The charger delivers 24 amps.... will it charge each cell with 24 amps? Or will the amps be shared over the cell´s, delivering 6 amp charge to each cell?
My problem is, that I connected 6 new chargers, 6v, one to each cell, charging 4 amps. This seems to work great, but I now have my doubt´s if I am charging alot slower than the old setup.
If problem gets big, with charging time. I just needa buy bigger chargers, and make new setupHy SimomTHK,
Your old arrangement was charging each battery at 24A and your new charger will be charging each battery at 4A, which means that the batteries will take six times longer to charge. But having a charger for each battery is a much better arrangement because the voltage across each battery is controlled independently according to the needs of each battery.
If you are not worried about the long charging time that is fine. The batteries would be very happy about such a light charge. If you want a fast charge, six 20 Amp chargers would be ideal.
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The are flooded cell.SimonTHK ,
Are your batteries flooded-cells, or are they AGMs?
Are you drawing load current from a tap between the series string of 18 cells, or is the load connected only to the entire string?
If problem gets big, with charging time. I just needa buy bigger chargers, and make new setupI just liked them 4A, small, cozy, silent, cheap chargers.
Thank you that is great to know. I believe for the better charging of each cell (6 chargers), I have an advantage vs the 24 amp quick charge.. The old setup was overcharging some cell´s and some didnt follow in voltage. Some cell´s might have reached high voltage very quickly, tus turning of the 24 amp charger. So for now, the slow charge, might give me more anyway
It does seem that my old 24 amp charger does have some off switch when reaching 40 - 41v. Now I havnt used much time on this project at all, so I dont know all details of the charger, but it does turn off.
Generally, as I am working with these kind of cell´s often, and getting more experience. I run into the problem of cells charging very differently, when put in series with 1 charger, and can cause alot of damage. I work with electric bycicle, scooter, etc etc, all kind og electric transportation. Customers quite often seem to change whole battery packs, as when only 1 is damaged, and the cell´s just get damaged way to often, when put in series.
In my experience it can cause:
-Charger never to turn off.
-Charger to turn off too early.
-Overcharging of some cell´s.
-No charging of other´s.
-One damage or worse cell, damage other.
So I like the idea of microprocessor controlled charger´s on each battery. Also it should give give the possibility to only change 1 damaged battery, because they are not dependant of each other´s simultanously internal resistance (or whatever is going on). Atleast not for charging.
Most chargers have a fuse which would take care of that situation.If you want to charge 6 batteries with 6 chargers while they are still connected in series there is one very important thing you need to make sure, and that is the charger outputs must all be isolated from each other, if for some reason the charger - o/p is connected to ground then you'll short the batteries out.
Flooded-cell deep-cycle batteries, like the ones in my 36V golf cart, are designed to be "equalized" by charging the entire sting of 18 cells in-series. These batteries will tolerate a moderate overcharge, so by passing the same current through all 18cells at once, and going a bit past the point where the first cells reach full charge, the weaker cells are brought up to the correct Specific Gravity.The are flooded cell.
I have seen golf carts that have 12V lighting (headlamps, tail lights, brake lights, maybe an entertainment radio) which is tapped six cells up from the ground end of the 36/48V string, but this added load on the lower six cells always unbalances them relative to the upper 12 cells, and makes it difficult to equalize the string. Here is a case where you might be tempted to use two chargers, or properly fix the problem by using a buck converter to reduce 36/48V to 12V, and then use a single charger...I dont understand your last quistion. Why you say 18 cells, it must be because each 6v pack, contains 3 cells? The load is if I understand you correct, drawing current from the entire string. The string of cells are together 36v, and the controller is 36v.
Normally I would never take power from in between a string. Last week I changed a setup that lowered speed of a motor by running over half the battery pack, to using an intelligent controller S-drive.
So I like the idea of microprocessor controlled charger´s on each battery. Also it should give give the possibility to only change 1 damaged battery, because they are not dependant of each other´s simultanously internal resistance (or whatever is going on). Atleast not for charging.
Flooded-cell deep-cycle batteries, like the ones in my 36V golf cart, are designed to be "equalized" by charging the entire sting of 18 cells in-series. These batteries will tolerate a moderate overcharge, so by passing the same current through all 18cells at once, and going a bit past the point where the first cells reach full charge, the weaker cells are brought up to the correct Specific Gravity.
As I said in my earlier post, the chargers made for this application accomplish an "equalization" during each re-charge cycle, where the first cells to reach full charge are a bit overdriven so that the weaker cells in the string also come up to full-charge. As long as you add water periodically, these batteries last a long time used this way. This method is used in golf carts, forklifts, scissor lifts, etc...
I think it is a mistake to use six independent chargers. Since each battery has three cells, you are still dealing with the equalization cell by cell, but only three cells at a time. You haven't eliminated the need for it, just made it harder to manage...
I have seen golf carts that have 12V lighting (headlamps, tail lights, brake lights, maybe an entertainment radio) which is tapped six cells up from the ground end of the 36/48V string, but this added load on the lower six cells always unbalances them relative to the upper 12 cells, and makes it difficult to equalize the string. Here is a case where you might be tempted to use two chargers, or properly fix the problem by using a buck converter to reduce 36/48V to 12V, and then use a single charger...
These are typical of the batteries used in golf carts, and happen to be the ones in mine...
Typical battery charger (made by Lester) for the batteries above... I have a schematic of one like this if it comes to it... The timer in one I have crapped out, and I built my own using an Arduino....
Many modern chargers monitor charging current, and switch modes when the charge acceptance reaches certain limits......Battery charging, with all types of battery, is based on battery voltage not current (the current is limited though)...
You have also just made the case for individual chargers.One major oversite in that theory. You are not factoring in discharging rate and energy stored per battery or per cell which will vary greatly between an older battery and a new one and when the load is drawing from all of them in series the ones with the lowest Ah will go dead first and very likely be run in reverse until the higher capacity cells drop off far enough for the system to shut down.
With large multicell battery systems as little as a 5% differnce in Ah between the highest and lowest capacity cell is enough to start doing damage to the whole battery set as its being used and recharged.
Simply put if one battery has a bad cell it it has just as much effect on the discharge and subsequent energy consumption rates from all the other cells as it does in the charging mode.
Your theory of only changing out a bad battery in the set still causes major problems in the end hence the rule of if one battery goes bad all batteries get replaced thusly with your multi charger setup you have in fact gained nothing but made the whole process slower and overly complicated for no good reason or long term measurable gains.
If I was dealing with a 36 volt 200 Ah battery bank I would have went with a single properly sized 36-volt smart charger instead of six 6-volt chargers.
Why? The batteries in my golf cart are over ten years old, and still going strong. The secret is replenishing electrolyte, not allowing the batteries to sit discharged, be cognizant of self-discharge in hot weather... Why try to fix something that isn't broken?You have just made the case for using independent chargers.
I'm not sure what you are saying here. If you charge a battery at a constant current of say C/10 and pay no attention to the battery voltage you will either boil off all the electrolyte or the battery will explode.Many modern chargers monitor charging current, and switch modes when the charge acceptance reaches certain limits...
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