Mosaic
Well-Known Member
Hi all:
I'm doing a project to smart charge LA auto batteries. This means MCU control. I am building it around a salvaged microwave transformer. Now these transformers tend to operate in saturation, I'm compensating by adding a small air gap between the I and E laminations with JBweld.
Anyway I am posting the LTspice design thus far. It features PWM constant current & constant voltage control, hardware current limit and s'ware limit. Inrush current limit. No spark connection to the battery and I plan to add a SPDT relay to dynamically adjust the input Xformer voltage tap for higher current, lower voltage, lower heat dissipation charging of very weak 12v (or 6V ) batteries.
I expect to add a constant current discharge module to provide for calculating true Battery internal resistance and infer cold cranking amps. Further, the constant current discharge can derive genuine Peukert indices for determining ampere hour capacity. This permits the charger to rerate every battery it charges accurately.
The MCu will be able to report to a PC via rs232 over USB to archive battery data and history, which could be useful for tracking deep cycle marine or maintenance of a bank of UPS batts.
For heat mgmt I have a serious finned heatsink about 5" by 5.5" square with tapered fins, 3/8" thick aluminum base. A 120mm 12V PC fan is strapped to this.
The charger is to be a 6 stage:
1) Constant (bulk charge) current
2) Constant Voltage
3) Float charge
4) Partial controlled discharge & surface charge dispersal.
5) Equalise charge based on int. res & Ah calcs
6) Cyclical temp monitored discharge-charge-pulse equalize for desulphation battery recovery.
Thermistors to be used on the battery and the Darlington driver to monitor temp rise over ambient. Battery charging regimens for Flooded wet cell, AGM, and Gel cells with temp compensation.
It's a bit ambitious but I hope to get pointers from the forum ....so pitch in!
I'm doing a project to smart charge LA auto batteries. This means MCU control. I am building it around a salvaged microwave transformer. Now these transformers tend to operate in saturation, I'm compensating by adding a small air gap between the I and E laminations with JBweld.
Anyway I am posting the LTspice design thus far. It features PWM constant current & constant voltage control, hardware current limit and s'ware limit. Inrush current limit. No spark connection to the battery and I plan to add a SPDT relay to dynamically adjust the input Xformer voltage tap for higher current, lower voltage, lower heat dissipation charging of very weak 12v (or 6V ) batteries.
I expect to add a constant current discharge module to provide for calculating true Battery internal resistance and infer cold cranking amps. Further, the constant current discharge can derive genuine Peukert indices for determining ampere hour capacity. This permits the charger to rerate every battery it charges accurately.
The MCu will be able to report to a PC via rs232 over USB to archive battery data and history, which could be useful for tracking deep cycle marine or maintenance of a bank of UPS batts.
For heat mgmt I have a serious finned heatsink about 5" by 5.5" square with tapered fins, 3/8" thick aluminum base. A 120mm 12V PC fan is strapped to this.
The charger is to be a 6 stage:
1) Constant (bulk charge) current
2) Constant Voltage
3) Float charge
4) Partial controlled discharge & surface charge dispersal.
5) Equalise charge based on int. res & Ah calcs
6) Cyclical temp monitored discharge-charge-pulse equalize for desulphation battery recovery.
Thermistors to be used on the battery and the Darlington driver to monitor temp rise over ambient. Battery charging regimens for Flooded wet cell, AGM, and Gel cells with temp compensation.
It's a bit ambitious but I hope to get pointers from the forum ....so pitch in!
