8 Myths and Facts about Lead Acid Batteries


Myth: Lead acid batteries can have a memory effect so you should always discharge them completely before recharging.

Fact: Lead acid battery design and chemistry does not support any type of memory effect. In fact, if you fail to regularly recharge a lead acid battery that has even been partially discharged; it will start to form sulphation crystals, and you will permanently lose capacity in the battery.

Myth: The worst thing you can do is overcharge a lead acid battery.

Fact: The worst thing you can do is under-charge a lead acid battery. Regularly under-charging a battery will result in sulfation with permanent loss of capacity and plate corrosion rates upwards of 25x normal. Overcharging a battery breaks down any sulfation, but can cause plate corrosion rates to increase up to 3x normal. With flooded/wet batteries you can always add water. One concern is overcharging AGM batteries, which already have very little water reserve, and so there is risk of dry-out. However, most chargers sold today are “smart” chargers and will shut off after the battery is fully charged.

Myth: Any charger should work perfectly okay with any type of lead acid battery.

Fact: There are many different technologies used in lead acid batteries. For example; many automotive batteries are a flooded/wet design for engine starting, but not designed for deep cycle use. You can use automotive chargers for these which are either trickle charge or taper charge and normally have higher output ripple current. You would not want to use an automotive charger for a deep cycle AGM or GEL battery because the higher ripple current would cause water loss and dry-out and a trickle or taper charger may not fully recharge a deep cycle battery.

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Storage and Installation

Myth: Never store a battery on a concrete floor because it will suck the energy out.

Fact: There was truth to that 75 years ago when batteries were built in hard-rubber cases because acid would weep through the case into the concrete creating a discharge path. Nowadays modern plastics are impervious to acid so there is no risk of this happening.

Myth: It is okay to store lead acid batteries anywhere inside or outside.

Fact: It is good to store lead acid batteries in cool places because the self-discharge is lower but be careful not to freeze the battery. Do not store lead acid batteries in hot areas because the heat will cause high self-discharge and will shorten the life. Do not store lead acid batteries outside because the UV light will damage the plastic case and moisture will corrode the terminals.

Myth: Battery operating temperatures are not so critical as long as lead acid batteries are not too hot.

Fact: Individual cell temperatures within a battery bank must be kept within 3°C/5.4°F of each other because the charge acceptance for lead acid batteries varies considerably with temperature. If the ambient temperature in the battery room varies by more than +/- 10°C/18°F then you should be using battery temperature compensation to automatically vary the charge voltage.


Myth: Maintenance free batteries never require maintenance.

Truth: There is no such thing as a maintenance-free battery, and IEEE recommends this type of battery should be called valve-regulated lead-acid or VRLA to avoid any confusion. Even so-called maintenance-free automotive batteries should be checked/tested to ensure they do not let you down, and the terminals should be cleaned to ensure a good connection. Higher voltage stationary banks also need check-ups and cleaning; furthermore, they need conductance testing to determine the condition of the plates and discharge capacity testing to verify if they are performing well or need replacement.

Myth: Any type of grease is okay to protect battery terminals.

Fact: There are many different cleaning and protecting products in the industry. Some of these contain harsh chemicals that may actually damage the plastic case, connections, or terminal seals. One common industry product is NO-OX, which is a petroleum-based product with corrosive ingredients that keep the terminals clean by removing the oxide layer.  This is usually okay to use on automotive or less expensive batteries, but when it comes to advanced technology batteries, it can often become a problem, not to mention that NO-OX is also toxic and very flammable.  Electrical grade silicone grease is a much safer alternative to use on all lead acid batteries because silicone is very non-reactive, so it does not damage plastic or rubber terminal seals and is also non-toxic.

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