144 VDC to 120 VAC affordable conversion

[crx_rogus]

Folks -

Thinking of how my Insight might be able to help with winter power outages, should they occur, with enough available power to reliably run the fridge and whatever else, other than feeding ATX switching computer power supplies direct HV DC and getting 12V max out, has anyone come across any affordable invertors? Technically, I suppose there might be a way to modify a 12VDC->120VAC invertor for that purpose, but I don't know enough about them to do that.

I wouldn't be surprised if it's far more affordable to convert the Insight's DC-DC's 12VDC out to 120VAC. Since a DC regulator followed by a high-power oscillator are technically all that's needed (but simple square waves to a fridge is a likely unhappy thing), it seems at least, just in talking out my neck, that it could, perhaps, be a relatively simple thing... while talking out my neck at least.

[IamIan]

Originally Posted by crx_rogus

Folks -

Thinking of how my Insight might be able to help with winter power outages, should they occur, with enough available power to reliably run the fridge and whatever else, other than feeding ATX switching computer power supplies direct HV DC and getting 12V max out, has anyone come across any affordable invertors? Technically, I suppose there might be a way to modify a 12VDC->120VAC invertor for that purpose, but I don't know enough about them to do that.

I wouldn't be surprised if it's far more affordable to convert the Insight's DC-DC's 12VDC out to 120VAC. Since a DC regulator followed by a high-power oscillator are technically all that's needed (but simple square waves to a fridge is a likely unhappy thing), it seems at least, just in talking out my neck, that it could, perhaps, be a relatively simple thing... while talking out my neck at least.

Quality work gets complicated fast... so the basics are simple but the details in application can get complicated fast.

But a few basic ideas:

#1>
Most 12VDC to 120VAC inverters you can buy operate in stages... the first stage is usually a DC-DC step up that brings the 12VDC up to about ~160VDC... then a second stage inverts that ~160VDC into ~120VAC... it is not very difficult to apply your own HVDC directly to that inverting stage and bypass the DC-DC step up stage... The IMA HVDC battery can put out up to ~10kW of power... which is more than most houses will use at any one time... although by itself it can't keep that up for very long at all.

#2>
Install a DC keep alive switch... although you incur the losses of running the OEM DC-DC converter ... this could allow you to use the 144VDC IMA battery to keep the 12V battery charged while your conventional 12VDC to 120VAC alternator did its job from the 12VDC supply... The OEM DC-DC alternator function can not put out as much kW of power as the main traction battery does... So constant power would be more limited.

#3>
The IMA motor already supplies AC power... a variable transformer could allow you to convert it to any output VAC you want... frequency control and steady stable power output can be tricky.... The IMA motor requires the gasoline engine to be running .... and its max power output is ~5kW of generator action... which is about 1/2 of the peak the IMA battery pack can put out... but the gasoline lets it put it out for much longer.

#4>
The MDM already takes the HVDC from the 144V battery pack and converts it to AC to drive the IMA motor... but it would not be easy to try and reliably get it to put out 120VAC 60hz for household use.

#5>
Just run a normal 12VDC to 120VAC invertor and just idle the engine to let the stock system take care of the DC-DC alternator action to keep the automotive 12VDC charged up enough to power the 12VDC to 120VAC alternator

[MN Driver]

How long are you going to be able to run your fridge for though? You have less than a kWh of power to work with, so you'd have to have your car on to keep some charge flowing into it. On top of that, your battery probably wouldn't be fully charged to begin with and draining it too low could be a bad situation.

If I wanted to pull power, I'd feel safest tapping the 12 volt battery directly with the car idling but there are limits to how much power you can pull and motor start loads for a fridge might be tough without a pretty strong invertor if you don't already have one capable of it.

[Mike Dabrowski 2000]

the IMA motor is a 3 phase generator that is always producing voltage when the ICE is running. Tapping two phase lines will produce single phase AC power at an rpm variable frequency.
In our hybrid training classes we tap the motor and connect it to some 1500W halogen shop lights to demonstrate this. I dont recall the frequency, but seem to remember that it is close enough to work 60HZ equipment.Rev the engine, and you can see over 200VAC, which has caused us to blow up several shop lights.

A more efficient system would be to use a 3 phase bridge rectifier on the three phases to generate HV DC, which could be fed to the HV buss of a 12V to 120V inverter. (after the step up from 12 to 160VDC. See Ians #1)
Just another project on my list.