get wattage

    Indeed, but the point is that what OP needs to look for is battery capacity, not the power (whether apparent or real).

    Thanked by 1dodheimsgard
  • @deank said:
    Do note that lead acid battery used in traditional UPS have less than what it advertises.

    If Pike Trickfoot is correct in that you need 408Wh, you will probably want 800Wh UPS.

    Or you can go with power stations (AKA solar generators).

    This post from deank is useful and therefore should be flagged.

  • skorupionskorupion Member, Host Rep
    edited April 2021

    APC Smart-UPS SRT 1000 VA, 230 V should last you about 26 hours
    (calculated with https://www.apc.com/shop/us/en/tools/ups_selector/home/load)

    Thanked by 1dodheimsgard
  • dodheimsgarddodheimsgard Member
    edited April 2021

    Thanks guys ;)
    Since watts = Amps x Volts... power supply with 40AH battery (12V) shoud produce 480 wats, considering 50% efficiency it should last for 12 hours if power draw would be 20W?
    Please correct me if Im wrong

  • deankdeank Member, Troll
    edited April 2021

    For UPS true capacity, you need to check what batteries it uses.

    And then you actually need to substract 15% off it due to power loss from DC to AC. Lithium solution will probably be better.

    Thanked by 1dodheimsgard
  • TomBGTomBG Member

    @skorupion said:
    APC Smart-UPS SRT 1000 VA, 230 V should last you about 26 hours
    (calculated with https://www.apc.com/shop/us/en/tools/ups_selector/home/load)

    Nope. There is no standard UPS that will survive more than 2 hours even with zero load.
    Best choice - charge a large lead-acid battery with float charger. Use dc-dc step-down to make it 5V.

    Thanked by 1dodheimsgard
  • deankdeank Member, Troll
    edited April 2021

    @dodheimsgard said:
    Thanks guys ;)
    Since watts = Amps x Volts... power supply with 40AH battery (12V) shoud produce 480 wats, considering 50% efficiency it should last for 12 hours if power draw would be 20W?
    Please correct me if Im wrong

    Provided that it will be DC to DC, roughly yeah. Lead acid batteries sometimes just fail when going under 50% of its charge though.

    If it's DC to AC to DC, then do -15% on that. So, 480 Wh reduced to 400Wh - ish. Your actual stable power will be only 200Wh-ish.

    Thanked by 1dodheimsgard
  • @TomBG said:

    @skorupion said:
    APC Smart-UPS SRT 1000 VA, 230 V should last you about 26 hours
    (calculated with https://www.apc.com/shop/us/en/tools/ups_selector/home/load)

    Nope. There is no standard UPS that will survive more than 2 hours even with zero load.

    What are you even talking about?

    And yes, there are standard UPS' that would run 24h on 17W load. Standard being UPS' for offices and datacenters, not off the shelf Staples $100 special.

  • CristianDCristianD Member, Host Rep

    1000w - 100$

  • WilliamWilliam Member
    edited April 2021

    @deank said: Do note that lead acid battery used in traditional UPS have less than what it advertises.

    Not always true. This is only for OPEN lead batteries. Closed and gel (AGM) are near label capacity.

    My solar system uses open lead acid and i get around 85AH per 100AH battery in summer, and 80AH in winter.

    Also note that Li (any, LiPo, LiIon, LiFePo4) batteries are loosing 50% in extreme cold weather - WAY worse than lead acid.

    Open lead acid is also not legal indoors - charging them produces highly explosive hydrogen gas. No UPS uses open lead acid.

    @TomBG said: Nope. There is no standard UPS that will survive more than 2 hours even with zero load.

    Please what? I run a MPP Solar 5048G 5000W inverter with 16 100AH batteries (400AH @ 48V) - This runs my entire place including AC for a day, without AC 2-3days.

    A cheap APC USV will easily run 17W for days.

    @deank said: Lead acid batteries sometimes just fail when going under 50% of its charge though.

    Absolutely not true. You discharge them to exactly 12.5V and there will be zero problems. Low discharge is normal with lead acid and has to be calculated in.
    They also do not 'fail', they just drop to low voltage and ARE ALWAYS RECOVERABLE.

    I had batteriers stored outside in Croatia, a year, at 14.6V - Came back, 12.1V, trickle charge to 14.8V and it's still the same 85AH with some new distilled water.

  • @dodheimsgard said:
    I would like to run this setup for up to 24 hours in case of electricity outage.

    Where are you located? 24 hours of power outage :o :o :o

  • @ankursharma8715 said:

    @dodheimsgard said:
    I would like to run this setup for up to 24 hours in case of electricity outage.

    Where are you located? 24 hours of power outage :o :o :o

    Poland, more than few hours outage are rare but better safe than sorry ;)

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