The goal is to keep the battery in my infrequently used car well charged.
I park on a city street with no access to AC power.
I used an inexpensive solar panel (x2) on the dashboard for a couple years; its performance tapered off to failure.
Bought another, same degradation and failure ... in 2 months.
Before that I'd take the battery out ~4X per year and charge it overnight inside.
Time for something new.
For safety and durability I start with some LiFePO4 cells, 4s2p, left over from an e-trike experiment. (These were a lot cheaper 4 years ago).
Active balancer for easy charging on a bench supply.
Feed the ~13V battery output to an adjustable boost converter set for 14.xV output, 6A current limit, 12.5 low V cutout.
Monitor output with a small V & A display.
Attach the output to the car with an OBD power cable, fem connector snipped off & replaced with quick connect.
Replace the fuse in the cable with 7.5A (ATM size) to avoid ever blowing the car's 10A fuse to the comm port.
This gadget will sit in the driver's footwell and charge the car's battery autonomously every few months.
There should be enough capacity in the LiFePO4 battery (20AH) to supply 1-2A overnight.
There's the low voltage cutout to stop it otherwise.
Pictures when I get some more parts in and more assembly.
I park on a city street with no access to AC power.
I used an inexpensive solar panel (x2) on the dashboard for a couple years; its performance tapered off to failure.
Bought another, same degradation and failure ... in 2 months.
Before that I'd take the battery out ~4X per year and charge it overnight inside.
Time for something new.
For safety and durability I start with some LiFePO4 cells, 4s2p, left over from an e-trike experiment. (These were a lot cheaper 4 years ago).
Active balancer for easy charging on a bench supply.
Feed the ~13V battery output to an adjustable boost converter set for 14.xV output, 6A current limit, 12.5 low V cutout.
Monitor output with a small V & A display.
Attach the output to the car with an OBD power cable, fem connector snipped off & replaced with quick connect.
Replace the fuse in the cable with 7.5A (ATM size) to avoid ever blowing the car's 10A fuse to the comm port.
This gadget will sit in the driver's footwell and charge the car's battery autonomously every few months.
There should be enough capacity in the LiFePO4 battery (20AH) to supply 1-2A overnight.
There's the low voltage cutout to stop it otherwise.
Pictures when I get some more parts in and more assembly.