This issue was first pointed out by Andy1:
Those 3 degrees difference were in a time frame of 1 minute (from time it unplugged the bike to the time I pulled the left brake). Is that normal?
In the following post:
http://visforvoltage.org/forum/7494-vectrixs-recharging-process-add-yours
Today I took more pictures of the Vectrix's recharging process. I noticed a temperature jump like Andy1's:
When the convential charge stopped and the cooling phase quicked in (5:10h to 5:11h), the display turned off, as always . In order to take the pictures I was forced to switch on the bike with the key, and surprise! The temperature showed a 2 degree celcius increase!.
I noticed also that the temperature display when you turn on the bike is always 21 degrees. After a while the temprature is calculated and displayed. Maybe the formulas (its a mix between different temperature sensors)used to calulate the temperature during the recharge process are different. This can explain those 3 degrees of difference...
The 21degC means nothing, it just displays that number whilst it boots up and gets the real measurements from the sensors. It probably cannot display nothing, so they picked some number to display when it does not yet know the real temperature.
The change in temperature after the impellers are turned off is because the cooling air stream has ceased. If you were charging in a hot environment, with air temp higher than battery temp, then the temperature would drop a bit after finishing charging. The temp sensors stick out into the air between the battery cells:
If you look into it a bit longer, you will find that the temperature will continue to rise for up to a few hours after charging finishes! You seem quite motivated to investigate at the moment, please check it out!
Particularly after a full charge or after an equalization charge there seems to be a continued temperature rise after charging.
I think it is due to three factors:
A) Temp sensors measure a composite of actual cell temp and air temp. So the lower temp whilst the impellers are running is a measurement error, same as above.
B) The core temperature of the cells is higher than the mantle. This temp gradient equalizes over time once the air flow ceases, causing the measured temperature and the air temperature to become the same (usually higher) temperature.
C) There might be some hydrogen and oxygen pressurizing the cell after an overcharge. These gases are recombined in an exothermic reaction. The pressure drops, the cell heats up. That might be why the self discharge of NiMH on day one is very high. It radiates heat!
Due to all of this it is very important to continue cooling for several hours after an equalization charge. I do not know how much of the end of the equalization charge in the newer firmware consists of just running the cooling impellers.
Could those people with "wattsup meters" (or something like it) have a look at the current draw pattern during charging with the later software version, please?
This information may be used entirely at your own risk.
There is always a way if there is no other way!
Very interesting answer, thank you very much.
You're completely right. If we have a look at the pictures:
First line has been taken one minute after finishing the EQ. 147v and 27 C degrees
The second one has been taken about 5 hours later. Voltage has drop to 142v and temperature has increased to 30 C degrees... And the bluetooth has turned on BH...
However, Andy1's temp incresase can't be explained by this process. I'm still suspecting that it has more to do with two different ways of calculating the temperature. The individual sensors may send the same temp, but perhaps the total ammount is calculated using different mathematical parameters, depending on riding or charging situation..