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Re: Using I Miev for backup power unit

Posted: Thu May 19, 2016 7:41 am
by vh2q
I figure as long as I stay below the current limit on the on-board DC converter (I believe it's 80A), I can tap the car's 12V battery to power emergency circuits in the house. This yields about 1000W I think. Small surges should be possible as the battery will support several hundred amp load for short periods of time.

Adding a solar array and some additional batteries in parallel with the car's battery will make this whole thing more robust and uprate the average load to maybe 2000W and the surge as well.

The "hump" to get over is the water pressure pump that pulls water from the cistern. That's a bit of a hog at 3/4hp but it only runs for about 20 seconds at a time. The problem is the inrush current.

Re: Using I Miev for backup power unit

Posted: Thu May 19, 2016 3:19 pm
by jray3
If using the i-MiEV as backup power through a 12V inverter, I'd consider attaching the inverter to a much larger 12V battery for a buffer and jumper the i-MiEV to it, which further reduces the stress on the system. BUT, there's not much concern, as I've used the i-MiEV to charge a big dual-battery diesel that tends to go below 10V after extended storage. After over an hour of boost-charging, the only overheated component is the jumper cables!

Re: Using I Miev for backup power unit

Posted: Fri May 20, 2016 8:17 pm
by Aerowhatt
vh2q wrote:I figure as long as I stay below the current limit on the on-board DC converter (I believe it's 80A), I can tap the car's 12V battery to power emergency circuits in the house. This yields about 1000W I think. Small surges should be possible as the battery will support several hundred amp load for short periods of time.

Adding a solar array and some additional batteries in parallel with the car's battery will make this whole thing more robust and uprate the average load to maybe 2000W and the surge as well.

The "hump" to get over is the water pressure pump that pulls water from the cistern. That's a bit of a hog at 3/4hp but it only runs for about 20 seconds at a time. The problem is the inrush current.


The fuseable link to the cable going back to the DC to DC converter is right at the battery terminal. If memory serves it was a 60 amp and looked to be a slow blow variety but did not say that. To keep from adding problems during an outage stick with a 60 amp or less maximum draw from the car 12 volt system. Like others have suggested having an external battery bank that the car is connected to solves a number of issues. For high surge currents you need to have a properly sized inverter and often (with a smallish battery bank) a capacitor bank set up between the battery and inverter. The biggest issue with high start surge items is usually the supply battery voltage being pulled low enough, long enough to trip the low battery shut down on the inverter. A capacitor bank can prop the voltage up long enough to prevent this without adding a bunch more battery capacity.

Aerowhatt

Re: Using I Miev for backup power unit

Posted: Sat May 21, 2016 7:59 am
by vh2q
My inverter will support 3000W continuous, 9000W for 20 seconds. It is also a solar controller so I could do the solar trickle thing (which would also recharge the IMieV 12v battery if the ignition was off) but realistically that only makes sense if you are using solar power all the time. Using the grid to charge up after an outage is the easier solution, but that does limit the duration of the backup supply to 16 hours at 1000 Watts, so about 4 days if you are very careful and only use the power for a few hours a night.

I am thinking that the 12V battery voltage should not dip too much with the main battery "backing it up", ie with the ignition on. I just don't know how hard you can push it and for how long before the fuse blows. And I am pretty sure the fuse is 80A.

Re: Using I Miev for backup power unit

Posted: Mon Aug 08, 2016 3:53 pm
by Aerowhatt
vh2q wrote:I am thinking that the 12V battery voltage should not dip too much with the main battery "backing it up", ie with the ignition on. I just don't know how hard you can push it and for how long before the fuse blows. And I am pretty sure the fuse is 80A.


Yes according to the Schematics it's an 80 amp fuse, thanks for the correction.

The surge loads you mentioned are going to require some serious battery capacity to hold through without tripping the low voltage threshold on the inverter(s). I'm thinking about 500Ah, "trickle" charged by the iMiev through a 50 or 60 amp resettable DC circuit breaker. I've seen way to many backup systems that are pushed to close to upper limits and then when needed most, something fails. Leaving no power at all until repairs are made and expensive components replaced. Not much of a backup system if it fails when you need it most!!

For longer outages you simply must have some solar input to the batteries as well. Generators just bring your neighbors to your front door . . . extension cords in hand :roll:

Aerowhatt

Re: Using I Miev for backup power unit

Posted: Mon Aug 08, 2016 4:05 pm
by vh2q
Well we are going to find out what this big battery/little battery setup can do. I may put a second lead acid battery in parallel with the car's 12v battery to provide for some surge demand but in the final analysis the average draw has to be under 80A at 12V otherwise the dc to dc transformer won't be able to keep up.

At some point I will install a solar array (when the size shrinks to the size of a double door). But you can't charge the car direct from the solar array, at least I don't think so. You need a humungous battery bank (at least 16 batteries) to store all that power before dumping it into the vehicle. And if you have that battery bank you don't need the car battery for power backup.

The inverter low voltage threshold/alarm is around 10V if memory serves. I think it's programmable as well.

Re: Using I Miev for backup power unit

Posted: Sat Nov 05, 2016 3:44 pm
by pbui19
vh2q wrote:Well we are going to find out what this big battery/little battery setup can do. I may put a second lead acid battery in parallel with the car's 12v battery to provide for some surge demand but in the final analysis the average draw has to be under 80A at 12V otherwise the dc to dc transformer won't be able to keep up.

At some point I will install a solar array (when the size shrinks to the size of a double door). But you can't charge the car direct from the solar array, at least I don't think so. You need a humungous battery bank (at least 16 batteries) to store all that power before dumping it into the vehicle. And if you have that battery bank you don't need the car battery for power backup.

The inverter low voltage threshold/alarm is around 10V if memory serves. I think it's programmable as well.


hi vh2q - any update ? did it work out with big/little battery in parallel ? winter is approaching and we've already a few power outages.
Thanks

Re: Using I Miev for backup power unit

Posted: Thu May 17, 2018 6:49 am
by bradleydavidgood777
(2012) Mitsubishi Motors introducing MiEV Power BOX 1500 Watt Power Feeder for its EVs
http://www.greencarcongress.com/2012/03/mits-20120309.html

Lots of news in 2012 about this thing. $1800.

Re: Using I Miev for backup power unit

Posted: Thu May 17, 2018 7:29 am
by vh2q
I have it all rigged up and tested (with lights only ... and for some reason they come on and off, something to do with a load sensing feature on the inverter and the fact that most of our lights are LED) .. I have not tested it under load and have not really had a reason to. My one concern is the water pressure pump is 3/4HP and I think that's too much on startup for the dc to dc and lead acid battery in the car to handle. The inverter is quite robust, from memory 3kw surge 9kw