Velleman PI2500B Mode D'emploi page 5

3. Do not leave batteries in a discharged state for more than a day or two. They will undergo a chemical process
called sulphating, which can permanently damage the batteries. Also, batteries will self-discharge over a period of
3 to 6 months, so they should be periodically recharged even if they are not being used.
4. If batteries are not of the 'maintenance-free' type, check the electrolyte fluid level at least once a month. Use only
distilled water to replenish the electrolyte fluid. Excessive fluid loss is a sign of overcharging.
5. Connections to battery posts must be made with permanent connectors that provide a reliable, low resistance
connection. Do not use 'alligator' clips. Clean the connections regularly and prevent corrosion by using an
insulating spray coating or Vaseline.
6. Battery state of charge can be measured with a hydrometer or a voltmeter. Use a digital voltmeter that can display
tenths or hundredths of a volt when measuring 10 to 20V. Measure the voltage after the battery has not been
charged or discharged for several hours.
Battery Capacity: deep-cycle batteries are rated either by reserve capacity in minutes or by ampere-hour capacity.
Battery reserve capacity is a measure of how long a battery can deliver a certain amount of current - usually 25A.
E.g. a battery with a reserve capacity of 180min can deliver 25A for 180 minutes before it is completely discharged.
Ampere-hour capacity is a measure of how many amperes a battery can deliver for a specified length of time -
usually 20h. E.g. a battery rated at 100 ampere-hours can deliver 5A for 20 hours (5A x 20h = 100 amp-hrs).
Actual battery capacity decreases as discharge current increases. A battery rated at 100 amp-hrs can deliver 5A for
20h, but may only deliver 20A for 4h, resulting in an actual capacity of 80 amp-hrs.
To determine the battery capacity you require, follow these steps:
1. Determine the power consumption for each piece of equipment you will be operating. This can normally be found
on the product label. If only the current draw is given, multiply it by 225 to get the power consumption in Watt.
2. Determine how long each device will be operating between battery charging cycles.
3. Calculate
- watt-hours per device: consumption x operating time
- total watt-hours: the sum of the individual watt-hours
- total operating time: sum of the individual operating times
- average power consumption: total watt-hours/total running time
- amp-hrs needed: total watt-hours/10 (12V but with a margin).
4. Select the battery that suits your needs best, keeping in mind that battery life is directly related to battery
discharge: the deeper the discharge, the shorter the battery life. Ideally, you should use no more than 50% of the
battery's rated capacity.
Using multiple batteries: to obtain sufficient battery capacity, you may need to use
more than one battery. Two identical batteries can be connected in a parallel
system (see fig. 4) that doubles the capacity and maintains the voltage of a single
battery. Do not connect batteries from different manufacturers, or with different
amp-hrs ratings, as this may result in decreased battery life.
Fig. 5
PI2500B & M 12V
If you need to use more than 2 batteries, it is
recommended you set up 2 separate battery banks
and use them alternately. A battery selector switch
allows you to choose between the 2 banks, use both
in parallel, or disconnect both (see fig. 5).
1. PI2500B & M
2. Battery selector switch
3. Battery bank 1
4. Battery bank 2
5. Vehicle start battery
6. Isolator
7. From alternator or charger
8. To chassis ground
5
Fig. 4
VELLEMAN