Battery Characteristics & Fault Diagnosis

Yuasa lead-acid batteries are built to the highest standards. They are manufactured, in most cases to correspond with or exceed the vehicle manufacturer’s requirements and specifications.

Nevertheless, it should be clearly understood that wet (filled) lead acid battery is “a live” product. Whether it is in storage or in service, it has a finite life. All batteries once filled will slowly self discharge. The higher the storage temperature and humidity of the storage area, the greater the rate of self discharge.

To ensure the batteries are not allowed to discharge to the point where they are damaged (sulphated) or so incapable of giving designed service life, regular checks of the recharge date label on the back of the battery, and voltage checks of batteries with less than 4 month remaining should be made. It is important to ensure good turn around of stock, first in, first out, especially with slow running stock of low volume lines. Batteries with a voltage of 12.35V or below should be recharged immediately. Recharging must not be effected by means of a rapid charger due to the inefficiencies when attempting to recharge a partially sulphated battery which leads to excessive gassing and damage to the active material grid bonds within the battery, which are critical to ensure battery life.

Ideally use a recharge rate as stated in “recommended recharge rate and period” according to battery type and catalogue instructions. At the end of discharge, all cells should be gassing freely. It is clearly recommended that batteries are left to stand for a minimum of 3 hours after charging to ensure any gases trapped in the upper battery casings are allowed to diffuse into the atmosphere. If a battery has been recharged, the recharge date on the back label should be updated by 6 months after second recharge date by physically notching the label. (Note a maximum of two recharges are allowed prior to sale, and product should not be sold a maximum of 9months after the expiry of first recommended recharge date).

Battery Problems

Non Manufacturing Defects

Physical Damage
If the battery is stored, handled or fitted incorrectly, if the connectors leads are hammered onto terminals, leads are not correctly fastened, the battery will have damage to casing and/or terminals. This is not a manufacturing fault.
* Note all batteries picked and dispatched from Yuasa’s UK warehouse are photographed prior to dispatch to ensure our shipping quality targets are met.

If a battery is allowed to stand in a discharged state either on or off a vehicle for a period of time, a chemical reaction takes place which will permanently impair the performance and life of the battery, this process is called “sulphation”.

Sulphation can be seen as a fine white/grey coating on the positive plate and a non metallic luster on the negative plate. In most cases this signifies the battery as not serviceable. Attempts to recharge batteries left in a discharged state, even at very low charge rates will lead to damage to the grid and active material interfaces and also sulphate deposits can be formed within the separators which produce dendritic shorts.

The damage can occur in storage or if the battery is installed on the vehicle (or equipment) that is not used for a period of time, for example tractor, motorcycle, boat, airport vehicle even a car or truck that is stored with the battery connected can still damage the battery. This is because there is a permanent drain on the battery from items such as the alarm, clock, lights, etc left on which drag the battery down to its lowest possible state of charge. The longer the period left, the greater the sulphation builds up on the plates.

The sulphation hinders the efficiency of the electrochemical reactions within the battery between the active material of the plates and the acid. This is not a manufacturing fault.

Wear and Tear
As the battery is cycled, i.e. charged and discharged, the active materials within the battery plates are in motion in order to release the electricity stored by the battery. Every time the battery is charged and discharged a small amount of active material is permanently lost from the plates.

As the ultimate battery life is determined by many factors, such as temperature, battery operating state of charge, duty cycle, etc it is impossible to stipulate a minimum/maximum life expectancy in the field. This process of normal ageing will eventually cause the battery to lose capacity and it will come to the point where the battery can no longer start the vehicle or equipment. Modern fuel injected cars start much more quickly, typically using a surface discharge off the battery plates, hence the unexpected failure of the battery is more often than not seen when the battery is first put under stress, for example on a cold morning, or after a weekend stand. This is not a manufacturing fault.

It is always best to take the opportunity of free battery checks prior to the onset of cold weather or long airport parking periods.

Deep Cycling
As above, every time a battery is charge and discharge cycled a small amount of material is lost. If a battery is subjected to deep discharging (greater than 35%) and rapid charging the process is accelerated. Additionally if the recharge does not recover the discharge cycle in full, the battery will exhibit loss of performance and concentration of the acid can occur between plates which can lead to corrosion and loss of performance.

Even after recharging, the voltage will be low (under 12.4V) but if the cells acid gravities are checked they will generally be even across the battery. This is not a manufacturing fault.

If the alternator regulator is not set properly, or alternator voltage control circuit fails, then the battery can be subjected to an excessive charge.

If left unchecked the battery will overheat and will start to evaporate the electrolyte. The overcharging will accelerate the break up of the active material and grids and the battery will lose performance. Examination of the battery will typically show low acid level and usually a black coating on filler plugs and a strong smell. It is recommended that the alternator charging voltage is checked by a mechanic. This is not a manufacturing fault.

False Claim
In order to minimise fraudulent battery claims each Yuasa battery has its own individual unique number found on the back label of the battery. It is recommended that this number is recorded on the proof or purchase at point of sale, to enable a double cross check to be made during the claim procedure. The label has been made tamperproof.

Incorrect Application
The batteries recommended within this Yuasa application list are equal to or above the original equipment specification. Fitting a smaller or less powerful battery will result in a shorter service life and earlier failure. The failure will normally be seen as deep cycling/premature wear and tear.

It should be noted that a vehicle fitted originally by manufacturer with an AGM battery should be replaced only with an AGM battery. Likewise, a vehicle originally fitted with an EFB battery should only be replaced by and EFB or AGM battery.
This is not a manufacturing fault.

Undercharging occurs if the battery is not receiving enough charge to return it to a full state of charge, this will slowly cause sulphation. This fault can occur if the car is being used only occasionally for short journeys, or for Start-Stop urban motoring. Undercharging will occur if alternator voltage is low (13.6-13.8volts), the alternator belt is loose or battery cables are worn and causing high resistance – If in doubt seek advice from an auto electrician.

Battery Problems

Manufacturing Faults

Due to the high demands of the OEM market and the technical and manufacturing standards of Yuasa batteries, the rate of genuine manufacturing faults is negligible.

Short Circuit/dead cell
Typically seen in a battery within 12 months service life. One cell will show a dramatically lower acid specific gravity reading than the others. The problem cell will usually boil visibly under a high discharge, all other remaining cells will show a good specific gravity reading of 1.26 or above. Short Circuit/dead cells seen in later life are usually associated with the recovery of a sulphated/overdischarged battery. It is possible to see variable acid specific gravities between cells if sulphation is the route cause.

Internal Break
The battery will have good specific gravity but no voltage reading. Check for any physical damage which may have caused an internal break.


Providing the correct battery, in the right condition has been used in the right application, the number of battery problems encountered will be minimal. All batteries have a finite life (otherwise there would not be an aftermarket battery business), the life is governed by the conditions under which the battery operates. Battery failures caused by sulphation, wear and tear, deep cycling and physical damage are not manufacturing defects and are not covered by the Yuasa guarantee. Under normal operating conditions, a battery cannot become discharged on its own. The reason can normally be traced back to:

  • Malfunctioning alternator, regulator, or starter motor
  • Slipping (incorrectly adjusted alternator charging belt)
  • Electrical fault e.g. interior boot/glove box lighting, ECU/sensor interface issues where vehicle does not go into “Sleep” after parking for more than 5 minutes, wiper 
motor fault
  • Excessive use of electrical consumers, – air conditioning, stereo (incorrectly fitted direct to the battery) etc
  • Long standing time without recharge
  • Vehicle lighting and/or hazard flasher left on

If a battery is consistently used/left in a discharged condition, it will eventually get to a state, where it cannot be recovered by a controlled recharge. This is classified as deep discharge/undercharging and it is NOT a manufacturing fault. If a battery is continuously deeply discharged by stop/start motoring and heavy usage of vehicle consumer device and then not adequately recharged, it will lose its performance relatively quickly. This is called deep cycling/wear and tear and is not a manufacturing fault. Alternative battery technology, charging and handling solutions need to found for these applications.

CCA Testing using Digital Conductance Battery Testers.
There are many different types of hand held digital conductance tester on the market. They generally give a good indication 
of problems but the following points should always be taken 
into account.

  • They are not a reliable method of checking the fully 
developed cold cranking performance of a NEW Battery, partially due to some of the health reading algorithms used. They are designed for the evaluation of testing of faulty or used batteries.
  • Different makes of tester, and even different models can give different results.
  • Different battery manufacturing design techniques can significantly effect the reading on one digital conductance tester as common algorithms have to be used. For example, batteries designed with more durability in mind tend to carry more material and higher density, this is usually reflected in a lower initial voltage, but longer discharge times. Digital testers can only determine realistically the initial internal resistance of the battery at the particular state of battery, not how much material is available. This can cause considerable difference between the indicated CCA data and the real CCA data obtained in a laboratory under real current loads to the appropriate battery standard specified.
  • CCA readings can be measured according to a number of international standard SAE, EN, DIN or IEC, Within the EN 50342: 2006 standard two requirements are listed: EN1 & EN2. Typical Conductance testers are calibrated toward EN2 standard, however the ETN numbering system makes it difficult for the normal man to understand which standard is being used on the battery.
  • The condition of battery cables and terminal connections can influence the reading on the hand held tester.
  • A battery that is 2-3 years old may still be serviceable for a number of years to come, but because of “wear and tear” may only give a 75% health reading. Conversely a deep discharged battery (or partial internal break) can give a good reading on cca scale, but on actual high rate or capacity check the battery is in a poor condition. NB Testing in conjunction with a load tester should be considered where deep discharge may be failure option.

Overall the digital conductance tester gives the best indications of evaluating suspect or used batteries in the market today, but considerations should be made of above points whilst operating the meters.