Bosch PLN‑24CH12 Spécifications télécharger pdf (Page 12)

12 en | Planning information Battery Charger

180110011Aa | V1.1 | 2011.05 Installation and Operation manual Bosch Security Systems B.V.

4.3 Effects of discharge rate on battery capacity and battery life

The rate at which a battery is discharged also has a profound effect on its capacity and life.

Figure 4.1 shows the effect of discharge rate on battery capacity. The figure shows that a

battery -when discharged at a low rate- will be able to deliver a higher capacity than a battery

discharged at a high rate.

Figure 4.1 Capacity vs discharge rate

4.4 Depth of discharge (DOD)

A battery "cycle" is one complete discharge and recharge cycle. It is usually considered to be

discharging from 100% to 20%, and then back to 100%. However, there are often ratings for

other depth of discharge cycles, the most common ones are 10%, 20%, and 50%.

Battery life is directly related to how deep the battery is cycled each time. If a battery is

discharged to 50% every day, it will last about twice as long as when it is cycled to 80% DOD.

If cycled only 10% DOD, it will last about five times as long as when it is cycled to 50%. The

most practical number to use is 50% DOD on a regular basis. This does not mean that you can

not go to 80% once in a while. It is just that when designing a system when you have some

idea of the loads, you should figure on an average DOD of around 50% for the best storage

versus cost factor.

Also, there is an upper limit: A battery that is continually cycled 5% or less will usually not last

as long as one cycled down 10%. This happens because at very shallow cycles, the lead

dioxide tends to build up in clumps on the positive plates rather than in an even film.

Figure 4.2 shows how the battery life is affected by the depth of discharge.

Figure 4.2 Battery life based on depth of discharge

A Battery capacity

B Discharge time in hours

A Number of cycles

B Daily average depth of discharge in %

1 2 ... 7 8 9 10 11 12 13 14 15 16 17 ... 34 35

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Bosch PLN‑24CH12 Spécifications Page 12