battery charger not happy with a long wire connection

Thread Starter

operator_error

Joined Dec 13, 2020
2
I have a Chinese battery charging control module (XH-M603) that I'm trying to use as a float charger for a 12v SLA battery. The problem is that the module only works correctly when it is connected close to the battery using short leads. When I connect the module using 30ft of wire (which is how I intend to use it) the module doesn't sense the battery correctly and won't output any current. The total resistance of the 30ft of wire is only about 0.6 ohms but that seems to be enough R to confuse the module's charging circuit.

Is there a simple way I can offset the effect of the long wire so that the module thinks it's close to the battery? -Thanks
 

Thread Starter

operator_error

Joined Dec 13, 2020
2
I'm not exactly sure of the gauge (probably 22-24?). The wire I'm using is 4-conductor solid core RJ-11 phone cable that I had laying around in the garage. I combined the wires from the cable, two for positive and two for negative. The cable is in good condition and has no splices. I've run a few amps through this cable previously with other projects and in this case the charger would be used for float current, probably 500mA max. That doesn't mean I don't need a bigger wire though!

Yep, that's the module in the video - works great when it's positioned close to the battery.

I have some Cat-5 solid core cable laying around which could yield a little heavier gauge with the wires combined. The wires are twisted inside the cable though.. which, now that I think about it, is also probably going on inside the RJ-11 phone cable that I used. Do you think the twisted wires could have anything to do with confusing the module, or is it just a matter of ordinary resistance?

I expected to have to adjust the charger's voltage to allow for the voltage drop caused by the long wire, but I didn't think the wire would completely confuse the charger. The charger module does display the voltage coming from the battery but doesn't seem to "sense" it and just won't put out any current.
 

Dodgydave

Joined Jun 22, 2012
9,837
There's your problem the wrong cable type, you need heavy duty cable like 4mm as it's taking heavy current and will drop voltage with smaller guage wire.
 
Top