AGM battery for Gen 4/Gen 5 Prius/Prius Prime and observations on the 12-V charging system

No interestingly seems like this method of Toyota charging of 12V batteries is more than 20 years old.

I have a 2004 Toyota hybrid Alphard which I changed into a campervan over Covid lockdowns. After checking the Prius guess what is the resting voltage of the Alphard- you guessed it 12.2V. Well it got the charger treatment too. I have had 12V issues with the van. It has two AC units and driving very slow in hilly terrain with the AC going in hot weather had the battery voltage fall to 11.7V which trips faults and check lights. The inbuilt charger just cannot keep up with the load, so I have a volt meter in the van to check that.

I did a 500km round trip this weekend with the Prius, so will be interesting to see what the battery voltage is now. Checking the battery voltage will be added as one of the periodic routine checks e.g. oil level, tire pressure, coolant levels, etc. to do.

I must say I find it strange that the battery charging could be an issue. I had my gen3 Japanese 2011 Prius import for 10 years. It had 20 000kms on when I bought it with the OEM battery and I never had any battery problems and sold it at 120 000kms still with the OEM battery. It was the best car I had ever owned, absolutely no issues at all. Sold in a weak moment, but glad that I have another one now.

 

DO you know the voltages the Prius vehicle electrical system was subject to when you turned the "intelligent charger on and it went to the de-sulphating program" ?

 

No as I can't remember but some years ago I checked what it did and from memory it pulsed the battery at 14."something" volts.

14.7V pulsed
something like this
https://www.aliexpress.com/item/1005005389302164.html?spm=a2g0o.productlist.main.13.5f8042detgTbzy&algo_pvid=98e3cea6-29fb-46e9-84c7-2304f38be9d7&algo_exp_id=98e3cea6-29fb-46e9-84c7-2304f38be9d7-6&pdp_npi=4%40dis%21NZD%2125.98%2125.98%21%21%2115.32%2115.32%21%402101c5c317312844782771260efb9d%2112000032853324743%21sea%21NZ%21830455513%21X&curPageLogUid=4G6GrbsZCJ0e&utparam-url=scene%3Asearch%7Cquery_from%3A

 

Good to know that it does not apply a 15v or higher voltage in the mode you used. 15v or higher could cause problems with the cars electrical system and components.

 

Mine is a bit different to that one as it's only a 5 stage charger and only 6A . Mine does do the 15.5 or 15.7V charge (memory a bit hazy on exact what voltage it was) but you have to set it to the repair mode for it to do that. It doesn't go to repair mode automatically.

As you can see in that one's manual it always starts with this desulfation mode which seems like it sends a pulses and then measures the falling battery voltage
?? or pulse current? between the pulses to determine the state of your battery. After that it goes though the other stages. They work really well and have revived drained motorcycle batteries. I have one built in permanently into my Toyota hybrid Alphard running off the vehicle supplied 100AC to charge the house batteries.
I have had good service from these units for a few years now.

 

Yes I was pleasantly surprised that repair revived a motorcycle battery the was below 11V and I got about a year more out of it. I knew I was pushing it tho.

 

My 2020 Prime once again charged fully yesterday, and it wasn’t any 20 hours since the last time. It had been colder. Without the monitor it would be difficult to see the details.
I have yet to see it stop charging though in ready mode when it starts doing this. Of course the rate may be minuscule and it still is charging at 100%. Plus the Toyota battery sensor soc reading may be different.

 

I see about 14.3-14.4 v in ready mode in park. It seems to charge fast sometimes, other times slower. No amp scale to know. The 20 hour thing doesn’t seem to be a thing. SOC was around 80, distance was 3 miles, got home let it finish to 100% for about 12 mins in park appx. But it actually never stops charging, since no ammeter don’t know how low it goes.