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

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  • Updated 1 year ago
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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:



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(a)Typical Engineer

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  • engineery

Posted 2 years ago

  • 7
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Oregon Mike, Champion

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What did you use to calibrate/verify calibration of the meter? 
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(a)Typical Engineer

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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
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Stephen Martin

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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.
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Jacob

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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.
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Jacob

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LOVE IT MAN!!!!!!!!!!
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(a)Typical Engineer

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You "need" this for your monster reel mower madness machine.
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Jacob

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I have one on each battery that senses over current and fires a relay to reduce the self propel speed. Not perfect but it does help. Nearly the same ones as your using but has a output on it.
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(a)Typical Engineer

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What is the purpose of that, reduce current if the battery drops below a certain point?  What is the trip point?
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Jacob

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It limits the self propulsion system. Basically 2 relays in series. one side of each relay, normally open side, has a resistor. The throttle runs through the 2 relays on the normally closed sides. When amp draw exceeds the present amount, it triggers the relay to reduce the output from the speed throttle.

It keeps it from pulling too many amps from the batteries. I have it set at 10 amps each battery. Since the batteries are tied together with a schotty diode, it protects each battery individually.
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(a)Typical Engineer

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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.
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Jacob

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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...
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Jacob

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https://rover.ebay.com/rover/0/0/0?mp...
Here is one. Cheap and huge power
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(a)Typical Engineer

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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.
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Jacob

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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.
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Blue Angel, Champion

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Nice job, aTE! This gives me some ideas...
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(a)Typical Engineer

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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.

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Michael G

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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)
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(a)Typical Engineer

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1) The volt meter is wired directly to the battery, so the charger does NOT need to be plugged in.
(Edited)
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(a)Typical Engineer

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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.
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MattW

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Nice work! I may have to try this out if I ever get spare time again.
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Michael G

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aTE - what is that component that it cable-tied just to the left of the fuel meter?
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(a)Typical Engineer

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It's the push button switch that is used to adjust the meter's settings.  It was a temporary mounting, and next time I have it apart I'll figure out something a little more permanent.

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Michael G

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aTE - I received this meter today. Head is a little spinny after reading the instructions. Would appreciate it if you could give me help on the settings. I do have a Fluke meter if needed. Does this need to be reset for every battery size.

Thanks
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(a)Typical Engineer

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If you don't have instruction sheet, this reviewer posted the entire procedure in a review:

https://smile.amazon.com/review/R2YFRS3XJSP8SB/ref=ask_dp_lswr_rp_hza

1-U: you are "trimming" the voltage to match the voltage measured with the volt meter

2-b: set to "3.7"

3-c: set to "14", the number of cells in an Ego battery

4-d: set as desired (i use the setting which flips back and fourth between the voltage and capacity readings

Regarding the question, once you set the meter for 14 cells, it is set regardless of being a 1-P 2.0 AH, or a 3-P 7.5 AH.
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Michael G

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Once again more info than I expected. Hopefully I'll get a chance to play with this on the weekend.
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Michael G

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aTE - (never mind I found it was torn) can’t believe it I have another question. What did you use to remove the 4 back cover screws? Looks like security hex? If so what size?

Thanks
(Edited)
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(a)Typical Engineer

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I’d forgotten those are security torx bits, off the top of my head maybe T-15. I can check when I get home.

Once you get them out, you can use a center punch to knock out the security pin, then use a regular torx but after that.
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Michael G

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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.
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Michael G

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(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.
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(a)Typical Engineer

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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.
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Michael G

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Got my Fluke working:

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Blue Angel, Champion

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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
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Michael G

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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
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Sam Kaplan

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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?