Split Charge Monitoring

hi guys
got a bit of a confuser-although Im not overly electrically minded!
I have a TMax split charge which charges via a solenoid & control box.
I use it on my crank battery & my aux battery.Both batteries charge fine-I have circuit tested the output from the solenoid to the aux battery & it is present when the solenoid kicks in.
However..i have installed a National Luna dual battery monitor-4 wires, 2 pos & 2 neg wired directly to the relating battery terminals as instructed.
Readings are fine for the cranking, showing battery state in volts & charging volts.But for the aux battery, the display only shows battery state & not the charge rate.
I have "jumped" the circuit & temporarily wired it so that the monitor was connected to the output of the solenoid for the aux battery but no change.
Could the problem be that the crank battery Pos terminal is connected directly to the alternator so the monitor can detect the charging rate but the aux battery is not-although i thought my jump wire would have cured that?
I may try connecting the aux pos lead from the monitor ALSO to the feed into the charging solenoid. This may give the charge output of the alternator BUT-is that necessarily the charge rate the aux battery is accepting?
Anyone electrically minded gratefully received!!!

i have the exact same split charge in my defender.
i have connected a digital volt meter to each battery
this gives me the reading i am after and both are generally around 14.4v
when im winching you can easily see the effect and when the split charge kicks in you can hear it and also see it on the guages

Swap both circuits of the meter round, ie. check that the second charging meter works on the main battery

will try that tomorrow, cheers

Faulty earth cable!!

wiltshire landyman said:

i have the exact same split charge in my defender.
i have connected a digital volt meter to each battery
this gives me the reading i am after and both are generally around 14.4v
when im winching you can easily see the effect and when the split charge kicks in you can hear it and also see it on the guages

Click to expand...

would you please be kind enough to take a picture of volt meters as i am also looking for a twin display many thanks drew

Blue sea systems offer some great products here is a volt meter which will read three different batterys. DC Voltmeter Panels - Blue Sea Systems

thanks will look int it