Adding a 3rd battery to run 24v trolling motor

[general south]

I currently have a dual 12 v battery setup running a perko switch that allows to select battery 1, 2, all, or off. I want to add a 3rd battery and run that in series with battery 2 to have 24v to run to trolling motor. I am going to attach 2 images to this post that represent the schematics of current setup and future setup. I just want to make sure Im not going to inadvertently put 24v through my electrical system or fry anything. Thank You

 

[fishrdan]

Looks good to me as the bottom (0>12V) battery is connected to the switch, not the top (13>24V) battery.

 

[general south]

Thank you fishrdan, my other option would be to disconnect the com going to my outboard/accessories before connecting that 3rd battery and putting my multi meter to it while switching the selector switch to 1, then 2, then all to see what the voltage is doing. With that setup, In order to charge the other 2 batteries I will probably put a switch to disconnect / isolate them and throw on the trickle charger/maintainer

 

[fishrdan]

Checking the switch with meter before connecting everything is a good idea, but you could have the batteries wired wrong and still read 12V on the switch. Just make sure you have the batteries wired as shown and you'll be A-OK.

Most modern multi-bank onboard battery chargers have independent outputs, so you don't have to break the series jumper while charging the batteries. Just permanently connect the charging leads to the battery while leaving everything else in place, then you only need to plug the charger's 120V cord into an extension cord to charge. The cost of an onboard charger is money well spent, one of the best things I added to my boat.

 

[hondam]

that setup would not be accepted by abyc or nmea regulations. the prohibit the mixing of 12 and 24 systems without a voltage converter which are expensive. if everything is in good condition and wired correctly it shouldnt cause any issues but will cause reliability and corrosion issues down the road thats why they regulate against it.

i would be especially cautious in an aluminum boat. ive seen one that was eaten from the inside out with corrosion and the owner didnt notice until it was to late.