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Old 14-04-2012, 00:34   #16
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Location: On board in Alanya, Turkey
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Re: Blue sea automatic charge relay

Originally Posted by goboatingnow View Post
if your starter and house are similar batteries, then a really is fine , otherwise a diode splitter is better.
Split Diodes were the first automatic solution but they have a voltage drop of 0.7 volts across each diode, maybe double this at high charge currents. This causes a huge power loss, but this loss can be compensated for by having regulators that sense the service battery voltage and boost the charger output. This can produce the right voltage at the service battery but can produce too high a voltage on the starter battery. Consider a heavily depleted large service bank - and an almost full smaller starter battery. The voltage drop across the diode feeding the service bank increases with the current so may well reach 1.4 volts or more. The alternator senses the voltage at the bank and ups the output by 1.4 volts to say 15.8 volts. The voltage drop across the diode feeding the starter bank is only 0.7 volts because the smaller service bank is taking a much smaller current. So the starter bank is sitting at 15.1 volts for maybe several hours! This is almost an equalizing charge - so not very good for any sealed, Gel, and AGM batteries.

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Old 17-04-2012, 07:26   #17
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Re: Blue sea automatic charge relay

thanks guys!

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