dump load question
By donald77777, Section Newbies Posted on Tue Feb 05, 2008 at 04:31:06 AM MST
which resistor is better ? or what ?

Hello everyone. I have looked over different dumploads on the site and have a basic idea of them. Now since I have some misc parts laying around I want to check with you to see if they will work. I have two resistors. one is a JURIA 25 watt 250 ohm J the other is a IRC 6907 2"d 2500 ohm 25 watt could I use these together ? or not ? any help would be appreciated. On a side note I am looking to build or buy (if cheap) a transfer switch that will disconnect my inverter at 50% battery charge. (whatever the voltage leve is can't remember of hand) Thank you once again.

dump load question | 3 comments (3 topical)

Re: dump load question (3.00 / 0) (#1) by donald77777 on Mon Feb 04, 2008 at 10:30:41 PM MST

edit forgot to mention the dump load is for a 100 watt wind turbine.

Re: dump load question (3.00 / 0) (#2) by commanda on Tue Feb 05, 2008 at 12:26:17 AM MST

Power = volts squared divided by resistance P = E^2 / R rearranging for R gives R = E^2 / P assuming a 12 volt system with a dump voltage of 14 R =  14 * 14 / 100 R = 1.96 ohms So no, neither of those 2 resistors is any good for what you want. Amanda

Re: dump load question (3.00 / 0) (#3) by SparWeb on Wed Feb 06, 2008 at 12:36:28 PM MST

This might help: These resistors are each rated at 300W, 2 ohms.  All in parallel have a combined resistance of 0.5 ohms. My system's voltage is 12V.  When fully charged, the voltage can be up about 14V, more than that when it's cold.  The max current is therefore: 15V / 0.5ohm = 30 Amps. Power dissipated is 450 Watts; more than enough for my windmill which furls at 200W. Your resistors must allow enough current to actually dissipate your 100W, at whatever battery system voltage you're using. Make allowances for the resistors getting hot - a thing on my to-do list.  My plywood wall is unprotected.  Fine while it's winter.  Must cover before summer. Steven Fahey

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