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Tiny cargo trailer to camper/sleeper conversion

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    #16
    Originally posted by 91cavgt View Post
    Battle Born batteries are pretty much the cream of the crop right now! They are some amazing batteries!


    I thought about getting a shunt setup for the cargo trailer but for right now, I’m gonna pass. It won’t be used often enough for me to have to monitor the battery level that closely.


    I too am relatively new to lithium batteries. When the lockdowns started last year I had to stay at home(was a school bus driver) but still got paid. So I bought a bunch of used 18650 batteries and started experimenting. I’ve learned a lot but still have a lot to go.



    One thing that completely confused me this afternoon is I just got back from testing the battery voltage. So last night at this time, the battery was at 14.6 volts. So I turned on 2 fans along with two 12 volt work lights. The battery voltage right now is 14.5 volts!!!! Maybe the battery had a surface charge of 14.9 volts and then settled to 14.6 volts once that surface charge was used up? I’m not sure.


    So I left the fans and lights on. Tomorrow at this same time we will see where the battery is at.

    Does your BMS not have a shunt with it?


    Sent from my iPhone using Tapatalk Pro

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      #17
      Originally posted by Mike D View Post
      Does your BMS not have a shunt with it?


      Sent from my iPhone using Tapatalk Pro


      No, the BMS does not have a shunt. This BMS I bought about a year and a half ago when building your own lithium battery was starting to really take off. At that time, it was rare to have a BMS that had a built in shunt, or even Bluetooth capability the way a lot of them have now. One big problem now with BMSs is due to the chip shortages, they have gone up in price and gone down in availability.

      The BMS that I have is VERY basic. It shuts off power if the voltage of any of the bricks drops below 2.5 volts and it shuts off the battery if the voltage of any of the bricks gets above 4.2 volts. It also will balance the bricks any time the battery is charging. But, it has no low temp cut off(the MPPT charge controller does have it though) and there is no way to really monitor what the BMS is doing without a multimeter. That’s why it was so cheap.

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        #18
        Originally posted by Mbbriggs05 View Post
        Very cool build.......even more interesting is your battery setup. We have camp house that is setup on partial solar since getting shore power to it isn't an option. We have been looking at upgrading batteries and I think this just might be the solution
        If you want to buy pre-built lithium batteries, expect to pay $800-$1,000 for a 100 amp/hr battery from a quality manufacturer like Battle Born. You can find pre-built batteries cheaper from manufacturers like SOK, but they don’t come with as long of a warranty as the Battle Born batteries have. Otherwise, the cheapest ones you can find right now cost around $350-$400 for 100 amp/hr with no really any kind of warranty or customer support.


        There are places that you can buy battery kits from and assemble the batteries yourself in much the same way that I have. Typically you can get some pretty good quality components inside the battery for around $250-$500, but they do not come with an enclosure to put them in. A place I use for this is batteryhookup.com

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          #19
          I have a 6 x12 that I insulated and use as a deer camp . 2 cots fit side by side and there's room for my ac and a couple of totes.. I used a marine battery for power. I run 2 led lights outs side and 2 inside.. I haven't had to charge the battery and my son and I have spent 4 or 5 nights in it so far this season.. I really want to buy one of the cargo toy haulers that's fully furnished. I can't bring myself to buy a rv.. seems like way too much up keep.

          Sounds like your build is a lot more interesting than what I threw together.. I bet it's gonna turn out great..
          Last edited by jds247; 10-11-2021, 06:30 PM.

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            #20
            Thanks! I appreciate the compliments and questions.


            One quick thing I feel that I need to say. My apologies if sometimes what I’m saying in the videos or what I’m typing doesn’t make any sense, or it sounds like I’m talking about something else. I’ve got Parkinson’s and the more tired I am, the more the connections in my head get mixed up.

            So if something I try to explain or describe doesn’t get the job done then just ask again and I can explain it better the next morning.

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              #21
              All this talk about batteries...
              If you go back to that thread I posted up earlier, the guy just added a post (on Sunday) about buying a set of 40 Ah Valence RT Series batteries (with built-in BMS) that are used in crash carts at hospitals. Something about them having to be replaced periodically no matter what condition they are in.

              The specific post is HERE.

              Might be a different option for some when looking for batteries for this type of use. Btw, those batteries have a pretty small footprint: 7.5"H x 7.5"D x 5"W.

              Comment


                #22
                Originally posted by kmack View Post
                All this talk about batteries...
                If you go back to that thread I posted up earlier, the guy just added a post (on Sunday) about buying a set of 40 Ah Valence RT Series batteries (with built-in BMS) that are used in crash carts at hospitals. Something about them having to be replaced periodically no matter what condition they are in.

                The specific post is HERE.

                Might be a different option for some when looking for batteries for this type of use. Btw, those batteries have a pretty small footprint: 7.5"H x 7.5"D x 5"W.

                Valence are some good batteries too, but as you stated, are typically used in the medical industry. So new ones can be VERY pricey, but you can find used ones for a good deal. Here are some that I found here in Texas…….

                https://sanantonio.craigslist.org/fo...386848649.html

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                  #23
                  $480/ea...Wow! That's pretty steep!

                  Comment


                    #24
                    Originally posted by kmack View Post
                    $480/ea...Wow! That's pretty steep!

                    The ad claims they are 138 amp/hr. If that is true then that’s a really great price. If they were 40 amp/hr then I agree that it is pretty steep.

                    Comment


                      #25
                      Originally posted by Mike D View Post
                      Does your BMS not have a shunt with it?


                      Sent from my iPhone using Tapatalk Pro


                      I’ve been thinking more and more about this. As stated earlier, I’m still learning about lithium batteries and I just got reminded that the voltage reading is not a good indicator of the battery level in a lithium battery.


                      The voltage on the battery had dropped down to 13.9 volts with the lights and fans running. The next day I checked and there was no voltage coming out of the battery! The BMS did its job and shut the battery off to prevent it from being drained too low. So I connected up a little 12 volt power supply and immediately it woke up the BMS. The battery voltage showed 11.9 volts.

                      So, just like a lithium powered cordless drill, the voltage of the battery stays high for a MUCH longer time than what a wet cell or AGM battery shows, then it quickly drops as you get closer to using the full capacity of the battery. With a cordless drill, you have full power and your drill doesn’t even slow down until right before the battery dies. Then with almost no warning it shuts off. This battery is performing in the exact same way. So it’s next to impossible to determine the battery level via battery voltage.


                      Because of this, and it was something that I needed to experience myself to be reminded, I ordered a battery monitor with a shunt to better keep track of the battery level.

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                        #26
                        That is exactly why I added a shunt to mine. So I could tell when the battery was getting low and not leave me stranded without a troller.


                        There are some cheaper ones out there that tell basic battery data. Some have a hardface monitor that you can cycle through about 4 different forms of battery data info.

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                          #27
                          Got a little more work done. My wife has kept me busy with other projects so progress has been pretty slow. Please keep in mind that I am not a carpenter! Got the cedar panel mounted on the roof that holds the dome lights. These are off center on purpose. The bed is going to be against the passenger side of the trailer so I wanted the dome lights to be more on the left side. That way, if you are sitting on the bed, the dome lights are in front of you so there won’t be any shadows casted. The dome light in the back was positioned so when the kitchen area is built, it will cast light in that area while avoiding shadows as well. I’m also considering adding other lights to the kitchen area so when the kitchen is swung out, you can still see what you are doing.

                          Another cedar panel got put up that is the transition between the roof and walls. This panel on the driver’s side is also going to house a pair of 4” speakers and a pair of small tweeters. The depth of the 4” speakers that I’ve got is posing a bit of a problem though since I’ve got the 3/4” PVC running in the same space. So, I’ll probably have to shave some material off of the PVC pipe directly behind the speakers to gain clearance while also spacing the speakers out just a bit.


                          Since the battery is built, and the wires for the solar panel are ran inside, I decided to go ahead and temporarily hook up the MPPT charge controller. Starting at 8:00 am, power starts to be put back into the battery. By 9:00 am, the power is up to 5 amps. It peaks out at almost 9 amps going into the battery as the sun gets higher in the sky. By around 4 pm, a shadow from our RV starts to be cast on the panel so power output drops off sharply after that, but is still at more than 5 amps at 4 pm. If it is a sunny day, the charge controller shows an average of 0.5 kWh put into the battery each day. I programmed the charge controller to charge the battery to 14.9 volts bulk, 14.8 volts maintain, and 14.7 volts float.

                          [ame="https://m.youtube.com/watch?v=VIoFY_8xxR8"]https://m.youtube.com/watch?v=VIoFY_8xxR8[/ame]


                          My goal for the next video is to finish putting the cedar planks on the ceiling. This is because I am using a piece of all thread in my makeshift lift the holds the planks in place while they get screwed into place. I’m going to need that all thread very soon for another project (building a 300 amp/hr battery for our RV).

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                            #28
                            Looking great bud! Looking forward to seeing this in it's final stages.


                            I think you'll be really glad you got a shunt for your battery . Some shunts will tell you how much energy you're using at the moment, too. So you can calculate how much time you have left as well as how much battery you have left. As well as what the true energy usage is for each appliance singly or combined.

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                              #29
                              Awesome build! Not sure how I had missed it….

                              Just an FYI for those working on or wanting to work on similar projects. There are what I know as LVD’s (low voltage disconnects) with multiple relay controls… this type of controls permit for load disconnect at different levels… since different levels can be programmed for each relay control you can prioritize what loads you cut off… the ones I was using were in the $150-$200 dollar range…. While it might seem like a lot of money, cutting off loads prior to your batteries getting drained too low will save and extend battery life…. Obviously lithium batteries have built in cut off levels. The beauty of these type controllers is that they do all the work of monitoring your system once programmed….

                              Comment


                                #30
                                Thanks. Yeah, the more I thought about the shunt the more I wanted to add one. The only electrical devices that I’m putting in here are mostly 12 volt devices that by themselves only draw less than 2 amps. However, when they are all added together if they are all on, radio, fan, water pump, lights, battery warmer and device chargers it can add up to 10 amps. But if the power inverter is turned on, all bets are off on how long the battery can last. A 1,000 watt power inverter can easily pull 100 amps. At 100 amps, tre battery wouldn’t last too long.

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