AN150

Using batteries in AEA Technology Equipment

Written by Bill Ashley for

AEA Technology Inc.

Abstract:

AEA Technology’s equipment operates from either wall power packs or 8 AA batteries.  This paper discusses the use of batteries in AEA Technology equipment and how to squeeze the most from a set of batteries.

General

Battery types:  

Since AEA Technology equipment uses 8 standard size AA batteries, there are multiple options available in the choice of batteries: Alkaline, NiMH, or NiCd.  Sealed Lead Acid ( SLA ) or Starved Gel (SG) batteries with a 12-14 volt output are usable as an external power source.

Alkaline Batteries:

A set of alkaline batteries will run longer than NiCd types (on a single charge), but must be replaced after discharging.   Alkaline batteries cost the most over the long run, but make a good stop gap solution when you are on the road and have forgotten to recharge your NiMH or NiCd set.  Most convenience stores stock alkaline cells, plus newly purchased NiCd batteries may not have a full charge.

Using alkaline batteries in AEA equipment may result in a gradual display contrast shift caused by heat buildup in the unit.  If alkaline cells are used on a consistent basis, try these solutions:

1.    1. Set the “Battery Saver” time out to reduce power consumption when not in use.

2.    2. Preset the contrast to a somewhat light setting, this will give a longer time before the display darkens to a readjustment level.

3.    3. Reduce the backlight intensity to a lower level.  The backlight’s heat can be useful to operate in colder temperatures, but it can darken contrast at room temperature and warmer environments.

4.    4.  Use NiMH batteries instead.  While NiMH batteries may have less capacity, they have a lower and very flat resistance (approx ½ Ohm), so the power loss in the batteries improves significantly.  With NiMH batteries, the total power in the case is less than 4W for the entire battery life. NiMH batteries “hit the wall” rather suddenly compared with alkalines. The flatter resistance curve may even allow the 2000maHr NiMH batteries to outlast the 3500maHr alkaline batteries.  

NiMH Batteries:

NiMH batteries offer the most advantages compared to NiCd or Alkaline cells..  When properly recharged, they last for over 500 cycles, thus the cost over the long haul is  very inexpensive.  Unlike NiCd cells, they do not lose capacity (“burn time”) when recharged early, in fact they last longer when recharged prior to full discharge.  Lastly, NiMH cells do not suffer from the infamous “memory” problems that so often reduces NiCd charge capacity. 

One drawback of NiMH: you must use a recharger specifically designed for NiMH cells or the batteries will suffer damage long before reaching the 500 recharge cycles.  Do not attempt to recharge NiMH unless their temperature lies between 10 to 45^o45^o C (50 to 112^o F).).  Do not attempt to recharge batteries that show signs of out gassing (gunky residue near the anode or positive end).

The second NiMH battery drawback: They should not be fully discharged.  When a NiMH cell fully discharges, cell voltage reversal occurs, and continued discharging eventually causes out gassing.  Higher quality rechargers will revive these cells (that have not yet out gassed) by starting off with a low precharge current.  Cheap rechargers may damage these cells.  Batteries that show signs of out gassing should be replaced.  Most battery authorities recommend replacing all the batteries as a set, many rechargers operate best when all the cells are at a similar stage in their recharging life cycle.

NiCd Batteries:

NiCd batteries are less popular now that NiMH batteries are available.  NiCd cells are rechargeable in a NiMH charger, but not visa versa.  NiCd cell’s  lifetimes are shorter and they require a full discharge prior to recharging or a loss of capacity occurs (also known as acquiring a memory).).  Do not over charge, overcharging NiCd cells results in out gassing.  Allow NiCd cells to cool off prior to recharging. 

Sealed Lead Acid ( SLA ) or Starved Gel (SG):

These types of batteries will not fit into the internal compartment, so an external power cord will need to be purchased or custom made for your application. SLA batteries (or car batteries) are advantageous when operating in a high magnetic field or when you are powering off of your automobile.  You must use a SLA recharger for this battery.  The required voltage for external batteries, SLA or SG type on AEA Technology units is 12 to 14 volts.

Battery Operating Tips:  

Reduce backlight Intensity.  The brighter the backlight, the more power is consumed.  Use the lowest intensity setting that works for the existing lighting conditions.  The backlight may be helpful in maintaining the LCD’s contrast in temperatures below 0^o C (32^o F) so it becomes difficult to reduce power at those temperatures.

Use the backlight timer.  Set the timer to 10 or 20 sweeps, the power consumption drops when the timer turns off the backlight. Pressing Enter (or any other key) activates the backlight for another interval. 

Turn the battery saver on.  The battery saver turns the unit off after approximately 5 minutes of inactivity.  If you press any key prior to auto shutdown, the timer will reset.

NOTE:  The battery saver’s auto shut down saves all the instrument settings at the time of shut down.  Powering back on takes about 5 seconds of recalibration and the instrument will return to the settings at the time of shut down.

Use NiMH batteries for cold weather operations.  As temperatures drops below 0^o C (32^o F), continuing the LCD’s operation will determine how long the instrument will be useable. NiMH batteries can delivery more power at lower temperatures than Alkaline batteries.

Remove Batteries prior to long period of inactivity. This will prevent the mess and contact corrosion caused from leaking batteries.

Always use a recharger that matches the battery.  Do not attempt to recharge alkaline cells.

Typical Current Draw:

Typical Operating Times by Battery Type:

 Conclusion:

If your operating conditions require that your AEA Technology instrument be operated on battery power, AEA Technology recommends for best performance and economy using the battery types in the following order: