19 Replies Latest reply on Apr 28, 2020 8:05 PM by colporteur

    Dumb Question

    mark1054

      I am a total newb, so this is probably a really dumb question. I have a DC Harmar scooter lift that I need to be able to run from household current. I need to modify it to make a lift to get my wife off the floor when she falls. I have all the plans to do it, I just don't know what I need to convert the DC to AC. Currently, the lift connects to DC via a standard "trailer" plug. So I need to connect it to a converter that will them plug into a wall socket. I spoke to a guy at Harmar and he seemed to think it was doable as long as the device put out a minimum load of 15amp. Any help would be really appreciated. Thanks!

        • Re: Dumb Question
          Fred27

          What is most important is the DC voltage and current the lift requires. Then it's really a case of finding a suitable power supply. Have you got any more details of the model of lift you're working with?

          3 of 3 people found this helpful
          • Re: Dumb Question
            colporteur

            Welcome to the E14 Community Mark. I don't consider your question dumb by any measure. You have a technical problem and you are asking a community that supports technical people a question in their wheelhouse.

             

            I have a two solutions. My focus is not aesthetics. The solution is easy to create and safe. It is using technology that already exists today.

             

            I would consider an RV battery and a battery charger. The RV battery can be charged using the charger from an AC source without generating toxic fumes. The battery will meet the current and voltage requirements within a range of uses. If the kids are using the device for a amusement ride it won't hold up.

             

            Good RV batteries can provide well over 30amp/hrs. Your current demand is not for hours but for short periods of time. The battery and charger in a plastic tub from a department store, keeps the cost down if the solution has budget constraints.

             

            If you wanted to go all in on just a battery charger, there are units capable of supplying that amperage and more. I did a quick search for battery charger and starter and got this hit. The 25amp rating meets your requirements. Make up some cables (be sure an use 10AWG wire and rated connectors and your good to go.

             

             

            A wall wart power supply is not going to provide the capacity for such a job. A power supply that can provide the current specified is not going to come cheap. Hang around here long enough and a power supply RoadTest review might net you the ideal unit. Some of those suckers can support 40amps. It will just cost you a RoadTest:)

             

            I'm looking at solutions that are DC power supplies in themselves but are used for a specific task. A battery charger is just a DC supply.

            4 of 4 people found this helpful
              • Re: Dumb Question
                dougw

                The charger idea is a pretty robust, low cost solution.

                If the power is simply fed to the motor with a switch, a car battery charger should work without a battery.

                I have an old 16 A charger that has many times been asked to supply over 30 amps (while starting a car).

                I consider it bulletproof - it has been through the war and abused badly, but still works fine.

                At 14.7 Volts it supplies less than 2 Amps, so it doesn't need a voltage limiter/regulator.

                The chargers are about as low cost as you can find. I paid about $30.

                If you want a low cost regulated power supply, the one I have found is an MFJ-4245MV - it works well:

                https://mfjenterprises.com/products/sec-4245mv

                  • Re: Dumb Question
                    mark1054

                    So are you saying I could wire the lift directly to the charger to use it?

                      • Re: Dumb Question
                        dougw

                        If the lift has electronic circuitry, (for example a speed controller) it may need a regulated voltage.

                        If the lift control is just a switch, it should work, as the charger is able to power DC motors.

                        Can you describe the controller and what it does?

                        If you want to try it, have someone knowledgeable look over your wiring and explain the charger voltage is unregulated - not clean DC.

                        • Re: Dumb Question
                          colporteur

                          I have concerns with your experience level. That being said this is not a complicated project. If you have tried starting a car with booster cables and didn't cause damage during the process then you have knowledge of what you are trying to do. If you fried either car electrical system in your booster attempt then don't attempt this.

                           

                          If you are going to use the charger to power the lift, then I recommend the charger has some safety features. Some old chargers had no protection circuits. The circuit breaker in the house tripping was the only indication there was a problem. The safety circuits in the charger are providing protection. Yeah you can depend on tripping the house breaker but don't. If the lift draws to much current your expecting the charger protection circuits to work and shut the system down.

                           

                          If you screw up the polarity of the connections between the devices one or both of the devices will give up their magic smoke that allows them to work. Your not guessing or working on an I think this is right. Be sure.

                           

                          The charger needs to be capable of supporting the load. Check the specifications. Ensure the cables are sufficient to handle the current load. Like I indicated you need a minimum of 10 awg but that is the electrical code in my area. Ensure the switch is rated to handle the load. The connections have to be mechanically and electrically sound. All connections need to be well insulated.  Your not just twisting two wires together and wrapping it with gaff tape.

                           

                          I'm trusting you are not using this around water. This is not a 9V battery your sticking your tongue on. Your talking some pretty serious current that has the potential to do some damage. Don't overlook safety just so you can have it working. The charger is just a fancy power supply it can do the job if done correctly.

                          1 of 1 people found this helpful
                          • Re: Dumb Question
                            Fred27

                            I'd be very wary of trying to use just a battery charger to operate the lift. A battery charger is designed to provide a low current (for slow charging) over a long period of time. A car battery is capable of short burst of very high power. It can even melt a spanner if you short out the terminal with one!

                             

                            I was going to suggest the same as Sean - use a battery for the heavy lifting and a charger to slowly recharge it between uses.

                             

                            There are devices designed to starts cars from mains power and provide a large amount of power. This may also do the job but is likely to be a more expensive solution.

                      • Re: Dumb Question
                        Fred27

                        This really isn't a dumb question. Maybe it's worth changing the title! It also makes it easier for someone to find useful information if they have a similar question.

                        • Re: Dumb Question
                          mark1054

                          It kinda sounds like the easiest way to do this would be with an external battery and trickel charger, Yes?

                          1 of 1 people found this helpful
                            • Re: Dumb Question
                              kmikemoo

                              mark1054 YES!  Go for the battery and the charger.  It's simple and what the system was designed to use.  I also do not believe that a battery charger will run your lift, but you might try the following item - or something similar.

                              https://smile.amazon.com/BMOUO-Universal-Regulated-Switching-Computer/dp/B01EWG6YT8

                              It's not a bench top power supply.  It's just power.  I have one for my ham radio.  I have a 24VDC one that I use for vehicle diagnostics when the starting batteries are dead.  At $20 USD... it's worth trying out.

                              • Re: Dumb Question
                                colporteur

                                Yep. Provided you are not deep discharging the battery a trickle charger would do the trick (pun intended).

                                 

                                I have a friend that uses the arrangement to run a radio transmitter to broadcast infrequent short messages. The battery is the radio supply and the trickle charger keeps it working.

                                 

                                Actually they just had to replace the battery after eight years of operation. No heat in the enclosure tends to reduce the life of the battery.