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DC-DC Charge install Reflection 29RS

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  • ncitro
    replied
    Originally posted by Wasatch View Post
    Thanks ncitro!

    Yes, 20A (oops)

    Appreciate the logic description of the converter only in the system during shore/generator power. I installed a PD 50A transfer switch to bring in an inverter and resolve the batter charging battery loop. The converter is on the shore power to ac panel side of the switch.

    From what I read, I believe the Renogy charger should read the battery charge level and even with the 7-way giving some juice, adjust the charge mode- is that what you are experiencing with your set up?
    Thats correct. In my case I still see the 7 amps or so from the seven pin contributing to charge until the batteries get towards full. More commonly I do not enable the DC to DC charger unless I know I will need it (towing in rain or clouds with a low SOC) no reason to stress the trucks alternators unless needed. In those cases I leave charging up to my solar panels and the stock 7 pin charger and again, I see the 7 pin contributing until they get towards full, then the solar panels top them off.


    NickinCO ​​​Note that while I have not had any issues there have been concerns raised in the past about harm to the truck when using the stock wiring. In particular I know howson linked a article from AM solar stating the always disable the factory wiring when they do an install. I will see if I can find that discussion and link it.

    Edit: Post 138 here:

    https://gdrvowners.com/forum/operati...e-borns/page10

    Leave a comment:


  • Country Campers
    replied
    Originally posted by Wasatch View Post
    Thanks ncitro!

    Yes, 20A (oops)

    Appreciate the logic description of the converter only in the system during shore/generator power. I installed a PD 50A transfer switch to bring in an inverter and resolve the batter charging battery loop. The converter is on the shore power to ac panel side of the switch.

    From what I read, I believe the Renogy charger should read the battery charge level and even with the 7-way giving some juice, adjust the charge mode- is that what you are experiencing with your set up?
    You will want to make sure that the converter is OFF when you are using the inverter, you do not want to take battery power to the inverter to the converter and charge the battery, the electrons will get confused and you will probably deplete your batteries.

    Brian

    Leave a comment:


  • howson
    replied
    Originally posted by NickinCO View Post
    Wish people would stop saying the stock 7-pin can damage the lithium batteries, made it very confusing when I was spec'ing a system. That's simply not the case. It just won't charge them to 100% SOC.
    I haven't followed every post closely--who is stating using the 7-pin with the truck's OEM-provided charge will damage a lithium? Not my intent to "call someone out" but it is important, especially on this forum, to provide accurate technical information.

    Leave a comment:


  • NickinCO
    replied
    Wish people would stop saying the stock 7-pin can damage the lithium batteries, made it very confusing when I was spec'ing a system. That's simply not the case. It just won't charge them to 100% SOC.

    Leave a comment:


  • Wasatch
    replied
    Thanks ncitro!

    Yes, 20A (oops)

    Appreciate the logic description of the converter only in the system during shore/generator power. I installed a PD 50A transfer switch to bring in an inverter and resolve the batter charging battery loop. The converter is on the shore power to ac panel side of the switch.

    From what I read, I believe the Renogy charger should read the battery charge level and even with the 7-way giving some juice, adjust the charge mode- is that what you are experiencing with your set up?

    Leave a comment:


  • ncitro
    replied
    Originally posted by Wasatch View Post
    First question here on this DC-DC charger install. Thanks for the insight thus far.

    We have a 31MB Reflection, I upgraded the stock Progressive Dynamics power converter to the PD9100L (Lithium model). We have two 105Ah 12v lithium batteries in the RV. I am installing a Renogy 20v DC-DC battery charger. I used 4AWG from the truck batteries and opted to run that 4AWG line to a connection in the truck bed that will connect to a 4AWG run into the battery compartment and into the Renogy charger. I am not using the 7-way wiring.

    Thoughts on:

    Can I keep the PD9100L connected to the system via the current 7-way pin connection and will the converter's TCMS manage the PD9100L charging voltage output based on the volts the batteries are receiving from the tow vehicle/Renogy battery charger? Thus, with the TCMS, will the PD9100L adjust to not overload the battery because it senses the voltage of the battery at any given time/mode?

    Another instance- say, if the battery is 25% full (~12v) and I start charging it via the tow vehicle thru the Renogy battery charger and say I am getting a max of 14.1 v, will the PD9100 kick in and increase the volts to 14.6 (adding .5 volts) to that mode of the charging logic?

    Thanks
    Congrats on the project sounds like it'll be a good system. I assume you meant the 20A Renogy not the 20V.

    Keep in mind the converter does not affect the factory 7 way pigtail. That charge wire goes directly to the battery and has no charge profile built into it. Some people (myself included) run both the Renogy and 7 pin and some remove the 7 pin charge wire. howson recently had a write up on that process.

    Your converter will only do anything when you are connected to shore power or generator power.

    Leave a comment:


  • Wasatch
    replied
    First question here on this DC-DC charger install. Thanks for the insight thus far.

    We have a 31MB Reflection, I upgraded the stock Progressive Dynamics power converter to the PD9100L (Lithium model). We have two 105Ah 12v lithium batteries in the RV. I am installing a Renogy 20v DC-DC battery charger. I used 4AWG from the truck batteries and opted to run that 4AWG line to a connection in the truck bed that will connect to a 4AWG run into the battery compartment and into the Renogy charger. I am not using the 7-way wiring.

    Thoughts on:

    Can I keep the PD9100L connected to the system via the current 7-way pin connection and will the converter's TCMS manage the PD9100L charging voltage output based on the volts the batteries are receiving from the tow vehicle/Renogy battery charger? Thus, with the TCMS, will the PD9100L adjust to not overload the battery because it senses the voltage of the battery at any given time/mode?

    Another instance- say, if the battery is 25% full (~12v) and I start charging it via the tow vehicle thru the Renogy battery charger and say I am getting a max of 14.1 v, will the PD9100 kick in and increase the volts to 14.6 (adding .5 volts) to that mode of the charging logic?

    Thanks

    Leave a comment:


  • Guest
    replied
    My Renogy was verified to deliver 20amps through my 7 way connector. It can draw up to 30amps depending on the TV output voltage so in the GM case (no promotion) when the tow haul mode is active or the headlights are on, the TV output voltage will be increased which helps to lower the overall load on the 7 way.

    Jim

    Leave a comment:


  • Country Campers
    replied
    BLoflin

    I am pretty sure we are all on the same page, just each individual input and understanding is kind of hard to do in short posts, better discussed around a campfire. I will surely post some numbers once we get out of the winter funk and get to camping.

    Great discussion and input by all.

    Brian

    Leave a comment:


  • BLoflin
    replied
    Originally posted by Jkwilson View Post

    You are missing the entire key point. A battery is not a fixed load. Boosting the voltage at the battery INCREASES the current flowing into the battery. 100% absolutely and always. You can’t increase the voltage without increasing current, and you can’t increase the current without increasing the voltage.

    The voltage drop in the wiring causes the battery to draw less current. That means the battery is not getting all of the power that the tow vehicle charging circuit can provide. By boosting the voltage, the battery draws more current and receives more power, up to the ability of the charging circuit to provide power because the alternator sees a load it responds to.

    Numbers you might see with direct wiring to the trailer might be 13V and 6A providing 78W to the trailer battery. With the DC-DC converter you’d theoretically see 14.6V and 20A, though the circuit usually is current limited to more like 12A, providing ~175W to the battery.
    Thanks. But I'm not missing the entire point. I was not questioning on what is needed to charge a battery. I was questioning on why it appeared there was a belief the Renology part will put out 20A regardless of the capacity of the tow vehicle can provide to the input.

    I agree the Renology part is good (and pretty much necessary) as it performs two functions (especially in relation to LiPo RV batteries). It increase the Voltage as, yes, that is needed to actually put charge into the batteries AND it is intelligent in that it steps thru the 3 phases of battery charging and adjust the voltage according.

    My whole original response, and what I was still trying to explain, is that the Renology part does NOT and can NOT boost either power or specifically current "magically" when used with a tow vehicle that can only put out 6 amps. That is what I was (over?) reacting too.

    The OP latter responded with perhaps not a good choice of words.

    I just didn't want anyone thinking they could get 20A of charging out of the Renology device while the vehicle was limited (either due to Alternator output, wiring or fusing) to just 6 amps.

    Then the other people posting confused me more in some cases, so I continued to try and clarify (but I guess I failed)..

    I apologize, as hopefully we are all together now. Renology DC to DC Battery Charger is a good part of the solution. But it doesn't fix if your tow vehicle charging design is deficient. A user needs to understand if they want to provide 20A to their batteries from Renology part, then they need to provide (at least) 20A from their tow vehicle.

    Thanks,

    Leave a comment:


  • Guest
    replied
    Country Campers howson

    Brian, Howard, nice posts on the installation and operation.

    After testing my 20amp Renogy outside the rig as an initial test, I measured up to 27 amps at startup if my memory serves me. Running current was at 25amps. With the low internal resistance of the LiFeP04 battery, the Renogy delivered the specified 20amps to the rig. For folks that are not confident in the 7 way to operate at the full capacity of the 20amp Renogy, the charger can be configured via a jumper wire to result in a 50% reduction in output. So in this case, the Renogy will output 10amp while drawing as much as 15amp from the TV through the 7 way. This will still allow for proper LiFeP04 charging while isolating the two different battery chemistries between the RV and TV.

    Jim

    Leave a comment:


  • Jkwilson
    replied
    Originally posted by Jlawles2 View Post
    Jkwilson John, someone else will probably chime in to help clarify also. Most of the people running DC-DC chargers are not running lead acid batteries. Instead they are running LiFePO4 which finish charging at a higher voltage. Without the DC-DC charger the LiPO will only charge to about 80% (IIRC) capacity. By using the DC-DC charger they ensure that they get the 100% charge needed.
    Likely correct. The issue is even more pronounced on lithiums because their open circuit voltage is closer to the charging system maximum output so the voltage drop on the run to the trailer is much more critical. In this application, the DC-DC converter is functionally a battery charger with a DC input. Typically these DC-DC converters will work with an input voltage as low as 7 or 8 volts.

    Leave a comment:


  • Jlawles2
    replied
    Jkwilson John, someone else will probably chime in to help clarify also. Most of the people running DC-DC chargers are not running lead acid batteries. Instead they are running LiFePO4 which finish charging at a higher voltage. Without the DC-DC charger the LiPO will only charge to about 80% (IIRC) capacity. By using the DC-DC charger they ensure that they get the 100% charge needed.

    Leave a comment:


  • Jkwilson
    replied
    Originally posted by BLoflin View Post

    Hmmm, but that isn't how electricity works at all. The equation is V=I*R. Also Power has to be conserved. Power In = Power Out - losses (thermal, etc). For Power Out to be more than Power In then Power needs to be created (via a power source, like a fuel or chemical reaction, or in case of the vehicle alternator, fuel into an engine and an engine turns the Alternator).

    For example lets say the Alternator voltage is 14V (just to keep it simple, no decimals) at the Alternator. Lets say when you pull 6 Amps out at the trailer connection the Voltage drops to 12V. That means the wire resistance to the plug is 0.333 Ohms (14 - 12V / 6A). You drop 2V due to resistance along the wire. If you try and pull 12A then the voltage at the trailer connection drops to 10V.

    Also the Power is consistent: At Alternator is 14V x 6A = 84Watts. At Connector is 12V x 6A = 72W + Power loss in the wire resistance is 2V x 6A = 12W which totals 84W.

    Instead if you are trying to pull 12A then power at Alternator is 168W and power at connector is 120W and the power loss in the wire is 48W.

    Now for simplicity lets assume the DC-DC Converter (Renology part) is sitting right at the Trailer Connector (i.e. no additional wire with additional resistance).

    The Convertor will take that 10V with 12A input (i.e. 120W) and step it up (convert it) say to 15V to be able to start a Bulk Charge cycle for the battery (again using rounded numbers for math simplicity). Then the available current DROPS to 8A (actually a little less than 8 as there are some losses in the Renology circuits), 8A x 15V = 120W. Again because you can NOT create power (without a power source).

    The OP spoke of "boosting" the power. You can not. You can boost the Voltage in a Converter, but with the corresponding LOWERING of the current. Or conversely you can boost the Amps by lowering the Voltage ouput, but of course that would not be helpful for charging batteries.

    Also, again the 20A rating on the Renology is NOT the guaranteed current output, it is the highest current (and also highest power rating is nominal 250W based on the 20A and 12V). They also have a 40A (500W) and a 60A (750W). None of these can create power or boost current if you are not delivering the corresponding input current and voltage.
    You are missing the entire key point. A battery is not a fixed load. Boosting the voltage at the battery INCREASES the current flowing into the battery. 100% absolutely and always. You can’t increase the voltage without increasing current, and you can’t increase the current without increasing the voltage.

    The voltage drop in the wiring causes the battery to draw less current. That means the battery is not getting all of the power that the tow vehicle charging circuit can provide. By boosting the voltage, the battery draws more current and receives more power, up to the ability of the charging circuit to provide power because the alternator sees a load it responds to.

    Numbers you might see with direct wiring to the trailer might be 13V and 6A providing 78W to the trailer battery. With the DC-DC converter you’d theoretically see 14.6V and 20A, though the circuit usually is current limited to more like 12A, providing ~175W to the battery.

    Last edited by Jkwilson; 03-05-2022, 09:16 PM.

    Leave a comment:


  • ncitro
    replied
    BLoflin Howard has it right, and your concerns are valid as well. Those of us that have used the 40 or 60 amp models have run large gauge wire back from the truck battery to the Renogy (I used 4AWG for my 40A), and have alternator capacity to spare (I think Howard and I are both running dual heavy duty alternators). Those that are using the factory wiring are using the 20A model, in a Ford the factory charge wire is 10AWG, and is fused large enough to handle the load. Guest was I believe the first to do the upgrade with his factory wiring on his GM, and he verified that the stock wiring and fuses were adequate for his calculations.

    Leave a comment:

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