My solution for parking mode power for 48+ hours

Ormy

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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.
 
Not sure that 3 works well, the charging rate is likely to be too low, and reliability may not be as good as 2 due to the balancing required, and it is likely to be rather expensive compared to 2.

2 should be a good solution but needs quite a bit of DIY effort.

5 is an easy solution, only real issue is that the battery will not last nearly as long as a lithium battery so in the long run will be more expensive, but you do get a really high charge rate at little cost.

What MG is it? Most would have a diesel engine battery option with a rather larger battery, you may need to change the battery tray and mount but it should be fairly easy to fit a larger battery to all except maybe a TF, but I would have thought there was plenty of room for a larger battery in the TF since it doesn't have an engine under the bonnet!

Unless you make long trips regularly, you should give your AGM battery a 100% charge on a battery charger at least once every 3 months. Otherwise it is likely never to reach 100% since the last bit of charging is very slow, and lead acid batteries need a 100% charge occasionally to clean the plates, not so important for AGM but still worth doing.

Low voltage cutoff at 11.8V should be no problem, my car (another MG) will start on only 11.3 from an AGM battery. Most AGM batteries are happy to go down to 11.8 and will charge much faster at that voltage than at higher voltages.
 
Awesome job. I currently have option 4 and get approximately 60 ish hours. I went with LiFePO4 batteries and avoid LiPo packs as I don't feel like dealing with the higher risk even vs the common LiCoO2.

On solution 3, I've searched for a high current output 12v dc - dc charger for LiFePO4 and found nothing cheap. I've checked solar chargers and all. Do you know of a solution? I want to build a backup battery but not rely on the expensive Neo/b124 chargers. I found one but it only charges at 1.5 amps @ 12V. I have many hobby chargers that can handle that very easily but it is impractical to activate it every time I start my vehicle.

I'm limited to the 9A charge as the NEO9 isn't available in the US.
 
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Not sure that 3 works well, the charging rate is likely to be too low, and reliability may not be as good as 2 due to the balancing required, and it is likely to be rather expensive compared to 2.

The hobby/RC chargers I was looking at (cheap ones) could handle up to 6A. I thought maybe run 2 chargers and 2 battery packs in parallel for 12A but then cost again becomes an issue. Reliability/balancing depends on the quality of the charger, but even the cheap ones do a pretty good job these days.

5 is an easy solution, only real issue is that the battery will not last nearly as long as a lithium battery so in the long run will be more expensive, but you do get a really high charge rate at little cost.

In terms of number of charge cycles yes lithium will last longer but if I went with lithium it would likely end up doing a full charge-discharge cycle almost every day. With AGM and voltage cutoff at 12.2 I'm not fully discharging the battery (12.2V corresponds to about 40% charge remaining) so I would expect 5-6 years of usage. Should I be expecting significantly less? I've done a fair amount of research but this is my first hands-on experience with AGM technology. If its more like 3-4 years I can accept that. If it only last 2 years or less I may have to choose another solution when it dies.

What MG is it? Most would have a diesel engine battery option with a rather larger battery, you may need to change the battery tray and mount but it should be fairly easy to fit a larger battery to all except maybe a TF, but I would have thought there was plenty of room for a larger battery in the TF since it doesn't have an engine under the bonnet!

ZR 160 mk1, the original battery was a 075, the AGM I bought is 027 (15mm taller but otherwise the same). There is some space in front of the battery, I could have made a 096 fit (30mm longer than 027 and 15Ah more capacity) which I think is what the diesels take. However I use that space for my air-horns and don't really to want to mess about finding another space for them, no other spaces in the engine bay, would have to remove bumper and mount somewhere, maybe in the future. Besides if I decide I need a bigger battery I might move the battery and engine-bay fuses to the boot and then I can have the battery as big as I like, size 334 or a full on caravan battery, weight would be the limiting factor then.

Unless you make long trips regularly, you should give your AGM battery a 100% charge on a battery charger at least once every 3 months. Otherwise it is likely never to reach 100% since the last bit of charging is very slow, and lead acid batteries need a 100% charge occasionally to clean the plates, not so important for AGM but still worth doing.

I do a 150 mile trip (2.5-3 hours, London to Yorkshire) and back the next day every 2 or 3 months. That should keep me covered right?

Low voltage cutoff at 11.8V should be no problem, my car (another MG) will start on only 11.3 from an AGM battery. Most AGM batteries are happy to go down to 11.8 and will charge much faster at that voltage than at higher voltages.

The old battery would start the car happily from 11.8V after voltage cutoff kicked in. However one day I noticed something funny with the electric windows, stupidly I ran the window up and down a few times before starting the engine. Since the battery was already down to 11.8V, after running the window a few times the engine wouldn't start and I was late for work haha. Don't want to risk it right now but might do some testing with lower cutoffs when I have some time off work. Besides all the stuff I've been reading about AGM says their capacity is down to 25% at 12.0V and 0% and 11.8V so how the hell is it cranking your engine with only 11.3V? These AGMs are crazy.... Which MG do you have?

Your comments are much appreciated thanks Nigel.
 
You can go down to 11.8 V on a battery and also start it, but that might not happen on a cold winter morning.
Personally i would not go under 12 V and i would prefer to use 12.2 V for my cut off.
 
Awesome job. I currently have option 4 and get approximately 60 ish hours. I went with LiFePO4 batteries and avoid LiPo packs as I don't feel like dealing with the higher risk even vs the common LiCoO2.

Thank you. From what I read LiPo and LiFePO4 are lower risk when it comes to higher temperatures and brief periods of fast-charging compared to Li-ion but there's not much in it between LiPo ad LiFePO4. Maybe I misread that stuff or need to do more research? I'm not an RC-hobbyist, just a general electronics tinkerer :)

On solution 3, I've searched for a high current output 12v dc - dc charger for LiFePO4 and found nothing cheap. I've checked solar chargers and all. Do you know of a solution? I want to build a backup battery but not rely on the expensive Neo/b124 chargers. I found one but it only charges at 1.5 amps @ 12V. I have many hobby chargers that can handle that very easily but it is impractical to activate it every time I start my vehicle.

Yes the high current models are too expensive to be practical for this kind of thing, for that money you might aswell just buy a Cellink/Blackvue like you did. Most cheap chargers are built around IC LM317 (a voltage regulator with 1.5A limit), you could reverse-engineer one using the LM317's bigger brothers, the LM338 (5A limit) or LM396 (10A limit), or design your own circuit using these ICs. I found a TON of useful information on designing charging circuits including detailed calculation, circuit diagrams, PCB plans etc at the link below. Another solution would to just buy several of the 1.5A pre-built circuits and connect them together in parallel with some diodes&resistors to protect them from each other.

In terms of 'activating' something every time you start the vehicle, that's easy to solve. Just wire whatever you want to 'activate' through a relay controlled by any 12V source that's only 'on' when the engine is running. I have all sorts of things in my car running through relays that switch on when Acc (ignition signal) comes on.

Thanks for your comments EsQueue much appreciated.

https://www.homemade-circuits.com/how-to-make-current-controlled-12-volt/ Not just that article, the entire site is filled with extremely helpful circuit building guides.
 
The hobby/RC chargers I was looking at (cheap ones) could handle up to 6A. I thought maybe run 2 chargers and 2 battery packs in parallel for 12A but then cost again becomes an issue. Reliability/balancing depends on the quality of the charger, but even the cheap ones do a pretty good job these days.
Note that you shouldn't run the chargers in parallel or their current limiting is unlikely to work, which could be disastrous!
A lot of the cheap chargers measure the current returning in the 0V, connecting their 0V outputs together gives alternative paths so that it doesn't have to return through the correct charger! 6A isn't very much at 3.7V, even less with LiFePo4 batteries, you would need several.

In terms of number of charge cycles yes lithium will last longer but if I went with lithium it would likely end up doing a full charge-discharge cycle almost every day. With AGM and voltage cutoff at 12.2 I'm not fully discharging the battery (12.2V corresponds to about 40% charge remaining) so I would expect 5-6 years of usage. Should I be expecting significantly less? I've done a fair amount of research but this is my first hands-on experience with AGM technology. If its more like 3-4 years I can accept that. If it only last 2 years or less I may have to choose another solution when it dies.
With a sensible system, you would not charge a Lipo to 100%, stopping at 90 will double lifespan.
5-6 years charging AGM every day and running the camera 24/7 is certainly possible, but maybe a little optimistic. Does depend a lot on the battery construction though, there is a lot of variation in AGM batteries.

ZR 160 mk1, the original battery was a 075, the AGM I bought is 027 (15mm taller but otherwise the same). There is some space in front of the battery, I could have made a 096 fit (30mm longer than 027 and 15Ah more capacity) which I think is what the diesels take. However I use that space for my air-horns and don't really to want to mess about finding another space for them, no other spaces in the engine bay, would have to remove bumper and mount somewhere, maybe in the future. Besides if I decide I need a bigger battery I might move the battery and engine-bay fuses to the boot and then I can have the battery as big as I like, size 334 or a full on caravan battery, weight would be the limiting factor then.
Sounds like you have that worked out :)

Not keen on the boot idea, you need a lot of copper to carry the 80 or so amps that your alternator is capable of supplying to your empty battery without your cables getting very hot.

I do a 150 mile trip (2.5-3 hours, London to Yorkshire) and back the next day every 2 or 3 months. That should keep me covered right?
I'd still give it an overnight charge every few months, the last bit goes in very slowly, but it is the last bit that does all the good, so really a 12 hour charge is desirable if you are starting off from a half empty battery, or a 24 hour charge at the weekend if like me you use a 6W charger!

The old battery would start the car happily from 11.8V after voltage cutoff kicked in. However one day I noticed something funny with the electric windows, stupidly I ran the window up and down a few times before starting the engine. Since the battery was already down to 11.8V, after running the window a few times the engine wouldn't start and I was late for work haha. Don't want to risk it right now but might do some testing with lower cutoffs when I have some time off work. Besides all the stuff I've been reading about AGM says their capacity is down to 25% at 12.0V and 0% and 11.8V so how the hell is it cranking your engine with only 11.3V? These AGMs are crazy.... Which MG do you have?

Your comments are much appreciated thanks Nigel.
A nearly empty AGM battery will supply far more current than a nearly empty conventional battery, running the windows up and down a few times is likely to warm it up a bit and get even more power!

Totally empty for an AGM tends to be around 11.0V, 12.0 being about half full, most would prefer not to go below 11.8V. Also remember that a lot of these figures are given for unconnected batteries, as soon as you put a load on them the voltage drops even though they are just as full, your alarm system probably provides sufficient load to drop the voltage by 0.2V.

Mine is a ZS, has a little more space for batteries, but then you can't change the headlight bulb without taking the battery out!
 
Thank you. From what I read LiPo and LiFePO4 are lower risk when it comes to higher temperatures and brief periods of fast-charging compared to Li-ion but there's not much in it between LiPo ad LiFePO4. Maybe I misread that stuff or need to do more research? I'm not an RC-hobbyist, just a general electronics tinkerer :)
Thanks for the links.


LiPo will take the crown in with having the fastest discharge rate. This is Definitely not needed in our dash cam setups. Having such a high discharge rate is also what causes them to be more dangerous. They even have LiPo charge bags as they aren't forgiving to failure compared to the other technologies. LiPo cells are used in absolutely no automobile applications as far as I know.

LiIon can also have pretty high discharge but usually comes at a cost of capacity. The LiCoO2 cell if I recall have the highest energy density of all lithium technologies. You'll get almost nearly double the capacity in the same space compared to LiFePO4 batteries. Many hybrid and mostly all electric vehicle use that technology but have a dedicated water cooling system for them.

LiFePO4 has the least energy density but is also the safest. It is much more resistant to abuse such as vibration, over charging, over discharging and even puncture. It doesn't charge or discharge as fast as the other lithium tech but we will be hardly pushing them to their maximum with our setups. They can output quite a bit when many are ran in parallel to make up for their slow charging. Their safety rating and their ability to match automobile's voltage rating in a 4s config is why they are the only batteries used in some Marine Deep cycle, solar setups and RV batteries. I will stick with LiFePO4 in the case of a BMS or charging failure.
 
I've posted elsewhere showing where LiIon cells are certainly able to withstand much higher temperatures than is commonly thought for safety purposes, but high temps are very hard on the cells and should be avoided. Were I doing a project like this I would choose my battery type first based on what I want to achieve, then design or buy a safe and correct charging system for it. As we all know, almost every Li disaster occurs during charging or via a short-circuit, so that is where to put the main focus- the rest likely won't be any problem with a little common sense put into the design.

Beyond the one-in-a-million defective cell escaping a factory's QC testing, I feel absolutely safe with LiIon batteries being stored and used in my vehicle. My only worries occur during charging and those concerns are are small as I use only known good chargers.

Phil
 
Beyond the one-in-a-million defective cell escaping a factory's QC testing, I feel absolutely safe with LiIon batteries being stored and used in my vehicle. My only worries occur during charging and those concerns are are small as I use only known good chargers.

Phil
I was asking around. The only good DC - DC chargers I can find are hobby chargers which require navigating a bit before it charges, and the automatic LiFePO4 chargers are very low power or extremely expensive where the BlackView B124 were the only option. Which good chargers have you found for your LiIon batteries?
 
Yeah my chargers for the batteries for my RC "toys" handle LiFePO4 just fine too, actually have a couple of those batteries for transmitters.
The question is if the charger boot in the last mode it was in, but i do think thats the case with my charger.
Mine however only do 6A charge and only support up to 6 cells batteries on the balance plug.
 
@EsQueue
My LiIon chargers and experience are with individual cells although I've kept somewhat informed on multi-cell matters which I do understand. So I doubt that I can give you anything more which would be useful for this project as I doubt you're interested in pulling and charging cells individually.

I will say that I'm wary of fast charging rates for any Li battery technology as it is harder on the cells/battery and it's pushing closer to the edge of safety issues. I do not want to be dealing with a catastrophic Li failure regardless of whatever other advantage might be gained- I'm very careful with these ;)

Phil
 
@EsQueue
My LiIon chargers and experience are with individual cells although I've kept somewhat informed on multi-cell matters which I do understand. So I doubt that I can give you anything more which would be useful for this project as I doubt you're interested in pulling and charging cells individually.

I will say that I'm wary of fast charging rates for any Li battery technology as it is harder on the cells/battery and it's pushing closer to the edge of safety issues. I do not want to be dealing with a catastrophic Li failure regardless of whatever other advantage might be gained- I'm very careful with these ;)

Phil
Fast charging rates is relative to the battery and it's quality. One battery will be totally fine while a other will heat up. Charging a battery at .5C should do no harm and should pose no safety concern unless they fall into that on-in-a-million cell you mentioned earlier. I have experience with IiIon cells to as I built a 13s10p battery for my ebike a few years ago as well as a diy spot welder as it is the safer route to connecting them. I haven't had any failures so I can't base that on experience. I can only go off of what I read and research about, and observe from what I see used in real life. From that research, I've come to the conclusion that LiPo is a no-no for automotive purposes, despite it's superior discharge rate. LiCoO2 and similar chemistry are used in the automotive industry. They are a great choice due to it's light high energy density but it's charge and discharge rates is driven hard thus the need for active cooling; typically liquid. Tesla also fuses each individual cell and I doubt that the average person that uses these cells are willing to go through all of that. Our dash cams are extremely low energy drain so LiFePO4 is more than well equiped for the task. It has excellent safety and is typically rated for around 2000 cycles while the others are much less. The size disadvantage usually don't mean much in a car if it isn't what's driving the vehicle. I've checked out many tests of LiFePO4 cells, some are punctured with metal remaining inside, while many are purposefully shorted. The results were good.

Yes, LiIon can be safe but I prefer safer. I also require fully automated and a fast enough charge rate to where it is under 5C and I think I've found it. Unfortunately it is not as cheap as I wanted but it is a cheaper option than the EGEN back up batteries for any DIYer that wan't.

I am happy with my current setup of a BlackVue B124 with a 9A charge rate at 14.6v. This is spread to the 18650 4s4p 6 Ah rating config that's included in the box and my DIY 32700 4s2p 11,852 mAh batteries. A 18A charge rate will fall well under specs and charge my system from empty to full in under an hour as opposed to nearly 2.
 
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FYI.... from my research ALL usb power banks that have PASS THROUGH do not CHARGE and POWER something at the SAME TIME....
Can anyone please tell me if they found one that does ?
 
FYI.... from my research ALL usb power banks that have PASS THROUGH do not CHARGE and POWER something at the SAME TIME....
Can anyone please tell me if they found one that does ?

By definition any power bank that has true "pass-through-charging" will power a device at the same time it is charging. Very few on the market have this feature.

Check out Zendure. They are not cheap, however many of their products do indeed have it. (requires a QC3.0 charger) ONLY power banks that actually state definitively that they have the feature, have the feature. (and then sometimes even some that do, don't!)

https://www.zendure.com/collections/a-series-portable-chargers/products/a8-qc-portable-charger-black
 
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Can't pass-through easily be remedied with two relays and a diode? If the diode doesn't work maybe 3 relays. I'll try to draw something up. Sorry, it will look like crap.

Here it is. You can add 12 to 5v converters if necessary and they can also run another relay instead of the diode. Just a crude drawing off the top of my head.

EDIT: the drawing is wrong. The wire running directly to the diode and then to the camera would need to be ran to the NO connector of the bottom relay so it only provides direct power to the camera only when the acc has power. I've just updated the drawing.
20190920_184249.jpg
 
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Using a relay system will work, as almost all relays switch fast enough for the cam not to 'think' the power has been switched on or off. A filter cap might help with switching spikes but I've never had any issue with that running my cams through a SPST switch on the 12V side.

Phil
 
This is my solution to powering my dash cam while the car is off. Automatically switches power from car to power bank when car is turned off
 

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