Battery banter

Despite their universal use across most vehicles, many techs still don’t really understand batteries, but they are a missed opportunity

Published:  04 November, 2019

The vehicle battery has for many years ceased to simply be a chemical storage device. Instead, it has turned into a critical integrated component within the electronics network. It is also increasingly responsible for the total electromotive force in electric vehicles. I will comment on this development later. Despite this, it remains little understood or respected by many techs. I will begin with some interesting technical facts, provided by Yuasa, our battery partners here in the UK.

Many independent battery manufacturers limit the critical internal components to reduce cost, as well as to maximise profit and range application. Typical configurations include smaller cell capacity and increasing the electrolyte strength to artificially meet CCA ratings.
Reducing lead content reduces reliability, specification, and lifecycle. The electrolyte has a direct effect on performance and lifespan. Increasing electrolyte strength to artificially meet capacity specifications will increase internal corrosion.

The end of life is directly affected by the number of start cycles over time, this is the defining feature of 2/3/4/5-year battery construction. The battery begins its decline immediately following manufacture. The initial formatting drives impurities off the plates, as a result the peak CCA performance should be achieved. The peak performance period (lifespan) depends on its warranty specification. The final phase is a rapid decline in output and eventual failure. The correct action is to replace the battery before the final decay period, it often appears to perform normally during this period.

Hands up, who checks batteries at the point of delivery? If they are below 12.4v send them back. Six cells at 2.12v produce a voltage differential of 12.72 fully charged. At 0°C a battery has 66% available capacity. Excessive heat can also have a negative effect on battery performance and accelerate failure and end of life due to plate corrosion, an increased in self discharge, and increased electrolyte loading. A 10°C rise in temperature will increase the self-discharge rate from 0.1v to 0.2v per month.10°C equals a 60-month battery life. 25°C equals a 36-month battery life.

Plate sulphation is normal during battery discharge. When both plates are coated with lead sulphate, or when the plate voltage falls below 12.4v, prompt recharge will displace the lead sulphate. The battery will normally recover and perform normally. However, if allowed to stand it will crystalize and harden.

The death zone of a battery rendering it unrecoverable is SG at 1.04, cell voltage at 1.9v, total battery voltage at 11.3v.
Recovery is marginal from a SG at 1.02, and a battery voltage at 12.3v. Acid stratification accelerates failure and can occur due to cold weather and short drive cycles. The separation of acid has the effect of increasing the open circuit voltage while reducing the CCA performance. Superficial testing may show a healthy fully charged battery.

Conventional flooded batteries should be maintained within 5% of its fully charged state if premature cell failure is to be avoided. Meanwhile, AGM batteries can operate normally with a 50% cycle rate.

24v systems and vehicles using two batteries require that both the CCA and OCV be in balance. This is also a critical factor with electric vehicles using lithium batteries, as cell differential will lead to differential cell charge and overheating.  
Stop/Start vehicles will be fitted with either an enhanced flooded (EFB) or absorbent glass matt (AGM) batteries. Key differences with EFB & AGM are:

  •  Extended life over conventional flooded batteries
  •  Improved temperature resilience
  •  Improved charging and cycle times
  •  Additional internal plate components
  •  Leak resistant to 55°C
  •  AGM performance improvements,
  •  Four-times extended cycle times
  •  Sealed plates at 1bar preventing loss of active material
  •  Very low internal resistance
  •  High energy yield
  •  Electrolyte absorbed in the glass matt; 100% leak free


Hopefully by now most repair shops have a conductance tool. It applies a small load, current at approximately 1-1.5 amps. The load is proportional to the correct battery specification, provided the correct battery specification has been entered. The internal resistance and state of charge is checked against an algorithm providing a linear comparison with a load discharge test.

We can also use a scope with a hall effect current clamp. This will provide real time voltage drop and current draw across the whole cranking spectrum, a healthy battery at ambient temperature will return at least 100 amps more than the CCA rating during the initial starter ring gear engagement.

Pico Diagnostics also provides a battery test facility with very similar results to a conductance test.
It is also worth a word about correct battery support. While downloading software or conducting diagnostics, voltage drop over networks is critical and may lead to functional failure.

I have been very outspoken over the current euphoria with plug-in EVs. Because of this, let me make this a technical critique and not just personal or political.

The current known lithium reserves are estimated at around 350 million tons. Most of it is politically accessible – Australia has a lot of it. The demands can be simply split into three equal parts, batteries, lubricants and ceramics, and propulsion and weapons technology.

A 65-watt lithium battery requires 10kg of lithium. If current predictions are correct with 500 million EVs by 2040, the global resources will only last 18 years. This does not factor in the economic expansion from emerging markets like China, India, and South America. It also does not factor in the much bigger battery demands for 4x4, small commercial vans and high-performance vehicles.
Lithium recovery and extraction from exhausted batteries only offers 20% at best.  Disposal will be an environmental problem as lithium is essentially a brine, with the fourth lightest mass in the periodic tables.

 Charging is without doubt one of the most contentious subjects. Some manufacturers are claiming a very short stop over, with high current charging strategies. Other considerations include the poor business model for charging stations, lots of vehicles stationary over long periods of time, together with the power network required to carry the load. Also, what about the operating overheads for charging ports?

For me the biggest issue is the primary energy source.  Coal, oil, gas, biomass, nuclear and renewables are all currently used to produce electricity. Given production processes, transportation, energy loss in the conversion processes it doesn’t look so clean anymore.

The current marketing reminds me of the video format wars; Betamax versus VHS, with V2000 also angling for market share. In the same way, we have hybrids and plug-in EVs all competing, except the goal is the myth of clean transportation for the future. My opinion for future personal vehicle development lies with the hydrogen cell.

Back in our home video format war comparison, while the tape formats were fighting it out in the 1980s, the higher-picture quality benefits of laserdisc and uncompressed audio, decades before Blu-Ray, were ignored by consumers in the UK in favour of home taping convenience. There were a few markets though, notably Hong Kong, where laserdisc was the dominant home video format. In an interesting twist, China has announced an ambitious programme for hydrogen powered vehicles. Europe on the other hand rarely gives even lip service to this obvious development. I suspect the problem with new clean vehicle technology is how governments will apply taxation in place of gasoline and diesel.

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