Even / odd battery voltages!

Well here's an odd one. Went to start the car this morning (last used a few days ago) and got a triangle warning light and no "Click" from the main HV relay. Pulling out Torque and Dr Prius, they both claimed no ECU fault codes, and then I did a double-take when I noticed THIS

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All the odd numbered blocks reading as about 10v, all the even numbered blocks reading as about 16v.

Has anyone seen anything like this happen to a battery pack? I can't see how it's possible for a battery pack to end up like that, so my only thought is that it must be a problem with the voltage sensors in the battery controller.

 

Solved!

I'd assumed it would be a faulty battery ECU, as I've had issues with it previously (corrosion and a cracked pin on the voltage probe plug) so I went ahead and bought a "battery ECU" on eBay to replace it with and resolved not to bother opening the battery up until it arrived.

Meanwhile, the 12v battery level dropped to useless (there's a phantom current draw that I really ought to get round to tracking down...) so I dug it out to charge. The ECU arrived today, so I took the fully charged 12v battery out to the car and, noting the possibility of a logic glitch, decided to try plugging it back in just in case. Lo and behold, normal battery voltages!

So, the cause was either (or a combination of)
- battery ECU getting glitchy and needing disconnected and reconnected (this surprised me -- I wouldn't have thought the battery ECU would be powered with the ignition off?), or
- low 12v battery level causing problems for the ECU (dropping too low to provide a reference voltage for a DAC input?)

Just as well, as it turns out what the ebay selled had sold me (and physically labelled) as a "battery ECU" was in fact a hybrid control ECU so I would be sending it back anyway

I'm going to be trying to track down the phantom current draw, and I'm still suspicious of that battery ECU.

Thanks for your suggestions!