Hybrid battery internal resistance in Dr Prius app

Those IR measurements are wildly innacurate. You need high quality / expensive sensors to get an accurate measure of IR...

Just focus on "Voltage Diff" which is what's going to make warning lights come on once that number gets high.

 

It is actually accurate, it reports the internal resistance reported from the ECU monitoring. Toyota sensor on internal resistance and instant voltage is good. Chemically, the internal voltage changes depends on the charged state. Generally, in READY mode, the internal resistance is more accurate because it is under load. It is good when they are all similar, usually less than 25mOhm.

 

"It's going to change with load, temperature and health of battery. It may be a fairly pointless exercise to go for "accuracy" in this case." https://electronics.stackexchange.com/questions/366283/what-is-the-most-accurate-way-to-measure-internal-resistance-of-a-consumer-batte

 

What I meant, it is accurate enough. It is very useful when we have battery error code. If one of the cell have very large internal resistance, 2-3x higher than the rest, it could be bushbar corrosion, not battery cell issues, especially if it is less than 12 y old.

 

Exactly.
Take all readings from that app with a grain of salt. The scales don't change much so it is easy to give yourself a heart attack when you're measuring in the noise. Or for things like this where the internal ECU compensation isn't mirrored to the display.

The real data is in voltage difference and temperature, and that has wild axis graphing!

 

What's always concerned me is when vehicle warning lights detect hybrid error and clear the code and keep driving it resets all the IR measures for the 14 blocks in the pack and takes a while to become accurate again. But more to the point, there's so many distractions when working on these packs DIY style and the more you can simplify how you do it the better. Of course if you got $30K in lab grade testing gear like my rebuilder friend in Bend, OR has, then the software and high quality sensors sorts all that out for you.

 

Error code is a good thing. It help us diagnose problems. In my opinion, if it is more than 12y old, and we get an error code on defective battery, it is the time to check our saving for a new battery. Generally when one fails, the rest are failing too. If the car worth more than $5000 and it is 2015 or newer, $2500-3000 for a new battery makes sense if the rest of the car are still great (suspension, body, engine consume no oil, no rust). Otherwise, time to sell it after slapping $1000 used battery.

 

PriusChat member johnjohnchu made this handy Gen 2 block numbering picture:



So, assuming Dr. Prius numbers the blocks the right way, the service plug is included in block 10, so it wouldn't correspond to what you're seeing at blocks 4 and 5.

If Dr. Prius has the numbering backward, then block "5" would be the one with the service plug—but it would be pretty weird for the service plug to show up as a lower resistance.

So I'd guess the differences being shown are just attributable to something else.

 

miliOhmmeter is very expensive. But we can get cheap enough Voltmeter and they are accurate in mV level. Dr. Prius Apps only report what ECU read and the number can be trusted. In my opinion, your battery is normal. Every block is below 25mOhm. I believe the CEL is trigger if the volt difference between blocks is higher than 1V.

 

Oh yeah, those have block-width doublewide modules, right?