No announcement yet.

Simple $20 Charger Extension Cable and Data Display

  • Filter
  • Time
  • Show
Clear All
new posts

    Simple $20 Charger Extension Cable and Data Display

    I wanted a longer cable on my charger, as well as the ability to easily monitor charge process parameters. I'd been using a DVM for voltage, ever since the voltmeter in my charger quit working. Then GeorgeS pointed out this neat little power meter: Bayite DC 6.5-100V 0-100A LCD Display Digital Current Voltage Power Energy Meter Multimeter Ammeter Voltmeter with 100A Current Shunt

    It even tracks energy throughput. Neat.

    So ordered one. I rigged up a 5' long charger extension cable with the meter wired in-line. It's dead simple to set up. No configuration required.

    The left Zip-tie is out of position here, sorry - it's 55.63V, 279.2W:

    I haven't checked accuracy yet, but my Luna Charger is set at 5A, above. That's gotta be close.

    Shunt is inside the yellow heat-shrink:

    XT60 connectors on each end. The short cable goes to the battery, long one to charger.:

    Wiring details. Left end to battery:

    This is neither pretty, compact, nor waterproof. But it works fine for indoor bench use. I also have a Batt Man (a much nicer waterproof unit with data-logging capability) on my eBike, but it's not set up for charge monitoring, so this project rounds out my basic instrumentation. It is a nice addition to the eBike kit.

    There are other, similar meters with lower amperage ratings (smaller shunts) which would have superior accuracy. Maybe look at those if you will only use it for charging. I wanted the higher capacity in case I re-purpose it later - that tends to happen around here.
    Last edited by JPLabs; 08-05-2016, 07:11 AM.
    Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.

    You can use something like 4 conductor jacketed telephone or alarm wire from the shunt out to the meter, very small wires. I want to use the meter on bikes because it is very easy to read and is exactly what I want for info, but it's not ideal or user friendly. I leave the shunt with the battery and run a wire to the handlebars. I'm using the same connectors. It's annoying that there is a source and load side to the meter, so different connectors for charge and discharge. I buy the pigtails and connect two of the same gender together, which effectively swaps the M/F.


      I've been looking at that same display on Amazon and have pondered putting it on the bike. The ability to put the shunt inline with the high current wiring between battery and motor and not run the those wires to the handlebars and back is one of the big motivations. Lack of waterproofing is a small issue, it could be sealed inside a project box with a clear lid, but just having more stuff on the handlebars is a negative for me. Even with that I'm tempted to get one to attach to the bike to use for new or extreme rides, with the idea that over time I'll have developed a better for feel on how things work. When not on the handlebars I'd route it into one of the panniers in back to be there if I want to look, but not have it taking up handlebar space.

      I've got some of the marine sealant-filled shrink tubing that would be just the thing sealing up that shunt.


        those little hoes on the displays box look like zip tie mounting access through the box. ??? Maybe not, your probably not as dumb as me! Great post, clear pictures, I will add this to my Lunagizer! My latest tactic to guess the battery level stuff is buying a 52v 25ah GA battery! Then I'll mount my shark battery on the down tube! Can we mix different 52v batteries plugged in together? Or use them separately? thanks for the great post. E-rod


          Nah, I'm not quite that dumb, most days;). Those are clips to lock it into a hole in a panel, for flush mounting.

          My opinion of some things to consider:

          As far as mixing pack types in parallel goes, my understanding is that it can be done if 2 main conditions are satisfied. The main risk is that a large current will pass from one pack into the other if their voltages deviate:
          1 - the pack voltages must match very closely when you connect them. This is critical. Like within .01V or perhaps less, depending upon packs and BMS. Current = (Voltage Difference)/(internal resistance).
          2 - the packs must have similar internal resistance, sag under load, and capacity vs. voltage. You don't want them to be very different, or the 2 pack's voltages or SOC can deviate under load, and then you will no longer meet #1. Alternately, if the total load (amps) exceeds either of the pack's BMS, and current draw is unbalanced, you could trip one BMS, then the other, without ever exceeding the total amp capacity of the paralleled packs.

          Small pack differences should be OK; the packs will quickly re-balance to recover from SMALL differences. So, better/safer if used well under their amp rating, if the 2 packs are not quite matched but are paralleled together anyway. But not big differences

          Those are the main issues, I think.
          Last edited by JPLabs; 04-01-2016, 06:45 PM.
          Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.


            Thanks so much for your advice. I can see that I better not mix batteries at my level of knowledge. Easy enough to use one at a time. What a gas I'm having on this bike! Can't wait for a big GA battery!



              I don't mean to completely discourage you. If 2 packs are same the chemistry, same voltage, and in good condition, their relevant properties should match fairly well. If they both have BMS then they should be pretty safe to test in parallel, as long as you start with both at equal voltage before connecting them. I wouldn't be afraid to try it myself, if those basic conditions are satisfied. But if you do, do at your own risk.

              What I would not do is combine packs with different chemistries, or combine old and new packs. Some people even do that, but they need to be extra careful.

              Especially, don't ever connect 2 packs without matching the voltages first. I've seen advice to run parallel that 'suggests' matching the voltage first. I'd say that equalizing the voltage first (charge fully is the easiest way) is an absolute requirement, not just a suggestion.

              Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.


                4 month update: My meter stopped working, after 4 months of use. Displays only 88.88 for all values, now. BUT: The seller, Bayite, replied in a day, stood behind the product, and had me taken care of with a replacement coupon code within 2 days. Good Seller!

                Electronics failures tend to be sporadic for things like this. Don't let my one failure scare you off this meter. It's certainly not common, based upon all the buyer feedback.

                Again, nice find, GeorgeS!
                Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.