TECHNOLOGY NEWSLETTER No. 4 January 2011
CHARGING OF CALCIUM/CALCIUM BATTERIES The diagnosis, “discharged battery” occurs repeatedly in vehicles with modern calcium/calcium batteries. And it is this phenomenon that Banner deals with in the following “Newsletter”. The modern vehicle “disease”. Throughout the year, it is stop-and-go traffic and short journeys that place the biggest loads on starter batteries in modern vehicles with their large numbers of electrical consumers. As a result, the vehicle energy balance very quickly tips to the disadvantage of the starter battery, i.e. the dynamo generates less power than the vehicle needs. Lasting damage to the battery due to deep discharge is the consequence and this often leads to starting problems in sub-zero, winter temperatures. External charging. If the vehicle is employed regularly for long distances then in most cases the starter battery is recharged efficiently. However, if this possibility is unavailable the charging level of the vehicle battery should be monitored and if necessary recharging undertaken. Battery does not accept recharging. The majority of the standard batteries sold operate with a charging voltage of 14.2-14.4V and sufficient battery voltage (e.g. 12.75V) is frequently identifiable following charging (min. 6 hours). However, after 2-3 weeks claims are presented relating to insufficient charging, or batteries in storage show a rapid voltage reduction (e.g. to <12.50V). Battery technology as the cause. The causes lie in the charging behaviour patterns of modern full calcium batteries, e.g. our Power Bull. As a result of grid technology, following extremely deep discharging (which generally does not occur in
vehicles except when the lights are left on) such batteries require a higher charging voltage. Acid stratification phenomenon. Following a standard vehicle starting procedure, a charge of 14.4V, which is usual in vehicles, is sufficient as starting makes only a limited demand on capacity. However, should deeper discharging occur and recharging take place with, e.g. 14.4V in full calcium batteries an insufficient mixing of the electrolyte is achieved, which in specialist jargon is known by the term “acid stratification”. This involves differing acid concentrations in the battery cells, e.g. 1.20 g/ cm³ in the upper third and 1.28 g/ cm³ in the lower. Acid stratification identification. Open-circuit voltage measurement always shows the battery voltage in terms of the higher acid density (1.28 g/cm³ corresponds with approx. 12.75V). Therefore, one assumes that the battery is sufficiently charged. However, using acid density measurement in such cases it can be determined that in fact the electrolyte density in the upper cell section only amounts to 1.20 g/cm³. Effects of acid stratification. Sufficient acid mixing is frequently restored following battery standing times or use in the vehicle. An acid density of, e.g. 1.24 g/cm³ (approx.1.5V battery voltage) is quickly attained (after 2-3 weeks standing time, or a few days in operation). As a consequence, excessive self-discharge is diagnosed, or starting problems occur in the vehicle due to insufficient charging. External influences enhance this effect. Low temperatures (< 0°C – charge acceptance declines markedly) and short-distance journeys, during which the battery is often subject to a charging deficit (i.e. power output is greater than charging input), exacerbate this effect.
Banner GmbH, A-4021 Linz-Austria, Postfach 777, Banner Strasse 1, Tel. +43/(0)732/38 88-0, Telefax Sales +43/(0)732/38 88-21599, E-mail: office@bannerbatterien.com Author: Günther Lemmerer, Marketing and PR
Special charging programmes help. Most stratified full calcium batteries can be restored to a fully charged condition through the appropriate charging programme. It is important that an increased charging voltage of 15.8-16V is used over a period of around 24 hours. The maximum charging voltage must amount to at least 1/10th of the rated capacity (e.g. 10A for a 100 Ah battery). Moreover, the ambient temperature must amount to a minimum of 15°C in order that optimum conditions for recharging prevail. Recommended charging devices. Banner’s range of accessories includes charging devices capable of recharging deep discharged full calcium batteries. The Accucharger MPL10 and Accucharger Professional devices are recommended for starter batteries with outputs of up to 100 Ah. The individual technical descriptions of these chargers can be downloaded from the Banner website: http://www.bannerbatterien.com/banner/ produkte/batterien/zubehoer/index.php