RV Charging tech

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    RV Charging tech

    Here's a shift of gears. I have a 1980 Winnebago with an LA 360. As part of my upgrades, I want to be able to power the rooftop air off the alternator, so I will no longer have to run the generator (on a tray on the bumper) while driving down the road. I have already installed a 3000w inverter in the past, and it will run the A/C for a short period before the voltage drops too much at the coach batteries. Mathematics tell me that, after initial starting load, the rooftop unit will draw between 120 and 125 amps through the inverter circuit. The RV originally came with a 74 amp alternator, but immediate need during a failure event found a 60 amp replacement installed (the only one I could get immediately) about 5 years ago.

    Summit Racing has a 165 amp alternator that will fit. https://www.summitracing.com/parts/p...ge/model/cb300 Being an older coach, I don't think it uses much more than 15 amps overall outside the inverter usage, so 165 should be more than enough.

    Here's where the tech gets muddy:

    The 8 awg charge wire runs to the chassis battery. Another 4 awg cable runs from there to a solenoid and on to the coach batteries.
    The dash has an ammeter instead of a voltmeter. The voltmeter is separated from the rest of the gauges in its own panel with a double-throw momentary switch to check the chassis and coach voltages separately.

    If my math is correct and this works, how should I wire it up?

    I would just put a 4 awg charge cable from the alternator to the battery, but my thoughts then turn to the ammeter. When I crank on the roof unit, will this let the magic smoke out of the gauge or cluster? Potential fire hazard?

    Another thought is to run a separate 2 awg cable from the alternator to a second Cole Hersee solenoid (with its own switch) straight to the coach battery pack.

    And a final concern would be the voltage regulator. Its external, and stock. Should I upgrade to something like this? https://store.alternatorparts.com/QS...regulator.aspx



    As for why not just keep using the generator? Two reasons. One, its loud. Getting a Honda EU-2000 would cost many times more than this upgrade. Two, the generator tray and bumper assembly stick out a bit off the rear. If I can relieve myself of needing the tray, I can modify the spare rack and bumper which will then allow me to tuck the hitch receiver closer to the body, lessening the leverage tongue weight has on the short coach's wheelbase. Its only 20 feet long, after all.
    Mrs CSR said I was good, or something.

    #2
    Interesting...
    brb
    83, 22re,w56,ultimate duals,4:10 \31" arbs.
    hopes to grow up someday

    Comment


      #3
      What does the invertor recomend for wire size? In my wifes grooming van i run 2 agms and it has 120 amp alt on the apu power pack. Everything is within 6' and i run 1/0 wire. 15 amps of 110v will pull the power down pretty fast and i wish i put 4 batterys in. I think the alt and inveror r gonna hate that ac unit.

      Comment


        #4
        I think you are going to be at 165 amps just with the AC. I think I would get a larger 200A range inverter and a separate group 31 battery just for the "house" loads.
        This is going to be really hard on the alternator I don't think a regular pickup alternator will last long. There are plenty of high output 400a+ alternators but they will be up around $500 but I think you could find a used Delco heavy duty semi truck alternator that would do the job.

        Alternate idea might be to add some solar to offset the load. 400w will get you mid 20's of amps, large commercial panels can be had pretty cheaply.

        Comment


          #5
          Originally posted by Dejeeper View Post
          What does the invertor recomend for wire size? In my wifes grooming van i run 2 agms and it has 120 amp alt on the apu power pack. Everything is within 6' and i run 1/0 wire. 15 amps of 110v will pull the power down pretty fast and i wish i put 4 batterys in. I think the alt and inveror r gonna hate that ac unit.
          I believe it was 2/0, and that's what I installed, along with a 300 amp fuse.
          Last edited by DRTDEVL; 06-30-2020, 07:55 PM.
          Mrs CSR said I was good, or something.

          Comment


            #6
            Originally posted by CarterKraft View Post
            I think you are going to be at 165 amps just with the AC. I think I would get a larger 200A range inverter and a separate group 31 battery just for the "house" loads.
            This is going to be really hard on the alternator I don't think a regular pickup alternator will last long. There are plenty of high output 400a+ alternators but they will be up around $500 but I think you could find a used Delco heavy duty semi truck alternator that would do the job.

            Alternate idea might be to add some solar to offset the load. 400w will get you mid 20's of amps, large commercial panels can be had pretty cheaply.
            Its only a 1350 BTU roof unit (not 15,000), so it runs at about 1250 watts AC. By my math, that's technically only 10.5 amps A/C, and converted to 12 vdc is about 116 amps. Add in for losses from the conversion, and that's where I came up with 120-125 amps.

            I currently have a pair of group 31s for the coach batteries. I will be modifying the battery tray in coming weeks (they don't quite fit right as 27s were stock), and have considered upping the size (if there is room) to 3 group 31s in parallel.

            I did consider the 200 amp units as well.

            I am also considering solar in the long run, but whatever I do now needs to be done before heading out to Sturgis in 5 weeks. An alternator and wiring upgrade seems to be the most economical solution in my situation.

            A little more back story:

            The RV was my grandfather's and he didn't want AC, as he only planned to go up and down PCH with it. He checked the block for no AC when he ordered it, and was pissed that there was AC in the dash, not knowing that no A/C meant only no rooftop unit. He removed everything under the hood for the AC, and I cannot locate the right compressor or brackets anywhere. I have to run the roof unit (that I installed) when I drive in order to remain semi-comfortable. That's one of the reasons I installed such a large inverter... eventually planning on running the rooftop off the battery pack with enough charge capability.
            Mrs CSR said I was good, or something.

            Comment


              #7
              I would probably hook the alt to the truck bat with 2 and then connect the truck to the house batteries with 2/0. U want to minimize the loss. Use a large issolator or seliniod if u need to seperate the 2 battery banks.

              Fyi i just put a dometic 13.5kbtu unit on a trailer and it was 16amp.

              Comment


                #8
                I think some of your question was around the amp gauge. You are getting to the point where you don't want to bring those BIG wires through the dash, And good luck finding an amp gauge that will go to 60-200 amps.

                Many of us have the same issue. The solution is to use an amp gauge that just uses a "hall effect ring" around the alternator charge wire. You do NOT Break into the wire path to the batteries. They are available from cheap to $$$.

                Google "Hall Effect Amp Meter" or "Hall effect Current gauge" That should get you to what you may want. They can easily go to 200amps.

                You may want more than one because the one on the Amp-Battery wire will not show a discharge. Just the amount of Amps going to the battery. Normally at the battery positive terminal you will have several leads from there to your loads. More of the inexpensive sensors can tell you what is happening and an increase in amps might alert you to the fact that the battery voltage is dropping. That is why the Voltage meter is a really handy gauge to watch.

                A 200 amp alternator is not that unusual anymore. A KOH or TT truck can run 250 amps with all the cooling fans, lights, etc. The good alternators are not cheap, but a OEM 160 as a spare will get you home. No expert here..... Life taught.

                EDIT: I just noticed the post above on an isolator. That is not a bad idea for charging the batteries independently especially when using a real battery charger.. You can also run a parallel link between the 2 positive posts with a hand latching switch. That is to separate the "starting battery" from the "House battery" when PARKED-ALTERNATOR NOT RUNNING. But you can always engage it to connect the two batteries at your will MOMENTARILY for car starting.. (I am not sure but I think the alternator wire then goes to the center terrminal of the isolator....Yes per below)

                So now you are at the cost of installing dash air............Cheers.

                Click image for larger version  Name:	dual-battery-isolator-charging-system.jpg Views:	0 Size:	17.7 KB ID:	57207
                Last edited by Isdtbower; 06-30-2020, 10:44 PM.

                Comment


                  #9
                  I use something similar to this in my RV for DC loads and a hall effect version on the AC. It allows me to monitor all the incoming/outgoing loads to maximize battery when boondocking.

                  I have 400w of solar and 2x 6v GC2 golf cart batteries but the voltage sag with the inverter for things like the coffee maker etc. is pretty extreme.

                  If you have the smaller AC you might be OK but the commpressor start up load is going to be huge and if you have not checked it already you should make sure the inverter will even start it.

                  Comment


                    #10
                    Originally posted by Dejeeper View Post
                    I would probably hook the alt to the truck bat with 2 and then connect the truck to the house batteries with 2/0. U want to minimize the loss. Use a large issolator or seliniod if u need to seperate the 2 battery banks.

                    Fyi i just put a dometic 13.5kbtu unit on a trailer and it was 16amp.
                    I just double-checked the mfr (Coleman Mach 3), and max load is 14.9 amps. That's right at 165 amps for 12v (lesser for 13.6), so I would have to go with the 215 amp at this point (only a few dollars more): https://www.summitracing.com/parts/p...ge/model/cb300

                    Originally posted by Isdtbower View Post
                    I think some of your question was around the amp gauge. You are getting to the point where you don't want to bring those BIG wires through the dash, And good luck finding an amp gauge that will go to 60-200 amps.

                    Many of us have the same issue. The solution is to use an amp gauge that just uses a "hall effect ring" around the alternator charge wire. You do NOT Break into the wire path to the batteries. They are available from cheap to $$$.

                    Google "Hall Effect Amp Meter" or "Hall effect Current gauge" That should get you to what you may want. They can easily go to 200amps.

                    You may want more than one because the one on the Amp-Battery wire will not show a discharge. Just the amount of Amps going to the battery. Normally at the battery positive terminal you will have several leads from there to your loads. More of the inexpensive sensors can tell you what is happening and an increase in amps might alert you to the fact that the battery voltage is dropping. That is why the Voltage meter is a really handy gauge to watch.

                    A 200 amp alternator is not that unusual anymore. A KOH or TT truck can run 250 amps with all the cooling fans, lights, etc. The good alternators are not cheap, but a OEM 160 as a spare will get you home. No expert here..... Life taught.

                    EDIT: I just noticed the post above on an isolator. That is not a bad idea for charging the batteries independently especially when using a real battery charger.. You can also run a parallel link between the 2 positive posts with a hand latching switch. That is to separate the "starting battery" from the "House battery" when PARKED-ALTERNATOR NOT RUNNING. But you can always engage it to connect the two batteries at your will MOMENTARILY for car starting.. (I am not sure but I think the alternator wire then goes to the center terrminal of the isolator....Yes per below)

                    So now you are at the cost of installing dash air............Cheers.
                    Not exactly. My concern is letting the magic smoke out of the current ammeter in the dash. I figure if I can keep that one to where its only reading the amp draw/charge rate of the chassis, the house charge line can be separated out and directly to the other battery pack, separated by a solenoid. I would have to put a diode on the chassis/starting battery charge wire, so any power spikes (like compressor starting) won't try to draw the excess through that 8 awg wire off the starting battery.

                    I already have a 4 awg line from the starting battery to the house batteries from the factory, and it is separated by a solenoid that is activated by a 3-position switch: Dual - Single (off) - Starting, and the start position is a momentary, spring loaded trigger that bypasses the ignition on circuit. There is also a power station with a float charger built in from the shore power line. It only charges the house batteries, but when the alternator failed, I was able to use the shore power line and the isolator switch to charge the starting battery and prevent its failure.

                    Originally posted by CarterKraft View Post
                    If you have the smaller AC you might be OK but the commpressor start up load is going to be huge and if you have not checked it already you should make sure the inverter will even start it.
                    It will run it and start the compressor with no problem, but the house batteries discharge within 15 minutes to set off the low voltage alarm, and that's with the engine running and driving, delivering the full 60 amps off the alternator. It falls about 100 amps short of what is needed. The inverter is rated at 3000w nominal and 6000w peak. https://www.amazon.com/KRI%C3%8BGER-...ZSCFHEDKA9Y3X6
                    Last edited by DRTDEVL; 07-01-2020, 09:37 AM.
                    Mrs CSR said I was good, or something.

                    Comment


                      #11
                      Originally posted by Isdtbower View Post
                      I think some of your question was around the amp gauge. You are getting to the point where you don't want to bring those BIG wires through the dash, And good luck finding an amp gauge that will go to 60-200 amps.

                      Many of us have the same issue. The solution is to use an amp gauge that just uses a "hall effect ring" around the alternator charge wire. You do NOT Break into the wire path to the batteries. They are available from cheap to $$$.

                      Google "Hall Effect Amp Meter" or "Hall effect Current gauge" That should get you to what you may want. They can easily go to 200amps.

                      You may want more than one because the one on the Amp-Battery wire will not show a discharge. Just the amount of Amps going to the battery. Normally at the battery positive terminal you will have several leads from there to your loads. More of the inexpensive sensors can tell you what is happening and an increase in amps might alert you to the fact that the battery voltage is dropping. That is why the Voltage meter is a really handy gauge to watch.

                      A 200 amp alternator is not that unusual anymore. A KOH or TT truck can run 250 amps with all the cooling fans, lights, etc. The good alternators are not cheap, but a OEM 160 as a spare will get you home. No expert here..... Life taught.

                      EDIT: I just noticed the post above on an isolator. That is not a bad idea for charging the batteries independently especially when using a real battery charger.. You can also run a parallel link between the 2 positive posts with a hand latching switch. That is to separate the "starting battery" from the "House battery" when PARKED-ALTERNATOR NOT RUNNING. But you can always engage it to connect the two batteries at your will MOMENTARILY for car starting.. (I am not sure but I think the alternator wire then goes to the center terrminal of the isolator....Yes per below)

                      So now you are at the cost of installing dash air............Cheers.

                      Click image for larger version Name:	dual-battery-isolator-charging-system.jpg Views:	0 Size:	17.7 KB ID:	57207
                      Bluesea Systems sells a real nice setup that includes a dash mounted button/switch to go between isolation modes.
                      @DobermanRacing

                      Comment


                        #12
                        Originally posted by DRTDEVL View Post
                        \n\nI just double-checked the mfr (Coleman Mach 3), and max load is 14.9 amps. That\'s right at 165 amps for 12v (lesser for 13.6), so I would have to go with the 215 amp at this point (only a few dollars more): https://www.summitracing.com/parts/p...ge/model/cb300\n\n\n\nNot exactly. My concern is letting the magic smoke out of the current ammeter in the dash. I figure if I can keep that one to where its only reading the amp draw/charge rate of the chassis, the house charge line can be separated out and directly to the other battery pack, separated by a solenoid. I would have to put a diode on the chassis/starting battery charge wire, so any power spikes (like compressor starting) won\'t try to draw the excess through that 8 awg wire off the starting battery.\n\nI already have a 4 awg line from the starting battery to the house batteries from the factory, and it is separated by a solenoid that is activated by a 3-position switch: Dual - Single (off) - Starting, and the start position is a momentary, spring loaded trigger that bypasses the ignition on circuit. There is also a power station with a float charger built in from the shore power line. It only charges the house batteries, but when the alternator failed, I was able to use the shore power line and the isolator switch to charge the starting battery and prevent its failure.\n\n\n\nIt will run it and start the compressor with no problem, but the house batteries discharge within 15 minutes to set off the low voltage alarm, and that\'s with the engine running and driving, delivering the full 60 amps off the alternator. It falls about 100 amps short of what is needed. The inverter is rated at 3000w nominal and 6000w peak. https://www.amazon.com/KRI%C3%8BGER-...ZSCFHEDKA9Y3X6
                        \n\n\nI don\'t think the 8ga and ammeter is going to be a problem, your inverter wiring needs to go direct to the battery for power and ground, 2x 1/0 or 2/0 cables depending on length (closer the better). Then the same from your alternator but I would got 2/0 on that or double 1/0 depending on length. Every bit of voltage drop you have is going to cost you in efficiency and overall output. You don\'t want a loosing battle and you find out 2 hours into a trip the now HOT components can\'t keep up.\n\nI\'m not sure about running a modified sine wave inverter on that large of a load. I know it will run it, I had a 2kw unit in my service truck for years but it is really hard on motors. It would suck to kill your AC on the way to the place you needed it...\n\nedit: easy way to isolate is with a VSR https://www.amazon.com/PAC-PAC-200-2...s%2C225&sr=8-5
                        Last edited by CarterKraft; 07-01-2020, 10:18 AM.

                        Comment


                          #13
                          You need to listen to what was posted above. Coleman Mach ac’s pull waaay more than 14 amps on startup. I know, we had that exact model in our last fifth wheel. Our 3200 watt Yamaha generator wouldn’t even start it. When they start the amperage spikes for a split second. That’s gonna kick a three thousand watt inverter off. We tried everybody in the family’s generator and none of em would start it. I posted in the other thread about putting an Easy Start on it to get it to run off our generator. I pulled it off the trailer when we sold it and put it on our newer fifth wheel we just bought. It has a 15,000 btu on it and runs with ease on the generator. Try it jerryrigged first to see if the inverter will start it and run it first before you invest all the time and money into a total install and maybe not work.

                          Comment


                            #14
                            Originally posted by rockdog57 View Post
                            You need to listen to what was posted above. Coleman Mach ac’s pull waaay more than 14 amps on startup. I know, we had that exact model in our last fifth wheel. Our 3200 watt Yamaha generator wouldn’t even start it. When they start the amperage spikes for a split second. That’s gonna kick a three thousand watt inverter off. We tried everybody in the family’s generator and none of em would start it. I posted in the other thread about putting an Easy Start on it to get it to run off our generator. I pulled it off the trailer when we sold it and put it on our newer fifth wheel we just bought. It has a 15,000 btu on it and runs with ease on the generator. Try it jerryrigged first to see if the inverter will start it and run it first before you invest all the time and money into a total install and maybe not work.
                            You need to read what was posted above. My inverter can handle a 6000 watt spike, and can run the a/c unit until the batteries drop below 12.2 volts right now. My cheapo Sam's Club 3600w generator has a 4600w spike capability, and it doesn't stall, either.
                            Mrs CSR said I was good, or something.

                            Comment


                              #15
                              Originally posted by DRTDEVL View Post

                              You need to read what was posted above. My inverter can handle a 6000 watt spike, and can run the a/c unit until the batteries drop below 12.2 volts right now. My cheapo Sam's Club 3600w generator has a 4600w spike capability, and it doesn't stall, either.
                              Damn, missed that. I are not good at reading comprehension!

                              Comment

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