During shelter-in-place

I left it on for about 5 minutes. FYI, in my other vehicles, the Kill-A-Watt meter would start out at 0.01A, slowly increasing to 0.20A, 0.30A, then settle around 0.60A to 0.70A, within a minute or so.

I hooked up the Battery Tender to the Prius first, then plugged in the 120VAC.

 

I guess, I'd see it as a rule of thumb, but maybe not a carved in stone law.

I recently got a new clamp on meter and it reads DC current. Maybe this would be an interesting test for it.

 

Hi Jerry,
It looks like you are also a "Double E" like myself Indeed, 0.30A at 120VAC is quite a bit of power. Power calculations are quite complicated, because 0.30A is actually AC. So, inside the Battery Tender, it would need a full-wave rectifier to convert to DC, then some sort of buck converter, running at some PWM duty cycle, to step down to 13VDC-14VDC, while providing max 4A DC.

Along the AC to DC conversion path, there are power loss, power factors, crest factors, switching circuit efficiencies, heat loss, etc. Even the 120VAC input could vary +/-10%. So at best, I could use the Kill-A-Watt meter to track the AC currents slowly increasing, hovering around 0.60A-0.70A while the charging cycle is in full swing, then the current would decrease slowly when the battery is ~80% full. Eventually, it would drop down to ~0.01A when the Battery Tender is "maintaining" the battery

 

Yeah I'd think whatever max amps they recommend, there's a good safety factor.

 

Cool. Lots of folks don't know what they're doing with electricity, so I kept it simple. Plus the full explanation would be really involved and none of us has time or need for it. Yes, I am a EE, but don't get as much practice as I used to.

Anyway, it's awesome that you get that stuff. And I agee that the killawatt is handy for seeing rates of change in the power flow. One of these days, when I have the time and ambition, I might use my old clamp on meter on the charger power cord and the new one on a lead to the battery set to DC and just have them side by side so I can compare. Just for the fun of it. Maybe I'll try that tomorrow.

 

Welcome to PriusChat!
…I'm a bit late coming to the party! (…shouts of "…so what's new?") -
…all the advice re. 12V AuxBattery is spot on, and if you're worried about the TractionBattery, then do a search on "Prolong Grid Charging" HybridAutomotive make a system to condition and recondition the main HybridBattery for various models of the Prius. I see yours is a very pretty silver 2009 Gen 2. Mine is the same year (touring package) and I've been using the Prolong Grid System for the past 5 years. The car has done just over 167,000 miles, is returning 43 MPG overall, and the SoC (state of charge) of the hybrid battery spends most of its time in the 65-75% range (which is higher than when I started using the Prolong System (55-65%) (…just saying' )

 

Well, I tried the DC clamp meter, but was too lazy to verify the DC clamp on meter's readings, so I'll just trust it for now.

My charger apparently has a lot of internal power use, as evidenced by the roaring fan. So the AC and DC amps were closer to each other than I expected.

IIRC, this picture was with the charger set at 2 amps. It was only putting out 0.48 because the battery was already in good shape. Incoming current was 1.11 amps if you can't see it clearly.



This next shot was with the charger set to 6A. It's taking 4.35 amps incoming to put out 3.43 amps DC. It's a little bigger difference than at 2 amps, but at 2 amps the incoming current was almost double the output. At 6 amps, it's only 27% more. Not surprising considering all the losses inside the charger that @jlim888 pointed out.

 

That might not be long enough.
Just a wild guess.

 

Not in THIS case you didn't.

 

"As simple as it can be, but not simpler."

 

I'm envying your current clamp collection... I normally would just put a small 0.01-ohm power resistor in series, use the DMM to measure the voltage drop across, then use Ohm's Law to calculate the current

FYI, the Battery Tender is rated at 4A charging current at ~14VDC, with no cooling fan. Even at 4A*14VDC = ~56 Watts, the enclosure of the Battery Tender barely warm up.

 

Well, I got the new one (with DC ability) because the old one apparently went belly up. It turned on but wouldn't switch functions. I't several years old, so I didn't feel like trying to fix it. The new one didn't cost much more than replacing the old one, and I've always wanted a DC clamp on meter. Plus it came with that handy splitter so you could check the current in a cord without having to split the cable or cobble up an unsheathed extension cord.

Wouldn't ya know, a couple months later, on a whim, I tried the old one which was still laying on the bench and it was working perfectly. Turns out to be a happy mistake because having two can come in very handy now and then.