LiFeP04 Operating Temperatures

[Davydd]

Originally Posted by avanti

You are not listening.

Of course I guess I am not listening because you are off trying to discuss a separate "deep sleep" system that would add unnecessary complexity after I gave you all the parameters of how I would have to operate and after I pretty much said you would have to plug in or seek a warm external environment. You didn't listen to me either until maybe you found out about 36 consecutive days below 0.

I can't speak about Tesla. Their -22F critieria was one that gave me some not to worry hope so I don't know if Elite Power Solutions is just being conservative or their batteries are different enough. However, my future home will have an insulated garage and a Tesla will fit in it where my ARV won't. Also, the parking spot I parked in for 17 years in downtown Minneapolis when I worked is now a dedicated EV plug in spot. Driving and operating I said was no problem in cold weather. I would guess the same with a Tesla but you are not going to leave it at a cold airport lot while you fly off to the Bahamas for a week.

The simplest answer for my ARV and Tesla is external shore power. If those under hood Roadtrek Etrek AGM batteries are some kind of "deep sleep" system maybe one can now understand they won't amount to anything with 36 consecutive days below 0 or a not so uncommon few days for that matter.

[booster]

Originally Posted by Davydd

No. You do have to make sure you do not run your batteries down. Disconnected lithium ion batteries lose about 3% of their charge per month. With my 800ah battery bank that would be about 24 amps per month. I could easily let them sit over a winter as long as the temperature is above -4. Elite Power Solutions recommends you recharge your batteries when and if the voltage drops below 3 volts for the individual 3.2v cells. That would mean you would want to keep them above freezing in order to do so. The easiest solution is to stay plugged into shore power which I had done the past two winters.

If that 3% a month for the ARV system? If so, the BMS must remain active so some extent. One of the big selling points of lithium is the very low capacity loss while not in use, and is usually quoted as very much less than 3% which is more in the range of what you get with wet cells. Our AGMs look to lose well under 1% a month.

[Davydd]

Originally Posted by cruising7388

Fuel wouldn't be relevant with RT because their Voltstart only engages for five 30 minute periods without requiring a manual reset. Are other autostart systems similarly configured? BTW, with the seriously diminished CCA available on a battery at -25F will the Mercedes diesel crank and start at this temperature?

If the coach is in enclosed unheated storage, IMO utilizing any autostart feature would not be a good idea.

ARV requires a key start after 5 auto starts. I am not sure why it is 5 but it must be an external to Roadtrek and Advanced RV requirement. ARV can be programmed to run for a maximum of 2 hours with each restart and can be programmed to restart at any SOC you set it at. If I set my 800ah battery bank at 40% SOC charge start it would replenish the 480ah used in that 2 hours with high idle Delco alternator operating at 240 amps charging. So, in theory batteries online give up I estimate at least 4 amps per hour or 96ah per day plus the 240ah for battery heating pads. That's 336ah per day. I thus get a total of 2400ah to use with the 5 starts. That would give me a theoretical maximum of 7 days of heat keeping the batteries above 41 degrees. 10 running hours probably would also require refueling. That's all theory. Absolutely no way would I leave a B unattended in cold storage relying on that. I could probably do that if in my yard and observed but would then probably have sleepless nights.

Do diesel engines start in extremely cold weather? That's a good question. I have started my B at -15 degrees at the lowest and that took some cranking effort I am not sure auto start systems can do. There is a preheat. Also I have Trik-L-Start to ensure my chassis battery stays sufficient. -25? All bets are off.

[Davydd]

Originally Posted by booster

If that 3% a month for the ARV system? If so, the BMS must remain active so some extent. One of the big selling points of lithium is the very low capacity loss while not in use, and is usually quoted as very much less than 3% which is more in the range of what you get with wet cells. Our AGMs look to lose well under 1% a month.

That 3% per month is disconnected batteries per Elite Power Solutions not ARV. Actively connected to a BMS, EPS says to double that for checking or to keep above 3v and recharge as necessary. If you are actively connected in an ARV then you are going to also have all the other parasitic discharges which I give as about 4 amps per hour with inverter and refrigerator off. I could probably reduce that further by turning off two breakers.

[cruising7388]

Originally Posted by Davydd

ARV requires a key start after 5 auto starts. I am not sure why it is 5 but it must be an external to Roadtrek and Advanced RV requirement. ARV can be programmed to run for a maximum of 2 hours with each restart and can be programmed to restart at any SOC you set it at.

Being able to program the SOC point for a restart in the field is a nice touch. Roadtrek Voltstart is factory programmed, the particular thresholds dependent on whether the batteries are lithium or AGM. I don't think the owners can adjust this. All they can do is engage or disengage the function. Perhaps the dealers and repair facilities can.

Re the ARV programmable restart, is the SOC parameter limited to what the battery BMS would shut the battery down on its own initiative or can it override the threshold established by the BMS?

[cruising7388]

Originally Posted by BBQ

Have you looked at a Tesla battery?
It has its own liquid cooler and heater.

From the manual: “Do not expose Model S to ambient temperatures above 140º F (60º C) or below -22º F (-30º C) for more than 24 hours at a time.”

The bottomline is, for long term survival, it has to be plugged in.

No, I sure never looked at one but I'm aware that these electrics temperature control their batteries. It would be interesting to learn how they arrived at the -22F figure.

[Davydd]

Originally Posted by cruising7388

Being able to program the SOC point for a restart in the field is a nice touch. Roadtrek Voltstart is factory programmed, the particular thresholds dependent on whether the batteries are lithium or AGM. I don't think the owners can adjust this. All they can do is engage or disengage the function. Perhaps the dealers and repair facilities can.

Re the ARV programmable restart, is the SOC parameter limited to what the battery BMS would shut the battery down on its own initiative or can it override the threshold established by the BMS?

After the ARV engine auto starts it goes into high-idle mode keyless. High idle I found doubles the amperage charging over just standard idle with a key start. It will shut off at the end of the time you set it for up to 2 hours, or it will automatically shut off when SOC reaches 100%. You can also manually shut it off at the Silverleaf monitor touch screen. There are other ways to auto start. You can do so remotely with a Compustar key fob or with a Compustar app or RVCair app which mirrors the Silverleaf controls. You can turn it off with those apps as well. With any auto start keyless method, they will shut off as well by simply depressing the brake which has to be done if you intend to put the B in gear and drive off. The van doors do not have to be closed. I believe you can autostart your engine with the Mercedes Benz key fob as well but the doors have to be closed. You can go nuts trying to figure all this out.

Another ARV feature is you can program when you do not want the engine to auto start. I leave it at not starting between 10 PM and 7 AM which are normal quiet hours in a campground. I can pretty much with monitoring information at hand tell when it would have to auto start. We haven't ever needed it other than some extensive testing I've done.