Any advantage to recharging 12V battery?

It runs the DC to DC converter 100% of the time.

Tom

 

No benefit at all, leave the Aux battery along.

 

That depends on your driving habits. The charging system is a "constant voltage" system (yes it is on 100% whenever you are in "Ready" mode) which is a safe way to prevent over charging the 12v battery, but is sloooow. If you drive for long periods, this system maintains the 12v battery well (lead acid batteries should always be maintained fully charged or they suffer premature failure). If you do a lot of short trips, using a "Battery Minder" (not a trickle charger) that is set up for AGM lead acid batteries (about $60) is a good idea.

BatteryMINDer® Plus AGM/OPTIMA Maintenance Charger / Desulfator-Conditioner 12 Volt – 1.0 Amp | All | Battery Chargers by BatteryMINDers.com

JeffD

 

This advice is spot on.

Tom

 

I see a VDC 1.3 amp model #12117 at amazon for $45. On the high end, Northern Tool 2/4/8 amp for $100. I suppose the Northern might double as a charger, whereas the 1.3 requires a charger first to revive a dead battery.

Any thoughts as to brands or features that are must have or avoid for sure?

 

Not a Charger, but a "Battery Minder".

BatteryMINDer® Plus AGM/OPTIMA Maintenance Charger / Desulfator-Conditioner 12 Volt – 1.0 Amp | All | Battery Chargers by BatteryMINDers.com

The competing product line is "Battery Tender"

Battery Tender - Home of the Battery Tender Jr. - Batterytender.com

But the "Battery Tenders" do not have the added feature in the "Battery Minders" that prevents (and often corrects) "sulfation" (The creation of a layer of sulfur compound crystals on the surfaces of the lead plates which reduces the effective plate surface area) which is a major cause of premature lead acid battery failure.

JeffD

 

Your battery minder link is the 12118 model which seems to only be for AGM-type batteries. The 12117 model says all 12-volt, including AGM-type. And the 12117 is $5 less at the VDC site. Seems odd.

If I could get one unit (12117) for all my cars, that would make me happier than only being able to use it on the Prius... Any thoughts?

 

Prius consumes approx 30mA when the system is off.
If your Prius stayed off-position for 12 hours (overnight), it consumes 4.32 Wh of 12V electric energy.

One gallon of gasoline has 36,370 Wh of energy, or we can pull 12,730 Wh energy by 35% Prius engine efficiency.

If you charged the 4.32 Wh by your charger, you can save 0.00034 gallon of gasoline per night.

Ken@Japan

 

ken1784, thanks. My concern is with making sure the battery gets an initial charge and that the 12V draw while short-trip driving (not merely while off) is accounted for to maintain its charge. Also, longer term with extending battery life via desulphation. My dog sleeps in the garage with the car, so I cannot open the gargage door and leave the car running overnight (CO). I do leave it running when I can, but it is my wife's daily driver. She would have lights, stereo, wipers, climate control, NAV, Bluetooth, cell charger, etc. going. Am I worried over nothing? Something is killing batteries early in some cases.

 

I assume that there was a reason to raise the chaging voltage in the AGM specific model. The only drawback I see is that 12117 may result in slower AGM charging than the 12118. A call to their tech support at (800) 379-5579 Ext. 206 line may be in order.

JeffD

ps. My Jetta also has an AGM battery

 

I don't know how short your wife drives, but...
The 2010 Prius DC-DC converter has max 120A supply capability, and I think 10 minutes driving is enough to recover the 12V battery discharged for a week rest.

Ken@Japan

 

But I thought it would only send 1 amp to the 12V, and only while in ready mode. Everything I've seen talks about how slow the system charges the 12V. How can it send 120A to the little 12V without overcharging?

edit: Guess you are saying the converter supplies the load while driving, so only the tiny draw while off has to come from the 12V?

Sorry to be a pest, but am ignorant in matters electrical...

 

I agree with jdenenberg, if you have any reason to worry that your 12V acc battery is in need of assisted living, a BatteryMinder set up the way you suggest in your original post would be a nifty mod. You'll probably extend the life of that 12V battery quite a bit in the process.

- D

 

I believe your 1A is the 200V HV battery current to the 12V line for keeping Prius in ready mode.

The DC-DC converter supplies a constant voltage and it keeps the 12V battery 100% charge level. It's only less than 0.1A trickle charging.
The max 120A is going to head lamps, PTC heaters, fans and others on the 12V line.

I think you're correct.

Ken@Japan