Capacitor quality information

[pepporony]

So I have been using Viofo A119 for sometime (over a year?) now. Recently just noticed that the cam turned itself right off after I turned the ignition off. I open the camera up and the capacitor was bulged.

I parked outdoor every working day under the sun and it's quite hot here so there's that.

Now I'm wondering, do we have any site/information on the quality of capacitor used in dashcam?

Like, I know that there are capacitor tier list but I don't know if there is a site that says which brand of capacitor is using in this specific cam. Or do we have to trust the operating temp, stated by the manufacturer?

 

[Nigel]

Super capacitors are all pretty similar in temperature and lifetime performance since they all work the same way. If they are failing then it is likely they either got too hot or got supplied with too much voltage, they can survive temperatures a few degrees higher than lipo batteries and survive them for longer but they are still very close to their limit in a hot parked car in summer, especially if the camera is powered.

The only easy way for the camera manufacturers to improve the temperature performance is to fit 3 supercaps insetad of 2, maybe they should for models sold in Thailand and Oz?

 

[Edgardo]

The only easy way for the camera manufacturers to improve the temperature performance is to fit 3 supercaps insetad of 2, maybe they should for models sold in Thailand and Oz?

Or, start using Lithium Iron Phosphate "LiFePo4" batteries. They are claimed to be much more heat tolerant and good for a couple of thousand charge-discharge cycles. I have some solar yard lights that use LiFePo4 batteries. Very constant voltage during discharge too.

 

[SawMaster]

Discrete eectronic components are normally 'graded' by how close they will be to the nominal stated value in use. This is expressed as a percentage where non-critical parts may have a 15% tolerance while critical applications may call for a 5% tolerance. Generally the lowest-tolerance components are the best quality ones, but that does not mean that they will outperform higher tolerance components in any other way. If not stressed beyond their design specs the part might last longer due to the better materials used and tighter QC and testing in manufacture

Another consideration is that when used in series (like is done here) it becomes more important that both components behave exactly the same. The lower-tolerance components are more likely to do that, as are components sourced from the same manufacturing batch. Some components which are normally 'paired' may be offered in matched sets, and in paired usage are always replaced together even if only one is bad. You need to replace both here for that reason, but you might not be able to find matched sets What likely happened here is that one of your caps had less internal resistance so it got overworked compared to the other, then failed earlier.

If your preferred component source does not list matched sets, you can contact them to see if they can get them for you. They can usually identify manufacturing batches and send you parts matched that way for little or no extra cost which is usually good enough. This is the approach I'd take if I wanted the best possible match But given how cheap these are and how easy the install job is, I personally wouldn't invest much time or money seeking perfection since the odds are that your next pair will probably be better than what you have. Hope this helps!

Phil

 

[pepporony]

I guess I have to change my behavior instead of looking for a more expensive camera hoping for a better caps..

Just curious, will a wedge shaped cam like A119 that mounted very close to to windshield hotter than things like Viofo WR1 that hanging around?

 

[Nigel]

If your preferred component source does not list matched sets, you can contact them to see if they can get them for you. They can usually identify manufacturing batches and send you parts matched that way for little or no extra cost which is usually good enough. This is the approach I'd take if I wanted the best possible match But given how cheap these are and how easy the install job is, I personally wouldn't invest much time or money seeking perfection since the odds are that your next pair will probably be better than what you have. Hope this helps!

Phil

That is a good reason for using 3 instead of 2, assuming there is enough space to fit them. Having 3 means that they don't need to be so closely matched and also they will all be operating at lower voltage so will be able to withstand more heat.

 

[Nigel]

I guess I have to change my behavior instead of looking for a more expensive camera hoping for a better caps..

Just curious, will a wedge shaped cam like A119 that mounted very close to to windshield hotter than things like Viofo WR1 that hanging around?

The WR1 is quite a good shape since it has far more surface area not exposed to the sun than exposed to the sun, as well as having all round air cooling.

If you have someone that can use a soldering iron, those capacitors should be fairly easy to replace to get the camera back to normal.

 

[SawMaster]

That is a good reason for using 3 instead of 2, assuming there is enough space to fit them. Having 3 means that they don't need to be so closely matched and also they will all be operating at lower voltage so will be able to withstand more heat.

That's not as easy to do as it seems. First, with 3 you'll go over-voltage for the cam's needs unless you design in a voltage regulator. Second, while it's not too tough balancing 2 caps via matching components, using 3 or more in series is almost guaranteed failure without a charge balancing circuit because the charging imbalance becomes exponential. You double the stress on the weakest cap with 3, quadruple it with 4, and so on. The weak cap will fail very quickly like this, where the difference isn't nearly as much with only 2. Arranging 4 in 2S2P configuration still doesn't help as you've now got two imbalances. Supercaps run at ~2.7V each, so running 2 of them in series gives you the workable voltage you need with the least chance for imbalance; that is why the factories do it this way

Heat is the enemy of dashcams (and almost all other electronics), and while most 'wedge cam' installs hide most of the cam behind a darkened 'frit' or panel, it still gets hotter next to the windshield than it does away from it even where there is no direct sun on the cam However what matters more is that the cam be able to tolerate the heat of the environment it is in, which cap-equipped wedge cams seem to be able to do even in the hotter climates. So while less heat is better, it may not really be an issue as long as the cam functions properly and does not see a significantly shorter life wherever it is mounted Probably more important is the cams ability to shed self-generated heat which a larger cam might be able to do better.

While heat may have played a part in this cap failure, IMHO most of it was likely a 'dud' cap of the two in which case lowering the heat level would have not significantly increased the cap's lifespan. Remember we're dealing with consumer-grade stuff which is all made to a price and is not intended to last forever. To get much longer service life would likely double the cost of a cam and you'd still have the odd failure now and then. It's not something I'd worry too much about, just avoid direct sunlight and you should be OK

Phil

 

[Nigel]

That's not as easy to do as it seems. First, with 3 you'll go over-voltage for the cam's needs unless you design in a voltage regulator. Second, while it's not too tough balancing 2 caps via matching components, using 3 or more in series is almost guaranteed failure without a charge balancing circuit because the charging imbalance becomes exponential. You double the stress on the weakest cap with 3, quadruple it with 4, and so on. The weak cap will fail very quickly like this, where the difference isn't nearly as much with only 2. Arranging 4 in 2S2P configuration still doesn't help as you've now got two imbalances. Supercaps run at ~2.7V each, so running 2 of them in series gives you the workable voltage you need with the least chance for imbalance; that is why the factories do it this way

Heat is the enemy of dashcams (and almost all other electronics), and while most 'wedge cam' installs hide most of the cam behind a darkened 'frit' or panel, it still gets hotter next to the windshield than it does away from it even where there is no direct sun on the cam However what matters more is that the cam be able to tolerate the heat of the environment it is in, which cap-equipped wedge cams seem to be able to do even in the hotter climates. So while less heat is better, it may not really be an issue as long as the cam functions properly and does not see a significantly shorter life wherever it is mounted Probably more important is the cams ability to shed self-generated heat which a larger cam might be able to do better.

While heat may have played a part in this cap failure, IMHO most of it was likely a 'dud' cap of the two in which case lowering the heat level would have not significantly increased the cap's lifespan. Remember we're dealing with consumer-grade stuff which is all made to a price and is not intended to last forever. To get much longer service life would likely double the cost of a cam and you'd still have the odd failure now and then. It's not something I'd worry too much about, just avoid direct sunlight and you should be OK

Phil

That's not correct, they are probably being charged to whatever voltage the USB cable provides, probably 5.2v, maybe a bit more depending on the charger.
5.2v / 2 = 2.6v - if they are 2.7v super capacitors then that is uncomfortably close to the limit and will mean their max temperature limit is low
5.2v / 3 = 1.74v - well below their limit and resulting in a higher max temperature limit
Yes there is more risk of them not being well matched with 3, but it doesn't matter since you are using them nowhere near their voltage limit, they will be happy even if not balanced.

 

[kamkar]

I just read that adding nano diamonds to lipos will make them foolproof.
https://www.sciencedaily.com/releases/2017/08/170825091240.htm

 

[Module 79L]

So I have been using Viofo A119 for sometime (over a year?) now. Recently just noticed that the cam turned itself right off after I turned the ignition off. I open the camera up and the capacitor was bulged.

I parked outdoor every working day under the sun and it's quite hot here so there's that.

If the camera is not running while the car is parked then the capacitor's swelling has nothing to do with the temperature reached inside the car or the windshield's temperature, even if you leave the car facing the sun. This type of capacitors usually bulge due to manufacturing defects or loss of characteristics (becoming dry is the most common cause for bulging) but only when they're being powered, not when they're "resting".

 

[Nigel]

If the camera is not running while the car is parked then the capacitor's swelling has nothing to do with the temperature reached inside the car or the windshield's temperature, even if you leave the car facing the sun. This type of capacitors usually bulge due to manufacturing defects or loss of characteristics (becoming dry is the most common cause for bulging) but only when they're being powered, not when they're "resting".

When you turn the camera off, the capacitors don't turn off, they supply some power for shutting the camera down but most of the power remains in the capacitor and their voltage stays near maximum, they can still be damaged by heat.

 

[Dashmellow]

High quality super-capacitors such as those offered by Maxwell are rated to operate at temperatures up to 85º C (185º F). Even in a hot car on a sunny day they are unlikely to see such extremes.

 

[Module 79L]

When you turn the camera off, the capacitors don't turn off, they supply some power for shutting the camera down but most of the power remains in the capacitor and their voltage stays near maximum, they can still be damaged by heat.

I didn't say they turn off when you cut the power. Where did you get that idea from? What I said was that when they start to dry out they tend to swell but only when being powered. A defective or handicapped capacitor doesn't swell just for being in a hot environment.
Being swollen doesn't mean they're done, it means they lost some of the ability to accumulate as much charge as before (hence the quicker shut down) but they should be replaced anyway, for obvious reasons.