How long can a battery pack sit?

Just pulled the front cover off it just takes a second and put your meter on it It's going to be around 200 volts I bet depends I didn't even look to see where you're located but if it hasn't seriously frozen should be in good shape and it's already out so there's no reason you can't put a trickle charge on it 300 volts at about 2.4 amps it'll charge right up to about 240 50 60 volt somewhere in there and then it'll stop changing on the meter and you just disconnect the charger Don't let it heat up

 

The new battery is better than the old one.
The battery will be charged from the hybrid system. There is no need to make unnecessary movements.
You can take readings with the program and post the photo in Priuschat

 

First is it brand new from Toyota or “new” reconditioned from one of a dozen companies including Dorman at the local auto supply? If not new oem, it’s used with some modules swapped out. Even if it has a shiney Dorman paint job. Worse yet if it’s a lithium or cylindrical NiMH aftermarket replacement.

If it is new oem or used and has discharged itself, which that is likely, it won’t start the engine. Without the engine you can’t force charge it.

Tom is anticipating that scenario and suggests advanced battery teardown and charging with a special charger you buy. Even then some modules may be bad requiring a total disassembly and individual module replacement which are only available used. Overall a risk. If you paid $500 it might be worth the risk.

 

this is assuming the battery is not discharged, if it's discharged it won't start the engine and if the engine is not starting it will not charge the battery. So better take the measurements first and charge if it's below 200v.
There's a high probability that at 18months it will be discharged or low.

 

Well I managed to get my last two for free and by looking at the cases of the batteries they had QR codes on them and I don't think the generation twos at least the early ones shipped with QR codes on the battery stickers replacements a few years later all did and then of course running the numbers off the battery and so on and looking under the hood The last two I got look like somebody had bought them 6 weeks prior to me seeing the car at the tow lot and they're in two different cars running strong like brand new ones or like very new batteries I didn't do anything to them I pulled them out of the car put my test meter on them and saw 196 on one of them and the other one a few weeks later was I don't know I think right at 200 or 202 granted the car is probably hadn't been sitting six weeks but they wouldn't start no 12 volts or something so I grabbed them both and they turned out to be in nicer condition under their covers then the two I was running clean bus bars everything in place etc so I used them. I do have the Venice hybrid charger and discharger funny story about that is I've used it like once maybe twice and then it's just sat here on the floor so maybe in the next year or two I might have a reason to use it I don't know usually if you just drive the car or start it put it in gear and step on the gas and let it run up till it's green and turn it off. If you're not going to drive these cars why bother with them Just get a Yaris and then you can leave that thing sitting for 6 months at a time while you fly all over the world and when you come home pretty much be guaranteed you're going to the store.

 

I've worked on battery packs that have sat for 1/2 dozen years and were self discharged down to zero volts... Even the ones with negative voltage can be restored, but they fail soon after. The ones with a little positive voltage do great after reconditioning though.