Admin and Mods I am writing this as informational only to be used as a Sticky Topic. If you opt to make it a Sticky please lock the thread up so as not to become polluted with replies. Question can be opened in other threads. I am the author of the 3-part Groundings Do’s and Don’ts. I have been in telecom and power generation for 40 years as a professional engineer. In my tenure I have worked with every major battery manufacture and in the 90’s and early 2000’s when I worked with MCI Worldcom was the world’s largest customer/consumer and sat on IEEE Battery Standards committee. We hams have use for batteries, all types but primarily Pb lead acid batteries for a good reason. Pb batteries have the longest service life and offer the best value. Unfortunately most Pb batteries are abused, wrong type selected for the job, and when coupled with improper care cut their service life severely short. So the purpose here is to clear up some myths, how to select and care for Pb batteries. So let’s start with the 3 basic types. SLI (Starting Lighting & Ignition) Do Not Use Them period. Using SLI batteries for cycle applications is the number 1 mistake consumers and ham radio operators can make. SLI batteries are designed to deliver very high burst of current to crank and engine, and then be recharged very quickly. The plates are thin and spongy to increase surface area to lower the internal resistance which is required to deliver the high starting currents. If pressed into cycle service you are only going to get a very limited number of cycles, and less capacity with each cycle. The thin spongy plates dissolve quickly when cycled and end up in the bottom of the jar. They are easy to spot in the specs. They typically only have Cranking Amps specification of CA, CCA, HCA, and MCA. You will NOT likely see an Amp Hour Rating. I will stop there, they should NOT be used. True Deep Cycle Batteries As the name implies these types are made to be deeply cycled and what you will most likely want to use for most applications. They are constructed with thick heavy plates filling the battery jar using lead antimony alloy and some are doped with Selenium to improve self-discharge and lower Float currents. Higher end Deep Cycle batteries are using Carbon Technology to improve Partial State of Charge performance. Unlike SLI batteries they cannot deliver high currents because they have higher internal resistances. Thus limits the charge and discharge rates to roughly C/6 where C = the specified Amp Hour capacity, and the integer represents Hours. So if you have a 100 AH battery means limit charge and discharge current to 100 AH / 6 H = 16.67 amps or 17 amps max. Deep Cycle batteries quality range greatly. At 50% DOD lower end will only give you 300 to 400 cycles. Higher end models can give you up to 2000 cycles. The dead giveaway on longevity is the warranty period which runs 1 year on low end, and up to 10 years. True Deep Cycle batteries typically will only list AH specifications and not capable of delivering high cranking currents. A good quality Deep Cycle battery will have a few different AH rating capacities based on the Hour Discharge Rate. Rates are typically 100 hours, 20 hours, 10 hours, 8 hours, 4 hours. This has to do with Peukert Effect which I will go into later. Hybrid Batteries Hybrids try to fill the void between Deep Cycle and SLI batteries. They are super easy to spot because they come with gimmick marketing names like Golf Cart, RV, Leisure, Floor Machine, Electric Vehicles, Trolling Motors, Fish Finder, Marine Deep Cycle, Wheel Chair, and the list goes on. They have thicker heavier plates than SLI, but not as heavy as Deep Cycle. Their advantage is they can deliver higher currents for limited cranking current, but they give up cycle life doing so. Hybrids have a use in ham radio application because they can deliver higher discharge rates of C/4 which means a smaller battery can be used. So if you have a radio that demands 25 amps on TX, you can get away with a 100 AH battery vs 150 AH for a Deep Cycle. Again quality ranges wildly with these batteries. A 2 to 4 year warranty is about the best you can get. A hybrid is easy to spot in the specs as they will have AH, CA, and RC ratings. Construction Types PB batteries fall into two construction types of Flooded Lead Acid and Sealed Lead Acid (SLA) aka Valve Regulated Lead Acid (VRLA). SLA fal into two sub categories of AGM and Gel. FLA batteries offer your best value and longest cycle life. They can take a lot more abuse, and battery health is monitored by taking the Specific Gravity readings. The only way to determine the true State of Charge (SOC) and health of a lead acid battery is by taking the Specific Gravity. From that you can determine when and if an Equalization charge is required or not, and if your charge voltage settings are correct. AGM or Absorbed Glass Mat batteries use a fiberglass mat with starved electrolyte absorbed into the fiber glass mat. They definitely have applications in ham radio, but you need to justify their use because they cost twice as much (AH Capacity) and half the cycle life of FLA making them some 300 to 400% higher cost than FLA in the end of life. Some of those justifications are: Extreme cold environments, Where spills cannot be tolerated, unusual mounting orientation like on their side, and where high discharge and charge rates are a must. By their design nature makes them a hybrid battery. Some can easily deliver discharge currents of C/2 or 50 amps on a 100 AH battery. Question is can you afford them. Gel batteries should not be used. They are very fragile batteries and cannot tolerate any overcharging and by the design have short cycle life. To add insult to injury are very expensive. The electrolyte is a gel and just the slightest over charge dries out the gel that leaves voids and cracks in the gel which a permanent and accumulative damage. Gel battery application is for egress lighting and alarm panels made for float service using very low charge rates. Stay away from them like SLI batteries. To Parallel Or Not To Parallel. Short answer is to never parallel Pb batteries. There is no reason too, and if you do will cut cycle life in half or more. You see this done a lot by consumers and hams alike. Solar users are the worst offenders. It is done out of ignorance in what I like to say is Stuck Inside a 12 Volt Toy Box. For some reason folks get the idea 12 volt batteries are all there is. So if they need 12 volts at say 300 AH, they buy 3 x 12 volt 100 AH batteries and configure them 3P. What did not occur to them or knew is to use either 6 or 4 volt 300 AH batteries wired in series. You can buy Pb batteries that range from 6 AH to 6000 AH. Once you get above 1000 AH you would be using 2-volt batteries. The reason why you do not want to parallel Pb batteries is you cannot match and balance resistance of the cables, connectors, and the internal resistance of the batteries. It is impossible. The result is unbalance charge and discharge currents in each string. The string with the lowest resistance does most the work. End result is you have one string over charged and one undercharged. Both are unnecessary stress on the battery and wear them out from either corrosion or sulfated plates. There is only one application where you can get away with parallel battery operation and that is Emergency Standby Float Service where the batteries are rarely or ever cycled (used). Example a large telephone offices, or where a ham radio operator uses his DC power Supply with backup batteries in the event of a power outage. Bottom line is there is no need for most to use parallel batteries. If you need or want 250 AH batteries, buy 250 AH 6-volt batteries. 6 volt batteries run from 175 to 400 AH. In 12 volt batteries about as large as you can handle is 150 AH before weight becomes an issue and why you cannot find larger than 200 AH if your back can handle it. Charging On to charging and where things can get off track real quick. Very few folks understand how a battery charger works and how to properly use them. Manufactures make it confusing with marketing terms that are mostly nonsense you see in so called Smart Chargers. All chargers worth having are very simple DC power supplies with Current Limit and Voltage Regulator. Such a charger provides Constant Current up to the voltage set point at which time becomes Constant Voltage aka CC/CV. In addition some of the Smart Chargers have a processor that can change voltage set points when thresholds are met. One of the most common questions I see is from folks who ask why when they set them to 14.4 volts, connect the battery, and see a voltage of 12.something volts? Answer is simple Ohms Law and how all power supplies work with current limiters. It all has to do with the Battery Internal Resistance (Ri) and the batteries Open Circuit Voltage (OCV). If you buy say a 10 amp battery charger, at most can only deliver 10-amps which is controlled by the Current Limiter. So as an example say we have a 12 volt 100 AH battery with an Ri = .01 Ohms, and the battery OCV = 12.1 volts or 50% State of Charge (SOC). We set the Charger to 14.4 = Bulk and Absorb and connect it to the battery. What voltage will we see? Battery Under Charge Voltage = OCV + (Ri * Charge Current) 12.1 volts + (.01 ohms * 10 amps) = 12.2 volts. As the battery charges the battery voltage will rise and current will remain Constant 10 amps until the battery voltage reaches 14.3 volts. At 14.3 volts begins the Absorb Phase where current starts to taper off toward 0 amps. At this point the Constant Voltage stage begins and where the Voltage Regulator holds 14.4 volts. When current tapes to 3% of C (3 amps on a 100 AH battery) is where the battery is considered Saturated and you can either Terminate the charge, or some chargers will lower the Voltage to 13.6 to 13.8 volts (Float) depending on battery requirements. Float voltage is just another voltage set point and is a Constant Voltage up to 10 amps. Take away with chargers, is there is no magic. They are simple DC power supplies with a current limiter, voltage regulator, and some offer some processing that changes voltage set points when events are triggered. So what do you look for in a charger? 1st and most important is the charge current rating. FLA batteries have a minimum requirement of C/12 to prevent electrolyte stratification when the heavier acid settles to the bottom of the jar and the water floats on top. C/12 will provide enough agitation to stir the electrolyte. There is no reason to go above C/6 as that can cause unnecessary heating and extended gassing voltage by spending too much time in the Absorb phase which is at the gassing voltage threshold. The magic number is C/10 which is perfect and provides the fastest possible charge. Charging faster than the C/10 rate gets you to Absorb much sooner, but extends Absorb time and you have reached the point of diminishing returns. What voltage do you want to charge too? There is no correct answer and only your temperature corrected hydrometer can tell you. You start with the manufacture recommended voltage window which is usually 2.35 to 2.45 volts per cell. You complete a charge cycle, and take a hydrometer reading. It is low turn up the voltage, if high relax the voltage. Pb batteries have two failure modes. 90% of deep cycle batteries are from sulfated plates from chronic undercharging. The remaining 10% are from natural aging and over charging (corrosion). You want to error on the side of slightly over charged. Keep Pb batteries at 100% SOC at all times and immediately recharge after any use. As for what kind of charger you select depends greatly If you chose FLA or AGM. For FLA you will want one with an Equalization Charger sometimes called a 4 Stage charger of Bulk/Absorb/Float/EQ. AGM do not require EQ charges. Just make sure whatever model you get has adjustable voltage settings. Battery Recommendation As for battery brands two come to mind and they offer mid and high end models at fair price points. My favorite for FLA is Trojan, and they have 3 quality levels of mid, high, and best called respectively Signature, Premium, and Industrial. The T-105 is a very solid mid entry level 6-volt 225 AH golf cart battery (2-year warranty. They also make a T-105RE called SPRE 05 255. Same case and capacity of the T-105 that has 5 pounds more lead and a 5 year warranty. Their Industrial line is pricey, large, and a 10 year warranty. Another FLA good quality battery and a little less expensive is US Battery 6-volt line up and Renewable Energy Lineup. Many models to choose from. For AGM the best of the best is Concorde. They invented the AGM battery for military aircraft. There high end line is Sun Extender PVX series. They are pricey but they also make a mid-end line called Lifeline Marine batteries. Another very good AGM is Odyssey. Hope that helps and you gained some information.