Lithium-Ion vs Lead-Acid battery
Let’s consider a 12V battery to store energy from a solar powered system (ie: Off-Grid). For this application, we need a storing capacity of 105Ah.
If we equip the system with a Lead-Acid battery, the actual capacity of the battery will be 2 x 105Ah = 210 Ah (no more than 50% DOD).
Let’s take as an example the 12V lead-acid battery for power applications: DAIJIN SG. This device measures 50cmx25cmx24cm, weighs 76Kg and has a capacity of 210Ah. The useable capacity is 105Ah (depth of discharge 50%), and for high discharge applications, actual capacity will be only 65Ah.
The table below summarizes the characteristics of the two batteries for our application:
|Size / Volume||26cmx17.2cmx22.5cm = 10.0L||52.1cmx26.9cmx23.3cm = 32.7L (x3.2)|
|Charging||Fast to 100%||Fast to 80%|
|Wasted||0%||15 à 20%|
Lithium-ion vs Lead-Acid cost analysis
We take the example of a solar installation for a standalone building (Self Sufficient Home). The storage capacity for the battery is 50KWh.
The application need is summarized in the above table:
|Discharge Power||10KW (or 5 hours running time at C/5)|
|Cycling frequency||1 charge discharge/charge per day|
|Average ambient temperature||23°C|
|Expected Lifespan||1900 Cycles, or 5.2 years|
The costs of delivery and installation are calculated on a volume ratio of 6:1 for Lithium system compared to a lead-acid system. This assessment is based on the fact that the lithium-ion has an energy density of 3.5 times Lead-Acid and a discharge rate of 85% compared to 50% for AGM batteries.
Based on the estimated lifetime of the system, the lead-acid battery solution-based must be replaced 3 times. Lithium-Ion solution-based is not replaced during operation (2000 cycles are expected from the battery)
The cost per cycle, measured in US$ / kWh / Cycle, is the key figure to understand the business model. To calculate it, we consider the sum of the cost of batteries + transportation and installation costs (multiplied by the number of times the battery is replaced during its lifetime). The sum of these costs is divided by the net consumption of the system (50kWh per cycle, 365 cycles per year, 5.2 years of use). The result is summarized in the table below:
|Installed capacity||100 KWh||58 KWh|
|Usable capacity||50 KWh||50 KWh|
|Lifespan||500 cycles at 50% DOD||1900 cycles at 90% DOD|
|Battery cost||US$16,400 ($164/KWh) (x 4)||US$44,497.00 (700€/KWh) (one shot)|
|Installation cost||US$1,095 (x 4)||US$1,095.00 (one shot)|
|Transportation cost||USD30.70per KWh (x 4)||US$10,959.00 per KWh (one shot)|
|Cost per KWh per cycle||US$83.30 / kWh / cycle (+81% vs Li-Ion)||US$46.03 / kWh / cycle|
* Others Information
|hemistry||Voltage||Energy Density||Working Temp.||Cycle Life||Safety||Environmental||Cost based on cycle life x wh of SLA|
|LiFePO4||3.2V||>120 wh/kg||-20-60 °C|| >2000(0.2C
rate, IEC Standard)
lower than SLA
|Lead acid||2.0V||> 35wh/kg||-20 – 40°C||>200||Safe||Not good||1|
|NiCd||1.2V||> 40wh/kg||-20 – 50 °C||>1000||Safe||Bad||0.7|
|NiMH||1.2V||>80 wh/kg||-20 – 50 °C||>500||Safe||Good||1.2-1.4|
|LiMnxNiyCozO2||3.7V||>160 wh/kg||-20 – 40 °C||>500||better than LiCo||OK||1.5-2.0|
|LiCoO2||3.7V||>200 wh/kg||-20 – 60 °C||> 500||Unsafe w/o PCM||OK||1.5-2.0|