Anyone use Phase Change materials for their packs?

Batteries, Chargers, and Battery Management Systems.
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CONSIDERABLE SHOUTING   1 kW

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Anyone use Phase Change materials for their packs?

Post by CONSIDERABLE SHOUTING » Jul 11 2020 6:27pm

As the title says, I got interested in these materials when I learned the EGO batteries were using it to help control battery temperatures but I realized I'd never seen anyone use it with their packs. Some minor googling says paraffin waxes work well, but there seems to be no "sheets" or anything like that can be bought for projects like these. Has anyone used them?

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jonescg   10 GW

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Re: Anyone use Phase Change materials for their packs?

Post by jonescg » Jul 11 2020 8:36pm

There's a thread on Thermal Management of LiPo which covers some of this. Paraffin is probably the easiest to use - look for a melting point of 40'C or something, depending on your climate I guess.

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amberwolf   100 GW

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Re: Anyone use Phase Change materials for their packs?

Post by amberwolf » Jul 11 2020 11:10pm

Some threads that may have useful info; I'm sure not all of them are relevant, but some are.
search.php?keywords=phase+change+materi ... mit=Search
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Balmorhea   1 MW

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Re: Anyone use Phase Change materials for their packs?

Post by Balmorhea » Jul 12 2020 12:22am

The correct way to approach this problem is to not drive your batteries so hard that they get hot. Use more of them, or use cells with higher real world ampacity.
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CONSIDERABLE SHOUTING   1 kW

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Re: Anyone use Phase Change materials for their packs?

Post by CONSIDERABLE SHOUTING » Jul 12 2020 9:58am

Seems like it. Most companies I've found are commercial-only and the cost seems high enough to the point where I'd just be cheaper and easier to add more batteries instead instead of making a specialty enclosure.

classicalgas   10 W

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Re: Anyone use Phase Change materials for their packs?

Post by classicalgas » Jun 17 2021 11:56pm

paraffin is cheap, and can be mixed with extra low temp (coconut butter based) waxes to get your phase change temperature where you want it. Any craft store has waxes with low melting points.

EV battery heat management is an engineering specialty of its own now, lots of papers showing that wax can help with battery temperatures. I saw one that indicated that wax could cut battery temps by 20%

Air in an un-ventilated battery pack is a lousy conductor, liquid wax is much better, so a metal case is worthwhile.

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Re: Anyone use Phase Change materials for their packs?

Post by 999zip999 » Jun 18 2021 12:42am

don't waxes have a flashpoint with a catch fire I guess if wax smokes that's the first sign of danger . if you put water on hot wax it'll explode.

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Re: Anyone use Phase Change materials for their packs?

Post by classicalgas » Jan 20 2022 10:14pm

More research on wax as a PCM (phase change material) heat sink for batteries is being done . Mixing in graphene to improve wax thermal conductivity, heat tubes to move heat outside the pack, etc.

It looks like, for hobbyist application, a coconut wax with a small amount of soy or paraffin would be ideal. Coconut wax has a very low shrinkage when solidifying compared to most readily available waxes, and a very low temperature (100-110 F) change to liquid. A bit of soy wax raises the phase change temperature into the 120 F range . Waxes are electrical insulators, so in theory you could pot the whole pack, BMS and all.

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