How does Tesla's octovalve give a 10% increase in range?  - Page 1
Forum section: electronics / general

author: DougSpindler
author_rank: Super Contributor
timestamp: September 06, 2020, 06:57:15 pm
content: I'm not an engineer but Tesla came up an octovalve which does something to the car's batteries to increases range by 10%.Anyone understand Tesla's octovalve? And what that does to the Tesla batteries to increase the range?(21:37)

author: tom66
author_rank: Super Contributor
timestamp: September 06, 2020, 08:11:49 pm
content: It... er, doesn't.I like Sandy, but he's clearly a mechanical engineer and when talking about these types of things, he's a little out of his depth. Model S and X have all used motor heat in the past as a supplement to the cabin. My Golf GTE can use the motor/drive inverter, and engine heat too. Priuses do the same thing. Oddly, the Model 3 omitted this thermal path and only features a PTC heater for the cabin, perhaps for cost reasons as Tesla did not believe it worthwhile for the small amount of heat it provides (~1kW or so.) I'm not sure if the Y has reintroduced this with Octovalve.There's nothing too unique about this. When the outside temperature is warm enough (14-15C but overcast so little sun) my car can keep the cabin comfortably at 20C using just the inverter and motor excess heat. And it requires very little hardware to do so, the HV system coolant is just piped through a heat exchanger and if that doesn't provide enough heat to warm the cabin a PTC resistive heater supplements the heat. The loop temperature only needs to be about 50C or so to get acceptable cabin heat so this presents no danger to the drive components.Model Y does have a heat pump, and I think this is what Sandy is confusing when he says the car can use waste heat. But the heat pump here is just a reversible A/C system that can warm the cabin or cool it, using regular ambient air on the A/C radiator. Octovalve might be involved in routing coolant (possibly now including the inverter/motor) and it's a clever design, but that's all it is, there's no mystery behind its operation on a fundamental basis. Heat pumps are not uncommon on EVs for obvious reasons: new Renault Zoe and Leaf have featured them, I think the Kia e-Soul has one, and e-Golf had it as an option. Sadly, they never offered the GTE with one, despite the A/C system being comparable to e-Golf.

author: DougSpindler
author_rank: Super Contributor
timestamp: September 07, 2020, 04:28:31 am
content: Thank you for your explanation. You got me thinking about this differently. Could it be they can claim the 10% increase in range from the octovalve because oof efficiencies in heating cooling the cabin? And nothing to do with the batteries?

author: tom66
author_rank: Super Contributor
timestamp: September 07, 2020, 06:59:00 am
content: I think that cabin heating is between 5-10% the energy required on longer drives (my car uses between 1.5 - 2kW on cabin heating, presumably a Y would use a bit more) so if you could take as much of that from the motor, and supplement the rest with a heat pump, it's possible to see how a 10% range improvement could be had, but I think this would be a particularly nice edge case where everything lined up well.

author: ConKbot
author_rank: Super Contributor
timestamp: September 14, 2020, 02:57:26 pm
content: Are they doing anything clever like using the heatpump for battery pre-heating in cold conditions, to make that more efficient? Or is it just purely to supplement a traditional heater core.