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What are the 3 Stages of Smart Chargers?

 Tech Tips & Tricks

You may have heard it said "you need a 3 stage charger." We've said it, and we'll say it again. The best kind of charger to use on your battery is a 3 stage charger. They are also called "smart chargers" or "micro processor controlled chargers". Basically, these types of chargers are safe, easy to use, and will not overcharge your battery. Almost all of the chargers we sell are 3 stage chargers.

Okay, so it's hard to deny that 3 stage chargers work and they work well. But here's the million dollar question: What are the 3 stages? What makes these chargers so different and efficient? Is it really worth it? Lets find out by going through each stage, one by one.

Stage 1 | Bulk Charge

Bulk StageThe primary purpose of a battery charger is to recharge a battery. This first stage is typically where the highest voltage and amperage the charger is rated for will actually be used. The level of charge that can be applied without overheating the battery is known as the battery's natural absorption rate. For a typical 12 volt AGM battery, the charging voltage going into a battery will reach 14.6-14.8 volts, while flooded batteries can be even higher. For the gel battery, the voltage should be no more than 14.2-14.3 volts. If the charger is a 10 amp charger, and if the battery resistance allows for it, the charger will put out a full 10 amps. This stage will recharge batteries that are severely drained. There is no risk of overcharging in this stage because the battery hasn't even reached full yet.

 

Stage 2 | Absorption Charge

Absorption StageSmart chargers will detect voltage and resistance from the battery prior to charging. After reading the battery the charger determines which stage to properly charge at. Once the battery has reached 80%* state of charge, the charger will enter the absorption stage. At this point most chargers will maintain a steady voltage, while the amperage declines. The lower current going into the battery safely brings up the charge on the battery without overheating it.

This stage takes more time. For instance, the last remaining 20% of the battery takes much longer when compared to the first 20% during the bulk stage. The current continuously declines until the battery almost reaches full capacity.

*Actual state of charge Absorption Stage will enter will vary from charger to charger

Stage 3 | Float Charge

Float StageSome chargers enter float mode as early as 85% state of charge but others begin closer to 95%. Either way, the float stage brings the battery all the way through and maintains the 100% state of charge. The voltage will taper down and maintain at a steady 13.2-13.4 volts, which is the maximum voltage a 12 volt battery can hold. The current will also decrease to a point where it's considered a trickle. That's where the term "trickle charger" comes from. It's essentially the float stage where there is charge going into the battery at all times, but only at a safe rate to ensure a full state of charge and nothing more. Most smart battery chargers do not turn off at this point, yet it is completely safe to leave a battery in float mode for months to even years at a time.

 

It's the healthiest thing for a battery to be at 100% state of charge.


We've said it before and we'll say it again. The best kind of charger to use on a battery is a 3 stage smart charger. They are easy to use and worry free. You don't ever have to worry about leaving the charger on the battery for too long. In fact, it's best if you DO leave it on. When a battery is not at a fully charged state, sulfate crystal build on the plates and this robs you of power. If you leave your powersports in the shed during off-season or for vacations, please connect the battery to a 3 stage charger. This will ensure that your battery will be ready to start whenever you are. Use the link below to browse our selection of smart changers and 12v/24v trickle chargers.

Choose your Smart Battery Charger


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27 Responses

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  • So I recently installed my 3 stage charger into my LiFePO4 battery bank in my RV. When I plug it in, initially, the charger works as it should through all 3 phases. But once it gets to phase 3, and I'm using my batteries, it won't go back to stage 2 or stage 1... I have to physically unplug the charger and presto is starts back in the phase I need based off the condition of the battery? I'm using a PowerMax 30A charger. Am I doing something wrong? Is it faulty? Is it not designed to go backwards? If it's a smart charger, and I'm using my batteries, shouldn't it be able to pick up the condition of my battery usage and charge accordingly?
    Nathan
    May 11, 2020 a 3:41 pm
    • The PowerMax's are designed for lead acid batteries, so their charging profile is meant for those batteries out of the box. The charger may be capable of charging lithium batteries initially, but for maintenance purposes it may have issues restarting the charging cycle. The reason is lithium's sit at a higher voltage than lead acid batteries, so in affect it doesn't know when to restart the charging cycle for your batteries. In an RV this probably isn't going to be a big issue as they PowerMax acts as a power-supply when pluged in, so amperage is supplemented by the unit as request are needed. When you unplug and plug into shore power it will complete a charge cycle, but for long-term maintenance charging you should talk to PowerMax about adjusting the profile. The PowerMax voltage can be adjusted in the field in order to customize the charging profile. You may have to work with your battery manufacturer and PowerMax in order to customize the charger to work correctly with your batteries.

      Tech
      May 21, 2020 a 7:38 am
    • This is very useful, but i have a 4 stage charger and i wonder what the 4th stage does. Please help explain the 4th stage.

      Paul
      January 13, 2017 a 1:49 am
      • There is no black and white answer, as it really depends on the manufacturer, and what they consider a stage to be. Your best bet is to consult the manual for your charger, or contact the manufacturer.

        Tech
        January 16, 2017 a 2:00 pm
      • Great, thank you :)

        Hamed
        September 29, 2016 a 8:00 am
        • I hooked up my supercheap auto 7 stage charger to my lead acid battery and it has been in the “bulk” phase for 2 hours now. This is the first time I’ve needed to charge the car battery (I let the car sit for 2 months)
          The “faulty battery” light is not on, but I’m wondering if there really is something wrong?
          Any advice would be nice!

          Jonathon
          September 29, 2016 a 3:20 am
          • Car batteries generally start at about 50AH, so only being on a couple of hours could be normal depending on the level of the battery, and the chargers amp rating.

            Tech
            January 16, 2017 a 10:49 am
          • what should the absorption voltage be set up to? and the time? for AGM batteries

            Shabbir
            September 2, 2016 a 5:43 am
            • If you are looking for the charging profile for an AGM battery I would refer you to the manufacturer of the battery you are trying to charge. Most smart chargers have certain charging profiles built into them, but if they feel resistance they will reduce the voltage. However in a manual setup, I would refer to the manufacturer to be sure you program the charger to their specifications.

              Tech
              January 16, 2017 a 10:31 am
            • wow? ive been trying to find out why my battery is still stuck on float mode for 3 days now and wont go into pulse mode, now I know why, thank you for this info, its put my mind at wrest, I was told that it could take up to 10 days.

              Arthur Cowgill
              June 30, 2016 a 1:26 am
              • So i have a flooded deep Cycle marine battery.. I have a 3 stage smart charger. I can’t find any info on weather i should vent when charging. Also how do i tell when i need to add distilled water… Thanks a bunch

                Greg W
                June 22, 2016 a 12:26 pm
                • Generally there is no need to remove the caps unless you are checking the water level in the battery. Batteries today have vents built into the caps or the case to prevent gas build-up. As far as watering your battery I would consult with the manufacturer to be sure of the proper procedure… but generally there is a plastic inserts that go to the into the cells of the battery, and most have you fill the battery till the water just barely touches the bottom of the plastic insert.

                  Tech
                  January 16, 2017 a 9:43 am
                • very good information its helps for new buyer s

                  Vishu
                  June 7, 2016 a 9:30 pm
                  • Very simple , clear and communicating language. It’s really help full and informative.

                    Vikram Singh
                    June 5, 2016 a 2:01 am
                    • Just put a 3 stage 24v charger on my mobility scooter, plan on leaving 4 months. Any thoughts?  Without knowing all the details, as long as the system is a 24v system and the charger is sized correctly, should be good.

                      Scott
                      July 6, 2014 a 12:27 pm
                      • Thanx a alot
                        Gud info
                        Way 2 go frnd;)

                        Abdul Khan
                        May 12, 2014 a 9:42 pm
                        • Great explanation, was surfing around – this was the best I found. Thanks heaps, helps me with my RV charging issues.

                          Andrew Grant
                          April 12, 2014 a 4:42 pm
                          • I‘m just wondering if you can pull power while this is in use? Can I use lights(12v) and a water pump (12v) etc in this circuit without interrupting the charger?

                            Rob Moir
                            March 21, 2014 a 6:13 pm
                            • I now realize a charger is not just a charger but there are choices we should concider before buying.
                              very good explanation, thank you.

                              Frank
                              December 27, 2013 a 3:06 am
                              • Exactly what I was looking for. Thank you.

                                Igor
                                December 9, 2013 a 9:57 pm
                                • Testing nesting

                                  Dan B
                                  February 27, 2017 a 8:43 pm
                                • very impressive article with visualization thanks a lot

                                  Kamal
                                  November 12, 2013 a 9:40 pm
                                  • Simple and informative. Very good explanation.

                                    Thanks a lot :)

                                    Sharat
                                    September 22, 2013 a 3:36 pm
                                    • Very nice article… informative…!!! thanks!!!

                                      Venuu
                                      April 15, 2013 a 10:41 am
                                      • Glad you found it usefull! :)

                                        Jeremy Fear
                                        April 15, 2013 a 11:58 am
                                      • Very useful information
                                        Thank you.

                                        A L Laoye
                                        February 8, 2013 a 8:21 am
                                        • You‘re welcome. Thanks for reading our article.

                                          Tech
                                          February 8, 2013 a 10:22 am
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