theoldwizard1 wrote:

In 50+ years of driving, I have NEVER had an alternator or voltage regulator fail. 1 maybe 2 starters.

pianotuna wrote:


I have seen 16 amps going to the house bank at idle. The highest reading noted was 19.6 amps, when driving. I don't have an easy way to measure input amps to the unit.

otrfun wrote:

Using, or not using any given protective device hinges on an individual's aversion to risk.

For those who want the peace-of-mind of knowing their dc to dc charger will not discharge their battery if their alternator goes off-line for any reason, a BI serves a very useful purpose.

For those who don't, it doesn't.

theoldwizard1 wrote:


I keep thinking about this.

It is possible that the charger is limiting the output current when there is lower input voltage because of internal heat. In other words, it is protecting itself from over heating.

StirCrazy wrote:

all the dc to dc i have seen have a trigger wire so you can put it to a switch and onlly turn it on when you need it or hook it to the altanator trigger so it only starts when the altanator is putting out a voltage.

mine is going on a KOER upfitter switch so I have to physicly turn on the switch and the engine has to be running before it will energize as for me this will just be a emergency source of power and I want to controle when it is on and off.

with this you don't need a BI as it is built in, but if all you want to do is have it so you cant drain down your starting battery and not worry about charge profile then yes a BI is the way to go, but they serve two different purposes so one isnt a replacment for the other, well except in the case of the dc to dc as it has a built in BI so you get both if you go that way...

otrfun wrote:

If I understand your explanation, your system is going to: Require the operator to physically turn on the KEOR upfitter switch, while the engine is running, before it (the dc to dc charger) will energize.. Based on this functional description, I don't see how your KOER upfitter switch offers any additional or different capability vs. a standard dc to dc charger installation, other than the ability to turn the dc to dc charger off an on at will. Any switch will do that. Now if you're also saying the KOER upfitter switch output is only active when the engine is running, then a BI wired through a simple off/on switch would function the same way. It would only allow the the dc to dc charger to be turned on when the switch is on and the engine is running.

You seem to infer the Renogy ignition trigger wire and/or Battery Isolator has some effect on the Renogy dc to dc charger's "charge profile". They do not! This is true regardless how they're used, or not used, as the case may be. They *only* turn the dc to dc charger off and on---nothing more, nothing less.

StirCrazy, you mention a BI (Battery Isolator) is "built-in" to a Renogy dc to dc charger. It is not! The ignition trigger wire by itself is *not* equivalent to a BI. The Renogy ignition trigger wire will activate the dc to dc charger when it senses *any* nominal amount of 12vdc (10-15v). It cannot tell the difference between the output of a battery or alternator. A Battery Isolator can. The BI is voltage selective to ensure it will *only* close the relay (activating the dc to dc charger) when the alternator is active, when voltage is >=13.3v. Battery voltage (12.7v) alone will *not* activate the BI relay. This protects the battery from being discharged by the dc to dc charger if the alternator is not operating for any reason. *None* of this capability is "built-in" to a Renogy dc to dc charger.

Lastly, yes, you can connect the Renogy ignition trigger wire directly to the alternator output. This will turn-off the dc to dc charger when the alternator is off-line. However, it's important to find a circuit that is not backfed by the battery when the engine is not running. On some vehicles, this is much easier said than done. Using a battery isolator can save time and grieve and accomplish exactly the same thing. Additionally, for those who have a dc to dc charger located inside a TT, 5R, or TC, mounting a BI inside the RV, next to the dc to dc charger, can save the hassle of running a 20-30 ft. ignition trigger wire all the way to the alternator in the TV engine compartment.

StirCrazy wrote:

you need to read what I said, I am putting it on the upfitter switch so I have controle when it is on. I never mentioned that it has anything to do with the charge profile, it is like you said to turn on or off. if it is on you are charging your house battery if it is off you are basicly isolated and the actual place to hook it to is a alranator output that is only hot when the engin is running.

For me, the only time I am using it is when it is an emergency as that means my solar has failed due to weather or what ever so yes I want to be able to have it off while I am driving and don't need it, or when I am camping I can turn the switch on while the truck is off and if I run into a situation where I need some extra power I can just use the remote start from inside the camper. so I am basicly using it as a very afordable and much quieter generator. I do not want it running when ever the truck is. that would just be a waist of fuel to me, and yes extra curent will decrease fuel milage. the problem as you sugested by just using a simple on off switch is what if you leave it on? if I leave an upfitter switch on and shut off the truck the circuit goes dead allowing me to leave it in that state and use it like a generator. and one more thing if you look at any documentation for a dc to dc it is to be installed as close to the batteries it is charging as possible so running a new wire or two is the best option anyways.

as for the isolate part I believe I said it acts like a built in battery isolater, if I didn't I apologise (I worded that wrong and changed it to read proper) it is a battery charger not a wire so it will only flow one way if the truck is off and your trigger wire is hooked up properly. it won't suck down your starting battery unless you intentionaly hooked it up that way which is contratry to the instructions. a battery isolater is useless unless you using starting batteries for your rv, well not useless but doesnt do anything except prevent back draw, it does nothing to optimize charging profiles and that is the main reason to use a dc to dc charger. and yes you have to hook it up right, the trigger is to be hooked up to a line thats only hot when the engine is running and on top of that you have to size it properly for your altanator.