False polarity alarm on jump booster?

And you're sure you've got it right?

I strongly recommend NOT to proceed. It could be there's something defective with the charger, whatever the issue: if it's warning, not worth the risk to proceed. Try another charger.

Got a new one myself for Xmas: CTEK MUS 4.3. A bit confusing, but seems a robust unit. Beefier cables than my old 3.3 one.

 

Buy and install a new 12V battery.

 

Maybe. Do you have the manual still. If not you can usually find a pdf version for download.

 

You don't need to actually drive the Prius to charge the 12V battery. What matters is how long the Prius is left READY. From the 12V battery's point of view it doesn't matter whether the Prius is traveling at 80 mph or 0 mph. If you want to make sure the battery is charged, leave the Prius READY for at least 8 hours.

It is certainly possible that the jump pack will refuse to provide power if the recipient battery is below a certain voltage. If you still had the battery around, you could measure the voltage across it.

 

you could've asked the autoshop to charge up the old battery for you and keep it. It's only a small core charge you would need to pay

 

Yes, this was my first though when you said it didn't show any problem on your wife's Prius.

I'm guessing that your battery was pretty far gone and appeared to be somewhat like a short circuit to the jump start unit. That unit advertises having short circuit protection. Do you know if it has a separate warning indicator for short circuit, or is it perhaps shared with the reverse polarity indicator.

If you're feeling brave you could try shorting the output (instead of connecting it to anything) and see if it sets off the same "reverse polarity" warning.