Why do 3.2V LiFePO4 solar street lights have a 10-year warranty?
Firstly, talking about some low-level technical rumors
1. The 12V solar light is much brighter than 3.2V
Let me ask one common-sense question: which one is much brighterbetween car headlights and home lights?
Usually car headlights are 12V or 24V, but home lights are 220V Very low-level technical knowledge tells us, there is no directrelationship between voltage and brightness.
2. 3.2V system is too simple
To some extent, this point is not wrong. 3.2V system is more simplethan 12V system, but this is not the key point. As everybody known,lithium iron phosphate battery needs do inter-node protection anduniform flow balance among the four batteries if it needs connect inseries to 12V,However, the requirement for consistency of fourbatteries which connect in series is very high. Besides, consistencyfor each battery work temperature is much higher - it's too difficultto ensure this point for solar outdoor lights. Definitely, if it is indooruse laptop or outdoor electric car, you can use expensive BMS systemto ensure this point, but for a few hundred RMB solar lamps, it's evenmuch cheaper than protector chip. In addition, factories usually useechelon utilization and so-called B grade lithium iron phosphatebattery (the price of A grade battery is three times more than that oflead acid battery for several years, so it is unlikely to be widely used).Not to mention battery consistency.
Therefore, the 3.2V lithium iron phosphate battery with simplestructure and no need inter-node protection has an unprecedentedopportunity. After six years testing, the failure rate is even far lowerthan that of AC electric street lights.
By the way, it is true that ternary lithium battery itself is a grade, butit is mainly used for indoor products (laptop, power bank, etc.), notsuitable for outdoor use.
Inflammable andexplosive features can be controlled by itself(except Samsung), only if there is enough BMS cost (Tesla), whilethe lighting factories clearly could not stand the cost. Therefore, solarstreet lights which caught fire and explosion all use 12V ternarylithium battery. A burnt lamp can be replaced by a new one. However,if the forest caught fire, manufacturers and engineers are not assimple as losing money.
3. 3.2V,excessive current will burn out MOS and wires
This idea is very funny. Solar street lights are just less than hundredwatts, now the high conductivity of MOS, IGBT technology isalready very low price. Below 50A electricity flow is only a fewRMB, wire is needless to say. A total of dozens of centimeters longwire, you didn't even have the courage to use thick wires? I think it'scaused by long time habitual thought of cutting corners.
4. 3.2V is not suitable to constant current intelligent control andmaximum power point tracking(MPPT)
Before I refute this opinion, I firstly talk about technical commonsense: voltage fluctuation between fully charged and empty dischargeof 3.2 V lithium iron phosphate battery is very small, the release ofthe main capacity concentrated in 2.9 V to 3.3 V, just landed on therange of white LED junction voltage - this is "quantum entanglement"designed by God. Even if full power is used to drive the white LED.it will not exceed the maximum rated power of the LED. Therefore.PWM control is sufficient, no need to use constant current drive withhigh failure rate. Secondly, about the intelligent control and maximumpower point tracking (MPPT), I think that they are designed to reducethe high cost of panels and batteries in those years, but until nowsome people still think photovoltaic story is not finished, and same asthe controller, the stock thinking.New energysubsidies werebasically canceled, Lithium battery and solar panels are as cheap asthe price of 20 meters cable now, not includes light pole, which eachAC street lights will need at least 50m cable.
In this underlying algorithm, the price of solar panels is below 3015RMB/watt, light tracking technology is unnecessary; less thanRMB/watt, MPPT(maximum power point tracking)is no sense. Atpresent, it is less than 2 RMB/watt, cable is no use, and state subsidyis completely unnecessary.
Instead of using MPPT for the sake of selling points, simply addingsolar panels is much cheaper and more reliable. Intelligent control isthe same. ost solar street lights are installed in a backward area.Idon't believe electrician in village walks dozens of miles of mountainroads to adjust light control time with a mobile phone every day. It'smore like pseudo-requirements. Their purpose is to sell the controllerat high price or they don't understand technology. Actually, increasethe solar panel configuration can save more money and efforts.
Now, let me introduce the advantages of single 3.2V lithium ironphosphate battery:
1. The battery doesn't have balance problem and its life time can beover l5 years.
Because most of the manufacturer of lithium iron phosphate batteriesfor electric cars are main board-listed companies, the dischargestrength is 3C in outdoor conditions. Natural design is perfect. Whenused on solar street lights, the charging intensity is only 0.1C-0.3CThere is no problem for the car to use 8 years and solar street lights touse 15 years. I often give the example of Liu Xiang, who is too old for100 meter hurdles, but who will surely serve to 80 years old for slowwalking.
2. The controller and lamp bead are directly attached together. Thereliability is greatly improved. The installer only needs to plug in theDC plug.
3. The power generation of weak light is much better.
It is very easy to make the solar street lights work well in sunny days.The key point is to generate precious power by weak light in rainyand cloudy days. The reason is very simple. The photovoltaic effectgenerates electromotive force(voltage)by the light intensity.Generally speaking, when you start driving uphill, do you shift thefirst gear or the fourth gear? 3.2V will not stop weak current chargingin cloudy and rainy days.
4. LiFePO4, can be seen from the molecular formula that lithium ironphosphate battery has no heavy metals and scarce resources, and itwill must become cheap and clean energy storage battery. Cobalt isscarce in ternary lithium battery, which tripled at price last year only.
5. There are still a few advantages, will share in another article aftera period of time.
List a few disadvantages of 3.2V 
We do have to thicken the wires, and even usethe military plug.
There are high requirements for supply chain management andproduction equipment. For example, iron-lithium phosphate batteryproducers are at least main board-listed companies with thresholds ofcapital and quantity . For another example, full parallel connectionrequires a high level LED suppliers. We only use the world's firstbrand- Japanese Nichia LED, and the batch tolerance is less than onemillionth.
For the factory of lead-acid, controllers and ternary lithium, has asubversive effect, who usually writes the traditional governmentbidding documents.
In summary, the appeal for low failure rate, long life span and highcost effectiveness, are the real pain points for solar street lightindustry for many years. Two evils choose the lesser. We used sixyears'time, installed tens of millions of lights, prove and make surethat choosing the 3.2 V system is the future.
A final word, more and more competitors are choosing the 3.2Vtechnical path.
In a few days, we will launch Nichia LED 150 watt, over 30.000lumens of high-brightness solar street lights. It will be the brightestsolar street light in a single lamp head, and life span is 15 years.
To sum up, 3.2V lithium iron phosphate battery has gradually becomea major trend now. Many small factories in Shandong, under thecondition of no technical background,imitate the technical patheasily, failure rate, performance cost ratio and lifespan are muchbetter than the 12 V products.
Well, let me finish here. Single 3.2 V lithium iron phosphate battery,"Unlimited sunshine, wireless world" micro grid new lighting erahas begun. Thanks to all of 3.2 V peers, we work together to cut thecable. Replace the last five kilometers of outdoor power grid withsunshine cover.
