neubie Posted August 18, 2018 Share Posted August 18, 2018 The isolator shows alternator voltage on one side but house battery voltage on the other with engine running. This is the old solenoid type little cylinder. Can only assume the isolator is busted. What's the favorite replacement? solenoid or solid state? Quote Link to comment Share on other sites More sharing options...
WME Posted August 18, 2018 Share Posted August 18, 2018 Do you want good enough or do you want righteous? Isolators come as a basic solenoid type, copper contacts or an up rated design with silver contacts. Its $30 vs $90. The solenoid when new has almost 0 loss, but as it ages it loses more. The diode type have a built in fixed .7 v power loss. You need one of the 4 post isolator, the 4th post is for the exciter voltage These both work just like advertised. There a much newer design that does the same basic things. BUT it will allow the rv converter to charge the truck battery when your plugged in to 110v AC. This is one of the smart ones. https://www.ebay.com/itm/Victron-Cyrix-ct-12-24V-120A-Intelligent-Battery-Combiner/171934028788?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649 So you makes your choice and pays your money. Quote Link to comment Share on other sites More sharing options...
Gulfstream Greg Posted August 18, 2018 Share Posted August 18, 2018 2 hours ago, neubie said: The isolator shows alternator voltage on one side but house battery voltage on the other with engine running. This is the old solenoid type little cylinder. Can only assume the isolator is busted. What's the favorite replacement? solenoid or solid state? Verify that you have 12 volts at the smaller terminal with the ignition on. Hold your hand on the isolator and have someone switch on the ignition, there should be a heard and felt clunk. No clunk check to see that it is getting 12v on the energizer terminal. If it is bad and you are thinking of installing an AGM house battery then go with an isolater like the one WME suggests. This is another good one also https://www.littelfuse.com/~/media/commercial-vehicle/application-guides/littelfuse-if-161-48525-smart-battery-isolator.pdf Quote Link to comment Share on other sites More sharing options...
Maineah Posted August 18, 2018 Share Posted August 18, 2018 Often referred to as "combiners" One of the neat things about them they are bi directional this means you charging system will also charger you truck battery too when plugged in. Quote Link to comment Share on other sites More sharing options...
neubie Posted August 19, 2018 Author Share Posted August 19, 2018 (edited) Do the combiners act like isolators except for charging purposes or are they combiners for charging and discharging? I would worry about losing all batteries to my mysterious lights-coming-on-by-themselves and such if it was just a safe always on fuse. This is what I have now, so everything is an upgrade, even a new solenoid. I wouldnt hate a combiner if it doesnt discharge the truck battery from house use. Edited August 19, 2018 by neubie Quote Link to comment Share on other sites More sharing options...
WME Posted August 19, 2018 Share Posted August 19, 2018 Modern combiners, combine when one of the batteries is under charge. Charge from truck alternator, charge from RV converter, charge from solar. They act as isolator when there is no charge. The trigger is when one of the batteries drops below a certain voltage usually some where in the upper 12v range, then it turns into an isolator. So you would be good with one. Quote Link to comment Share on other sites More sharing options...
neubie Posted August 19, 2018 Author Share Posted August 19, 2018 couldnt hurt trying one then. They arent that much costlier than a solenoid. Quote Link to comment Share on other sites More sharing options...
Maineah Posted August 19, 2018 Share Posted August 19, 2018 The way they set up it is weighted to the truck battery that being the bench mark. It is activated by raising voltage at the truck battery once the engine is running otherwise it sits there fat dumb and happy. Quote Link to comment Share on other sites More sharing options...
neubie Posted August 21, 2018 Author Share Posted August 21, 2018 Except for a hole in the wall with no screw in it now, the electrical circuit seems to report correct voltages. How can one test the combining ability of thing -- solar is sort of charging things and currently both battery sets are sort of charged. Quote Link to comment Share on other sites More sharing options...
WME Posted August 21, 2018 Share Posted August 21, 2018 Disconnect solar, measure voltages, turn on truck head lights. At some point the combiner will disconnect the batteries and the truck battery will keep dropping and the house battery should hold a constant voltage. Quote Link to comment Share on other sites More sharing options...
Maineah Posted August 21, 2018 Share Posted August 21, 2018 It's hard to tell but it does look like a combiner. Here is how they work the truck is primary once the truck battery charge is satisfied the relay closes and it commences to charge the coach battery (engine running). They are voltage sensitive so if the coach battery drops below the truck battery voltage after the engine is off it disconnects. If you are using solar it's best to connect it to the coach battery because it's, it's only means of charging engine off and with the combiner off it will not discharge the truck battery. Now some are bidirectional and if the coach battery charge exceeds the truck battery voltage it will combine then the solar will also charge the truck battery! Once the sun goes down the truck will disconnect. Quote Link to comment Share on other sites More sharing options...
neubie Posted August 22, 2018 Author Share Posted August 22, 2018 (edited) Thanks all. The combiner is WMEs recommendation above. This one charges both batteries when alternator provides current, I tested that. There is a pin called ignition assist on the thing, I should read its manual. Perhaps it does combine when truck falls below usable levels. Will try the headlights + other lights idea. With a new charged truck battery, are we talking hours on the lights,or just a few minutes? Need to measure electric use everywhere anyway. Edited August 22, 2018 by neubie Quote Link to comment Share on other sites More sharing options...
WME Posted August 22, 2018 Share Posted August 22, 2018 14 hours ago, neubie said: . There is a pin called ignition assist on the thing, I should read its manual. Wow a totally awesome thought Quote Link to comment Share on other sites More sharing options...
Maineah Posted August 23, 2018 Share Posted August 23, 2018 Usually what the ing. assist is for is drawing current from the coach battery to assist the truck battery getting the truck started it combines the batteries to give the truck battery a boost whether they like it or not. Quote Link to comment Share on other sites More sharing options...
neubie Posted August 23, 2018 Author Share Posted August 23, 2018 11 hours ago, WME said: Wow a totally awesome thought I would totally do it if it didnt get in the way of my beauty sleep. Quote Link to comment Share on other sites More sharing options...
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