-12volt 150watt Price ; please email to alvis_333@yahoo.com
Volts, Amps and Watts
WATTS are the units of POWER. A hairdryer full-on might be 500 WATTS; on the low-power
setting it might be 200 WATTS.
The higher the POWER the bigger the charger.
VOLTAGE must be matched to the equipment in use and will be either 12 VOLTS or 24VOLTS in a boat.
CURRENT indicates the flow of energy from the battery and is measured in AMPERES (orAMPS). Zero current and the battery is not discharging. The higher the current the faster the battery will discharge.
A battery is rated in AMPERE-HOURS (abbreviated Ah) and this is called the BATTERY CAPACITY. For example, a small boat might have a 12 volt 100Ah battery. This battery will provide 100 AMPERE-HOURS before needing to be re-charged. This may be taken from the battery as
1 AMP for 100 hours
2 AMPS for 50 hours
10 AMPS for 10 hours etc.
WATTS are VOLTAGE multiplied by CURRENT, so taking the above example with the 12 volt
battery
1 AMP x 12 VOLTS = 12 WATTS for 100 hours
2 AMPS x 12 VOLTS = 24 WATTS for 50 hours
10 AMPS x 12 VOLTS = 120 WATTS for 10 hours
Re-charging a battery follows the same principle. The requirement is usually to re-charge the battery over-night - say in 10 hours.
Because a battery is not totally efficient at converting electrical energy into chemical energy and vice-versa, re-charging a 100Ah battery requires about 120Ah to be put back into it, and this can be achieved by either
120 Amp-hours / 10 hours = 12 Amps for 10 hours
120 Amp-hours / 15 hours = 8 Amps for 15 hours
120 Amp-hours / 24 hours = 5 Amps for 24 hours etc.
CURRENT = WATTS / VOLTS
therefore if, say, the lights add up to 36 WATTS and the battery VOLTAGE is 12 VOLTS then the CURRENT taken from the battery will be
36 WATTS / 12 VOLTS = 3 AMPS
If these lights are on whilst the battery is being charged, then the battery charger must also provide an extra 3 AMPS to power them.
Battery Charger Selection By Calculation Example
Below is a sample calculation to determine which of our products would best suit your
requirements.
1. Determine the battery voltage - 12 volt or 24 volt
2. Determine how many batteries are to be charged (1,2,3 or 4)
3. What are the battery capacities (Ah, Amp-hours)?
Add them together
e.g. 2 x 60Ah, 1 x 100Ah = 220 Ah total
4. What re-charge time is required?
(6 hours minimum, usually 24 hours maximum - if not known, assume 10 hours)
5. Divide TOTAL Ah by the re-charge time to get CHARGING CURRENT
e.g. 220Ah / 10 hours = 22 AMPS.
6. ADD 20% to allow for battery in-efficiency
i.e. 22 AMPS + 20% = 26.4 AMPS
7. Is there any additional load current on the battery during re-charging? If so, add this to the
CHARGING CURRENT.
e.g. 24 WATTS / 12 VOLTS = 2 AMPS
CHARGER CURRENT REQUIRED = 26.4 AMPS + 2 AMPS = 28.4 AMPS.
8. Choose the next biggest charger in the range
e.g. 12 VOLT, 30 AMP, 3 BATTERY BANKS = BCM 12/30-3
Note
Much too big a charger could damage the battery and too small will take longer to re-charge.
