What is Depth of Discharge (DoD)?
A depth of discharge (DoD) is the measure of how much energy from a battery has been used.
The deeper the discharge, typically the shorter the life expectancy of the battery. A battery that is frequently discharged to 80% may last 1,000 cycles. Whereas, a battery discharged to only 30% may last 5,000 cycles.
Why Is Depth Of Discharge Important?
The deeper the battery is discharged, the more stress is placed on the battery, which can lead to reduced performance and shorter battery life.
When deciding on a battery for your application, it’s important to consider both the depth of discharge and the number of cycles you need from the battery.
What is the depth of discharge formula?
Depth of discharge is normally expressed as a percentage.
For example, if a 100 A h battery is discharged for 20 minutes at a current of 50 A, the depth of discharge is 50 * 20 / 60 / 100 = 16.7 %. The complement of the state of charge is the depth of discharge, which decreases as one rise.
Try to Avoid Fully Discharging Your Battery
The length of time a battery will last is determined by how often it is charged and discharged. The usefulness of a battery’s life is shortened if it is completely discharged.
As a result, all batteries require additional power reserves for safety and near-empty batteries can’t give enough.
Some days, you’ll use more power because of heavier loads, hotter temperatures, or other factors.
On those days, if you top off your battery before it’s completely discharged, you’ll help extend its life.
Keep Batteries Above 20% Storage
If your batteries have less than 20% remaining storage capacity, you will run out of power.
This might include no electricity for HVAC equipment, insufficient power for major appliances, and even the inability to operate manufacturing and shipping processes.
High DOD Can Also Shorten Battery Life
When a battery releases a lot of energy in a short period of time, it produces a high amount of discharge.
Some batteries suffer from poor quality deformation, while others are designed that way.
Battery life can be significantly reduced if you deep discharge your batteries — and this will result in you having to pay extra for energy storage.
Lead Acid Depth Of Discharge
The suggested Depth of discharge for lead-acid batteries is 50%, which means you should not fully drain your battery capacity, otherwise, it will shorten the battery life.
One of the things that can affect the efficiency of a lead-acid battery is Sulfation.
Sulfation is the lead sulfate that coats the lead plates inside the battery, and it can happen when batteries are left in a discharged state for too long.
If this sulfation happens, it will reduce the capacity of the battery and shorten its lifespan.
How to prevent sulfation?
The best way to prevent sulfation is to keep your lead-acid batteries above a 50% state of charge.
This can be accomplished by regularly charging your batteries.
How to extend battery life of lead acid
- Don’t let your battery completely drain.
- Don’t overcharge the battery.
- Don’t overload the equipment.
- Don’t store batteries in extreme conditions.
- Do keep the battery clean.
Lithium-Ion Depth Of Discharge
The majority of current lithium-ion batteries have DoDs ranging from 80% to 95%, with many leading solutions, such as the durable Blue Ion 2.0 battery from Blue Planet Energy, having a 100% depth of discharge and considerably longer lifespan.
How to extend the battery life of lithium-ion
- Use partial-discharge cycles.
- Avoid charging to 100% capacity.
- Select the correct charge termination method.
- Limit the battery temperature.
- Avoid high charge and discharge currents.
- Avoid very deep discharges (below 2 V or 2.5 V)
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