Searched but didn't find.

A random question on this hot afternoon:
If one runs a pre-cool cycle, is the battery cooling loop activated as well? Or does it wait until the car is started (assuming it doesn't reach the trigger temp for cooling even when off)?

That's an interesting question. I haven't seen any data on it. Initial gut reaction: if I built it, it would turn on the TMS when it preconditioned, unless there's a reason not to I'm not aware of.

Well it certainly works the other way around. If you have the HVAC set for fan only, when the TMS activates to cool the batteries you get cabin cooling at the same time.

VIN # B0985

It occurs to me that it really only matters if unplugged. If plugged in, it controls battery temps more tightly.

I agree with saghost. Even unplugged, I would default to whatever parameters it uses if the car is ON, reasoning that the car was going to be driven shortly and the battery cooling will run anyway.

The Leaf battery issues got me thinking - if I was parking a Volt outside and unplugged in Phoenix, I'd be tempted to run a pre-cool cycle mid-day Just Because. Yes, I realize it's effect would likely be in the noise. :)


If you have the HVAC set for fan only, when the TMS activates to cool the batteries you get cabin cooling at the same time.
Yep. I can't find a diagram but there's a single freon loop. So I think it's a matter of turning on the pump for the battery cooling or not.

I'm a Phoenix LEAF and Volt owner. I have also been concerned. Still have all 12 capacity bars on the LEAF, but I'm expecting to lose one any day now.

I found this post here. Sounds very informative:

http://gm-volt.com/forum/showthread.php?5243-Volt-thermal-management-system-temperature-band&p=45948#post45948

Thanks shrink. I had forgotten the SOC > 75% restriction on running TMS though it's not clear (to me) that was 100% confirmed from GM.

Interesting quote in there:

(2) At extreme high temps, the ICE may come on to generate power for the TMS to work faster,
but only if the car is powered on (that is, the ICE won't start by itself, unmanned)

To the best of my forum-reading knowledge, this has not been reported, even from the Arizona owners.

Thanks shrink. I had forgotten the SOC > 75% restriction on running TMS though it's not clear (to me) that was 100% confirmed from GM.

I think the OP said he discovered the SOC > 75% in consultation with a GM engineer. That OP seems quite knowledgeable.

I haven't observed the quote you referenced, but I've only had my Volt for 6 weeks or so.

Searched but didn't find.

A random question on this hot afternoon:
If one runs a pre-cool cycle, is the battery cooling loop activated as well? Or does it wait until the car is started (assuming it doesn't reach the trigger temp for cooling even when off)?Anytime the Li-Ion battery is charging or discharging (eg running 360V A/C compressor) the TMS will be active.
HTH
WOT

Anytime the Li-Ion battery is charging or discharging (eg running 360V A/C compressor) the TMS will be active.
HTH
WOTThanks WOT!

A random question on this hot afternoon:
If one runs a pre-cool cycle, is the battery cooling loop activated as well? Or does it wait until the car is started (assuming it doesn't reach the trigger temp for cooling even when off)?

I decided to sacrifice for science this afternoon - I didn't start a cabin conditioning cycle until I reached the car. Not surprisingly, I learned that WopOnTour was right. :)

The first thing I learned is that you can't remote start from either the key or the phone if the key is in the car. You can however start it and then unlock and get in the car without it stopping.

This morning I drove rather aggressively, and so I was showing 2.4kWh used for my 10.1 mile commute and a battery temp of 82F (outside gauge said 83F) when I parked. When I got in the car after nine hours of high temps increasing to triple digits (car said 106F when I finally started it,) it showed a battery temp of 90F; I'm not positive if the TMS hit the battery - if so it didn't use much power (there's a 1-200 Wh discrepancy with some of the numbers that could be TMS activity,) and the 16 degree delta could be the result of thermal mass and insulation.

The remote start hit the fan hard pretty quickly - for the majority of it the remote start was drawing around 5 kW while it ran, with momentary drops to 2.8/3.0 and an instantaneous peak of 5.4 kW. I could also hear the radiator fan running.

It seemed to prioritize the cabin - the battery didn't change from 90 for the first few minutes - but by the end of the ten minutes the battery showed 84F, clearly showing the battery was being cooled effectively. From the changes to the "battery remaining" calculation off of the reported SoC in the DashDAQ, the remote start used ~650Wh - but when I started the car, is showed 3.2 kWh used (the discrepancy I mentioned; the SoC often has a slight mismatch to the overall use for some reason - it always starts showing 10.2-10.4, but it;ll show zero when the engine kicks on and the car will say 9.9 used.)

When I turned it on, the car was soon hitting the same 5kW in Park; by the end of my drive home even though the fan was at the same speed and the air blowing cold, the draw was down to around 2kW (colder recycled air means less work for the compressor causing the reduced draw?) and the battery average temp was down to 75F.