Battery wiring advice please

[billywhizz]

can anybody advise me how to correctly connect my leisure battery to the charging circuit, i have mercruiser 485 engine, the main battery shows 14.6 volts across the terminals with the engine running, when i do the same test on the leisure battery it reads 12 volts and runs down, the leisure battery is brand new and if i disconnect the live terminal and test between it and ground with the engine running only reads 7.6 volts? if i were to run a cable from each terminal on the engine battery to the same terminal on the the leisure battery would this damage the alternator?

 

[Silvertip]

Re: Battery wiring advice please

No it will not damage the alternator. So where does the wire come from that you are currently using to charge the leisure battery? If both terminals of the leisure battery are not connected directly to the engine battery the leisure battery will not be charged by the engine alternator. A dual battery switch is normally used to accomplish this and provide the versatility that a direct connection cannot. When two batteries are connected in parallel and one of the batteries is weaker than the other, the weak battery will suck the life out of the good battery until the two are equal. A dual battery switch provides the option of starting the engine and charging BAT 1, BAT 2 or BOTH and it allows you operate accessories at anchor on BAT 1, BAT 2 or BOTH. The configuration is as shown below. All of the accessories on the boat except the bilge pump should be wired to the COM terminal on the switch. The bilge pump should be wire so it can be operated manually or with an automatic switch.

 

[billywhizz]

Re: Battery wiring advice please

Silvertip, Thank you for your time and patience, at last it is begining to make sense, as best as i can see the live wire from the leisure battery go,s through an isolator switch and then to a small metal box on the transom which i assume is the voltage regulator? not sure both batterys are wired through isolator switches,