Battery Practicability

Time is money. The best battery is of little use if you have to constantly take care of it, or - worse - hire a caretaker.

Battery Practicability
Lead-acid battery maintenance is annoying, time-consuming, costly but necessary.

A battery simply has to work. Ideally, it should be maintenance-free and even better if the battery status can be checked on remotely or if the battery itself reports problems - should any ever occur. Exactly this ideal situation is achieved by a lithium iron phosphate (LiFePO or LFP for short) battery with BMS (battery management system).

All the disadvantages associated with old battery technologies (such as lead-acid, nickel-iron, nickel-cadmium, etc.) are actually irrelevant for modern LiFePO batteries. However, it might make sense to make a comparison here to see how big the advantage over these old technologies really is:

Properties Lead-acid LiFePO4 Comment
Energy density MJ/kg 0.11 0.32-0.64 Energy/weight
energy density MJ/l 0.25 0.35-0.9 energy/volume
cycle stability 1000-2000 2000-5000 SoC 100<->20
typ. Lifetime up to 10y 20-25y 200 cycles/year
usable capacity 50-60% 80% acc. to design.
efficiency 70-85% 90-98% of charge current
load capacity 0.1C to 10C see below C-coeff.
no H₂ outgassing ✔️ oxyhydrogen hazard!
maintenance-free ✔️
without fire hazard ✔️ ✔️
temp. range for discharge 0-55°C -45-55°C recommended 20-40°C


The C-coefficient describes the charge or discharge current (generally "current carrying capacity") in relation to the maximum capacity of a battery. It is therefore easy to determine what current load a cell can withstand. Assuming a cell has 400Ah, a C coefficient of 3 ("3C") means that this cell can deliver or absorb up to 1200A. A C coefficient of 1 would be 400A and a C coefficient of 0.5 would be 200A.

Charge and discharge characteristics of LiFeYPO₄ cells

The LiFeYPO₄ cells used by PetaJoule are specified up to 10C, but are dimensioned by us so that a load of max 0.5 to 1C occurs during operation. To get an idea, you can browse through the original manual of the cells from the manufacturer Winston here: