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Originally Posted by Gnarvan
Quick question about battery isolators.
It's my understanding the big difference between a battery isolator system and a relatively simple relay is the isolator has a diode in the system. The purpose of the diode is to keep your house or aux battery from draining back into your starting battery if the starting battery fails. Does the battery isolator system serve any other function?
Just trying to increase my understanding of why people drop extra $$$ on an isolator.
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The term Isolator or separator are really the same thing, but one usually see's isolator used with the diode based units. These units were relatively convenient in that they did not to be switched on or off. The diodes only lets the current flow in one direction. A draw back of the diode isolator was that you have a voltage drop caused by the diode. This would prevent you from ever charging the house battery up to full voltage (if only using the vehicle charging system).
The term separator has been used with units like the Surepower 1315 or 1314. They are really just a big solenoid but have some integrated circuits to monitor the voltage of each battery for disconnect and connecting. The term "smart" is usually used in their marketing terminology at some point. The heart of the unit is the high power relay, "solenoid", "DC Contactor". Obviously for battery circuits you may need a pretty hefty relay, 200 amps is not uncommon. Of course these need to be picked on, so when engaged you are always using up some power. A relay used for this application would need to be rated for continuous duty. One draw back of high power relays is the wetting current needed to keep the contacts clean. They will become pitted and build up a contact resistance. One of the things to look for in a high power relay what the contacts are made of, in this case you would prefer to get something with a silver alloy as apposed to just copper.
Another term for the smart separator is "ACR" automatic charging relay. Again these are pretty much the same thing. Blue Sea makes a few "ACR's one of them uses a Magnetic Latch Relay the Blue Sea 7620. The big difference of the Magnetic Latch relay is that it does not use all the continuous power that a continuous duty relay does. On a normal relay it does not really matter what which side of the coil has positive or negative. . With a magnetic latch relay the plunger is engaged and a stop will swing into place and keep it closed. To open it you provide the voltage the opposite polarity and the plunger engages and the stop is pulled out of the way.. The polarity of the magnetic stop is based on the same coil inputs. The input to the coil is momentary and thus can not be used with a simple switch.
There are other versions using high-Power FET's and such, but all in all they are supposed to do the same thing. I have personally removed the so called smarts from Sure Power unit and just use the Trombetta Relay wired into my run circuit. The van is running the batteries are combined, it is off they are disconnected. I also have a Blue Sea 6007 Switch wired in parallel to the relay. If the relay fails on a trip I can manually change it. I believe it to be a cleaner setup.
Sure the "Smart" relays will let you charge the van battery while you are plugged in and all that. With out a doubt the dumbest idea was the "start assist mode on the Surepower unit 1315"
sorry for the thread jack.
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