LifePO4 battery system.

[rykiel575]

Hi guys

So due to a hit and run yesterday when my pajero was parked I have decided to investigate further the use of a LiFePO4 battery back system which will be hard wired to feed two dedicated 24/7 dashcams - one in the front, and one in the rear.

Last year I bought 4x 200Ah 3.2V cells which I will wire in series to form a 12.8V 200Ah battery pack.

I am thinking of using half channel slotted uni strut with M10 threaded rod to clamp the 4 cells together. The batteries did come with a BMS which I will install also.

My question is what is the best way to charge the battery pack?

I've thought of a few options.

1. Remove the primary lead acid starter and replace with the 200Ah LiFoPO4 pack. The max discharge on the cells as I understand it is 3C. But even if it was 1C the 200Ah pack should be able to handle it as cranking amps is probably about 100Amps (apparently 250Amps after some research) for a few seconds.. If I go this option I would have to move the battery pack to the cabin and insulate the battery box to protect it from the heat. I would also have to get a Li-ion battery starter for use if my pack were to ever go flat.
If I go this route I am thinking of building a plywood box which would sit longitudinally directly against the 2nd row passenger seats, with the terminals/vents facing up, and long edge against the seat side by side so it'd end up being a longish box that is not very wide. I have heavy duty cable cutters and crimpers from my old jobs and a bit of thick cable to do the job. (Any suggestions for cable size? would 25mm2 solid copper be enough or should I go higher? I have 70mm2 cable which is way overkill but nothing in between those two (id have to go and buy something else)... might have some 35mm2.


2. Leave primary lead acid starter as is, and purchase a mains powered 240v charger, and then take out the LiFePO4 battery box and charge it in-house. From my calculations (200Ah x 12v = 2400W. Assuming draw of 4Ws for both dashcams, that would be 600 hours it would run for, which is 25 days but I don't want to go to 0% depth of discharge so I would probably have to charge is every fortnight).

3. Get a special car charger (DC-DC? BC-DC?) - and use LiFePO4 battery like a secondary lead acid battery - one of the issues i ran into when researching this last year was because of the different chemistry and voltage characteristics between lead acid and lifepo4, you can't parallel the two batteries together (so presumably can't use a voltage sensing relay to shut off)

4. Dedicated solar panel permanently mounted which feeds the LiFePO4 batteries


The purpose of the batteries would be for the dashcam for now but would be for a fridge and so forth down the line. I'd also probably take the battery out when it comes to reselling the pajero so no loss there.

[Dicko1]

The install of these batteries for the use of a dash cam doesn't make sense. I have a dashcam and it runs for weeks without the need to add anything other than the century start battery. They only have minimal draw and most vehicles are driven several times a week. Just use the start battery and install a 40watt solar panel on the roof. Simple solution. Heaps of info online regarding making a battery system up....first decide why you need the system and build it around this need.ie.....portable for use in any vehicle, bolted into one vehicle, used for fridge, also will connect solar..etc.etc.

[rykiel575]

In my previous pajero i had a starter battery used as a secondary as the guy i bought it from wanted to keep the deep cycle for his new car.

It died within a few months with just the one dashcam.

Solar panel might be an idea though.

At the end of the day i still have the batteries sitting around so would like to make use of them.

[old Jack]

I have been running 2x 30Ah LiFePO4 batteries in the cargo area for 7 years, they have an integrated BMS on each cell, charge voltage is from the Challengers conventional NON SMART alternator via a solid state VSR on the input side and a low voltage cutoff set at 11.5vdc, on the fridge side of the circuit. At the time of installation there was a limited selection of 12vdc chargers suitable for lithium batteries so I knew that the alternator would not be able to get the batteries up to full charge when travelling for extended periods especially in hot weather so I accepted the reduced capacity.

The car is driven every week day for 2 periods of about 30 minutes each but every second or 3rd weekend the car is not driven. I do not run the 40 litre Engel all the time but I do find the parasitic draw of the car, VSR and LVCO is enough to drain the batteries down to 11.5vdc over about a month in the cooler weather and 3 weeks in the hot weather. So I give the batteries a fully recharge every month using a 24 hour duration 16vdc 4amp Max trickle charge. I haven't tried isolating the batteries when they are fully charged and removing all parasitic discharges to see what the standby life of the batteries are.

OJ.

[Bru9]

I have been running 2x 30Ah LiFePO4 batteries in the cargo area for 7 years, they have an integrated BMS on each cell, charge voltage is from the Challengers conventional NON SMART alternator via a solid state VSR on the input side and a low voltage cutoff set at 11.5vdc, on the fridge side of the circuit. At the time of installation there was a limited selection of 12vdc chargers suitable for lithium batteries so I knew that the alternator would not be able to get the batteries up to full charge when travelling for extended periods especially in hot weather so I accepted the reduced capacity.

The car is driven every week day for 2 periods of about 30 minutes each but every second or 3rd weekend the car is not driven. I do not run the 40 litre Engel all the time but I do find the parasitic draw of the car, VSR and LVCO is enough to drain the batteries down to 11.5vdc over about a month in the cooler weather and 3 weeks in the hot weather. So I give the batteries a fully recharge every month using a 24 hour duration 16vdc 4amp Max trickle charge. I haven't tried isolating the batteries when they are fully charged and removing all parasitic discharges to see what the standby life of the batteries are.

OJ.

Why don't you get the enerdrive 40A DC-DC? It does everything you could want, even allows to set charge rate in 5A increments, I have one in cargo bay and just with a press of a button I can charge AGM or Lifepo4 option in my portable battery box. also by the looks the 12V dropins are getting better & better, life is too short to waste building lithium batteries, do we build are AGM or Flooded batteries? What would I be saving that warrants all the hassel? All the custom built stuff uses Chinese cells to. Chances are when the battery needs replacing you are gonna have no time in the world to build one. Just buy online & plonk it in.

What is the life expectancy of the 12V dropins I wonder? Researching more about proper charging & care I feel they should get at least 5-6years of good usable capacity. They are getting cheaper from china with there decent lifespan vs the high cost of quality usually USA brand agms . Even good flooded DC batteries are expensive in this country.

Finally at 7yrs old have you done a capacity test?

[Dicko1]

Why don't you get the enerdrive 40A DC-DC? It does everything you could want, even allows to set charge rate in 5A increments, I have one in cargo bay and just with a press of a button I can charge AGM or Lifepo4 option in my portable battery box. also by the looks the 12V dropins are getting better & better, life is too short to waste building lithium batteries, do we build are AGM or Flooded batteries? What would I be saving that warrants all the hassel? All the custom built stuff uses Chinese cells to. Chances are when the battery needs replacing you are gonna have no time in the world to build one. Just buy online & plonk it in.

What is the life expectancy of the 12V dropins I wonder? Researching more about proper charging & care I feel they should get at least 5-6years of good usable capacity. They are getting cheaper from china with there decent lifespan vs the high cost of quality usually USA brand agms . Even good flooded DC batteries are expensive in this country.

Finally at 7yrs old have you done a capacity test?

It is not unusual to also get 7-8 years out of a Fullriver AGM. Like any other quality battery they will last a long time if set up correctly in the first place and maintained for longevity (like Jack does by giving his batteries a monthly full quality charge).

[Bru9]

It is not unusual to also get 7-8 years out of a Fullriver AGM. Like any other quality battery they will last a long time if set up correctly in the first place and maintained for longevity (like Jack does by giving his batteries a monthly full quality charge).

Agree. At 7 years what is the capacity remaining in the Fullriver AGMs?

Very easy to maintain an AGM. my portable battery box sits in shed all year round disconnected from any loads/chargers & I either keep it on float continuously with solar or just top up every 2-3months depending on temps/seasons & leave overnight on float to fully saturate. Every 12months if not used I just cycle it a few times to exercise using a powerful 12V globe as drain plug.
But for a portable battery box lead is simply too heavy & then there is the slow recharge times in small sunhour regions along with the fact lithium can use almost all the capacity in a cycle.

If I was regularly going in the northern parts of this country I would go flooded over AGM, in places with very little clouds & long sunhours like 7+. For basic loads like fridges & stuff I don't see the point in AGM.

[Dicko1]

Agree. At 7 years what is the capacity remaining in the Fullriver AGMs?

Very easy to maintain an AGM. my portable battery box sits in shed all year round disconnected from any loads/chargers & I either keep it on float continuously with solar or just top up every 2-3months depending on temps/seasons & leave overnight on float to fully saturate. Every 12months if not used I just cycle it a few times to exercise using a powerful 12V globe as drain plug.
But for a portable battery box lead is simply too heavy & then there is the slow recharge times in small sunhour regions along with the fact lithium can use almost all the capacity in a cycle.

If I was regularly going in the northern parts of this country I would go flooded over AGM, in places with very little clouds & long sunhours like 7+. For basic loads like fridges & stuff I don't see the point in AGM.

Flooded batteries dont last long up North in rural areas. Corrugations shake the life out of them and heat also takes its toll. That why the vast majority use agm batteries for camping, rv,s and trailers/caravans. Also no spillage .

[Bru9]

Flooded batteries dont last long up North in rural areas. Corrugations shake the life out of them and heat also takes its toll. That why the vast majority use agm batteries for camping, rv,s and trailers/caravans. Also no spillage .

Don't corrugations just about ruin the 4wd anyway? I was more referring to longterm frequent base camping, i have a marine grade 12v century, dunno how they hold up.
While i have no direct experience my self all the stuff i have read in marine and offgrid forums suggest flooded is the best for warm climates as far as temp is concerned.
Enough to convince me that a camper trailer battery setup would be trojan t105 for me. The thing about agm is for living out of the camper for say 6months or 12months you need a genny to get them back to full quite often, far more runtime then with flooded.

[Dicko1]

Bit of info for you Bruce...AGM is used by most caravans, camper trailers and off road vehicles for use as a power supply. Very few use a plain wet cell..




From the web...


2. Basically, there are two types of lead acid batteries (along with three sub categories). The two main types are starting (cranking), and deep cycle (marine/golf cart). The starting battery (SLI starting lights ignition) is designed to deliver quick bursts of energy (such as starting engines) and therefore has a greater plate count. The plates are thinner and have somewhat different material composition.
The deep cycle battery has less instant energy, but greater long-term energy delivery. Deep cycle batteries have thicker plates and can survive a number of discharge cycles. Starting batteries should not be used for deep cycle applications because the thinner plates are more prone to warping and pitting when discharged. The so-called Dual Purpose Battery is a compromise between the two types of batteries, though it is better to be more specific if possible.
3. Wet cell (flooded), gel cell, and absorbed glass mat (AGM) are various versions of the lead acid battery. The wet cell comes in two styles; serviceable and maintenance free. Both are filled with electrolyte and are basically the same. I prefer one that I can add water to and check the specific gravity of the electrolyte with a hydrometer.
The gel cell and the AGM batteries are specialty batteries that typically cost twice as much as a premium wet cell. However, they store very well and do not tend to sulfate or degrade as easily as wet cell. There is little chance of a hydrogen gas explosion or corrosion when using these batteries; they are the safest lead acid batteries you can use. Gel cell and some AGM batteries may require a special charging rate. If you want the best ,most versatile type, consideration should be given to the AGM battery for applications such as Marine, RV, Solar, Audio, Power Sports and Stand-By Power just to name a few.
If you don't use or operate your equipment daily, AGM batteries will hold their charge better than other types. If you must depend on top-notch battery performance, spend the extra money. Gel Cell batteries still are being sold, but AGM batteries are replacing them in most applications.
There is a some common confusion regarding AGM batteries because different manufactures call them by different names. Some of the more common names are "sealed regulated valve," "dry cell," "non-spillable," and "valve-regulated lead acid" batteries. In most cases, AGM batteries will give greater life span and greater cycle life than a wet cell battery.
SPECIAL NOTE: It's common for individuals to use the term "gel cell" as a generic term when referring to sealed, maintenance-free batteries, much like one would use Kleenex when referring to facial tissue. As a result, be careful when specifying a gel cell battery charger, as many times we're told by a customer that they need a charger for a gel cell battery when in fact it isn't a gel cell at all.
AGM: The Absorbed Glass Matt construction allows the electrolyte to be suspended in close proximity with the plates active material. In theory, this enhances both the discharge and recharge efficiency. Common manufacturer applications include high-performance engine starting, power sports, deep cycle, solar and storage battery. The larger AGM batteries we sell are typically good deep cycle batteries and they deliver their best life performance if recharged before allowed to drop below the 50% discharge rate. The Scorpion motorcycle batteries we carry are a nice upgrade from your stock flooded battery, and Odyssey branded batteries are fantastic for holding their static charge over long periods of non use. When deep cycle AGM batteries are discharged to a rate of no less than 60%, the cycle life will be 300 plus cycles.
GEL: The gel cell is similar to the AGM style because the electrolyte is suspended, but it's different because technically the AGM battery is still considered to be a wet cell. The electrolyte in a gel cell has a silica additive that causes it to set up or stiffen. The recharge voltage on this type of cell is lower than the other styles of lead acid battery. This is probably the most sensitive cell in terms of adverse reactions to over-voltage charging. Gel Batteries are best used in VERY DEEP cycle application and may last a bit longer in hot weather applications. If the incorrect battery charger is used on a gel cell battery, poor performance and premature failure is certain.

[old Jack]

I have used wet cell deep cycle, sealed AGM, Optima and Oodessy batteries under the bonnet in extended outback touring since the early 1980's and without any doubt the Oodessy in metal case lasted the longest, almost double of the Optima!
Negatives of all the above is weight, limited discharge capacity if you want a decent life out of the batteries.

LiFePo4 batteries in the rear cargo area have lasted the longest, have had the most capacity, are the lightest and most compact for the usable amp hours and the number deep cycles but they come at a cost which many people find hard to justify.

OJ.