Prius 12V battery charging at 14.9V/10A???

See my post above. 12.6 V @ open circuit and/or a 0.4 V drop @ 10 A correspond to a lead–acid battery at about a 50% SOC. The OP needs to recharge the battery and refrain from keeping the ignition switch in the accessory mode or in the off mode with the lights on.

The Prius Prime 12 V battery can easily be recharged from the traction (hybrid system) battery when idling in the EV mode with the ignition switch in the on mode and READY displayed on the MFD. Make sure that the SOC on the traction battery is high when you start so that it isn't drained and the ICE doesn't kick in during the process.

 

No it doesn't.
Those SOC tables give voltages under NO LOAD.
How much the voltage drops with a healthy load depends on the total capacity of the battery.
Small battery, bigger drop.

 

Yes, it does.

I have two plots, one for open circuit, one with current. The OP is measuring both, and each result is corresponding to an SOC of 40–50%, independently.

 

Procrastination is a terrible thing. I waited. Had an appointment yesterday to get the 12v battery replaced, can't start. I've had it hooked up to the jump battery now for three hours. Interior lights go on, but dim. Go to start, the dashboard is all lit up, but no start. I'm wondering if I leave it on all day, or give up and get a to.........Well it started.

Have to get me a charger next. Dealer was waiting for me with a new battery. Installed and out the door in 40 minutes. $325 done deal.

 

How is your battery today, 1 year later. Is it still at 12.5-12.6V max voltage?
[QUOTE="TWrecks99"[/QUOTE]
Your battery similar to my 6y old AGM 35Ah, 12.5V fully charged and drop to about 12.2V with Dom lights On, 11.9V with IGN On. It holds the charge find for 2 or 3 weeks parking.

I think the lifespan of 12V battery has large variants. In average 4-6 years, sometimes longer when it is regularly driven and much shorter if it is ever depleted below 11.8V. Basically, unrecoverable damage is done when it is below 11.8V from sulphation. There is no way to recover the capacity lost from undercharging. Overcharging will cause hydrolysis and damage the battery too. A good charger like NOCO5 has cutoff about 14.6V for AGM, similar to CTEK5, Aldi 15.1V, and cheaper trickle charger often keep charging without any control when it will stop. Cheap Chinese unknown brand in Amazon are the worst, some of them overcharged and cause bulging because inaccuracies in Voltage cutoff.

 

A single CTEK maintains our entire fleet, via installed LED charge state telltale connectors.

 

rub it for a week and then check its resting and recovery voltages

 

My 12V seems to be factory original (2012). And according to the MFD, it's always running at 14.9V. I drive it daily. So the battery should be charged, I would think. It still starts the car.

Should I be looking for a replacement, despite it still presently working? (I do have a NOCO GB40 jump pack)

 

Yes you should get a new battery. All you need is around 11 vdc to Ready the car but you are likely close to a no start even after going to the grocery store. When it gets that bad a jump box may not be enough because the box has to first bring your battery up some. In fact the owners manual recommends a five minute wait under jump power for these situations.

Right now its not accepting much of a charge which causes the charge voltage to stay high. Most likely it has a higher than necessary charge current which will cost you mpg as well. The charge voltage should drop into the 13s pretty quick.

 

with a jump pack, i'd run it til it dies. who knows how long it might last?

 

It may still be ok--or may not. What's the resting voltage of the battery when everything has been off for an hour or so?
The charge voltage should drop into the 13s, within a few miles on a warm day.

 

Not sure about other gens, but second gen will charge 60-70 amps on a low voltage battery and amps will drop to milliamps as voltage goes up. It's not dumb!