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Using Our EFIEs on 24 Volt Systems

We've sold quite a number of our EFIE products to customers around the globe. The only continent we haven't delivered our products to is Antarctica. Therefore, there are times when our customers need to use our EFIEs with 24 volt systems, even though they were made for 12 volt systems. This article tells you how to make the conversion.

First of all, when I say "24 volt" or "12 volt", I mean nominal (in name only). 24 volt systems will actually run as high as 28 or 29 volts, and sometimes more. 12 volt systems run as high as 14 volts. In either case, when the engine is running and the alternator is supposed to be charging, the voltage has to be a little higher so that that charge will flow into the battery and charge it.

For our purposes, we don't care about these differences. The EFIE can run on voltage as low as 10 volts and as high as 18 or 20 volts. So, it doesn't have to be an exact 12 volts that it receives. Further, if its voltage isn't exactly correct, it will have no effect on how the EFIE operates. However, it can't take 24 volts for long periods of time without eventually overheating its voltage regulator. So we have to provide a simple circuit to get the voltage to the EFIE in a useable range.

We can do this with 2 resistors easily purchased from your local electronics store. You may have a Radio Shack in your city, but if not, these are standard resistor sizes so any decent electronics parts supplier will have them. If you can't find them locally in your home town, then you can usually order them from a parts house in your country.

Below is the schematic for how the resistors go together. Following that will be a chart that gives the resistor values to use for the different devices we carry. The chart will show the resistance in ohms. So when ordering them, you would order the amount of ohms from the chart below, but you must also specify 1/4 watt as the current rating. They should cost you a few cents each.


schematic

 

Device
A
B
Quad Digital EFIE Basic
270
2.7K
Dual Wide Band EFIE Basic
270
2.7K
Frequency MAP Enhancer (New)
165*
2.7K
Analog EFIEs:
Single EFIE Deluxe
330
2.7K
Single EFIE Basic
330
2.7K
Single EFIE Circuit Board
330
2.7K
Dual EFIE Deluxe
165*
2.7K
Dual EFIE Basic
165*
2.7K
Dual EFIE Circuit Board
165*
2.7K
All values are in Ohms
* 165 Ohm is not a standard size.  Use 2 x 330 Ohm in parallel.

The above values are for circuits that power only the EFIE device. If you need to power other 12 volt devices, this will draw more current. In these cases you will need to find new resistance values that will allow for the additional current, while keeping the voltage within a reasonable range.

For a good professional install, you should twist the wires together and solder them. You'll need to be sure they don't short out to the frame of the vehicle, or any other metal, so will need to cover them well with heat shrink or electrical tape. Its a very simple circuit that will allow you to use EFIEs with 24 volt systems.

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