I dont need to monitor cells, just need to drop the pack down to X voltage and disconnect the load relay. This pack is accustomed to 50a discharges during normal use, I plan to do a 1.5-3a slow discharge in 3 steps to prevent polarity reversal, it will be more than safe for it, I just need to disconnect or step at the right volts.
I already know what volt levels I need to step down at, and have already tried it manually.
People have been doing this without Arduino using 3 methods, I feel it can easily be automated on an Ardiuno and a high volt dc relay, using the same loads that people have already proven.
Many people do 4-6 cells at a time using multi-channel RC balancers like hitec x4, while dummy proof and automated, this is extremely time consuming and messy with the need to unwire the whole pack, and still takes several days to perform because these are only able to handle individual cells, not 25-30 in series.
The "manual" method many use: a set of 120v bulbs, starting with a pair of 200w bulbs in series, once the pack dips to 140v a 75w down to 85v, then a 25w bulb down to a 20v final cutoff.
I am no expert, but I can pick up a lot with a little guidance. I have had a few arduinos/RPi for 4-5 years, one is running a remote controlled car, it was a kit, but I had to correct a lot of broken code shipped from china to make it work right, and I am teaching my daughter how to code sketches. I have a couple other little projects, far from expert, but my feet are wet. I work for a company that does commercial/residential automation and IT services, I help manage ~100 servers both windows/linux, I code a number of scripting languages. I have built and installed on and off-grid solar systems (not professionally). I have a couple of soldering irons and 2 shaky hands. When my hands were younger I soldered a ZIF socket in my Honda ECU and burned my own EPROMs for custom tuning, I know how to use Digikey/Mouser ;). I am not great on circuit design, but I have built my own LED lighting from scratch, and nothing burned. So I feel like I have basic electro/mechanical skills and coding skills necessary to do something basic, and with a little guidance, maybe something more complex.
I have a few options for design:
- Set it to disconnect/wait at each voltage level and do a manual swap of the load attached to the relay (200w, 75w, 25w).
- Use 3 relays (pricey)with 3 loads, and I switch on each relay automatically at the desired voltage.
- Build a complex circuit that steps down the load at each configured voltage point, this is ideal, but may be taxing my abilities unless someone really spells out the exact circuit for me. I could probably figure it out on my own after a LOT of trial/errors, time spent would be a deterrent.
I found this 240vdc relay for $65, any cheaper suggestions?... hoping to do the whole project for ~$75.
http://www.electricmotorsport.com/solid-state-relay.html
Here is an example that someone else designed, it does exactly what I need, just at a lower voltage, I have removed a couple items, and the shunt is even optional, I dont necessarily need to track the AH, but I think I might already have a 250v shunt somewhere. The sketch for this circuit already does 99% of what I need, just needs a couple of items trimmed and add my voltage cuts.
