Setting Fardriver for weak battery Part 2. Setting MaxSpeed (mode 3) and Ratios in speed (Boost)

The battery is 13s5p 18650 using high capacity (3400 mah) but low power (5a continuous cells). So the maximum continuous should not exceed 25a, max 30 seconds 50a, peak 60a. Note that 60a creates a large voltage sag, and that means the cells will heat up quickly, so this should only be for a few seconds. In the fardriver, max amps is set with Max Line Current, and then MaxSpeed rpm is used to pull current down to maximum continuous of the motor or battery, which’s is the weakest link. If you wire boost, you can set max boost line current to the max your battery can handle for a few seconds, then use ratios in speed to pull that down to maximum 30 seconds current, then set the timer to kick you back into mode 3 where it will go back to MaxSpeed setting which is set for less than 25a line current. 0:00 Setting Fardriver for a weak Battery part 2 0:50 using gps app so I can know what rpm limit I need in the Fardriver app 1:27 looks like 38 kph for mode 3 speed. 1:37 I know from yesterday that only used about 10a, so I want to try 50 kph. 2:00 so i increase rated speed from 600 to 725 rpm and save it. 2:30 lets see what speed it maintains now. 2:54 only 47 kph but lets check how many amps that is. 3:52 Looks like only 17a, so I can afford to bump speed up to 50 kph. 4:35 I bump MaxSpeed up from 725 to 750 rpm 4:57 back to GPS app to see if its close to 50 kph now. 5:18 49 kph, close enough. The max legal speed for ebikes is 50 kph so this is fine. 5:46 back to Fardrive Graph page to see what our cruise amps are now at 750 rpm (49 kph) 5:57 we see our amps climbs to maximum continuous line amps (50a) during acceleration 5:59 then we see line amps decrease at 44 kph so it doesn’t overshoot maxspeed too much. 6:04 finally we see it settle around 20a @49 mph. Perfect. Below 25a max continuous, below 50 kph max legal speed. 6:47 now to set the speed limit for boost, using ratios in speeds, since boost overrides MaxSpeed rpm 7:04 first we will set everything 100% up to 600 rpm 8:06 we will begin the taper at 700 rpm, 50%. 50% of 200a is 100a so it will not have any restriction of speed. 8:12 800 rpm is set to 25%, which limits phase amps to 50a. It will barely affect speed. 8:22 900 rpm is set to 0%. So this means the real rpm control will be between 800-900 rpm. 8:26 Now set all rpm 1000 and up to 0%. 9:31 you can see boost is activated and we have 60a for acceleration 9:39 you can see ratios in speed settings have choked the amps and speed settled ar 835 rpm (53 kph) and 25a cruise. 9:56 field weakness is disabled, but we use ratios in speed as the boost rpm limit. One of its many functions. 10:15 Now the Fardriver is set, lets see whats going on inside my 💩 battery using my 💩 JBD bms 10:47 you can see a high cell difference (0.098v), mainly because of cell group one voltage sag. 11:35 here we see 70a discharge spike and 0.135v difference, but its due to cell group #1. 11:45 the process could actually be a dead cell in cell group 1, but most likely its just due to cheap construction….. 11:55 …this is because the series busses were designed for 15a bms and controller, not 60a…. 12:05 …so since I have 12AWG from the battery (-), which is cell group 1, and 16awg equivalent series bus…. 12:15 …it allows cell group one to be discharged faster than the other cells… 12:25 …A good battery, with proper series busses, will NOT do this… 12:35 …and every REAL ebike battery has a Bluetooth BMS so you can check it…. 12:45 …on a good battery, cell differential will rarely exceed 0.020v under rated continuously discharge… 12:55 …but if you don’t have a Bluetooth bms or cell monitor, you will never know whats going on inside under max discharge… 13:05 …JBD is 💩 but better than any non-Bluetooth BMS. 15:43 Seems overkill solar needs internet to connect so its now total 💩 in my bms app rating. Lol 16:20 This app is not so bad, lets give it a test 17:05 app seems ok, its the JBD that has the slow refresh rate. 17:14 you can see at 68a the cell differential is all over the place. This app shows it more clearly with the length of the blue bars 18:22 this is the official app but needs internet to get full features. Without internet you get only 0.01v resolution 19:55 The low resolution is still enough to see what a 💩 battery this is. In some cases its easier to see the tangible difference 21:30 unfortunately this app is best for 12v or 24v batteries, mainly for solar. 22:04 the dashboard is ok but missing cell differential which is often the first indicator of a problem. 23:01 Back to Graph, observe the behavior of phase amps to understand when ratios in speed will actually limit them.. 23:18 60a line and 400 rpm and phase amps is already below 100a and will continue dropping as rpm increases… 23:30 …this means I could set 400RPM ar 50% with max phase amps set to 200a, and it will not affect me. 24:00 ..in the future I will have a powerful battery that can support field weakening and show how to use ratios in speed to stabilize that.