Here is an excerpt of a GPSman1 posting on an engine block heater thread that mentions the jump start heating operation:
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Kermit... the "jump start" button helps boost the voltage of the HV battery by WARMING it. This has been discussed many times, in many places. ( searching for "official" Ford documentation of this, but I think GaryG has also seen this in print... )

Ah... here is it from Helms Workshop Manual, CD-ROM 2004 edition:
"NORMAL OPERATION:
When the jump start button is pressed, the jump start control module within the high voltage traction battery uses the low voltage battery during an 8 minute process to heat and [therefore] step up the low voltage [in the HV pack] in an effort to charge the high voltage battery to the point where it may start the engine and operate the motor generator within the eCVT"
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All I know is what I read around here and in my owners manual. So what is happening battery warming or battery charging?

 

David, I found a section in the workshop manual that talks about the "Jump Start Control Module Fault" on page 414-03-31 of the '05 workshop manual. One of the things that page state is "the vehicle (and the HVTB) must be at room temperature for the jump start proccedure to have optimum effect. "Under Normal Operations" it says "the jump start button is momentarily pressed, the jump start control module within the HVTB uses the low voltage battery during a 10-minute process (8-minute charge plus 2 minute rest) to step up the low voltage in an effort to charge the high voltage battery to the point where it may start the engine.

Everything I read says this is a charging process, not a heating process, and the minimum SOC must be at a minimum of 30%. If John can give me a page he is reading that states it's a heater, I'll confirm that for us.

GaryG

 

Gary... I already gave the Helms reference elsewhere.

The truth is, WARMING the battery gives the EFFECT of CHARGING the battery.

Lay people, and the lay person language of these over generalized manuals use the terms interchangeably, since a "charge up" is what is perceived.

TECHNICALLY from an engineering standpoint the HV battery is being WARMED.

The EFFECT is the HV battery registers a higher charge and can output more watts or joules, or whichever units of measure you wish to use.

I'm speaking from a technical standpoint, you from a more realistic view.

Let's just say both are happening when called for, and agree that this procedure is useless when the HV battery is at 40% ( normal ) or above.

This is turning into a which came first, the chicken or egg senario.

Is the battery being warmed because it is being charged?
Or is the battery being charged because it is being warmed?

The second is simpler, and would take less engineering, materials, and cost.
#2 is most likely.

I rest my case and see no need for further discussions.
-John

 

What about those of us that live in a warm climate and the outside temp is well above the optimal 82F? If that were true, heating the battery would further hinder battery effectiveness. You could in effect, never jump start the HV battery if it got below a 30% SOC in that kind of weather, and possibly drain everyone's battery in the city in the process.

GaryG

 

(Sorry, the little kid in me) Wow, now I can hold the city for ransom! Pay me or I'll drain everyone in the cities battery!

Okay, seriously, I can understand where you're coming from John, that the process must warm up the battery, but I'm wondering if under normal operating circumstances that really makes any difference to an operator if they use the button or not before they go out. Or just how much of a difference that really makes, as the ICE is just as cold, and still needs to be warmed up.

 

Rich, having had the HV battery drained so low that the small generator by itself was heating the battery to the point that you could not increase that charging by regen says alot. I got into the habit of parking my FEH with a very low HV battery, which will heat the battery and the ICE (because of load) the fastest possible after a cold restart. I can't think of a better way of "warming a cold HV battery" which this thread is about. This way, the computers and modules can safely do the heating process the best way possible.

As far as the kid in you, I've been laughing all day over how I could drain my FEH battery and ask people in the Sears parking lot for a jump start. Work out a deal ahead of time for a percentage of the cost for the Sears Auto Department to jump start everyone trying to help me. Then I remembered I would need to wait till it got cold here to jump start my FEH to drive home.

GaryG

 

Sorry, the last I knew the COLDER the battery is, ANY battery, the higher the specific level it can be charged to. If I were a designer I would provide a means to jump-start the FEH/MMH by jumpering in an alternate 12 volt source just as is common practice.

Sounds to me as if that is exactly what the Ford design engineers have done.

 

While 82'F is "optimum" that just means optimum for life span, and continuous use.

The useful operating range of NiMH batteries is up to 140'F.

140'F will provide more power output than 82'F.
So Yes, Gary ( smarta$$ ), even you in Southern Florida may use the "jump start" button if it really comes down to it. But this will put more wear/stress/strain on the battery, and should not be done just for kicks.

The point of this discussion is that the "jump start" button is not useful for "recharging" the HV battery on a regular basis, and is not a means of input to use outside energy ( plug-in, solar ) to add amp-hours to the HV battey.

-John

 

"....140F will provide more power output than 82F..."

Would you mind very much letting us know the foundation, documentation, for your understanding? Everything I have ever read indicates that a colder battery can hold a higher specific charge level, be charged to a higher energy storage level, and therefore likely supply more power than a higher temperature battery.

 

A battery is a chemical device. You get electricity out when a chemical reaction is allowed to progress forward. Putting electricity in ( charging ) moves the chemicals in reverse.

All chemical reactions progress more rapidly at higher temperatures, slower at colder temperatures. Storing household batteries in a refridgerator to prolong shelf life is wise, but do not freeze them. ( below a certain temperature becomes a dis-advantage ) And you must warm them before use.

A warmer battery will allow a faster chemical reaction, and more electrical output, up to a point, such as near 140'F. At temperatures above this, you start to get other chemical reactions that become destructive to the battery.

Each type of battery will have its "niche". But the higher end of that temperature "niche" will allways have more wattage output... at the expense of shorter lifespan. So there is a trade off.

-John