How much driving to fully charge the 12V?

I think you're getting a little dramatic there. You might be overthinking things, just a tad.

Yes, fairly regularly. Where exactly in the RM do you see that it says the DC/DC converter only puts out 14V?

 

Musta been the redesigned tail lamps.

 

14.4 here

 

It seems that for most battery manufacturers, that the "safe" recommended charge rate for AGM is 0.1C. So a 35 Ahr battery would be 3.5 amps, and so on. There are lots of opinions on the web that 0.2C is just fine. Given that the battery in a Gen2 can last for many years with no current limit on charging (is a constant voltage system), I go with a 6A or 10A AGM setting on my smart charger (depending on battery size) and not worry about it.

Posted via the PriusChat mobile app.

 

I was curious what would happen if I charged my Prius battery with the 15 amp charger. Prius has been in storage for the winter and I had a 1.3 amp maintainer on it. Took the maintainer off a week ago, so I decided to try the 15 amp charger, only because it had a digital readout. Took the Solar digital tester and tested the AGM battery, set at 350CCA, tried both AGM settings, tester showed battery could be charged, the CCA showed 500. Still can't figure out how the tester tests AGM. Hooked the 15 amp charger up and took a video for 45 seconds. Now I'm not using the 15 amp at all for the AGM, was just curious what the reading was going to be.

Charger stabilized at approx 5 amps for the 45 seconds, then I disconnected the charger. Normally I'm charging the AGM with the Ctek 7amp and maintaining the AGM with the BatteryMinder, have 4 BatteryMinders, bought 6 years ago when Northern Tool had them on for $20 each. Also have assorted other chargers, my go to is the Ctek. Yuasa actually sells a rebadged Ctek.



I'm quite diligent maintaining my auto batteries, have 5 vehicles, couple farm trucks parked for the winter, batteries stored indoors.



The Toyota battery in the photo belonged to a lady friend, she is taking care of her 102 year old mother during Covid and parked her van for the winter. She went to start it after a month and the battery was dead, boosted it and took it to the local Napa. They told her she needed a new battery so she replaced the battery but told them she wanted the old battery, which kind of ticked them off. She was thinking she might be able to get warranty since it was 4 years old. She ended up letting me have it, brought it home and used my assortment of chargers to resuscitate the battery. Mainly used the Ctek charger. Was able to get it back over 665CCA depending on the tester, the blue one is a cheapy from our version of Harbor Freight. Just did the test, battery has been sitting for a month or so. I give all the batteries a top up charge every 2 months while they are sitting in my basement.

 

14.7 is the most common voltage I ever see in my 2010 when in ready.

13.8 is what I was used to seeing in my Gen 1.

 

I haven't been taking notes on the various Prii I have worked on, but my 2006 DC-DC converter does put out 14.0V +/- 0.05V

Posted via the PriusChat mobile app.

 

I wouldn't read too much into that. The RM says "9 to 14 V" or "10 to 14 V" in many, many places in the "Specified Condition" column.

 

DC-DC converter outputs a nominal 14 volts, but amperage is over 60 amps and we are concerned about 5 amps to charge the AGM? Anyone care to explain why DC-DC converter amps are different to a bench charger amps?

Prius 12 volt charging current | PriusChat

More 12v stuff from Hobbitt

https://techno-fandom.org/~hobbit/cars/prius-12V/

 

Just because a current source is CAPABLE of providing 60 amps under the right conditions, does NOT mean that it will under all or even most conditions.
And what is provided does not all go into the battery. In fact under most conditions, most of it goes into running the car.

 

Odd trying to find a Yuasa AGM automotive battery website for USA only returns powersport motorcycle batteries.

Motorcycle Batteries | Powersports Batteries | Yuasa - Made in the USA

I show a Canadian dealer a couple hours from me, got a quote for the Prius AGM Yuasa $199.50cdn/$160usd?? in store.

Yuasa Battery 1 SASKBATTERY.COM

 

This video explains it, but noted also that it was providing 10 amps to the battery until he turned on all the accessories and then input stabilized at 5 amps.

 

There are also just flat-out limits to the accuracy of Hall current clamps. It looks like he's using a Fluke i410, which is made for measuring currents up to 400 A DC. (An i1010 also looks like that, but would be even more overkill for this use.)

I have an older Fluke model similar to the i410 and I just avoid using it to measure currents that won't be at least a handful of amps. Using it to measure fractions of an amp is like tightening little inch-pound screws with your 1/2" drive torque wrench.



You can see how any reading in the neighborhood of 0.8 A barely emerges from the error bars. Even asking a question about what it means when readings of two different i410s differ by 0.8 amps is kind of begging for the answer "Cottleston, Cottleston, Cottleston pie".

 

Sitting for five days, OFF the charger...

 

18AH? One of your Prius batteries? Isn't a Prius AGM 45AH?

 

What is the model number of that DMM? Shall we check its specified accuracy?

It may also be useful to get the brand and model number of the battery, to check its specs for anything special about its chemistry.

 

Starting at post #28, the debate begins concerning the actual resting voltage of an AGM battery, after a full charge.

The 18ah battery is NOT used in the Prius. Rather, it is the newest AGM battery I have at home, which should have the highest resting voltage.

Two meters are now attached for a voltage reading. (See pic.) Meter accuracy is unknown.

 

A classic case of "surface charge", I think.
Put a small load on it for a few minutes.......like a single 12 V light bulb.......and then read it again.

Also this: