why is there a 12 volt battery in the hybrid

hondabuster

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ItsaMaverick

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This is the same in a tesla. There is still a 12v lead acid battery that is mission critical. The car will not operate without it. I found it very strange.
 

fbov

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Anyone remember when distributors had points and a condenser? The "points" were switch contacts running on a cam so the switch opened and closed once for each cylinder on each engine revolution. Opening and closing the 12v circuit caused the ignition coil to produce a high-voltage pulse that made the spark plug flash. You know what happen next.

I only mention it because hybrids also have "points" that could fail the same way they did in our distributors - corrosion. Making/breaking electric contact draws an arc, and that arc can damage the contacts.

The HVB is disconnected when parked. When you open a door, the 12v system energizes a step-up system that energizes the HVB contacts on the load side. When the contacts are closed, there is no arc because there is no voltage difference. That's very reliable.

So... Tesla needs a 12v, too.
 

Rkbrumbelow

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Basically, it comes down to a lot of things are designed for 12v

car makers are conservative by nature and do not want to deal with 2nd and 3rd party suppliers having to account for more voltage variables
 

Fish Chris

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So far as I know, all hybrids have a 12 volt battery as well. What they don't have, is an alternator. Instead, power from the big battery is regulated down to 12 volts (or 14.5), and then used to keep that battery charged.
 

Rkbrumbelow

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So far as I know, all hybrids have a 12 volt battery as well. What they don't have, is an alternator. Instead, power from the big battery is regulated down to 12 volts (or 14.5), and then used to keep that battery charged.
My HCH2 still has an alternator/generator I threw the big red don’t touch me switch 3 years ago. However it means it only effectively charges in the 2.5k RPM range (which may be using the IMA as a generator come to think of it) yeah cargurus says it’s the IMA doing the charging. Though they are wrong about the car not driving without the big battery. I still get 36mpg and the circuit has not only been turned off the battery is physically disconnected.
 

jimmy fitzwell

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One of the original EVs, the 2011 THINK City Car, bit the dust because of arc-flashing. Quick cycling the key with the heater left on completely destroyed it.
High voltage DC is the future (cars, heat-pumps, solar... etc.) so be careful with hacks.
 

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Hf45-based hybrids use a DC-DC converter to supply low-voltage DC, as well as the AC inverter for the AC-DC-AC conversion.

Other hybrid systems, as in the Explorer, may have conventional/beefed-up belt driven alternators.
 

es7129

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Our Hyundai Tucson Hybrid Blue also has a 12v.
 

clavicus

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Afaik, for one thing, the high voltage battery is physically disconnected via contactors when not in use. The 12v battery provides power to magnetize the contactors.

12v battery may also power certain other accessory things when the hv battery is in this disconnected state. I'm assuming that's stuff like modem, computer memory, security system, etc?
 

fbov

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Thinking about it, both cab and bed outlets offer 400W of 120v power as I recall. That's a high current draw for a typical car battery. I'll wager they use the HVB, and that's something very unique. The C-MAx did 100W, the Escape, 150W.
 

slashy42

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Thinking about it, both cab and bed outlets offer 400W of 120v power as I recall. That's a high current draw for a typical car battery. I'll wager they use the HVB, and that's something very unique. The C-MAx did 100W, the Escape, 150W.
The 2.0 has the same 400w inverter.
 
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