12.0 volts or below - At 12.0 volts your battery is considered to be fully discharged or 'flat' and should be recharged as soon as possible. The lifespan of your battery will be severely affected if it remains within this voltage range for extended periods of time.
When the battery is not in use, recharge it if the open circuit voltage (OCV) drops below 12.5 volts. Deep cycle batteries are not designed to be kept in a low state of charge and will build up sulphation on the battery plates that will reduce the performance and cycle life of the battery.
These readings are also available on the side of the battery as a reference. Multimeter readings such as zero volts are indications of short-circuiting, while a 12-volt deep cycle battery that remains below 10.5 volts even after hours of charging might be a sign of a dead cell.
If your deep cycle battery that used to last for a long time is suddenly getting hot to the touch or seems to be draining far too quickly, it's time to get it tested or replaced. A hot battery under normal conditions means something isn't right inside the circuitry or actual chemical reactions within the battery.
Voltage on a fully charged battery will read 2.12 to 2.15 volts per cell, or 12.7 volts for a 12 volt battery. At 50% the reading will be 2.03 VPC (Volts Per Cell), and at 0% will be 1.75 VPC or less. Specific gravity will be about 1.265 for a fully charged cell, and 1.13 or less for a totally discharged cell.
12.1 - 12.4 volts - Your battery is partially discharged and should be recharged as soon as possible, using a suitable battery charger.
Most deep cycle batteries are built to handle a 50% depth of discharge, but some can handle up to 80% discharge.
A healthy 12 volt battery should maintain a voltage range from 9.6 - 10.5 volts under the load for a good 30 seconds straight.
How long do deep cycle batteries last? The average lifespan of a deep cycle battery is about 3-6 years. However, the lifespan of a deep cycle battery will vary based on several factors such as the type of battery, how it is used and maintained, and the climate in which it is kept.
Sometimes, deep cycle batteries can fail even sooner than their expected lifespan. Most often, this happens because of a chemical issue called “sulfation.” What is sulfation? Sulfation is the formation and build-up of lead sulfate crystals on the surface of the battery's lead plates.
If the voltmeter reads between 14-15 volts then the battery is normal. But if the battery reads over 15 volts or less than 13 volts, then there might be a problem with the alternator. The alternator is over charging the battery or not giving enough charge to the battery.
AGM battery's minimum voltage is 12 volts, meaning it can produce 12 volts when fully charged.
At 12.4 volts the battery is considered 75% charged and can still ignite your engine. When the battery voltage lowers to 12.2 volts without the engine running, it is considered a bad battery that may start your engine but is no longer capable of holding a charge.
If the battery is dead from poor maintenance, worn-out from too many deep cycles, overcharging, or excessive deep discharging; it probably can't be recovered.” Following manufacturer-recommended care and maintenance procedures will get you the longest life and best performance from any battery.
Typically, a fully charged deep cycle battery will have a voltage of over 12.8V - 13V. Below are a few common battery problems you can identify by the voltage measurements. If a fully charged AGM battery tests more than 20 percent lower than the fully charged voltage level, it's probably due for replacement.
Generally, it can take anywhere from an hour to 24 hours to fully charge a deep cycle battery, depending on those factors. A good rule of thumb is to divide the amp hours of your solar battery by amps delivered by your solar panels, battery charger, or the alternator and battery charger.
It can. A good battery should rest at a bit over 12volts and rise to about 13.5volts on charge.
Re: What should battery voltage be reading under load? More or less around 12.7 VDC is "resting voltage"... Battery below this voltage is discharging (if under load) or less than full charge (if resting). ~13.6 volts is "float charging" (keeping the battery full, but not really actively charging).
The reading for a fully charged battery should read 12.6 to 12.7 volts, some AGM batteries can be 12.8 volts, if you have a reading which is showing -12.6 or -12.7 then you have the probes the wrong way round.
How Long Will a Deep Cycle Battery Hold a Charge When Not in Use? These batteries can hold their charge relatively well when not in use. Still, users of lead-acid batteries should expect to lose 10-35% of the battery's power monthly without any intervention.
Battery current is described in units of C-Rate. For example, a 100Ah battery has a “C-Rate” of 100Amps. Thus to fully recharge a 12V 100Ah battery using a 12V/10A charger will take a nominal 10 hours if the battery is fully discharged.