PINNED - AGM & GEL battery info lead battery info

[martin007]

or whatever gives a 6 to 8 hour CV length in tests.

In which menu is this set?

[Burgerman]

The thing that determines the CV length of time is the termination current...

Watch.
This battery is already charged. It taks a few seconds here and not 8 hours bcause the battery is already full. I cant video a full 8 hour deep cycle charge!

So the cv voltage is instant. Set to 28.2V in this case.
After a few seconds it drops to a low current of 0.2A because battery is full already. Then FLOAT (27.2V) starts. That low current is what you set to make it go to float after say 6 to 8 hours. The BATTERY decides the current after 8 hours.

Mine needed to be set to 0.2A in order to get an APROX 8h CV charge on a deeply discharged battery. After 8 hours it reached (fell) to the target current that I set, 0.2A, so changed TO FLOAT automatically. Since this battery is full already it does this in just 1 minute.

https://www.wheelchairdriver.com/doomed/3stage.mp4

[martin007]

OK.


I have to experiment...

[ex-Gooserider]

In my studio I have a ZXD set to 28.8V and 25A max, and I plug in any time I've done much distance, but often only for a few minutes at a time, sometimes up to a couple hours...

Batteries are old Odyssey re-brands that are near end of life judging by how fast they drop LED's on the joystick...

The current when I plug in varies, depends on how much running around I've done, can be as much as 25A, or as little as 2-3A... It drops off fairly fast to under 1A.... Do I need to worry about unplugging at that point or can I leave it? I don't have any indication that it's dropping to float, but I'm also not positive about whether I'm in 3-stage or CV-power supply mode....

ex-Gooserider

[Burgerman]

Odyysey state that 8h CV stage at 14.4 to 14.7V is the max you should do. So watch it, ignore the CC stage. After a DEEP CYCLE of 25% or greater depth, it will take around 8 hours to achieve a full charge. After this float wont hurt but isnt needed.

They actually say 1000thC termination, or 8 hours CV whichever occurs first in cyclic use.

If its only very lightly used, a few Ah, then it should automatically drop to the point where it switches to the 3 stage lower voltage. On my optimas that are old now, thats around 0.1A as set on my ZXD. If you are using 3 stage, float finishes the charge slowly anyway, so setting to 0.2 or even 0.3A garantees that it does in fact end.

[mattross]

I have an Invacare Storm 4 with some nearly dead MK Gel batteries in it. Recently I bought a Victron 24V charger (13A, IP22 version) to use as a secondary charger to my ZXD2400 (primarily for this backup chair). I have it configured for the same recommended charge profile as the ZXD2400 and it is charging these nearly dead batteries to some degree. However, as the batteries are now very poor (21.6V before charging according to my multimeter), the voltage immediately jumps to 28.2V and the batteries only pull about 2A initially, and drop below 1A in about a minute. This is enough to make the chair work for a few days, but then it will lose drive again.

Now to my question. The Victron charger has a 'recondition' mode where it can force a configurable higher voltage to try and desulfate deeply discharged batteries. I have not tried it as I don't know how the chair itself might handle the extra voltage, which by default is set to 32.4V, if enabled. Would I be risking the chair by using this mode? I am replacing the batteries, but need it to continue working a little longer.

[Burgerman]

I have it configured for the same recommended charge profile as the ZXD2400 and it is charging these nearly dead batteries to some degree. However, as the batteries are now very poor (21.6V before charging according to my multimeter), the voltage immediately jumps to 28.2V and the batteries only pull about 2A initially, and drop below 1A in about a minute. This is enough to make the chair work for a few days, but then it will lose drive again.

This is all about resistance.
If I set the ZXD to say 28.0V and charge healthy batteries at 30A setting they will only charge at that rate with short, heavy 10sq mm cables and anderon connectors. If I choose longer wires, or thinner cables, then it might start at 40A for a couple of minutes then it drops away.
This is because the differemce of actual battery voltage and charge voltage while actually on charge may only be a few 10ths of a Volt.
But this resistance can also be in the battery... And with old or badly maintained batties it usually is.

Now to my question. The Victron charger has a 'recondition' mode where it can force a configurable higher voltage to try and desulfate deeply discharged batteries.

When you DISCHARGE a battery that very action turns the sulfuric acid in the (water and sulfuric acid) electrolyte into lead dioxide and lead sulfate. This coats the plates with a super fine "dust" coating covering all of the active particles. And leave the electrolyte closer to water. Which doesent conduct...
That sulfate coating, if left more than a few hours gradually begins to turn into large non conducting crystals. Called "permanant" sulfation for a reason. You cant force that to conduct by adding a little extra voltage.

As you charge normally, that coating of lead dioxide and lead sulfate is returned back to the electrolyte and forms the sulfuric acid. If you do not continue a charge to the point where the battery is 101% fully charged, as in put back MORE energy than was ever used, then some of this is left behind every charge. Which turns permanant over time.

RECONDITION on a gel battery is harmful! The correct way to return the sulfation back to the electrolyte is to charge FULLY. If that doesent work nothing else can. Charging IS desulfation. Although most chargers dont do this properly.

Charging at an elevated voltage as a mobility charger does or a if you choose "recondition" causes gel shrinkage and eectrolyte loss through gassing and voids in the gel. As it gets dried out... So the answer is a LONG charge to try and desulfate a lead battery and LOWER float voltage maybe weeks or months. But your high resistance is likely due to the active material being used up, plate distortion, gel shrinkage and electrolyte loss as well as sulfation. And unwanted chemical reaction from impurities in the materials.

I have not tried it as I don't know how the chair itself might handle the extra voltage, which by default is set to 32.4V, if enabled. Would I be risking the chair by using this mode? I am replacing the batteries, but need it to continue working a little longer.

Your battery is long past help.
Chair wont care.

Instead set the ZXD to charge as a supply. At max 27.4V and a max of 0.5A and leave it for a month.

[mattross]

Okay thanks, I won't be enabling recondition and will just wait for replacement batteries instead. I need to move the chair around daily as it is always in the way in a small room, so can't leave it charging permanently without disabing the third XLR pin.

[Burgerman]

Thats OK. Just replug after you used it. Or snip it. Theres a connection between negative and the 3rd big pin we dont need... As long as you dont forget.

[Frank]

Hello there, I need to replace the batteries (Eternity technologies G06 12 066) of my Quickie wheelchair Q700R. Should I replace them with the same batteries or are there better brands like MK batteries?

[Burgerman]

Those batteries are very high quality gel. They are actually the very same as the Haze GEL (not AGM) batteries that you can find on eBay.
https://www.ebay.co.uk/itm/130633616407

So you should get either of these two. The Eternity and the Haze are identical internally and made in the same factory.
Both perform better than the MK does, slightly.
Best to charge with:

20% of capacity (20A approx max)
2.35 V per cell (8 hours approx or until around 0.3 to 0.35A is reached)
Float at 13.5V per 12V battery.

https://eternitytechnologies.com/wp-con ... .08.22.pdf

Or for less money go lithium. And that will cost less. give you 20+ years of use, 5 to 6 times the range, charge faster, less weight, but need a steep learning curve and some DIY work...

[Frank]

Thank you for the information and Happy Holidays.

[shirley_hkg]

Again. What's the voltage (Gel) for infinite float please.

[Burgerman]

13.3 to 13.35V indefinitely. 20 to 25 Centgrade.
That will charge it too. But will take maybe a week or more to 100%.

[shirley_hkg]

Bought a pair of 85a GEL (5.8mΩ), for £105. Drove it for an an hour, and recharged .

Firstly, would you estimate how much did I consume for the ride?
Part of the Ah returned are wasted as heat.

Secondly, CV lasted 7+ hours, before switching to float. Now it is still higher than 27V, 4 hrs after leaving CV. That voltage seems too high with me. It used to drop to around 26.6v.

Is the absorption period too long?

[Burgerman]

Bought a pair of 85a GEL (5.8mΩ), for £105. Drove it for an an hour, and recharged .

Thats very high IR and will mean long slow charge times.

Firstly, would you estimate how much did I consume for the ride?
Part of the Ah returned are wasted as heat.

You cant estimate. Energy wasted not only in heat but in converting water into oxygen/hydrogen and then converting it back too... And even rechargeing (converting lead dioxide and lead sulfate back to sulfuric acid isnt 100% efficient either. Not just resistance losses.

Secondly, CV lasted 7+ hours, before switching to float. Now it is still higher than 27V, 4 hrs after leaving CV. That voltage seems too high with me. It used to drop to around 26.6v.

Is the absorption period too long?

No. Look at it like this.
The only really accurate safe way to charge a lead battery fully, and with least cycle damage is at float. A few mV above the normal resting voltage. That takes several days minimum.

The only way to fuly charge on true cyclic use (where a recharge has to happen in a single 8 hour overnight shift in say airport floor cleaning machines etc) is to charge at elevated voltage and estimate when its full... Say 14.4 to 14.6V. That damages cycle life. And you never really know. In order to actually get a battery 100% full at all really needs whats called a "fast finishing" stage. Which means stopping the CV stage early at say 1 or 2A and then adding x amount of time at a fixed current of 1 or 2 amps. And try not to look at the voltage go through the roof.

So whats best?

That all depends on how long you have. Time.
So to reduce error, we do a happy medium. We charge in cyclic use at a slightly elevated voltage 14.1V on gel.
(Where 14.4 = fast with greater loss of cycle life and 13.6 float charge = long charge time, of maybe 16 to 48 hours, and best cycle life)
And we end EARLY at 8 hours CV and allow a float of 13.6 to complete the charge. To avoid overcharge.

So no even 12 hours at CV is fine as long as its not a HIGH CV.

SEE here:

https://www.wheelchairdriver.com/MK1.pdf

[Burgerman]

Also that timer does not set a FLOAT voltage time alone. It sets how long the battery stays at the CV voltage you choose before it kicks back in to continue topping it up. So you can set that at say 15 mins if needed. It will then drop to your float voltage and if that takes less than 15 mins it will restart the CV stage over and over. So actual float will only start much later when it doesent keep kicking back to CV stage.

What I tend to do is set it as a power supply. Set 14.1V at room temp, (28.2 on a chair) and put on charge at midnight. Turn it off when I get up in the morning or reduce volts to 13.5 (27.0) if I intend staying on my bed. That tops it off and garantees a 100% charge over the next 24 hours.

You can only charge a lead battery in 8 hours if you do a controlled overcharge in 8 hours. And it will end up under or over charged.
You cant charge full, in under 16 hours in cyclic use because thats just how long full absorption takes at safe voltage levels that dont ruin cycle life.

[shirley_hkg]

It entered CV in less than an hour, and current was 1.1a in another 3 hrs.

Took another 5 hrs to reach 0.45A, before switching to float.

It just sit there over 6hrs, waiting to reach 27V.

[Burgerman]

You plug it in. Set it to charge at what Amps? It should go to whatever CV voltage you set or should draw whatever current you set while it does.

So not sure what you mean?

If it sits at whatever CV voltage you set, and draws a lower current than you chose, then the battery or the cables are too high resistance. Di it will take a long time to charge. Takes 12 to 16 hours to charge cheap high impedance lead. 8 to 10 hours to charge Odyssey low impedance batts...

Or do you mean its sat at 27V after CV and its not dropped to your float voltage yet?
If so thats a bit odd. Maybe your ZXD needs calibrating. Or the batteries are a bit strange! Could be just a surface charge. Give it time. Float isnt needed if they are actually full so thats normal if its OCV is that high. Is it still falling?

[shirley_hkg]

CV 28.18
CC 15.15
Trigger to float 0.45A
Float 27v
Float time 8.5 hrs.

Now it is 27v, 9hrs after CV ended at 0.45a .

[Burgerman]

Thats OK. Its either a battery that has a few impurities (a cause of high surface charge) or the calibration isnt very accurate on the ZXD. It will drop away in time. But float is really for maintainance. If its not needing extra time on float then it isnt!

It will at some point.

Read that MK gel info. It says float isnt needed on a properly charged battery. Unless for maintainance or if the CV end point is low enough current or long enough time. Full is full.