Replacing a car dash cam lithium battery with a capacitor? - Page 1
Forum section: electronics / general

author: Halcyon
author_rank: Unknown
timestamp: February 20, 2019, 06:44:59 am
content: My dash cam stopped working, I suspect it's due to the internal lithium battery pack (pictured) having failed and puffed up considerably. Rather than replace it, I'd rather repair it as it's quite a nice little camera.Ideally I'd like to put something other than a lithium pack in there as temperatures inside cars in Sydney can easily reach over 65°C in direct sunlight in Summer, which I'm sure is not good for batteries. In place of the normal 3.7v lithium battery, could I use something like a 6.3v, 2200µF, 105°C electrolytic capacitor? It only needs to last long enough for a graceful shutdown (under 30 seconds).In addition, there is a small battery (approx. 6.8mm in diameter) soldered to the board (also pictured). I presume this is to keep time/date however I'm not ovely fussed about this as the camera gets time/date from GPS automatically and actual config is stored on the SD card. In any case, this battery is depleted. There are no voltage markings on it, but would it be safe to assume that it's a 1.5v non-rechargable? Anyone who knows a bit more about batteries might be able to advise?

author: helius
author_rank: Super Contributor
timestamp: February 20, 2019, 07:24:34 am
content: The latter cell is amanganese-silicon rechargeable cell from Seiko Instruments. It may still be recoverable.As to the capacitor question, it's hard to say without knowing what kind of power draw and time is required. In order to keep a stable voltage, a capacitor for reserve power must only use a small fraction of its capacitance (since the voltage-charge relationship is linear). Battery charging circuits, especially for lithium cells, can also be very different from capacitor based circuits and may need to be bypassed if a capacitor is substituted.

author: Daixiwen
author_rank: Frequent Contributor
timestamp: February 20, 2019, 07:36:01 am
content: Depending on how smart the charging circuit is, replacing the battery with a capacitor may or may not work. It's worth a try, I don't think it would damage anything.The capacity is low though. If we assume the charging circuit charges at 4V and that the camera will work down to 3V, a 2200µF capacitor will only hold for 30 seconds if the circuit uses less than 73µA. It seems low, especially if it needs to write into the flash during that period. You'll probably need at least 1000x more. Maybe two supercaps in series, but then you need to be careful with the temperature again.

author: amyk
author_rank: Super Contributor
timestamp: February 20, 2019, 12:26:38 pm
content: Connecting it through a time delay relay to the always-on 12V bus of the car would be a better solution...

author: aargee
author_rank: Frequent Contributor
timestamp: February 21, 2019, 06:10:55 am
content: Except for the interfacing to the always on 12V. Our hot dashboards are real killers for batteries in GPS as well.Incidentally,I really don't understand the love everyone has for dash-cams. Especially when the data can just as easily incriminate the driver, but I guess the driver's never makes a mistake do they?

author: ataradov
author_rank: Super Contributor
timestamp: February 21, 2019, 06:12:56 am
content: Quote from: aargee on February 21, 2019, 06:10:55 amAt least in the US you don't have to provide the video if you think it will incriminate you. And dash cam can save your bacon big time. OR at the very least create an amusing YouTube video.

author: Halcyon
author_rank: Unknown
timestamp: February 21, 2019, 06:37:02 am
content: Quote from: aargee on February 21, 2019, 06:10:55 amMany years ago I used to investigate car crashes. What I learnt is that most at-fault drivers will either outright lie or try to dilute the truth. Aside from physical evidence, it comes down to your word against theirs (particularly when insurance companies are involved). I remember one bloke who tried to tell me that he was never driving at all, it soon turned out that he not only lied but was also intoxicated at the time of the crash.There are a significant number of drivers who don't like to stop after a crash and just keep driving. So unless you're quick to remember a rego plate, trying to track down the driver of the other car is almost impossible. You wear the insurance excess if you can't identify the vehicle/driver at fault, regardless if you contributed to the crash or not.I've had a dash cam for years and two weeks after I bought it, it paid for itself. A crash happened in front of me where the at-fault driver (driving a taxi) fled the scene. The other driver involved was obviously shaken and didn't get any details of the taxi. I supplied the footage to local Police. Following an investigation, the taxi driver copped a number of infringements, not to mention having to pay the other driver's insurance excess and an increase to his own insurance premiums.If you're worried about your dash cam capturing you doing something wrong, the solution is simple: Don't drive like a dick and obey the road rules.

author: wilfred
author_rank: Super Contributor
timestamp: February 21, 2019, 09:58:17 am
content: I thought about a supercap when this happened to my dashcam. But even if the capacitor could hold up long enough to save the last of the video you would keep losing the date time when it eventually ran down. Well mine did which is why I replaced the battery. I used a battery from some old gadget I picked up for a few dollars. A speaker I think it was.I am also curious about the dashcam pictured, do you also get blurry images when it gets hot?

author: Halcyon
author_rank: Unknown
timestamp: February 21, 2019, 11:01:19 am
content: Quote from: wilfred on February 21, 2019, 09:58:17 amThe dash cam I have gets its time/date from GPS. There is no internal clock settings so hopefully this won't be an issue.I've had no issues with blurry or over-exposed/purple/black images when it gets too hot. It seems to hold up quite well. It's a discontinued BlackVue model (I don't have it handy right now so I couldn't tell you the model).