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Does a battery box need to breathe?

FPD218

FPD218

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Mar 29, 2024
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Wisconsin
I built my first DIY 560 amp hour 7,168 watt hour battery box for a standalone system to operate my home furnace. The question I have is the Stanley FatMax toolbox is waterproof and airtight, do I leave it like that and latch the lid or does it need to be able to breathe, that is my question.
 

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To add, it is charged with an 800 watt solar array or the victron 30 amp charger, but never at the same time. The battery box sits inside at 65° f
 
Not sure that gasket is going to withstand much pressure, but can you remove it and not worry about pressure differentials?
 
Very Nice clean setup, even the smart-plug (love it).
With LFP a Sealed Box is FINE ! Provided that the BMS is free & clear of obstructions that may prevent it from cooling.
This is in the basement on the floor, the floor actually acts a bit of heatsink (cooler thermal mass) and being there the ambient temp is likely pretty constant without ever really getting hot. Do keep in mind that "optimal Temp" for LFP is 25C/77F and is usually quite happy between 20C/68F & 30C/86F.

Your Solar Controller will warm up as expected and that is no issue as that won't get too hot with only 2 panels with 800W. The BMS likely won;t get overly warm taking in even the max of 30A and the cells won't heat up much with that low Amperage either, they will warm up a bit but not hot... I've thrash tested systems & packs (Pushing things to edge case limits) and with my 24V280AH packs that it takes about 100A to make them heat up (40C/104F+). Pretty much the same with Deep Discharge, 1 pack delivering 75A and higher starts to warm them up but even at 200A discharge they never went over 42C/107F NB: This is @ Ambient Temp of around 25C which the cells were at as well.

Hope it helps, Good Luck.
 
timselectric said:
Agreed
Heat is the only concern. If you plan to push it hard.
Click to expand...
Biggest discharge will be 26 amps when the furnace is on which is intermittent and cycled 2-5 times per hour depending on ambient temperature. Biggest charge input will be 30 amps.
 
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I like stuff to breathe. Hard to know what moisture, pressure differential, or heat you are trapping. Even a screened 1” hole top and bottom would be enough.
 
FPD218 said:
Biggest discharge will be 26 amps when the furnace is on which is occasionally and cycled 2-5 times per hour depending on ambient temperature. Biggest charge input will be 30 amps.
Click to expand...
I wouldn't expect it to be a problem.
Just monitor it for the first day, to be sure.
 
Steve_S said:
Very Nice clean setup, even the smart-plug (love it).
With LFP a Sealed Box is FINE ! Provided that the BMS is free & clear of obstructions that may prevent it from cooling.
This is in the basement on the floor, the floor actually acts a bit of heatsink (cooler thermal mass) and being there the ambient temp is likely pretty constant without ever really getting hot. Do keep in mind that "optimal Temp" for LFP is 25C/77F and is usually quite happy between 20C/68F & 30C/86F.

Your Solar Controller will warm up as expected and that is no issue as that won't get too hot with only 2 panels with 800W. The BMS likely won;t get overly warm taking in even the max of 30A and the cells won't heat up much with that low Amperage either, they will warm up a bit but not hot... I've thrash tested systems & packs (Pushing things to edge case limits) and with my 24V280AH packs that it takes about 100A to make them heat up (40C/104F+). Pretty much the same with Deep Discharge, 1 pack delivering 75A and higher starts to warm them up but even at 200A discharge they never went over 42C/107F NB: This is @ Ambient Temp of around 25C which the cells were at as well.

Hope it helps, Good Luck.
Click to expand...
That's smart plug controls my original solar setup that was running the furnace. I did this stand-alone system for the furnace so that I could free up that power for other uses inside my home. I can control that smart plug with my app on my phone and pull energy from what I call the warehouse my bulk storage of 1,000 ah of LiFeP04 and feed it into the furnace batteries if needed through the victron 30 amp charger on Sub-Zero days.
 

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It's in shaded building so probably not
Just check temperature on the hottest day of the year and check moisture when it gets the coldest, but your place is climate controlled so it might never make a difference
 
FPD218 said:
That's smart plug controls my original solar setup that was running the furnace. I did this stand-alone system for the furnace so that I could free up that power for other uses inside my home. I can control that smart plug with my app on my phone and pull energy from what I call the warehouse my bulk storage of 1,000 ah of LiFeP04 and feed it into the furnace batteries if needed through the victron 30 amp charger on Sub-Zero days.
Click to expand...
 

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gotbeans said:
It's in shaded building so probably not
Just check temperature on the hottest day of the year and check moisture when it gets the coldest, but your place is climate controlled so it might never make a difference
Click to expand...
Battery box is located inside my house in the basement in a temperature and moisture controlled atmosphere @65 degrees Fahrenheit. There is a dehumidifier that also cycles on and off as needed.
 
So how’s the phonix handle the furnace inrush?

Do you have a draft fan/power vent on the furnace?
 
No problem, yes it's a high efficiency condensing gas furnace, inducer fan is only 285va inrush, the blower motor is a ECM motor, inrush is under 700va total with the inducer fan already running and settles to 515va running pushing the heat upstairs. 515va ÷ 120 volt = 4.29 amps of 120 volt
 
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If only my 2001 power vent hydronic oil burner used so little power. I’ve never actually put a clamp on it, but I’m guessing a solid 10a running power.
 
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