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Old 03-18-2017, 03:40 PM   #41
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From my earlier post: "The spec for gas engine in the 40e shows 260 lb-ft from 1250 to 4000 rpm (which if true is quite impressive). For thrust available, I used final gear ratios and 28" rolling tire diameter to estimate thrust force at the max torque. I could then plot the available thrust in each gear as a flat line (simplified, I know) between the mph ground speed for each gear at 1250 and 4000 rpm."

I hope these back-of-the-envelope estimates are at least in the ballpark:

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The estimates of thrust (tire force on ground) for an 11,000 lb rig, for different % grades, are overlaid in red over the estimates of available thrust from the X5 40e hybrid using only the ICE (with no electric boost).

The available thrust is a function only of ground speed. The required thrust is actually a function of airspeed. So the graph as shown applies to zero wind speed. The red thrust-required curves may be moved to the left by an amount equal to a headwind, or the the right for a tailwind.

The 8 speed gearbox offers very high leverage in the lower gears. This is what allows the 4 cyl twin turbo to move an 11,000lb rig up a 15% grade in 35mph headwind in 3rd gear at 35mph and 4000rpm. I am OK with that, and the diesels can pass me.

If anyone sees a flaw in my reasoning or calculations, I welcome comments.

Charlie
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Old 03-18-2017, 04:23 PM   #42
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I think it is a challenge to calculate theoretical performance given the number of variables.

I would go back to a comparable vehicle, the 240 hp (with no electric assist) Ram 1500 3.0 ecodiesel, which has the same hp, the same ZF transmission, and weighs more. That diesel truck won't be passing you up the hills, even if your high voltage battery is completely flat and you are just relying on the 240 hp gasoline engine.

Here is some BMW info on the vehicle. No service manual info found so far, but there is lots of press material such as this. This is the info that goes to those writing those magazine articles.

https://www.press.bmwgroup.com/globa...07284EN/360732

I read the entire owner's manual. Interesting. But no mention of towing, except in relation to tow trucks.

Jeff
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Old 03-18-2017, 04:49 PM   #43
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Jeff,

I am encouraged by the examples you have presented in this thread. Also, we towed our 19' Bambi with a 2003 Volvo XC90 T6 (280 lb-ft, 258hp) with no problem except one slow (but successful) climb over the Bighorn Mts. It had a 4spd tranny, and the large steps between gears were awkward - we always wanted to be in 2 1/2 or 3 1/2 gear going uphill. With 8 speeds, with more short legged lower gears, and a more robust (BMW-like) design, I can easily imagine making that climb more gracefully even with the I4 260 lb-ft, 240 hp.

Thank you for the link - I will read through it.

Charlie
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Old 03-18-2017, 05:42 PM   #44
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This is getting more interesting...

In the flyer that Jeff linked above is the following:
"The energy for the electric motor integrated in the 8-speed Steptronic transmission is drawn from a lithium-ion battery, which also supplies power to the low-voltage battery for the 12V electrical system aboard the BMW X5 xDrive40e via a voltage transformer.
The 220 Amp-hr 12V batteries in our 23D are 2.64 KWh, and the 40e Li-ion batteries are 3.4 times higher at 9KWh. So maybe we could double the trailer battery life, while depleting 29% or so (efficiency?) of the cars battery when boondocking. This would be a big help for cold-weather winter ski trips, where our furnace runs a lot. This subject has been mentioned in other hybrid-related threads here.

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Old 03-18-2017, 11:04 PM   #45
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The 220 Amp-hr 12V batteries in our 23D are 2.64 KWh, and the 40e Li-ion batteries are 3.4 times higher at 9KWh. So maybe we could double the trailer battery life, while depleting 29% or so (efficiency?) of the cars battery when boondocking. This would be a big help for cold-weather winter ski trips, where our furnace runs a lot. This subject has been mentioned in other hybrid-related threads here.
I have also explored this idea, considering that I have a 90kWh battery (~84kWh usable) on my X. The conclusion I've come to, and lewster was helpful in this regard, is that one really needs to tap directly into the battery and use heavy gauge cables to connect the AS. The ideal thing to do is to just run the AS off of the vehicle DC-DC converter. That way, you bypass any losses related to charging the battery on the AS. The risk is that you deplete your TV's 12V system and somehow end up dead while boondocking.

I plan to add Anderson Powerpole connectors to my frunk on the X for this purpose. However, it's not a high priority for me, and I don't want to void the warranty on my 12V system on the X prematurely.

The thing I do know is that using the 7-blade connector is a terrible idea. It's extremely lossy due to being very undersized for the job. If you want to use your vehicle battery for boondocking backup, you really need to come up with a plan and appropriate equipment.
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Old 03-18-2017, 11:37 PM   #46
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Old 03-19-2017, 01:31 AM   #47
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Good input ohmman. I agree it needs to be done right. For us the gray tank or freah water is the first to go except for winter camping, where the furnace fan really consumes battery. We usually can hook up when skiing, but sometimes not. If the cars high voltage sysyem could be used, that would then be a benefit.

i would think the risk of depleting 12 V battery is low due to the low usage of trailer system compared to high voltage capacity. But I am new to this subject. The possibility is attractive.
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Old 03-22-2017, 05:23 PM   #48
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This article has some information on the various charge/hybrid modes on the 40e.

http://insideevs.com/1200-mile-bmw-x...ance-delivery/

My earlier comment about half battery capacity wasn't in relation to plug in charging, when it can be fully charged, but to charging over the road using the gasoline engine. I had remembered reading about a 50% charge. Perhaps it is a function of which combination of modes is selected by the driver.

Jeff
After reading the Users Manual and a few post on Bimmerfest forum, I am beginning to understand how the X5 hybrid system works. In Sport driving mode the eDrive system is more aggressive about charging the batteries, assuming you will want some electric boost to the gas engine performance. It even will devote reserve gas engine power to to charge the battery while driving under less demanding circumstances. (This compromises fuel efficiency for driving performance). It makes sense that this occurs only up to 50% charge, since that is enough for most circumstances. And it reserves the opportunity to charge further from regenerative braking, which it can do.

So the 50% charge limit applies to charging using power from the engine, but it could go to 100% if one had a long downhill with gentle braking. When applying the brakes, the motor can be used to charge the battery while providing at least a modest amount of braking - without having to use the disk brakes at all. If one steps harder on the brakes, then of course the disk brakes are used - and that extra energy becomes waste heat. The manual urges the driver to plan ahead when slowing or stopping, to allow more gentle braking.

Now, if we could just get the airstream to charge its batteries this way...
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Old 03-23-2017, 10:05 AM   #49
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Regenerative braking, a solar power generating skin, an integrated TV and coach stability braking system, an improvement in aerodynamic form, and integrated hitch system would all be nice steps forward in RV coach design. We'll all sign up when the $$$$s are right. Pat
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Old 03-24-2017, 11:41 AM   #50
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Hi Pat. It looks like you tow with a recent X5. Do you have the diesel?

Charlie
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Old 03-24-2017, 11:43 PM   #51
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Charlie - Bimmer is an X35i. Pat
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Old 03-25-2017, 12:13 AM   #52
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A bit of information for the BMW folks. Posted by invisihitch representative on BimmerFest. Note - do not believe everything you read on the Internet.

(Quote open) -- snip --

BMW expressly prohibits the use of weight-distribution hitches on the X5. And, for a while, they seemed to be taking a hard line on this prohibition when it came to warranty claims. More recently, that stance appears to have softened considerably.

As some posters on bimmerfest have pointed out, BMW's written statement prohibiting the use of WDH appears only in their own hitch documentation. Some have suggested that this means it is BMW's hitch -- not the vehicle -- that cannot handle the forces of WDH. I have pursued this with BMW for two years now, and I believe we may be close to a resolution (which appears to be supported by the softening of the warranty stance). Assuming this gets resolved in the way I hope, we may make a new product announcement. In the meantime, we continue to aligned our position with BMW.

I hope this helps, even if it's not what people would prefer to hear.

Cheers,
Daryl (Quote closed)

My apology for posting this here. It's for information only. No discussion requested or expected.

Now, back to hybrid towing discussion. It's very interesting to consider the 4 cylinder bi-turbo as a tow solution. Will be interested in your experience if you move forward. The manual charge control might well help. Charge going down and use the electric power on the uphill trip. Certainly a different use of the design. Pat

Edit - this post was originally posted in the Tesla X towing thread in error.
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Old 03-25-2017, 12:22 AM   #53
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Thanks, Pat. Good to know. Maybe BMW will be more clear on the use of WDH with their new X5 / X7 that will be launched soon.
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Old 03-26-2017, 02:36 AM   #54
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I am sufficiently convinced of the viabiliry of the hybrid for towing that we are placing an ordertoday. It will bemaybe 5 weeks before we have the car. Then theplan is to have the Curt class III hitch installed, and modified to strengthen. Also a brake controller.

So this rhread may go dormant awhile. I will definitely report experiences after we have been towing the A/S.
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Old 03-26-2017, 10:37 AM   #55
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I am sufficiently convinced of the viabiliry of the hybrid for towing that we are placing an ordertoday. It will bemaybe 5 weeks before we have the car. Then theplan is to have the Curt class III hitch installed, and modified to strengthen. Also a brake controller.

So this rhread may go dormant awhile. I will definitely report experiences after we have been towing the A/S.
Congratulations on the decision. I'll be following your experiences closely.
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Old 03-26-2017, 12:51 PM   #56
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Charlie, great news! Very interested to hear about your towing experiences with the 40e. We'll be looking for the new posts. Pat
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Old 03-30-2017, 10:32 AM   #57
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I just redisovered the "Battery University" site, which has a wealth of information about batteries, charging, electric vehicles, etc:

http://batteryuniversity.com/learn/a...ric_vehicle_ev

They quote average Wh/km values which are much lower than what I used above.

I think this site may be familiar to those who have upgraded their trailer batteries for boondocking.
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Old 04-29-2017, 10:20 PM   #58
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A brief update: We have ordered a 2017 BMW X5 Xdrive40e hybrid. We will take delivery at the BMW Performance Center in Spartanburg, SC (near the factory) on May 16 (our 41st Anniversary!). We then enjoy a long road trip home (without trailer, of course), including a stop at CanAm RV in London, ON to have a properly reinforced hitch receiver installed, then family visits on the road back to Seattle. It will be later in June before I can report on towing our A/S with the hybrid. Stay tuned for photos and reports on towing with a hybrid SUV...

Charlie
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Old 05-02-2017, 09:09 PM   #59
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A brief update: We have ordered a 2017 BMW X5 Xdrive40e hybrid. We will take delivery at the BMW Performance Center in Spartanburg, SC (near the factory) on May 16 (our 41st Anniversary!). We then enjoy a long road trip home (without trailer, of course), including a stop at CanAm RV in London, ON to have a properly reinforced hitch receiver installed, then family visits on the road back to Seattle. It will be later in June before I can report on towing our A/S with the hybrid. Stay tuned for photos and reports on towing with a hybrid SUV...

Charlie
Congrats on your new X5 40e. We had a 2015 X5d (and unfortunately had a serious accident that totaled it) and now have a 40e. We also picked ours up at the BMW Performance Center. It is an awesome experience that I'm sure you will enjoy. What color is your new X5?

However I don't tow with the BMW as we have a RAM 1500 used for that purpose. So I cannot comment on what to expect. Sometimes I'm asked which I liked best, the X5d or the 40e. It totally depends on the type of driving. For long trips the X5d was much better but for short, around town, trips the 40e is better. Better MPG and acceleration. But realistic battery life is about 15 miles before running almost 100% on the gas engine. I would think for towing the X5d would be better but maybe not!
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Old 05-03-2017, 11:11 PM   #60
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Hans647,

Sorry that you totaled the 35D. Our new car is Imperial Blue Metallic, with multi-spoke wheels and Luxury Line.

The X5 diesel was definitely the "Ultimate Towing Machine." Handling and stability with the 23D were confidence-inspiring. The torque of the diesel was overkill - easily keeping the pace of traffic when needed, although we usually go light on the throttle to save fuel consumption.

I will be posting photos and towing tales in about mid June. It is a long road trip home to Seattle from Spartanburg, SC.

Charlie
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