PINNED - AGM & GEL battery info lead battery info

[Burgerman]

The battery box is the standard sunrise part with a groove descending down middle to only give about 178mm maximum height at the front.

Thats not standard.

Normally a set of gel mk grp24 73ah batteries fits fine the right way up...

[Glyphi]

Aha! Thank you for that info. Could this case be different because the chair has the full rise/tilt/recline kit fitted? For the amount I use it I wish I didn't have it...

OK time to take VERY careful measurements, Looks like M34 yes, M24 no way,Odyssey looks possibly if it's the side terminals only model. Have to put the front battery on it's side.

Glyn

[Burgerman]

Yes. But odyssey wont fit on its side.

[Glyphi]

Ah, that is a shame. The numbers made me slightly hopeful but when they are that tight there is no substitute for experience, I wish now I had started investigating the Lithium option a year ago. Best to fit the smaller battery now and read the lithium thread! (several times)..

Many thanks,

Glyn

[Glyphi]

Did anyone guess what my next question would be? Yup. Let's talk chargers - I don't mean the massive horses either...

So, MK M34's arrive tomorrow. My current charger - unbranded ebay device may give me the correct voltages/ I'm going to check. So I re-read the thread again! Then started looking around.

Ring Automotive do:
The http://www.ringautomotive.com/uk/products/Workshop+Tools/Battery+Maintenance+Tools/SmartChargePro/RSCPR824 looks like it does the job - but is pricey, £206.

Portable Power Tech do:
https://www.portablepowertech.com/product/premium-15a-24v-battery-charger/ that also looks good, but talks about bulk charging at up to 30.6V.. But all other parts of the cycle are the correct 28.2V. (Spec on https://www.portablepowertech.com/library/documents/555c57b0c6776-ht-c-30-12ht-c-15-24datasheet.pdf). Might I be safe to assume that it stops bulk charging when the battery hits 28.2V? I'm tempted to assume so. Good price at £120. The 12A device they do is even better at £82 - but the spec is useless. Phone call to be made perhaps.

Any of these - or even an 8A charger would be fine for my usage (can be heavy, but use the manual indoors).

The question - do any of you have comments on these manufacturers or these parts? Or recommendations for others?

Again, many thanks for the help.

Glyn

[Burgerman]

Ring one is ok set for gel.

Other one is 15A and less well made but should be ok set to mode 2 only. But that cant connect to he normal charge port and its big and bulky? It also stops charging at 1A and so will seem to charge fast but will really need another 6 hours or more at float.

[Glyphi]

Hmm, I don't like the +-1V accuracy bit much either. There will be others, so I'll keep looking if the old one is over-voltage.

BTW you mentioned USB charging stuff being expensive many many posts back. http://www.ebay.co.uk/itm/DC-Car-Charger-9V-12V-24V-35V-to-3-6V-4-USB-Port-Step-down-Power-Supply-Module-/301274641034?hash=item46255e328a:g:7JAAAOSw34FVCUzO Works for me, connected it to a 3 pin plug and plug it in instead of the charger.

Is there a good place to connect to get 24V that is switched on/off by the controller? I never got around to looking. (I looked harder last time and found them in the UK).

Now to build an arduino voltage monitor...

[Burgerman]

Theres nowhere that can be switched on off.

[Glyphi]

Oh Bum. Batteries here, but charger is throwing 29.1V into them. I wonder how much damage a one off charge at that voltage would do? I've stopped it for the moment. Any thoughts BM? Time to order a new charger methinks - lets hope for next day delivery.

[Burgerman]

Not much but dont do it!

http://www.wheelchairdriver.com/MK1.pdf
http://www.wheelchairdriver.com/MK2.pdf
http://www.wheelchairdriver.com/MK3.pdf
http://www.wheelchairdriver.com/MK4.pdf

14.1V max at room temp for Gel MK.

[Glyphi]

I know, I know - but it's new toys! I wanna play!

But I even checked the voltage on the old batteries. If only I had a couple of 10A diodes in the srcap box.

Haha, I may not but I do have a 15A bridge rectifier.. Now to go experiment.

[Burgerman]

If you let it go beyond 28.2V for long it produces gas. This puts voids in the gel that dont recover. Do be careful!

[Glyphi]

I'm experimenting on the old batteries - not made of money.. The bridge in the way prevented the charger going into charge - perhaps it senses the voltage on the battery before applying the charge voltage, the diodes could mess that up. Any other chargers recommended in the 8-12A range? I have been promised a ring back from the engineer at portable power tech. the one I showed you earlier is out of stock so am investigating the 12A one. The ring can be delivered Saturday and I still have 5 hrs to order it - but more options are good.

Thanks for your help BM.

[LROBBINS]

Many chargers will not start if they don't sense battery voltage (in many cases even a tiny 9V will suffice), so having a diode in line will keep it from starting.

[Burgerman]

Add a high value resistor across the diode(s). 1k maybe.

29v? Add one gives .7v drop. So 28.3? Ish.

[Burgerman]

Buy the ring charger... It does the job properly according to specs.

[Glyphi]

Ring charger on order. Might arrive tomorrow - might arrive tuesday.

My F55S, what maximum current would you expect to see it draw? Presumably draws max in stall mode? It's got the P&G joystick box, but no visible writing on the controller..

[Burgerman]

80 MOTOR Amps 6mph version
50 MOTOR Amps 4mph version.
Battery Amps is not 2x motor amps as you might expect other than at 1 particular speed at full load. Because that depends on pulse width at stall, and on motor impedance.

Where / how are you measuring it?

[Glyphi]

I was thinking of sticking a 0.01Ohm 10W resistor - initially in the battery charging cct - to measure the current, then thought hmm, would it work as I drive along? It should be possible to put something together cheaply to test out the idea - single largest cost is the anderson connectors! Many of the bits I have lying around. First pass is a bodge using an Arduino to get a feel for it but I also have a couple of dirt cheap 12bit ADCs on the way from China that use a good reference voltage. It's the sort of thing I may start and never finish, but it's gotta be worth a try.

So If I'm going flat out up a hill expect 160A.. Wow 256 Watt with a R01 resistor, and loose a volt over it. Better aim for R001 for an in drive version - though other sensors may be available... Allegro do one goes up to 200A... Only R0001


Stop it Glyn you are thinking, researching and typing all at the same time. Must lie down, too excited.

[Burgerman]

Use a clamp meter, or a hall current sensor.

But motor amps are far more interesting!
And completely different to battery amps.

For eg a low impedance 4 pole can take the full 100A or whatever your power module is capable of at stall at maybe 25% pulsewidth. Thats 25A battery current. With 2 motors, you can have 200A but just 50A battery current.

As you speed up, at full throttle, going up a ramp for eg, the 100A motor current stays the same, but pulsewidth increases, along with battery Amps.

Now you can really have a headache.

ONE motor wire, with a Clamp meter:
www.wheelchairdriver.com/gopro/motoramps.mp4

[Burgerman]

So If I'm going flat out up a hill expect 160A.. Wow 256 Watt with a R01 resistor, and loose a volt over it.

Wouldnt worry about 1 volt...

Watch the peak high, and peak low volts here. The 3 rows of small figures.
Remember that at 18V the controller reduces pulsewidth to maintain adequate battery voltage for safety and keep alive the controller...

This meter samples at high frequency. Records high, average and low values.
This tiny wheelie, drops the 25v batteries to 18V... Small figures at the bottom. Lead batteries are shit!

http://www.wheelchairdriver.com/gopro/voltdrop.mp4

[Burgerman]

So what do you suppose this (or basketball/soccer etc) does to the battery voltage?
Answers on a postcard. And the reason you need Odyssey or lithium.

http://www.wheelchairdriver.com/gopro/control.mp4

http://www.wheelchairdriver.com/gopro/wheelie.mp4

[Glyphi]

Yes, I was wondering how the chopped DC to the motor would affect it - Thanks, fascinating video. The Allegro device is Hall effect, effective resistance R0001. I'll go slow and steady at then. Use a R01 or R025 to monitor charging current and with another channel for voltage for the moment, it will be pretty inaccurate on current with the Arduino ADC. Do you reckon knocking 0.25V off the charging voltages will make a massive difference? or should I head for 0.01 straight away. The very first thing is to check the voltage never goes above 14.1V, the reason I started this merry chase.

What sort of frequency does the power module throw it's pulses out at? (Too lazy to connect a scope up today)

[Burgerman]

0.25V off the charging voltages will make a massive difference?

I posted 2 more posts while you were typing!

Charge will not be .25v lower if you use a resistor. Voltage drop will decrease over time as current falls. But it will result in long charge times or some undercharging.

[Burgerman]

What sort of frequency does the power module throw it's pulses out at? (Too lazy to connect a scope up today)

18 to 20k. Dep on controller. Anything above audio works. I set the roboteq to a lower frequency, 12k which I dont hear, and it scared my dog.

[Burgerman]

My current sensors on my powerchair look like this... Used for motor current measurement bi-directional.

[Glyphi]

Ahh, typing, Googling, rolling fags and musing.

Yes, took a sec to see the line about min,max and average readings - I was getting seriously worried.

I'm trying to get a second chair at a decent price at the mo - missed a perfect one on eBay some days ago. Then I'll think about lithium, the Oddessy ones wouldn't fit in mine.

Oops, you've posted again!

Yes, you are using the Allegro devices I found. How useful do you find them?

[Burgerman]

I posted yet more... And edited/added some. Go read!


They work great. They control the Roboteq motor compensation on my 45V BM3 powerchair.

[Glyphi]

I did. It's all fascinating stuff. It's a great help to be able to talk - what I do know becomes clearer, and what I don't can be learnt!

Assuming I do a conversion, lithium and roboteq but costs make me do one at a totally different time to t'other, which one to to first? Roboteq on lead initially? or 24V with lithium initially? (Assuming the massive range is not important)

Whoops, that's assuming the standard 6mph motors do not mind being over-volted. Do they? I'm, not sure how hot they get at the moment.

[Burgerman]

6MPH motors like all dc motors get hot through amps. Which are highest at stall. And lowest at full speed and lowest load.

At stall, 100 plus amps, no movement at all = 0% efficient. Smoke.
At 24 or 36, or more volts free running = about 6A.