The runtime rating @ 900W is only 2.3 minutes. Resistance of 12AWG is
~1.6 ohms/1000ft. Be generous and say there's 1ft of lead, so 0.0016 ohms.
P=I^2 * R
Use 60 amps to get your full 1500VA, that works out to 5.76 watts for
2.3 minutes. Not enough heat for long enough.
I'd expect the internal resistance of the batteries themselves to be far
higher, so yeah, they'll get toasty during those couple of minutes, but
not enough to worry about fires.
René
On 12/19/2025 4:00 PM, Anthony Carrico wrote:
The Tripplite 1500LCDT has a 1500VA (900W) output rating. It is 120V @
12A. I guess they round 1440 up to 1500, which seems like bad math,
but anyway...
Inside there are two 12V SLA batteries. I've replaced these things in
the past, but today I was looking at the wire, and noticed that it is
12AWG.
As far as I know, 12AWG wire is good for 20-30Amp depending on
temperature, and two 12v batteries in series is 24V.
24V*20A is 480VA.
24V*30A is 720VA.
480 to 720 minus inverter losses are much less than 1500, so what gives?
Is the 12AWG wire OK because its length is short? Or do I not
understand the UPS's power rating?
