How do you charge your i3

Thinking about purchasing an i3. We have an older home with a 100 W service so not sure if it can handle a Level 2 station. Is level 1 ok for most owners?

Our apartment has 100 amp service. Please correct me if I'm wrong, but I believe that the 100 amp rating is at 120 v., so it would be 50 amps at 208/240 v.

I charged our i-MiEV using a small L2 EVSE (208 v. at 13 amps). I have been charging our i3 with its L1 EVSE which has been sufficient so far, but it's probably not for everyone. I am about to install a JuiceBox L2 EVSE that I will run at 208 v. and 16 amps (it will be on a 20 amp circuit). That should charge our i3 fast enough, but if not, I could upgrade our charging circuit to 40 amps (the wiring is already sufficient). Even if we charged at the i3's full power (~32 amps), we should still have sufficient excess capacity during nighttime hours when little power is being used in our apartment.

If you run power-hungry appliances in your home (electric water heater, oven, A/C), you might need to be careful charging when these appliances are on. We replaced our conventional electric water heater with a heat pump water heater, rarely turn on our A/C, and don't use our oven much, so I don't anticipate any tripped circuit breakers.

JoeKirdahy said:

Thinking about purchasing an i3. We have an older home with a 100 W service so not sure if it can handle a Level 2 station. Is level 1 ok for most owners?

Click to expand...

100 W service, you mean 100 amps? Are you in the U S or ? It makes a difference where you live. In the US they include a 120 volt evse that requires about 18 hours to charge from empty and no it is not acceptably for most and so most people buy a 240 volt 30 amp evse which reduces charging time to 3.5 hours. If you live in Europe it is another case depending on where you live.

alohart said:

Our apartment has 100 amp service. Please correct me if I'm wrong, but I believe that the 100 amp rating is at 120 v., so it would be 50 amps at 208/240 v.

I charged our i-MiEV using a small L2 EVSE (208 v. at 13 amps). I have been charging our i3 with its L1 EVSE which has been sufficient so far, but it's probably not for everyone. I am about to install a JuiceBox L2 EVSE that I will run at 208 v. and 16 amps (it will be on a 20 amp circuit). That should charge our i3 fast enough, but if not, I could upgrade our charging circuit to 40 amps (the wiring is already sufficient). Even if we charged at the i3's full power (~32 amps), we should still have sufficient excess capacity during nighttime hours when little power is being used in our apartment.

If you run power-hungry appliances in your home (electric water heater, oven, A/C), you might need to be careful charging when these appliances are on. We replaced our conventional electric water heater with a heat pump water heater, rarely turn on our A/C, and don't use our oven much, so I don't anticipate any tripped circuit breakers.

Click to expand...

Domestic service is more likely 100 amps @ 240 volts, not 208 volts.

There is absolutely no advantage to have 120 volt over 240 volt charging. It's the same amps, at double the speed, PLUS an increase in overall charging efficiency. Your car comes with a 120 volt charge cable that can use 12 amps or less (1.4kW).

If you have a 100 amp panel, I would recommend a dedicated 20 - 30 amp breaker and wiring circuit to power a 16 amp (3.8kW) to 24 amp (5.7kW) charge station (each operating at 80% of the rated circuit load).

Your electrician will have to determine if even that is possible. If not, you could double up with an existing electric appliance. An oven and dryer are typically on 30 amp circuits. Your electrician can explain methods how to do this.

For a 20 amp / 240 volt circuit, I recommend an L6-20R outlet.

For a 30 amp / 240 volt circuit, I recommend an L6-30R outlet.

For a new charge cable, I recommend the Nissan / Panasonic unit used in the 2013 and newer Nissan LEAF, which is modified by EVSEupgrade.com for the above operations.

Our company also sells the JESLA, which is more expensive than the above choice and it is already preprogrammed for 12, 16, 24 and 40 amp service.

It really depends on what your real load is on that 100A panel. Most of my bigger typical loads (dryer, stove, heat, hot water) are all gas. The two biggest loads are the central a/c and the refrigerator. I had a 30A EVSE installed and used it throughout the hottest part of the summer with no problems. If I had an electric stove, dryer, and water heater...it would have been problematic. Now, I would NOT have wanted to try a 40A or larger EVSE - it might have worked, but it would have been pushing it just too far. My inspector had no issues, nor did the electrician.

Keep in mind that if you select a unit with a plug...to pass code in the USA, you must put in a 50A receptacle and wiring and circuit breaker to it on a 30/32A device...there are NO 40A plugs, and a load like an EVSE must be run to handle 125% of the fixed load, so a 30/32A unit would need a 40A circuit if hardwired, or a 50A circuit if you use a plug. Anything less, and it technically won't pass code.

mind machine said:

Domestic service is more likely 100 amps @ 240 volts, not 208 volts.

Click to expand...

The service in our apartment is 120Y/208 v. which is common in commercial establishments and in many apartments here in Honolulu. As you say, free-standing houses typically have 120/240 v. split phase power. A downside to 120Y/208 v. power is that one wouldn't be able to charge at full i3 charger power. So if you live in an apartment, check your electric panel to determine which type of power you have. I was surprised to have only 208 v. available.

alohart said:

mind machine said:

Domestic service is more likely 100 amps @ 240 volts, not 208 volts.

Click to expand...

The service in our apartment is 120Y/208 v. which is common in commercial establishments and in many apartments here in Honolulu. As you say, free-standing houses typically have 120/240 v. split phase power. A downside to 120Y/208 v. power is that one wouldn't be able to charge at full i3 charger power. So if you live in an apartment, check your electric panel to determine which type of power you have. I was surprised to have only 208 v. available.

Click to expand...

More than one person has used a step up transformer to get 250 volts.

You'd need a bigger EVSE than 32A if your input voltage was only 208vac. The i3 can handle 7.4Kw. Power=volts*amps so 7400/208=35.6A needed. FOr practical purposes, probably a 40A unit. Now, the i3 could be both current limited as well as max power limited, and may not make full use of a larger unit...a call to BMW might clarify that. The heat generated remains about the same as it's related to the power consumed (the thing is a bit less efficient with lower voltage, and you'd really notice it if it were 120vac...not sure if 208 would be that much different than 240 in efficiency, though).

jadnashuanh said:

You'd need a bigger EVSE than 32A if your input voltage was only 208vac. The i3 can handle 7.4Kw. Power=volts*amps so 7400/208=35.6A needed. FOr practical purposes, probably a 40A unit. Now, the i3 could be both current limited as well as max power limited, and may not make full use of a larger unit...a call to BMW might clarify that. The heat generated remains about the same as it's related to the power consumed (the thing is a bit less efficient with lower voltage, and you'd really notice it if it were 120vac...not sure if 208 would be that much different than 240 in efficiency, though).

Click to expand...

Sorry, that most definitely is not how it works.

The i3 can handle 30 or 32 amps (I'm actually not sure what the max amps is, as J1772 is traditionally 30 amps, except for Tesla powered cars).

If the BMW pulls a max of 30 amps, then the max power input to the charger will be:

30a * 208v = 6.2kW (commercial voltage for North America)

30a * 240v = 7.2kW (home voltage for North America)


Also, keep in mind that since 30 amps is the typical maximum amperage at public charge stations in North America and Japan, then even if the BMW can physically pull 32 amps, it will be limited to 30 amps.

The J1772 standard as currently defined supports LOTS more current than 30A - it's 80A or 19.2Kw max currently, an there has been talk of larger, but the infrastructure seems to make more sense going to DC fast charging, rather than having to carry around a huge power supply (charger) in the vehicle. Since there are very few, if any, vehicles that can support anywhere near that rate on their Level 2 charging circuit, it's not illogical to find there are not many, if any, around. It's much easier to regulate the high current DC input to the batteries than it is to make it in the vehicle.

The EVSE announces what power it has, the vehicle adjusts itself to not overload itself or the EVSE.

jadnashuanh said:

You'd need a bigger EVSE than 32A if your input voltage was only 208vac.

Click to expand...

I've got a 60 amp JuiceBox with a 32 amp output cable, but it's on a 20 amp circuit, so I'll be charging at 16 amps, 208 v., or 3.3 kW assuming no voltage drop on my very long (~150') 8 AWG supply lines. That should be plenty fast for me. But if not, I could spend even more money on my expensive (>$3000) charging circuit to upgrade the panel fuse and circuit breakers to 40 amps and the receptacle to a 14-50P.

That's part of my problem should I want to get more power (isn't needed for the current vehicle, though). I live in a row of townhouses, and to get power into my unit, I'd have to run over 100' through five other units from the meters at the end of the row...not going to happen - trying to coordinate with 5 other owners to be home, then pay to have their basement ceilings repaired is just not worth it. I'm sure there are other people in similar circumstances. There's a good reason why the internal ac charging unit in most vehicles isn't huge: cost and weight of the unit itself, and the likelihood that it could actually be used by the typical customer. DC fast charging, done away from home is a better solution for a fast charge, should you need it IMHO.

FWIW, power = current * voltage...if you want the same power and your voltage goes down, you need more amps. My typical input voltage is 245vac, so I have a bit more power available if the car is limited to 32A (I'm not certain it is actually current limited, it certainly IS power limited). I've never seen more than about 29A going into my EVSE when the i3 is charging.

There is an internal switch in the i3 (and probably most if not all EV's) that runs the power one path if the voltage is below a certain point (such as 120 vs 240), and another if it is higher. That higher path is more efficient. You're trying to make about 400vdc, and the higher the voltage coming in means less current, less heat, and more efficiency in the ac-dc conversion process (i.e., a big DC power supply) (as above, if the voltage goes up, to get the same power, your amperage would go down which is why you tend to go higher voltage - you can use smaller wires and achieve the same power which saves material costs and weight).

JoeKirdahy said:

Is level 1 ok for most owners?

Click to expand...

To get back to the original question, I think the answer depends on how far you drive daily and how long you have to recharge.

I'm in a condo with deeded parking in a shared, multi-story, partially-underground garage. I've been working on getting a level 2 charger estimated and installed since March. Was able to take delivery when the i3 arrived in May because one of my parking spaces already had a 120v outlet next to it (and I worked out a deal to reimburse the HOA). So I've been getting by with a combination of level 1 at home and level 2 or 3 in public.

BMW says that level 1 will fully recharge the i3 in about 20 hours. While that seems like an unworkable number, it's not been an issue for me. I drive about 10 miles a day and typically leave the car parked overnight 12 to 14 hours. As long as I plug in when the gauge dips below 50%, I will be fully recharged the next morning.

Before I bought the i3, I'd assumed that I would have to have level 2 installed. Everyone from the BMW i. reps at the driving events, to the dealer staff, to the other folks here are quick to dismiss level 1 as too slow. However after having to live with it, I'm pleasantly surprised to say it's not that bad. In fact now that I've finally gotten estimates for level 2 chargers, I'm questioning whether I need to make the investment.

As I mentioned above, I started exploring the level 2 charger install in March. That's when I contacted the BMW i. partner Bosch. They referred me to three different local vendors before one would come out and perform the site inspection that leads to an estimate. The first couple refused to come out when they found out I was in a condo. Several other contractors that I contacted independently declined to provide estimates also. One notable guy made a visit but then demanded a $500 fee to generate the estimate. The Bosch estimate finally arrived in October (yes, I started the process in March) with a couple of options. The lowest cost version is $6,500.

Needless to say, I'm having a hard time rationalizing that cost given the growth of the public charging network in my area and my existing level 1 option.

To recharge at the max rate the i3 can use with a level 2 unit requires a 32A unit. Those by themselves range in price from a bit over $300 to over $1000...the differences mostly in how they look, not how they perform. But, the bigger thing is how far they have to run the fairly significant wiring (at least 8g) which can cost over $3/foot when you include the wire, in your case, probably conduit, and clamps...not counting the labor. IF it requires bigger upgrades to the service panel, you have yet more hardware and labor. SF is not an inexpensive labor market, so that probably puts it up higher than some. THen, being a condo, you certainly would need an inspection and permits (not counting the hassles of negotiation with the HOA in the first place). If they put it on a separate meter, then you'd have our own billing costs plus the cost of the electricity involved. If I was paying for it, I'd want to have a lockable switch so somebody else couldn't charge without me knowing and approving, again, adding to the overall cost.

Mine ended up costing about $1K installed in my own garage of my townhouse (also a condo). But, my panel was in my garage, so they didn't have to run the wires very far. There's a level 2 EVSE about 1/4-mile away, but I like the ability to precondition the vehicle prior to leaving, and that wants more power than the level 1 unit can provide plus, while it doesn't happen too often, if I did want to go out again and needed a charge, having it done quicker was worth the investment to me...but, at $6.5K...it wouldn't happen!

If the plug is on a 20A circuit, you could speed it up a bit by buying a bigger EVSE - a 20A circuit can handle up to a 16A EVSE (125% rule). Note, you can put a 15A receptacle on a 20A circuit, but you can't put a 20A one on a 15A circuit, and the circuit might already be 20A. What might also be possible is to see if they could switch that existing receptacle to be a 240vac one, and you'd double the current available, and again, you could use a bigger EVSE. That would only work if that receptacle was on its own circuit, but labor-wise, would be easy...change the circuit breaker, move a few wires, swap out the plug for one designed for 240vac...probably way less than an hour labor time and maybe $50 in parts for the new CB, receptacle and cover plate. Doubling the voltage would mean double the power (power = amps * voltage). The i3's charging circuits are more efficient using 240vac verses 120vac, so you get more bang for your bucks.

jadnashuanh said:

more bang for your bucks.

Click to expand...

Thanks for the advice. The issue is not electrical. The complex opened in 2002 and has a very robust power system. We've got 240v panels with over a dozen empty breakers. Even a 480v panel with unused breakers. The $6,500 quote is for a 30 amp circuit and Bosch-brand EVSE that would use the existing conduit. My current space is three floors from the electrical room; the path that the wires need to be pulled isn't exactly direct; there are multiple outlets on the circuit currently.

They also quoted a 40 amp circuit to accommodate the BMW wall box for $8,200 but I'd have to buy that EVSE separately. The real issue is construction. For seismic reasons, the garage was built with post-tension concrete slabs, which requires x-rays and core drilling for new cable runs.

We share the space with a public garage serving a supermarket and small retail center. My hope is that an operator such as NRG eVgo or even BMW i. through DriveNow (our neighborhood already is designated as a pickup/drop-off zone for the Active E fleet) will come in with public stations.

Similar to Stumble I don't find myself charging at home that much.

In 50 days of ownership I've charged at home exactly 4 times with the supplied cord.

It helps if you have DC and a fast charger close. On the way home I stopped by with 18mi on the GOM, 14 minutes later I left with 60mi. I also charge around work at the various stations and take the opportunity to charge at the grocery store or when we run errands. I live in the SF Bay Area where there are many chargers.

CA has lots more opportunities for public charging than most other places. There's exactly one CCS charger that I could find within range, and it's not in an area that I hardly ever travel to by many miles. Right now, most of the level 2 units are either at a car dealer, or public utility substations that have nothing worthwhile around to stop at while the thing charges up. SO, as a result, doing it at home is better, even if it does cost me (many of the others are free, at least for the time being). I wish we had the installed infrastructure that's around in the metro areas of CA. But, then, other than to visit, I wouldn't want to live there!

I live in a small condo complex and charge at 110v. It all depends on how much you drive and how long you are home. We usually don't drive more than 50 miles and are home at least 12 hrs so it works fine. Bit if you drove 60 and were only home 10, you'd want the 220/30a charger.

One more possibility if you're lucky...

SOmetimes, they'll run a 3-wire cable and use a common neutral fed from a 2-pole circuit breaker. If that is the case, you'd probably see black, red, white wires along with the ground in the receptacle. SOmetimes, they'll break the power tab on the receptacle, and run the black to one half and the red to the other meaning that each half is on a separate breaker - the neutral can be the same because the current essentially cancels out, and if only half is used, can never be more than one leg, so the wire size (gauge) can stay the same.

IF that is true, you would have 240vac available at the receptacle and if they'd allow, you could replace it with a 240vac, 20A plug, and double your power available.