Battery chemistry & storage
Enter your capacity and target charge level. See maximum charge power and estimated charge time across six chemistries.
How it works
Step 1
Maximum charge power scales directly with capacity, since it's based on a C-rate applied to the nameplate size. The power density comparison covers a related power constraint from the discharge side.
Step 2
Targets at or below 80% give the most accurate estimate, since real charging tapers as it nears 100%.
Step 3
A slower charging chemistry only matters if your charging window is genuinely tight. The charge rate vs lifespan tradeoff tool covers the other side of pushing for faster charging.
LFP, NMC, and sodium-ion all typically support charging at up to 1C under normal conditions, meaning the difference between them on raw charge speed is usually small. Where they differ more meaningfully is in how well they tolerate sustained fast charging over many cycles, covered in the charge rate vs lifespan tradeoff tool, and part of what the UL 9540A test method evaluates when it looks at how a pack responds to high current under realistic operating conditions.
Lead acid's chemistry can't accept high current without excess gassing and heat, while flow batteries are generally built for steady, moderate charge and discharge rather than rapid cycling. Both effects show up directly as a much lower sustainable C-rate, and therefore a much longer charge time for the same capacity, which the battery charge time from grid calculator can turn into an actual number of hours for your specific charger and capacity.
This calculator assumes a constant maximum charge rate, which holds up reasonably well for target levels at or below about 80% to 90%, but real charging tapers as the battery nears full to protect the cells, a tapering curve NREL's energy storage research models in more detail than the flat-rate estimate used here. Treat time estimates for targets above 90% as a lower bound rather than an exact figure.
If your charging source is limited by power rather than time, the power density comparison covers how much weight each chemistry needs to deliver a given amount of power, a related constraint on the charging side too. The state of charge estimator can help track where your battery actually sits during a charge cycle, and fast charging is only as useful as the equipment delivering it, which the inverter sizing for future battery addition tool checks from the inverter side.
Questions
LFP, NMC, and sodium-ion all typically support charging at up to 1C, meaning a 10 kWh battery can accept roughly 10 kW of charge power and reach 80% state of charge in about 48 minutes under ideal conditions. Lead acid and flow batteries charge far more slowly, often taking several hours to reach the same state of charge.
Lead acid's chemistry can't accept high charge current without excessive gassing and heat buildup, which both wastes energy and accelerates degradation, so manufacturers rate it for a much lower sustainable charge C-rate. That slow charge acceptance is a structural limitation of the chemistry, not a fixable design choice.
It matters most when your charging window is limited, such as a short sunny period, a narrow off-peak utility rate window, or a generator that only runs part of the day. If you have all day to recharge from solar, a slower charge rate may not be a practical constraint at all.
No. Most chemistries taper charge current as they approach full state of charge to protect the cells, so the last portion of a charge cycle takes disproportionately longer than the first. This calculator estimates time using a constant maximum rate, which is closest to accurate for target charge levels below about 80% to 90%.