Differences in deep cycle battery chemistry. Wet Cell or flooded vs. Absorbed Glass Mat or AGM
Many people refer to AGM deep cycle batteries Gel which is an incorrect statement. They both have Marine terminals that allow you to connect cable to them. They have an auto post and a stud connect cables to. This particular battery is a deep cycle dual purpose battery Size 24. This is also a group size 24 deep cycle Dual Purpose battery. This particular battery is sealed and it's maintenance-free but if you shake it it's got water inside of it. You don't have to replace the water but it can still can get flooded with lead-acid battery. This battery by AGM Tech is a sealed acid-free corrosion free, gas free very safe AGM battery. What's nice about the AGM is that is superior to the flooded in the fact that it has less intro resistance which means it charges up a lot quicker because it's sealed it doesn't have any way to gas. It holds its charge a lot longer for instance you could expect the smaller version lead acid battery self-discharge 1% per day by itself. Compared to the AGM battery where you can expect it to self discharge at 1% per month. The AGM deep cycle battery is a great application for boats especially when you can't get to it to replace the water but what's nice about the AGM batteries. You can actually install it on its side for a tight compartment with no problems. The plates inside this battery are supported by a glass mat that's where the word AGM comes from. The mats is between the plates so when you have vibration, the plates aren’t loosened up which causes shorting. This vibration causes wet cell traditional batteries over time. The AGM battery is a Superior battery and it does cost a little bit more money but lasts lot longer that traditional SLI batteries.
Deep cycle batteries you might want to consider for RV's and the like. Amp hours and how they relate to battery hours is how many is how many amps a battery can steadily deliver in a 20 hour period. A good example is a 100 amp battery will provide 5 amps for 20 hours and what you know if you go below that 20 hours are above that 20 hours you're going to get either less or more of that hundred amps. Lead acid battery. gel cell and AGM you will get roughly 80% of the charge rated amps in the 4 hour period. Only 60% roughly in a 1 hour. The lithium-ion is 99% in a 4 hour period and 92% in a 1 hour period. So basically if you discharge 100 amp battery to 0 in a 4 hour period, you're only going to get 80 amps out of it. So that's just something to keep in mind if you using a high draw item like a inverter. One cycle is 1 charge and 1 discharge cycle. DOD stands for depth of discharge before recharging. Various batteries on the market have different DOD's. Lead acid you can usually discharge down to 50% then like a gel cell battery which is like 80% so there is some variation in that depending on the battery type. See the table below showing an average of 50 amps deliverable, not so much the capacity of the battery but how many amps are available for the user to use in that specific battery.
In the chart you will see the average ballpark on the price,weight,cycles and more. With a lead acid battery you only get a 50% discharge on it so you need a 100 amp battery for it. A Gel cell battery will discharge all the way down to 80% so all you need is a 62 amp battery and usually Gel cells are more expensive than the AGMs but when you comp them as to how much actual amperage there is, the cost for the Gel cell is less versus the AGM. Lead acid batteries can cost around $80. If you go for a 6 volt golf cart battery they can cost upwards to $200 each. So above you can see 50 amps of usable power from the battery with the charger.
Above is a diagram of a battery so that you can see what causes batteries to degrade. Lead batteries are all pretty much built the same way. The flooded lead-acid battery, the gel cell and the AGM. You basically have lead plates both positive and negative and they are inter leafed together with spacers in between them. Each of these plates is 1volts which make a cell. So 6 cells will equal to 12 volts. You'll have 6 cells in a 12 volt battery and 3 cells in a 6 volt battery. In a flooded lead-acid battery there will be 6 caps for the 12 volts. Three caps for the 6 volt battery will be available. The lead-acid batteries have acid which comes up above the plates. Half inch to 3/4 of an inch above the plates and you definitely want to keep that topped off with the distilled water because if the fluid gets below the plates, lead sulfate will build up on the plates and diminish the capacity of the battery. The biggest killer of flooded lead-acid batteries is a sulfate building up on the plates and it's a natural byproduct of the discharge process of the battery. Usually when you recharge a battery it sort of dissolves all that sulfate and puts it back into the electrolyte. But if you don't charge up the battery right away it'll start to harden. Lead sulfate will start to harden on the plates. Another problem with the the flooded lead-acid batteries is also that that sulfate break off and some of the lateral plates will shed and buildup in at the bottom of the battery. It will eventually short out the plates, killing the cell and killing the battery altogether. The gel cells are built almost identically except for the electrolyte is that it has a consistency of vaseline. It wont' leak at all. AGM which is absorbed glass mat is what a GM stands for and there's a glass mat that goes in between the plates and is saturated with electrolyte.
Pros and Cons of a Lead Acid Battery
The lead-acid battery is the most common type of battery out there with your car starting battery being most popular. If you have an RV it'll have a deep-cycle flooded lead-acid battery in it. The biggest pro is at the very cost effective Dollar per amp they're hard to beat. They have a relatively long life given you maintain it properly. You will get just a s long life cycle as you will in general as with a AGM or gel cell battery. Lead acid batteries do have a lot of cons the biggest one is they produce hydrogen gas which is explosive. You have to be careful when you're around them and they do need to be vented to the outside. None of these lead acid batteries you want to have in a sealed container. Lead acid batteries have to be specifically vented to the outside. Lead acid batteries are not spill proof as they contain lead acid. Thirty percent of sulfuric acid is the main harmful component in these batteries. Maintenance is needed with the distilled water and clean the terminals once in a while. Water loss is very easy preventive maintenance. Be sure to always maintain a good charge as they have a high self discharge rate which is about 1% a day. The specific gravity of these has to monitored every month to extend battery lifespan. So with 100 amp battery you can lose up to 30 amps a month. That is why you need to have a trickle charger on them. Trickle charging is a life saver for many other battery recharging needs. Also they're really slow to charge compared to the other batteries. On average a 6-8 hour charge time is needed and sometimes a 12 hour window is needed. EverStart deep cycle marine batteries from Walmart are really dependable for a long time. Marine batteries are really good option for marine solar applications. Using a charger that came with a RV and it's just about one stage taper charge. Full time use you can expect 1.5 to 2 years before replacing these. Once you start using a solar panel to charge these you can add another year to that life cycle. Most all lead acid batteries have a 50% the depth of discharge so you can discharge them to 50%. From the previous chart above using 50 available apps for the users here so you need a hundred amps to do that and the cost is roughly $110 for a golf cart batteries. You'll can expect to pay up around $150 for a 50 amps. With the golf cart batteries if you look at them side by side they're actually taller and there is a space on the bottom there so the material that sheds off the plates can build up and not reach the plates. Also golf cart batteries have heavier and more reinforced lead plates. With regards to lead acid batteries, the heavier the better because it's that lead that adds the quality to them. The manufacturer lists them at about a thousand cycles but you know how these cheap Walmart batteries it might be 300 or 400 cycles in real life. Just varies on the quality of the battery and charge time of course at 68 hours. Sometimes even up to 12 hours with a special charger. Charger price is $150 on a flooded batteries. You want a 4 stage charger because that fourth stage is a equalization charge and that helps dissolve the lead sulfate that builds up on the plates from time to time. With everything it comes to $260 so you know the $150 for the roughly for the charger and $110 for the cost of the battery.
Why pay more for quality deep cycle batteries?
Gel cell batteries, AGM and Lithium ion are fairly expensive compared to lead acid but if you full time RV or dry camp a lot, these batteries are worth the upgrade. One main reason to buy a more expensive battery is if you don't want to do the needed maintenance. It takes a lot of maintenance to keep the batteries going and it's not rocket science or anything but the batteries are really heavy. You have to deal with electrical wiring, there is battery acid and then of course explosive hydrogen gases. Hydrogen is formed when the batteries are charged. You have to keep track of equalization charges as well. You might want to consider getting a hydrometer for proper maintenance. Also a lot of times the battery boxes aren't really easy to get to and it's just a pain overall. Even getting to the batteries to check the the fluid levels in the batteries. So it's sort of a pain and almost a hobby maintaining them. This is something you have to do though to keep them in check. Whether you are using the RV or not. Even if the RV's sitting up next to your house and it is just plugged in. You still have to do it and it's something needs to be done about every 3 months or so. You need to check the fluid level in the battery and top it off if needed and clean the top of the battery and get there any corrosion off the terminals. This maintenance needs to be done regularly otherwise a battery is just going to sulfate and you know you're not going to get much of a life span. You'll end up replacing it more often then you need to and then of course you might as well have had a good battery and then you wouldn't have even had the mess with it in the first place. The lead acid batteries are definitely the cheapest, dollar per amp but you have to put some of your own sweat equity into them. Another good reason to buy a more expensive battery is if you're using a generator to charge your battery. These more expensive batteries are going to charge a whole lot faster than the lead acid battery. More importantly they have a lot less tendency to build up sulfate on the place which ends up killing the battery slowly. Then you end up replacing it more buying more cheap batteries over and over again. In comparison you can invest in a nice AGM battery, gel cell or lithium ions. A third good reason is that you can store them in out-of-the-way places that you don't need access to. You want to make sure they're secured but be sure to leave a little bit of ventilation. Inside of cabinets or under beds will work for storage. These batteries don't off gas to a degree where you have to worry about them. So in the long run if you're not really into maintenance type activities you might really want to consider one of these more expensive batteries as you can just put them someplace and forget about them. Replacement time is on average in 7-10 years until you have to replace these. It makes life a whole lot easier.
Deep Cycle Gel Battery or Gel Cell
Surprisingly gel cells batteries aren't that popular with rvers. Some of the pros include no maintenance and really good resistance to vibrations. Superior recovery from deep discharges. You can discharge gel cell batteries down to 80% and leave it for a month come back charge it back up and the battery is like new again. Super fast charging time of 2 to 3 hours. Absorbing charge is really fast and they have a really low self-discharge of about 1 to 3% a month as compared to 1% per day for the flooded lead-acid batteries. Gel cell batteries are sealed and they won't leak or spill. So you don't have to worry about any battery acid or any spills. Also no off gas with these as well. As far as cons they cost 2-3 times as much as a flooded lead-acid battery. Gel cell batteries are also their larger and heavier. So a 100 amp lead acid battery will weigh 10-15 pounds less compared to a 100 amp gel cell. Also for the gel cell you need a special charger and the charger is only good for gel cells. Gel cells can't take the higher voltage that the lead acid batteries and AGMs can. Overall they are pretty cost-effective more expensive than AGMs but that when you figure out you'll be able to get 50 usable apps out of the battery with a gel cell you only need 62 amps to get 50 amps out of it. Compared to the AGM where you need a hundred amp hours to get 50 usable amp hours. So the cost is actually less than the AGM. Also the weight as well. Get the AGM just because it has a much better resistance to vibration. The numbers are fairly comparable between the cost of the two. Both are definitely worth taking a look at and considering. Unlike an AGM battery you cannot lay the Gel battery on its side. The gel anatomy is such that it has vertical plates and the top of the battery is this gel material that is used for the electrolyte. You do not have to maintain these batteries. The electrolyte is injected in the caps on the top of the battery and sealed shut. A gel battery and a standard liquid battery charge differently. Gel batteries typically take a softer charge and can be easily overcharged if you don’t have the correct charging profile.
The AGM Deepcycle Batteries
Absorbed glass mat AGM batteries are currently the most popular of these three battery types for a RV battery choice. You can expect these to last over 10 years easily. Install one of these in a cabinet or in the battery box and never look at it again! The until time to check it is when you need to replace it. came time to replace it there's pros and cons this with all the batteries. A truly huge pro for the AGM is that is has a very good vibration with the absorbed glass matt between the plates. The glass matt is really packed in really tight into the cell so there is virtual zero vibration. The AGM batteries are used a lot in aviation and have a fast charging time of 2 to 3 hours. Low self-discharge rate from roughly 1 to 3% a month and are totally sealed so they don't spill any battery acid and no off-gassing. No venting is required to the outside. The price is 3 times the cost of lead acid battery and they are larger and heavier than the largest and heaviest of these three battery types. A special charger is sometimes needed but with most AGM manufactured batteries you can just use a regular 3-stage battery charger. Very much comprable to the gel cel but they are a little heavier and really good cycles. So with lead acid batteries expect to replace them every 1.5 years but once you have a solar to charge these you can pretty much double the life span. The AGM you can safely charge about every third or fourth day. But it is a good habit to charge these once a month off of a power rv park or electricity to top them off. The long time in between full charges does not really affect the AGM batteries. But it definitely shorten the life of the lead acid battery significantly. Both Gel Cell and AGM batteries are sealed battery types and are truly maintenance free. Finally AGM batteries are referred to as SLA, sealed lead acid or sealed battery type.
Lithium Ion Batteries
Lithium iron phosphate batteries if you happen to remember some of your old chemistry or science classes.They have a ton of pros and just one major con. Pros are again no maintenance excellent good weight to power ratio. You get 3.5 x amount of energy out of the Lithium-ion batteries versus out of a similar weight lead acid battery. Very good resistant the vibration again very good recovery from deep discharges. Fast charging is 2 to 3 hours. They have a low self-discharge rate under 1% a month. No off-gassing as there's no acid so you don't have to worry about leaks. The lithion ion batteries don't produce sulfate. There is no plates to build sulfate on. No electrolytes in these batteries so there again you don't have to worry about sulfate. The major con is it it's a five to six times the cost of a flooded lead-acid battery. They also need a special charger which you have to have for these batteries. At five to six times the cost of a battery is about $600 but pricing keeps coming down every year. Also these batteries most come with complete battery management system built into the battery. Many people call it a smart battery. Very much resembling an AGM battery in the design also. Similar to a 24 group battery but all built in and complete so basically all you need is a charger and the wiring between the charger in the battery. If you get up in the bigger systems you can go with your individual cells and then you have a battery management system. The BMS is separate from the actual batteries. In this systems which have the battery Management Systems built into the actual batteries in the chart. Many solar electric solutions are currently using lithium ion now including for battery backup systems.
Just like with gel cell batteries you can take it down to 80% discharge and all you will need is 62 amp hour battery to get the 50 amps out of it. That 50 amps will cost you $600. The weight is a lot lighter at around 20 pounds and over 2000 + cycles out of lithium ion. Expect 2-3 hours of charging time. Chargers for lithium ion batteries aren't that expensive at only about $100 each. These should come down in price as technology and supply improves. Currently at $600 for each battery is a major stumbling block. If you are concerned about weight these batteries are for you. If price is not an issue you might want to consider these batteries. Overall you can see that lithium iron phosphate have a lot of pros. But you can do just fine with an AGM battery. Shove it into a box, save some money and don't look at it for 10 years. I don't think there is $300 more dollars added by being 40 pounds lighter. Once the price comes down $200-$300 then it is time to buy these batteries. Also you can can get used lithium ion batteries and what is really popular now is doing a bulk charge which can save you upwards of 50% off the price of a new one.
Golf cart batteries are 6 volt batteries and they're really heavy duty deep cycle flooded lead acid batteries. Golf cart batteries have more than double thicker plates compared to the plates in automotive batteries. A lot of people swear by these especially the Trojan t105 battery from the Trojan battery company. Cost is about $160 each for the 6 volt battery and you need 2 of them so for roughly $340 you get the 225 amps out of it. So 110 usable amps which is really inexpensive. These are also high quality batteries. You do need to maintain them as I mentioned earlier but if you have solar they are really easy to maintain. Basically you just take a hot off one of the positives and you connect the negative to the positive battery and then you take the negative all that second battery and you get 12 volts. A regular 12 volt charger will charge them and all that's connected in series. You don't want to do that wiring if you're connecting 12 volt batteries together. 12 volt batteries you always want to connect in parallel. You just basically take the positive off both of them and connect the negatives up and you'll get 12 volts. It's always better to have one big battery than two small batteries and it's better to have one big bank then two small banks. It goes back to that the formula of you know how many amps you take out over certain period of time to how many amps do you get out of it total. If you're taking out 5 amps out of two 12 volt batteries, you're only taking two and a half amps out of each of the batteries. Essentially by doing this you get a longer lifespan out of your batteries. Also you'll get more amps out of it over the 20 hour period. I have found by just having two separate battery banks work great. You can use 1 battery to power the RV heater and the lights. Then have a separate AGM battery to power a laptop and similar electronics. Balance out the energy with your current situation.