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Old 9th August 2006, 03:19 PM   #1
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Default finally beginning my case/enclosure - heat question

just thought i would share a picture of the case i am building
for a sonic impact amp. I am going to be using a 12 volt sealed lead acid battery with a smart charger.

on switch will turn on and off the amp
the other switch will turn on and off the charger.

I was just wondering if I should worry about heat build up in the case.
I wasnít planning on adding any vents, but will do so if people here think
its necessary. any answers and advice wouold be greatly appreciated.

thanks in advance.

here is a link to the pics of the case. it is built with the Baltic birch Ĺ inch plywood.
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Old 9th August 2006, 04:32 PM   #2
infinia is offline infinia  United States
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Hi
Not much heat here. You won't be listening while charging, right? But the battery, if included, most probably will need some venting. So ventilation in the box couldn't hurt, some holes in the back. A few towards the top and bottom. Holes should be at least slightly larger in diameter than the thickness of the panel.
As always YMMV.
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Old 9th August 2006, 08:45 PM   #3
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Default sealed battery

the battery is a sealed lead acid, so no need to vent it right?
i found a little usb temperature logger, so i am going to tuck in
in the case for some time and see how it does.

thanks again. i am going to start placing the components inside
and should have something that i cna listen to by tomorrow.

fun hobby this is.
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Old 9th August 2006, 09:51 PM   #4
cpemma is offline cpemma  United Kingdom
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Wood is a good thermal insulator, it's going to get hot in there eventually even with a low-wattage source. A few holes underneath and in the upper back won't show but will allow a convection path out. It's also worth gluing a small heatsink to the chip to aid heat transfer away from the chip body. An LM3875 chip will run with the guts at 150C, but the Tripath chip is limited to only 85C.
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Old 10th August 2006, 03:36 AM   #5
infinia is offline infinia  United States
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Hi
link for sealed lead acid battery info
http://www.engineersedge.com/battery...id_battery.htm
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Old 10th August 2006, 07:22 AM   #6
AndrewT is offline AndrewT  Scotland
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Hi,
sealed lead/acid batteries and most low maintenance batteries are not designed for deep discharge duty. If used this way they have a short life.

If you intend running your charger when the amp is off and then turning the charger off when running the amp, this this is exactly the situation that shortens the life of an inappropriate battery.
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Old 10th August 2006, 02:38 PM   #7
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Default i'm confused about battery now.

your post has made me second guess my battery selection.

I am planning on just using this amp for no more than 1-3 hours at a time, maybe only on the weekends when I have time to sit down and listen to some music.

the battery I have chosen is a 12 volt 7ah sealed lead acid battery commonly found in home alarms. when I am not listening to the amp, I am going to turn on the charging circuit which is a smart charger that turns off when the battery is fully charged (battery tender)

so the battery probally will generally always be held at a 80-100% charge at that time.

is that bad for the battery? I donít ever think the battery will ever be fully drained or close to being fully drained.

thanks again for your answers.

is there a better battery I should be using for this project?
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Old 10th August 2006, 03:01 PM   #8
infinia is offline infinia  United States
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Sealed Lead batt, are OK for this purpose just make sure that under operation the capacity is not depleted beyond 50%. Sealed are expensive and normally lead acid deep discharge are used as an economical but higher maintenance option. Sealed are used in applications of energy storage for electrical equipment/appliances in boats for example were space and mounting is a concern.
Keep in mind that depending on charging profiles that max capacity reaches about 90%.
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