Lithium Prototype Test

Can you give us more details on how you got the lithium pack down to 2 bars? I've never been able to get it below 4 bars and have been trying often... Of course maybe I just need to head for the mountains?

And yea, battery temps haven't never gone above 60's yet for me...

 

So do you need to program the ECU to work differently??

 

Keep in mind, the OEM temperature sensors take their measurements from the hottest part of the battery pack. On the bottom of the pack, with the sensor tucked into a recess on the bottom of the module. The cooling air has already flowed over the modules, in between modules and is then in the exit plenum with the sensors. They actually see air that has removed heat from the modules are in physical contact with the hot area of the modules.

For the Gen 2: This battery has the temp sensors tucked in a large bump on top of the module, directly in the path of the incoming air stream. The construction of the battery module (earlier provided photos) has no heat generating material anywhere even near the top portion of the module. The sensors could just as easily have been mounted inside the cooling fan or to the outside of the case and be nearly as accurate. I wouldn't consider the temperature indications as a good or bad sign for the battery. They're relatively useless unless the battery gets absolutely smoking hot. Gen 3 will be slightly better, as the initial air flow enters from the bottom of the battery pack.

 

You still aren't listening. Look at the flowpath of cooling air. Look at the location of the cooling sensors. Learn a bit about fluid flow and heat transfer. When you use a real thermometer to take your temperature, where do you take the reading? Most people put it under their tongue to get an accurate measurement. It will be accurate even if you have a fan sitting 3 feet away and blowing in your face. Now hold the thermometer suspended in the air, halfway between you and the fan. Do you think it's going to give an accurate indication of what your temperature is? Temperature sensors mounted on top of modules in a Gen 2 is the same thing.

 

Seems like the terminals might be a good non-invasive way to get a more accurate temp measurement. Also there's potentially enough space to get a temp sensor inside the 3D printed modules. Because Lithium is so much more powerful the packets inside are significantly smaller than their containers, which is great if there's a failure and a packet expands, but lithium is also more risky in terms of fire so you wouldn't wan to get to that point. I'll reach out to Jack and get his perspective on the need to get more accurate temp readings before he goes into full production.

 

While I agree for the most part, the fact remains that we're testing these packs so an investment in selling large numbers of them doesn't fall apart if there's a handful of car fires. As @ericbecky explained to me on the phone yesterday... Lithium packs were done long ago by someone who's business fell apart due to warranty nightmares. There's lots of risks in terms of investing in such an endeavor.

 

I wanted to know if a Prius gen3 is programmed to run with capacity and charging criteria for an NImh battery and then if one were to replace that with a Lipo battery, would you need to reprogramme the ECU??

 

You will likely never get a straight answer.

I'm all for adding more options to the aftermarket, but at some point people are going to have to work on these or may buy a car that has this installed. A major component like this has to have information, not just a "believe me" button.

I'm still curious about how the true SOC of the new battery matches up to the SOC indicated by the car. This is a fairly important issue that I can't get an answer for. Just because the car displays a SOC of 50%, it does not mean this LI battery is actually 50%. With LI batteries having a MUCH flatter curve from full charge to near dead, and apparently a much higher volt/cell, this battery could potentially be at the edge of complete discharge and still be showing 50% SOC in techstream. And I have a hard time believing this LI battery has some magic voltage curve that matches the oem NiMH when guys are on here displaying super high pack voltages, even after running on just EV for multiple miles.. Voltages that are WAY above the norm even for a fully charged OEM NiMH.

I'm sure AZ will be along shortly with his expertise to explain it.

 

See post #49....

 

I've never needed to press the "believe me" button, but just in case, can you tell me where it's located?

 

Making people feel better? On the internet? That's crazy talk!!!