I am wiring a IP65 Smart Shunt to my boat trolling motor batteries. I have 2-12 volt 100 ah Dakota Lithium batteries hooked up in series for a 24 volt setup. I have the ground from my trolling motor hooked to the LOAD MINUS side of the shunt. I have a negative cable hooked up to the BATTERY MINUS side of the shunt going to the Main negative terminal of Battery 1. I have a MID POINT cable hooked up to the positive post on Battery 1 going to the negative post on Battery 2. I also have the AUX (grey wire) from the shunt hooked up to the positive on Battery 1. Next I have positive wire from trolling motor and VBATT+ (red wire) hooked up to Main positive post on Battery 2. I know I should hook a positive cable from Charger Bank 1 of my 2 bank MINN KOTA PRECISION 12v charger to Battery 1 and the positive cable from Charger Bank 2 of my charger to Battery 2. Here is my question, Do I hook up both ground wires from the Charger Banks to the LOAD MINUS side of the shunt as my Victron instructions indicate OR do I hook up Charger Bank 1 negative cable to LOAD MINUS side of the shunt and the ground cable from Charger Bank 2 to Battery 2 negative post as I read in a Victron Community post from 2023 by pwfarnell because the MINN KOTA charger is 12 volt only and not 24 volt and has separate circuits? Could someone please clarify this for me?
Unfortunately this simply won’t work; you can’t use a SmartShunt to monitor charging of a 24v bank that you’re charging individually at 12v.
The simplest thing to do, usually, is just get a 24v charger so that you can charge, discharge, and monitor the bank at 24v.
Thank you so much for your reply. I just want to give you a few nuggets of information I have found searching this subject after your reply and please feel free to correct my assumptions or the information I have gleaned from the internet.
First: The 12 volt lithium batteries hooked up in series to make 24 volts are not ever recommended to be charged with a 24 volt charger because over time you will end up with uneven charge between the 2 Lithium batteries. To prevent this, battery manufacturers recommend charging the batteries individually with a Marine style charger like the one that I have that has separate banks on separate circuits.
Second: Reading Victron’s information supplied with the Smart Shunt, NOTHING is to be hooked up to the Main Negative post on Battery #2 other than the Negative cable to the Battery Minus side of the Shunt. That tells me that the Battery Charger Negative cable from battery #2 should be hooked up to the Load Minus side of the shunt sharing a common ground on Battery #2 with the charger Positive cable to the positive post on Battery #2. This should give battery #2 a full 12 volt charge from one bank of the charger. Then Battery #1 would be hooked up with the second bank of the Battery Charger with the Positive cable to the Positive post and the Negative cable to the Negative post which would give this battery a full 12 volt charge. If this bank’s Negative cable was hooked up to the Load Minus side of the shunt like battery #2, then the Battery Charger would be sensing a 24 volt system and would not work.
Third: Reading the Victron information, hooking up the Smart Shunt grey Aux. fused wire to the Positive on Battery #2 would give me a Midpoint Reading showing battery charge balance when I am not charging while the Smart Shunt red fused wire hooked up to the Positive of Battery #1 would read the charge state of battery #1.
Fourth: I saw a YouTube video of someone who did this exact same hookup as I just described to you a year ago with a Victron BMV-712. He hooked his 12 volt charger banks as I described above to his Lithium Batteries. Then have later did a follow up video and everything was still working perfectly and his batteries were maintaining an even charge.
Please point out any flawed information I may have posted here. I’ve just spent $1500.00 on 2 Lithium Deep Cycle batteries and really wish to get this right.