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Current Load Calculation


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I'm in the process of making wire harness changes that include upgrades and additions that will increase the total current requirement from the alternator/battery.  Ultimately, besides wire gauge changes, the alternator will need to be upgraded.  

For this calculation, I started with the belief that winter and summer might be very different.  Turns out, maybe not so much. 

Loads are computed at minimum charging voltage: 13.5 (arguably).

Lighting current is based on using incandescent bulbs which also will see "persistent" and "transient" use.  The persistent load comes out to about 17A, while transients total around 16A.  I took a WAG and chose 25A for both.

Some other transient loads, such as power windows, are not included. 

Audio equipment is not included.

The highest load case in this example is 134A.  If you believe in safety factor, and I most certainly do, it looks like I'll need at least a 150A alternator.




Has anyone successfully used an alternator rated in the 150 - 200A range?

Edited by ETI2K
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