Battery Life Span

Batteries have a life span for how useful they are, when they are no longer useful they are 'dead' and disposed of (hopefully recycled). The length of a single charge (and thus the life span) depends on the device the batteries are used in.

A simple battery tester is sufficient to classify the stages of a battery's charge level.

Full - The battery is nearly at full charge, if not at full charge.

Good - The battery is full enough that it will power most devices that are designed for the battery.

Weak - The battery is mostly depleted and may only work in low demand devices. Rechargeable batteries should be recharged at this level.

Poor - The battery is almost fully depleted and likely won't work in anything. Rechargeable batteries might be too far gone at this level.


Alkaline Primary

Life Span: One charge

Package Charge: Full

Some devices will get almost all the charge out of the battery while others will still leave a decent amount of the charge.

Low drain devices could go for months or even years on a single battery.

High drain devices could take it down quickly but leave enough charge that a low drain device might get a few weeks or even months from the battery.

As the battery is drained, the power output drops and performance of the device could suffer, particularly high drain devices. Even dropping to Good level can impact performance.


Lithium Primary

Life Span: One charge

Package Charge: Full

Most devices will get almost all the charge out of the battery, those that don't might leave enough charge for limited use in other devices.

Devices will usually get the same or better duration from a single charge.

As the battery is drained, the power output barely drops and might not have a noticeable impact on performance until drained to Weak level.


Ni-MH Rechargeable

Life Span: 500-1000 charges

Package Charge: Partial

Many devices will get almost all the charge out of the battery, not that it matters since it isn't an issue to recharge these batteries before they are fully drained - and will actually help provide more recharge cycles.

The first few charging cycles (drain and recharge) should be full cycles (drain to Weak state, charge to Full state). Can be useful to repeat the full recharge cycling every 6-12 months.

Regular recharge cycles can be incomplete (keep it within the Good state). This stresses the battery less and can provide more recharge cycles, potentially up to 1000.

Fast charging can cut back the number or recharges the battery can handle, possibly dropping it to below 500 cycles.


Li-Ion Rechargeable

Life Span: 500 charges (approx.)

Package Charge: Partial

Most devices will get almost all the charge out of the battery, however it is not required since recharging the battery before it is fully drained will not harm it. Recharging early can gain some recharge cycles, but doesn't really gain any total run time. (Recharging the battery fully once after an hour of running will directly replace recharging the battery three times, each after 20 minutes of running each time.)

The first few charging cycles (drain and recharge) should be full cycles (drain to Weak state, charge to Full state). Can be useful to repeat the full recharge cycling every 6-12 months.

Regular recharge cycles can be incomplete (keep it within the Good state). This stresses the battery less and can provide more recharge cycles, potentially over 500. Avoiding reaching full charge has more impact than charging before it is weak - optimization is achieved by not fully charging the battery every time.

Fast charging can cut back the number or recharges the battery can handle.

While exposure to extreme temperatures can reduce the number of charge cycles, this battery handles a wider range of temperature than the other chemistries covered above.



The best way to get the most out of batteries is to keep a battery checker on hand and track the batteries.

The tester can be used on batteries that have been sitting for extended periods, found after being 'misplaced' for a while or fresh out of a device that doesn't seem to be working right. This will indicate if the remaining charge might work in a low-demand device or has enough charge for a regular device. It can also indicate potential issues with a device - such as a digital camera that works with 1.2V Ni-MH and 1.5V Alkaline but for some reason doesn't work with 1.5V Lithium Primaries.

Tracking the batteries can be as simple as keeping certain sets together so they 'die' at the same time or full on tracking of how much 'life' they have had.

While I have named these tracking methods, these are just to help separate them on the list while giving an idea of what the tracking involves.


----- Primary Battery Tracking

Not particularly needed, aside from squeezing a little more power out of the batteries to save a little money.


One and Done Tracking

This is the standard method used for Primary batteries (Alkaline and Lithium) since these have only one charge. Use the battery and then send it to recycling (or more often, the trash).

Pros: easiest tracking.

Cons: most expensive tracking.


Once and Again Tracking

Another method for Primary batteries where batteries that no longer supply enough power for a device, a new set is put in that device. The set removed is then used in a low-demand device until it runs out. This is improved by including a battery tester to verify the charge of the batteries pulled from a device, so the charge level can be confirmed and any that are too weak can skip being used in a low-demand device.

Pros: not as wasteful and 'One and Done', shaves a little bit of cost off.

Cons: depending on the efficiency of the involved devices, a pile of batteries suitable for low-demand use could build up.


----- Rechargeable Battery Tracking

Already saving money over using Primary batteries, even more money can be saved by avoiding accidental discarding and battery damage.


Pile Tracking - aka Not Tracking

Used with Rechargeable batteries, when they are depleted they might be dumped in a 'discharged' pile for charging later. Once charged, they are dumped in a 'charged' pile to be taken from when batteries are needed. A battery tester could be considered necessary to check batteries before use and after charging.

Pros: easiest tracking for rechargeable batteries, works perfectly fine if all devices involved use only a single battery.

Cons: see 'Battery Combat' at the bottom of this page, can't track used life span.


Loose Tracking

When the batteries are first gotten, they are used as required. After their first use, they are kept together in some way.

Some examples: A pair of batteries used in a TV remote are charged and set aside to be used as a pair again. A single battery from a flashlight is charged and set aside to be used in a single battery device again. A set of pair of batteries used in a wireless mouse are charged and set aside to be used as a pair again, the pair previously in the TV remote go in the mouse.

Pros: takes little more effort than Pile Tracking, can avoid too much 'Battery Combat' as explained at the bottom of this page.

Cons: can easily lose track of groupings and break down into Pile Tracking, difficult to try adding any form of tracking used life span.


Group Tracking

Batteries are labeled (differing brands purchased, permanent marker) so they become different groups. A record of how many are in each group is kept in the battery storage. Batteries within the same group can be used as needed and placed in a separate location when discharged. Once all batteries from a particular group are in the discharge location, they can all be charged and put back into the ready to use location.

Pros: avoids most 'Battery Combat' as explained at the bottom of this page, can track the used life span.

Cons: takes additional time and space, situations can arise where an insufficient supply of batteries are ready for use, if marker is used to label then it must be monitored so it does not wear off.


Set Tracking

This is Loose Tracking stepped up, using the labeling of Group Tracking - in particular, permanent marker. Each battery is assigned a grouping and marked as part of that group.

For example: A TV remote that takes two batteries so a pair are marked as 'A1'. A computer mouse requires two batteries as well so a pair are marked as 'A2'. A flashlight also uses a pair of the same size as those devices, so another set is marked 'A3'. At this point, it would be nice to have a spare set for when any of those devices run their batteries dry, so another pair are marked 'A4'. Another flashlight uses four of the same size batteries, so we labeled four batteries as 'B1'. This flashlight is used for work and needs one battery change mid-shift so another set of four are marked 'B2'. Another flashlight uses three batteries, which are then labeled 'C1'. A few other devices need a single battery, a set of four are left unlabeled since only one at a time will be used.

In this way, a battery labeled A1 must be charged at the same time as the other A1 and must be used in a device together with that battery. At no point should any batteries from different groups be used together. The B1 and B2 batteries would be charged together. Set C1 should be charged either one at a time to ensure even charge, or with one of the singles that is depleted to a similar level - this should minimize the risk of 'Battery Combat' as explained at the bottom of this page. The unlabeled batteries are best charged as singles to minimize the 'Battery Combat' risk.

Pros: avoids more 'Battery Combat' as is explained at the bottom of this page, can take less space then just Group Tracking, can track the used life span.

Cons: labeling must be monitored so it does not wear off.


Device Tracking

This is the next step up from Set Tracking. Particular battery groups can only be used in a particular device until they approach 'end of life'.

Using the example in Set Tracking: Group A1 can only be used in the TV remote, and when A1 is charging the TV remote is out of commission. A2 can only be used in the computer mouse, when the batteries need charging the mouse is out of commission until they are charged. Since the flashlight goes through the A3 batteries in about a week, set A4 is designated as for the flashlight only as well. Set B1 and B2 are already restricted to their flashlight. C1 is already device restricted, though they must be charged individually. The single batteries must each be labeled and be assigned to a particular device: D1, D2, D3, D4.

By using a set of batteries in the same device every time, they become adapted to that device. This can make them less effective if used in another device, but will typically be a little more effective in the device they have adapted to. It is still a good idea to 'exercise' them periodically by using them in a device that can drain them a little farther than their usual device - this is easier with a charger that can occasionally 'cycle' the batteries by draining them before recharging them (cycling them every time may prevent adapting to the device they are assigned to).

Pros: avoids nearly all 'Battery Combat' situations as explained at the bottom of this page, can track the used life span.

Cons: either more batteries are needed or devices will have to go unused while batteries are being recharged, labeling must be maintained.


Meticulous Device Tracking

Yet another step further in tracking the batteries. Not only are the batteries assigned to a particular device, where they were in the device is recorded so they can be in a different position each time.

In devices where batteries are in parallel, this level of tracking gains nothing because their particular location doesn't impact anything. That is, the tracking that is important is already being done.

In devices where batteries are in series (most devices, easily noted by the fact that the batteries face opposite directions or are directly in line with each other), this level of tracking can squeeze even more 'life' from the batteries involved.

To do this, each bay in the device must be noted in some way, either by being labeled or recorded with the battery order information.

Examples: Bay1, Bay2, Bay3. In the TV remote, with the IR lens pointing away, the battery compartment is to me and the buttons down - LeftBay and RightBay. Flashlight takes the batteries positive first in a single bay, so notation will be FirstIn, SecondIn.

Each battery must also be labeled within their own group.

Examples: A1-A, A1-B, A2-A, A2-B, C1-A, C1-B, C1-C.

Then, in the records, track where each battery is used. How in particular depends on how thorough the tracking is wanted to be. For a two battery device, keeping a tally (or count) is sufficient since the number of uses in one position or the other must never be more than one apart. In a multi-battery device, a tally can be used or note on their exact position during each usage - again making sure their use in a particular position is kept within one of use in any other position. This can easily be done by always using the batteries in order (ABC, BCA, CAB) and thus the tally can just track which battery was in a particular bay (A in one means B in two and C in three, while C in one means A in two and B in three).

Pros: the odds of any 'Battery Combat' are about as small as they can get and thus the batteries will likely see close to their best life span, built in tracking of used life span.

Cons: paperwork (or computer), time, labeling maintenance


----- Tracking Used Life Span

In each of the tracking methods (for rechargeable batteries), there is mention of tracking the used life span of the batteries - either in pros or cons. The life span of a battery is a measure of how long it is still useful.

Primary Batteries - These have only one charge and that is the total of their life span, once depleted they are dead and can be sent to recycling (usually taken to a metal yard or battery specialty shop).

Rechargeable Batteries - These can be recharged over and over. Their life span is how many times they can be recharged before no longer holding enough of a charge to be viable. Often times, the manufacturer reports a higher life span than a typical user will allow a rechargeable battery - this can be due maintenance of the battery or conditions the batteries are used or stored in, but can also be due to a difference in what the manufacturer considers to be a dead battery compared to what a particular user considers to be a dead battery.



----- Battery Combat

If the title of this section conjures images of gladiatorial combat or sci-fi blaster fights - good.

In theory, batteries work together as a team to make the device work. In parallel they all contribute a little work and thus make the job easier on each other. In series, they all work hard to complete a job they couldn't do on their own.

But in reality, even batteries that are the 'best of friends' fight just a little.


Here are some terms that will help understanding the fights below:

Series: Typically one behind the other or in a bay based compartment where batteries are inserted in different facings. If one battery is missing, the device can't work. Voltage of the batteries is totaled, capacity (run time) remains constant.

Parallel: The batteries are beside each other and facing the same direction. If one battery is missing, the device can still work. Capacity (run time) of the batteries is totaled, voltage remains constant.

Charge: The amount of power stored in the battery.

Depleted: When the charge gets too low to be sufficient for any device.

Dead: For a primary, this is just a depleted battery. For a rechargeable, this is a battery that has been recharged so many times that it can no longer fit a sufficient charge to be useful.

Power Flow: While thought of as going from '+' (positive) to '-' (negative), it actually goes from '-' to '+'. With that in mind, a bad battery in the negative position of a series is more harmful than at the positive. It doesn't matter where it is when it comes to parallel - just that it is in the group.

Bad Battery: A dead or just depleted battery among good batteries.

Backwards Charging: When a battery gets charged backwards. This is devastating to the battery.


Here are many of the ways they fight:



This happens with fresh batteries or ones that have been used together properly for some time. Like a group of friends that rough house a little when they hang out together. Doesn't usually cause any harm, but sometimes (due to manufacturer defect or spending time away from the group) one takes it the wrong way and the real fighting starts. With batteries, horseplay can't be avoided and usually has little impact on performance.


The Series Deceiver

A bad battery gets paired up with one or more batteries that have seen less use. The nearly bad battery is quickly depleted and the device stops working early - because the total voltage dropped too low. The user believes that the batteries are dead and tosses them - but if a battery checker is used, the good batteries still have charge left. If the batteries are left in the device after a bit of use, they may also start fighting with their charge level - see the next two fights.


Series Charge Duel

When two batteries are in series and one is bad, it will start draining the other battery (particular if it is the battery in the negative position) and will actually start charging itself off the other battery, damaging both batteries. With rechargeable batteries, this shortens their life span, while in primary batteries there is the potential for more destructive results since primaries can't handle being recharged.


Series Charge Beating

On the other end of the scale, there are plenty of batteries involved and one is bad. When it starts draining and injuring the other batteries, they actually gang up on it and damage it more - if it is already nearing death, this could potentially outright kill it. With so many, this could lead to a chain reaction that further injures the other batteries and could potentially kill them as well.


Parallel Inequality

With the group working side by side, the bad battery drains quicker (either due to starting with less charge than the others or having less capacity). When the bad battery gets too weak, the others just take on the work it was doing. This is not usually a problem right away, particularly if the others don't have much more charge... but if they have a fair amount more charge then that can start backwards charging the bad battery, causing it damage and potentially leading to an early demise.


Parallel Group Deception

When a group of batteries are being used and most of them are bad, they become drained quickly and leave all the work to the few or even lone good battery. Typically, this just drains the good batteries fairly quickly. With primaries, this can cause problems such as over-draining alkaline batteries (potentially resulting in leaks) or overheating the batteries supplying the bulk of the power, either way it looks like something was wrong with all the batteries or the device. Rechargeable batteries in this situation could be mistaken as approaching end of life (or being defective) because they didn't last as long - this can result in good batteries being disposed of early - though damage will likely be incurred by all batteries involved anyway.


Full on Knock Down Brawl

When the worst happens - either because of defect, short, heat or escalated fighting. Some (or all) of the batteries not only die but also fail, some times catastrophically. Protection circuits prevent most of these from happening, but they can't prevent them all.

With a defect, one battery may have an internal short, chemistry imbalance or something else wrong with it. This is fairly rare in all but the most questionable of brands. The battery fails and no protection circuit can do a thing about it.

External shorts occur within the device or while the battery is in storage. A protection circuit in the device or on the battery can prevent any serious damage from a short.

Excessive heat either occurs from hard use, fast charging, being stored in a particularly hot location or another battery failing and having an exothermic reaction. In the case of hard use or fast charging, protection circuits can prevent any serious damage. As for being stored in a particularly hot location, the only solution is to move the battery to a cooler location. As for being subjected to another batteries' exothermic failure - it is already too late.

Escalated fighting is when the batteries start fighting in one of the other manners but eventually it just gets so bad that batteries start failing.

Here are the battery chemistries used in flashlights we carry and their typical failure results:

Alkaline - chemicals leak out, corroding the device it is in.

Ni-MH - unable to find details of the effects since this occurs so rarely, should be chemical leak.

Lithium - chemicals spray out, larger cells may catch fire.

Unprotected Li-Ion - chemicals spray out, larger cells may catch fire. In some conditions, cells may also pop open.

Protected Li-Ion - battery stops working and might no long be useable.

All chemistries, catastrophic failure - explosion-like rupturing of the battery that sends chemicals and shrapnel flying. Lithium and Li-Ion battery shrapnel may be on fire. This typically occurs when in a fire, damaged, sabotaged or when a regular failure begins to chain-react through a quantity of batteries.