2 Batteries - 2 motors

[DaveO_VB]

Gents, I have two Honda outboards and two batteries with two switches "1-All-2-Off". My question is how should these be wired in order to Start & charge from any combination, i.e. Battery 1 starting both, engine 1 charging both, engine 2 charging both, etc?<br /><br />Secondly, could a charging loop be carried fwd from the engine (15')to the galley to charge a house battery while underway and what size wire would it take?<br />Thanks!

 

[Peter J Fraser]

Re: 2 Batteries - 2 motors

DaveO<br /><br />2 engines means: 2 x starting batteries, 2 x master switches, separate electrical systems with a 3rd master switch to parralel your starting batteries in the event that 1 of them goes belly up.<br /><br />I would install a 3rd battery for all your front end house and electronic requirements with an automated split charging system to keep the house battery charged. This battery also needs to have a master switch fitted so it too can be isolated as required.<br /><br />If you run both alternators into one battery you risk frying a voltage regulator and other electronics that your engines may have.<br /><br />Good luck<br /><br />Peter

 

[Peter J Fraser]

Re: 2 Batteries - 2 motors

Dave,<br />A few more thoughts on your question.<br />Wire up your 1st battery B+ to Terminal 1 on master switch.<br />From Master Sw Common post to #1 engine Starter motor.<br />Battery B- straight to Engine frame as per normal.<br /><br />Same connections apply for eng #2. e.g. Batt 2 B+ to Term 1 on #2 master switch. common post on switch to #2 starter motor.<br /><br />Connect #2 terminals on both master switches with the same size cable as the other leads. This is then your Bridge to join both batteries in parallel in emergency.<br /><br />Both Batteries also need to be joined together on the B- terminals to complete the circuit. (Separate cable)<br /><br />For Normal operations turn each Master Switch to Position #1 only.<br /><br />For Emergency starting turn master switches to #2 for the engine with flat battery and to "BOTH" on the engine with the good battery.<br /><br />I would ensure that the engine on the "Good" battery is running first before you attempt to start your 2nd motor.<br /><br />You can switch both master switches to position "BOTH" to start but if you have a faulty battery with an internal short you would risk killing your good battery as well.<br /><br />For all your other front end electrical demands you should use a 3rd battery for a separate power supply. This can be charged from either engine if you fit a diode controlled battery isolator. This can be wired in with a switchable input from your main batteries so you can alternate the charging requirements from either engine.<br />This 3rd battery will also require a separate master switch to isolate the accessory circuits<br /><br />Regards<br /><br />Peter