Lifepo4 Battery pack installation

[claudiohi]

Hi guys, I am planning to install a sealed Lifepo4 12Vx9AH (Aliant brand) in my car, but the car may be parked in such hot area (under sun light).
So my question is: how safe is it to install this battery inside the car´s trunk?

Thanks!

 

[SawMaster]

Most of these types of batteries are safe to store, charge, and use at 38C (100F) as long as you're not at maximum current. A car trunk can easily exceed that in direct summer sun and a car interior won't be much better. You would need to check out the battery manufacturer's specs to be sure what this one can do, but I think you'll be OK.

For better safety an AGM battery would be my choice, and in smaller sizes like this they're cheap enough to purchase. The discharge voltage levels need to be considered; a LiFePO4 can tolerate a deeper discharge for a given size compared to AGM. A 15A AGM would probably give you around 24 hours recording time for a single cam without excessively discharging it.

You also need to be considering the camera, which will be reaching the limits of it's survival at these temperatures, and will be exceeding manufacturer's recommendations which will void it's warranty. You'll positively want to avoid any that use a LiPo instead of supercaps. Probably the best cam for heat tolerance is the old Mobius, but it's not much good with night-time footage compared to newer cams. Street Guardian cams also do well in higher heats.

Phil

 

[Nigel]

So my question is: how safe is it to install this battery inside the car´s trunk?

How are you are going to charge it?

 

[SawMaster]

How are you are going to charge it?

Maybe THIS ?

Phil

 

[Nigel]

Maybe THIS ?

Phil

That looks fine for an AGM battery, as long as your cables and relay are thick enough.

Not so sure for a lithium battery, although it depends on what battery management system is inside the battery, if any.

 

[Philzter888]

I’ve looked at the safety issues of lifepo4 recently and a lit review suggests operating temperatures below 40C is preferred. There is some chance of damage between 40-60C, with increasing likelihood or rapid rise in temperatures if say charging above 40C. However “critical” or thermal runaway type scenario requires very high temps like 100-150C+ unless there’s a pre-existing defect like too much iron causing a short. I am using an elitech gsp-6 and it logs temps. I’m logging max 31C in cool weather and outside temps max 25C. I’m guessing in summer the only way to keep under 40C is with ventilation - like under the seat with cracked windows at the very least.

 

[SawMaster]

Yes, the heat found in cars exceeds the "recommended" range of many electronic components, so lifespans will be shorter than ideal, but it works well enough so we go with it. And I take the same approach toward batteries.. Good quality Li cells and batteries are relatively safe to use in car heats as long as you keep them out of direct sunlight but you do have other choices which are safer- they will just be more "DIY" and less "plug-and-play". The skills needed are basic and most people can do it. Just don't go swapping battery types in this kind of sytem- it is only safe and workable with 12V AGM, SLA, and LA type batteries. It can use Li types if they have (or you add) a proper charging system for them which is another subject altogether.

Phil

 

[Philzter888]

I feel queasy with that approach. Most properly engineered 4x4 solutions put an extra battery under the hood. I have an Eaton UPS 9130 with 2000VA and it’s just a pass through double conversion and it’s engineered with a huge noisy fan that constantly runs even when batteries aren’t used. Must be a good reason for that. I’m conditioned to over-engineering everything with airflow and fans. So I get nervous when there’s no active ventilation or cooling. Guess the type-I error I want to avoid is the dash cam getting shorted out at the critical moment when an investment banker trying to claim on his life insurance throws himself under my car.

 

[SawMaster]

Lots of cars have the battery in the trunk (boot). RV motorhomes and trailers (caravans) have their batteries in comopartments which are usually at least somewhat sealed up. Near the car engine batteries receive lots of radiant heating. Just some common sense and it's not a problem with AGM/SLA but could be with a Li type battery. In the UPS mentioned above, the cooling fan is needed for the charger circuitry which is totally absent here with the AGM/SLA not needing any conversion from one power form to another, or needing charge regulation which they do internally as part of their nature. So no problem that I can see

Phil

 

[Philzter888]

I agree lot so cars have battery in the trunk, but they are manufacturer engineered with a venting tube or sealed off. A lot of race cars do this as well, but its also recommend to insert venting tubes. Putting holes in your car for venting tubes is risky business - Ive spent ages trying to figure out an easier way to put solar cables and antenna wires into the cabin without drilling in the asbence of pre-existing grommets. I personally would never buy a car where a lead battery is located under the driver seat. Funny you mentioned RV with batteries because I recall watching a video on youtube a few weeks ago about some guy who had overheating problems despite cool ambient temps throughout the RV, and he ended up building in ventilation fans to circulate air in the battery cabinet. RVs have much more air volume than a normal car. I tried to buy a 4-gas detector recently since we transport natural gas sometimes, and it was really difficult to buy a new one. I ended buying an old detector from Peel Electronics, it was the 04-OG-12V which could detect natural gas and battery emissions - companies don't really produce these anymore. Like I said, I call it "over engineering", its unlikely that you will get a bad outcome. But if one does happen, and its cheap to mitigate why not pay for the over engineering? If the fan is really just for the electronic circuit boards, then don't the lithium battery controllers rely on IC as well? Sorry just playing devils advocate.

 

[SawMaster]

Li batteries are a whole different game and I am not discussing them here. SLA/AGM batteries do have vents, but these are normally closed and any gasses recombine and go back into the battery as electrolyte. The only time they vent fumes is when they're hot and working hard, and those are minimal. Old-fashioned lead-acid needs venting and uses it frequently.

I can't offer you any more than that. If you think you can do better then by all means do so.

Phil

 

[Philzter888]

Like I said this is all low risk stuff. Manufacturers still vent AGM to outside the vehicle despite the fact they are labelled “sealed”. Again probably over engineering. Take for example the Porsche Cayenne 2006 that killed mother and daughter in Florida for using incorrect battery instead of the proper AGM that vented outside the car. That’s just 2 deaths so low odds. And if the battery was in the trunk probably wouldn’t have been as bad. At least you know right?

 

[Indian]

My LiFePo4 battery has a BMS that stops charging at temperatures over 50 degrees celsius and ther Dc charger prevents charging under 0 degrees.
The OP does not say much about his battery. Has it got a BMS? The BMS will cut out charging at 50 degrees.
I dont think heat will be his main problem but rather the correct charging cycle. A Dc charger might be needed. If the alternator is made for the AGM battery, the charging cycle is similar for the LiFePo4 batteries, so the Dc charger is not needed.
I run my fridge and camera with occasional use of the Eberspächer air heater and I dont worry about running flat. The battery has never dropped below 77% and an hours drive puts in 100% again.

 

[Tomcat]

I have the B124+b124E and a 100AH lifepo connected the 9A charging during driving is slow but i can always charge at home if i want to and i have it connected with a fuse to prevent problems between batteries. It can run 4ch of BVs for 24/7 without problems.
also the 100AH battery i have has low temperature protection. It stops charging below 0 too cells die if you dont. the 100ah model i use has the same BMS and build quality as the overpriced liontron. Overall i would say a 100ah lifepo4 was the best price/capacity deal for me.
the Vitronic DC charger you have is great as you charge alot quicker then i do.

 

[kamkar]

TBH a ready to run lipo like that i would assume it have some form of BMS build in, if not the charger should have that, and i assume this also go for temperature and not just balancing like a lipo charger for flashlight or RC batteries ( though a few do have a temp probe )
But a large battery meant for off grid power storage i would assume have something extra as they can be in more exposed environments.
And i have seen of gritters power grid and often it are in a place that offer 0 insulation in winter

That said i have driven my RC car a winter where after a short joint break in the car, the RC cars transmission was frozen solid and we had to thaw up both cars over candles in the car.
But then again our little scale 4 x 4 cars are not super power hungry when driven normal, but you can get in a bind where you can use huge amounts of power to get out or snap a 5 mm hardened steel axle.

My friend laughed at me cuz my car was beefed up with all steel and ALU housing gearbox, but his plastic gearbox also needed heat to get going again.

If you are just charging a 100 Ah battery with 9 A, then you are charging it very conservative i would say

 

[Indian]

I have the B124+b124E and a 100AH lifepo connected the 9A charging during driving is slow but i can always charge at home if i want to and i have it connected with a fuse to prevent problems between batteries. It can run 4ch of BVs for 24/7 without problems.
also the 100AH battery i have has low temperature protection. It stops charging below 0 too cells die if you dont. the 100ah model i use has the same BMS and build quality as the overpriced liontron. Overall i would say a 100ah lifepo4 was the best price/capacity deal for me.
the Vitronic DC charger you have is great as you charge alot quicker then i do.

Yesterday I started the car when the temperature was -16 °C and the battery temperature was at -12 degrees. I drove 40 km and the battery was at +5 degrees and charging. I started at 61% battery charge and after 100 km from start, my battery was at 100%. Car had been parked for 4 weeks in sub zero temperatures.

 

[AnodizedBear]

If you are just charging a 100 Ah battery with 9 A, then you are charging it very conservative i would say

I have the B124+b124E and a 100AH lifepo connected the 9A charging during driving is slow but i can always charge at home if i want to and i have it connected with a fuse to prevent problems between batteries. It can run 4ch of BVs for 24/7 without problems.
also the 100AH battery i have has low temperature protection. It stops charging below 0 too cells die if you dont. the 100ah model i use has the same BMS and build quality as the overpriced liontron. Overall i would say a 100ah lifepo4 was the best price/capacity deal for me.
the Vitronic DC charger you have is great as you charge alot quicker then i do.

I was also looking at purchasing a 100ah LiFePo4 battery to use as a battery pack for my new Viofo A139. I have an alternator rated for 100amps too, but I imagine that some of that will be used to charge my car battery and operate the car's electronics. I don't think it will be quite as simple as just running a 100amp circuit and charging it in an hour. I was wondering how you did it? I probably only drive the car about 4 hours a week, though. So, I figure if 7.5aH gets 24h, I figure a 100ah battery will give me pretty good coverage!

I'm hoping to use my car as a battery backed camera that can keep an eye on the garage. Suffice it to say that there's a few reasons why I'd like to use my car dashcam for this rather than installing a camera in the garage.

 

[SawMaster]

With LiFePO4 you need a BMS (battery management system) to control charging. Most factory-built LiFePO4 batteries will have this built in, but for vehicle use you want one with over-temp and under-temp protection. Beware that many claim under-temp protection but actually do not have that function. Charging these outside of their specs will destroy them. LiIon is similar. AGM or SLA can simply be 'paralleled' or 'float charged' directly as these self-regulate charging by their nature.

Phil

 

[AnodizedBear]

Great! So, just pick a battery you like, hook it up via a battery management system, and you're good to go? Sounds great!

Here's a battery I found on Amazon. https://www.amazon.com.au/12-8V-100...v+100ah+LifePo4+battery&qid=1618135086&sr=8-7 Looks like it takes a 20amp charge rate. So, I'm guessing it should charge in about 5 hours?

Any idea about budgetting power delivery from the alternator to ensure that one doesn't oversubscribe their electronics system?

 

[SawMaster]

The car will only deliver excess current to the battery, so if the car needs 90A only 10A will go to the battery. But today's alternators are generously sized, so you'll likely have the full 20A available for charging the added battery. The BMS won't be 100% efficient so maybe 5.5 to 6 hours for a full charge from empty. Dashcams use roughly 0.5AH, so with a 100A battery that's 200 hours runtime- over 8 days. You could use a smaller battery and use a charger while parked too.

I'm far from an expert on the subject, but there are plenty of YouTube vids and internet forums on the topic of RV use of LiFePO4 batteries, and you'd do well to learn from those which batteries and BMS's are good as well as how to hook everything up. Not too complicated but you need the right wire gauges and terminals, plus you need fuse or circuit breaker protection too. 100A or even the 20A charging current is some serious power and must be handled correctly for safety reasons.

Phil