I was curious if anyone has came up with a charger for their HV battery pack yet? Seems that it would be a pretty simple device and I wonder why there are so few for the dealers. I haven't got to look at schematics, but from what I've read in the posts the HV batteries are disconnected when the car is powered down. If so couldn't you make a full wave rectifier for a 240 volt AC plug that puts out a low current for charging? I know it's a 255 volt battery pack, but 240 volt seems close to the 90% charge where it's supposed to charge up to. I wouldn't even need anything fancy, a timer could turn it on and off so there isn't anything too sophisticated.

I know I could benefit from a charger. I drive about 23 miles to and from work and the last three miles when I get home depletes the battery's charge. If I could start off fresh each morning it would definitely help my mileage. I've already installed an engine heater to help out this winter.

 

Don't even think about building a simple charger for NiMH batteries. You need to monitor and control the charging current during the cycle and not overcharge (the TCH never fully charges the battery so as to preserve its life).

Also, 240 VAC actually produces 339 volts on its peaks, which without some intelligent current limiting will toast the battery. And the battery output voltage is not proportional to it's charge (this would be true for a capacitor), but is quite flat over most of its range.

 

I think your charging idea is what some company is doing in Austin, Texas. They do this for the Prius. I thought I read they change out the original batteries, modify the ECU and fix up a plug in charger. It's costly though but some are getting over 100 mpg with this change.

I had thought about a charger that could take the batteries to about 80% charge. The batteries are designed for a quick charge. A charger that would bring the batteries up with a 12 hours charge should work. I would feel more comfortable monitoring the HV batteries for a month or more to read the max, minimum dc volts.

I started messing with nickel hydrid batteries when they first came out about 15 years ago. No memory and they had lots more ma than the nicads. I used them in my pylon model plane. I remember when I stopped flying the new quick charge hydrids (NiMh) were available. The batteries in our cars are hydrids specially designed just for hybrid use.

In the EV Mode the batteries seem to go farther if you drive 25 miles per hour (using cruise) instead of 40 miles per hour. Not many places you can maintain that slow speed for any length of time without getting run over.

 

I didn't know that these batteries had a flat voltage output. I had assumed they fluctuated like a AA battery and would drop. I don't know, maybe that's when they drop below 50% charge.

I think I could figure out how to make the correct voltage from AC. I'd never heard of 240 volts being 339, but that could be it's peak without taking the RMS average? Originally I was talking to my brother (an electrician) about a 110 volt charger, upping the voltage through a transformer donated from one of the old tube radios that I work on. I figured I'd watch the voltages over some time (if I ever got to it), then essentially would build a trickle charger for overnight.

Anyway, I was just wondering if anyone had built anything that could just work with the batteries we already have. If it's cheap enough, works without damaging the car, and can add another few tenths of a mpg I'd be interested.

 

The voltage does drop, but it isn't linear -- 80% charge isn't 80% voltage.

240 volts is the RMS voltage, the peak voltage is larger by the square root of two.

I wouldn't recommend this because any mistake and you could have a fire, electric shock, or destroy the battery. It also would certainly void the warranty. The battery capacity isn't that large anyway so there wouldn't be that much of a savings, especially considering the risks.

 

The "charger" would be the easy part, it's the charge monitor that would be hard, probably a) very expensive and b) still might be almost impossible.

Jack your car up when you part and and spin your front tires so it thinks it's going down hill. That should work and be easier.

Later!

Dang

 

I noticed it only takes 2 or 3 miles of driving to get a nice charge on the HV batteries. Double those miles should give you a full charge.

Evidently the ECU carefully monitors the battery voltage.

I also feel it would be an advantage to charge the batteries manually overnight. That way you would not be charging the batteries with a cold engine for that next morning drive to work.

 

Hmmmmm......making the car think it's going down hill. That'd probably work, but I don't think I have a big enough garage to pull it off.

No really I was looking at this car like it has great upgrade potential and someday someone is going to figure out the charger. Hopefully by the time my battery pack dies they'll have some nice lithium upgrade, but I'm not counting on a car company to help me there (they like to sell cars). Unfortunately I live in a state where I only have a 7 year/100,000 mile warranty on my car, and that's because I paid extra for it. So far I've gone about 13,500 miles in just under nine months, so the end is coming fast.

I figure a lot of people could benefit from the charger, not just me. By the time my car is warmed up in the morning (maybe a mile) my car is generally still charging. When I get a good charge on the HV battery again I'm to the edge of town and about ready to hit the highway. After I hit the highway, that's it for using the batteries and they don't do me much good until the return trip when I drop back to 35 in town. It just would be nice to have a good charge in the morning (and it would help emissions since the car tries to run on batteries while the engine warms).

 

It could be worse, I have 36,700 miles on mine today, and I got it a couple days over 11 months ago. So that means in 4 more years I should have over 200,000 miles on it. I would love an upgraded battery and the ability to both run in electric mode only as well as charge the battery.

Hopefully, one of the companies will decide there are enought TCHs out there to make an upgrade for it. if not, I would just trade it in on a newer model that has those capabilities. I feel fairly confident that they will have them in 4 years time.

But for the time being, I have no reason to think the battery won't last 200,000 miles.

 

Yeah the Prius plug-in kits I've heard of (which do void the warranty but are available) add a bunch more batteries as well as the plug-in capability, to give a lot more charging capacity and EV mode driving. Here's some info.