The Three Most-Asked Questions
Our team here at Northeast Battery fields a ton of questions about batteries and how they work. While we get a range of questions for different battery applications, we thought we would go ahead and answer the three most commonly asked questions about lead acid batteries. Ready? Here we go.
Do lead acid batteries develop a memory?
The quick and simple answer is, no. For those looking for extra credit, check out the below.
Lead acid batteries are not affected by the memory effect. The memory effect was limited to the nickel-cadmium batteries in the 70’s and 80’s. The memory effect was the occurrence when a nickel-cadmium battery would develop a cyclic memory that would allow the battery to “remember” how much energy was previously drawn.
During subsequent draws, the battery would not deliver more than it had before. Modern day nickel-cadmium batteries do not experience cyclic memory.
Do lead acid batteries discharge when not in use?
All batteries experience some amount of self-discharge, yes. But, the rate of discharge for lead acid batteries depends on a few key factors.
- Temperature: The warmer the environment while a battery is in storage, the faster the rate of self-discharge. For example, a battery being stored at an average temperature of 80℉ will discharge at a rate of 4% per week. Whereas a lead acid battery being stored at 65℉ will only discharge at a rate of approximately 3% per month.
- Length of Storage: The amount of time a battery spends in storage will also lead to self-discharge. A lead acid battery left in storage at moderate temperatures has an estimated self-discharge rate of 5% per month. This rate increases as temperatures rise and as the risk of sulfation goes up.
- Sulfating: This is a buildup of lead sulfate crystals and it occurs when a lead acid battery is left sitting without a full charge. Even if you are giving your battery a small charge such as putting it in the car and letting it idle, this is still not enough to combat the self-discharge that can take place.
- Dirt: Dust and dirt on a stored battery can also create a reaction that leads to self-discharge. You can easily prevent this by wiping down the top of the battery with a clean, dry, and soft cloth. The best way to reduce the amount of self-discharge while your batteries are in storage is with the three C’s. Keep them clean, cool and fully charged.
Do I need to completely discharge my lead acid battery before recharging it?
This is a hard and fast NO. By fully discharging your lead acid battery, or even discharging it below 80% of its rated capacity, you could damage the battery.
The belief that a battery needed to be fully discharged before recharging goes back to the memory effect issue. (See question 1.) Since that is no longer an issue (and never was an issue with lead acid batteries) there is not a need to fully discharge.
By discharging a lead acid battery to below the manufacturer’s stated end of life discharge voltage you are allowing the polarity of some of the weaker cells to become reversed. This causes permanent damage to those cells and prevents the battery from ever being recharged.