Nearly all AGM batteries are "recombinant" - what that means is that the Oxygen and Hydrogen recombine INSIDE the battery. Copyright 2022 Northern Arizona Wind & Sun. They will gradually last for shorter periods in each discharge. VPC is the volts per individual cell - if you measure more than a .2 volt difference between each cell, you need to equalize, or your batteries are going bad, or they may be sulfated. If you look at the fine print, it has that rating only at 5% DOD - it is much less when used in an application where they are cycled deeper on a regular basis. All rights reserved. While some battery manufacturers state a higher maximum charge rate, such as C/3, higher charge rates can result in high battery temperatures and/or excessive bubbling and loss of liquid. Batteries that are being charged will be higher - the voltages while under charge will not tell you anything, you have to let the battery sit for a while. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This also means that since they are non-hazardous, the shipping costs are lower. The lower the internal resistance, the better. This is why your car battery dies on a cold winter morning, even though it worked fine the previous afternoon. The battery may short out or it will just last for shorter and shorter periods requiring a replacement purchase long before it should be necessary. However, there are often ratings for other depth of discharge cycles, the most common ones are 10%, 20%, and 50%. Capacity is increased at higher temperatures - at 122 degrees F, battery capacity would be about 12% higher. Typical efficiency in a lead-acid battery is 85-95%, in alkaline and NiCad battery it is about 65%. Much of this loss of efficiency is due to higher internal resistance at higher amperage rates - internal resistance is not a constant - kind of like "the more you push, the more it pushes back". Practically all batteries used in PV and all but the smallest backup systems are Lead-Acid type batteries. Most smaller deep cycle batteries (including AGM) use Lead-Calcium plates for increased life, while most industrial and forklift batteries use Lead-Antimony for greater plate strength to withstand shock and vibration. You might be thinking I have a 5 Amp appliance that I need to power for 20 hours, so what I need is a 100 Ah battery that was defined as such using the 20 hour rate. For a very brief discussion on the advantages and disadvantages of these and other types of batteries, such as NiCad, NiFe (Nickel-Iron), etc. Voltages are for a 12 volt battery system. To get a full charge, you must continue to apply a current after the battery voltage reaches the cutoff point of most of these types of controllers. Many batteries are sealed, and hydrometer reading cannot be taken, so you must rely on voltage. The most practical number to use is 50% DOD on a regular basis. Previously, Ed was chairman of the Marine Technology Department at the New England Institute of Technology. It is often hard to tell what you are getting in a "marine" battery, but most are a hybrid. Industrial deep cycle (Crown and Rolls 4KS series): 10-20+ years. A few Lithium-Ion types are starting to make their appearance, but are much more expensive than Lead-Acid and most charge controllers do not have the correct setpoints for proper charging. The Antimony increases plate life and strength, but increases gassing and water loss. This is not usually a problem with solar electric systems, but if an auxiliary generator or inverter bulk charger is used, current must be limited to the manufacturers specifications. AGM's will cost about 1.5 to 2 times as much as flooded batteries of the same capacity. Although these can be cycled down to 20% charge, the best lifespan vs cost method is to keep the average cycle at about 50% discharge. Batteries do not make electricity, they store it, just as a water tank stores water for future use. The major construction types are flooded (wet), gelled, and sealed AGM (Absorbed Glass Mat). The recombining is typically 99+% efficient, so almost no water is lost. If the liquid in standard wet cells is not mixed, the electrolyte becomes "stratified". It appears that the only current source for new cells seems to be from Hungary. Some models even have completely different plate designs to add even greater strength. The difference is in the structure. If you are investing for the long term and you would like your battery to get the most from your purchase then one with an Ah rating twice that which you actually require would give you a much better service life and actually represent a cost saving. Understand the demands of your on-board electrical equipment, and assess the abilities of your batteries and charging gear to keep up with those demands. A newer type of sealed battery uses "Absorbed Glass Mats", or AGM between the plates. The answer is related to the internal chemistry of batteries - at around 10.5 volts, the specific gravity of the acid in the battery gets so low that there is very little left that can do. Lead-Antimony (such as forklift and floor scrubber) batteries have a much higher self-discharge rate (2-10% per week) than Lead or Lead-Calcium (1-5% per month), but the Antimony improves the mechanical strength of the plates, which is an important factor in electric vehicles. Even most "dry charged" batteries (those sold without electrolyte so they can be shipped more easily, with acid added later) will deteriorate over time. Not quite. Float and charging voltages for gelled batteries are usually about 2/10th volt less than for flooded to reduce water loss. Lifespan is increased at the same rate if below 77 degrees, but capacity is reduced. Always remember the shallower the discharge and charge levels the longer your battery will last. Batteries that are stored for long periods will eventually lose all their charge. Lead-Acid batteries do NOT have a memory, and the rumor that they should be fully discharged to avoid this "memory" is totally false and will lead to early battery failure. This is converted to heat, which is why batteries get warm when being charged up. (The internal resistance gradually goes up because there is less and less to be converted back to normal full charge). The 6-hour rate is often used for industrial batteries, as that is a typical daily duty cycle. Ed Sherman is a regular contributor to boats.com, as well as to Professional Boatbuilder and Cruising World, where he previously was electronics editor. It is aVERYpoor idea to buy new batteries and "save" them for later. At 122F (50C), capacity is improved by 12%. The plates are composed of a Lead "sponge", similar in appearance to a very fine foam sponge. Some Peukert Exponent values (not complete, just for info). There is a great deal of misunderstanding that surrounds deep cycle batteries, which often leads to extra costs as buyers follow false economies. In a dead battery, the specific gravity can fall below 1.1. Here is the summary: It is worth knowing that the capacity of all rechargeable batteries decreases with age and deep cycle units are no exception. that are more suited for deep cycle batteries. Not everyone needs these features. Deep Cycle Battery as a Starting Battery. Not all shunt type controllers are 100% on or off, but most are. The Crown L-16HC size has .22" thick plates. What taper charge really means is that as the battery gets charged up, the voltage goes up, so the amps out of the charger goes down. A "float" trickle charge should be maintained on the batteries even if they are not used (or, especially if they are not used). In such cases, the specific gravity and the voltages may vary from what we show. This makes sure that all the cells are equally charged, and the gas bubbles mix the electrolyte. Trojan Battery- not a lot of real technical info here, but has all the specifications.Rolls Battery- Specs and data on the Rolls & Surrette deep cycle and marine batteriesConcorde- specs and data on all the Concorde batteries, including Lifeline.Discover Battery - Lots of info on the Discover Battery brand of batteries.Discover Solar - A solar specific site for the Discover Battery brand.SimpliPhi, Posted in Batteries & Charging. Note that forlong termfloat service, such as backup power systems that are seldom discharged, the float voltage should be around 13.02 to 13.20 volts. Chargers: Most garage and consumer (automotive) type battery chargers are bulk charge only, and have little (if any) voltage regulation. Top 10 Choices for Boaters, 11 Holiday Gift Ideas For Boaters This Season, 10 Cool Last Minute Holiday Gifts for Boaters. State of charge, or conversely, the depth of discharge (DOD) can be determined by measuring the voltage and/or the specific gravity of the acid with a hydrometer. A battery "cycle" is one complete discharge and recharge cycle. The major applications are automotive, marine, and deep-cycle. As you can see, two batteries, both rated 100 Ah, can perform very differently. 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. Float voltage for Lead-Acid batteries should be about 2.15 to 2.23 volts per cell, or about 12.9-13.4 volts for a 12 volt battery. This has allowed some less reputable manufacturers to label starter batteries as deep cycle especially in the lead acid battery arena. It is for this and other reasons that we no longer sell any of the gelled cells except for replacement use. The advantage of these batteries is that it is impossible to spill acid even if they are broken. They charge OK, but a charger rated at 20 amps may only be supplying 5 amps when the batteries are 80% charged. For longest life, batteries should stay in the green zone. It can range from about 1% to 15% per month. The best determination is to measure the specific gravity, but in many batteries this is difficult or impossible. Occasional dips into the yellow are not harmful, but continual discharges to those levels will shorten battery life considerably. Usually older batteries need to be watered more often. These are often called traction batteries because of their widespread use in forklifts, golf carts, and floor sweepers (from which we get the "GC" and "FS" series of battery sizes). Batteries are divided in two ways, by application (what they are used for) and construction (how they are built). These use a variable voltage to keep the charging amps much more constant for faster charging. Some of the various brands and models that we use and recommend are listed below. Nearly all large rechargeable batteries in common use are Lead-Acid type. We sell the Concorde (and Lifeline, made by Concorde) AGM batteries. Those same batteries are rated at less than 5 years if cycled to 50%. Many inverters and charge controls have a hard time with them. It is sometimes hard to tell, as the term deep cycle is often overused - we have even seen the term "deep cycle" used in automotive starting battery advertising. This does NOT mean you cannot go to 80% once in a while. The positive (+) plate is what gets eaten away gradually over time, so eventually there is nothing left - it all falls to the bottom as sediment. PWM, or "pulse width modulation" accomplishes the same thing. The chart is for a Concorde Lifeline battery, but all lead-acid batteries will be similar in the shape of the curve, although the number of cycles will vary. Finally, we made appropriate changes based on the environmental temperature the battery was likely to be operating in. Because of this characteristic, you have to be on the lookout for under handed manufacturers who might try to pull the wool over your eyes. For the best experience on our site, be sure to turn on Javascript in your browser. Automotive batteries will generally fail after 30-150 deep cycles if deep cycled, while they may last for thousands of cycles in normal starting use (2-5% discharge). All AGM & gelled are sealed and are "valve regulated", which means that a tiny valve keeps a slight positive pressure. The links below are on this page - you can also just scroll down if you want to read them all. The subject of batteries could take up many pages. A charge controller is a regulator that goes between the solar panels and the batteries. There is no "best" controller for all applications - some systems may need the bells and whistles of the more expensive controls, others may not. AGM batteries main advantages are no maintenance, completely sealed against fumes, Hydrogen, or leakage, non-spilling even if they are broken, and can survive most freezes. We learned how to recognizea real deep cycle battery and not a mislabeled starter battery, We checked the discharge rating used by the manufacturer to arrive at their Amp Hour rating, where we determined a 100 Ampere Hour battery (at the 20 hour rating) would power our 5 Amp appliance for the required 20 hours. So a 100Ah battery should power a 100 Amp appliance for one hour . For gel cells, subtract .2 volts. In the hybrid, the plates may be composed of Lead sponge, but it is coarser and heavier than that used in starting batteries. The charging voltages are the same as for any standard battery - no need for any special adjustments or problems with incompatible chargers or charge controls. The newer AGM (absorbed glass mat) batteries have all the advantages (and then some) of gelled, with none of the disadvantages. Voltages at this stage are typically around 14.2 to 15.5 volts. that it is almost impossible to give a fixed number. Throughout this article we have been considering which battery we would need to power a 5 Amp appliance for 20 hours. How to Buy a Boat: Tips for a First Time Buyer, Top 10 New Fishing Boats for Under $20,000, What Type is Right for You? In a recent article on boats.com I talked about amperes in your boats electricalsystem. Here well cover the steps you can follow to find the right battery for your needs. Float Charge: The 3rd stage of 3-stage battery charging. In leisure applications, this is often inevitable yachts, for example, can be cold, especially at night when far from shore and this is the exact time the battery is needed. Obviously, there are some practical limitations on this - you don't usually want to have a 5 ton pile of batteries sitting there just to reduce the DOD. The biggest problem with NiFe batteries is that you may have to put in 100 watts to get 70 watts of charge - they are much less efficient than Lead-Acid. This gives less surface area, thus less "instant" power like starting batteries need. Plate thickness (of the Positive plate) matters because of a factor called "positive grid corrosion". If measured right after charging, you might see 1.27 at the top of the cell, even though it is much less at the bottom. This may occur several hundred times per minute. Generally, new AGM batteries have the lowest, and old industrial (Lead-Antimony plates) are the highest. Marine batteriess are usually a "hybrid", and fall between the starting and deep-cycle batteries, though a few (Rolls-Surrette and Concorde, for example) are true deep cycle. Photo courtesy of ProSport. Distilled or deionized water should be used to top off non-sealed batteries. This means longer charging time and/or higher finish rate (higher amperage at the end of the charge). Meters for Amps (from the panels) and battery Volts are optional with most types. Do not put a new battery in a pack which is more than 6 months old or has more than 75 cycles. If left for long periods unused, these should be trickle charged to avoid damage from sulfation - but this applies to ANY battery.