Cheap 'n easy plug-in Prius mod =)

uriel8

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Dec 23, 2007
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Here's my bright :idea: for stretching out the Prius gas mileage to 75 to 100 mpg without spending $8k to $24K for an aftermarket kit or job is to:

1) buy a replacement Prius NiMH battery pack from Ebay where they have them for $800 to $1100. Install it in parallel with the stock battery. Be careful and wear gloves as I've heard the car battery has nominal 220 VDC. (view inside the battery case and location)

2) Install the EV-only switch to the switch blank on the left side of the dash described and pictured here in a PDF.

Since the Prius BMS is designed to override the EV-only instruction whenever the battery falls below 80% charge, the gas engine (ICE) may try to run to recharge it. Try to handle that by installing:

3) manual ignition defeat switch on the ICE starter. I suppose that ignition failure could cause computers to shut off the EV motor, but probably not.

Alternatively, buy the aftermarket BMS replacement box from Hybrids-Plus in Boulder, CO.

Then if I know I only want to go 25 miles or less at 34 mph (the governor limit Toyota puts on the EV motor) I won't over-deplete the batteries.

Now I just need a battery charger for a 210 volt battery to plug into when I get home to plug into. Where can I get one of those?

Might work as well on pre-2004 cars just as well. Any ideas or experience here, guys?

Bob in San Diego
 
to make a good battery charger all you have to do is limit the current (and rectify) it's that simple

to charge the batteries just tap them down to a lower voltage and simply put a light bulb in series with the battery and use a rectifier to convert your 110v AC to DC. see here how i built my battery charger.
http://endless-sphere.com/forums/viewtopic.php?t=2850

just tap the battery so that the volts when fully charged don't exceed your AC voltage. don't charge them in parallel without seperate light bulbs between charger and battery.
 
Hello bob and welcome here!

I'm glad that we could have a Prius electric owner here!

For your charger, you need a cc cv mode. It will charge to a constant pre-seted and limited current until it reach the 210V. When that occur, the current will drop as the final stage of charge is accomplished.

You could use a 120 to 240 V transformer that you open and remove some wires turns to get 210V after it is converted from ac to dc with the bridge rectifier .. cost around 100$ for a 1000W transformer

Doc
 
Your ideas are good but I doubt they could be implemented w/o a lot more work. For one thing the battery pack is only good for a mile or so in EV mode using stock software, so two packs won't extend range that much (they're only 1.3 kwh nominal). The ICE is spun to the appropriate speed by the CVT and various MG sets before being fired off, not a standard starter. I've thought about this idea too and have decided it's better to plan for the day when plug-in kits drop in price. FYI, the car will go 41-42 mph before the ICE cuts in. It will actually spin the ICE w/o firing it at higher speeds. This is to limit the speed of one of the electric motors.

I keep waiting for someone to take a wrecked Prius and do a regular EV conversion but tapping into the stock drivetrain seems pretty hard to do. I suspect you'd have to change the entire drivetrain... A lot of people use Manzanita Micro's chargers; they're adjustable for a larger range of conditions. http://www.manzanitamicro.com/
 
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