Rebuild BM2 green...

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Re: Rebuild BM2 green...

Postby ex-Gooserider » 12 Feb 2016, 02:50

steves1977uk wrote:Where would I find the MOSFET type? on the top side of it?

Steve


On the face of the part (the non-tab side) you should see a part number and a manufacturer name or logo, and probably a date code and possibly other numbers.... Note some manufacturers that are trying to hide their designs will paint over the numbers or sand them off, in which case you are sort of screwed.... All that can be done then is to try and characterize the part (takes a lot of added / more sophisticated gear) and attempt to find a data-sheet description that matches.....

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Re: Rebuild BM2 green...

Postby ex-Gooserider » 12 Feb 2016, 02:52

Burgerman wrote:Thanks, must have one somewhere. I have a bunch of 5 and 10 watt resistors.

Expresso, you missed that its on 24V! Sounds like a vacuum cleaner!


Feed it a PWM signal (see 555 timer circuits....) or look in the mfg listings for the same form-factor and CFM rating in a 24V rating...

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Re: Rebuild BM2 green...

Postby expresso » 12 Feb 2016, 04:12

Burgerman wrote:Thanks, must have one somewhere. I have a bunch of 5 and 10 watt resistors.

Expresso, you missed that its on 24V! Sounds like a vacuum cleaner!


ok i dont know much - but just try to get the same type - volt and just quiet version with same CFM - -http://www.digikey.com/

i am sure they have it in 24V also - they have everything
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Re: Rebuild BM2 green...

Postby MenCallMeGimpy » 12 Feb 2016, 04:22

At the risk of looking a total maroon (to quote Bugs Bunny), what about ditching the fan and having heat sinks made? They could stick out the side just beneath the seat (ahead of the frame) and look like you've got a motorbike engine in there. Of course, you'd have to go full speed at all times to generate sufficient airflow, but that doesn't sound like it would be a problem, does it?
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Re: Rebuild BM2 green...

Postby Burgerman » 12 Feb 2016, 04:29

I used to have a heat sink. But if you look inside the mosfets do not contact the case directly and its the motor connections and cables that are acting directly as the thing that transfers the heat. As I have it now cool air blows around the case from the seat side and out along all four edges. The closest edge to the fan (hole) is the one were the cables are. It blows air pretty well over this connector side and over the wires. There's no good way to cool it with a heat sink.

Look at the pics of it in bits and you will see the heat path. The mosfets only sit against foam rubber and can get much hotter than the case. The heat of the board/mosfets really loses most of its heat via the large metal to metal flat faces that are the motor and input power connectors. If you feel these when its hot, those are the hottest parts by miles. I have considered drilling holes top and bottom... Makes the roboteq with its 32 output devices bolted solidly to an outer case heat sink look very good!

viewtopic.php?f=2&t=5380&start=200
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Re: Rebuild BM2 green...

Postby MenCallMeGimpy » 12 Feb 2016, 04:31

Burgerman wrote:There's no good way to cool it with a heat sink.


Damn. That would have looked very cool.
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Re: Rebuild BM2 green...

Postby Irving » 13 Feb 2016, 13:02

Another problem with putting a heatsink on that controller is that the tabs on those MOSFETs are not isolated so you'd need to use insulating mica sheets and nylon washers which make the heatsink much less effective.
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Re: Rebuild BM2 green...

Postby Burgerman » 23 Feb 2016, 16:20

Still awaiting a seat back... Be here 26th or soon after.
And footplate.
Wiring done, brake release fitted, seat plate on...

This is just a bump... So I dont forget to update it.

810_1336.JPG

810_1333.JPG

810_1332.JPG

810_1331.JPG
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Re: Rebuild BM2 green...

Postby steves1977uk » 23 Feb 2016, 17:56

Looking good BM :mrgreen: Wish I could use my hands to build stuff.

Steve
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Re: Rebuild BM2 green...

Postby hank » 23 Feb 2016, 18:29

First class build. 8-)
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Re: Rebuild BM2 green...

Postby Burgerman » 23 Feb 2016, 19:08

:mrgreen: Wish I could use my hands to build stuff.


You can use others hands as I mostly have to do. You learn to instruct!
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Re: Rebuild BM2 green...

Postby Burgerman » 23 Feb 2016, 19:58

Lights. Very hard to photograph. The yellow ones will be red LED when they arrive. So all will be red.

They are lots brighter than this seems to show. Sunglasses required!

Evening, room lights...
810_1344.JPG


Daylight...
810_1342.JPG
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Re: Rebuild BM2 green...

Postby expresso » 24 Feb 2016, 05:34

Love it- very nice -
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Re: Rebuild BM2 green...

Postby hank » 26 Feb 2016, 16:58

Has Santa been with your new Cobra Seat. :)
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Re: Rebuild BM2 green...

Postby Burgerman » 26 Feb 2016, 17:49

Not yet... Waiting. But THEY get it on the26th, so I get it 2days later...
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Re: Rebuild BM2 green...

Postby SteveO » 26 Feb 2016, 19:37

Burgerman wrote:Lights. Very hard to photograph. The yellow ones will be red LED when they arrive. So all will be red.

They are lots brighter than this seems to show. Sunglasses required!

Evening, room lights...
810_1344.JPG


Daylight...
810_1342.JPG

[quote="Burgerman"]Lights. Very hard to photograph. The yellow ones will be red LED when they arrive. So all will be red.

It's looking great, can you post a link to where you got the led bulbs from or did you have to replace the whole fitting? Either way can you do a link please? Also you added a 45 degree thermal switch for the fan, could you show us exactly where and how you fitted the switch and which fan you used as I'd like to do the same to mine
Thanks John
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Re: Rebuild BM2 green...

Postby Burgerman » 26 Feb 2016, 20:20

http://www.ebay.co.uk/itm/361442455527? ... EBIDX%3AIT

http://www.ebay.co.uk/itm/380891608375? ... EBIDX%3AIT

http://www.ebay.co.uk/itm/121215117549? ... EBIDX%3AIT

some use different! Take a look first.

Thermal switch was out of my pile of bits. Came from an old power supply. http://www.renge-components.com/photo/p ... mostat.jpg Like this. 40C woulds be better.
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Re: Rebuild BM2 green...

Postby SteveO » 26 Feb 2016, 21:10

Burgerman wrote:http://www.ebay.co.uk/itm/361442455527?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

http://www.ebay.co.uk/itm/380891608375? ... EBIDX%3AIT

http://www.ebay.co.uk/itm/121215117549? ... EBIDX%3AIT

some use different! Take a look first.

Thermal switch was out of my pile of bits. Came from an old power supply. http://www.renge-components.com/photo/p ... mostat.jpg Like this. 40C woulds be better.

That's great, thanks and those bulbs just go in as a direct replacement? And how do you attach the thermal switch to the PM and then to the fan?

Cheers John
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Re: Rebuild BM2 green...

Postby Burgerman » 26 Feb 2016, 21:41

The chip is fixed with epoxy inside the case, the wires go in series with the computer fan. And a resistor to give approx 12V and connected permanantly to the 24V supply.
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Re: Rebuild BM2 green...

Postby jim4472 » 26 Feb 2016, 23:10

Info from my duff 80 amp controller fets

IRF100N

IR037T

2Q 8K

Data Sheet
http://www.irf.com/part/_/A~PB-IRF1010N

hopefully this will help with Irvings request.

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Re: Rebuild BM2 green...

Postby Burgerman » 27 Feb 2016, 01:16

https://www.google.co.uk/url?sa=t&rct=j ... RQ&cad=rja

Barely 80A capable, and theres no heatsink as such in the pilot plus, and they are 11mOhm...
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Re: Rebuild BM2 green...

Postby SteveO » 27 Feb 2016, 02:14

Burgerman wrote:The chip is fixed with epoxy inside the case, the wires go in series with the computer fan. And a resistor to give approx 12V and connected permanantly to the 24V supply.

So I epoxy the switch directly to the inside of the case near the mossfets and run two wires to the positive wire on the fan, obviously splicing into the pos wire. The connect the fan wire direct to the batteries via a resistor? Or even just to one of the batteries? Sorry to be a pain in the ass but I don't want to get it wrong.

Thanks John
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Re: Rebuild BM2 green...

Postby Burgerman » 27 Feb 2016, 02:37

Yes. Never connect anything to one battery...
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Re: Rebuild BM2 green...

Postby ex-Gooserider » 27 Feb 2016, 02:47

SteveO wrote:
Burgerman wrote:The chip is fixed with epoxy inside the case, the wires go in series with the computer fan. And a resistor to give approx 12V and connected permanantly to the 24V supply.

So I epoxy the switch directly to the inside of the case near the mossfets and run two wires to the positive wire on the fan, obviously splicing into the pos wire. The connect the fan wire direct to the batteries via a resistor? Or even just to one of the batteries? Sorry to be a pain in the ass but I don't want to get it wrong.

Thanks John


NEVER, EVER, CONNECT ANYTHING TO JUST ONE BATTERY IN A SERIES SET!!!! Always connect across the entire set and design the circuit to produce the desired voltage to the important bits if they don't run on the set voltage*.... Tapping into just one battery in the set will produce an imbalanced load and damage the batteries by causing them to charge unevenly. Search for threads on the need to 'balance' or equalize the charge in the batteries if one wants maximum life out of them. One of the minor advantages of BM's car charging setup is that it automatically balances the batteries any time he hooks up to it.

In theory if one only charged in parallel, the imbalance caused by connecting to just one battery would be corrected each time you charged, but it still isn't a good idea, as you'd be discharging to unequal depths of discharge.

* Getting the desired voltage is an electronics 101 thing, as it is pretty simple, and it is best if you understand the theory, but for chair stuff, the three basic approaches are to:
1. Use two identical 12V devices in series, so they split the 24V from the pack;
2. Use an equivalent value resistor to drop the undesired voltage and dissipate it as heat - make sure the resistor has the wattage rating and be careful where you put it!
3. Use a DC-DC converter.

I will leave it as 'an exercise for the student' to explain how / why each approach works, and the costs / benefits of each....
(doing this will help your understanding, so it's worth the effort....)

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Re: Rebuild BM2 green...

Postby SteveO » 27 Feb 2016, 12:13

This is reason I ask my questions before doing anything first. Thanks John and exGooserider for your valuable advice which is priceless to me. Now, before I do anything I will accept your "student' to explain how / why each approach works, and the costs / benefit" exercise and post my findings here afterwards. Just coming on here everyday stops my brain turning to mush but it pleases me no end that you are all here to freely offer your fantastic advice making it possible for us to take control of our lives.
Tank you
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Re: Rebuild BM2 green...

Postby hank » 08 Mar 2016, 12:19

Any luck with your new Seat John. ;)
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Re: Rebuild BM2 green...

Postby Burgerman » 08 Mar 2016, 14:07

Email this morning, 16th to 18th.

But stuck on bed with a sore so might not be an issue...
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Re: Rebuild BM2 green...

Postby hank » 08 Mar 2016, 18:05

Sorry to hear that. get well soon.
No rush for new seat yet then.
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Re: Rebuild BM2 green...

Postby nandol » 06 Apr 2016, 19:54

Burgerman wrote:Next job. Making the powerchair RELIABLE!

Stock powerchair motor couplings, on most powerchair motors, or rubber cush drives if you prefer, fail with monotonous regularity. As soon as you fit decent low resistance batteries (throw away those gels), fit decent wiring, and program the chair to turn, stop, and go.

I have a draw full of these failed ones. From 3 different motor manufacturers. It feels like a gearbox failure, but in reality its a £2 part... Most are similar. What happens is that suddenly you put some real torque through them. And the outside case splits, jams under load as it expands.

I fix these now BEFORE they can fail.

The problem: (Good one on the right...)


olá Fellas,that part also fail in my motor two or three weeks after the old lady crash my chair with her vehicle
I already send this link to ivanov so he can from now on fix this problem, he also says the right motor is kaput,and i have to buy a pair of new ones

In Brazil you can drive a car with or without insurance...and its legal !! :o :shock:
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Re: Rebuild BM2 green...

Postby Burgerman » 07 Apr 2016, 09:38

I have to do the same to fix my BM3 too.

No insurance... Its the wild west over there still.
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