Renogy 20A dc to DC report

[pianotuna]

Hi All,

Regarding the Renogy 20A DC to DC Battery Charger 12V, the unit puts out 20 amps, but draws 30 amps when doing so. This is the result of bench testing.

[pianotuna]

otrfun,

Thanks for the posts you made.

[otrfun]

StirCrazy wrote:

otrfun wrote:

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...

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.

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.

StirCrazy, I read your previous post a number of times before I posted my reply. My apologies, but I was having a very difficult time comprehending it. I high-lighted in bold what I saw as your major points, took them at face value, and replied accordingly.

As for this last post, suffice to say, it appears you're applying due diligence to ensure you get the results and performance you want.

The primary purpose of my previous post was to clarify what a Renogy ignition trigger wire and battery isolator can and cannot do, in the simplest, most succinct way I know how. Although a battery isolator is a very simple device, it is also a very much misunderstood device in terms of its function, capability and application.

At this point, I don't think I have anything further to add to this thread, so I think it's time for me to bow out.

Sounds like you've got some very cool projects going on. Best of luck with them all!

[StirCrazy]

otrfun wrote:

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...

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.

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.

[otrfun]

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...

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.

[pianotuna]

theoldwizard1 wrote:

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.

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.

Hi theoldwizard1,

I don't know the input voltage at idle. It is not something I would normally do (i.e. idle).

[StirCrazy]

otrfun wrote:

theoldwizard1 wrote:

otrfun wrote:
it would also continue to operate if the alternator fails. Having a very high amperage drain on your battery if your alternator fails, in the middle of nowhere, would not be fun.

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

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.

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 acts like it has a built in BI so you get both if you go that way...

[theoldwizard1]

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.

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.

[otrfun]

theoldwizard1 wrote:

otrfun wrote:
it would also continue to operate if the alternator fails. Having a very high amperage drain on your battery if your alternator fails, in the middle of nowhere, would not be fun.

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

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]

otrfun wrote:
it would also continue to operate if the alternator fails. Having a very high amperage drain on your battery if your alternator fails, in the middle of nowhere, would not be fun.

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

[otrfun]

pianotuna wrote:
otrfun,

Back when I first had a 2500 watt inverter, I'd often run the water heater on electric. I monitored voltage when doing so and when it reached 12.2 I'd shut down and allow the battery bank to recover. I found I could sustain a 1:3 where I'd run the heater for 20 minutes and then leave it off for 40 minutes.

I'm still on the OEM alternator.

Yup, it's surprising how much load some things can take and continue to work.

I've always been a big fan of making lots of voltage and current measurements. Reducing voltage drops and maximizing efficiency & current transfer between components is a pet peeve of mine. If possible, try to go one cable larger than needed with every install. When dealing with 12v DC circuits, I strive for 1% voltage drop under maximum load. In a pinch, I will occasionally accept 2%. Many of the installs I've seen through the years have 5 to 10% drops. Yup, they "work", but not well, or to specs.

[otrfun]

theoldwizard1 wrote:
If you are towing or using a truck camper, the B+ wire on the 7 pin trailer harness is almost always wired to a KEY-ON circuit. Now additional wiring required.

Yes, B+ on the 7-pin is a possible option. Several downsides to using a simple ignition on approach, however. The dc to dc charger would still continue to operate if the ignition is left on without the engine running--potentially depleting the battery. Plus, it would also continue to operate if the alternator fails. Having a very high amperage drain on your battery if your alternator fails, in the middle of nowhere, would not be fun.

We much prefer using a Battery Isolator with a 13.3v close/on, and 12.8v release/off relay. The BI prevents the dc to dc charger from operating unless the alternator is operating. If you turn on the ignition without the engine (alternator) running you're protected. If the alternator fails while you're driving, you're also protected.

The BI can be installed pretty much anywhere. Next to the dc to dc charger or on the TV. One option, wire the BI inline with the power cable feeding the dc to dc charger. Another option, mount the BI next to the charger and parallel off the input terminal of the dc to dc charger with a small wire and use the BI to simply open/close voltage to the Renogy's ignition trigger wire. We prefer the latter. One less connection/terminal on the primary power cable is a good thing.

[theoldwizard1]

otrfun wrote:
The Renogy ignition trigger lead and/or commonly used battery isolator accomplishes would you're describing. If the Renogy ignition trigger lead detects a "nominal" 12vdc, the charger turns on. If the 12vdc goes away, it turns the charger off. A battery isolator operates in a similar fashion, but it's much more voltage selective.

If you are towing or using a truck camper, the B+ wire on the 7 pin trailer harness is almost always wired to a KEY-ON circuit. Now additional wiring required.

otrfun wrote:
What pianotuna is describing is a 3-4a drop in output charge current at idle (vs. driving).

I mis-understood! I would be unhappy as well. I don't think that is in the spec sheet !

[StirCrazy]

pianotuna wrote:
otrfun,



In the RV the wire length is about 12 feet due to the dc to DC having to be located under the passenger's seat. It is #8 wire which is more than adequate for 30 amps input (about 6 feet on input side).

The renogy does have a cooling fan.

hold on here, #8 gage is the bare minimum size for a 2% voltage drop at a max lenght of 6 feet, I would hardly call that more that adequate, thats pushing the limit.

I do remember you saying it was to hard to upgrade the wire so if your happy with it thats fine but Otrfun is right, a larger cable would reduce the voltage drop and lower your inlet current.

[pianotuna]

otrfun,

Back when I first had a 2500 watt inverter, I'd often run the water heater on electric. I monitored voltage when doing so and when it reached 12.2 I'd shut down and allow the battery bank to recover. I found I could sustain a 1:3 where I'd run the heater for 20 minutes and then leave it off for 40 minutes.

I'm still on the OEM alternator.