AC charging losses

[GAmountain]

I was looking at Titan specs and though people are impressed with AC charging capacity, it seems that it takes 2400w of AC (20a/120V) to provide a max charging wattage of 600w to the batteries. That's a 75% loss?? I'm new to this, but that sounds huge. Why so much loss? Am I missing something in the AC to DC conversion?

 

[gnubie]

Please cite your information or are you just relying on the max ratings on the spec plate? That's the peak draw if so rather than the continual draw. If you have a watt meter (kill-a-watt style) plug the unit into that and see what power it really is drawing while charging.

 

[GAmountain]

I'm just reading the specs. "Fast Ac charging 600 watts standard" which uses the 20a AC charger that comes with the unit. Faster charging with the 25a unit. See: https://www.pointzeroenergy.com/product/titan-solar-generator/. and other references from PointZero. Perhaps I've caught my error. When it says "20a," that might mean charging at 20a DC, not pulling 20aAC from the wall? Does that make sense? Except that 20a x 24VDC = 480w. The standard charger is 20a; you can buy one at 25a (which would = 600w).

 

[gnubie]

Yes, it looks like you have picked up on the DC charge current rather than the AC input. In the standard bundle is one 20A charger, with options being an additional 20A charger / 25A charger / 2 25A chargers.

 

[GAmountain]

That same page also reads:
AC charging: Up to 1450 watts with two 25A chargers (must have two batteries to use two chargers). But 2x25x24=1200, not 1450, so I'm still not clear on how much 120V AC amps will be drawn from the AC chargers. If it is 20a (or 25a) AC, that would be a huge loss to produce 600w. But if that is the output of the AC charger device to the battery, then the math still doesn't seem to match their specs.

 

[gnubie]

24V is the nominal voltage. If you take the full range of voltages the battery can be at and divide that into 600W you'll get a better idea of things.

600 / 20A = ~30V, max voltage under charge is 29.2 so at the top of charge about 20A. I can't say if that is exactly how they have calculated things as there will be losses but not necessarily huge losses.

 

[GAmountain]

That makes lots of sense. The same math applies for two 25a chargers: 25 x 29.2 x 2 =1460, close enough to the specs's "1450 with two 25A chargers)."
Thanks very much for your help! I figured something was wrong in my assumptions.
This may sound crazy, but last resort if solar has failed off-grid: then a small gas generator could re-charge the battery. If it is only 1450 watts max with two 25a AC chargers, this could be done easily with a very small gas generator.