Peri Hartman via EV wrote:
For some time, I've been meaning to get a small UPS to power my router,
laptop, and other electronics in case of an emergency... My thought is
to buy a 12v deep cycle battery and hook up a charger, an inverter, and
contactor to switch from wall to battery. I'm pretty sure there are
products which do all that but I haven't found any yet.
Does anyone have a suggestion ?
New consumer-grade UPS seem to have degenerated like home audio systems
-- they often quote imaginary ratings that can't possibly be correct.
But there are industrial/commercial UPS that have a big enough battery
and enough cooling to actually deliver significant amounts of power for
an extended period of time. You can often find them used ("needs
batteries") for good prices, because they are bigger, heavier, and
uglier. Hide it under your desk. :-)
Another route is to upgrade the battery in a smaller UPS. I've done this
in two older APC "BACK-UPS 450" and one SL Waber "UPS250". These are
older bigger heavier metal-cased units; not the modern cheapie plastic
boxes. The original 12v AGM was something like 5-10ah. I connected them
to external Hawker 12v 60ah AGMs instead.
The second problem is that the inverter will overheat if operated for
more than 5-10 minutes at rated load. This was easily solved by adding a
fan. Then they run for as long as the battery holds out. :-)
These are old enough to actually have a trimpot to adjust the float
voltage. They were initially set for 13.8v to recharge faster; but this
dries out the AGMs so you have to replace them every few years. I turned
them down to 13.5v, which takes over a day to recharge; but the same
batteries are still going strong after 6-10 years.
Lee Hart
--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exupery
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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