Suck or blow?

[Kelpie]

I'd like to improve the ventilation to the locker housing all my electrical gear. It houses charge controllers, inverter, lithium battery etc.
The BMS for the battery can hit 60º when it's working at full capacity so I really need to get a good cross flow going.
My plan is to place an air intake in the cockpit (with a weatherproof cowl) and have the outlet in the coaming.

Should I put the fan on the inlet or outlet?

 

[Refueler]

Normally I would go for 'extraction' - to avoid any heat from the fan motor itself being in the 'cooling air'.

What you are looking for is maximum cooling ... even those 1 or 2 degrees can be worth it.

 

[Thistle]

I agree with extraction. I'd also be trying to work out why things are getting so hot in the first place and I'd also be thinking about ways of using any heat produced rather than just dumping it.

 

[Alex_Blackwood]

I agree with extraction. I'd also be trying to work out why things are getting so hot in the first place and I'd also be thinking about ways of using any heat produced rather than just dumping it.

Yes for extraction. I think he may be in he Caribbean so using heat may not be top of his list.

 

[Kelpie]

I agree with extraction. I'd also be trying to work out why things are getting so hot in the first place and I'd also be thinking about ways of using any heat produced rather than just dumping it.

The heat is from the FET based BMS on the lithium battery. It is only a problem at maximum current draw which is just a few minutes per day, if at all. But it will shorten the lifespan of the battery if I don't do something about it.

Average temperatures here are high 20s or more, so anything I can do to remove heat from the boat is good.

 

[coopec]

I think it should suck and the fan should be spark proof to avoid possibility of explosion. (I wasn't aware of this)

"Lithium-ion and lithium-metal battery cells are known to undergo a process called thermal
runaway during failure conditions. Thermal runaway results in a rapid increase of battery cell
temperature accompanied by the release of flammable gas. These flammable gases will often be
ignited by the battery’s high temperature, resulting in a fire. In addition to the combustion of
these gases as they vent, another concern is the accumulation and potential explosion of the
gases.
https://www.fire.tc.faa.gov/pdf/TC-15-59.pdf

 

[Refueler]

I think it should suck and the fan should be spark proof to avoid possibility of explosion. (I wasn't aware of this)

"Lithium-ion and lithium-metal battery cells are known to undergo a process called thermal
runaway during failure conditions. Thermal runaway results in a rapid increase of battery cell
temperature accompanied by the release of flammable gas. These flammable gases will often be
ignited by the battery’s high temperature, resulting in a fire. In addition to the combustion of
these gases as they vent, another concern is the accumulation and potential explosion of the
gases.
https://www.fire.tc.faa.gov/pdf/TC-15-59.pdf

With most cells used for boats / cars etc. - they are hard cased. This reduces the risk substantially. It can still be catastrophic - note TESLA cars known to catch fire. But it is extremely rare.
The greater risk is with the non hard case Li batterys - particularly LiPo where only foil pouches contain the cells with heat shrink around to hold all cells together. But these would not be used in boats cars etc unless carried on for specific use by person. Even Computers and phones use a hard case version .....

There is actually more risk from a Lead Acid battery - which gives of Hydrogen Gas while charging ...