What is Depth of Discharge?
DOD refers to how much of a battery’s capacity has been used. For instance, a battery that has been drained 30% has a 30% DOD, and 70% of its capacity remains.
All batteries need extra power reserves for safety -- and near-empty batteries can’t provide enough.
Some days, you’ll use more electricity, because of heavier loads, higher temperatures, etc. Or solar or wind systems won’t produce enough energy.
When batteries have less than 20% storage remaining, you can run out of electricity.
That could mean no power for HVAC loads, inadequate power for large appliances, even downtime for manufacturing and shipping operations.
High DOD can also shorten battery life.
Deep discharging can drastically shorten battery life -- and that means you’ll pay for more for energy storage.
Beware: Some battery companies tout 80% - 100% DOD rates... and put you at risk:
And beware companies that promise 80%+ DOD. This isn’t just dangerous for your system’s performance and longevity - it’s also a common sales ploy to sell you an undersized system (and make the price, for less storage, seem less overpriced).
So protect yourself: Size batteries for no more than 50% DOD -- and comparison shop based on that number.
You need extra energy reserves, no matter which battery technology or company you select; make sure you get the system you need and deserve.
“What if my current system drops below 50% DOD often?
Installing an extra battery usually helps. Depending on your installation, a backup generator can also ensure you have power during extended deep discharging.