If you run a 10A load for one hour then 10Ah are consumed. This shows the amount of energy stored or removed from the battery. solar, alternator, charger, etc) would show up as a positive number.Īh = Amp-Hours. If you had no loads on your batteries, any charge going into the batteries (e.g. This is an important function to teach your crew as it serves as a good reminder to turn off unused lights, navigation equipment, etc. Discharge is shown as a negative number and shows the number of amps that are being consumed. Your fridge may draw 6 amps of current and this is displayed as -6.0A.
For example, I am drawing 10 amps and, if the current was constant for one hour, you would say I used 10 amp-hours (more info on amp-hours below). While driving a boat, you would say I’m doing 10 knots, and you would cover 10 NM if you travelled for one hour. Current is analogous to speed, it’s the rate at which electricity is flowing. Amps is the flow of current in or out of the battery. Imagine a battery bank at 11.9V, a 100A alternator will get 2 golf cart batteries to 14.4V in little time, conversely a 55A alternator will take hours to get 8 golf carts batteries to 14.4V.Ī = Amps. A good analogy is topping off a pool with water, how quickly it takes for the water level to reach full, depends on the combination of the hose filling the pool and the size of the pool. It’s hard to predict where the voltage will rise, as it depends on the size of your battery bank and the charge rate. For instance, if your batteries were at 12.1V before charging, you will want to see that number increase. When charging, you are looking for an increase in voltage. A 12V battery is 50% discharged at 12.2V assuming there are practically no loads on the battery. A 12V battery is 100% discharged when it reaches 10.5V. For example, an at-rest, fully charged 12V battery bank will show about 12.6V to 12.8V. Voltage is used to assess the approximate state-of-charge and to check for proper charging. Let’s start with the four pieces of information you commonly see on any battery monitor: We have written a number of articles on how battery monitors work but we recently received a request from a boater to interpret his battery monitor while the batteries are being charged from three different sources, the generator, the alternator and shore power. It’s similar to a fuel gauge and speedometer for your house batteries and it really takes the guesswork out of managing your energy consumption. If you don’t have a battery monitor on your boat, we highly recommend having one installed.
Understand Your Battery Monitor While Charging