Understanding the battery heater

[Andyw2100]

Thanks, I have not had the same success in similar situations, however I can only charge at a max of 32A (NEMA 14-50 with the crippled Canadian UMC adapter) so perhaps the higher current is what did it for you?

Could be.

I've always charged at 56 Amps, based on Cottonwood's suggestion, with an eye towards minimizing the heat and potential stress on the various components. (I do, of course, charge at 80 Amps if there's a reason to.) If it turns out that 56 Amp charging and leaving immediately takes the battery right to the borderline of no regen limits, depending on just how cold it is, I may experiment with kicking the Amps up to 64, to see if that winds up increasing the likelihood of leaving without a regen limit when it is even colder. I'm not sure if I'd want to go all the way to 80 Amps on a regular basis, though, even for just the winter. I know lots of people charge at 80 Amps 100% of the time, with no ill-effects, but I just like the idea of not pushing any of the system components too hard most of the time.

 

[AWDtsla]

Could be.

I've always charged at 56 Amps, based on Cottonwood's suggestion, with an eye towards minimizing the heat and potential stress on the various components. (I do, of course, charge at 80 Amps if there's a reason to.) If it turns out that 56 Amp charging and leaving immediately takes the battery right to the borderline of no regen limits, depending on just how cold it is, I may experiment with kicking the Amps up to 64, to see if that winds up increasing the likelihood of leaving without a regen limit when it is even colder. I'm not sure if I'd want to go all the way to 80 Amps on a regular basis, though, even for just the winter. I know lots of people charge at 80 Amps 100% of the time, with no ill-effects, but I just like the idea of not pushing any of the system components too hard most of the time.

80A @ 240V is nothing for the pack, compare to charge and discharge loads while driving. You're just running all the pumps/fans/etc that run while charging for even longer.

 

[green1]

80A @ 240V is nothing for the pack, compare to charge and discharge loads while driving. You're just running all the pumps/fans/etc that run while charging for even longer.

It's nothing for the pack, but what is it for the chargers, the HPWC, and the wiring outside the car?

 

[Andyw2100]

80A @ 240V is nothing for the pack, compare to charge and discharge loads while driving. You're just running all the pumps/fans/etc that run while charging for even longer.

Cottonwood would probably be the better person to explain why he is a proponent of this, but I'm pretty sure it's not the pack that benefits from the 56 Amp charging. I think it is likely to be the components in the HPWC and possibly the onboard chargers, etc.

 

[AWDtsla]

It's nothing for the pack, but what is it for the chargers, the HPWC, and the wiring outside the car?

It's no worse for the chargers than charging at 40A with single charger. It's no worse for the wiring if you have the right wiring. You can always go to a larger feed if you don't like the losses on the feed that meets code.

 

[apacheguy]

It heats at ~6kw from HV. It is not from the 12V

Hmm. That's the pack heater. For cabin pre-con I think it's the 12 V systems that do all the leg work.

It isn't. 6 kW @ 12V is 500A. That heater would have some monster cables attaching it at that current level. Conversely, 6 kW at HV is roughly 15-17A, which can be done on a much, much thinner wire.

So wait. What's rated at 6 kW exactly? The pack heater right? Or is the cabin heater also 6 kW?

 

[ArtInCT]

Hmm. That's the pack heater. For cabin pre-con I think it's the 12 V systems that do all the leg work.

I think we need to be clear about which heater we are talking about.... I was told that the cabin heater was on the 12 volt side and have read the traction pack battery heater is on the high voltage side.

Is this correct?

 

[apacheguy]

@Art - That's my understanding as well. Others can chime in with input.

 

[Kalud]

I think we need to be clear about which heater we are talking about.... I was told that the cabin heater was on the 12 volt side and have read the traction pack battery heater is on the high voltage side.

Is this correct?

Both heater are on the HV side.

Cabin PTC Heater is 6kW
Battery coolant heater is 5.556kW

 

[AWDtsla]

Both heater are on the HV side.

Cabin PTC Heater is 6kW
Battery coolant heater is 5.556kW

Right, and that's why you can go to battery draw while attempting to charge at 40A.

 

[green1]

Right, and that's why you can go to battery draw while attempting to charge at 40A.

That also helps explain why someone who charged at 56A for 3 hours had no regen limit, while someone who charged for 5 hours at 32A did.

 

[ArtInCT]

Both heater are on the HV side.

Cabin PTC Heater is 6kW
Battery coolant heater is 5.556kW

Thanks for that data Kalud!
Very precise.

What is the source of these rates?

Are you aware of the OEM manufacturer's specs?

 

[Mike Tuccelli]

I keep reading in forums words like logs and Teslalog. How can I access mine please and please forgive my ignorance.

 

[ArtInCT]

I keep reading in forums words like logs and Teslalog. How can I access mine please and please forgive my ignorance.

Mike: Here is a link to one of the newest tracking software effort, which is WEB BASED so there is no client for you to install.... -> #1

It is an experimental effort by TMC member Marc Chouinard. There are a few other softwares some of which have a client software.

These software efforts are based upon the Tesla API which is known as REST and documented here ->http://www.teslamotorsclub.com/showthread.php/13410-Model-S-REST-API?p=266884&viewfull=1- post266884

 

[Cottonwood]

So Cottonwood has seen a complete lack of regen limits, though that was before Version 7 firmware, and Version 7 of the firmware seems more conservative with respect to the regen limits (they kick in sooner, at higher temperatures than they did previously.) Also it's not clear whether or not Cottonwood typically experienced temperatures in the low teens or not.

Yes, I keep my garages at 45˚ F. in the winter. That helps reduce, but does not eliminate regen limits. In a drive through Kansas, I spent the night in Salina, KS near the Supercharger. I forgot how cold it got, but I charged to 80% before going to sleep, then plugged the car in over breakfast and set the charge to 100%. The car was charge rate limited, and it was interesting to see the charging slowly switch from cold limit to SoC charging limits; range mode was off. By the time I left the regen limits were almost gone, and then driving a little over the speed limit of 75 mph in flat Kansas got rid of the regen limit pretty quickly, even with range mode on.

Cottonwood would probably be the better person to explain why he is a proponent of this, but I'm pretty sure it's not the pack that benefits from the 56 Amp charging. I think it is likely to be the components in the HPWC and possibly the onboard chargers, etc.

Exactly! Charging at 56 Amps vs 80 Amps makes at most a diminimis difference to the battery. OTOH, it cuts power in half for the HPWC, cables, and on board chargers.

 

[FlasherZ]

Exactly! Charging at 56 Amps vs 80 Amps makes at most a diminimis difference to the battery. OTOH, it cuts power in half for the HPWC, cables, and on board chargers.

Well, technically, it doesn't cut the power in half, but it cuts heat dissipation in half. Technically you'd be right by saying "power loss" gets cut in half. The power delivered to the car is only cut by 30%, while heat loss is cut by 50%. I know you know that, just being a bit semantic.

 

[Cottonwood]

Well, technically, it doesn't cut the power in half, but it cuts heat dissipation in half. Technically you'd be right by saying "power loss" gets cut in half. The power delivered to the car is only cut by 30%, while heat loss is cut by 50%. I know you know that, just being a bit semantic.

You are correct, and my words were not specific enough. Let me try again.

Charging at 56 Amps vs 80 Amps makes at most a diminimis difference to the battery. OTOH, it cuts resistive, parasitic power loss in half, for the HPWC, cables, connections, and on board chargers while only reducing the charge rate by 30%.

 

[AWDtsla]

OTOH, it cuts power in half for the HPWC, cables, and on board chargers.

These things don't get tired. If running at design power and properly implemented it's fine. If you're saying the HPWC is poorly implemented for the design power, that's another story altogether. I don't have dual chargers (yet?) but so far it seems auxiliary overhead while charging takes more power than I^2R losses to the power source at full current, so it's just wasting power to not use it.

 

[FlasherZ]

These things don't get tired. If running at design power and properly implemented it's fine. If you're saying the HPWC is poorly implemented for the design power, that's another story altogether. I don't have dual chargers (yet?) but so far it seems auxiliary overhead while charging takes more power than I^2R losses to the power source at full current, so it's just wasting power to not use it.

I'm with you, I charge at 80A. That said, I have had my HPWC cable replaced twice because the coupling with the car tends to wear, and when that happens the temp has hit over 180 degF on the HPWC handle while charging. 56A cuts that heat in half and keeps the handle cooler. Some have said they feel uncomfortable with the heat generated by the HPWC and wiring.

I recommend you charge at whatever you feel comfortable charging at. For me, 80A - even with the potential heat on the HPWC handle (it's rare I have to interrupt charging anyway, generally it's cold from being fully charged anyway).

 

[Cottonwood]

I recommend you charge at whatever you feel comfortable charging at. For me, 80A - even with the potential heat on the HPWC handle (it's rare I have to interrupt charging anyway, generally it's cold from being fully charged anyway).

Absolutely.

I have no problem with charging at 80A and do so often when I need a quick charge. OTOH, most electronic circuits have a random failure that is strongly dependent on temperature; high temperature is the enemy of reliability for electronics. 90-98% of the time, I don't need 80 Amp charging. Most of those times, I have the current dialed back to 56 Amps to cut the heat in all the charging paths in half.