Author Topic: I took my Morgen for a ride today.  (Read 7561 times)

Offline Morgen 3Eman

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I took my Morgen for a ride today.
« on: May 31, 2012, 01:30:04 AM »
Hi Folks,

I finally finished the prep work for painting my Morgen, and re-assembled it, and today it was all together, interior installed and everything.  It was a lovely day here in Oregon, so I drove it around the neighborhood for half an hour.  The MP3 worked flawlessly.  I'm really pleased with how well it accelerates and brakes. 

Thanks again to all you kind folks who have given me so much knowledge and advice on this crazy project.


TTFN,
Dennis

Offline Morgen 3Eman

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Re: I took my Morgen for a ride today.
« Reply #1 on: May 31, 2012, 10:54:40 PM »
I've driven it around for about an hour now, and the 48V LED is still green.   I'm very pleased with how fast it cruises at 15 Amps.  I really need a speedo...
,
Dennis

Offline Bikemad

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Re: Incorrect Battery Gauge Operation with lithium batteries
« Reply #2 on: June 01, 2012, 03:39:34 AM »
I've driven it around for about an hour now, and the 48V LED is still green.

Dennis, if you have the LiFePo4 pack, the battery voltage is likely to be too high for the gauge to function correctly.

These simple gauges were originally designed for use with lead acid batteries, which have quite a pronounced voltage drop as the battery is discharged or loaded. The lithium batteries however have a very gradual voltage drop throughout the discharge period until they reach a point where the voltage suddenly drops very quickly very near to the end of their discharge cycle.

The following diagram is not meant to be 100% accurate, it is purely intended to give a rough comparison of the typical discharge curves for the three types of batteries that are commonly used:


A 13 cell Lithium Polymer pack would be almost the same as the LiMnO2 curve.

I don't know the actual figures, so let's simply assume that the battery gauge Green and Amber LEDs are meant to go off at 51V (~50%) and 45V (~85%) respectively with a lead acid battery pack. 
If you look again at the above diagram, you should be able to see that the LiFePO4 pack would need to be ~90% discharged before the Green light would go off, and almost completely exhausted before the Amber light would go off.

I think this might explain why you've been able to drive around for so long without the green light going out. However, there is also another possible explanation, if you have a 36V throttle and a 48V battery, the green light will stay on continually until the battery's BMS eventually triggers the Low Voltage Cut-out! ::)

I tend to use my battery gauge solely to indicate that power is turned on, and I rely on my Turnigy Watt Meter to measure the capacity in Ahs that has actually been used, this gives me a reasonably good indication of how much battery capacity I still have available to use.

If the battery runs too low on my bike,  I can simply pedal my way back home again, but with your Morgen, I imagine it would be much more of a problem. ;)

If your Mercedes had a over optimistic fuel gauge, you'd probably carry a spare gallon of fuel with you just in case. So you might want to consider installing a small reserve battery pack so that you can simply switch over when the main pack runs out unexpectedly.

Alan
 
« Last Edit: July 04, 2017, 08:56:50 PM by Bikemad »

Offline Morgen 3Eman

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Re: I took my Morgen for a ride today.
« Reply #3 on: June 01, 2012, 05:50:41 PM »
Hi Alan,

You are so helpful!  I just found a modern analog voltage meter that is packaged like my ammeter, and I figured to scale it to read 58v to 48 volts would be enough resolution, but with your info, maybe I should rescale it only down to 50 volts....

The throttle is marked 48v.  Oh, and I tried pus in g the Morgen, and it is pretty easy.  I wouldn't want to push it a mile , tho.

TTFN,
Dennis

Offline jbzg

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Re: I took my Morgen for a ride today.
« Reply #4 on: June 04, 2012, 09:49:36 PM »
Hey,

I have mentioned my problems with battery level meter in other post (36v throttle, instead 48v was delivered to me by my local dealer), so I'm thinking about installing volt meter...

Would you say that something like this http://item.mobileweb.ebay.com/viewitem?itemId=110851328156&index=14&nav=SEARCH&nid=90347 would be useful?

Offline Morgen 3Eman

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Re: I took my Morgen for a ride today.
« Reply #5 on: June 04, 2012, 11:05:48 PM »
Well that looks pretty cool, but for my Morgen I wanted an analog voltmeter to go with the Lucas analog ammeter.  Here is what I bought:

http://www.sunpro.com/product_detail.php?pid=16305

I put a 40 volt zener in series to get the full scale up to 58 volts, and then recalibrated it. 

Having said that, the fact that it only requires signal wiring to operate makes it a lot straight forward to install.  If I would have wanted a digital dash, I definitely would have considered that meter.   

TTFN,
Dennis