110V Super Charger Idea. Need Electrical Engineer input.

[littlefreak3000]

I live in an apartment so I don't have a 220V outlet option available to me. As an engineer (Software) I having been playing around with ideas in my head on how I could get a 220V charger using only a 110V. Of course their is the option of taking two 110s that are on different phases but that's messy and would leave me with wires all over my apartment. So then I started thing about a solution using a battery. What if you had a 110V charge batteries enough so that when the batteries are used in tandem with a 110v line that it could provide a 220V line with to charge a bike.

So while the bike isn't charging the batteries would get charged then when a bike is plugged in the batteries then provide 110v in parallel with the outlet that charged them providing 110v. It be like having your own mini supercharger station.

Now there are few things unknown to me. First is how much battery power would be required to do this? Is it too much to be feasible? What is the efficiency of the batteries? Are you going to be wasting energy to keep the batteries charged in-between bike charges? Can a battery provide enough power quick enough to keep up with the 110V line without burning up?

I know from the demographic post we have some EEs on the forums and I thought it be a fun idea to discuss.

[protomech]

If you have two 110V circuits that are out of phase, combining them for one 220V circuit is your best option. Of course, then you need to also source an 220V EVSE. Yes, wiring will be a little messy but it's better than the alternative.

Here's a UL-listed device that does this.
http://www.quick220.com/-A220-15D.html

You might also consider how much you really, really need 240V charging at home. This will effectively double your charge rate, but even a cheap 240V EVSE will cost about $400 (JuiceBox, Clipper Creek LCS-20) plus $200 for the quick 220.

Now there are few things unknown to me. First is how much battery power would be required to do this? Is it too much to be feasible?

To do it like you would describe you would need a few kWh of battery storage, the batteries would need to be able to supply around 2 kW continuous, then you'd need a large inverter for 120V AC output, battery charger for the battery system (to charge it back up), and then you'd still need the quick220 device described above.

I hope you see why, leaving the expense aside, you're not going to be saving wiring..

What is the efficiency of the batteries?

Around 70-80%, full trip (charger into SC battery into inverter). Not great.

Are you going to be wasting energy to keep the batteries charged in-between bike charges?

Yes, a little.

Can a battery provide enough power quick enough to keep up with the 110V line without burning up?

Yes, if it is large enough or powerful enough. Bear in mind you're probably talking about $5000-8000 for this system in order to save running one cable into an additional 110V circuit.

I know from the demographic post we have some EEs on the forums and I thought it be a fun idea to discuss.

If I see an EE I'll send him your way..

[littlefreak3000]

Thanks for the response. I did figure from the start it would be expensive no matter what. The other option is make a battery storage that can provide a direct DC charge like a Tesla super charger. Maybe it would only be worth it if you had a solar set up to maintain the system like Tesla does.

[protomech]

Yes. Solar-backed direct DC-DC charging would be quite a bit more efficient.

Tesla can configure their superchargers like you describe, i.e. charging a battery from lower power grid AC, that can supply higher power DC for a short period of time to charge cars as they arrive.

They do this for a couple of reasons:

1. Some utilities don't like to see wildly fluctuating power demand, especially when they have to install substations to handle peak load. I imagine it depends on the utility, but Tesla could be hit with significant ($$$) charges. Using batteries as an intermediate level to buffer demand will help smooth out Tesla's power demand most of the time.

2. In some locations, it may not be possible to have sufficient high-powered grid connections installed. This is the best analogy to your 110-only apartment. Battery storage lets them burst to higher discharge rates, at least for short periods.

3. Local energy storage allows them to store and then dispense energy from solar or wind, giving them the option of going grid-free or grid-assisted. In practice the amount of solar needed would be immense - a single SC bay would require power from ~130 bays worth of overhead solar canopies - but this may be solved in time, i.e. large solar arrays installed off-site or etc.

Tesla can also spend far more money designing, building, and maintaining their storage-assisted supercharging facilities than you are, i.e. 2-3x the cost of the vehicle. That makes some sense for Tesla. One set of charging stations can support hundreds of vehicles: ~25k Model S sold in US so far, ~100 charging stations = 250:1. It doesn't make as much sense to build a battery-backed charging station for a single vehicle.

[Chocula]

If you have an electric range or dryer, you may be able to tap the line for those.  You might need to make sure you don't use both at the same time.  If you have access to the electrical panel, you could have your electrician convert one of your circuits to 220 volts.  This is actually pretty trivial and won't require new wires to be pulled unless you need to increase the amperage which would only provide a minimal increase in your charge rate, but would significantly expand your choice of EVSE.  Ideally you would find a circuit with only one outlet like the ones for garbage disposals and dishwashers.  The drawback to this is that the entire circuit gets converted to 220 and while many electronics can run on either 110 or 220, not everything can.  You would also want to change any outlets on that circuit to prevent anyone from accidentally plugging in a 110 device.

I charged my car off 110 for a few months before I was able to get the 220 EVSE installed.  Not really a problem, but it is nice having it charge quicker.

Good luck,
Chocula