BU-803c: Loss of Electrolyte

Discover what you can do to keep the integrity of your battery

The loss of electrolyte in a flooded lead acid battery occurs through gassing as hydrogen escapes during charging and discharging. Venting causes the electrolyte to become more concentrated, and the balance must be restored by adding clean water. Do not add electrolyte as this upsets the specific gravity and shortens battery life by promoting corrosion.

Loss of electrolyte in sealed lead acid batteries is a recurring problem that is often caused by overcharging. Careful adjustment of charging and float voltages, as well as operating at moderate temperatures, reduces this failure. In flooded batteries, lost water can be replenished by refilling, but in sealed batteries water loss can lead to dry-out and decline of performance. Replenishing lost liquid in VRLA batteries by adding water has been tried with limited success. Although the lost capacity can often be regained with a catalyst, tampering with the cells turns the stack into a high-maintenance project that needs constant supervision.

Nickel-based batteries can lose electrolyte through repeated venting due to excessive pressure during extreme charge or discharge, as well as from overcharge. Inaccurate full-charge detection and elevated trickle charge can lead to overcharge. This is especially true with aging and faded packs. After recurring venting, the spring-loaded seal of the cells may not seal properly again and the deposit of white powder around the seal opening is evidence of leakage. Sloppy manufacturing can also lead to electrolyte loss. Dry-up conditions result in a “soft” cell, a defect that cannot be corrected. On charge, the voltage of a “dry” cell goes high because the battery has no clamping ability. It is no longer chemically active and does not draw current.

A properly designed and correctly charged lithium-ion cell should not generate gases, nor should it lose electrolyte through venting. In spite of what advocates say, lithium-based cells can build up an internal pressure under certain conditions, and a bloated pouch cell is proof of this. (See BU-301a: Types of Battery Cells) Some cells include an electrical switch that opens if the cell pressure reaches a critical level. Others feature a membrane that releases gases. Many of these safety features are one way only, meaning that once activated, the cell becomes inoperable. This is done for safety reasons. (See BU-304a: Safety Concerns with Li-ion.)

Why does a battery gas?

When overcharged, a battery gases, splitting water in the electrolyte into hydrogen and oxygen. A battery becomes a “water-splitting device” by electrolysis. A parallel is the fuel cell but it does the opposite way, turning oxygen and hydrogen into electricity by producing water. Energy is needed to produce oxygen and hydrogen and the battery gets the energy through overcharging.

Last updated 2016-03-07

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Comments (8)

On August 19, 2015 at 9:11pm
abdullahshafudin wrote:

Can loss of electrolyte lead to battery explosion

On August 19, 2015 at 10:08pm
abdullahshafudin wrote:

Can dark current leading to electrolyte loss.?

Example : the usage of alarm system that have ultrasonic sensor to detect any movement in a car.

On September 17, 2015 at 11:37pm
edward wrote:

Lead acid lost wasn’t directly related to accessories attached to the car… you are working in car manufacturer don’t you… you should know better..

On September 18, 2015 at 2:11am
abdullahshafudin wrote:

Dear Edward,

How do you know I am in car manufacturing?

Currently I had an issue with maintenance free battery explode after one year. From my analysis, I found the electrolyte loss below than the fusion bridge that resulting arcing inside battery and ignite the hydrogen gas thus explode the battery.

Now I am stuck with how can the electrolyte loss too much ( far below min level).

hope you can share analysis activity or countermeasure if you have any experience facing this problem.

On September 7, 2016 at 11:54am
Phil wrote:

I just received, by courier, a new Banner (expensive!) deep-cycle lead-acid battery for RV use.  It seems it had been tipped on its side during transit, so one cell has lost all its acid. (it was shipped with no hazardous goods markings at all, by the way :(
Obviously I will ask the supplier to replace it, but I wanted it in a hurry…
Just wondering if I attempt to fix it:  how long it can stay in this condition (one dry cell) before it is permanently damaged? Is it feasible to replace the acid in just one cell - how closely do I need to match the SG of the remaining cells? 
Thanks for any experience anyone may have.

On September 16, 2016 at 9:02pm
Conundrum wrote:

Hi, is there a fix for a battery where the resting voltage is 10.74V? This is looking very much like one cell (the end one on the positive end) is bad because it appears the electrolyte was replaced or supplemented with water (fortunately deionized). Any ideas other than “give up and buy another one”? Its got a very high internal resistance but my SG measurements of the other 5 cells look good.
I tried putting in electrolyte from a scrap battery (50% SOC) and that helped a but but not sure what else to try. thanks!

On November 24, 2016 at 6:03pm
Bart Boeckmann wrote:


I have a forklift I bought from the General Mills factory in northern ohio.

I have made the mistake of filling up cells before charging several times.

I am using a hydrometer with numbers not floating pellets.

It appears now that so much acid is gone from adding distilled water over time that adding the diluted acid from the auto parts store will never get me there.

I assuming that I either need to get out all the water in each cell then add the auto parts store acid or is it possible to add the full concentrated acid?

I am aware of the dangers of the concentrated acid, full face mask, rubber apron, respirator, safety glasses…ect…no problem.

However does adding the full concentrate acid even work???

Does draining each cell and refilling destroy it?

48v crown forklift.

Charger set to slowest rate.

Charger also came from general mills.

On December 13, 2016 at 4:29am
Dan wrote:

Bart Boeckmann, To restore your batteries do the following,
Put pack on charge with highest setting to agitate electrolyte,

After 1 hour check batteries have SG of 1220 or above, if below 1220 remove electrolyte and add battery acid 33% as much as possible, can use SG meter to suck out and put in container, after another hour check SG and repeat as required,

Charge batteries with at-least their full AH capacity i.e 700Ah = 14Hrs @50A do not let cells go above 40 degrees C reduce charge current to avoid excessive heat or gassing,

Allow cells to cool and remove from container ream bridges off as required to remove.

Find a container that will hold 2x the capacity of electrolyte i.e. a 10L plastic bucket, empty all electrolyte from cell into bucket, Mix in 98% sulphuric to raise SG to 1270/1275 as required if you go to high just add distilled water to lower SG,

Allow electrolyte to settle lead to bottom and refill cell with adjusted electrolyte to top fill mark, do this for all cells and re install to truck.

I have done this on many used flooded traction cells where actual electrolyte levels are weak or unknown to to spillages and misuse etc. BE very careful adding 98% sulphuric to water/weak electrolyte is exothermic and will cause temp rise do it gradually. I did this to a spilled pack that had been refilled with water and pack tested to 98% of rating.