Dual Battery system

[diggerglp]

If you add the dual batteries, do you have to get a bigger alternator to handle the charging so it doesn't burn up the OEM alternator. The boat is a 2000 21V 350 Tournament Ski Mercruiser.

[ajholt7]

You should be just fine if you are only doing a dual battery setup.

[kko]

no

[light200]

naa, you'll be fine.

[chpthril]

Simply adding a 2nd battery to have as a backup starting battery will not phase the alternator at all, but, if you are adding a "house" battery to power a stereo system, and that battery will be deeply discharged weekend after weekend and relying on the alt to replenish it, then yes, it will accelerate the wear on the alternator.

So it really depends on how its gonna be used, but I dont see you toasting and alt.

[diggerglp]

Another question on the batteries

The 2nd battery is for exactly what you said and that being to power the new amped up stereo system. I was going to use a deep cycle battery with an isolator switch so it will be getting drawn down alot when the boat is not running so will the stock alternator need to be bigger to recharge this battery and the starting battery when they are both in need of charging.

[laserfish]

Listen to Chp and buy what he recommends. It will save you a lot of headache and he is a wealth of info and help.

[chpthril]

The 2nd battery is for exactly what you said and that being to power the new amped up stereo system. I was going to use a deep cycle battery with an isolator switch so it will be getting drawn down alot when the boat is not running so will the stock alternator need to be bigger to recharge this battery and the starting battery when they are both in need of charging.

Keep the "house" battery isolated when the engine is off and use a true battery charger or install a dual-bank charger to recharge the "house" and maintain the "starting" battery.