Prius V at 190K

Your best bet is to consider the cost of a new battery with a rebuilt engine sometime in its future. Otherwise it might be time to trade.

 

no point to fiddling with a battery that isn't broke. have you cleaned the egr circuit?

 

I would allocate $4k for a quality rebuilt engine installed by an independent shop, maybe $7k at a dealer. Depends on your area and knowledge of good hybrid shops and engine suppliers.

Refurb batteries are worthless unless you don't mind yearly issues that put you in the shop for days each time. Used battery cells are worn out and all the charging and discharging refurb strategies do is to simply allow the supplier to weed out the worst modules if you are lucky. New cells can get you another 150k miles from a battery standpoint. Obviously don't mess with your battery unless it code blues on you or can't make it through a stoplight without the engine restarting and pinging as you drive away with little battery hp.

You could buy a new vehicle instead, order now for Christmas and have your 40k-50k loan preapproved.

 

Safe bet you have a blown head gasket.

 

dropping coolant isn't good

 

Slow failure of the head gasket.

 

Could be coolant leaking past head gasket, into cylinder. That's a 3rd gen "tradition", typically starts between 150K and 200K miles. Usually at the adjoining wall between cylinder's one and two.

Regarding the EGR passages in the intake manifold, they tend to clog up with carbon in sequence, with the passage at cylinder one completely clogging first, and so on. The rest of the EGR circuit is a single passage, and it's very prone to clogging as well. By 200K it's pretty much guaranteed to be near-completely occluded with carbon.

There's a theory this changes the combustion chamber environment, the shape of the heat pulse with each combustion, and this leads to head gasket failure. Corroborating evidence is that carbon clogging of the EGR and head gasket failure go hand-in-hand.

I would assess the head gasket integrity first (leak-down test and/or boroscope inspection of the combustion chambers, with engine coolant pressurized). Once that's resolved, either through head gasket replacement or engine replacement, get on the EGR cleaning. More info in first two links in my signature.

 

The car won't use coolant unless it is leaking, which is obvious or if it's burning it in the cylinder.

 

there can be an extremely low drop that is harmless. for instance, my 10 year old car has dropped a bit, but is still above min.
if you need to add coolant, that might indicate a problem. it could be the head gasket, or something as simple as a hose clamp

 

With our 2010, purchased new, in the first few years of ownership both engine and inverter coolant reservoirs gradually dropped from top to bottom line. I topped them up at that point, and the levels have stayed stable since. I changed fluid on both at 10 years, continues to be stable now, a bit over 12 years. Only 96k kms though.