Many Gizmo Engineering products are offered with choice of battery or plug-in versions. Here are some thoughts on choice of power.

Battery versus Plug-in Power
Plugs are, by design, meant to be easily unplugged. With an alarm system however, that compromises their reliability because they can become unplugged so many ways:

  • A annoyed operator can simply yank the plug out to silence the alarm, and forget to plug it back in.
  • Sometimes an outlet is "borrowed for some emergency".
  • Cords can get tripped on, or snagged, and come unplugged inadvertently.
  • The circuit breaker for a branch power line can trip and not be noticed if nothing important is on that line.
  • Power outages are a time when alarms are most needed because thats when pumps stop pumping and normal protections may not be there. Even when power returns, many systems need to be reset before operating again. This is the time when fuses often tend to blow because of the abrupt startup surge.
  • Plug connections can oxidize in corrosive enviroments.

Battery power by comparison, is uninterruptible, and the alarm can only fail if someone willfully disconnects the battery. The downside is of course that batteries eventually discharge. Now though, battery technology has advanced to the point where some batteries can last for 20 years.

Low Battery
On our products with a circuit board, there is usually a feature that reduces the output after 60 minutes of alarming. After this time, the buzzer and LED will activate for only 5 seconds every 30 seconds to reduce power consumption. This is enough alarming to get someone's attention. Depending on the type of LED this allows the unit to run for weeks. When the battery voltage runs low, there is a low-battery alert that has a distinct stacatto pattern. Again, 5 seconds out of every 30 seconds is enough to get attention.
Even on our products without the low battery alert, the audio buzzer volume gets quieter as the battery voltage drops. Operators will have no trouble recognizing this and because operators like the Drum Alarms, they will want them to keep working because they make their life easier.

Choice of Battery?
We offer two types of Lithium battery chemistries: Lithium manganese dioxide, and Lithium Thionyl Chloride. The battery is in two ways: by internal discharge, and use.

Either will provide ~1200 mA-hours of capacity, which translates to around 50 hours of alarm activity. (typically a few years)

In cases where the alarm is rarely activated, then the internal-discharge determines the life. The discharge rate of Lithium Manganese Dioxide (Ultralife) batteries is approximately 2% per year which means that after 10 year the self discharge will reduce the charge to 80% of a new battery. (80% is the common industry-accepted threshold to say when a battery is spent) Lithium Thionyl Chrloide batteries have a discharge rate of approximately only 1% which means the battery can last 20 years.

Lithium Thionyl Chloride batteries have the longest standby life, however they are higher in price. So if you have a tank that will sit undisturbed for years then this is the best choice of battery. If you have a product that will be alarming daily, or weekly then a Lithium Manganese Dioxide battery will last just as long for less cost.



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Cross section view of a Lithium Thionyl Chroride battery
Ultralife U9VL-J
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20 Year Battery Lithium Thionyl Chloride Battery


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