MKay

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MKay

Postby Mkay » 16 Jul 2019, 11:50

Firstly, thankyou for creating such a site BM. The BS and throwaway culture in the mobility sector is exhausting!

I am Michael, 35 from the Highlands of Scotland I have very limited ambulatory powers and strength, a frequent faller thanks to MD but my biggest problem is serious heart failure.

I leave my sofa rarely these days but I do enjoy good weather on a TGA Vita X (that is now seriously failing) I used to enjoy full bore rifle shooting, farming and minor engineering projects.


Currently the Vita has had issues with switching off during use which is incredibly dangerous at 8mph as it is effectively initiating an emergency brake; the batteries (Yucel gels) had had a hell of a run and been heavily mistreated so I couldn't really complain. A pair of 75ah Yellowtop's subsequently went in, along with andersons for 12v charging with a Victron Centaur.
Unfortunately the Optimas came at 12.4 & 12.3 respectively a few good boost charges but the ocv after a run is coming out at >.3v difference between the two batteries; meaning at least one of them has Sulfication and a lower capacity, Tayna are planning to collect them to test but I will get a PL8 on them first.
Out of curiosity (and because it was sat there) I installed a Victron Battery monitor and saw that the voltage under load was dropping significantly <23.3v up a steep hill, It also has amperage, so I did it again and saw it was pulling >120amps compared to 6amps on flat! off a 900w motor with a mass of 220kg including me.
Additionally the scooter is still anchoring up and then refusing to go again for 5mins, I can only assume I have a faulty with the s-drive 200A controller.
Either way it is not nice being 2miles from home and having to get pushed home in freewheel. Programming lead from woody duly ordered and we will hopefully learn what the error is.
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Re: MKay

Postby Burgerman » 16 Jul 2019, 12:46

You failed with the Optimas. They are the same size physically as the bigger and lower impedance 100Ah Odyssey. Both are deep cycle, and the Odyssey will show you much lower voltage drop under load. And a much greater "reserve" rating. So that would have been a far better choice.

The Optimas need the same 14.7V charge at 20C to 1000TH of capacity. If you do not continue this until amps fall to this level they will sulphate more every cycle That means charge till you see 75mA. Then stop. About 8 to 10 hours at CV after your trip. Also if they showed less than 12.6V on arrival they should have been rejected.

Out of curiosity (and because it was sat there) I installed a Victron Battery monitor and saw that the voltage under load was dropping significantly <23.3v up a steep hill, It also has amperage, so I did it again and saw it was pulling >120amps compared to 6amps on flat! off a 900w motor with a mass of 220kg including me.

Thats correct. Accelerate uphill from a standstill and it will read 200A. Limited by the controller.
Your 900 watt motor was actually taking 120A X 24V = 2880 Watts. Motor wattage has nothing to do with power output.

Additionally the scooter is still anchoring up and then refusing to go again for 5mins, I can only assume I have a faulty with the s-drive 200A controller.
Either way it is not nice being 2miles from home and having to get pushed home in freewheel. Programming lead from woody duly ordered and we will hopefully learn what the error is.

Its one of 2 things.
1. A bad connection like a loose terminal.
2. The controller warms up, and then it reduces power to protect itself. This is called thermal rollback. It progressively shuts dowm the Amps allowed to the motor.
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Re: MKay

Postby Mkay » 16 Jul 2019, 13:18

The Optima's were on offer at £179 before taking the vat off, the Odyssey were 350 (unless we are talking about different models). I should have rejected them straight away but I hadn't been there. Thought I would give them a go, wish I hadn't.

Up the hill at full speed not from a stand sill, just very surprised.

That was my thought though it didnt happen before the yucels died (checked all conections when installed the shunt for the BMS)

Centaur has AGM mode at 14.45v and 'Other' at 14.85 (@15Ah per battery) during abso phase then equalise to 100mAh then float (my megger doesn't read below 100mAh)
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Re: MKay

Postby Burgerman » 16 Jul 2019, 19:39

14.5 is borderline OK, but for full service life it needs to be a little higher. 14.7 is best for cyclic longevity.

Also whats important in cyclic operations is to be sure that the battery is charged TOTALLY. So you need to ensure your charger stays at 14.7CV for 8 hours, or until the battery reaches 1000th of its capacity. So a 70Ah battery will need to remain on charge until current falls to just 70mA. WHICHEVER OCCURS FIRST.
Call it 90mA fitted onto a chair (residual current drain when off adds a small amount) and because older or used batteries that have never been charged correctly may never reach this low point due to sulfation.

Failure to do this means that some sulfation remains and does not get returned to the electrolyte every cycle. And so capacity diminishes and internal resistance increases over time. Float isnt needed at all in cyclic use if charged correctly, but it does no harm. Should be 13.6V in cyclic operation, and 13.4V for long term float or storage operation.
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Re: MKay

Postby Mkay » 17 Jul 2019, 12:22

I will check that today. Do you think the 14.85v setting would be the better choice? Its not for long though, I have a 24v 50ah charger/dc power supply to use once I rewire which can be adjusted for voltage, ah and eq duration (4/8/12h).

The bmv shunt is installed between the battery negative and controller neg terminal, will this be showing the controller ah or just the battery ah (I thought this would be the same) ?
because its only showing <125ah and the controller is 180ah continuous duty which I thought would mean thermal shutdown is an unlikely outcome. Plus most of the time it happens at below 70ah.
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Re: MKay

Postby Burgerman » 17 Jul 2019, 15:10

I will check that today. Do you think the 14.85v setting would be the better choice?

No. Correct CV at room temperature is 14.4 to 14.7V with the higher 14.7 being prefered.

Its not for long though, I have a 24v 50ah charger/dc power supply to use once I rewire which can be adjusted for voltage, ah and eq duration (4/8/12h).

EQ? If thats Equalisation you do not want ANY!!!
You want your 50A CC, then an 8H limited CV Voltage of 14.7V or to 1000thC whichever occurs first.

The bmv shunt is installed between the battery negative and controller neg terminal, will this be showing the controller ah or just the battery ah (I thought this would be the same) ?

It will show battery Amps, and Ah used, by the controller.
Dont confuse the Controller Amps with MOTOR amps though. At stall and low speed, at max load, the motor amps can be 5X higher than the battery Amps.
This is because the low motor impedance may cause the 200A controller limit to be hit, at say 3 to 10V depending on impedance. Lets say it is reached at a 25% pulsewidth. Thats 6 volts at the motor, and 24V at the battery. So that means that when the motor draws 200A the battery current would be 1/4 of this. At 50A. As speed increases the motor requires more volts to achieve that 200A and so eventually at around 1/4 speed full pulsewidth is needed and battery amps = motor amps. And after this point current reduces to zero at just beyond max speed. And becomes NEGATIVE and regenerates power as you go downhill or decelerate. I expect that gives you a headache. It did me for a year or two.
because its only showing <125ah and the controller is 180ah continuous duty which I thought would mean thermal shutdown is an unlikely outcome. Plus most of the time it happens at below 70ah.

You are confusing Ah with Amps.

Ah is a measure of Amps over 1 hour consumed or stored. Amps is a measure of current.

So you can have an 8A charger, and it will put back 8Ah in one hour, 16Ah in 2 hours...
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Re: MKay

Postby Mkay » 20 Jul 2019, 11:54

That finally makes sense, its fine knowing something in principal but sometimes it helps to have someone put it in order.

You're right, Im not confusing Ah and Amps but I am bad for thinking quicker than I can type and not typing what I mean.

The language is differnet it does not use CC and CV but it does describe them as such, would you mind reading it and let me know if you agree

exerp- Assuming that the battery is discharged, the Skylla-TG charger commences charging in the boost-charge mode. In this mode the battery is charged until the battery voltage reaches the boost voltage. At this point the battery is charged to approximately 80% of its maximum capacity. This is the end of the boost-charge mode and the Skylla-TG charger then automatically switches to the equalize-charge mode. During the equalize-charge mode the charging voltage still equals the boost voltage, but the charge current slowly decreases.

Sounds like CC and CV just with names presumably translated from the terms used in sweden.
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Re: MKay

Postby Burgerman » 20 Jul 2019, 13:09

They have things all confused.

Heres what happens in a 2 and 3 stage charger. More stages are never needed and are marketing bullshit.

Stage 1, CC = Constant Current. This is also called BULK by the ignorant. In reality on a cheap charger this is simply the max power the charger has. So it will charge at say 8A as the battery voltage slowly rises. The charger is of course simply trying to charge at 14.4V or whatever. But hasnt the power to instantly push the battery that high. So its called a stage, but in reality its just go inadequate Amps (power) to hit CV instantly!

Stage 2, CV = Constant Voltage. Also called ABSORPTION, ACCEPTANCE ETC) This is when the charger or power supply reaches its preset voltage. It should hold this very steady, as the Amps naturally drop away as the battery becomes more full. When a typical lead battery reaches around 1000th of its Capacity then it is FULL 100%. This almost always takes 5 to 16 hours. When the current reaches this level, (E.G. 70Ah battery reaches 0.070 or 70mA) its charged. NOT reaching this level, usualy means the battery is not as healthy as new, and in any case for reasons of safety, and battery health CV should be limited to around 8 to 10 hours.

Stage 3, Theres a 3rd stage used for crappy chargers that end CV too soon, (typically 100thC or earlier) or used for long term storage. This too is a CV mode, and is at a lower voltage. If set to 13.6V AGM and GEL it continues the charge from stage 2, and completes it. At this voltage, limit this to say 3 days. But this takes a long time to fully charge the battery at the decreased voltage. And if this voltage is reduced further to say 13.35V then you can leave connected indefinitely for long term float storage to keep the battery healthy.

3 STAGES...
Below shows a typical SHORT CV stage, and requires long float to complete the charge.

bc-24-5000FChart.jpg


Better to monitor CV current untill it drops to a really low level instead in cyclic use, as we do not have time to wait for a CV voltage to complete the charge fully. Doing this means no CV required. So faster charge. AS SHOWN BELOW on my PL8 charger. 8 hours CV and no float.

VOLTS
amps.gif


AMPS
CC-CHARGE.gif
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Re: MKay

Postby Burgerman » 20 Jul 2019, 13:23

This is a MOBILITY charger, the upright type.

This is what it did when MONITORED BY THE PL8 ONLY! :lol: And you wonder why battery soon dies!!!
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