Can HV battery individual modules be scanned for fault indication?

The mini VCI can check the voltages and internal resistance of module pairs in the battery also the temperatures at three points. The VCI uses Techstream software "the same as the dealer" available on Ebay for around $25 with the software. There are other very good alternatives including Priidash and Android software requiring an Elm 327 devise.

John (Britprius)

 

I have a 2007 Gen2, 63,000 kms in Sydney Australia

Scangauge can do both - on the Gen2 they are labelled BCD (battery cell delta) and BUC (battery upper celsius).
Normally BCD should be zero, anything else tells you that at least one cell or module is out of line.

Don't worry too much about high ambient temperatures - down here we have plenty of hot days over the old century mark and provided the AC is always on the battery stays below 45 deg C. Don't turn off the AC and tough it out with open windows though - the battery is cooled by air from the AC. Extreme cold weather is more to be feared than hot I suspect.

The battery state display in the MFD only shows part of the full charge/discharge range. When it goes pink my Scangauge shows trus SOC to be about 45%, and first green shows up at as little as 75%. Full green is usually about 85%. The ideal situation is for the thing to stay blue all the time - the Toyota system works best when the battery charge is going up and down frequently, and converting regeneration to motion regularly. I've driven all day on dead flat outback roads and got worse fuel economy than on moderately undulating country because the IC engine was working all the time.

 

The dealer will not do anything until the car has actually set a DTC. That happens when the HV batteries have fallen to an even more depleted state than what you are experiencing. There have been a number of postings here of people swapping individual cells to get back on the road. It remains to be seen how long these fixes will last. The cells are made to a high level of consistency, so if one is going, the others are not far behind.

As for heat and battery life, the battery experts here warn of the fact the NiMH battery has an exothermic condition, where at full charge it will generate its own additional internal heat for a bit. So the scenario to be avoided is to go down hill, charge the battery to all green bars, then stop the car and park in a sunny location. That will raise the battery temps to undesirable levels. Best to let the car sit with the A/C running until the charge drops down a bit before parking.

 

This is not always the case, maybe in your hotter climate.

The battery at all green bars is only at 80% charge (nominal) so some way from being fully charged and even in sunny conditions in some countries the battery temperature will be below that of where the battery fan turns on "even slowly". Turning the A/C on in these conditions will in fact warm the battery not cool it, as the A/C can and does put substantial load on the HV battery. This will cycle the battery more and use more fuel in doing so, and not cool the HV battery unless the battery fan is already running.

Living in the UK "and there will be many other countries this applies to" although we do not usually get temperatures much above 25c we do get temperatures down to -15c even in the sun. I have never heard my battery fan running in five years of use except when testing the fan with Techstream.

I am not saying in a hot climate this should not be done or is not a good idea, but I am saying it does not apply to all situations "one size does not fit all".

John (Britprius)

 

Yes, John, right-o. My example was specifically related to places like the desert southwest (AZ, NM) and such, where the car will get quite hot when parked. I have seen my battery temps go up after parking with all green bars, and returning 10 min later, so I do the cool down with A/C. It only takes a couple of minutes to lower the charge one bar or so.

My battery fan runs at ~6-9 volts normally, with battery temps ~45C when working lots of hills.