LOW BATTERY ERROR

[laoshanren]

My chair keep shown 'low battery' when the V= 23.5 V, the voltage got 26.5 just a short while charge . Is the battery bad, or can setup to eliminate this by software ?

Thanks

[Burgerman]

Battery is bad. Most likely.

[laoshanren]

Battery is bad. Most likely.

one of them can be charged up to 13, and the other one 12.4, not sure bad or not?

[Burgerman]

You dont charge a battery UP TO a voltage. You charge a battery AT a specific voltage.

You charge gel at 14.1V per battery. And AGM at 14.4V per pattery. You do this for around 12 to 16 hours. Or until current falls to a very low level (1000th of capacity). Then its charged.
The measured voltage will vary over time with a healthy battery.

Straight after charge, it will fall rapidly from around 13.6 to 13.2V. then it gradually drops to 12.85V (agm) or 12.9 to 12.95v (GEL).

I suspect both your batteries are

[laoshanren]

You dont charge a battery UP TO a voltage. You charge a battery AT a specific voltage.

You charge gel at 14.1V per battery. And AGM at 14.4V per pattery. You do this for around 12 to 16 hours. Or until current falls to a very low level (1000th of capacity). Then its charged.
The measured voltage will vary over time with a healthy battery.

Straight after charge, it will fall rapidly from around 13.6 to 13.2V. then it gradually drops to 12.85V (agm) or 12.9 to 12.95v (GEL).

I suspect both your batteries are

Thank you.
Very good advice. I used a smart charger to charge the batteries, the Quantum charger doesn't go far as long as the PAD shown 100%. or as long as the green led ON.

[laoshanren]

You dont charge a battery UP TO a voltage. You charge a battery AT a specific voltage.

You charge gel at 14.1V per battery. And AGM at 14.4V per pattery. You do this for around 12 to 16 hours. Or until current falls to a very low level (1000th of capacity). Then its charged.
The measured voltage will vary over time with a healthy battery.

Straight after charge, it will fall rapidly from around 13.6 to 13.2V. then it gradually drops to 12.85V (agm) or 12.9 to 12.95v (GEL).

I suspect both your batteries are

Search online the smart charger can recover many batteries, not sure if OK for gel.

[Burgerman]

Snake oil. A smart charger cannot recover anything other than a battery that needs charging. And most so called smart chargers are big on marketing and dont charge anything properly.

If your chargers are working, and one battery is below 12.9V after charging, before use, then the battery is faulty. Or just worn out.

[laoshanren]

Snake oil. A smart charger cannot recover anything other than a battery that needs charging. And most so called smart chargers are big on marketing and dont charge anything properly.

If your chargers are working, and one battery is below 12.9V after charging, before use, then the battery is faulty. Or just worn out.

Is it possible to config the warning threshold? It warning at 23.5 V now.

[Burgerman]

A battery that reds 12.0V (24V) is already dead. You will be going nowhere.

[laoshanren]

A battery that reds 12.0V (24V) is already dead. You will be going nowhere.

That means the battery effective scope of use is only from 12 V to 12.9 V, can this let the chair run 10 miles even more accord to the manual?

[Burgerman]

A FULLY charged battery is 12.85V or up to 13.15V. The difference is just a surface charge and as soon as you begin moving it will be under 13V.

A battery that is 80% discharged, which is as low as you can go without damaging the battery quickly, is around 12V. The wheelchair will begin warning you if you go below this because you should not be doing so. In any case 11.7V is where the chair will stop due to a mixture of increased resistance due to battery being discharged, and peukert, meaning the surface charge and voltage depression is below that needed for safe control.

So yes. 12.95V to 12.00V is about the range between full and fully empty. For sealed deep cycle batteries that we use. You may see chargts for wet batteries that show slightly different voltages. But the gel/AGM chart here is correct. And is what your chair is calibrated for. Thats correct.

Do NOT discharge to 80% unless you want to rapidly kill the battery. In any case, the chair will not operate below 11.7 volts due to increased internal resistance.

TYPICAL SEALED AGM DEEP CYCE SEALED BATTERY STATE OF CHARGE TABLE

A few mins after this point the chair STOPS. The battery is TEMPORARILY exhausted. There's still around half of its real Ah left. IF you wait 24 hours for the voltage to recover. Then you may get an extra mile. Then it stops again. Rinse and repeat several times (days) and you will be able to discharge to 70 or 80% total. This is because of something called Peukert. Which says that the capacity reduces the faster you remove power from it. And it partially recovers over time.

[Burgerman]

That means the battery effective scope of use is only from 12 V to 12.9 V, can this let the chair run 10 miles even more accord to the manual?

Yes. But only in theory...
In reality, you will only see about half of that predicted range claim. Because they measure range with the ISO test. Which is unrealistic. The so called 'tenis court test'. This is calculated from power used driving a set course, for a few laps only. Then the actual range is calculated based on the 5 hour discharge rate capacity. It results in a completely unrealistic range figure. And one that will destroy the battery. You will see a real world range figure of around HALF of the claimed range. So 5 miles? And this depends of terrain, route, weights, hills, turning, etc.

And this depends on the battery being brand new. Since actual capacity and range deteriorate from the first few weeks, until the battery has completed its 350 to 400 cycles. Then its done and destroyed and needs to be replaced.

That 350 to 400 cycles, also depends on keeping average discharge level away from that 12.0V lower end...
It also depends on CORRECT charging, which your mobility or smart charger DO NOT DO.

So in reality your 5 miles becomes 3 and then 2, and as soon as it begins to deteriorate it accelerates the problem ever faster.

This is why you need a chair with CORRECTLY CHARGED (not by a smart or mobility charger) high quality deep cycle batteries, such as MK gel, or Odyssey of around 70Ah. Or better still Lithium Ion Phosphate of around double this Ah. And a GOOD charger.

[Mechniki]

I took my Roma into Dorking a couple of weeks ago, when I needed help fitting new hand grips to my night time (Action 3). I didn't have the strength to fit silicone grips to the hand rims. The wheels are fairly heavy. I took out one of the axles, so I could join the two wheels together. Carried them into Dorking mostly on top of my feet which obviously added more weight on the front of my chair and casters. I made it to a bicycle shop, where I got the silicone grips fitted.

I did a bit of nosing around Dorking, carrying the wheels with the newly fitted silicone. Before making my way home. I lost a single green of battery charge after an estimated 8 miles (2 x 55Ah AGM's). At that point I stopped and plugged in the LifePo4 into the XLR port, got the green light back. Made the rest of the way home (about 1.2 miles), without losing the power. When I got home, it took 4 hrs to recharge the AGM's,(left chair for 48hrs of charge) (I switched to my Spectra chair) the Lithium's had discharged to 25% but it didn't take too long to recharge them to 70%. (they were at 70% charge when I plugged them in to the XLR - I store them at 70%). I hadn't considered that I may need them, hence they weren't fully charged. But I did charge them to 100% this time, and can leave them plugged into the XLR fully charging them took nearly 3 days. But I am glad I had them despite them being designed for a motorcycle with their own BMS. What I like most, is that because the batteries are in a backpack and are extremely light in weight I can use them on either chair. I will be adding an LED display for the Spectra so I know the Voltage of each battery before using the Lithium add on.

[scootntootn]

At that point I stopped and plugged in the LifePo4 into the XLR port, got the green light back. Made the rest of the way home (about 1.2 miles), without losing the power.

Are you able to run the chair WHILE charging?

[Burgerman]

When the lead battery runs low, connecting a higher voltage lithium, esp one thats fully charged, will then dump all the lithium power into the lead battery. So yes it will charge the lead as you drive. But that is absolutely the wrong way to do it.

Because you drain the lithium fast which it hates, and will possibly shorten the lifespan fast. But also because the lead suffers more from deep discharge, and gives less range because of the high peukert value.

The correct way is to begin with both batteries fully charged. And link them. Then as you drive the power initially comes from the lithium, and as you go further it starts to come from both. You hurt the lead and the lithium less, and get mote total range. Likewise they can be charged as one battery at 28.80V.

[Mechniki]

I'll try that, thanks BM

[laoshanren]

When the lead battery runs low, connecting a higher voltage lithium, esp one thats fully charged, will then dump all the lithium power into the lead battery. So yes it will charge the lead as you drive. But that is absolutely the wrong way to do it.

Because you drain the lithium fast which it hates, and will possibly shorten the lifespan fast. But also because the lead suffers more from deep discharge, and gives less range because of the high peukert value.

The correct way is to begin with both batteries fully charged. And link them. Then as you drive the power initially comes from the lithium, and as you go further it starts to come from both. You hurt the lead and the lithium less, and get mote total range. Likewise they can be charged as one battery at 28.80V.

Thanks.

One more question is my two GEL batteries dropped from 25.4 to 23.5 in 10 - 20 minutes, and charged from 23.5 to 26.5 in also short time say 20 minutes, is this normal ?

Actually I'm trying to mix the SLA lead acid and gel, they have almost same V, is that OK?

[Burgerman]

One more question is my two GEL batteries dropped from 25.4 to 23.5 in 10 - 20 minutes, and charged from 23.5 to 26.5 in also short time say 20 minutes, is this normal ?

Yes,and it means little. It beccause of something called surface charge.
If I take a brand new and just charged battery and start a car with it, it will use around 1Ah. So that battery is still full. But its voltage drops below 9V while cranking the engine and will then gradually rise over the NEXT 24 HOURS back to the fully charged voltage if you were to disconnect it and wait.
Likewise if I take an identical fully charger battery and take out 1A for 1 hour it will still read 12.9V... Both will have different voltages, and be equally charged.

Actually I'm trying to mix the SLA lead acid and gel, they have almost same V, is that OK?

No... In series at leat. You will destroy them while charging.
And in parallel, you can safely charge at the gel voltage, (14.1V max) and that will leave the AGM/sealed battery undercharged.

[laoshanren]

One more question is my two GEL batteries dropped from 25.4 to 23.5 in 10 - 20 minutes, and charged from 23.5 to 26.5 in also short time say 20 minutes, is this normal ?

Yes,and it means little. It beccause of something called surface charge.
If I take a brand new and just charged battery and start a car with it, it will use around 1Ah. So that battery is still full. But its voltage drops below 9V while cranking the engine and will then gradually rise over the NEXT 24 HOURS back to the fully charged voltage if you were to disconnect it and wait.
Likewise if I take an identical fully charger battery and take out 1A for 1 hour it will still read 12.9V... Both will have different voltages, and be equally charged.

Actually I'm trying to mix the SLA lead acid and gel, they have almost same V, is that OK?

No... In series at leat. You will destroy them while charging.
And in parallel, you can safely charge at the gel voltage, (14.1V max) and that will leave the AGM/sealed battery undercharged.

Thank you, I'll not use mix batteries.
One of my 22 NF GEL can only charged to 10.5 V, won't go higher, why? any thing wrong inside?

[LROBBINS]

any thing wrong inside?

Yes, probably a shorted cell. There's no resurrecting it.

[laoshanren]

any thing wrong inside?

Yes, probably a shorted cell. There's no resurrecting it.

Is this mean there is no short if be able to charge over 11V?

[Burgerman]

You can charge any battery or cell to more than its correct voltage. It doesent mean its any good.

If you charge a single 12V battery correctly, it will read 13.4V approx directly after charge. This will fall over a few days in a ever slowing amount until it reads around 12.95V. This is all the same 100% full. If you wait a few weeks, it will read around 12.85V and still 100% full.

If after charging your battery is less than these figures. Its ruined. Permanantly. It may be 1 cell thats bad, or 3 that are not as good, or whatever. It doesent matter. Its only fit for the bin.

Also even if the voltages read as above, that still does not mean the battery has the ability to deliver any real current. It may be high resistance. So if voltage falls a lot under load it is still junk.

Also... Even if the volts are as above. AND the battery can deliver enough current to drive the chair, it may be severely lacking Ah, and so have very little range.

The reality is that unless the battery is under a month old (use) then it will already show at least some of the 3 issues above to small levels. And this gets worse over time.

[laoshanren]

You can charge any battery or cell to more than its correct voltage. It doesent mean its any good.

If you charge a single 12V battery correctly, it will read 13.4V approx directly after charge. This will fall over a few days in a ever slowing amount until it reads around 12.95V. This is all the same 100% full. If you wait a few weeks, it will read around 12.85V and still 100% full.

If after charging your battery is less than these figures. Its ruined. Permanantly. It may be 1 cell thats bad, or 3 that are not as good, or whatever. It doesent matter. Its only fit for the bin.

Also even if the voltages read as above, that still does not mean the battery has the ability to deliver any real current. It may be high resistance. So if voltage falls a lot under load it is still junk.

Also... Even if the volts are as above. AND the battery can deliver enough current to drive the chair, it may be severely lacking Ah, and so have very little range.

The reality is that unless the battery is under a month old (use) then it will already show at least some of the 3 issues above to small levels. And this gets worse over time.

Thank you.

I rescued 6 of GEL batteries by my DIYed 16KHz charger, and 4 of them works well for now. nearly all of them have 0.5 - 3.5 V originally cause of they wasn't touched for a long time say few years. The other two can only charged to about 10.5 V, don't know why?

[Burgerman]

Rubbish. Any lead battery sat at 10V or less for more than a week is ruined regardless of any amount of messing about with it. Depending how long = HOW ruined...

You CANNOT desulfate or repair any battery THAT IS PERMANANTLY SULFATED, or that has used up its active plate material, or that has internal corrosion, plate swelling or distortion, internal shorts etc by pulses, frequencies or any other means. Thats all snake oil.

You can remove some non permanant sulfates back to the acid, if its a healthy battery that has beel discharged for a long time if you are lucky by a very long slow charge over a few days at a controlled voltage /current. The act of charging IS desulfation. But it will never be as good as it was. And probably junk. And non of this can be determined by measuring voltages. I have a bunch of completely knackered batteries here that are all sat on the shelf at 13.0V.

[laoshanren]

Rubbish. Any lead battery sat at 10V or less for more than a week is ruined regardless of any amount of messing about with it. Depending how long = HOW ruined...

You CANNOT desulfate or repair any battery THAT IS PERMANANTLY SULFATED, or that has used up its active plate material, or that has internal corrosion, plate swelling or distortion, internal shorts etc by pulses, frequencies or any other means. Thats all snake oil.

You can remove some non permanant sulfates back to the acid, if its a healthy battery that has beel discharged for a long time if you are lucky by a very long slow charge over a few days at a controlled voltage /current. The act of charging IS desulfation. But it will never be as good as it was. And probably junk. And non of this can be determined by measuring voltages. I have a bunch of completely knackered batteries here that are all sat on the shelf at 13.0V.

Thank you,
Are there any standards to measure the battery other than voltage? say wattage or the time length to drive curtain load for curtain time ?

[Burgerman]

Many. But first you need to understand Peukert or surface charge.

There are 3 important factors or measurements you must do to determine if the battery is any good.

1. charge at 1/3rd of the 20h capacity rate at the CORRECT voltage. On a Gel battety that is 13.95V at 20C (MAX 14.10) until the battery has been on charge for 16 hours, then off. OR for 8 hours CV stage max, or to 1000th of its Capacity. So you will charge for about 12 to 16 hours total at 14.10V at room temperature.

2. Use a tool like the PL8 CHARGER that I use, because it can accurately measure Ah. If the battery is a MK gel, 74Ah battery, (I think?) you would set it to:
a) Discharge at the 20 hour rate. (74000mAh div by 20 = 3700mAh. Or 3.70A - Set discharge rate to 3.70A.
b) Set discharge limit to 10.5V. So it stops when the battery reaches this point.
c) READ OFF the Ah or mAh that was removed, accurately! If its the same as the rated capacity the battery is as new. If its less than 80% of rated capacity, reject. This is the end of life point.

2. Fully charge. Load test it. If you cant take 25A for 132 mins (from memory, look it up for your battery), before the voltage drops to below 9V, REJECT THE BATTERY. Because it will be useless in any wheelchair. Or anything that tries to take out current. This basically measures internal resistance. (This is the so called 'reserve capacity')
Ideally you would also measure battery AC impedance. The MK gel grp24 should be 3.5mOhm or less at 1khz.

3. Measure self discharge rate. Fully charge as above. Wait 28 days. Do the SAME discharge test as before. If it now has 5% less capacity in Ah reject the battery.

Ah measurement - under test..
This is an 80Ah 24V battery in a chair. So is being discharged at 4.00A over 20 hours. far it has had 19,181 mAh (19.2Ah removed), and it will stop when it reaches the manufacturers 100% discharge voltage limit at the 20 hour rate of 10.something Volts) :