I am looking to purchase a discharge tester I like the Zketech EBC-A40L but it is only up to 5v, other than that it does everything I want. Is there a device that does up to 15v (able to test a nominal 12.8v battery)?
I have been looking for something similar for years. It doesn't exist in the hobbyist price range. The technology has been there to build something like this for a long time but I guess no company feels its worth it or doesn't want to impact sales of their $3000+ devices.
I have researched ways to build something like this and have concluded that the easiest way would be to buy one of the lower end 150V 40A programmable electronic loads, add a programmable DC to DC power supply, and then write the code to communicate with both to monitor and control the charging and discharging processes. The system would have to enable and disable connections using SSRs. This could be done for PC or ESP32/Arduino, but I think the PC route is the right approach since it would allow the PC to store the metrics and chart them in a much nicer way than a stand-alone device. Going lower level such as implementing the load and charger using an ESP32/Arduino would be reinventing the wheel and far more complex. This approach would be limited to 27A @ 14.6V due to their 400W power limitations.
I really would like a higher discharge rate as well such as 50-100A so that larger batteries can be tested in hours instead of days. Loads over 40A are difficult to find for less than $1000. For the most part, they don't exist. Some 60A loads exist but they are up in the $600+ range and are still really limited by a total power rating of 400W or 600W. A 14.6V load at 40A is just under 600W. To get to 14.6V@100A would require dissipation of 1500W of power. A 1500W device could accommodate voltages up to 60V@25A. All of those though would be space heaters.
Even at 40A this would be a lot of work and not worth the investment unless there was enough demand. The total cost of the parts to do this using existing components is under $500. The time to code and test it so that it includes cycle programming by the end user and charting of the curves, is far more time consuming and expensive. There would have to be a market for it. It would be nice to know how much interest there is in something like this though. The cost of the MOSFETs and cooling system would probably be cost prohibitive for hobbyists. You might as well buy one of the many existing commercial versions for thousands of dollars.
In my opinion, the EBC-40L is the ugliest thing on Earth and like you said is limited to 5V and 40A (200W). Its probably understandable why they haven't improved their design to accommodate at least 14.6V batteries @ 40A (600W).
