Auxiliary Battery Cooling

Mik's picture

The writer of this blog accepts no responsibility or liability resulting from attempts to repeat or perform the procedures described in this thread. This information may be used at your own risk. Click for more details.
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I have been working on additional battery cooling systems to extend battery life for my Vectux.

Keeping NiMH batteries cool is one of the most important parts of looking after them.

There is every chance that charging efficiency, range and battery longevity will be positively influenced by removal of heat from the batteries when they are more than 25°C warm.

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The Auxiliary Battery Cooling System (ABCool) consists of the standard Vectrix Battery Cooling Fans inside the battery housing and additional 240V-->12V power supply with it's own cooling fan and a double timer with (supposed) surge protection.
Some pictures of the fans inside the battery cover: (Click image to enlarge)

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Relays are used to ensure that one, and only one 12V supply powers the fans at a time.
It plugs into the connector under the front seat and allows the original charger electronics to function completely unchanged when the ABCool is not plugged into the grid.
Additional cooling periods before and after charging can be programmed via one of the two timers; the second timer turns the on board charger on and off.
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Follow the links to more detailed descriptions of the device and the background.
Click on photos to enlarge them.

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I the process of observing the latest "Recharge after BaLPoR" I discovered a design fault in the ABCool 12V power supply which causes two potential problems.

The design fault is not only easily fixed, but also makes it half as complicated and cheaper to build. KISS!

Here is a schematic of the inferior design, which is currently installed in the Vectux:
Photobucket
This design is unnecessarily complicated, but works well in winter....
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And this is the new, simpler and better design (but not built or tested, yet...):
Photobucket

The first problem
with the first design is that the Vectux charger activates the DTDP relay, which then switches the 4PDT relay on, so that the Vectux charger electronics provide power to the fans, no matter if the ABCool is plugged in, or not. This can cause unnecessary battery depletion in very hot conditions.
The second problem is that if one of the two relays fail to switch and the ABCool is not on, then the charger would run without cooling fans. This would not cause immediate severe damage, because once the battery temperature climbs to 46°C the charger will pause. This was involuntarily tested by siai47.
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The new, improved setup requires only one relay.
The Vectux charger is supplying the fans with 12V by default, even if the relay becomes faulty and fails to switch years later.
When everything is still working and the Auxiliary power supply is turned on, then the relay switches so that the auxiliary power source supplies the fans with 12V power, no matter if the Vectux charger is also trying to run the fans, or not. So mains power is used whenever available for cooling the batteries.
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The new design has 2 advantages over the current design:

Advantage 1): If any of the relays fail to switch, then the Vectux will function like a normal Vectrix. Currently a relay failure would cause loss of battery cooling during charging (if the ABCool is not plugged in) because the "default" position of the relays is to have the Auxiliary 12V supply switched on.

Advantage 2): Even in very hot conditions (battery and/or ambient temperature more than about 35°C (= the trigger temperature for the switching on of the battery cooling fans by the Vectux electronics), the power for the fans will be provided by the ABCool when it is connected to the mains power supply.
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With the first design the following scenarios are possible:
Scenario 1):
The Vectux battery is hot after riding in 35°C ambient temperature; the battery fans will therefore run spontaneously when the Vectux is being parked. Even if I plug in the first design ABCool, the power for the fans will continue to be provided by the battery, not by the ABCool. This leads to further depletion of the battery and further heating of the battery. Not much, but totally unnecessarily.

Scenario 2): After charging has finished in a hot environment the battery will be so hot that the fans remain switched on by the Vectux electronics, using power from the hot battery, even if the ABCool would otherwise run the fans by using the grid without depleting and heating the freshly charged battery.
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In summary (it's really the same stuff for a forth time, sorry to be a bit repetitive here...):

The first ABCool design will not allow additional cooling to be powered from the grid at those times when the Vectux electronics have decided that battery cooling is needed.
These are of course the times when cooling is needed the most and for the longest periods, and the power for this will come out of the battery, not the grid.

All I need to do to "upgrade" to the new version is solder connectors to a new 4PDT relay, and click it in to replace the double-relay in this photo:

Mr. Mik

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Comments

Great post Mr Mik!

I'm "electrically-challenged", and I think even I can follow this.

Mik's picture

Now that the "Battery Rework a la Mr. Mik" is completed and the Manual Battery Management System (M-BMS) is working, I have finally built and tested the modification to the ABCool described above.

The simplified circuit now also includes a diode. This is to safely discharge the energy stored in the coil of the relay when it is being switched off:

Photobucket

Click thumbnails for higher resolution pictures://i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/Battery%20rework%205%20BMS/th_ABCool25.jpg)

I also added a screen to stop small animals from entering the battery container: //i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/Battery%20rework%205%20BMS/th_DSC06228.jpg)

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The relay part of the ABCool:
//i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/Battery%20Rework%206%20BMS/th_DSC06252.jpg) //i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/Battery%20Rework%206%20BMS/th_DSC06268.jpg) //i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/Battery%20Rework%206%20BMS/th_DSC06264.jpg)

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The 12V power supply was changed to a laptop power supply, without a fan. It is much smaller and more waterproof than the power supply I used previously. I used "Liquid Electrical Tape" to waterproof it a bit more. Only time will tell if it works long-term.

//i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/Battery%20Rework%206%20BMS/th_DSC06283.jpg)

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An "Energy Logger 3500" (which ran out of warranty real soon after I got it):
//i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/Battery%20Rework%206%20BMS/th_DSC06274.jpg) It works much better now: Multiple outlets, and Australian ones for that. It does not only measure energy consumption, but it also logs the information. Included software can turn it into graphs on a computer. That will enable me to quickly check what happened during charging whenever something interesting has occurred, for example the next time when the battery inexplicably only gets charged to 16/17th.....

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Add in the digital double timer and a simpler mechanical timer: //i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/Battery%20Rework%206%20BMS/th_DSC06288.jpg)

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Here is the whole rig (without the relay, from the grid to the scooter):

//i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/Battery%20Rework%206%20BMS/th_DSC06292.jpg) A waterproofed RCD; a "Surge Cube"; the Energy Logger 3500; three timers; a little tester that shows if a power outlet is wired correctly; and the 12V power supply.

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The relay and 12V power supply installed: //i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/Battery%20Rework%206%20BMS/th_DSC06295.jpg)

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This is how it gets plugged in for "anytime, anywhere opportunity charging":
//i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/Battery%20Rework%206%20BMS/th_DSC06310.jpg) The charging delay and time can be freely set in 15min increments by charger 3, the cooling fans are permanently "ON". Two intervals are set by jumpers: 2hrs and 4hrs, that means it's just a quick turn on the dial to choose a pre-charging delay and charging time. On the very rare occasion when the battery is totally empty and I want the Vectux to have a full unsupervised charge I can move one jumper to make it 5.5hrs. It would only take an additional second to this.

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This setup will be used for regular "Commuting Charging":

//i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/Battery%20Rework%206%20BMS/th_DSC06316.jpg) Timer 2 is set to cool the batteries after riding, during charging and after charging. Charging is programmed via timer 1 to start in the early morning. This will deliver a full battery just before the trip to work; the fans run until I actually ride off. At work the fans run for 5 or 6 hours, with a full charge being delivered in the middle of this time. All fully automatic. I replaced the tiny button cells in the digital timers with 2x AA Alkaline batteries, they will last years!
You can also see that there is space for another 8m extension lead (grey for good reasons....) and a bag with other assorted goodies (like tyre pressure gauge and a double adapter for drink machines etc.) in the boot.

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And the large helmet still fits in!

//i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/Battery%20Rework%206%20BMS/th_DSC06321.jpg)

This information may be used entirely at your own risk.

There is always a way if there is no other way!


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