Odd HV charging behavior today

so, today on my way home from my parents house, I noticed some odd behaviour from the Hybrid charging system.

My parents live about 180km away, and the majority of the trip is on 100 and 110kmh zoned highways.
For the trip there on Friday, the system behaved as normal, with the usual targeting of around 60% SOC.

However, today on the way home, the system seemed to be targeting about 67% SOC.
I have never seen this behaviour before. Even when accelerating up hills, if the SOC was below 67%, the Battery was being charged.

On flat ground even at 110kmh, if the SOC was lower than 67%, the system was charging the HV battery.
I had 6 green bars for almost the entire trip. When on highway runs, I usually have the regular blue ones and a SOC of around 60-63%, and I only see green when lots of regen happens.

The car didn't throw any errors, or drive any differently than normal.
I still got great fuel economy for the trip, averaging 4.5L / 100km.
(52MPG for those in the USA. And 62MPG for those in the UK.)

Has anyone else seen this behaviour before, and should I be concerned at all ?
The car is 10 years old, 225k km on it and it still has the factory HV battery that is showing signs of its age.

I know I will have to replace it sooner or later, I'm just hoping its later.

 

I'm actually in the middle of a phev conversion again. I have most of the parts that I require, but the batteries and charger to go. I have already looked into a reco HV battery locally. Around $2000 au with 6 months warranty.

I have already prepared myself for that cost, was hoping it would be a ways off yet though.
I would rather replace it once the phev system is running, instead of before, as that would delay the build by months.

Was more curious about the charging behaviour being different than the normal.

Jason.