Close this search box.

Depth of Discharge is Not Your Friend


Batteries. They are a big topic of conversation for our customers. Whether it is interacting with vehicle batteries, either testing or charging, or managing the batteries in your equipment, such as a jump starter of work light, 90% of the calls, emails and messages we receive are related to batteries in some way. So, we thought we would address one of the biggest enemies of battery health and longevity – deep discharge.

The vast majority of batteries, even deep cycle batteries, fare poorly when deeply discharged, especially when they are allowed to stay in that condition for any length of time. This is true of lead acid batteries and lithium batteries, as we will get to shortly. To be clear, this is true of all lead acid and lithium batteries, whether they are installed in a vehicle, equipment or used for any other purpose. Low state of charge causes damage to batteries and often this damage is permanent.


Lead Acid Batteries. We all know that, if we leave our car parked in the driveway for four months, it isn’t going to start because it has a dead battery. Likely, that battery’s State of Charge has dropped well below what it takes to turn the starter. This is the danger zone for lead acid batteries because it accellerates a natural process called desulfation, which essentially robs a battery of its energy storing capacity. The longer the battery sits in a deeply discharged state, the more compromised it becomes. Even if that battery is fully charged after the dead period, it likely has lost a percent of its capacity that is difficult, sometimes impossible to restore, depending on its condition before the dead period occurred.


Similar to your vehicle battery, the battery in a lead acid jump starter can also be damaged by prolonged periods in a deeply discharged condition. That’s why we recommend signing up for recharge reminders, so that you don’t forget to regularly recharge your unit. We recommend charging your jump starter every 90 days to keep it in optimal condition. Like your vehicle battery, failure to charge your lead acid jump starter will result in desulfation, reducing the effective power of your jump starter until it is no longer useful.


Lithium Batteries. The first thing to note is that there are many different lithium battery types on the market today, and the rules for one don’t apply to all others. That said, there are some general guidelines that apply to most lithium battery constructions. Like lead acid batteries, lithium batteries do not fare well when deeply discharged. In fact, most lithium batteries incorporate a Battery Management System that prevents charging if the battery’s State of Charge dips below a predetermined level. But, even if a specific lithium battery allows charging when deeply discharged, battery capacity could be compromised. Like sulfation in a lead acid battery, in a lithium battery, deep discharge results in degradation of the anode and cathode material such that the battery is much less powerful than it was originally. Again, this is true of a lithium battery installed in a vehicle or equipment containing a lithium battery.


So, the moral of the story is that your battery, no matter the type, fares best when it is kept at or near full charge. Care should be taken to ensure that regular charging takes place on equipment or vehicles that are used only periodically. In the case of a seldom used vehicle, we strongly recommend connecting a quality battery maintainer, such as our PRO-LOGIX PL2112, to keep the battery fully charged during periods of inactivity. Deeply discharging batteries is a practice that should be avoided whenever possible. If you do put a battery through a tough usage cycle, it is best to recharge that battery as quickly thereafter as possible.

2 Responses

  1. We just got home from spending 6 months in south Texas, in storage during that time, my Spor Trac had a new smart charger attached. Upon starting it, the Sport Trac went into panic mode and started the alarm. I went through this a year ago at the same time when we got home. Back then I disconnected the battery and had an inexpensive maintainer on the battery. Unbeknown to me the charger was junk, so when I connected it didn’t have enough power to start and it went into panic mode.
    This time I left the battery connected with a new smart maintainer connected and it went into panic mode.
    I called my neighbor who is a retired Auto Mechanics Teacher at Michigan University, he came right over and brought his expensive Snap-on battery load tester and tested the battery—- it was BAD. My neighbor said “he has seen a lot of battery maintainers cooking batteries and that may be the reason my battery was so bad”. This bothers me, because I must have no less the 8 battery maintainers in service when we are gone for 6 months. To aggravate me more, I had a problem with another battery, but it was in a gas golf cart at out Texas residence. That battery(walmart) was almost new; I had a battery maintainer on it. After an extensive research, I figured out the battery had an internal short and it burned up the voltage regulator. I couldn’t blame the battery maintainer, but it was first on the list. I filed a claim with WalMart for the voltage regulator; the Walmart automotive service manager confirmed it was the shorted battery that caused the problem, WalMart made restitution.

    Now back to my Sport Trac. My thinking was this battery was not quite 2 years old, it had a 3 year warranty. I called my Ford dealer to check the warranty.( time few by-where did it go) They told me that battery was installed 6-2017, heck that was 5 years ago; was this battery bad because of the battery maintainer or was it just old? But when I took the battery out of the Sport Track there was a date label down along the side that showed this battery was made 11/2016. Now we just added another year to the age of this battery.
    So in your professional view, was it the battery maintainer or the age of the battery? And can these small battery maintainers cook batteries as my neighbor said?

    1. Rich – Thanks for comments and question. The reality is that some maintainers (smart or otherwise) can indeed dry out a battery during periods of long term storage charging. Often, this occurs due to an excessive parasitic drain, which essentiall never lets the charger sleep or even lower its output to “trickle” status for long. Your situation could be the result of having both an older battery and a potential excessive drain, which could easily have cause the battery to become compromised. PRO-LOGIX chargers and maintainers utilize a unique “rest” phase where the charger is completely off except for occasiona monitoring of the battery. While our approach is not completely foolproof (some excessive drains or compromised batteries could result in the charger spending very little time in “rest” phase), what we have experienced in the lab and out in the field is that our approach greatly reduces the likelihood of drying/boiling a battery in long term storage charging. A great product for this application is our PL2140, 4A Charger/Maintainer. I hope this is helpful. Jim from Clore Automotive

Leave a Reply

Your email address will not be published. Required fields are marked *

Clore Story


Recharge alerts

Related News