Portable in-car battery

[dsnows]

I would love for Tesla to offer a portable battery that can be carried in the car to extend the range. (Think iPhone battery case.) Perhaps a power wall that fits in the storage space under the rear deck or lays flat in the cargo space. It should plug into the main battery system. Charge the accessory battery when charging the main battery. Even if only 15-20 kWh would add significant range for a road trip.

Any reason this is technically not feasible?

 

[Mysterylectric]

Voltage. You'd need either a 400V system to parallel with the existing battery, or run it like an add on module, which would raise the pack voltage (and would need to be at the same voltage as the modules in the pack), and the system would need a massive regulator to keep the voltage limited to 400V. It sounds great, but implementing such a setup would take a lot of R&D. It's next to impossible to do as a retrofit.

 

[MSDadMich]

Sounds like someone is considering a project...

 

[buttershrimp]

May I interest you in a tasty thread? MacGuyver-Frankenstein Edition Tesla P113.5D

 

[JHWJR]

Would you want this battery device to weigh more or less than 1,000 lbs., and would you put another one in the frunk to off set the strange weight distribution?

 

[pinball_player]

How about a bigger battery instead? My comment is where do you stop? If 100 kWh is not enough, about 110 kWh? Then of course 110 kWh is not enough.

 

[MSDadMich]

That's an easy one for me. You stop when you feel there is enough of a personal safety factor to make it to the next charging station in any conditions. I think we are there. Of course if tech comes out that will extend the range with a similar weight and volume batt, at a similar price, why not use it... right?

 

[BrettS]

That's an easy one for me. You stop when you feel there is enough of a personal safety factor to make it to the next charging station in any conditions. I think we are there. Of course if tech comes out that will extend the range with a similar weight and volume batt, at a similar price, why not use it... right?

I think there’s more to it than that. Certainly being able to make it from one charging station to the next is good and is the minimum you need for long distance travel, but it’s not always convenient. I took a 1000 mile road trip with my S60 a few months ago and tried to time super charger stops with meals. For the most part I was successful as we were typically only traveling around 200 miles a day.

However, one day we went 350 or 400 miles and we had lunch at our first supercharger stop, but the second stop was less than 3 hours later and no one was ready for dinner at that point, so we sat in a Starbucks for 45 minutes and waited.

For long distance travel the ability to have a battery that’s big enough to allow you to skip charging stations if you’re not ready to stop... or even to be able to drive for a whole day without stopping would definitely be good, but clearly we aren’t there yet.

That said, though, there is a question of how much people would be willing to spend on bigger batteries. I routinely take 150-160 mile round trips with my S60 and the battery I have is perfect for those trips. I can make it there and back without stopping to charge. I rarely travel long distance and while a bigger battery would be nice for long trips I don’t do it frequently enough that it’s worth spending money on. I’m happy with my 60 knowing that it is enough to get me from one charging station to the next on the occasional long distance trips that I do.

For people who travel long distance all the time a bigger battery that lets them travel for half a day or even all day between charges could definitely be useful.

 

[dsnows]

Would you want this battery device to weigh more or less than 1,000 lbs., and would you put another one in the frunk to off set the strange weight distribution?

Haven’t thought about, but a standard power wall provides 13.5 kWh and only weighs 275 lbs. that’s no more weight than a couple passengers or some luggage. That would give you 30-40 mi. additional range. Make it 1.5X that size and you’ve got some real range (~50 mi.) and still only ~400 lbs.

 

[dsnows]

How about a bigger battery instead? My comment is where do you stop? If 100 kWh is not enough, about 110 kWh? Then of course 110 kWh is not enough.

Two things:
1. I don’t usually need the bigger battery/longer range. I only need it on a long trip.
2. I already have a battery that I’m stuck with. It would be nice to get the booster to use when I need it without replacing my car.

 

[SSedan]

And you are talking adding weight outside the wheelbase compromising weight distribution and handling vs. typical passenger weight location.
How about cooling, a small pack used independent after the big battery is going to be relatively highly loaded.

To someone who lives at a desk this is easy, to those with any mechanical experience, this is not so easy and not worth Tesla's time and money.

 

[arcus]

To sum up I can see a few reasons why not: safety (high voltage/amperage), extra weight of the battery (how would you handle getting it into the car?), not to mention negative impact on car's weight.

 

[JHWJR]

Haven’t thought about, but a standard power wall provides 13.5 kWh and only weighs 275 lbs. that’s no more weight than a couple passengers or some luggage. That would give you 30-40 mi. additional range. Make it 1.5X that size and you’ve got some real range (~50 mi.) and still only ~400 lbs.

Do you leave that in the car all the time and cart that much more weight around all the time? And if not, how exactly do you get this 275 lb. device in and out of the car?

 

[Tezzie]

It's not so much the lack of charging stations on the way to a destination. It's how to stay charged when tooling around in an out-of the-way location for a week or more. And if a regular electrical outlet is not even available nearby (within the 25' cord length of the mobile charger), then what? Interrupt the stay to drive 50+ miles or more to the nearest charging station? I guess I need to think more creatively when planning trips.

 

[mb300sd]

I'd be interested in how the BMS would respond if you injected 400VDC somewhere parallel with the battery. Do the BMS and motor inverters have separate power metering, and what the software would do if those numbers don't match up. I could lay out a 100A buck stage that would take a say 500V custom pack and slowly inject power into the HV wiring fairly easily.

 

[mb300sd]

I would assume the BMS does have separate metering, since the car meters during supercharging. The question is then what happens if the numbers from it disagree with what the motors are currently doing. Will it error out or just show that you're consuming less power than actual/regenning more.

Anyone with a salvage car want to do an experiment? I believe Tesla's warranty doesn't allow me to tap into any HV wiring.