Go to a battery test centre. They have a 500w tester
35amp test unit?
- 8th February 2012 08:32 PM #1browningbuck
35amp test unit?
well i am trying to build a 35Amp test unit. the idea is a 12V battery will be hooked up for max of 5 sec at a draw of 35A. this is a fairly large draw and i do not know what has a 420Watt device i can use? the power doesnt need to be used. it can be dissipated as heat, or light or... what ever. it is to test the internal connections of the battery to insure that all connections have been tested for QC reasons.
any ideas would be greatly appreciated.
Brian
- 8th February 2012 09:13 PM #2colin55 0
- 8th February 2012 09:31 PM #3browningbuck
yes i understand that but i doubt i can go there daily and test units hahahah.
0
- 8th February 2012 09:39 PM #4tcmtech
Just use three large 1 ohm resistors in parallel. That would give you a .333 ohm equivilant which would draw 36 amps at 12 volts.
Given the short duty cycle three 50 watt heat sink mountable type resistors would have no problem taking the momentary loads. Typicaly they have 10X surge wattage wattings as well so dumping roughly 150 watts into each for 5 second bursts would not bother them one bit.0"Sometimes genius is simply having the ability to see and understand the obvious. " -- tcmtech
"I didn't get to the point of knowing all that I do know by believing that I already know everything." -- tcmtech
- 8th February 2012 09:52 PM #5browningbuck
okay that seem simple enough! but im curious if the draw would be a stable 450Watt (like you are describing).. something is bothering me on the idea and i dont know what it is? you may have to walk me through it sorry...im thinking basically im at 1ohm system with 150 watt (draw 3 parallel 50W resistors) but this seems like the short across the three resistors are going to keep rising in draw until they burn (obviously they are designed to dissipate large amounts of energy, but this seems less accurate than what im after)
im not in any way saying your idea is wrong, just trying to understand it. thanks0
- 8th February 2012 09:54 PM #6ronsimpson
I made a 12 volt test load using car headlights.
0
- 8th February 2012 10:03 PM #7browningbuck
yeah that was what i was thinking about, but i guess that would be 8X 55w laps.... maybe its what i do? im waiting on tcmtech. i like his idea, just trying to figure out if its stable for testing say 100 batteries over a few hours?
0Last edited by browningbuck; 8th February 2012 at 10:03 PM.
- 8th February 2012 10:09 PM #8ronsimpson
Head lights are available in most countries. 450 watt resistors are hard to find.
If you choose resistors you could put them in a bucket of oil or water for a heat sink. (water is non conductive at 12 volts) I have used mineral oil, transformer oil and motor oil.0
- 8th February 2012 10:55 PM #9Reloadron
Along the lines of tcmtech's suggestion you could use three of these at about $5 USD each or maybe six of these. The latter able to last longer before getting hot. There are also solutions like using 12 volt heater elements along these lines but as can be seen, that gets costly. Also keep in mind the wire used to and from the load. AWG 10 will give you 30 Amp service and I would opt for AWG 6 to avoid IR loss and heating.
Ron0Please do not PM me with forum related questions. Let's keep things in the open forum. Thank you.
- 9th February 2012 01:48 AM #10ronsimpson Time to pick on Ron.
Originally Posted by Reloadron 
Using AWG 6 wire is good engineering practice. It seems strange to "avoid IR loss" when the goal is to have 400 watts of RI loss. lol
ron0
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