Much More Powerful Pie Now!!!

[Bikemad]

Don't solid state relays need an energising voltage like a mechanical relay? and if the energising voltage is off, won't the relay be off and not drawing any current?

Elmer is correct, if you look at the specifications for that relay, it gives an Off State Leakage Current of 30mA.  Although 30mA may seem rather low, it's enough to completely drain a fully charged 12Ah pack in under 17 days! 

12Ah/0.03A = 400hours = 16.67 Days

Alan
 

[Leslie]

Don't solid state relays need an energising voltage like a mechanical relay? and if the energising voltage is off, won't the relay be off and not drawing any current?

Elmer is correct, if you look at the specifications for that relay, it gives an Off State Leakage Current of 30mA.  Although 30mA may seem rather low, it's enough to completely drain a fully charged 12Ah pack in under 17 days! 

12Ah/0.03A = 400hours = 16.67 Days

Alan
 

That last thing I posted is rather large and humbly was the best I could do. and didnt need a forward current to stay close so it wasted nothing when off and or charging.

I want to get rid of one stage and replace it with the simple switchmode LM2576 it has delay switch capabilities with a cap on the no.5 pin` on off.  This should make it more efficient.


There are a few problems constant voltage switchmode need to overcome when dealing with larger variable voltage inputs, like our ebike packs looses plenty of voltage when we ride. and charge high to recharge. Mainly with the outout leg of the switcher and the buck overall resistance of the inductor.  It can get hot on the drain pin or the buck can starve from low voltage impeding the current flow to the devices.

So I will include a linear voltage regulator at the input to pad the voltage input to a reasonable level.  I have a 1500uh toroid inductor I hand wound from .5mm copper magnetwire so it should be good to 55v pulse.  I want 13v 900ma fro the switcher to run 6 watts 12v auto of led lights too.  Running the current regulator can not be an option.

Im going to try run my HBS36 500 watt at 72v and if all goes well I'll will think it worth a video. I don't know this thing does about 53kph at 60v

Im using an ecrazyman sensorless controller with 100v fets.  It has facility for 40 amps continuous but my HBS didn't respond to kindly to the sensorless requirement for my controller so I limited to 20 amps.  The bike could still do 53kph but it lost a little guts.  Some further mod to the throttle lost a little more top speed but gained a good hit of efficiency.

What resulted in a bike that performed like 36v bike on hills and almost a 60v bike on the flats, no bad heat at all or risk of overheating that wouldnt cost me my range.
 



More Pics latter.  I may get my old HBS running at 72v yet.

[o00scorpion00o]

Don't solid state relays need an energising voltage like a mechanical relay? and if the energising voltage is off, won't the relay be off and not drawing any current?

Elmer is correct, if you look at the specifications for that relay, it gives an Off State Leakage Current of 30mA.  Although 30mA may seem rather low, it's enough to completely drain a fully charged 12Ah pack in under 17 days! 

12Ah/0.03A = 400hours = 16.67 Days

Alan
 

Hi Alan,

Yes I understand now, Maybe I shouldn't read when I'm tired. 

I was thinking of disconnecting the battery when not in use, so that wouldn't be a problem as I have to take my battery inside to charge anyway.

I think Les has the ultimate solution indeed and It's nice and simple. I just thought the solid state relay would be better at handling higher currents than a mechanical relay. The highest I seem to find is 30 amps, where as solid state relays can take much higher currents. Ad I have seen my bike push more than 40 amps, though of course that's peak!

One other thing I believe the solid state relays can get hot and need a heatsink? and if that's true, that must mean they waste a lot of energy? or would a few watts mean much when riding anyway as the bike itself can use much more watts anyway!

It just baffles me anyway as to why (some) controller manufacturers don't include an on off switch. It would make things much easier. Really all I want is to switch on and off with a key switch when I'm out and about

[o00scorpion00o]

Check this out

http://radionics.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6995490

What about this for a relay???


Look at the price 

Pity it's way too expensive!

[Leslie]

That relay is a bit large for the Job.

The relay Monkey posted was fine.  The DC to DC converter is fine for a relay coil and efficient.  This the easy way and I have to say its worth the little extra.

It takes me ages to get these circuits to operate perfectly, it not just electrically they need to take the bumps and weather too. If for some reason they do not work you risk damaging your gear..

The bigger the relay often the bigger the current needed for switching and the coil if it is 12v a DC to DC converter will do the job.  Linear regs will not convert the voltage into current .  SO if you need 100ma at 50v you need to burn 3.8 watts to get 12v left over.  It all adds up.

Where as a DC to DC converter may use only 30ma to power a 100ma device.

I need 80ma to run controller logic and 100ma for the relay switch and around 300ma to run my led lamps  380ma in total if I do it linearly I will need to burn 14.44 watts. If I can bump the voltage down linearly to 50v on a 60v pack, at most not on the charger 4.9 watts.

This is why going for a really big relay isn't always the best idea, they can take too much power away.  That one reads about 375ma at 80 amps, now I aint sure if it means the 80 amp relay switch is so mofo it needs 180ma to switch it or it needs 180ma to switch a connected 80 amp constant current off from the input contact.  Your guess is as good as mine.  But the one I suggested only uses 50ma at the 24v coil. It would make a huge difference if you forget to turn the bike off after a ride on day.

If you can get a switch mode DC to DC converter to do the work you will save more watts.
I'll check Monkeys suggested relay out and see what it uses.

Edit

http://cgi.ebay.com/2-PCS-12V-coil-polarized-latching-relays-60A-250V-AC_W0QQitemZ250668406152QQcategoryZ36328QQcmdZViewItemQQ_trksidZp4340.m263QQ_trkparmsZalgo%3DSIC%26its%3DI%252BC%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%252BDDSIC%26otn%3D20%26pmod%3D370398338010%26ps%3D63%26clkid%3D6887377582374753659

Yeah I think Monkeys relay uses 12v 140ma compared to my 12v 100ma with his switchmode doing the work its better than my linear reg solution but with my switcher its about the same but much easier to install.  And I think he's relay latches which means it could stay on but can save power once it is on.

The non latching type only requires a pulse of power to switch on and off which he plans to use an RF key device from my understanding.

[Bikemad]

http://radionics.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6995490
What about this for a relay???
Pity it's way too expensive!

Why not build your own high current relay using four of these cheap automotive relays:



Just join the coils in series and the contacts in parallel.

You just can't beat cheap and simple!

Alan
 

[Leslie]

Why not build your own high current relay using four of these cheap automotive relays:


Just join the coils in series and the contacts in parallel.



Alan
 

30 amps.


Current rating only work in parallel and even then it isn't to good to do if you need the current.  There is no real resistive qualities of the contacts to regulate the current through both switches.

Remember it is rare  that we will switch on to a ready 20 amp load its only 80ma until you throttle.  

But you may need to switch it off from a full load.  Any individual parallel relay must be within specs.

The series relay one coil could LVC.

The three relays could be easy replaced by a 300 ohm 5 watt resistor.  But this may still LVC.

[Bikemad]

The series relay one coil could LVC.

If you use four idendical relays there should be no problem, as the voltage drop across each winding will be virtually the same.

The relay I chose actually has a rating of 40Amps continuous on the normally open contacts and 30Amps on the normally closed ones.

So in theory, it should be able to supply 160 amps of continuous current without any problem.

Alan
 

[o00scorpion00o]

The series relay one coil could LVC.

If you use four idendical relays there should be no problem, as the voltage drop across each winding will be virtually the same.

The relay I chose actually has a rating of 40Amps continuous on the normally open contacts and 30Amps on the normally closed ones.

So in theory, it should be able to supply 160 amps of continuous current without any problem.

Alan
 

Hi Alan,

Would the voltage variations using LiFeP04 hot off the charger and using full throttle not effect the relays?

Mark

[Bikemad]

A single relay would normally be working at ~14.5V when used on a car with the engine running (14.5V = regulated charging voltage), so that equates to 58V for four relay windings in series, your battery will probably be around 55V maximum when fully charged, so your battery voltage will be fine.

As far as the lower end of the operating range is concerned, the LVC on your BMS will cut out well before the voltage would be low low enough for the relays to switch off on their own.

Alan
 

[Leslie]

A single relay would normally be working at ~14.5V when used on a car with the engine running (14.5V = regulated charging voltage), so that equates to 58V for four relay windings in series, your battery will probably be around 55V maximum when fully charged, so your battery voltage will be fine.

As far as the lower end of the operating range is concerned, the LVC on your BMS will cut out well before the voltage would be low low enough for the relays to switch off on their own.

Alan
 

Why buy four relays and call it cheap when you can use a 50c resistor or even better a $1 regulator?  The Relays you pick are well within the capabilities we need for ebikes by them selves alone..

The 48v pack has 13 cells that discharge to 2.6v each don't they?  Well thats 33.8v  Can you be sure that the relay will be reliable at 8.5v each, is the divide going to be perfect?  Eg each relays has a 8.5v spot on Voltage drop.  Meaning all relays have a 10% resistance tolerance and that adds up to a possible 40% in series or 30% to any one relay.

30% tolerance on 33v is 11v  So the voltages may reach as low as 1v over any single coil, being parallel it will only disable one or two relays in the series at low volts..   This is still not in spec if you need 120 amps IMO.

I do know relays have a lower dropout voltage than their uptake, but the bumps on a road can make a difference to relay coils sitting on the edge of switching off.

These things are clear.  Four 30 amp relays in parallel is not needed.  120 amp is not needed.  Four series relay coils are not needed to regulate voltage.

Can you tell me how this is cheap?

I tell you Monkey Magic suggestion was the best and cheapest for most peoples needs. It can be modded with a precharge in it too.  It uses no power to keep it latched and none to keep it unlatch.

[o00scorpion00o]

Does anyone else here believe that controllers should have the facility to be turned on and off via a switch?
It would make life easier!


I have yet to figure out what the thin wire does on the magic controller. When used with a switch, all it does is turn off the lights bar one on the battery meter on the throttle! The motor works in any switch position!


Mark

[Leslie]

This is my setup.



It all still works fine.  I just want to avoid putting SLA's on it again.  Its been pretty harsh on the whole bike with the added weight but this is a muscle frame, fork and neck set hard tail MBT.



I use the 72v 40 amp sensorless ecrazyman controller as I was getting tired of hall sensors and just wanted something to take me from A to B.  As it tuned out with a little playing around I had 100% successful take offs.



I did notice the loss of torque on the take offs whi8ch seemed to be better when moving up to 60v, I would imagine that with 72v and a better hub than the HBS36 500 watt this controller would do better. So for 48v



It uses the IRFB4310 fet.

[Leslie]

Does anyone else here believe that controllers should have the facility to be turned on and off via a switch?
It would make life easier!


I have yet to figure out what the thin wire does on the magic controller. When used with a switch, all it does is turn off the lights bar one on the battery meter on the throttle! The motor works in any switch position!


Mark

Doesnt the key switch on the GM battery turn off the controller?  Other than that yes, its good to have a main switch, even an emergency cut off switch.  This can be wired off your brake switch as this is adequate to implement motor cutoff in emergencies, it not always appropriate to have to hold the brake switch closed for long than you need if your motor is stuck in full. But this isnt full off to the controller.

The precharge is to avoid the longish arc the higher DC voltages incur on the contacts of any switch.  Usually the faster switches last longer but the precharge  circuit insures your relay will live a long life.

[Bikemad]

Can you tell me how this is cheap?

Leslie, if you know of any other comparable cheap, high current relays suitable for straightforward use with a 48Volt battery, then perhaps you would be kind enough to post the details.

I suggested this D.I.Y. relay option because in my opinion it is a simple (and relatively cheap) solution for a  48V relay capable of switching high current, which is what Scorpion appeared to be searching for.

Let's compare it to the other options that were being considered or suggested:

• The 80Amp Panasonic Relay that Scorpion was looking at = €220.66
• MonkeyMagic's 60Amp Latching relay and DC-DC converter ~$36.40
• My suggested D.I.Y. 160Amp relay (4 x 12V 40Amp relays) ~$13.00

Looking at those prices, I consider it to be the cheapest option out of the three.

I wouldn't even consider the 80Amp Panasonic relay, because I'm still waiting to win the jackpot on the National Lottery!

The main advantage with the 60Amp latching relay is that it does not consume any power once it has been switched on or off, but unfortunately it does still have some disadvantages:

• It's designed to be mounted on a PCB and is therefore equipped with small fragile pins which the three coil wires must be attached to, making it less robust for bike use (and abuse.)
  
  
• As far as I am aware, the latching relay cannot be operated easily using a standard key switch, because it requires a momentary pulse to be supplied to each of the two coils, one to switch it on and the other to switch it off again. So presumably you would need a separate spring centred on/off/on toggle/rocker switch in addition to a standard key switch.
  (Please correct me if I've got this wrong.)
  
  
• If the battery is disconnected with the relay in the on position, whatever precharge system you employ will not work when the battery is reconnected, because the relay contacts will already be 100% closed.
  

If there was a perfect, cost effective switch solution that suited everyone, then perhaps we would all be using it!

Alan