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We have just purchased a 2000 Catalina. The engine charges the house batteries (which are also used to start the engine). The starting battery is only charged when attached to shore power and would only be used in an emergency (house batteries die).

My first inclination was to rewire the starting battery so that it, too, is charged by the engine. When I saw how much this was going to cost, I reconsidered. The PO did a superior job of upgrading just about everything on the boat - had the current setup (sorry about that) proved inadequate, I'm sure that he would have changed it.

We'll generally be at a dock, and even when cruising, we'll go to a marina at least once a week.

Can you think of any reason that I should have the starting battery setup changed so that it is charged by the engine?

Thanks,
mrmac
 

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If the batteries are the same type (i.e. wet lead) put an "echo charger" on the house bank. That will automatically connect it to the starter battery and recharge the starter as well, once there is spare power to do so.

Also known as a West Marine (aka Yandina) Battery Combiner. Real simple, real reliable.
 

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We have just purchased a 2000 Catalina. The engine charges the house batteries (which are also used to start the engine). The starting battery is only charged when attached to shore power and would only be used in an emergency (house batteries die).

My first inclination was to rewire the starting battery so that it, too, is charged by the engine. When I saw how much this was going to cost, I reconsidered. The PO did a superior job of upgrading just about everything on the boat - had the current setup (sorry about that) proved inadequate, I'm sure that he would have changed it.

We'll generally be at a dock, and even when cruising, we'll go to a marina at least once a week.

Can you think of any reason that I should have the starting battery setup changed so that it is charged by the engine?

Thanks,
mrmac
If a week is the longest you are away from the dock this is a non-issue.

Also you should still have a parallel switch or the BOTH setting on your battery switch that will charge both banks at the same time....
 

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Why not connect your alternator to an isolator then run one or 2 lines to your house and another to your start from the isolator depending how many banks it can run . I have 3 seprate power systems on my boat house bank which is 4 6v golf cart batteries starter which is 12v car and a deep 12 for the windlass
 

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Isolators similar to the one below have a .7 volt drop. That means if the alt or other device is set for 14.4 your battery is only getting 13.7 volts, minus any drop from connections. Not good.

A better choice is either an ACR, an Echo Charge, or a Duocharge.
 

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Isolators similar to the one below have a .7 volt drop. That means if the alt or other device is set for 14.4 your battery is only getting 13.7 volts, minus any drop from connections. Not good.

A better choice is either an ACR, an Echo Charge, or a Duocharge.
+1 diode Isolators went out when cave men still made dinosaur saddles...

It's not just the voltage drop, most smart charging sources today look for a min safe voltage in order to turn on. With a diode isolator there is no idle voltage on the input stud......
 
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