Are fans needed to cool down battery packs?

Joined
Jul 16, 2021
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Location
Stuggart, Germany
Hello everyone,
I was considering buying pc or blower fans to cool down my 52v 6p 18650 battery pack, but I think I will run into problems when it rains.
Has anyone else did something similar like this, if so can you share your tips!
Thanks
 
No need for fans. HUGE need for a better or at least larger battery if you are heating them up that much. If you are, your rate of discharge is hammering the battery into dogshit.

Whats too hot for lipo? when you can't touch them because the shrink is melting. Quite warm to the touch is ok, though they may not last quite as long. Putting them in an aluminum box can help them cool down, but not till you stop riding.

The only place for such cooling would be on a dragster or race vehicle, where you are willing to pay the price to win. You still going to buy new battery each race, the cooling is just to make it to the last lap.
 
Sorry guys for the late response, i''m new to this site and didn't know you have to manual turn on notifications.

Eastwood,
I'm pulling 15.53 amps

dogman dan,
When I touch my battery its mid warm after a ride its mild warm, but definitely not hot. I'm more concerned when I have to leave my bike in the sun for maybe an hour or two. The battery is going to be rested against my aluminum bike frame and inside a case, but I fear the heat will overheat the cells eventually! :cry:
 
High temperatures from outside Ambient may reduce longevity, but they do not do "damage".

Using the pack at a C-rate that causes heat rise internally is 1000x worse
 
You could place a probe in your battery case and attach the temp monitor to the handlebar. Then you will know if cooling is necessary. If it is, simple means of improving air flow are doing fine most of the time.

Active cooling, when necessary, should be liquid ideally, and combined with heating capability. We circulate a small tubing between the rows of cells when building the battery, then a small pump combined with cooler and heater systems can be wired to a thermostat and regulate the battery temp in real time. But, this should not be necessary for an ebike unless it is a performance monster, or one that was built with insufficient battery quality/capacity.
 
MAny many OEM use passive and active air: no need for water complexity unless you have warming goals too, IMO... NOt enough entropy in the system we like ( sized).

1: depends on the cell and the load.. Bad cells or undersized packs do get hot, warm and do hate it...

HOTLIPO.jpg

2: You dont really need it.. Unless you plan like 30kW e-bike out of a Nuclear controller.. That should have a pwm output available.. for a 12v fan ( three leads).. But ..

The volume of air I can push through this box is easily able to overcome any heat production I see in the future... When it rains, the pack will get wet, for there is nothing to corrode on this pack. It could work under water. I would not want water or vapor trapped inside a 18650 steel cell shell pack. Keep that dry.

I pulled 18kW out of this battery in this box and it did NOT get hot ( with my cell choice) .. Not one degree hotter run with a measly 10C, 250A~ peak... , 20s pack. Did not get hot going 50mph doing wheelies up a hill. Let me upload a pic. The motor was blazing and the controller was warm to touch but the battery was cool as can be. THis pack has three (3) heat sensors.. One for the PCB, one in the center of the pack, and one on the BMS shunt bar.

FANBOX.jpg

Many people study the entropy of cells to enumerate a number of watts per amp hour capacity the cell can withstand.... to see the actual heat load and extrapolate the lifespan... longevity... . Easy numbers if you know the formulas.
 
Admiral_cows said:
Hello everyone,
I was considering buying pc or blower fans to cool down my 52v 6p 18650 battery pack, but I think I will run into problems when it rains.

If your cells are getting so hot they need cooling, you're doing it wrong. Use more cells, or cells with higher current capacity. Just cooling the pack doesn't negate the ass beating you're laying on your battery.
 
Sounds like you got a normal, real world battery situation. Nothing is getting hotter than normal. Do try to park in the shade when it must sit there all day. If you must, prop a piece of cardboard or whatever to keep direct sun off the pack. Every bit helps some.

But your battery must live in the real world, which is why your lifespan is simply not going to equal the tests done in a room temperature lab. Its going to be charged when its a bit hot, discharged when it damn cold, etc. Its nothing but an expensive brick if you cant use it in anything but room temperature weather.

The main thing to avoid is letting the thing sit around for days and days, fully charged, at temperatures way over 110 F.

In other words, not sitting on the dashboard of a locked up car in summer. The garage at 110f is not ideal, but not fatal to your battery either.
 
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