I-Pilot battery connections

For over 14 years my autopilot was connected to two marine batteries, one of which was a dual purpose deep cell/starter to create 24 volts. Worked very well any many of you have done the same. I recently purchased an I-Pilot with Universal Sonar with the following warning: Must not be connected to any device that links the trolling motor batteries to the starting battery. -Using the the starting battery to power the trolling motor can cause corrosion and/or damage to the trolling motor and void warranty.

Are they being overly protective of their warranty or is their something anyone could tell me that would support their warning? I really don't have convenient room for a third battery.

Re: I-Pilot battery connections

It doesn't matter how long this practice has been used -- it is a bad idea, especially in a 24 volt system. You need to understand that the moment an engine is bolted to an aluminum hull the hull is now grounded via the engine block and negative battery cable to the starting battery. Should inadvertently use the wrong battery as the negative side of the 24 volt system you can toast electronics. So no -- this is not a cover their butt situation. It is to cover yours. Get another battery and wire this thing properly. Even if you have a glass boat, wiring accessories like radios, fishfinders and any other 12 volt accessories to the incorrect battery creates a potential ground problem.

Re: I-Pilot battery connections

Thank you for your insight. So if I understand you correctly, this battery configuration wired correctly should not damage the motor or the electronics...rather it lends itself to greater risk.

Re: I-Pilot battery connections

It lends itself to a much greater risk than one realizes. A dead short in a 12 or 24 volt system makes an a great arc welder and electronics destroyer. As I said, some folks use all sorts of creative wiring and some get lucky. Others not so much. Using two different styles of batteries in a 24 volt system means the system likely has two different battery capacitities so the troller does not operate as long as it would if you had two identical batteries. Because of this difference it is very likely the starting battery will become discharged before the deep cycle so it can leave you stranded. Since you are using the starting battery in the 24 volt system, it is the only one that is being charged by the engine. I must then assume you have an on-board charger just for the deep cycle or that you use a separate portable charger for it. How many more reasons do you need before you stop tempting fate. Keep an eye on this forum as I am in the process of creating a series of diagrams that illustrate how two and three battery systems can get people into serious and very expensive trouble.