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Hi there,
I found little information about this topic on internet (actually none on MDX although some on Prius) so I figured I'd start a thread to share my experience as well as getting feedback from you guys.
I bought my MDX Hybrid a little over a year ago, and loved it. In fact I loved it so much I bought another, albeit regular MDX, for my wife.
A few weeks ago there was a wicked storm and we lost power for more than 2 days. I happened to have a 300W inverter so I plugged it into the cigarette lighter and it powered up our WiFi router and kid's TV, plus some lights, effortlessly. That got me thinking, why not use my hybrid as an emergency generator? Being an electric engineer by training, I had a vague idea that hybrid had a generator instead of alternator.
After the storm I started researching in earnest. I found stories about Prius owners powering their houses in storms, and a NY Times story called it V2G (Vehicle to Grid). I could attest to many of the benefits mentioned in the stories. It's super quiet. My neighbor across the street 100 yards from us had a gas-powered generator that we could hear with windows closed, yet our hybrid barely made a whisper from our own backyard. The engine only comes on when it needs to like only a hybrid could do. Not to mention the convenience and low cost.
The only question that stumped me was exactly how much power (watts, or amps) I could draw. The whole car industry was hush hush about it and the last paragraph of the NY Times story might have explained why. A spokesman from - none other - Honda didn't like the idea and suggested to buy a generator, which Honda happened to have a decent lineup.
Apparently adventurous Prius owners took to themselves to solve the mystery. While most people limited the power to around 1KW and the NY Times story claimed at least 3KW was available, this dedicated researcher dug deeper and believed there should be 5~6KW. Accidentally I took a similar approach to do my research before I saw his work. Like him I started with information I had. I knew the three electric motors totaled to around 90KW, so it seemed reasonable to assume the generator had the capacity of that range. The DC-to-DC Converter would be the bottleneck. I found the main fuse in the engine compartment to be 200A (and regular MDX is 150A). Although I couldn't figure out if that was the converter fuse or out of the 12V battery, I thought anything lower than that would sure be safe.
So I had an inlet box and interlock switch installed on my house for the prospect power generator. I chose 30A wire and inlet box for up to 7.5KW. Then I bought a 4KW continuous / 16KW peak pure sine split phase power inverter for $289 plus taxes from eBay. There were other more expensive choices, but this worked perfectly for me. I chose 4KW even though I didn't expect to draw that much power because it costed only $70 more than the 2KW one, and so I'd have more head room if I wanted to go higher.
![115297]()
And a clamp meter, a twist lock connector for 120/240VAC, 1/0 AWG battery cables with connectors, and a series of 100A, 150A, 200A, and 300A in-line circuit breakers from Amazon.
Hooking up the battery cables was fairly easy and the rest of my experiment went like this:
I first tried the 100A breaker and a hair dryer for load. The breaker would trip when it was around 60 amps. Hooking up to the house had similar results. I decided the breaker was faulty and 100A was too low for me anyway.
I switched to the 150A breaker and it worked well. Using hair dryer I managed to go up to 148A and stayed there until I went one notch higher.
![115291]()
Satisfied, I hooked up to the house and started a 3-hour test run. I increased the load gradually by turning on more breakers, and eventually stayed at around 1KW with all what I considered essentials (lots of lights, refrigerator, furnace blower, WiFi router, TVs, stereo blasting music, etc.), and was able to also handle range hood and garage door, each costed about 200W, until I decided to run dish washer at the end.
![115295]()
During the 3 hours both the car and the inverter seemed to work effortlessly. The inverter occasionally turned on the fan but stayed cool to the touch. The 12V battery was cool initially for a long while, only got warm from the engine when it ran more often. The engine came on occasionally like I saw before, only this time I clocked how long it ran and how often. When there was no load, it ran 75s every 12 minutes, and at about 1KW load, it ran 75s every 270s. So the load made a difference, which makes sense. It came on when the battery gauge got to certain level, which also proved the 12v was charged by the main battery.
I also measured the battery voltage from beginning to end. It started around 12.46v, and stayed around 12.4v 'til the end. My conclusion from that was, the engine/DC-to-DC converter was able to keep up by running only 75/270 of the time. In other words, if the engine were to run continuously, it should output about 3.6KW. It might even be able to go higher if the engine could throttle. A few factors might change that equation though. First, the converter might overheat if run continuously, which I thought was unlikely since it's liquid cooled. Second, the 12V battery might not be able to handle the higher amps output, again unlikely since in that scenario the current would be directly drawn from the converter instead.
That's where I am now. I'm hesitating to continue with higher amp since I don't want to risk anything more than I had to, and 1.8KW seemed plenty enough for me.
So what do you guys think?
Oh something I thought interesting I saw. At the beginning of the 3-hour, I saw the 12V battery being charged by the main battery when the engine was off (because the voltage I measured was 14.4v), but afterwards it would not seem so when the engine was off (voltage measured at 12.4v). I don't know what to make of that. It seems to be drawing current because the battery gauge was going down slowly. So perhaps it's charging at a lower voltage when engine was off?
I found little information about this topic on internet (actually none on MDX although some on Prius) so I figured I'd start a thread to share my experience as well as getting feedback from you guys.
I bought my MDX Hybrid a little over a year ago, and loved it. In fact I loved it so much I bought another, albeit regular MDX, for my wife.
A few weeks ago there was a wicked storm and we lost power for more than 2 days. I happened to have a 300W inverter so I plugged it into the cigarette lighter and it powered up our WiFi router and kid's TV, plus some lights, effortlessly. That got me thinking, why not use my hybrid as an emergency generator? Being an electric engineer by training, I had a vague idea that hybrid had a generator instead of alternator.
After the storm I started researching in earnest. I found stories about Prius owners powering their houses in storms, and a NY Times story called it V2G (Vehicle to Grid). I could attest to many of the benefits mentioned in the stories. It's super quiet. My neighbor across the street 100 yards from us had a gas-powered generator that we could hear with windows closed, yet our hybrid barely made a whisper from our own backyard. The engine only comes on when it needs to like only a hybrid could do. Not to mention the convenience and low cost.
The only question that stumped me was exactly how much power (watts, or amps) I could draw. The whole car industry was hush hush about it and the last paragraph of the NY Times story might have explained why. A spokesman from - none other - Honda didn't like the idea and suggested to buy a generator, which Honda happened to have a decent lineup.
Apparently adventurous Prius owners took to themselves to solve the mystery. While most people limited the power to around 1KW and the NY Times story claimed at least 3KW was available, this dedicated researcher dug deeper and believed there should be 5~6KW. Accidentally I took a similar approach to do my research before I saw his work. Like him I started with information I had. I knew the three electric motors totaled to around 90KW, so it seemed reasonable to assume the generator had the capacity of that range. The DC-to-DC Converter would be the bottleneck. I found the main fuse in the engine compartment to be 200A (and regular MDX is 150A). Although I couldn't figure out if that was the converter fuse or out of the 12V battery, I thought anything lower than that would sure be safe.
So I had an inlet box and interlock switch installed on my house for the prospect power generator. I chose 30A wire and inlet box for up to 7.5KW. Then I bought a 4KW continuous / 16KW peak pure sine split phase power inverter for $289 plus taxes from eBay. There were other more expensive choices, but this worked perfectly for me. I chose 4KW even though I didn't expect to draw that much power because it costed only $70 more than the 2KW one, and so I'd have more head room if I wanted to go higher.
And a clamp meter, a twist lock connector for 120/240VAC, 1/0 AWG battery cables with connectors, and a series of 100A, 150A, 200A, and 300A in-line circuit breakers from Amazon.
Hooking up the battery cables was fairly easy and the rest of my experiment went like this:
I first tried the 100A breaker and a hair dryer for load. The breaker would trip when it was around 60 amps. Hooking up to the house had similar results. I decided the breaker was faulty and 100A was too low for me anyway.
I switched to the 150A breaker and it worked well. Using hair dryer I managed to go up to 148A and stayed there until I went one notch higher.
Satisfied, I hooked up to the house and started a 3-hour test run. I increased the load gradually by turning on more breakers, and eventually stayed at around 1KW with all what I considered essentials (lots of lights, refrigerator, furnace blower, WiFi router, TVs, stereo blasting music, etc.), and was able to also handle range hood and garage door, each costed about 200W, until I decided to run dish washer at the end.
During the 3 hours both the car and the inverter seemed to work effortlessly. The inverter occasionally turned on the fan but stayed cool to the touch. The 12V battery was cool initially for a long while, only got warm from the engine when it ran more often. The engine came on occasionally like I saw before, only this time I clocked how long it ran and how often. When there was no load, it ran 75s every 12 minutes, and at about 1KW load, it ran 75s every 270s. So the load made a difference, which makes sense. It came on when the battery gauge got to certain level, which also proved the 12v was charged by the main battery.
I also measured the battery voltage from beginning to end. It started around 12.46v, and stayed around 12.4v 'til the end. My conclusion from that was, the engine/DC-to-DC converter was able to keep up by running only 75/270 of the time. In other words, if the engine were to run continuously, it should output about 3.6KW. It might even be able to go higher if the engine could throttle. A few factors might change that equation though. First, the converter might overheat if run continuously, which I thought was unlikely since it's liquid cooled. Second, the 12V battery might not be able to handle the higher amps output, again unlikely since in that scenario the current would be directly drawn from the converter instead.
That's where I am now. I'm hesitating to continue with higher amp since I don't want to risk anything more than I had to, and 1.8KW seemed plenty enough for me.
So what do you guys think?
Oh something I thought interesting I saw. At the beginning of the 3-hour, I saw the 12V battery being charged by the main battery when the engine was off (because the voltage I measured was 14.4v), but afterwards it would not seem so when the engine was off (voltage measured at 12.4v). I don't know what to make of that. It seems to be drawing current because the battery gauge was going down slowly. So perhaps it's charging at a lower voltage when engine was off?
I did take a bit of a risk but was far from being reckless. I think I know why you thought so though. I should have mentioned most of my amps were on DV 12V. I did have photos of the 150A breaker on the positive terminal, and the clamp meter on the thick battery cable. So 12v x 150a = 1.8KW. My inverter was 110/220vac split phase, so that translates to ~8A on the AC end. I had purposely installed a 15A breaker in my house panel in case the DC breaker failed I'd still be limited to only 3.3KW. Other than these, I was careful to first test with a hair dryer, then on the house, gradually increasing the load in both cases, and monitoring what I thought could be problems. My big assumption was the converter had to have some sort of mechanism to protect from being overdrawn. So what could happen was the battery couldn't be charged fast enough, resulting in a depleted battery, which was a risk I could take. Another worse scenario was the battery couldn't handle that much output and would overheat and explode. Unlikely because I knew Prius 12V batteries were smaller, and mine was rated CCA 620A, which meant it could output 620A for 30 seconds for cranking. I kept monitoring that nonetheless in the 3-hour run. For all I could tell, it went really well.
