Prius 12 volt charging current

Are you still up on this board? I'm working on the same set up. Solar panel, second battery, Engel fridge, etc. Also sorting out 2kw inverter. I have lots of questions. I just bought a 2008 with 40k miles...I plan to add a whole bunch more.

 

If you are running a 2kw inverter off a Prius that is likely too large. I know @bwilson4web and others have tested and recommend nothing larger than 1 kw or expensive damage to the ECU that charges the 12 volt battery could result.

 

Excuse my ignorance, but can anyone tell me what is the purpose of the 90 Amp shunt? Also, why was that installed in the positive cable and an induction current meter in the negative.

I am asking as I want to replicate this test on a Gen 2.

 

Shunt is just an old-school way to measure a current too high for your meter. It's just a big resistor, with very low, but very precisely known, resistance, and heavy enough not to burn up at the current levels you're expecting. Then you set your meter for millivolts, and measure the drop across it. You want its resistance value to be low enough that it won't create a significant voltage drop (to the rest of the car), but enough that it's measurable, and you can use Ohm's law to compute the current flowing through it.

Clamp meters are a lot more convenient, especially when you don't want to interrupt the circuit twice to put in a shunt and take it back out. But while any old clamp meter can measure AC, only a more-expensive Hall-effect clamp meter can measure DC. And there's a lot more going on in one of those than a simple shunt, so AHetaFan was probably using both just for a double-check on results.

My old Hall-effect clamp tends to have a consistent error around 4 amps, but also consistently in the same direction (from the clamp's point of view), so if I measure twice, once clamped each way around the wire, and take the average, it isn't too bad.

-Chap

 

Also, it seems to me that the part of AHetaFan's write-up that least pinned down for replication purposes is the "I discharged the battery about 60%-70% and powered on the car" part, which doesn't say how that 60-70% discharge point was identified. By a voltage-to-charge chart (and if so, which one, and at what temperature)? Coulomb counting? Hydrometer?

I don't know if AHetaFan will be back around to supply more info, but that would certainly be something you could be sure to specify in your own report, whether or not you end up doing it the same way.

-Chap

 

You aren't alone. I've also been looking into mounting a few small panels on the trunk just to charge the 12V battery on my Gen 1.

Because of my current discharge rate of ~230mA when car is idle and off (Progressive Insurance & Bluetooth OBDII on OBDII port), and also because I charge lots of high amperage electronics (3A to Google Pixel, 2.4A to iPad, sometimes others), I now have a setup where I daily plug in my 12V to trickle charge every night.

A solar panel will help during high device-charging days and when traveling where I'm unable to plug in at night to top it off.

I haven't decided yet on when to have it charge.
A. When car is running in daylight. (12V actively charing via HV battery) Solar may charge it too quickly in this case and reduce the life of the Aux battery.
B. When car is parked, off, in daylight.

I haven't done enough digging to find an answer, but it would be nice to find the line where the HV battery charges the Aux and either break that connection or attach a relay or two, where the 12V Aux charges from either the HV battery or solar.

 

Has anyone used a dc to dc charger for their secondary aux battery? I had originally decided the prius charge characteristics would be analogous to a smart alternator but it looks like the hv battery will just charge the aux so long as it’s accepting a current which I assume means that as long as the ignition is in ready mode a dc to dc charger will take that as a charge feed.

Is there a solution to this that anyone can see?

 

after installing two 85AH AGM batteries, my 2013 PIP while parked in READY, the ICE would kick on significantly less number of times through the night versus with the OEM battery.

After going through multiple battery isolators, I went with an Intelligent Battery Combiner and all is working 100% like it should!
Upgraded my to a Victron Cyrix-ct 12/24V-120A to use with my battery monitor smart shunt - black_jmyntrn