HOW-TO: Add a digital volt meter to the charger

  • 6
  • Idea
  • Updated 3 months ago
  • Under Consideration
Summary:
Added a digital volt meter to the Ego Standard Charger.

*** DISCLAIMER ***
Ego does not endorse modifying equipment; doing so will void your warranty.

Background:
Ego's batteries do not have a traditional fuel meter.

Build Process:
1) cut opening in case
2) add the digital meter
3) calibrate and setup the meter
4) wire into charger (simply tapped off the +/- terminals
5) reassemble and test

Observations:
A) All four 1P (2.0 and 2.5 AH batteries), were at 51.6V / 41%; so all auto-discharge circuits are working.  Two 5.0 AH had been used last weekend, and were in a partial charge status.
B) Charging voltage as high as 59.0V, but drops back to 58.8V.
C) Cool to watch the CC/CV (constant current/constant voltage charge)

Conclusions:
This is cool, end of story.  Ego, please add some sort of battery meter system.

Future Projects:
Add this meter to my 20" gen 1 mower.

Amazon:
Geree Digital Volt Meter
https://smile.amazon.com/gp/product/B01CU07GN6/

Related threads:
i) Battry fuel meter
https://community.egopowerplus.com/ego/topics/battery-fuel-meter

ii) HOW-TO: Measure battery health
https://community.egopowerplus.com/ego/topics/how-to-measure-battery-health

Build Pictures:





Operational Pics:














Videos:



Photo of (a)Typical Engineer

(a)Typical Engineer

  • 26,300 Points 20k badge 2x thumb
  • engineery

Posted 1 year ago

  • 6
Photo of Oregon Mike

Oregon Mike, Champion

  • 36,046 Points 20k badge 2x thumb
What did you use to calibrate/verify calibration of the meter? 
Photo of (a)Typical Engineer

(a)Typical Engineer

  • 26,300 Points 20k badge 2x thumb
Used a Fluke multi-meter to set the "voltage trim" point.  That is the only thing that can be adjusted.  The % capacity is mostly likely based on a generic voltage discharge curve for the cell type selected.

I posted a little more detail in the first related thread link.

Here are additional details from the instruction pages:

https://d2r1vs3d9006ap.cloudfront.net/s3_images/1593021/RackMultipart20170507-13084-107ueux-IMG_2327_-_Copy.JPG?1494127990

https://d2r1vs3d9006ap.cloudfront.net/s3_images/1593022/RackMultipart20170507-92093-z1dtdx-IMG_2329_-_Copy.JPG?1494128005
Photo of Stephen Martin

Stephen Martin

  • 60 Points
Was thinking of adding a meter/indicator to the battery pack, but I think you have changed my mind to the charger instead.  Certainly easy enough.  

Question: The "T" terminal is to monitor temperature, but what is the "D" terminal?  Discharge maybe? (even though you wouldn't need it to discharge a battery)  Thx.
Photo of Jacob

Jacob, Champion

  • 61,956 Points 50k badge 2x thumb
I'm pretty sure d is for data so you would have to know how to read it. It could possibly be discharge. I'm pretty sure if it is discharge then it is actually the Battery sending that data out to the tool. It would be a microvolt value. I haven't looked at the battery to check if there is a shunt inside to confirm this.
Photo of Jacob

Jacob, Champion

  • 61,956 Points 50k badge 2x thumb
LOVE IT MAN!!!!!!!!!!
Photo of (a)Typical Engineer

(a)Typical Engineer

  • 26,300 Points 20k badge 2x thumb
Do you have a simple electrical schematic for frank-en-mower somewhere?  I've been meaning to figure out how to parallel "N" batteries without melting anything down, and it sounds like you have it figured out already, so no sense re-invent the wheel.
Photo of Jacob

Jacob, Champion

  • 61,956 Points 50k badge 2x thumb
Schotty diodes. They have a .3 v drop accross them. Not too terrible and they are cheap.

The best way to go is how the snow blower combines batteries, but schotty diodes are much more reliable and less sensitive.

http://www.radio-electronics.com/info...
Photo of Jacob

Jacob, Champion

  • 61,956 Points 50k badge 2x thumb
https://rover.ebay.com/rover/0/0/0?mp...
Here is one. Cheap and huge power
Photo of (a)Typical Engineer

(a)Typical Engineer

  • 26,300 Points 20k badge 2x thumb
Do you have details on how the snow blower parallels batteries?  It would be nice to be able to parallel more than two, like "N" number of them.  One application would be the ability to combine a couple (up to four) smaller (2.0/2.5) batteries in a backpack setup and power a high draw tool like a chainsaw or multi-tool.
Photo of Jacob

Jacob, Champion

  • 61,956 Points 50k badge 2x thumb
You could do 100 batteries using schottky diodes if you wanted. Completely isolated from each other by a 0.3v drop. The batteries will all work together as one drops below the next then the others pick up the slack.

The snow blower uses an op amp which outputs together. It could be a transistor. I can't quite tell yet.Much more complicated and many more pieces. I'll see if I have a picture.
Photo of Blue Angel

Blue Angel, Champion

  • 163,946 Points 100k badge 2x thumb
Nice job, aTE! This gives me some ideas...
Photo of (a)Typical Engineer

(a)Typical Engineer

  • 26,300 Points 20k badge 2x thumb
here's a table of data to make you heads hurt.  the interesting (to me) data is the total battery voltage and individual cell voltage at DISCHARGE, as well as at full charge.  if you watch the time lapse video above, you'll see the CC/CV; and the voltage goes over 58.8 (4.2v/cell) up to 59.0v, but then drops back down to 58.8 as the charger finishes up.

Photo of Michael G

Michael G

  • 7,098 Points 5k badge 2x thumb
This is really helpful. Couple questions:

1) Does the charger need to be plugged in for the battery level meter to work (I would think not)?

2) If not could one design a small standalone base to use on the battery to check it's charge?

(Now I'm kicking myself for selling my extra 2.0 battery and charger - could have hacked that charger)
Photo of (a)Typical Engineer

(a)Typical Engineer

  • 26,300 Points 20k badge 2x thumb
1) The volt meter is wired directly to the battery, so the charger does NOT need to be plugged in.
(Edited)
Photo of (a)Typical Engineer

(a)Typical Engineer

  • 26,300 Points 20k badge 2x thumb
2) yes, a stand-alone base would be helpful. And what I found out the other day is that you don’t need to lock the battery into the charger, just sliding it down until it makes contact, and that is enough for the meter to take a reading.

But it is important to note that if you have the charger plugged into the wall you should completely engage the battery to the charger so that you don’t have an intermittent connection.
Photo of MattW

MattW

  • 1,476 Points 1k badge 2x thumb
Nice work! I may have to try this out if I ever get spare time again.
Photo of Michael G

Michael G

  • 7,098 Points 5k badge 2x thumb
aTE - what is that component that it cable-tied just to the left of the fuel meter?
Photo of Michael G

Michael G

  • 7,098 Points 5k badge 2x thumb
Thanks - I had a set of security torx. The mod works great! I still need to calibrate it. I did need to cut some additional plastic inside the case to get the display to fit flush. I couldn’t figure out how you tied the wires into the connector so I ended up soldering them to the terminals for the battery that were shrink wrapped.

Thanks for sharing this mid.
Photo of Michael G

Michael G

  • 7,098 Points 5k badge 2x thumb
(a)TE - results after calibration:



I have a Fluke and high end Craftsman meters - both RMS capable. I opened my Fluke to c/o the batteries and one of the battery tangs was broken (hope this is a replacement part) so I had to use the Craftsman.
Photo of (a)Typical Engineer

(a)Typical Engineer

  • 26,280 Points 20k badge 2x thumb
Confirmed they are T-15 security torx, and these Wiha driver bits are the best:
https://smile.amazon.com/gp/product/B01B8L4Q3Q

Great results, especially the out of the box (assuming maintenance discharged) voltages, pretty much matches what my 2.0/2.5 dropped to.
Photo of Michael G

Michael G

  • 7,098 Points 5k badge 2x thumb
Got my Fluke working:

Photo of Blue Angel

Blue Angel, Champion

  • 162,740 Points 100k badge 2x thumb
I don’t know about the best, but those Wiha bits sure are awesome. I got the same set through KC Tool, much cheaper if you have a $50 order to qualify for free shipping:

https://www.kctoolco.com/wiha-76092-9...

Let’s face it... who ever orders less than $50 worth of tools?!?

KC Tool is a great place to pick up German tools. I’ve gotten most of my German stuff through them as well as Chad’s Toolbox, another great place to deal with.

The great thing about those Wiha Power Blade bits, besides their superior material and manufacturing, is their length. Using normal 1” insert bits works sometimes, but if the fasteners are recessed you’re screwed... pun intended. :-D
Photo of Michael G

Michael G

  • 7,098 Points 5k badge 2x thumb
I've noticed many having batteries that don't charge or unknown state so thought I'd bump this to the top.

I built one of these last year using (a)TE's instructions and use it every time before taking my batteries out to battle the lawn. Has saved me many trips back to the house to get fresh power. 

EGO should make a compact version of this and sell it (at least until they incorporate a battery meter in the battery).

Mike
Photo of Sam Kaplan

Sam Kaplan

  • 140 Points 100 badge 2x thumb
Plotting meter % (% charged) vs battery voltage gives a perfectly linear relationship from 25% to nearly 100% for both Typical Engineer's and Michael G's data.  This puzzles me since I thought that this behavior would be non-linear with a strong hysteresis.  Charging and discharging curves should be very different.  Could someone explain to me why there is a linear relationship?  Does this mean that battery voltage alone gives a reasonable measure of % charged?  Should battery voltage upon charging or discharging be measured after a waiting period to allow the voltage to settle to equilibrium?