Umm... there are RELAYS involved.
No 24v, = relays that are 'open'.

-John

P.S. read post #18.

 

John, I thought about a relay on the input side of the battery heater. But all conventional relays have coil resistance which can be measured with an ohmmeter. The one thing I didn't think to try was to check resistance with the 'diode' feature on my meter, in case they are using a bi-polar NPN or PNP transistor, or a Triac on the input side, instead of an actual contact relay. What I really need to do, to put this thing to rest, is connect an external 24VDC to these two pins 1 & 6 with an ammeter in series, and determine once and for all if the battery heater really is connected. And whether it is or not, I wouldn't bet the farm that my 08 FEH AWD is like all the other 08 FEH?? For some reason, there seems to be some variations in this year. Like 'why does mine have the plug at this connector, and Hugo, from Ontario, not, and the are both 08 models???

You mentioned in one of the earlier posts about how your 05' reacted in really cold weather, where the ICE modulated the SoC between 53% and down to 49%, etc, which exercised the pack, and raised the temperature pretty quickly.

If I discover that the heater doesn't turn on with 24VDC, then I do hope that Ford at least modified the software to do something more?

The previous poster mentioned how the HV battery capacity is so great, that it would probably never need any 'boost' to start the engine. I agree with that statement wholeheartedly.

 

You know more about relays than I do... so I'm very curious to hear what you find out. I hear a click every time I plug in... that's all I know.

Umm.... not so fast... the pack in the back is high voltage, but has a similar capacity of the 12v battery under the hood... owners have found the HV battery will start the car at SOC of 25%. But I've heard of at least two people who had a battery too weak to start. Those two didn't have a SG, so we can only guess what the battery pack level was...

 

Wow, if the HV pack couldn't start the engine, the SoC must have been really low. In a non-hybrid auto, a good quality battery @ 12.6VDC, with a cold cranking amp rating of say 700, will produce 8.8 kw of starting power.

On the FEH, I remember reading a fully charged 330V HV battery pack can deliver 78 amps max, which is 25.7 kw. This is awesome power. However, if the pack and engine are very cold, and the pack is greatly discharged, and the cold has limited the Maximum Discharge current, things change. I do believe the SGII can be used to make some rough order magnitude calculations. In theory at least, TBV * Mxd (Traction Battery Voltage multiplied by Maximum discharge current (available)), will give you the available Kw of energy for starting. Basically you have the SGII readings to calculate power by ohms law, P=EI (Power=Voltage times Current).

But I'm sure Ford wouldn't have put the jump start feature into the production models if they didn't envision a need.

As soon as I get a chance, I'll power the HV battery receptacle with 24VDC and report on the results. Initially, it appears the circuit is not connected inside the battery pack on my 08 FEH AWD.

 

I apologize in advance for the length of this post. But many 08 FEH owners will hopefully want to know this.

Yeah!! Yeah!! I managed to check out the 08 FEH AWD HV Battery heater function a few minutes ago. First John (GPSMAN1), the click you hear when you plug yours in is indeed coming from within the battery pack.

For any 1st time readers, the Engine Block Heater (EBH) accessory for the 08 model year is advertised as not including the HV Battery warmer like it did in the 05-07 model years. But a warm battery is almost, if not as important, to EV operation, as CHT. The coolant water/cylinder head temp rise rapidly, and enable EV mode, but the battery temp rises slowly, compromising the charging capacity of the pack, which greatly limits EV mode time. So if you have pre-warmed water with the gold plug EBH, but a cold battery, you may get to EV mode, but you won't stay there long until the pack gets warmed. John posted some representative graphs in another thread today (thanks) showing the relationship between battery temp and charging capacity. My car has the battery warmer plug at the pack, but NOBODY with an 08 model has located the termination end of this cable in the engine compartment to attach to a 24VDC source. Thus the Ford claim that this feature was eliminated for the 2008 model year . Furthermore, another poster, Hugo, informed us his 08 model doesn't even have a plug there at the battery?????? What have you done Mr. Ford?

Anyway, I previously measured the resistance on the receptacle side at the battery with an ohmmeter (pins 1 & 6), and it showed an open. I assumed that the circuit was not connected, which would further substantiate ford's claim. But I stated earlier today in the other thread that I would check again tonight. Sure enough, with my meter set to the diode setting (> .6vdc at the probe tips), I got a quick reading like what you see when measuring the resistance of a capacitor (you EE's will understand). Reverse the leads, or use any other setting, and it measures open.

So I hooked up a 12VDC lawn mower battery and a 12V battery charger in series with an ammeter in series with this (had about 21VDC instead of 24VDC), and when I touched the probes to pins 1(neg), and 6(pos), BINGO. I heard the click John described (like a relay picking up), and measured 2.64A on my meter. Just before hooking this up, my SGII-xg showed Tav of ~68F.

The circuit IS INDEED CONNECTED on my 08 FEH AWD. The current draw is exactly as I would have expected for 21VDC input voltage. As I've stated earlier though, I don't think all 08 models are built the same .

Since I still don't know where these two wires end up (I will continue to look for that), I can Tee off the harness near the battery, rig up a 24VDC supply, and have the capability to Pre Heat my HV battery just like you 05-07 model year guys. One of the other posters reported he found two wires matching the 08 color code in the middle connector on the firewall. Why they would terminate there I don't know, because I don't have a factory wiring diagram. But now that I know the battery warmer feature actually powers up, I will try to locate on my FEH and verify with the ohmmeter. If they are P/O a larger wiring harness, I will connect my external 24VDC supply via a blocking diode.

I AM A HAPPY CAMPER NOW.

 

Very Kewl Ken!

I'm just glad you didn't give up after you got the infinite Ohm reading!

-John

 

Great news and finding. Now is it possible to rig up a portable power source that can heat the HV battery independently--like what you might want to do at work?

 

We drive hybrids, and we LOVE technology, so we don’t give up easy. I think most folks who contribute on this website are passionate about hybrid technology, how it works, and how to utilize all the tools available to us to max. the capabilities of our vehicles. I wish I had a schematic of the input circuit to the HV battery heater, how it really works, but I don’t. I would like to know more about the cut-in/out temperatures in the heater system.

After studying and working in electronics for the past 45 years or so, and troubleshooting circuitry every day, you come to the realization that “some days are diamonds, and some days are rocks”. I still have a zillion more questions that I want answered about this wonderful but many times confusing FEH hybrid beast. I’m learning from all you experts, and contribute when I can.

Cheers, KenE

 

Hi everyone ... reviving an old post!

I haven't bought or installed the EBH for my '07 MMH, yet. I'm thinking about doing now before the cold weather hits.
Just a couple of questions for the experts out there:
1. I drive about 30 miles one way to work. It's about 1 hour each way, total - depending on traffic. Do you guys think it's really worth the install and cost of EBH? Lately I been getting between 30mpg & 40mpg and I'm loving it! I get gas once a week, which is great!

2. BillyK mentioned something about a portable power source for the HV battery. Is this really possible? What would I need for that? I noticed in the parking deck at work that there are external outlets, so maybe I can plug my MMH in!

Thanks
Cathy