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Date:  8-7-2019
Number of Hours:  2.00
Manual Reference:  
Brief Description:  Cooling the battery

On the flight from Oshkosh due to high outside temperatures the battery overheated. When it overheats the battery management system disconnects the battery from the charging system to prevent damage. During previous flights the blast tube I had installed for the battery was sufficient to handle cooling. But here on the coast I am not flying in 100* weather. I have made the following changes to hopefully address the issue.

I installed a new blast tube dedicated to the battery. Previously the blast tube was divided to provide cooling air to the battery and a P-Mag. Those are now separate cooling tubes.

I moved the thermocouple to try to get a more accurate reading of battery temperature. The new blast tube woiuld have been directly over the thermocouple and affected the reading.

I placed a heat sheild on the right exhaust pipe where it is nearest to the battery. I am not sure how much that radiant heat affects the battery, but others have done the same.

A closer source of radiant heat is the engine bloc. To build a radiant barrier I covered the battery box with a fibergass / aluminum sheet heat barrier. The sheet is designed as a firewall heat barrier and I had covered my firewall with it to reduce cabin heat.

EDIT: Based on more research I am going to upgrade the battery blast tube to 1" diameter tubing, presently it is 5/8". It will be interesting to see if that has any affect on CHT. I don't know the cooling efficiency loss from taking more cooling air for the battery.

This weekend the termperatures are forecasted to be in the 90s, a good day to test these changes.
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Location of temperature thermocouple

Location of temperature thermocouple

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Heat shield on exhaust

Heat shield on exhaust

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Heat barrier on battery

Heat barrier on battery

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