HXR Backup Battery "Dropping resistor" ?

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Joined: Mon Mar 30, 2020 8:10 pm

HXR Backup Battery "Dropping resistor" ?

Post by Bill_H »

I bought a Velocity with a single HXR installed, and I've been going through all of the configuration and understanding it's connections.
There is a backup battery installed.It is connected like this:

From the Positive terminal of the main battery, a thin wire (18?) runs to a big dropping resistor (25w1d2, apparently a 1.2 OHM 25 WATT) then to the positive terminal of the backup battery.

Why would this arrangement have been made? It would not prevent back current to the main battery and seems to ensure that the backup battery charges to a lower level than the main battery. Perhaps as the backup slowly charges it draws less and less current and the resistor becomes no factor? Does anyone else connect their backup battery like this? Issues?

Bill H.
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Joined: Tue Dec 11, 2012 12:11 am

Re: HXR Backup Battery "Dropping resistor" ?

Post by GRT_Jeff »

That's it? And it's just an ordinary battery? My guess is it's there to charge the backup battery and limit the charge current, or limit the total current to the backup bus, but I would also expect a diode or a switch or two. Since it's just a resistor, the voltage drop will be proportional to the difference in voltage, so the voltage can equalize as long as the batteries can hold the same voltage. Normally you would only charge a backup battery when at least the master is on and ideally the alternator is working, so normally there is a switch/contactor or an automatic charge circuit.
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