Welcome to my J.A.M. (Just Ask Mike) Session, a weekly column where I answer your basic electrical questions. If you’re a newbie who’s never plugged in a shore power cord (or ask – what’s a shore power cord?), or wonder why your daughter’s hair dryer keeps tripping the circuit breaker, this column is for you. Send your questions to Mike Sokol at mike (at) noshockzone.org with the subject line – JAM. Today I discuss recharging an EV from a portable generator.
Dear Mike,
OK. I’ve seen the joke. Is it possible? Recently I saw the picture of an electric car with a generator plugged into the car, supposedly getting a recharge on the side of the road. Can this be done? It must be a custom connection on the little generator. Will it work or can it work in a pinch?
I know it’s a silly question that defeats the zero emissions concept. But, let’s ask Mike… —Ken
Dear Ken,
I’ve already tested this possibility, run the calculations and find that it’s an impractical solution at best. A Level-1 EV charger pulling 16 amps at 120 volts from a 2,000-watt generator can recharge an electric vehicle (EV) at a rate of around 1.9 kWH per hour of running. If your EV gets 3.5 miles range per kWh of battery charge that means you’ll only add around 6 miles of range per hour of generator run time.
Recharging an EV from a generator is not practical
Want to completely charge an EV with a 75kWh battery from 0 to 100% range? That will take at least 40 hours of generator running time and refilling it with gasoline at least 6 or 8 times. It’s just not practical.
What’s really funny is that wth some of the portable lithium battery “solar generators,” manufacturers show that you can use them to recharge by day on the side of the road, like dumping in a can of gasoline.
For example, I have a Jackery 1500 which has 1,500 watt-hrs (or 1.5 kWh) of storage capacity. Even if it was 100% efficient in transferring all of its energy to an EV on the side of the road (yes, you can plug your EV into it), at best it might be able to give your EV 5 or 6 miles of range after an hour or two plugging in.
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Even with a Jackery it’s not practical
Note that I also have four 100-watt solar panels for the Jackery, which can completely recharge it in a full day of sunlight. So, in effect, you could recharge the Jackery every day while adding maybe 5 miles range. In 30 days, that would give your EV maybe 150 miles of range.
Now, if you were in a Zombie Apocalypse situation (and had a few months to wait), you could completely recharge your getaway RoadWarrior EV. But these would need to be really slow Zombies for this to work, since sitting in the same spot for 60 days is sure to attract some attention. Yes, that’s me taking a break from fighting Zombies.
OK, everyone. Remember that electricity is a useful and powerful force, so we all need to pay attention to safety precautions while using it.
Let’s play safe out there….
Send your questions to me at my new RVelectricity forum here.
Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
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I’m now proposing a study of campground infrastructure to determine how much power is needed to recharge an EV tow vehicle, an EV self-powered trailer with traction motors in the wheels, plus an RV’s normal electric requirements such as air conditioners, electric water heaters, lighting, etc… This data would be included in the 2026 National Electrical Code for campground power calculations.
I saw a clip of a Ford F-150 Hybrid Truck’s Pro Power Onboard Generator. Hooked up to a Tesla recharging it enough so the Tesla could make it to a charging station.
I’ve done this myself. Using the F-150 PowerBoost Hybrid on board generator you mentioned to charge a Volkswagen ID.4 EV I was able to add around 25 miles of range in an hour of generator time. Not horrible, but still pretty slow. Look for my upcoming article on the SparkCharge Roadie portable battery pack which can add over 15 miles of EV range in 15 minutes of charging time.
I know that a standard wet cell battery fully charged if connected partially discharged wet cell battery the two batteries will equalize in SOC like two columns of water will equalize. The question, does LI batteries act the same way? If you connect two LI batteries together in parallel with one at 50% SOC and the one at 100% SOC would they equalize at 75%? Just curious.
Li-Ion and LiFePo batteries have a Battery Management System to determine charge. They do not allow battery to battery discharge is my experience. The battery management system is connected to X number of cells and measures the overall charge of that bank of cells, When they are charged, the BMS stops the charging process. The overall charge meter for a system would take all of the banks and average them together to show you total battery system capacity.
Mike can correct me if I’m wrong but that’s my experience with most Li-Ion BMS systems.
Don’t all EV owners secretly carry a generator in their trunks?
They better, every once in a while you’ll still see someone out of gas, that tells me in the great EV world you’ll still see people standing beside their EV with an extension cord in their hand. Lol
Range anxiety is real. A relative of mine has a Tesla and he rarely let’s it get below 100 miles of range. I also see him driving his Toyota Tacoma a lot 😉
Quite telling.
Refueling, especially at an isolated spot, will be the Achillies tendon of the EV. Can you imagine trying to escape a hurricane in Miami, heading North, and needing refueling in Jacksonville. Not going to happen.
Can you imagine escaping a hurricane in a petrol vehicle and realize you only have a quarter tank and the power is out in Jacksonville so the pumps don’t work…not going to happen.
Anyone with half a brain who lives/visits hurricane territory, and hears about an approaching storm (a few days notice, normally) will fill their petrol vehicle, and keep their EV plugged-in. So, assuming both leave town with a full tank/charge, it will be much faster to refuel on the road. And, if Jacksonville has no power, someone running petrol can go much further to get fuel (assuming they don’t run down to fumes) than an EV can.
It is also a state law in Florida that gasoline stations must have a generator to keep the gas pumps running, even if the building does not.
That’s why I always filled my tank before setting up in camp, just in case the word of an approaching hurricane was reported I could break camp in less than an hour and drive 425 miles before needing fuel. I would never wait until they said mandatory evacuations.
What RV are you driving or towing that has a 425 mile range on a single tank of gas or diesel? I’m working on a few projects with self-powered EV trailers that could allow up to 400 miles of range while towing with an EV truck. Of course, that’s marketing numbers they’re telling me, so I want to see this for myself. With any luck I’ll get to experiment with it this summer.
Hi, Mike. Here’s part of a previous comment from Bob p: “2018 Nissan Frontier pulling a 23’ TT at 62 mph and getting 9.1 except in FL it gets 10.2.” 😀 –Diane
Just remember Mike that when you dump a jerry can into your car you’re not trying to fill it, just get to the nearest station. I’m sure that’s all you would do.
That’s true…. and 2 gallons of emergency gasoline is probably good for 40 to 60 miles of range (depending on what you’re driving). But I’m studying this concept of emergency charging for companies such as AAA member service centers. I hate the idea of sending a tow truck to pick up your EV with a dead battery by the side of the road. And what about the I-95 winter shutdown near Washington DC a few months ago with drivers stuck for 24 hours or more? While EV’s with heat pumps can easily keep you warm for in excess of 24 hours if you started with a decent charge, how would roadside emergency services deal with dozens or hundreds of stranded EVs in the future? We need to ask those questions now in order to get the appropriate infrastructure in place.
This is why I say liberals can come up with a lot of ideas, but they never think them through and ask the “what ifs”. EVs are great commuter cars, great for average everyday drivers, even short trips, but what if this happens, or that happens. The infrastructure is not ready for massive EVs. How long did it take for ICE before the infrastructure was in place for extended long trips. I’m not sure about the numbers, but I believe the model T was invented in 1908 and it was in the late 1930s to early 40s before people was traveling across the country. That’s 25-30 years, how long has EVs becoming popular? When the power companies start spending billions to upgrade the infrastructure, I’ll think about it unless I’m dead by then, I’m 79 now. Lol
Hey Bob p, I’m a wee bit to the left one might say, but I like to think things through as much as possible. I try my best to avoid generalizations like yours, but I get what you’re saying for sure. We left leaning folks get all excited about some new technology and off we go to the RV lot to by an electric RV (only to be told they don’t exist yet).
On the technology front, you’re right, anyone who purchases/makes/commissions an electric RV right now, today, is a bit of a risk taker and a pioneer. Will they get stuck someplace?? Maybe. but I do know that they will have to plan carefully to get where they are going. Now an electric assist trailer is a different beast and an easier bet to make work today.
Also, I’m not sure you can compare the rollout of infrastructure from the early 20th century to today. Our technologies and understanding of logistics has improved dramatically since then. We already have an electrical grid to charge vehicles, it’s the on the ground infrastructure that needs to fall inline. And to be fair, you can recharge an EV with a 110v line, as long as you’ve got a couple of days. Solar may be an option for an extended stay and if you don’t have tree cover, but it’s not fast by any means. New battery tech is coming… but it’s just not quite here yet. (graphene-ion batteries is what I’m talking about. Still a few years away)
So my analysis of the current RV/EV industry says you’re right about electric RVs today, and you’re also too pessimistic about Electric RVs and charging infrastructure 5-7 years into the future.
Before you make a public assertion about half the population of America, maybe you should rethink what you have to say at, “I’m not sure” and stop right there.
As a double retiree (Navy and Telecom company) technology can change overnight. A few years ago, AOL was cutting edge – one of the last jobs I did was install a 10GB fiber pipe to a cellular site for 5G data service. One other point – Medical technology has advanced so much that it will likely allow you many more years on this side of the dirt.
But that scenario is a red herring, Mike. There were several EV’s (Teslas, and a Nissan Leaf from what I read) and not one of them had run out of juice. There were numerous gas powered cars that ran dry. As L3 charging stations are added, and Tesla opens up its ‘SuperCharger’ network to other companies, range ‘anxiety’ will disappear, just as people used to mock those in the ‘horseless carriage’ about not being able to get gasoline if they venture to far from home.