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Old 07-13-2011, 08:03 PM   #8
FlyWright
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City: California Delta
Vessel Name: FlyWright
Vessel Model: 1977 Marshall Californian 34 LRC
Join Date: Apr 2008
Posts: 13,728
RE: What happened? House batts went dead

I'm not sure how the Blue Sea ACR works, but my combiner only closes after the charging battery reaches 13.2V for several seconds. Here are some specs I found on a Blue Sea website. (http://bluesea.com/category/2/productline/overview/387) Not sure if it's the same as your model.

Combine (30 sec.) 13.6V @ 12V DC
Combine (90 sec.) 13.0 V @ 12V DC
Open (10 sec.) 12.35V @ 12V DC
Open (30 sec.) 12.75V @ 12V
Open High 16.0V @ 12V DC

I'm not sure how your alternators and switching is wired, so it's hard to diagnose.

On my former setup, the alternators charged the batteries through the start cables and the Perko switch. If the Perko was on 1, only the house batt got charged. If the Perko was on 2, only the start batt for charged. I'd start in the 2 position, then switch to all to charge both banks while underway. Then when I got to my destination, I had to remember to select 1 to avoid draining the start bank while on the hook.

I changed this setup recently so that each alternator now charges its own bank via direct cabling. A combiner is present to allow one alternator to charge both banks, if needed. The loads are completely split and there is no need to mess with the Perko switches unless i need to tie the banks together due to a low start bank.

I have had problems in the past of one alternator not coming online unless I revved the engine above idle RPMs. Then the alternator charges and the tach comes to life. Maybe you had something similar happen? Maybe a slipping or broken alternator belt? Do you have ammeters? A constant scan of the voltmeter will also help in identifying a problem. You should see 14V+/- when the alternator is charging properly.

The way it was explained to me, the voltage difference between the alternator and the battery (i.e. 14V minus 12V) is kind of like the size of a pipe filling a reservoir. The larger the pipe, the easier it is to pump water into the reservoir. The amperage is like the flow of water going through the pipe. If you have a small difference between the charge voltage and the battery, there won't be many amps flowing into your battery. If your alternator voltage is dropping (i.e. bad voltage regulator), you won't be able to charge the battery very efficiently. The ammeter will allow you to monitor the flow of amps into the battery. A volt meter will give you a look at the size of your pipe. ;-)

I just installed a Xantrex LinkPro battery monitor to help me watch these parameters and the batteries' state of charge. It will help me to keep the batteries healthier and more fully charged so I do not deplete them unknowingly. I'm hoping it also helps me see potential problems before they reach crisis level.

After receiving a charge, the batteries will show high voltage, but this can be just a surface charge. If you place a light load on the batteries (5 amps?) for about an hour, you'll get a better look at the true battery voltage. Checking the specific gravity of each cell can also help ID a bad battery. Usually one cell gives out before the others. If they are all weak, you might have more of a charging problem than a battery capacity problem.

Check all battery connections and grounds.
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