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  Topic Review (Newest First)
04-13-2019 10:45 AM
Foolios Wow, I've been looking all over for info like this. These are some really good ideas.

"The onboard charger won't charge your battery. A separate charge plug, or a tap on the J1772 connector to your own onboard charger, will be needed to fill up. There may be issues with the J1772 interface at a public charging station, as you are now pulling more power than the car is "telling" the charging station about. Or not. "

Using the lower charge setting will help ya avoid that issue at the public charger. But you'd have to hope noone ever drove your car and changed that setting during their trip/charge attempt.
05-12-2018 06:49 AM
Lile001 Per the 451 Service Manual, p 24, the battery management system and the contactors for disconnecting the high voltage output are located within the battery module. There is a connector on the rear passenger side of the battery that runs everything that's high voltage.

Unlike some other electric vehicles, the high voltage Service Disconnect in the Smart (Located under the instrument panel in the left footwell) doesn't actually disconnect the battery. It disconnects the control lines to the contactor relay inside the battery. Many cars have a Center of Pack disconnect, that physically interrupts the main conductor in the battery, which is much safer. The battery terminals will not be live if this disconnect is pulled, however the battery is still live internally. I don't like this.

Pulling this Service Disconnect, it would then be safe to pull the main battery power line. I'd still be wearing voltage rated gloves and safety glasses for this operation.

The manual states that all high voltage DC will be discharged within 5S. I'd wait longer, and test the high voltage bus with a good voltmeter and gloves before trusting that it was really not live.

OK, now you have a wire that could potentially be the point where you hack in an extra battery, of the same number of cells in series as your original. In theory. This wire is exposed to the elements, water, road dust and flying gravel, so your connection better be very robust.

Another important point: The interface between this line and your range extender *must* be a relay. This line can't be left live all the time, or the battery will go flat when you park.

The onboard charger won't charge your battery. A separate charge plug, or a tap on the J1772 connector to your own onboard charger, will be needed to fill up. There may be issues with the J1772 interface at a public charging station, as you are now pulling more power than the car is "telling" the charging station about. Or not.

P56 shows a diagram of CAN bus points. The High Voltage State of Charge indicator instrument gets it's info from the CAN bus, which in turn talks to the HV battery BMS. Your hacked battery can not talk to the state of charge indicator, and you will have no idea of the additional range and state of charge unless you buy an aftermarket meter like this one.

It doesn't come right out and say this, but the HV Battery contactor relay is almost certainly controlled by the CAN bus. Unless we want to start hacking into THAT, like these guys are, we'll need a separate control for our range extender battery main contactor relay.

Some ideas for controlling this relay on your range extender batt: Simply operate the relay from a part of the 12V system that is powered when the car is powered, operate it from a manual switch, or get an Arduino CAN bus shield and sniff the bus for the right signal. If I lost you right there, then run away screaming right now I don't blame you.
05-12-2018 06:20 AM
Lile001 Here is a bit of research on the idea of adding a second battery:
1. Don't try this unless you can work safely around high voltage electricity and electronics. If your idea of checking 400VDC is to use your $5 multimeter probes barehanded, you probably don't have any business with this hack. There are a dozen videos on Youtube of people hacking spare batteries into Nissan Leafs, with the connections laying about uninsulated and loose in the trunk. There is also a great video of the aftermath of a vehicle fire in a Leaf with a hacked battery. Batteries are safe if handled safely. They are bombs if handled unsafely.

2. Smart ED 2014 (451) service manual here:

3. There is sufficient room between the rear bumper and the back of the motor/tranny/etc for a module that is 711MM(28") X 152mm(6") X 279mm(11"), theoretically if this were stuffed with 18650's this could be a 57 kg(126 lb) battery holding about 9.4 kwh, or a 50% range boost. There is some airflow through here, but given the car actually has a radiator to get rid of motor and battery heat, it is probably not critical. No reason to put the battery in the cab, except it'll get cold in the winter giving poor performance.

4. A simple, very low tech, safe, and very inefficient way to use such a battery would be to arrange it as a 36V battery, use a 36VDC to 240vAC inverter and simply hook it up to the charging port in the middle of your trip. Almost all my trips involve a long stop in the middle, I'm at the grocery store or a meeting or whatever. Just have the car bootstrap itself, or stop when your range anxiety gets too hairy and plug yourself in, read a book for a while. The inverter is 80% efficient, meaning you lose a lot of juice, inverter needs to be fan cooled and cannot be underneath the vehicle. Put the inverter in the cab, maybe under the seat, and leave the windows cracked open on a hot day. 36V is a lot safer than 400V, but still if you touch two bare terminals you basically just started up a 1000A welder, so be very careful. There's your hack.

5. The next level hack, in theory: Here's a whole series of videos showing a guy hacking into a Nissan Leaf battery pack, Smart has a lot of the same general components:
01-04-2018 05:44 AM
jenkinskg Another question, my 2013 on my code scanner says it has the 22kw charger?
Also on a 240v line I see 5.2kw charge rate?

any ideas
01-04-2018 05:38 AM
jenkinskg Sounds great, I was even thinking of just have 2 packs and a reserve switch when one goes low.
solid state relays
01-04-2018 05:35 AM
jenkinskg I want to do the same to my 2013, the guys at EV west do a lot with tesla battery packs.
My range right now in cold weather is so low that I cannot drive to work and back without worry of running out.
I think a parallel 400 volt pack is possible, there are used packs out there from wrecks etc.
From what I have seen I think an extra 7kw battery in hatch would be easy.
Good connections would be the hardest.
Your warranty would be the worry, mine is over I believe and I have a new battery anyway
11-18-2017 11:36 AM
poepad205 The simplest way is to acquire a smart battery, and just install a mechanical single pull double throw switch. Then you don't have to do anything else. The system will see the extra battery just like the installed battery. It will charge it like like the installed battery. One of the problems with tucking it here and there is BMS. There is always putting the extra battery on a trailer. And if you are smart enough you add a generator. Actually I believe this would be a great business making this kind of range extender trailer.
11-17-2017 06:37 PM
Lile001 I've thought along these lines as well. Just to calm down the naysayers, I'm an electrical engineer with high voltage experience, who has worked in a product development lab and who has built home-brew electric vehicles. In other words, a qualified hacker. The warrantee is already up, so what the heck, let's hot rod this thing.

Now, programming the Smart car dashboard battery monitoring systems to tell you how much range you have would be, IMHO, a formidable task, unless you happen to have the source code (not likely they will let loose of it) and a programmer interface. You'd have to know what processor is used, what programming language, and a lot more. I could do it given those tools, but I can't imagine them releasing the source code for hackers to play with.

It should be theoretically possible to put a battery of the same voltage, chemistry, and number of cells-in-series right in parallel. Tapping in at the high voltage disconnect is a possibility, for instance. Tap in your own high voltage disconnect for the spar batt on the line side of the existing high voltage disconnect, so when a mechanic pulls the disconnect all batts are disconnected.
The second battery could be monitored with a separate system, or not at all. Experience and a little math will swiftly tell you how much range boost you are getting. You'd just know to add XXX to your dashboard range readout. One of my electric vehicles works exactly that way after I added a spare batt. You could arrange the spare batt to provide a steady, small current when there was any demand.

There is actually quite a lot of room in the Smart. A spare battery does not have to be all in one place. Packs could be tucked in here and there. There is quite a lot of room under the passenger seat, and a 3" riser under the passenger seat would still put my partner's eyes well below the roofline, make enough room to put a rack of 18650's under there. I'm short, there's a good 6" behind the driver's seat. Screw all those tall people wanna drive my car. There is a great gap of room under the back, right behind the motor and transmission and in front of the rear bumper. Needs to be some cooling airflow back there, but a significant batt could hang between the frame rails behind the tranny. No need to take up precious interior room. Just be sure to bolt it down, accidents are much worse with heavy objects flying around the cab.

For charging, the thing to do would be to tap right into the wires on the back of the J1772 female connector. Your battery would of course have it's own BMS, and there would need to be an interface between your batt and the AC terminals - a stack of series'd Mean Well HLG-320H's would allow you to charge from 120V or 240V through the same cable. They are waterproof, could hang under the rear cargo lid. I've got an instructible about making a charger for a 72V Lithium battery from a similar Mean Well power supply, can't post the link 'cuz of some rule here but you can google "invention1 mean well electric charger" and find it. Some mods of the J1772 interface might be needed to convince the charger to give you more power, I don't know what the Smart ED charger interface is telling the charging station. The wikipedia article on J1772 is a good place to start on this signalling interface protocol.

Or you could just go for an additional J1772 plug. If you are charging the spare batt at home exclusively, it could just be a 240V plug. Charge the main battery via the standard J1772 plug and the spare battery via a separate cable you've added. This would actually be simpler to build.
11-07-2017 12:07 AM
poepad205 Very simple, you make up a pack the same voltage.
Install a switch between the batteries and the controller.
So the controller sees the batteries one a time.
The procedure would be to with the car off, switch to the extra battery pack.
Run it down to 20%, stop the car, turn it off and switch to the main pack.
Charging, Charge up the main pack first, unplug the charger,
switch to the extra pack, charge it to 80%.
04-01-2015 12:17 PM
cockerchrisjoe It's a big job i realize and it might not be possible at all but I figured it would be worth a look into it . If its something that can be done more than worth it to say my electric smart gets the same range as a 40kw Tesla
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