Using a AGM Deep Cycle Battery/LiFePo4 battery for dashcam

[Nath]

With lithium you simply have to stop charging when they are full. There is no float charge like lead acid. You have to stop the charging or you will kill it.

Hold a sec so you are saying that if you let the lithium battery connected to CC/CV power source indefinitely it's going to fail? (lets put aside something like a keeping it at 100% is not good for the battery longevity)

Exactly why never buying those ready to go battery packs. Lol a cellink neo is the biggest rip off I've seen in terms of my eyes. All that crap for 350-400AUD. No way! Haha.

It's actually not that bad. Yes, it's a bit overpriced but you'll get a charger, BMS, temperature protection (or rather "control"), bluetooth connection and LiFePO4 (which are not that cheap). Everything in a nice box, ready for the costumer who doesn't need to be tech savvy. Actually despite being able to build such pack myself, I just bought B-124 and added 20Ah LiFePO4 "raw" pack .

 

[Outbacknomad]

An article on lithium batteries worth reading.

DIY LiFePO4 Batteries On Boats - Marine How To

DIY LiFePo4 On Boats Last edit;3/26/23:The base of this article was written a number of years ago (2010) but this does not mean the information here is outdated. We have been keeping it updated and have added to it when ever we had the time. This article deals

marinehowto.com

 

[SawMaster]

A very good info source for LiFePO4 is Will Prowse and his YouTube Channel His website is listed there and he has some books out too. He covers all the aspects and tests products more thoroughly than anyone else I've found, including complete tear-downs. His vids are kind of fast-paced and hard to keep up with at first, but once you begin to understand things you can keep up. He's been doing a lot of 100A LFP tests lately so his more recent vids will be relevant here. Rewind/replay is your friend when watching his vids.

There's a lot to know and learn with LiFePO4 and it's proper management. All parts of it range from junk to good to overpriced with certain parts like under/over temp charge disconnect being critical and important here. As of now it's the best value in battery power but there is a higher entry price than with AGM to do it correctly, and it must be done correctly to receive it's benefits. If you can't meet the entry price or aren't willing to spend considerable time learning about LiFePO4 then I'd recommend you go with AGM which is much much simpler, easier, and far more forgiving of errors.

Phil

 

[joe384]

And just a general question (to anyone), I've read that LiFePo4 is the safest of all, mostly because it is less/not flammable due to the different materials it houses. But I see Toyota RAV4 Prime housing an Li-Ion for their main electric car, Tesla as well. How come those batteries are considered 'safe'? Just out of curiosity, I know they might have some extra and expensive protection and all but it does make sense that Li-Ion are fine too? Assuming they're well designed and protected. I'll still probably go with a Lifepo4 but that Li-Ion just came to mind.

Li-Ion is used by Tesla etc because it has the best energy density. I assume they put extra protection and stuff and have fancy charging circuitry.

 

[SawMaster]

Li-Ion is used by Tesla etc because it has the best energy density. I assume they put extra protection and stuff and have fancy charging circuitry.

Yep. And it's an entirely different purpose and usage. I'm a big LiIon fan for some purposes, but not as a source of external dashcam power. LiFePO4 is safer, has nearly as much energy density, and in recent times has become far more affordable. Leave the LiIon for specialized high-current draw situations like powering cars and power tools, and go LiFePO4 or AGM for dashcams- it's better for this use.

Phil

 

[Nigel]

Hold a sec so you are saying that if you let the lithium battery connected to CC/CV power source indefinitely it's going to fail? (lets put aside something like a keeping it at 100% is not good for the battery longevity)

Turn the voltage down so that it only charges to 80% and you can leave it charging permanently, perfectly safe with long life and what solar powered battery banks tend to do.

 

[SawMaster]

Turn the voltage down so that it only charges to 80% and you can leave it charging permanently, perfectly safe with long life and what solar powered battery banks tend to do.

You have to be careful charging this way, as most BMS's or MPPT's will 'see' an added load as a depleted charge, and try to charge it. Victron and a few others have systems made to be programmed and used this way, but most of the cheaper ones aren't meant for this. Li battery use requires that you know a lot more about what you're doing than other battery technologies do, and with the costs involved the last thing you want to do is ruin a perfectly good battery.

Another downside of this is that a system which 'top balances' (which almost all do) can't do that with less than full charging, so you'll have to periodically manually cycle the system without a load. If you want to 'float' a load, better to use AGM which can do this inherently.

Phil

 

[Nigel]

You have to be careful charging this way, as most BMS's or MPPT's will 'see' an added load as a depleted charge, and try to charge it. Victron and a few others have systems made to be programmed and used this way, but most of the cheaper ones aren't meant for this. Li battery use requires that you know a lot more about what you're doing than other battery technologies do, and with the costs involved the last thing you want to do is ruin a perfectly good battery.

Another downside of this is that a system which 'top balances' (which almost all do) can't do that with less than full charging, so you'll have to periodically manually cycle the system without a load. If you want to 'float' a load, better to use AGM which can do this inherently.

Phil

You always need to be careful charging lithium if you don't use a standard charger, and in fact lead acid, they can both be dangerous.

"will 'see' an added load as a depleted charge, and try to charge it."
It can safely be done, but yes you need to know what your charger is doing. It does not matter if they try to charge while there is an output load, as long as they don't exceed the maximum voltage on any of the cells, and don't exceed the maximum current. Measuring the current could be a problem if your meter is measuring the input current to the battery + load instead of the input current only to the battery cells, but as long as it doesn't supply more than the maximum charge current then it can only undercharge the battery, or if it is a heavy load then it may only reduce the discharge, neither of which are a problem.

With other battery technologies like NiMH where you detect end of charge by sudden increases in voltage, you can't drive a load while charging otherwise you can't know when it is full, but with lithium the battery is full simply when you reach maximum voltage, and even then it could take a bit more if you don't mind sacrificing some life, it is not actually full, just as full as you have decided to fill it.

"Another downside of this is that a system which 'top balances' "
Not all battery packs need to 'top balance', in fact a dashcam battery pack may only ever reach full on long journeys, and on a commuter car that may never happen, so such a battery pack could be dangerous for dashcam use (That is how CellLink is done?).

For powering dashcams, the safest battery pack would have all the cells in parallel and step up the output voltage to that required by the dashcam, in which case no balancing is needed and it doesn't matter if cells wear at different rates, you can also discharge while charging perfectly safely. Yes, there is a slight inefficiency in the voltage change, but on a CellLink battery pack you need to use a hardwire kit to step down the voltage, with roughly the same inefficiency as a modern step up regulator.

 

[SawMaster]

LiFePO4 batteries comprise of cells inside which are wired in series/parallel banks- this is how a nominal 12VDC (or whatever) is reached at the terminals. Li cells all run at 3.2V to 4.2V roughly, so series connection has to be there, and anytime Li cells are used in series they must be balanced or a cell or bank of cells can go out-of-spec and over or under charge compared to the rest ruining the battery for further use. The BMS inside the battery case accomplishes this, and this is why I've become a fan of Will Prowse as he cuts open the batteries he tests to see what's going on inside. You'd be surprised to learn that some renowned names use a crappy BMS while some cheaper brands use good ones, and that almost none of these batteries actually have an under-temp probe for charging protection although most batteries claim to have that function

Powerbanks like the Cellink don't 'balance' in charging; rather they are (supposedly) made with matched cells which in theory will charge and age similarly. It works well enough in practice for such relatively cheap devices, but when you're looking at spending ~$400+ for just a battery which ought to last you at least 10-20 years, that isn't good enough by itself- you simply must balance the cells or banks of cells to make things last. This is how laptop batteries are done, and is the difference between a charging circuit and a BMS which does a lot more than simply regulate charging current and voltage. And this is what makes the battery's internal BMS so important. The BMS uses the output at the battery terminals as a baseline to compare cells/banks when balancing them, and almost all of these are designed to balance under a no-load condition. With an added load it charges to a higher level which can exceed what the cells want, thus shortening their usable life. All this happens inside the battery itself, and only those batteries which have a data terminal can have this altered externally, usually by connecting to an MPPT controller with a data input port.

Those who limit charging to 80% and DOD to 20% do so as a means to extend battery life, and it does do that to a varying degree mostly dependent on cell quality. But when you factor in the need for more batteries to give an equal amount of usable capacity the advantage becomes questionable and of lesser impact. And it only really matters much monetarily when you're speaking of having many batteries, not just one like is being discussed here. In an off-grid system it's worth considering but I wouldn't be concerned with just one or two batteries as whatever savings might happen will only be found ten or more years into the future and won't even approach the $100 level. I've been casually studying this subject for about a year now and I'm just now reaching a level of understanding where it all is making sense. There's a whole lot more to it than meets the eye and doing just one thing wrong one time can destroy an expensive battery and I'm not talking about huge errors. You need to know a lot to gain all the benefits of a LiFePO4 battery and to prevent those losses. That's why I'm recommending AGM which can do this job equally well with far less fuss and bother, and less risk of loss as it's a far more forgiving technology when things aren't exactly right.

Phil

 

[Nigel]

LiFePO4 batteries comprise of cells inside which are wired in series/parallel banks- this is how a nominal 12VDC (or whatever) is reached at the terminals

While that is true, it is not how I would construct a dashcam battery. Using parallel connection only is far simpler and safer, and at the current required for a dashcam is easily converted into 5 volts.

Agree with the rest, except that limiting the charge/discharge to 80/20% can make a lipo have maybe 3x the lifetime, so is well worth considering, don’t think it is nearly as much for LiFePO4.

 

[SawMaster]

LiPo's aren't on the table here. I'm not sure anyone even makes a LiPo in large amperage sizes and finding an appropriate charge system could be a problem.

If you want, you can buy LiFePO4 cells and make your own battery, but now the engineering is on you and again it's not plug-and-play simple unless you know which parts to use. Even then you'll probably want to make your own cabling which requires larger crimpers than most folks will have and these can get expensive. These cells can't be just placed anywhere, they have to be compressed in mounting or they will swell in use and lose capacity or even die. Plus charging a swelled LiFePO4 can make it vent and if charging continues it can catch fire. This is one of the few safety-related problems with LiFePO4 and is easily avoidable so it is still a very safe battery technology, much more so than LiIon. As far as buying a LiFePO4 pre-built battery, all I've come across start at 12V nominal and go up from there. Unless you're going to learn the details you're better off buying a pre-built battery which will have a warranty and all the engineering done for you. These have come down in price considerably over the last year. Some (many?) of the cheapest ones are bad for different reasons, but good ones can be had quite reasonably now. I wish I could afford 100A worth of LiFePO4 but I'm poorer than most here so it ain't going to happen but I still enjoy learning about it and following the technology

Phil

 

[Outbacknomad]

If you want to build your own & unless you really know what you are doing use Winston Cells. The places that sell them usually sell all the parts.

 

[SawMaster]

Or check out "DIY Solar with Will Prowse" on YouTube. He's done 2 or 3 vids in the last 6 weeks or so on building your own battery. In the vid description there 's a link to his website and the forum on it is chock-full of knowledge, experience, and helpful people. Oh, and if you like something he shows on his vid it will be sold out within a half hour of the vid being posted so when planning a build check parts availability first and be ready to use alternatives if you're in a hurry.

Phil

 

[ChampaRando]

Oh my gosh haha quite a bit to catch up haha.

Anyways I found a Lifepo4 power station off aliexpress. It costs around $260 AUD. Hopefully its of decent quality and not a fake power station (judging from the description, company website and price). Plus it's a korean seller (yes on AliExpress lol), so hoping it's decent quality.
Will use that for now, test it out first and all. Worst case if it fails early due to poor quality, I can just go replace the internal cells myself for around 100 in 2-3 years. At least that way I have the circuitry and other stuff intact.

 

[Outbacknomad]

Hopefully it doesn't have B or C grade cells.

 

[ChampaRando]

Hopefully it doesn't have B or C grade cells.

Hopefully lmao.

 

[ChampaRando]

https://www.amazon.co.uk/gp/B07MC7TV2G
These are a lot more expensive than they used to be though, although they are quite nice in that you can just carry them inside the house to charge up.

It's basically the same as this, but just slightly larger.

I really wanted the PPS240W01 power station by Energizer, but I cannot find it at all anywhere in Australia. I've had good experience with energizer in the past anyways.

 

[SawMaster]

I chanced across an old dead 'power station' for free and replaced the battery. Couldn't find an exact match for the 20A in it so used an 18A AGM instead. It works but it's nowhere like the newer ones. Still contemplating running some cams from it but I really don't need to and that would be troublesome with how I've got the old bus wired up. Eventually I hope to do an auxiliary power system but that might require a lottery win for me

Phil

 

[Nigel]

Because I was just fooled by myself through these mAh numbers, without knowing how they work XD

Yes, the manufacturers try and fool you!

Power is measured in Watts, not Amps, so the best thing to do is compare Wh ratings. If the powerbank specification doesn't give you Wh ratings then you can calculate it using mAh * volts. Then the only problem is that you don't know the volts, but for a normal USB powerbank it is normally the average voltage of the cells during discharge, not of the output voltage, and that is normally 3.7 volts.

Conversion of voltage from cell voltage to output voltage is normally roughly 90% efficient, so you actually lose about 10% of the power, but the dashcam powerbanks that output "12 volts", generally just output cell voltage, so there is no conversion and no inefficiency, but then you need a hardwire kit which will lose the 10% anyway.

 

[ChampaRando]

Yes, the manufacturers try and fool you!

Power is measured in Watts, not Amps, so the best thing to do is compare Wh ratings. If the powerbank specification doesn't give you Wh ratings then you can calculate it using mAh * volts. Then the only problem is that you don't know the volts, but for a normal USB powerbank it is normally the average voltage of the cells during discharge, not of the output, and that is normally 3.7 volts.

Conversion of voltage from cell voltage to output voltage is normally roughly 90% efficient, so you actually lose about 10% of the power, but the dashcam powerbanks that output "12 volts", generally just output cell voltage, so there is no conversion and no inefficiency, but then you need a hardwire kit which will lose the 10% anyway.

Wait gimmie 1 minute I am re-posting. I just learnt something by doing maths myself lol