Newbie

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Newbie

Postby ronp849 » 02 Jul 2018, 01:08

Hi All
I am not a wheelchair user but I do voluntary repair work with the local DAG, (Disability Action Group who rent out scooters and wheelchairs to the local community).
I have recently managed to acquire my own scooter which was a scrapped TGA Super Sport. A magnet had come away from the motor casing which caused the motor to jam. After the magnet was refitted with a bit of two part epoxy, the scooter was working again.

At the same time as the scooter, I acquired some scrapped 70Ah batteries that were below 60% of their capacity. These were fitted on the scooter and given a test run. At first, the charge indicator dropped below 100% after a couple of miles but after a few charge cycles the capacity seems much improved. I do connect the charger after each use and leave it connected after full charge indicated. Is this normal practice?

Ron
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Re: Newbie

Postby Burgerman » 02 Jul 2018, 01:30

At the same time as the scooter, I acquired some scrapped 70Ah batteries that were below 60% of their capacity. These were fitted on the scooter and given a test run. At first, the charge indicator dropped below 100% after a couple of miles but after a few charge cycles the capacity seems much improved. I do connect the charger after each use and leave it connected after full charge indicated. Is this normal practice?


Welcome!
No not normal. But depending on if your charger is a modern 3 stage device, you actually SHOULD connect overnight, and leave connected up to about 20 to 24 hours if you can.

I would love to know how you determined the batteries were 60%?

When a battery is not charged for long enough, or not charged for long periods and left discharged it can leave them sulfated. Sulfation is a natural consequence of discharging. The battery plate gets a nice coat of lead sulfate on one plate and lead dioxide on the other and leaves the acid/water electrolyte weak. Recharging in a timely fashion reverses that, restores the sulfate back to the electrolyte.

However if the battery is left discharged for long, or not fully charged for at least 16 hours now and again, this lead sulfate turns to larger crystals, that cant ever be reversed since they no longer conduct electricity. So then even after charging fully some permanant sulfate remains.

If you are in time, and things were not too bad, a long slow charge or two reverses this, as much as is ever possible, and returns it to the electrolyte. But you will never get 100% capacity back. As a battery is used or cycled they age in a number of ways that have nothing to do with sulfates at the same time. So they may be say 80% as good as new, or some other figure at some point even when charged correctly.

The only way to actually know is to use a fancy computerised charger that many on here have. It counts Ah out, at a controlled 24 hour rate, and graphs the result down to 10.5V or whatever the battery manufacturer specifies.
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Re: Newbie

Postby ronp849 » 02 Jul 2018, 14:17

I would love to know how you determined the batteries were 60%?


The batteries are Drop Tested - I know, I raised an eyebrow when I first heard it. It does not mean from a great height but by using a computerised discharge unit, (Alpha Bat) to measure the voltage drop during a high discharge session.

Ron
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Re: Newbie

Postby Burgerman » 02 Jul 2018, 14:27

That cannot tell you the capacity. In fact cant tell you much. It just a pulse tester and a big guess. https://www.flexelmobility.com/catalogu ... ry-tester/ Frankly not much better than guessing.

To measure that capacity, you have one way only.

A 20 hour rate and a 10 hour rate complete charge discharge and measure the results accurately. It takes more than a day to charge, discharge, and fully recharge. And you must have the gear, and the knowledge to do this properly. And the battery manufacturer full specs sheet.

You need this, to test 2 lead batteries at once, and a lot of time... Then you can know.
Testing two small lithium cells here.

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