Analog fuel gauge for Emus BMS?

E

Eskutr

10 mW
Joined
Jan 8, 2014
Messages
21
Hi,

We're working on a conversion of a vintage scooter to electric power and have one question that we cannot find an answer to anywhere on the web...

Has anyone experience with connecting an analog fuel gauge to Emus BMS to provide SOC information? What is the best way to do it? Is it reliable and accurate? Any pitfalls to avoid? Anyone specifically use the Smiths Flight Fuel Gauge (http://www.europaspares.com/interior-parts/instruments-gauges/smiths-flight-gauges/smiths-flight-fuel-gauge.html)?

Ps for general advice, we're very happy with the Emus BMS and would recommend it for size and features. Only downside is it takes some time for the firm to reply to email questions - though generally helpful when they do.

Thanks for any help or advice, much appreciated!

Best wishes from Prague,
Neil
 
Not sure what voltage range you need but knoxie or jozzer in Britain were selling an led "fuel gauge" a while ago.
otherDoc
 
Id just go for something like this, in a real voltmeter.

http://www.ebay.com/itm/1PC-AC-0-150V-Analog-Voltmeter-Analogue-Volage-Panel-Meter-Dricetly-Connected-/171179466905?pt=LH_DefaultDomain_0&hash=item27db176099

Its old school analog, so it will look right.
 
I think you are on the wrong forum. people here don't use high end stuff for majority of projects. Try asking @ diy electric car forum. Few have same BMS and might advise you better.
Regarding response from them, they are small group of people that are constantly working on their BMS making product like no other hence slow on responding.
 
dogman said:
Id just go for something like this, in a real voltmeter.

http://www.ebay.com/itm/1PC-AC-0-150V-Analog-Voltmeter-Analogue-Volage-Panel-Meter-Dricetly-Connected-/171179466905?pt=LH_DefaultDomain_0&hash=item27db176099

Its old school analog, so it will look right.
Click to expand...

Thanks for the tip, it's a good voltmeter for the price, but unfortunately too big for our use... we only have approx 55mm to play with it on the scooter dash. We're also very keen to use the output from the BMS on SOC, it's a better guide since discharge affect on voltage is non-linear.

Appreciate your help, have a nice day.
 
agniusm said:
I think you are on the wrong forum. people here don't use high end stuff for majority of projects. Try asking @ diy electric car forum. Few have same BMS and might advise you better.
Regarding response from them, they are small group of people that are constantly working on their BMS making product like no other hence slow on responding.
Click to expand...

OK, will do, thanks for the tip! Have a nice day.
 
Ahh, if you are using lifepo4, then yes a simple voltmeter will not do well for you to monitor state of charge. It works fine with some experience, with lico, limn, lead, etc. But not with lifepo4.

But now you have me confused, maybe because I know nothing of the bms you plan to use. Are you not talking about turning your fuel gauge into some kind of voltmeter? That was what I thought, so I immediately just pointed out that you can just buy a voltmeter. Hunt one down that fits?

What you want is a wattmeter. One that counts watt hours I mean. If you can't fit one in the dash space, then you can at least mount one elsewhere. The Cycleanalyst is the best wattmeter out there, but cheap ones also exist, that could be put someplace where you could peek at it during a stop, at the minimum.

I don't know about the space you have, but I'd be finding space for a wattmeter display. Nothings impossible, so put on the thinking cap, and make it happen. I do understand, you don't want it to look like one of my E bikes. FWIW, the cheap wattmeters on ebay are a box 85mm long, with a 65mm display window. A CA is bigger, and weather resistant, so perhaps a good looking mount somewhere you can see it can be devised.

There are lots of things out there, Here is the smallest wattmeter I could find in 5 min.

http://www.ebay.com/itm/SKYRC-RC-Battery-MultiFunction-Watt-Meter-Model-WM-010-/190958703155?pt=Radio_Control_Parts_Accessories&hash=item2c76069233
 
Eskutr, I think you are on right forum. I may be able to help you. The "SOC OUT" pin on Emus BMS is pulse-width-modulated 0-5V signal. You can easily connect it to standard analogue gauge, however you need additional circuitry to do so. That can be some sort of signal integrator and amplifier. This schematic was tested and is confirmed to be working:
fSfMnRM.png


BMS is on left side and analogue fuel gauge is on right side.
 
circuit said:
Eskutr, I think you are on right forum. I may be able to help you. The "SOC OUT" pin on Emus BMS is pulse-width-modulated 0-5V signal. You can easily connect it to standard analogue gauge, however you need additional circuitry to do so. That can be some sort of signal integrator and amplifier. This schematic was tested and is confirmed to be working:
fSfMnRM.png


BMS is on left side and analogue fuel gauge is on right side.
Click to expand...

Hi circuit, thanks for the reply, and the answer is just what we need.... but *swallow pride* can I ask you if you would explain to us what "D15V6" and "Q1" are? We are more auto mechanics than electronic engineers. If you have something working, would you send us a photo of it to copy?

Thanks again, we really appreciate your advice.
 
dogman said:
Ahh, if you are using lifepo4, then yes a simple voltmeter will not do well for you to monitor state of charge. It works fine with some experience, with lico, limn, lead, etc. But not with lifepo4.

But now you have me confused, maybe because I know nothing of the bms you plan to use. Are you not talking about turning your fuel gauge into some kind of voltmeter? That was what I thought, so I immediately just pointed out that you can just buy a voltmeter. Hunt one down that fits?

What you want is a wattmeter. One that counts watt hours I mean. If you can't fit one in the dash space, then you can at least mount one elsewhere. The Cycleanalyst is the best wattmeter out there, but cheap ones also exist, that could be put someplace where you could peek at it during a stop, at the minimum.

I don't know about the space you have, but I'd be finding space for a wattmeter display. Nothings impossible, so put on the thinking cap, and make it happen. I do understand, you don't want it to look like one of my E bikes. FWIW, the cheap wattmeters on ebay are a box 85mm long, with a 65mm display window. A CA is bigger, and weather resistant, so perhaps a good looking mount somewhere you can see it can be devised.

There are lots of things out there, Here is the smallest wattmeter I could find in 5 min.

http://www.ebay.com/itm/SKYRC-RC-Battery-MultiFunction-Watt-Meter-Model-WM-010-/190958703155?pt=Radio_Control_Parts_Accessories&hash=item2c76069233
Click to expand...

Hi, Thank you for taking the time to answer, we appreciate it.
 
D1 is a zener diode, 5.6 Volts. For example model 1N4734A (black end goes up in the schematic):
http://uk.farnell.com/multicomp/1n4734a/diode-zener-1w-5-6v-do-41/dp/1861448

Q1 is a generic mosfet. For example STP22NF03L:
http://uk.farnell.com/stmicroelectronics/stp22nf03l/mosfet-n-to-220/dp/9803092

Almost any mosfet will fit here. You can buy these parts at any local electronics parts shop (not washing machine shop). If they will not have these exact parts, just show them the schematic and explain what it is for - they will find suitable parts. You cal also ask them how to connect these properly and which pin goes where.
 
circuit said:
D1 is a zener diode, 5.6 Volts. For example model 1N4734A (black end goes up in the schematic):
http://uk.farnell.com/multicomp/1n4734a/diode-zener-1w-5-6v-do-41/dp/1861448

Q1 is a generic mosfet. For example STP22NF03L:
http://uk.farnell.com/stmicroelectronics/stp22nf03l/mosfet-n-to-220/dp/9803092

Almost any mosfet will fit here. You can buy these parts at any local electronics parts shop (not washing machine shop). If they will not have these exact parts, just show them the schematic and explain what it is for - they will find suitable parts. You cal also ask them how to connect these properly and which pin goes where.
Click to expand...

Thanks a lot, that's clear now. Wishing you a nice evening.
 
Hi Circuit, you seems to be expert for EMUS BMS.
I have EMUS installed in 2 motorcycles. One has fault current sensor, need to send it back to EMUS and ask for replacement. It is new but it is not working :evil:

Well I have some issues with BMS. I have already spoken with one of the guys from EMUS, but perhaps you can help me.

I was charging the motorcycle and suddenly probably BMS has stopped charging process. It is paired with Elcon charger via CAN. BMS detects to high voltage and temperature on cells, fault code is 146. This must be misreading because all values are perfect (3,31-3,35V and 20-22 degrees celzius) and inside normal values. I have no idea what is wrong :oops:

I upgraded software to 2.xx. But I can not upload firmware for CAN group modules. It reports...enter config mode failed :roll:

Any advice would be most welcome 8)
 
tomaj said:
Hi Circuit, you seems to be expert for EMUS BMS.
I have EMUS installed in 2 motorcycles. One has fault current sensor, need to send it back to EMUS and ask for replacement. It is new but it is not working :evil:

Well I have some issues with BMS. I have already spoken with one of the guys from EMUS, but perhaps you can help me.

I was charging the motorcycle and suddenly probably BMS has stopped charging process. It is paired with Elcon charger via CAN. BMS detects to high voltage and temperature on cells, fault code is 146. This must be misreading because all values are perfect (3,31-3,35V and 20-22 degrees celzius) and inside normal values. I have no idea what is wrong :oops:

I upgraded software to 2.xx. But I can not upload firmware for CAN group modules. It reports...enter config mode failed :roll:

Any advice would be most welcome 8)
Click to expand...
What has happened with your current sensor? Have you tried to swap them and check if it is actual current sensor problem and not wiring, configuration, etc? If you're sure it's a problem with current sensor then yes, simply send it back and it will be replaced.

About the temperature thing.. I am not familiar with error codes, but this could happen during balancing: cell modules overheat and shut down to prevent damage. This could be solved in a number of ways:
1. provide better cooling to dissipate heat from cell modules.
2. lower balancing current (say, set 50% instead of 100%). Twice lower current means 4 times less heat.
3. increase maximum allowed temperature. This is probably not the recommended way to go, but it is an easy way to solve problems. Thing is that BMS reports temperatures by measuring cell module's temperature. When it is balancing, it is much hotter than cell itself. There are two temperature limits: software and hardware. Hardware limit is in the cell module, and it is set to, I think, 80°C. When this temperature is reached, cell module gradually lowers balancing current to cool off. This does not trigger any errors and charging may continue (charging current is lowered by BMS to keep required voltages). So you can simply set your maximum allowed temperature above 80°C (say, 85) and this will solve unexpected overtemperature problems. However this will put your system in danger if there is any rise in cell temperature due to any other reason. I'd suggest consider option #1 and #2.
4. check overvoltage protection and "full" voltage configuration. If these values are very close, it could be that voltage on one or more cells jumps a bit when cell module shuts down and this causes overvoltage protection to go off. If you are using LiFePO4 cells with "fully charged 3.65V" rating, I'd suggest setting "fully charged" value to 3.62V and "overvoltage protection" value to 3.70V or so. You can play a bit to find the best solution. Do not be afraid to charge to lower voltage than 3.65V, as energy difference at that range is very low.

You can also save a log file and send it to Emus BMS support and they will be able to see what happened.
Also I have to mention that v1 and v2 firmwares are not totally compatible: to downgrade from v2, you first have to install "factory settings reset" firmware and then go with v1.
I'd suggest you to contact support and describe the problem with group modules: maybe it is a known issue and a quick fix will be provided.
 
Thank you for very fast respond.

Yes I have replaced Current sensor with another one and it is working perfect. So I am 100% sure that sensor is fault.

All settings are OK. I have been charging the bike at least 20 times. Right now, cells T are 20 degrees and voltages 3,32-3,35, I plug the charger...charging error, too high cell temperature. It cuts out in 1 second. Does not even start charging. Wiring is correct.

They send me CAN modules firmware but it is impossible to install it.

I will talk with the tech support again, Hope we can solve the problem.

This BMS is high quality product, but it has a couple of bugs, which can kill your nerves 8)

Thanks for your time!
 
when you change the current sensor you need also to change the calibration inside the software , maybe it will not solve but it may help to find out the issue
 
Sorry to divert, but.

I knew somebody here would know how to make that original gauge work. But is it not just a volts readout?

You should still put a wattmeter on the bike someplace, even if just under the seat so you can have a peek at it before continuing to ride further from home.

If it's not lifepo4, then you will soon be able to correlate various % of discharge to the meter on the dash. 50% might still be hard to guess, but 20% left, you should be able to see that by the dash gauge.
 
dogman said:
Sorry to divert, but.

I knew somebody here would know how to make that original gauge work. But is it not just a volts readout?

You should still put a wattmeter on the bike someplace, even if just under the seat so you can have a peek at it before continuing to ride further from home.

If it's not lifepo4, then you will soon be able to correlate various % of discharge to the meter on the dash. 50% might still be hard to guess, but 20% left, you should be able to see that by the dash gauge.
Click to expand...
the usual gauge meters are resistance-driven. Simply add a variable pulldown resistor. It is not so straight-forward to show voltage, as it requires 12V supply and current is quite high.

As for Emus BMS, it outputs a calculated State-of-Charge value, so it is a real SOC in percentage.
 
SOC still based on voltage though right? I fail to see how it's counting wh. Fine for everything but lifepo4 though. I'm sure it will work ok for most use of the scoot.

I'm just spoiled now, having a couple CA's.
 
dogman said:
SOC still based on voltage though right? I fail to see how it's counting wh. Fine for everything but lifepo4 though. I'm sure it will work ok for most use of the scoot.

I'm just spoiled now, having a couple CA's.
Click to expand...
No, it is based on current sensor and some additional software corrections. Emus Current Sensor has two ranges: ±100A and ±1000A. Both ranges are used at the same time to improve accuracy, especially on lower currents. More info is available on Elektromotus wiki site.
http://elektromotus.lt/wiki/index.php?title=BMS:_Installation_Manual_v2.x

If you are a fan of CA, I'd recommend to check out elektromotus Bluetooth connection feature (requires additional BT module). They offer a nice Android app, which is freely available on Play market: https://play.google.com/store/apps/details?id=eu.elektromotus.emusbms.evgui.blue

EVGUI_RC6_1.png

EVGUI_RC6_2.png
 
Thank you for your explanation. I'll remain ignorant of most electronics forever I'm afraid. I'm good for explaining basics to noobs but that's about all.

I had not heard of a bms that included a shunt, or something like it. I just thought it was only reading voltage, then converting it to a lower voltage for the 12v based indicator.

Damn cool.
 
Circuit...

We have now tried with new firmware version (it is available on their website) but with no success :evil: There is no way to upload Can group module firmware. I have tried with all firmware versions, use factory restore firmware, reset BMS, swap BMS main unit with another one, use other PC, but...NO GO :(
I will let you know If/when we will found the solution.
 
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