I have recently installed the 12V DC-DC Orion Isolated Smart charger to my boat. This was to allow my alternator to be connected to my lithium ion house battery. Since connecting this device I’ve been monitoring the voltage closely as I have detected a problem with my alternator overcharging. My issue is that I am noticing the Victron is often giving me incorrect voltage values for the output (lithium ion) battery. It will consistently tell me the battery is at 14.3 v when I’m seeing the voltage on my voltmeter and pre-installed boat voltage meter at a different value (I.e. 13 v). Can someone explain this discrepancy?
Prime example of voltage drop across cabling. Also check for bad connections.
At which current do you see this, whats the cable crossection and distance from orion output to the battery terminals, which orion exactly are you using?
The Orion is very close to the battery (less than 0.5 metre) and I have the 30 amp. I’ll do some more testing to see when I’m noticing the biggest discrepancy, but I can’t imagine voltage drop being the issue. I’m using 10 mm cable. The only thing I can think of as maybe impacting the system is I’m running the alternator directly to a battery isolator. From the isolator one cable goes to my lead acid for the starter battery which then connects to the Victron and then my house lithium ion is connected to the output of the Victron. The second output of the isolator goes to the lead acid battery for my anchor winch. Maybe the isolator is causing a large enough resistance? The lead acid is being measured correctly by the Victron though so it seems unlikely.
How do you tell what current is occurring from the alternator? I have a voltmeter but only capable of measuring up to 10 amps.
The key to working this out is not to rely on different voltmeters, but to use a single multimeter and measure the voltage at the mppt terminals and the battery terminals during charge. The difference is should be 0.5V max, ideally less.