Question on Running 2 Batteries

[9632587410]

Hi<br /><br />I own a 14.6 Princecraft with a 1998 Yamaha 30 HP oil injected/electric start 2 stroke (long shaft) . I just got it and I was wondering what (if possible) is the safe way to connect my trolling motor battery (up front) so the engine charging system charges both batteries <br />( starting & trolling battery) ? Can this be done ? Thanks for any help .<br /><br />Jeff

 

[tesmel]

Re: Question on Running 2 Batteries

Yes it can be done by connecting the two batteries in parallel,the problem is that the two batteries now become one, so when trolling both batteries are being drained.You do not want this to happen because if the batteries run down then you cannot crank your motor.<br />To solve this problem you need a device called a Phase Charger, this piece of electronic device will connect the two batteries in parallel so that they both charge when the engine is running, but when the engine shuts off it disconnects(isolate) the two batteries, this is all done automatically you do not have to do a thing.<br />Since I am an electronics technician I have designed my own and it works great. If you are interested in getting one for yourself I can make one for you with complete detailed instructions on how to install it, for $49.00Cdn + shipping.<br />E-mail me at tesmel@sympatico.ca if you have any questions.<br />Terry

 

[petryshyn]

Re: Question on Running 2 Batteries

I'd advise against it. The troller battery is a deep cycle battery and is commonly drained to a low state of charge. The O/B charging system can be overheated by outputting its maximum output for long periods of time. Two things will result. The troller battery won't get fully charged, and charging system damage may result. <br /><br />Recharge the troller on shore......

 

[Boatist]

Re: Question on Running 2 Batteries

Schematic makes a good point but a lot depends on your motor and how you use your boat. Some Yamaha motors motors have two charge outputs. One regulated to charge the starting battery and a unregulated one that can be used for lighting or battery charging. If your has that I would use lighting one for trolling battery.<br />also a lot depends on how you use it. If you launch make a 5 min run acrossed lake and troll all day with the electric then run home you are not going to make much difference in terms of charging your trolling motor battery. On the other hand on a 14 foot boat you probably do not have a 50 lb thrust trolling motor. You might hook it up with a battery isolator this will keep one battery from running down the other but will tend to charge weakest battery more. If you been trolling all day that will be your trolling battery, so starting battery may not get much charge. With a 30 HP motor it will probably only charge around 12 amps. Also keep in mind a big trolling battery like group 27 when run down charging at 10 amps would take about 15 hours. If you want to try it anyway I would use a battery isolator so one battery can not run down the other battery and then I would use a second diode from the isolator leg that goes to the trolling battery. This will do two things It will reduce voltage to the trolling battery by about 7/10 of a volt. This will allow charge battery a better chance to charge first and also reduce load on you alternator of course the trade off is trolling battery gets less charge. One thing I would not do is use any kind of relay system that connect the batteries together when running because this type system can discharge the starting into the weak trolling motor battery. Good luck and let us know what you do.