MOWER: Active cooling to reduce battery operating temperature?

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Every time I run the 20" mower, I'm a little concerned when I open the battery cover, and it's just really warm in there.  I haven't used my IR thermometer to read actual temperatures, but I did watch a YouTube video where a guy was checking the temps before and after charging on the fast charger; and they were back to ambient temperature.

This is a 20" mower running on 2.0/2.5 AH batteries, not the 4.0/5.0/7.5, so maybe those batteries run cooler overall since they have more parallel strings of cells to draw from (either 2P or 3P, not 1P like I have).

So I'm sure some Ego Engineer has thought about putting the fan from the charger into the actual tools; maybe not all of them, but the high current draw like the blower and mower (probably chain saw too), might make sense?  The blower and chainsaw, maybe less so because the batteries are not enclosed like the mower.  Granted, the mower battery is the one that would be subject to the highest exposure to fine dust/dirt (unlike the trimmer, blower and chain saw).

I might run some back to back tests with the top cover removed to see if the temperature difference is significant.  Since there isn't a fan in the mower, the risk on pulling dust into the battery seems less than when it's recharging (which is why I place the charger on a nice clean work bench, not the ground).  And I'm not planning on mowing during a downpour... =)

Anyone else notice the battery compartment in the mower is significantly warmer than ambient?
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(a)Typical Engineer

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Posted 3 years ago

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Exrace

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Next time I mow (looks like again this weekend) I will put a lab thermometer in my 21 and see what the temp gets to. I will be using the 7.5 battery pack.
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Blue Angel, Champion

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ATE, I've noticed the same thing, but I think the culprit might be solar radiation.

When I mow, either with the large or small battery, if I remove it right away I notice the end cap is very warm. Then if I feel the inside of the battery (the vent near the contacts), it's only slightly warm.

I believe the combination of exposure to the sun and lack of airflow makes the end cap heat up a lot. I mentioned this in a thread a long time ago, and thought I might even paint the battery cover lid grey to match the deck and keep the sun out.

On the topic of air cooling, a simpler solution for most tools could be to drill vent holes under the battery (like the chargers have) and allow the tools to draw air through the battery. I think all the tools use a fan to draw air into the tool body, making it a low pressure area.

I thought about this with the blowers in particular since they draw so much continuous power and have such high airflow. The drawback would be sucking all kinds of dust into the battery.
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Ken, Champion

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Keep in mind, Ego designed their batteries with heat management in mind. That's why the cells are arranged in an arc rather than a block, and they are well ventilated. And the individual cells are wrapped in a phase-change material that is activated electrically when the battery reaches a certain temperature to turn liquid and draw heat out of the cells.
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I guess I should have added that I basically stopped worrying about heat issues with Ego batteries after watching so many videos demonstrating their amazing design. :-)
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Jacob

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The pcm is melted at a certain temperature, that is how it is "activated".

It uses the "latent heat of fusion" in the pcm itself to act as a thermal battery.

More than anything, the pcm acts as a thermal regulator to maintain temperature at a specific temp for a long period of time. It isn't activated electrically. That would be the peltier effect.

Once the PCM has melted and temperature keeps rising, the pcm only provides thermal assistance based on the "Specific Heat" of the PCM.

Once the pcm has gone from liquid to solid, it does the above but backwards and equal.

Clear as mud?
(Edited)
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Blue Angel, Champion

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Barnaby created a lot of confusion when he incorrectly stated that the PCM was activated electronically.

The truth, as you point out, is just the simple physical properties of a phase change. Elegant in its simplicity. :-)
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Ken, Champion

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That'll teach me for taking the word of Ego's spokesman for how their products work! But it doesn't change the fact that Ego has designed their batteries with heat management in mind.
(Edited)
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Jacob

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There is a possibility that the pcm is electrically melted during cold operations. So if the pcm has a phase change temperature of 40deg F, whem the battery senses it has dropped below 40f it could heat the cells, which would heat the pcm to melt it. This would allow phase change to work over and over to keep the battery pack warm. The inverse is not possible without using the peltier effect as it would need to force the battery to cool itself.
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If we look at the lessons learned between Tesla and Nissan (Leaf),  having a BMS (battery management system) makes a big difference in the long term.  Since the charging phase is an actively cooled system, and the operating phase is a passive/non-cooled system; the next generation of Ego Tools can increase their cutting edge advantage by incorporating active cooling during the operating phase.

Agree that Ego has the best OPE (outdoor power equipment) Li-Ion solution at the moment (just like Tesla).  If (once) that happens, you have effectively controlled the temperature of the battery during all phases of operation (discharge and re-charge), which can only increase long term reliability of the system.

The only trade off is additional cost and complexity.  On a tool like the blower, it would be relatively easy to have a pipe between the air channel (pretty much anywhere), and the battery area.  That would be a simple active cooling solution, as the fan would be the source of the air flow.
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Blue Angel, Champion

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I'm not sure what temperature the PCM melts, but if we look at the following discharge temperature graph for the Samsung 25R it doesn't look like temperature would be a huge concern for most Ego tools:



A 50V 600W system (480 blower on Turbo and 20" mower at full load) is drawing 12A. The 1P 25R (2.5Ah) battery would rise to somewhere around 68C with no cooling. I'm sure that's a little hotter than optimal for long life, hence the PCM.

Likewise, a 50 V 1000W system (chainsaw or 21" SP mower at full load) would be drawing 20 A divided by two strings of cells (10 A per string) in the 2P battery (5Ah). In that case the 25R would increase to about 60C un-cooled. Once again, enter the PCM.

If you look at this document:
https://www.powerstream.com/p/INR1865...

...and consider the abusive testing these cells are designed to put up with (including long term storage at 60C!), I think Ego has a pretty solid solution on its hands.
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Michael Cook

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I watched a video of a guy take apart an EGO 56v 5ah battery and an Echo 58v 4ah (?) Battety. The way EGO designed their batteries with the water resistance inside the cap, the arc construction, the mesh vents in the battery, the heat protection in the phase change battery cell casing. I wouldn't worry to much about the heat in the battery area. They designed it, and warranty it for 5 years, and the battery for 3 years. You might void the warranty by painting the battery cover.
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Blue Angel, Champion

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Very true!