HV Pack Voltages & Grid Charging

Charging the Prius battery is not recommended. It will shorten the battery life. The Prius system tries to keep the battery between 30 and 80% charge. Going lower will increase the risk of reverse charging a cell and going higher will increase the risk of overcharging a cell and causing venting. Either event will be fatal to that cell.

As for your questions:
There are 168 cells in the Prius battery. The inverter bumps the (nominal) 201V to the 350V range and outputs three phase AC to run the motors and rectifies and converts it back down during regen.
NiMH cell charging voltage is higher than 1.2V/cell, closer to 1.5V/cell. Cell voltage is nominal 1.25V charged but you need more to drive the required current into the cell.
You need temperature monitoring capability so your charge cutoff can work. There are several thermistors in the pack you could use, if your circuit can share them with the Prius system.

-I- wouldn't try this with Pearl, but do whatever you think you can get away with!

 

The Prius traction battery has a nominal voltage of 201.6V but the actual voltage is more like 230V-240V. The voltage is converted to ~500VAC by the inverter. The use of this higher voltage (and corresponding lower amperage) reduces power losses.

 

I am an electrical engineer & Prius Gen II owner. I have been working on a charger, but at 5 amps, not 350 ma. The Prius battery is a lot larger then the Insight. It is 5.2 KWH, so at 350 ma @240 v, that is 84 WH, so it would take 62 hours to charge. Mine would take 4.3 hours.
I'm not so sure what you are trying to do is realistic for a Prius. FYI, the electric motor in the Prius is 68 HP, in the Insight, I think it is 15 HP.

 

The normal Prius battery is 6.5AH with 168 cells giving about 1.3KWH.

Five Amps for 4 Hours would drastically overcharge it and probably cause it to burst.

kevin

 

Welcome Artric!

Charging to 245V on a Gen II (2004-2009) is probably what you need. This is normally the highest set point for an Enginer kit. This way, the SoC will stay below 80%, more like somewhere in the 70-75% range. The Prius gets VERY unhappy if SoC nears 80%, and will spin the ICE to draw off the excess battery charge. There is no problems with imbalance either, so there is no good reason to charge over 80% SoC

The Enginer kit connects downstream of the contactor. The contactor is only closed when the car is in READY mode. You will need to connect upstream of the contactor since the current drain on the battery is at least 1 amp to power the car in READY mode when the ICE is off. If you want to connect the charger upstream of the contactor, then you need some way of protecting your connection against a short in case of an accident, maybe a separate contactor or relay that is only closed when your charger is connected.

The HV ECU is a CAN bus device. Having it tell you the SoC while you are charging would be way to complicated and expensive. Best bet is to have the voltage cutoff at 245V

BTW, Vertex, you can charge at 5 amps, just make sure that you have a separate circuit that is running the HV battery fan.

All caveats aside, there is a small potential market for a Prius grid charger, especially people like me who have a Gen 1 Insight as well as a Gen II Prius with a plug-in kit. Enginer makes no provision to charge the traction battery when the car is turned off, but it sure would be nice to have 7 bars when starting off in EV mode.

 

Hi Seilerts,

I'd suggest you start the car 10 minutes before you need to leave, and then power cycle the enginer charger. the enginer kit will bring you up to 7 bars, and the charger will happily put that power back into the enginer batteries while the car is running...

 

Sorry, late night oil. The number I gave is for 4 batteries in parallel, I forgot to divide by 4. So, it would be 15 hours vs 1.1 hours.

 

Ah, I see what you are saying now vertex. You probably don't need to worry about cooling. Artric, at 350 mA, you definitely don't need to worry about cooling. Also, at least for the traction battery, it would be unusual to charge more than 35% of 6.5 Ah, given that the computer won't let SOC go below 40%, and the target SOC is around 75%.

Flanina, what I usually do is leave the car+pack on for a few minutes when I get home. I just think it is a PITA. Note that the Enginer pack may be putting out 70 amps to run the converter, while the charger is only capable of 15 amps...and I don't know if running the charger and converter at the same time would cause a problem for the BMS.

I admit, a grid charger for my PHEV Prius is an extra bit shiny chrome for the nerd-mobile. My own plan is to have a traction battery charger run at the same time as the engine block heater and be on a two hour timer.

 

Seilerts, Seems like charging the traction battery is overkill with a Enginer System. Actually, for just the 1 traction battery, 1 to 2 amps is enough for me, since I would typically charge overnight. I have a second battery I was going to add in parallel, but my calculations show that even with 4 batteries, I could not get enough range to drive the 2.2 miles home from the train as I orignially wanted to, since it has a lot of steep hills. Once the ICE has to turn on, the point of all those batteries becomes mute.

 

Have you tried running segments in EV mode with your AutoEnginuity, recording SoC, voltage, and current to see what is required? It's hard to see how you couldn't make it with 4 grid charged traction batteries in parallel -- that would give you around 6 amp hours to play with (1.5 ah per). A conservative estimate for range in EV mode is 1 amp hour per mile for flat ground at 30 mph. You would have a budget of over 2.5 amp hours per mile with 4 batteries???

 

I hadn't really thought of that. What I did do was start in EV mode at the bottom of the hill, which is 1/2 mile, steep (7%) grade. With the SOC showing green, I get 2 blocks in EV mode, and I am down to purple with the single traction battery. I would then mostly deplete all 4 batteries going the 0.5 miles. Then I have to drive 1.5 miles which is flat to a few degree uphill grade, to another hill, which is 10% grade, but only 0.2 miles. Of course, I can leave my house to get there in EV mode, and end up with more charge then when I left.
Now, if I dig into the battery controller, and modify it, so that I can use 80% of the battery range, and use 3 or 4 batteries, then I should be able to do it. Of course the battery life will suffer.

 

Kietyyyy was talking about making available a SoC spoofer, I don't know where that's at though. As far as battery life goes, these things are over-engineered, and junkyards are overflowing with Gen II batteries, so it is more a question of making sure that you always have enough left to start the traction battery. Your application is interesting.

 

Spoofing. I understand that if you monitor the bus, and send a second SOC right after the first, the system will ignore the first, and think the second spoofed one is correct. I will have to keep that in mind.

 

Once you get this "battery" bug, it's an expensive and time-consuming disease!

I've built a 7.2kwh A123 Lithium-Ion pack to outright replace the Toyota pack in my '08. Now I'm working on a new Battery ECU from scratch to replace Toyota's. It will allow much better control of what's going on battery<-->Hybrid System wise. I hope to include full 52mph mode and eventually warp-EV mode at up to 70mph. (this is like warp-stealth where the Engine still spins, but with no fuel or pumping loss)

There will be no need to spoof, as I can make my ECU present whatever parameters are needed over the CAN bus, and only those.

 

It is variable speed using PWM technology.
http://www.autoshop101.com/forms/Hybrid03.pdf

Ken@Japan

 

Wow! Please post more details (in a new thread maybe) when it's up and running. Good luck!