Auxiliary Battery Cooling - ABCool

Submitted by Mik on Wed, 07/22/2009 - 04:45

I have been working on additional battery cooling systems to extend the battery life of 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.

Therefore I designed and built a device I call the ABCool 12V power supply.

It keeps on changing a fair bit, depending on the season and other circumstances.

Particularly the timers are being changed as needed, but the 12V power supply and the relay have now (July 2009) been functioning unchanged and flawlessly since 4000 kilometers and six months!

The ABCool can be installed and removed without making any permanent changes to a Vectrix, if you can find the right connectors to plug into the 12V supply for the cooling impellers: Otherwise it's easy enough to cut the cables and attach any similar set of connectors which you have available.

The initial ABCool design was unnecessarily complex, using two relays instead of one.

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

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The relay is used to ensure that one, and only one 12V supply powers the impellers at any time.
The ABCool 12V supply 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.

The simplified design 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:

Click thumbnails for higher resolution pictures:

I also added a metal screen to stop small animals from entering the battery container:

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The relay part of the ABCool:

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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. By now it has lasted over 6 months and about 4000km.

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An "Energy Logger 3500" (which ran out of warranty real soon after I got it):
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.....
This Energy logger has stopped working and did not give me much joy right from the start. Often lost data. I think it might not be up to withstand the vibrations due to on-road use. I removed it.
Here is an example of the data type collected with it was working:
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Add in the digital double timer and a simpler mechanical timer:

Currently I use a much simpler timer, because it is "Winter" and I rarely need auxiliary cooling. I also avoid regular full charging. The timer just gets dialed up to the amount of time that will be needed to charge to 16/17th with no CC charging.
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Here is the whole, outdated rig (without the relay, from the grid to the scooter):

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:

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This is how it gets plugged in for "anytime, anywhere opportunity charging" in Summer:
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" in Summer:

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 opportunity charging at drink machines etc.) in the boot.