This is probably a topic for an LS swap forum, but posting here since lots of folks are V8 swapping 60s.
Problem: Gen4 swaps that dont have a BCM cannot control the alternator output voltage, defaulting it low (~13.5-13.8v). This voltage may be fine for most swaps, but was undercharging my battery. The 2 wire OEM alternator needs a 128Hz PWM signal, with Duty Cycles corresponding to output voltage:
10% 11 V
20% 11.56 V
30% 12.12 V
40% 12.68 V
50% 13.25 V
60% 13.81 V
70% 14.37 V
80% 14.94 V
90% 15.5 V
Solution space: BCM from your swap vehicle, BCM emulators, cheap chinese PWM devices, one wire alternators or DIY.
My DIY solution: small custom PCB, with automotive rated components for engine bay temp, automotive wiring, and a simple dial adjustment.
Board design
The design uses a small linear regulator for the 12v-5v and a LTC6992 oscillator for the PWM output.
Originally I had hoped to have this powered by the 5v that was coming from the ECM, but it proved unreliable. V2 will remove the dual voltage capability. 12V + GND input, 5v PWM output. This one is adjustable between ~66%-80% duty cycle (~14v-15v) with a small pot, as that is the range I wanted to be variable.
Assembly:
First prototype (my SMT hand soldering needs work, but its functional!)
Hard to see, but duty cycle measurements, frequency and voltage all about right. I should have screen captured from the scope, but my phone was on me
Problem: Gen4 swaps that dont have a BCM cannot control the alternator output voltage, defaulting it low (~13.5-13.8v). This voltage may be fine for most swaps, but was undercharging my battery. The 2 wire OEM alternator needs a 128Hz PWM signal, with Duty Cycles corresponding to output voltage:
10% 11 V
20% 11.56 V
30% 12.12 V
40% 12.68 V
50% 13.25 V
60% 13.81 V
70% 14.37 V
80% 14.94 V
90% 15.5 V
Solution space: BCM from your swap vehicle, BCM emulators, cheap chinese PWM devices, one wire alternators or DIY.
My DIY solution: small custom PCB, with automotive rated components for engine bay temp, automotive wiring, and a simple dial adjustment.
Board design
The design uses a small linear regulator for the 12v-5v and a LTC6992 oscillator for the PWM output.
Originally I had hoped to have this powered by the 5v that was coming from the ECM, but it proved unreliable. V2 will remove the dual voltage capability. 12V + GND input, 5v PWM output. This one is adjustable between ~66%-80% duty cycle (~14v-15v) with a small pot, as that is the range I wanted to be variable.
Assembly:
First prototype (my SMT hand soldering needs work, but its functional!)
Hard to see, but duty cycle measurements, frequency and voltage all about right. I should have screen captured from the scope, but my phone was on me
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