Reserve battery pack

Reserve battery pack

So if an ICE car can have a reserve fuel tank, why not a reserve battery pack for the Model S? This could be an add on down the road! How about installing an adapter or jack into the trunk cavity where the jump seats are stored? This connector would tap into another circuit that leads to the main computer system and be shown as the Reserve Power or Reserve Range. Using Tesla's battery tech, and maximizing that cavity's volume, could we squeeze another 50-75 miles out of this reserve battery? My thoughts are that if the Model S can tow a couple of kids (100 lbs?) plus luggage, perhaps we can better use that space for reserve range.

We need range that gets closer to ICE cars: 350 to 400 miles on a single tank. However, for my daily driver, the Model S fits the bill and then some!

AoneOne | 13 febbraio 2014

Between at-home charging and the rapidly expanding supercharger networks, most Model S owners are quite happy with the current range.

The extra 50 miles you're asking about is similar to the difference between the 60 kWh and 85 kWh models, which differ in cost by about $8K (depending on the exact accounting) and in weight by 183 pounds.

One would also have to consider safely mounting and protecting the batteries and adjusting the suspension to cope with the greater weight and different front/back weight distribution.

negarholger | 13 febbraio 2014

I could seen in 10 years or so a 150 kWh pack where you have a 15 kWh = 50 miles reserve at the bottom, 5 kWh bottom reseve not the brick the battery and a 10 kWh cusion on top for e.g. battery degradation... that would give a 350 miles EPA range with some extra. Goal is to make the EV so simple that you never have to think about the inner workings (like we do today).

youyouxue | 14 febbraio 2014

Took a double take on this. Thought you typed 'reserve gas tank' at first, and it brought back horrid memories of watching BMW's i Series commercials...

Anyways Tesla has stated that they will add battery technology to the Model S gradually, and I expect 135 kWh capacity in the near future. I think the matter is more about what people need, and not about how much the car can hold.

redacted | 14 febbraio 2014

I'm not sure the advantage of a reserve pack any more than a reserve fuel tank (that is, the only advantage being psychological) and I imagine it would add a good bit of complexity.

If you want the psychological advantage, it could be done in softw... oh wait, it's already got that. There is the ~18 mile reserve when you go below 0. Or so I've heard.

J.T. | 14 febbraio 2014

So if an ICE car can have a reserve fuel tank, But why would an ICE car have a reserve fuel tank? Is there a shortage of refueling stations? Are there gaps in the refueling network that are too big to cover on 1 tank of gas?
Wouldn't it be better to have a piece of paper on the steering wheel that says, "Go get gas!" I guess next is people carrying around MREs just so they won't starve to death before reaching the next MacDonalds.

PaceyWhitter | 14 febbraio 2014

The best way to have a reserve battery would be to make it removable, IE: you only put it in when you are going on long trips and otherwise you don't sacrifice the weight or the storage room. Otherwise you are just talking about making a larger battery.

The problem with the removable idea is weight and complexity. As has been said above, to make a 50 mile pack it would weigh 150+ pounds. In addition, it would have to have battery conditioning systems that would also hook into the car, which would further add weight. Finally, how would the battery keep itself conditioned when removed from the car? I doubt that anyone willing to spend the money on the reserve would be happy if it died in a year, but without active conditioning, that is a possibility.

I think the best solution is a bigger battery, which I am sure Tesla is working on.

Skotty | 14 febbraio 2014

It's a reasonable desire. Perhaps even bordering on out of the box thinking. Imagine if the battery was a set of plug-and-play modules, where an owner could add or remove them in order to have the range they need for the day, month, trip, or whatever (up to some max capacity). However, in the end, it's far less trouble to just have a larger capacity battery. Hopefully we will see that in a few more years. I agree, despite Tesla already far exceeding the range of others, I'd still like to see us get to batteries that give around 350 EPA range.

AoneOne | 14 febbraio 2014

I expect that, in the future, we'll look back at the 85 kWh battery with the same attitude that we regard today's Leaf battery. I look forward to that day.

Brian H | 15 febbraio 2014

Tesla nixed the add-on metal-air/frunk idea some time ago. The wiring and cooling connections are entirely missing and not workable to "patch in".

carl.leermakers | 15 febbraio 2014

I'm surprised that people compare Model S range with ICE car range. Who cares about range when you have an ICE car - on any highway you'll have the opportunity to fill up anywhere, within five minutes, so no ICE car driver will ever even think about range. I have never let my decision to buy an ICE car depend on the range it would get out of a full gasoline tank, and I am quite sure very few other people do!

With a Tesla, my reasoning is different: I need to be able to do 250-300 km (in worst-case circumstances - rain, wind, three or four people on board, traffic jams, etc.), be able to charge at location (assuming for example a four hour meeting), and get back. If I need to travel more than 300 km I will always be taking a high-speed train; if I need to do more than 800 km, I'll be traveling by air. I'm sure that's true for nearly everyone in Europe. So being able to do more than 300 km (one way) on a single charge is not really an issue; we would take train or airplane anyway.

So we don't need a 1000 km battery (we're not going to use our cars for those distances anyway).

The only thing we need is a big network of SuperChargers so we can manage our +/- 200 km traveling, to get back without range anxiety!

NKYTA | 15 febbraio 2014

@carl.leer, don't you ever take road-trips to national parks or other destinations? I do, so I'm hoping like AoneOne that the 85kW pack is like a leaf battery in a decade.

2050project | 17 febbraio 2014

FYI - If you're a member of AAA, they just started and EV mobile charging initiative:

Roamer@AZ USA | 17 febbraio 2014

How about a small roof mounted propane powered ram jet that kicks in at 60 MPH. The jet exhaust stream would look pretty cool at night. Just open the pano to turn it on when you want a little range boost for highway travel.

Thom EM | 17 febbraio 2014

I was at Yosemite NP last week and there was a Model S there in the parking lot of the Yosemite Lodge. There are three charge points in the park and zero gas stations.

There actually are two reserve tanks of about 4 kWh and 5 kWh built into the 85 kWh Model S battery system. That is, the gauge reads zero miles remaining when there is in fact another 15 miles remaining, plus another 10-12 miles that is inaccessible to protect the battery from "bricking" if left in a discharged state.

This information came from a post on that I have since been unable to find.

tes-s | 17 febbraio 2014

Instead of a reserve battery, why not just a higher-capacity primary battery?