Electrical Reference

IDEA! Bike-specific information can be found in ST13.ElectricalReference.

Useful Articles

The Boat Owners Association of the US (BoatUS, http://www.boatus.com) has an excellent set of how-to guides on various boat-related subjects including a number on electrical systems. Just about everything in those articles is relevant to motorcycles.

ALERT! WARNING: The ampacity figures in these articles are for marine-grade cable, which has insulation rated for 105°C. Conventional cable is rated for much less and will carry much less current before the insulation fails. Marine-grade cable is an excellent choice for use on motorcycles because it does a better job resisting water, salt, oil, fuel and other substances you might find on your bike.

Wire and Fuse Selection

Wire of a certain size is only capable of carrying a certain amount of current (measured in Amps). This spreadsheet (MS Excel, 12K) will allow you to calculate the minimum wire size required for a circuit of a given length carrying a given amount of current.

ALERT! WARNING: The warning about about marine-grade cable also applies here.

Blue Sea Systems has a useful chart with similar information: http://assets.bluesea.com/files/resources/reference/20010.pdf

Watts to Amperes at 12 Volts

The formula for this is Amperes = Watts / Volts. To go the other way, Watts = Amperes * Volts.

Watts Amps Watts Amps Watts Amps Watts Amps Watts Amps Watts Amps
1 0.08   51 4.25   101 8.42   151 12.58   201 16.75   251 20.92
2 0.17   52 4.33   102 8.50   152 12.67   202 16.83   252 21.00
3 0.25   53 4.42   103 8.58   153 12.75   203 16.92   253 21.08
4 0.33   54 4.50   104 8.67   154 12.83   204 17.00   254 21.17
5 0.42   55 4.58   105 8.75   155 12.92   205 17.08   255 21.25
6 0.50   56 4.67   106 8.83   156 13.00   206 17.17   256 21.33
7 0.58   57 4.75   107 8.92   157 13.08   207 17.25   257 21.42
8 0.67   58 4.83   108 9.00   158 13.17   208 17.33   258 21.50
9 0.75   59 4.92   109 9.08   159 13.25   209 17.42   259 21.58
10 0.83   60 5.00   110 9.17   160 13.33   210 17.50   260 21.67
11 0.92   61 5.08   111 9.25   161 13.42   211 17.58   261 21.75
12 1.00   62 5.17   112 9.33   162 13.50   212 17.67   262 21.83
13 1.08   63 5.25   113 9.42   163 13.58   213 17.75   263 21.92
14 1.17   64 5.33   114 9.50   164 13.67   214 17.83   264 22.00
15 1.25   65 5.42   115 9.58   165 13.75   215 17.92   265 22.08
16 1.33   66 5.50   116 9.67   166 13.83   216 18.00   266 22.17
17 1.42   67 5.58   117 9.75   167 13.92   217 18.08   267 22.25
18 1.50   68 5.67   118 9.83   168 14.00   218 18.17   268 22.33
19 1.58   69 5.75   119 9.92   169 14.08   219 18.25   269 22.42
20 1.67   70 5.83   120 10.00   170 14.17   220 18.33   270 22.50
21 1.75   71 5.92   121 10.08   171 14.25   221 18.42   271 22.58
22 1.83   72 6.00   122 10.17   172 14.33   222 18.50   272 22.67
23 1.92   73 6.08   123 10.25   173 14.42   223 18.58   273 22.75
24 2.00   74 6.17   124 10.33   174 14.50   224 18.67   274 22.83
25 2.08   75 6.25   125 10.42   175 14.58   225 18.75   275 22.92
26 2.17   76 6.33   126 10.50   176 14.67   226 18.83   276 23.00
27 2.25   77 6.42   127 10.58   177 14.75   227 18.92   277 23.08
28 2.33   78 6.50   128 10.67   178 14.83   228 19.00   278 23.17
29 2.42   79 6.58   129 10.75   179 14.92   229 19.08   279 23.25
30 2.50   80 6.67   130 10.83   180 15.00   230 19.17   280 23.33
31 2.58   81 6.75   131 10.92   181 15.08   231 19.25   281 23.42
32 2.67   82 6.83   132 11.00   182 15.17   232 19.33   282 23.50
33 2.75   83 6.92   133 11.08   183 15.25   233 19.42   283 23.58
34 2.83   84 7.00   134 11.17   184 15.33   234 19.50   284 23.67
35 2.92   85 7.08   135 11.25   185 15.42   235 19.58   285 23.75
36 3.00   86 7.17   136 11.33   186 15.50   236 19.67   286 23.83
37 3.08   87 7.25   137 11.42   187 15.58   237 19.75   287 23.92
38 3.17   88 7.33   138 11.50   188 15.67   238 19.83   288 24.00
39 3.25   89 7.42   139 11.58   189 15.75   239 19.92   289 24.08
40 3.33   90 7.50   140 11.67   190 15.83   240 20.00   290 24.17
41 3.42   91 7.58   141 11.75   191 15.92   241 20.08   291 24.25
42 3.50   92 7.67   142 11.83   192 16.00   242 20.17   292 24.33
43 3.58   93 7.75   143 11.92   193 16.08   243 20.25   293 24.42
44 3.67   94 7.83   144 12.00   194 16.17   244 20.33   294 24.50
45 3.75   95 7.92   145 12.08   195 16.25   245 20.42   295 24.58
46 3.83   96 8.00   146 12.17   196 16.33   246 20.50   296 24.67
47 3.92   97 8.08   147 12.25   197 16.42   247 20.58   297 24.75
48 4.00   98 8.17   148 12.33   198 16.50   248 20.67   298 24.83
49 4.08   99 8.25   149 12.42   199 16.58   249 20.75   299 24.92
50 4.17   100 8.33   150 12.50   200 16.67   250 20.83   300 25.00

-- MarkFeit - 24 Sep 2005
Topic attachments
I Attachment Action Size Date Who Comment
wire-sizing.xlsxls wire-sizing.xls manage 13 K 03 Sep 2006 - 13:50 MarkFeit Wire Sizing Calculator
Topic revision: r11 - 27 Mar 2016, MarkFeit
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