Charging while driving…Wild, irresponsible speculation...

[Cranky Canuck]

Dang. I appreciate the reply but thats a bummer.

No problem. I mean the traction battery doesn't really care where the electricity if from so there's nothing preventing you from setting up a solar system and running an EVSE off of it. There would be some losses going from solar DC to AC and then back to DC for the battery but it works and lots of people do that. To charge in a reasonable amount of time you'd want a pretty beefy solar array, a few kWs of generation at least but it's certainly doable.

 

[oldgeeksguide]

Wait...what? I need help understanding from you guys with EVs. I know some or all auxiliaries run on the low voltage battery, but is it not maintaining its charge from the high voltage or are there certain modes that would drain your 12v battery?

Speaking from ignorance (as is my specialty) I haven’t heard a good explanation for this issue. My rampant speculation is that it’s a software issue born from attempted efficiency. That is to say, with an ICE engine, it’s running the alternator all the time, so the battery is always getting charged until there’s a problem, like a slipping belt. My guess is that with a fancy, “software defined” phone on wheels, they try to only charge the 12v battery when they think it needs it, and sometimes they get it wrong. I would think it’s not that hard to get it right, but some brands (or their software) seem to have some difficulty with it. Another thing to note is that the HV battery may be physically disconnected when the car is “off”, so it could make sense that if the 12v is low, and the computer was thinking it was just about time to start charging then it gets turned off against its will, it could make life difficult. The weirdest thing is it seems even when the car is plugged in and charging, the 12v can still die, as indicated by at least a YouTuber with a Hyundai ioniq 5.

 

[Chavannigans]

Speaking from ignorance (as is my specialty) I haven’t heard a good explanation for this issue. My rampant speculation is that it’s a software issue born from attempted efficiency. That is to say, with an ICE engine, it’s running the alternator all the time, so the battery is always getting charged until there’s a problem, like a slipping belt. My guess is that with a fancy, “software defined” phone on wheels, they try to only charge the 12v battery when they think it needs it, and sometimes they get it wrong. I would think it’s not that hard to get it right, but some brands (or their software) seem to have some difficulty with it. Another thing to note is that the HV battery may be physically disconnected when the car is “off”, so it could make sense that if the 12v is low, and the computer was thinking it was just about time to start charging then it gets turned off against its will, it could make life difficult. The weirdest thing is it seems even when the car is plugged in and charging, the 12v can still die, as indicated by at least a YouTuber with a Hyundai ioniq 5.

I believe alternators charge as needed. They are not generators like vehicles had back in the day. They require an initial current to create the magnetic field by energizing the field windings which creates the inductive current. So they are freewheeling when voltage and amps are satisfactory and energized when needed by the ECM/ECU.


If they constantly run they will boil your battery acid by overcharging the system and create hydrogen gas (which is no bueno ). Not something the average person ever thinks about so youre not ignorant in my book.

But I do agree they need to better figure out how to "trickle" charge and maintain the low voltage battery health better. Rivian seemed to have a batch that was going out left and right for a while. Not sure if it was a poor quality battery (something that ICE vehicles deal with too) or the high voltage system was not charging it like it should have.

 

[SpaceEVDriver]

In a word, no. The traction battery has it's own charge controller, the DC to DC inverter only goes one direction as far as I understand it. To charge the traction battery you'd need to either provide it with either a 120V or 240V AC source through it's charging connector or a DC source at a suitable voltage (typically between 400V and 800V DC) through the charging port.

Some cars have little solar panels designed to keep the 12V system topped up but they don't charge the high voltage traction battery. Cars like the Hyundai/Kias that offer vehicle to load capabilities use the charge controller to provide AC power from the charging port so some cars have bi-directional chargers but they don't use the DC to DC inverter to do that. From what I understand those only work in one direct, from high voltage to low.

Also, most of the 12V batteries are very low Ah compared with the typical ICE 12V battery. The connections between the 12V and the DC-DC converter are not high-amperage. So even if you could charge from 12V, you wouldn’t be able to send many Volt-Amps to the traction battery.

If you had a really high amperage rating on the connections of, say, 30 Amps from the DC-DC converter, 12 Volts * 30 Amps = 360 Watts. We’re talking ~150 kWh in the traction batter, so, ignoring losses, which would be significant, it would take about 417 hours to charge the traction battery from 0% to full by going through the 12V battery.

You’d be better off using a solar auxiliary battery with a 120V inverter to charge through the J1772 port. That’s what I’ve been doing. It works surprisingly well.

 

[LastDayScout]

Can I use regular electricity, or do I have to use premium electricity?

 

[Chavannigans]

Can I use regular electricity, or do I have to use premium electricity?

You jest but the rates for "Congestion Fees" and "Peak Pricing" will remind you of filling up on Premium gas. lol

 

[SpaceEVDriver]

Regarding keeping the 12V charged: Most EV manufacturers do a good job. Ford recently made some updates because they were allowing the LVB to get down to a lower state of charge than would probably be considered wise. Other manufacturers have had major issues with “vampire” or “parasitic” drain of the high voltage battery. This sometimes comes from allowing accessories to run all the time (think cameras, etc), but also seems to be something else as well.

 

[LastDayScout]

You jest but the rates for "Congestion Fees" and "Peak Pricing" will remind you of filling up on Premium gas. lol

You are correct sir. Same stuff, higher price.

 

[oldgeeksguide]

I believe alternators charge as needed. They are not generators like vehicles had back in the day. …

“Back in the day” was probably the last time I crawled under a car, so that tracks.