How does the 12V battery charge?

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PPL

Member
Joined
Oct 20, 2014
Messages
20
Curious on how the on-board 12V battery on the Spark charges? Is this done from the main 21kW drive battery power or does it have a Alternator driven by a belt of the main electric motor?

Good to know when trading off mileage for heat and accessories usage.

Thanks!
 
All modern production EV's charge the 12 volt battery from the main "traction" battery.

This is done through the DC to DC converter.

Heater use would NOT go through the DC to DC, except for 12 volt features (heated seats and heater fan).

The heater itself takes its power directly from the traction battery.
 
Thanks for the feedback.

I figured as such but wanted confirmation. Basically, anything I do in the car uses up the main 21kW battery running or not. Glad I did not get the 2015 Spark EV with 19kW battery.
 
PPL said:
Thanks for the feedback.

I figured as such but wanted confirmation. Basically, anything I do in the car uses up the main 21kW battery running or not. Glad I did not get the 2015 Spark EV with 19kW battery.

The 2014 battery only has about 18.5kWH usable. The effective size of the 2015 is about the same as the 2014. I have only seen the 19kWh value published.

Most BEVs only have about 85% of the battery charge usable. For example the Leaf has a 24kWH batter but only 21.5kWH is usable, the i3 is a 22kWH battery with 18.8kWH usable.

kevin
 
buickanddeere said:
DC to DC converter is far more efficient and lighter than a belt and alternator.
TonyWilliams said:
All modern production EV's charge the 12 volt battery from the main "traction" battery.

This is done through the DC to DC converter.
Yep. This type of arrangement is typical of BEV, PHEVs and hybrids.

Even the Gen 1 Prius we in the US got (NHW11) was this way. I'm not sure about the NHW10 (JDM only truly 1st gen Prius, predecessor to NHW11) but I suspect it's the same way. You can't depend on an alternator if an engine or motor's not running. And, it makes no sense to incur more losses by running an electric motor to turn an alternator.
 
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