Kingfish
100 MW
Greetings –
This brief describes how to calculate the resistance of R1 for the various nominal operating voltages between 36V and 74V (10S to 20S) for the Infineon controllers.
There are two presumptions:
Though some utility can still be achieved up to 74V with resistors, for voltages above 60 it is considered more efficient to use a switching DC-DC converter/circuitry if room can be afforded.
LV and HV limits are based upon moderately safe LiPo cell operation ranges.
Formulas:
Table:
[pre]Volts Ohms LV HV LiFePO4 LiPo
36 100 29.19 40.48 x
37 113.89 30 41.6 10S
43 197.22 34.86 48.35 12S
48 266.67 38.92 53.97 x
55 363.89 44.59 61.84 15S
56.8 388.89 46.05 63.86 16S
60 433.33 48.65 67.46 x
64 488.89 51.89 71.96 18S
72 600 58.38 80.95 x
74 627.78 60 83.2 20S
85 780.56 68.92 95.57 24S[/pre]
Notes:
Some resistance values are difficult to locate. Example: It is pretty common to find two 2W 201-Ohm resistors in parallel to get the ~100 Ohm value on a 36V controller. You may need to get creative to find your best match
Citations:
Reviewed and checked by Justin at ebikes.ca. There’s a short topic on the subject just below the Regen section here; scroll to the heading “How do I modify the controller for more than 48 Volts?â€Â
Best of luck, KF
-- Ypedal edit to add Infineon reference.
This brief describes how to calculate the resistance of R1 for the various nominal operating voltages between 36V and 74V (10S to 20S) for the Infineon controllers.
There are two presumptions:
- At 36V, R1 = 100 Ohms (2-3W)
At 72V, R1 = 600 Ohms (3-4W)
Though some utility can still be achieved up to 74V with resistors, for voltages above 60 it is considered more efficient to use a switching DC-DC converter/circuitry if room can be afforded.
LV and HV limits are based upon moderately safe LiPo cell operation ranges.
Formulas:
- Ohms = ((V / 36) * 500) – 400; slope given as y = 500x – 400
- LV = (V / Vn) * Vl; (V / 3.7) * 3.0
- HV = (V / Vn) * Vh; (V / 3.7) * 4.16
where V = Volts, Vn = Cell-Volts nominal, Vh = Cell Volts-high limit, Vl = Cell-Volts low limit
Table:
[pre]Volts Ohms LV HV LiFePO4 LiPo
36 100 29.19 40.48 x
37 113.89 30 41.6 10S
43 197.22 34.86 48.35 12S
48 266.67 38.92 53.97 x
55 363.89 44.59 61.84 15S
56.8 388.89 46.05 63.86 16S
60 433.33 48.65 67.46 x
64 488.89 51.89 71.96 18S
72 600 58.38 80.95 x
74 627.78 60 83.2 20S
85 780.56 68.92 95.57 24S[/pre]
Notes:
Some resistance values are difficult to locate. Example: It is pretty common to find two 2W 201-Ohm resistors in parallel to get the ~100 Ohm value on a 36V controller. You may need to get creative to find your best match
Citations:
Reviewed and checked by Justin at ebikes.ca. There’s a short topic on the subject just below the Regen section here; scroll to the heading “How do I modify the controller for more than 48 Volts?â€Â
Best of luck, KF
-- Ypedal edit to add Infineon reference.