What’s difference between 3.2V Lithium and 12V lithium
Hansen Solar Lighting is specialized in manufacturing solar street lighting and solar garden light, today I would like explain solar lighting application on difference between 12V lithium and 3.2V lithium.
From 2017, there are lots of 3.2V solar lighting system in the market, their selling points: 1. LiFeO4 battery has longer cycle time and lifespan 2. It is available charging in rainy days even for 5V solar panel. 3. Warranty is long to 5 years, even 10 years.
For any persons who know a few about lithium batteries and overturn these theories easily, firstly, cycle time for new LFP battery can reach 2000times(DOD100%), its lifespan is indeed long, while most supplier use 3.2V second-hand(refurbished batteries), their cycle times is largely cut-downed, so its lifespan cannot be guaranteed. Secondly actually solar panel is able to generate little electricity in rainy days, because solar panel requires sunshine and generate silicon-ions to move and get electricity, how solar panel can have electricity without sunshine(solar energy). Thirdly, 5-10 years warranty perhaps is a trick, low quality solar does not have capacity for 10 years usage.
Analysis for 3.2V/3.7V solar energy lithium system application
Actually low voltage single series system is originated from some supplier, originally which were mainly designed for some kinds of products below 10W LED system,use single series LFP or Li-ion battery cell to reduce cost and get more orders in Chinese and international market of garden lights. While then some supplier put this solution in 30W system and raid the market,their marketing publicity called:
1. Lower price at same capacity
2. Less electricity with same brightness.
Now we are explaining their irrationality on these two points.
1. Lower price at same capacity
In industry,as we know, in former lead acid industry we are used to using AH expressing battery capacity(standard should be WH V*AH), mainstream 12V lithium is in 4 series cells and 3.2V is only one series, for example, 12.8V 2600mAH is 4series cells and 3.2V is one series, while its capacity is same if we do not care about voltage, but 3.2V use less cell and lower cost,its cost is 1/4 of 12.8V system.
2. “Less electricity with same brightness”is pseudo-proposition
Firstly for Li-ion, its voltage range is 2.75~4.2V, 3V LED is usually in 2.8V~3.2V(different LED has different range),lighting efficiency and lifespan will be affected when input voltage beyond the range, controller will start PWM to adjust and lower voltage, so li-ion battery will not affect so much, while for LiFeO4 battery, its voltage is 2.5V-3.65V, LED brightness will be reduced when below 2.6V.
Secondly,for 30W system, the actual output power is less than 20W, output current is >7A,charging terminal(solar panel),max power is 60W and max charging current is up to 15-20A, which means higher requirement for safe and heat dissipation, what’s more it causes higher energy loss in internal resistance, switch and etc, it easily to make controllers and cell damaged.and it also can make LED burned more easier.that’s why most suppliers are not launch low voltage controlling system.
3. It requires higher consistency for battery cells at condition of large parallel circuit, so LED does.which affect lifespan and quality.
4. Lower voltage means large current and cause large electricity loss in system itself and wire.
