HV Pack Voltages & Grid Charging

Probably get some help too from us other mod-dudes wild enough and tech enough to try stuff..

Yeah, I will definitely keep you guys posted. It's a matter of time is all...

Very interesting concept. Probably too rich for me, those A123 cells must have cost a pretty $. Very interested to learn how your battery ECU replacement works out!

The Prius Battery ECU monitors the current in/out of the pack to know its SOC. If you charge the pack when the car is off it will confuse the ECU and potentially damage the pack from letting it overcharge it during regen. As I understand it, the Chinese Enginer PHEV system only charges when the car is on, so the ECU sees the current coming back in and therefore doesn't need to "spoof" the ECU, it works just like it is supposed to.

The stock packs are quite small (6.5ah spec) there really isn't much value in charging them, you can't add much energy to them to be worth the trouble and expensive.

Jack Murray

The ECU monitors both current and voltage. Although monitoring current gives a more accurate estimate of SOC, the voltage monitoring will prevent overcharging, so that should not be a concern. The ECU may be confused initially, but should correct is self after the first discharge cycle.
For me, the purpose of topping off the battery SOC is that I can make my morning commute without the ICE starting in EV mode. For most people, however, I agree with just the standard battery, it is mostly a wasted effort.

As we are talking about the Battery ECU, you might find my teardown and analysis post interesting.

Was a charger for the stock battery pack ever done?

This is something I could definitely use.

There is a Toyota charger mentioned at http://www.autoshop101.com/forms/Hybrid15.pdf. For what purpose would you have a use?

I like the idea and it would be useful where I live.

Having said that, I've read other threads on how this can shorten the lifespan of the battery. I'm not one to follow the rules so I'd like to try it. I know charging it can be done safely but I'd like to try it and see if I can shorten the lifespan of my Prius battery.

They've talked about this a lot at insightcentral.net. Grid trickle charging on a Honda battery is beneficial, as it helps to rebalance the pack, which the computer doesn't do very well. The two approaches are daisy-chaining Meanwell-type power supplies, or plain old ATX power supplies. Or, watch ebay for a lab HV power supply.

If you can hook up such a supply without electrocuting yourself, then you are also capable of rebuilding or swapping the battery if it goes bad.

A 250V power supply and a canbus unit which can read traction battery SOC should be sufficient. leave the car in ready, and then turn on the power supply. once the SOC reaches 70% (or whatever) have the can unit switch off the power supply. you'd probably also want to tap into the power switch to shut the car down at this point.

It would be useful for people living on hills. try to arrive home with 1 or 2 bars, leave home with 8. cycling the battery like this every day would not be good for it though.

This may be a dumb question but couldn't I just use a power supply that has a monitor on it (over voltage trip, over current trip, etc) with a low current output that has a timer?

Yes, you can

Got a suggestion for a good battery charger?

Really, besides the Toyota service dept. battery charger, there isn't another that will cover the NiMH OEM battery requirements.
The most compatible will be an Electrophoresis or Lab power supply and these will not have any charging profile for NiMH, are complex power supplies

Personally, I wouldn't bother.

Does anyone have a link to the thread where some DIY PHEV tinkerers had a fire and explosion (by overcharging?) an extra NiMH pack? IIRC, they were in the UK.

I recall bwilson4web did some charging experiments on modules and either he or someone else shows what can go wrong... Maybe someone can post a link to that too.

I've seen all of the pictures. I guess from my point of view, it is a rechargeable battery and it can be recharged. And yes, I understand the implications of doing so.

I used to work on the electric buses for San Fransisco and the technology was very similar. We would charge the traction batteries with a floor charger. I do know that the charger costs more than an arm and a leg.....

That person is Nikki Gordon-Bloomfield aka aminorjourney, here is a shortcut from those days.
By the way, she was using a Zivan charger to keep her batteries fully charged........
and this is what happened to her...........

This is why charging the stock pack in ready mode is so important. if you get over voltage, or over SOC the prius will spin the ice to burn off the excess charge. using the enigner kit to charge the stock pack i have seen 8 bars on the display a few times, but never had the ice spin up so don't really know what that sounds/feels like but i imagine it's fairly noticeabe.

Ideally your power supply will stop output at 240v and will also monitor SOC to stop charging at 75% or so. it's very possible to exceed the 80% SOC at much lower voltage (high SOC followed by a high load which will drop the V very quickly, or very cold batteries)

It's always a great idea until something goes really, really bad.