I recently bought a Viofo A129 Duo for my car (15 year old MG). I use the 3fps timelapse parking mode with a 256GB memory card so I have enough storage for several days worth of parking mode recording. I'm using the 3-wire hardwire kit. Unfortunately I found the parking mode only lasted for 18-24 hours before the voltage cut-off kicked in, even at the lowest setting of 11.8V (the battery was a normal flooded lead-acid, 60AH, 3-4 years old). I planned and experimented with several solutions to extend the duration of the parking mode recording, here's what I tried and my end solution. Hopefully this is useful for some other people, might save you some trial and error.
Solution 1: Buy a 20'000mAh Anker powerbank, use some DIY circuitry so it automatically charges while the engine is running and powers the dashcam when car is parked. A cheap and easy-ish solution, however some DIY circuitry required because most powerbanks don't support pass-through charging (charging while also powering something). That would have made things much simpler but anything that supported pass-through charging was much more expensive. I decided to do a test run before I built the switching circuit, my girlfriend has a new 20'000mAh Anker so I charged it up and plugged in the dashcam (indoors for testing). After a few test runs from full charge to empty, results were in the 24-30 hour range, only 6-12 hours better than the car's battery, not good enough, and this was cool indoor temperatures, inside the car in summer would be worse. Also, the Anker took 6-8 hours to fully charge, this is too slow for my usage, it needs to get most of the way to being charged in 1-2 hours.
Solution 2: Build or buy multiple 3.7V (5V input) charging circuits. Power them via 12V->5V buck converters (DC-DC voltage converter) and use them to charge multiple 3.7V 26650 lithium cells (1 charger for 1 cell). Attach the cells to the load (dashcam) in parallel and use a 3.7V->12V converter. As each cell gets its own charging circuit the total input/charging current can be quite high depending on how many cells I have, and in parallel they are self-balancing on discharge. So basically the same as solution 1 except I can add a large numbers of cells and charge much more quickly. The downside is much more DIY work involved in initial setup.
Solution 3: Buy a 4S (14.4V) LiPo battery pack and a balancing charger that accepts 12V input. Connect the battery pack directly to the load. Benefits here are simplicity, no voltage converters, the cells are balanced automatically during charging so no need for any load sharing during discharge. Probably more reliable than solution 2 and slightly easier to set up but not as easy as solution 1. Slightly more expensive than either solutions 1 or 2.
Solution 4: Buy a Cellink or Blackvue. Extremely simple (not sure about reliability) but also more than double the cost of the other solutions for similar battery capacity. Possibility to add DIY extension batteries but then this solution loses it simplicity.
Solution 5: Upgrade the car battery to an AGM battery. Biggest capacity that will fit in my car is 60AH. They can be charged quite quickly and are generally more durable than normal lead-acid batteries. Just as simple as solution 4 but a lot cheaper, although still more expensive than solutions 1,2,3.
After some internal debating and speaking to friends I went with solution 5 and I'm very happy with my choice. AGM battery cost me £115 delivered, swapping car batteries is pretty simple. I've now set the voltage-cut off in the hardwire kit to 12.2V to protect the battery and I'm consistently getting 48+hrs before it cuts off the dashcam. If I'm planning to leave the car for an extended period (e.g. going on holiday) I will set the voltage cut-off to 11.8V and be prepared to jump-start the car if necessary but those will be on rare occasions. If I decide later I need even more capacity I will revisit solution 3 because it's the simplest that will also allow easy upgrade of capacity and charge rate in future.
Hopefully some people will find this helpful.
Solution 1: Buy a 20'000mAh Anker powerbank, use some DIY circuitry so it automatically charges while the engine is running and powers the dashcam when car is parked. A cheap and easy-ish solution, however some DIY circuitry required because most powerbanks don't support pass-through charging (charging while also powering something). That would have made things much simpler but anything that supported pass-through charging was much more expensive. I decided to do a test run before I built the switching circuit, my girlfriend has a new 20'000mAh Anker so I charged it up and plugged in the dashcam (indoors for testing). After a few test runs from full charge to empty, results were in the 24-30 hour range, only 6-12 hours better than the car's battery, not good enough, and this was cool indoor temperatures, inside the car in summer would be worse. Also, the Anker took 6-8 hours to fully charge, this is too slow for my usage, it needs to get most of the way to being charged in 1-2 hours.
Solution 2: Build or buy multiple 3.7V (5V input) charging circuits. Power them via 12V->5V buck converters (DC-DC voltage converter) and use them to charge multiple 3.7V 26650 lithium cells (1 charger for 1 cell). Attach the cells to the load (dashcam) in parallel and use a 3.7V->12V converter. As each cell gets its own charging circuit the total input/charging current can be quite high depending on how many cells I have, and in parallel they are self-balancing on discharge. So basically the same as solution 1 except I can add a large numbers of cells and charge much more quickly. The downside is much more DIY work involved in initial setup.
Solution 3: Buy a 4S (14.4V) LiPo battery pack and a balancing charger that accepts 12V input. Connect the battery pack directly to the load. Benefits here are simplicity, no voltage converters, the cells are balanced automatically during charging so no need for any load sharing during discharge. Probably more reliable than solution 2 and slightly easier to set up but not as easy as solution 1. Slightly more expensive than either solutions 1 or 2.
Solution 4: Buy a Cellink or Blackvue. Extremely simple (not sure about reliability) but also more than double the cost of the other solutions for similar battery capacity. Possibility to add DIY extension batteries but then this solution loses it simplicity.
Solution 5: Upgrade the car battery to an AGM battery. Biggest capacity that will fit in my car is 60AH. They can be charged quite quickly and are generally more durable than normal lead-acid batteries. Just as simple as solution 4 but a lot cheaper, although still more expensive than solutions 1,2,3.
After some internal debating and speaking to friends I went with solution 5 and I'm very happy with my choice. AGM battery cost me £115 delivered, swapping car batteries is pretty simple. I've now set the voltage-cut off in the hardwire kit to 12.2V to protect the battery and I'm consistently getting 48+hrs before it cuts off the dashcam. If I'm planning to leave the car for an extended period (e.g. going on holiday) I will set the voltage cut-off to 11.8V and be prepared to jump-start the car if necessary but those will be on rare occasions. If I decide later I need even more capacity I will revisit solution 3 because it's the simplest that will also allow easy upgrade of capacity and charge rate in future.
Hopefully some people will find this helpful.