Battery Self-Discharging; Batteries; Flooded Lead-Acid Batteries; Sealed Absorbed Glass Mat (Agm) Batteries - Bosch PLN-24CH12 Installation And Operation Manual

14 en | Planning information
Large battery banks make up a large thermal mass. Thermal mass means that because they
have so much mass, they will change internal temperature much slower than the surrounding
air temperature. For this reason, the external temperature sensor (see section 6.6 ) should be
attached in thermal contact with the battery. The sensor will then read very close to the actual
internal battery temperature.
4.6

Battery self-discharging

All lead-acid batteries supply about 2.14 V per cell when fully charged. Batteries that are
stored for long periods will eventually lose all their charge. This "leakage" or self-discharge
varies considerably with battery type, age and temperature (batteries self-discharge faster at
higher temperatures). It can range from about 1% to 15% per month. Generally, new AGM
batteries have the lowest, and old industrial (lead-antimony plates) have the highest self-
discharge.
In systems that are continually connected to some type of charging source, like the Bosch
Battery Charger, this is not a problem. However, one of the biggest killers of batteries is
sitting stored in a partly discharged state for a few months, like before commissioning. A
"float" charge should be maintained on the batteries even if they are not used (or, especially
if they are not used). Even most "dry charged" batteries (those sold without electrolyte so
they can be shipped more easily, with acid added later) will deteriorate over time. The
maximum storage life of these batteries is about two to three years.
4.7

Batteries

4.7.1

Flooded lead-acid batteries

Flooded lead-acid batteries have the longest track record in back-up use and are still used in
the majority of back-up systems. They have the longest life and the least cost per capacity. In
order to enjoy these advantages, they require regular maintenance in the form of watering,
equalizing charges and keeping the top and the terminals clean.
4.7.2

Sealed absorbed glass mat (AGM) batteries

AGM batteries are more and more used in back-up systems as their price comes down and as
more systems are getting installed that need to be maintenance free. This makes them ideally
suited for use as battery back-up. Because they are completely sealed they can not be spilled,
do not need periodic watering and emit no corrosive fumes. The electrolyte will not stratify
and no equalization charging is required.
AGM batteries are also well suited to systems that get infrequent use as they typically have
less than a 2% self-discharge rate during transport and storage. They can also be transported
easily and safely by air. They can be mounted on their side or end and are extremely vibration
resistant. AGMs come in most popular battery sizes and are available in large 2 V cells for the
ultimate in low maintenance large system storage in accordance with EN54-4. When first
introduced, because of their high cost, AGMs were mostly used in commercial installations
where maintenance was impossible, or more expensive than the price of the batteries.
180110011Aa | V1.1 | 2011.05 Installation and Operation manual
Battery Charger
Bosch Security Systems B.V.