Efficiency of the Charging Process
The 'new / modified' charger programme/software/firmware seems to be more efficient than the original Vectrix software according to the results of some initial testing. The following data, collected just today, seems to support this observation.
Just today, I took the bike out and on return I took a memory dump to obtain a figure for power used on the journey. I had made one stop, and the journey times, average current and ampere hours used all made interesting reading.
I had travelled 24.75 miles and used 16.87 Ampere Hours. The journey included a 200metre climb and descent and a 250metre climb and descent. The break, half way, lasted about half an hour.
On arrival back home I put the bike on charge almost immediately and the charge pattern was as follows:-
The C.P. stage lasted for 2hrs 10minutes - at 864 Watts (6 to 6.7amps)
The tr. stage lasted for it's usual hour - at 1.5 amperes
The C.C. stage lasted for 1Hr 50minutes - at 1.5 amperes
The E.C. stage lasted for 10 minutes - at 1.5 amperes
By calculation, the input power, to the battery, totalled 2515.5 Watt hours or, 18.62 Ampere Hours
The reading on my (mains) power meter read 2950 Watt hrs consumed. Which results in a charger efficiency of 85.27%.
Before using the 'modified charger programme' I have seen my power meter register as much 6450 Watt Hours when doing a full charge (including Equalising Charge), which produces an efficiency figure of about 58% and that calculation assumes that the battery was completely empty.
Efficiency from Mains input to driving power is also interesting.
For an output of 16.87 Ampere Hours, it required an input of 18.62 Ampere Hours to re-fill the battery and that represents an efficiency of 90.6%.
Overall efficiency is therefore equal to 90.6% multiplied by 85.27% and comes out at 77.25%. This is from mains power input to driving power output (battery output, NOT mechanical output.
Has anyone else got figures with which comparison can be made, just as a matter of interest of course?
The Laird.
(The impossible we do at once, Miracles take a little longer)
Perhaps the obvious comment from this data is that the original charger software used KW for heat and also charge. Maybe the Laids program does less heat and more charge!
Regards,
Jonathan
I think that another possible benefit of reducing the amperage that the charger charges at is longevity of the charger itself.
My V had a big recharge today.....from pretty much 'empty'.
it hadn't been ridden for a couple of days, so battery was at around ambient temp and was 19 deg. by the time it finished its charge it was at 23...is that really that bad?
Then I went for a 40km ride. by the time i got home the battery was 27 deg. I plugged it in straight away. within a couple of minutes the temperature DROPPED 2 degrees.
when, exactly, is the heating of the battery from charging a problem?
the heat issue is mainly when approaching full charge.
if going by the bars, unless you have recently (as in the last 24 hours) either had an equalisation charge, or run to red battery light, that may not happen until you hit that last bar.
how full is "full" depends somewhat upon the temperature of the cells (and every cell will be at a different temperature).
at ~24 deg C, self discharge isn't really all that fast till you get above 85-90% SOC.
by the time you are at 40 deg C, self discharge is well fast once you're past 70%.
so a pack that has self discharged some what, so that full bars actually mean ~70% SOC, means you won't encounter pack heating from charging.
That does mean you can only live with half of the rated pack capacity being usable.
Not just from a bars disappearing once past half way point of view, but from the lowest cell (that discharged the furthest because it was the warmest) hitting 0% SOC (and you won't be able to tell, because the bike doesn't know).
Matt
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
Hi,
if the temperature outside is low enough, the temperature drops a bit when it get ventilated during the charging process.
My Vectrix behaves the same. This might be caused by the rather small airintakes when the fans ar off during riding, so
the apparent wind is to weak to vent the Battery enough.
On the other hand if you store your Bike at 15°C some time and charge it up or ride it in warm weather the battery is
"heated" by the warm ambient-temperature quickly to this higher value.
Greetings Mike
Hi folks,
Battery heating. Any heating of the battery is an unwanted effect. It also uses energy, so the charge current is split between heating and charging. Wasteful, don't you think?
When the temperature sensors indicate a rise in temperature of the battery they are actually 'behind the event'. That is to say that the heating effect is far greater inside the cells than it is on the outside where the measurement is taken.
Given a choice, I would chose NOT to have any temperature rise whilst charging. Due to the exothermic reactions within the NiMH cells some heat production is inevitable, but it can still be kept to a minimum.
Minimum Heating = less battery damage.
More important still is the matter of keeping all of the cells at the same temperature as each other. Cells at different temperatures will have widely differing losses (leakage/self dis-charge). This contributes to Imbalance and is highly undesirable.
One way to even the temperatures between the cells is to maintain an air flow around the cells at all times. The actual temperature of the battery (within limits) is less important than the intercell temperature difference.
If the ambient air temperature is greater than the battery temperature, then Fans 'on' whilst riding will add to the battery temperature, however this is not necessarily a problem as long as the whole battery temperature rises gently and all cells are evenly heated.
As a part of my improvement, I have fitted lower power plenum fans. I favour a gentle continuous breeze through the battery rather than the occassional howling gale provided by the Vectrix Plenum impellors.
Not everyone agrees with my unusual views, so if you don't like what I say that is your prerogative. The evidence ,so far, indicates however, that I am headed in the right direction.
Keep smiling:-)
The Laird.
I wonder if a continuous howling gale is not better than a gentle breeze.
I have a feeling that the narrow airflow spaces between cells could cause temperature imbalance if the air flow is insufficiently strong. Some parts of the battery might end up with all the gentle airflow and others with next to none. The temp sensors are all located towards the middle of the modules, the likely place with the most airflow. They will be blind to heating at the ends of the modules.
A strong air-flow will force some cooling to all parts of the battery.
I cannot be certain of this and lack much education in fluid and gas dynamics, but I am quite convinced that the exponential growth of "wind" resistance with wind speed will cause this sort of problem.
This information may be used entirely at your own risk.
There is always a way if there is no other way!
If I remember correctly, it was The Laird who suggested to me that the stock impellers cannot be operated at lower voltages.
This might very well be the case, all I can say is that they can run a little bit slower for several hours without apparent damage. See this video for a rotten poor design to do this with (diodes dropping the voltage and heating up in the process, it works but is not at all elegant or efficient): http://www.youtube.com/watch?v=EiqM0QpuJDQ
Have there been any further insights into the question if or if not the stock impellers can be run at lower speed without letting the magic smoke out prematurely?
This information may be used entirely at your own risk.
There is always a way if there is no other way!
Hi Mik,
Those impeller motors are pretty much fixed speed motors. The start up of the motor takes the form of a pulsing system which gets it moving and then some form of electronic commutating takes over. With a lower voltage/current availability, they will refuse to start or become erratic in their start up.
They do fail. I have a failed one in bits, the electronics side is virtually unrepairable, which is part of the reason I changed to the present 'modified' Computer fans. The modification was done with a junior hacksaw and they are easily replaced, although with a claimed operating life of 50000 hours, I suspect that they will outlive the Vectrix.
If you want a variable speed then the simplest way is to use a brush type d.c. motor and vary the supply voltage /current. Unfortunately, they are not easy to find.
I think that I am right in saying that the original impellers are no longer being manufactured, which is another reason to find a viable alternative.
Keep smiling folks :-)
The Laird
I think the big advantage is that the charger operates at its 50% rating. Which means it is at its most efficient. This may explain the results which the Laird describes above.
Once you go EV, Gas is history!