PHEV prius plans?

[MetroMPG]

hey krousdb, have you considered taking the PHEV route for your prius, either with an aftermarket kit (EDrive/Hymotion) or do-it-yourself? know any owners who are seriously considering this?

just curious.

[krousdb]

Originally Posted by MetroMPG

hey krousdb, have you considered taking the PHEV route for your prius, either with an aftermarket kit (EDrive/Hymotion) or do-it-yourself? know any owners who are seriously considering this?

just curious.

Hey metro, been there, done that. In the summer of 2004 I constructed six 201.6V nominal NiMH battery packs, 3Ah each placed in parallel with the 6.5Ah OEM pack (24.5 Ah total). I ran a number of experiments to see if there was a benefit to having 4X the OEM capacity without grid charging. But since all of the batteries were under the control of the Prius battery ecu, the additional capacity had the same 40-80% SOC limitations. The testing showed no advantage in the additional capacity. EV distance did increase from 1.5 miles to 4 miles, limited of course by the 40% SOC minimum.

So in the spring of 2005 I finally came up with a grid charger design that would work on a standard 120V outlet. Basically step down transformers in reverse, 1000W total. I used bridge rectifiers for conversion to DC. Long story short, the charger worked and i was able to squeeze 2kwh into the batteries at a time. But 2kwh doesn't do much on a 50 mile round trip. No mileage gain was achieved. Possibly all that happened was that any gain was offset by the increase in weight. Grid charging also caused some of the added modules to die. Gradually I repackaged the remaining good ones into 4 3Ah mocules and finally I removed everything late last year because the wife would be driving it.

In summary, I was not able to realize any return on my $2000 investment other than a better understanding of how batteries work. This is not to say that PHEV doesn't work. The key is that you need to replace the prius battery ecu with something that will let you use the entire battery capacity between charges. But in that case, the batteries won't last as long.:-(

[MetroMPG]

very cool. (and my bad: now i recall you mentioned adding batteries in an earlier post.)

did you by any chance document the prius experiment on the web?

if i'm not mistaken, the EDrive system also replaces the prius' battery ECU in order to take full advantage of the capacity of the additional pack. from the little i've read about the Hymotion setup, it's a parallel battery pack like the one you built (and uses stock battery management).

how hard was it to build your charger? i'm going to be needing a 36v or 48v one for the suzuki project. i've seen mention of home-built chargers, but haven't dived into the heavy reading yet.

i have little experience with electronics in particular, but i'm not averse to getting into a project. regardless of the time involved & learning curve, can you say from a cost perspective whether i'd be better off just buying 3 or 4 "smart" 12v chargers and going the modular route rather than making my own single unit?

[krousdb]

Originally Posted by MetroMPG

did you by any chance document the prius experiment on the web?

Not well documented. Just snippets here and there on vairous yahoo groups as well as GH.

Originally Posted by MetroMPG

if i'm not mistaken, the EDrive system also replaces the prius' battery ECU in order to take full advantage of the capacity of the additional pack. from the little i've read about the Hymotion setup, it's a parallel battery pack like the one you built (and uses stock battery management).

Yep on the edrive. Too much for my wallet to bear. I went the poor man's route. If hymotion does not bypass the OEM battery management then they are wasting thier time and the money of thier investors.

Originally Posted by MetroMPG

how hard was it to build your charger? i'm going to be needing a 36v or 48v one for the suzuki project. i've seen mention of home-built chargers, but haven't dived into the heavy reading yet.

i have little experience with electronics in particular, but i'm not averse to getting into a project. regardless of the time involved & learning curve, can you say from a cost perspective whether i'd be better off just buying 3 or 4 "smart" 12v chargers and going the modular route rather than making my own single unit?

The rectification part is easy. The problem comes from getting the voltage output that you want. If you are running 3 or 4 12V batteries in series then yes, definately it would be better to go with separate 12V battery chargers. That is because when charging batteries in series, if one of the batteries looses a cell, the nominal voltage drops but the battery charger still shoots for a certain charge level. This causes the remaining celss to be overcharged, which results in more cells shorting out. It is a vicious circle that can end up in fireworks. The same can happen with a single battery but you will only loose one battery, not all of them.

The most important thing when running batteries in series is that, the one with the lowest capacity becomes the limiting factor. All of the batteries must be healthy and of the same type and capacity rating. If you notice a drop in performance, it is likely that only one battery will need replacement, not all of them.

[MetroMPG]

Originally Posted by krousdb

If hymotion does not bypass the OEM battery management then they are wasting thier time and the money of thier investors.

my mistake - after your strong comment, thought i'd better check my facts, and i was wrong. according to evworld.com, their 5kwh prius module incorporates battery management, similar to the idea of the edrive system. (the car depletes the added module first, then switches to "stock" operation using the original pack)

The rectification part is easy. The problem comes from getting the voltage output that you want. If you are running 3 or 4 12V batteries in series then yes, definately it would be better to go with separate 12V battery chargers.

thanks for that info. really good advice i hadn't considered before (the effect of a series charger on a pack with a weak batt/cell).

in light of that advice, and particularly because i'm leaning towards using the worst kind of batteries in the building phase of the project (mismatched, used starting batteries of differing capacities), modular charging is really the only way to go.

awesome. thanks. learned something useful today, and it's only 3 o'clock!