battery charts

10 posts / 0 new
Last post
echuckj5
echuckj5's picture
Offline
Last seen: 11 years 10 months ago
Joined: Wednesday, November 29, 2006 - 07:13
Points: 394
battery charts

Charts, I'd like to meet the people that make charts, I swear, they would make me feel like a genious!

Rode the bike hard today. Hard to get good information. on an electric vehicle. Lot of variables. Batteries have sat unused, gosh, bout a week. That makes a difference. Is it cold, hot, windy, speed. All combined, could have a miserable day, have to push, not ride.

Decided to make a chart. Now if you hav'nt figured it out. Computers don't like me. Cameras don't like me. I have no idea, how to post a chart. I saw the smart people around here talking in some foreign language, html, baloney, bracket this, I see why it did'nt work, ya, scroll down to the bottom, see your mistake? Oh, I understand. Right, I don't get it. So I'm gonna post a chart, chucks way, lots of dashes.

Date----distance---start voltage---end voltage---%of discharge---time to charge
10/10---11.53-------12.97-----------11.84----------25%---------------125 minutes

Forgot to write down the 50% discharded mileage, it was real close to 8 miles. Also, another variable, 18.1 ave speed. My normal average speed is almost 20 mph. Whats that mean, during this test, I had lots of starts and stops. I still tried to maintain 25 mph. A higher ave speed, should get farther.

Now, I posted this already once tonight, held my shift key down for 8 seconds and ending up losing the post. So, you all are going to have to wait till tommorrow, found out my oddysey chart is off, how much, enough. Can I make it? Where? In Dallas there is an airport called Love Field. About 13 miles away. Not a drive I would do on a weekday. The North Texas electric vehicle association is having a meeting there. I have a route that might get me there safely, or might get me run over. Really would like to ride, not load up my pickup, kind of defeats the purpose. So I do some more math, find out, the battery chart is'nt correct. Thought I could make it, maybe glide in the last mile, my route, will be a littly bit longer, than 13 miles. Well, it ends up, their chart is wrong, 12.3 volts is about 1/2 discharged, using their information, and a little math. Then I find that the slope of their line ai'nt right either, I learned how to find slope in algebra one, ninth grade. I find a new slope, shows I might be gliding a little farther than I hope. I hav'nt calculated my glide range, hope I get there, will post tommorrrrow

chuck

jdh2550_1
jdh2550_1's picture
Offline
Last seen: 8 years 6 months ago
Joined: Tuesday, July 17, 2007 - 09:35
Points: 2335
Re: battery charts

Hey chuck - I'll teach you to code in Hyper Text Mark-up Language (HTML) if you'll teach me to weld. Deal? ;-)

John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.

echuckj5
echuckj5's picture
Offline
Last seen: 11 years 10 months ago
Joined: Wednesday, November 29, 2006 - 07:13
Points: 394
Re: battery charts

The battery chart that came with battery, says a lot of things. Has a real nice graph, that charts battery voltage, vs, state of charge. Graph is one inch tall, by, 2 inches wide. Get your binoculars, hard to read. So ya all figured out why the graph is small, eh?

I did'nt like refering to the graph, to find my State of Charge so I calculated it, measured its slope, y=mx+b.
All I need, is two points on the graph. Graph and text says, 12.84 is 100% state of charge, thats one of my points. The graph says that 11.7 volts is 10% state of charge, that is my second point.

Y axis is volts, X axis is percent of charge, easier to use .1 than 10%, so thats what I did. m is the slope. B is the y intercept, at 0% state of charge, the intercept is 11.6v Had to calculate that, extrapolated to guesstimate where a zero state of charge is. Had to start from somewhere, I'll check the value of the actual intecept, later on.. Equation looks like this now,, v=m(sos)+11.6v

Slopes easy, have 2 points, change in y divided by the change in x. (12.84v-11.7v)/(1-.1)=1.267

The graph says, 50% sos is 12.2 volts. The text says, 12.18 volts is 50% sos.

Lets re-arrange the equation now,,(v-11.6)/m=(sos),,hmm, figured m, so its,
(v-11.6)/1.267=(sos)

So what is my state of charge at 50%? Now I need to re-arrange, v=1.267(sos)+11.6, (sos) is .5, lets put it in, solves to 12.23. Close, but, now I have 3 numbers for a 50% state of charge, all using odyssey information.

I know for a fact, I get about 8 miles now, on the first half of my pack,so, I should be getting about 16 miles to a zero (sos), or about 14.4 miles, to a 10% state of charge. Ya, right, nowhere near. Maybe about 13 miles, not tested yet, but probably pretty close. The charts not right, but I think I can correct it.

Now, the news does'nt get better. I don't start of with 12.84 volts, I start with 13 volts. So, using the same facts, lets figure a true slope. (13v-11.7v)/(.9)=1.444

v=1.444(.5)+11.6,,, solves to about 12.32 volts. Thats about my 50% state of charge, right?

So how is this useful, I know now, about how far I can go.

I'm a gonna make a chart, on my next post, my way

chuckie

[b]AGM BATTERIES[/b]

MB-1-E
MB-1-E's picture
Offline
Last seen: 12 years 3 months ago
Joined: Tuesday, May 8, 2007 - 18:31
Points: 385
Re: battery charts

Don't feel bad Chuck, I only know enough HTML and Algebra to be dangerous in either case.
Nice job on the math, you make it look like "plug and play". :)

So, if I've got this straight the "11.7 volts is 10% SOC", is a given and derived from the existing chart and "12.84 volts is 100% SOC", is a given and derived from the existing chart. I should be able to draw a scale for SOC along the horizontal (X axis) evenly spaced, from 100% to 0% in, let's say, 10% increments.

Same for the Voltage along the vertical (Y axis) from 11.5V to 15.5V, evenly spaced at, let's say, 0.25V increments.

Place a point at the intersection of 10% and 11.7V ... First Point
Place a point at the intersection of 100% and 12.84V ... Second Point

Draw a line through both points and be able to determine approximately what the SOC would be at any given voltage.
Or be able to determine that 50% SOC is a certain Voltage.

In the real world, you should be able to fully charge the batts, let it sit a bit or ride until you get the Voltage to 12.84V ... Zero your odometer, ride until you reach the calculated Voltage at 50% SOC then log the miles on the odometer at that point. Then you can make another graph that has SOC going from 100% to 0% on the horizontal (X axis) and Miles on the Vertical (Y axis) ... put a point at Zero miles and 100% SOC and another point at (Miles logged above) and 50% SOC ... draw a line through the two points and be able to approximate the SOC by miles driven.
Or how far you can go at any given SOC.

Now that could be useful information!
I wonder if I can get any information on my batts (probably not) so I can make such graphs or maybe I could start with your graph as a sort of generic thing, tweak it per real world Volts at 100% SOC and go from there.

... or, I misunderstood the whole shebang and will end up in Timbuktu with 0% SOC and have to pedal home ... :(
I'd better bring some water, just in case ... :)

Dave B

MB-1-E
<a href="http://visforvoltage.org/book-page/996-mountain-bike-conversion-24v-3-4h... - Bridgestone MB-1 Mountain Bike</a>

echuckj5
echuckj5's picture
Offline
Last seen: 11 years 10 months ago
Joined: Wednesday, November 29, 2006 - 07:13
Points: 394
Re: battery charts

Now, looking at my microscopic chart, I got the following information

Date Distance Start Voltage End Voltage Percent Discharge Charge Time
10/10 11.53 12.97 11.84 25% 125 minutes

How far can I go, according to the chart,, pretty easy, 11.53 miles/.75,,about 15.4 miles.. to a 10% state of charge, .9*(15.4 miles) is about 13.8 miles.

Now I calculated two slopes, using the odyssey information. 1.267 is right off the chart. How far can I go? (11.84-11.6)/1.267=(soc) is about 19%. 81% of my battery used on this trip. 11.53 miles/.81 is now about 14.2 miles,, to a 10% state of charge,,,,,,, .9*(14.2 miles) is about 12.8 miles,, not so good.

Using the slope of 1.444, the best figure I can come up with, How far can I go?
(11.84-11.6)/1.444 is about a 16.6% state of charge. Used up about 83.4% of my batteries. 11.53 miles/.834 is about 13.8 miles to a dead battery, or, about 12.5 miles, 10% state of charge.

  0% SOC 10% SOC
Chart distance 15.4 miles 13.8 miles
Chart slope distance 14.2 miles 12.8 miles
True distance corrected 13.8 miles 12.5 miles

But, there is more,, The chart says a 100% discharge battery using a 10 amp charger will take 2 hours to charge. It only took SC me 2 hours and 5 minutes to charge 2 batteries, using a 12 amp charger. What, is going here? I am going to convert to watts.

A 10 amp charger, lets call it 13 volts. Puts out about 130 watts an hour, 260 watts in 2 hours.
My 12 amp charger should put out about 156 watts an hour, or about 312 watts in 2 hours.
I have 2 chargers that each charge 2 batteries. About 624 watts total for 2 chargers in 2 hours. I have 4 batteries. Each battery got 156 watts put back into it on this trip.
Each battery is rated, with peukert, at 12 amp hour. 12 volt*12 amps=144 watts.

The reserve capacity, from the chart, word for word, is 27 minutes.
The definition, of reserve capacity, for all batteries is, "The time in minutes that a battery will deliver 25 amperes at 80F and maintain, at least, a voltage of 1.75 volts per cell, (10.5 volts). How many watts is that? About a 150 watts.

Now, in my opinion, this battery is grossly underrated. I have don't have much time, to pleasure ride, and see just how far I can go. At the 11.53 miles I went, I put about 156 watts in, yet, still showed a terminal voltage of 11.84, not a resting voltage, maybe waited 2 or 3 minutes, not 6 hours that odyssey recommends to take a state of charge reading. My last few rides, I've let the batteries sit uncharged for about an hour, usually get about .5 volts back. Using 11.84 volts, adding a 1/2 volt, puts me up to a resting voltage of 12.34 volts. About 1/2 my pack used on a 11.53 mile trip!!!!

I will have to do some real world testing,

Moderator - Hope you don't mind me fixing your tables. Chas S.

chuck

[b]AGM BATTERIES[/b]

MB-1-E
MB-1-E's picture
Offline
Last seen: 12 years 3 months ago
Joined: Tuesday, May 8, 2007 - 18:31
Points: 385
Re: battery charts

Holy Cow ... I'm getting dizzy with all my fuzzy math (mine, not your's Chuck) ... maybe I'll just work hard, earn some more bucks and buy a "Brain Drain" for $175 ... ;)

Wouldn't be near as rewarding as a nice chart that you know is based on specifications and real world tweaking, though".
... and we could even laminate them, make it credit card size and bring a magnifying glass so we can read 'em (time for me to get some new glasses).

Dave B

MB-1-E
<a href="http://visforvoltage.org/book-page/996-mountain-bike-conversion-24v-3-4h... - Bridgestone MB-1 Mountain Bike</a>

echuckj5
echuckj5's picture
Offline
Last seen: 11 years 10 months ago
Joined: Wednesday, November 29, 2006 - 07:13
Points: 394
Re: battery charts

So I get to thinking, Odyssey has a real good warranty on their batteries, 2 years on the pc 625, 3 years on their larger batteries, 5 years on their largest batteries. When I returned my bad battery last week. They put it and its mate on the load tester, said, yep, that ones bad, walked to the back, got me a new battery, load tested it, gave it to me, with a duplicate reciept. Said come back anytime. NOOO CHARGE!

So the cutoff voltage should be 10.5 volts, not 11.6 volts. A dead battery is when it won't deliver current, dangerous area to play in. But a better chart maker.

y=mx+b,,V=m(sos)+10.5,, at 10.5 state of charge should be zero. I am going to use 10.75 as my second data point. 13 volts - 10.5 volts is 2.5 volts. 10% of 2.5 volts is .25 volts. Add .25 volts to 10.5 volts, is 10.75 volts. Data points, (13v,1) and (10.75v,.1)

m=(13-10.75)/{1-.1)

m=2.25/.9 = 2.5, this is my new slope.

v=2.5(sos)+10.5 On my 11.53 mile trip, I measured an 11.84 reading in volts. Lets find my state of charge, re-arrange, (sos)=(v-10.5)/2.5

(sos)=(11.84v-10.5v)/2.5,,,,,about a 53% state of charge.

Ok, got some more data. Remember when my battery was bad. Now this is pure speculation, I highly doubt, I can get, 11.53 miles/.53 = 21 miles outa this pack. I do realize, I've been cutting myself short. Took a bad battery, basically, it was dead. It's partner was doing all the work, pushed me 10 miles on its own, the good battery in the pair, could'nt supply much after 11.2 volts. Now this battery, was discharging heavily. A little more peukerts than the front pair which had a voltage of 11.78 on that trip. I'm gonna post, find that data, its in a scott motor thread.

chuck

[b]AGM BATTERIES[/b]

echuckj5
echuckj5's picture
Offline
Last seen: 11 years 10 months ago
Joined: Wednesday, November 29, 2006 - 07:13
Points: 394
Re: battery charts

This is the information I got, a week or so ago, when I discovered I had a bad battery.

-Starting voltage: 12.97 volts
-Ave speed: 18 mph
-Top speed: 28.5 mph
-At mile 7.49,, the rear pack was at voltage 12.2 after stopping and letting the
-voltage stabilize for a couple minutes, very good results, almost 2 miles farther than -before.
-At mile 8.29, rear pack voltage was 12.1 ,,. Was at my parents house, visited with
-Dad, planted some more in the garden, stayed about an hour, pack voltage, rear, had
-risen to 12.25 volts.
-At mile 10, rear pack voltage, just plummeted, little power, hmm, something wrong.
-Right rear battery is warm, all three others are normal. Limp home at about 15 mph.
-At mile 11.84, I am home. Rear pack voltage, after a few minutes of stabilizing, is
-11.2 volts. Front battery pack is 11.78 volts. That one battery is warmer, put a fan
-on it, let it cool, then charged it up. Both packs took the same amount of time to
-charge, pack with bad battery took a couple minutes, maybe five minutes, longer to charge.
-The bad battery was slightly warm, other three normal.

Went 11.84 miles, front pack is 11.78,
Rear pack, bad, is at 11.2. Rose .15 volts in an hour. Make this ride often, the rear pack voltage normally rises about a 1/2 volt, in an hour. Both packs took the same amount of time to charge. This rear battery was really working hard. Pushed me 10 miles, kept its current flowing.

Got things to do, let me think about this.

chuckie

[b]AGM BATTERIES[/b]

echuckj5
echuckj5's picture
Offline
Last seen: 11 years 10 months ago
Joined: Wednesday, November 29, 2006 - 07:13
Points: 394
Re: battery charts

Thanks Chas, for the chart It sure is easy, to make a chart. For you!

I've been thinking about it. On my bike, 2p2s. 24 volt system. About 30 amps, cruising. That means each battery is providing 15 amps at 12 volts. My voltage drop is about from .4 to .7 volts at cruising, per 12 volt pack, or about .8 to 1.4 volts for the 24 volt pack.

I'll stick with the 12 volt reading. If 10.5 volts is a dead battery, one that won't supply enough current to maintain my speed, I should see that at about 11.2 volts. Hmm, subtract the .7 volt (worst case scenario) drop from the voltmeter reading of 11.2 volts at cruising. And, that, is, just about what I saw when my battery was bad, the good battery, at 11.2 volts could'nt supply,,wait a minute, not 15 amps, the 30 amps it needed to.

All in all, what's in my hand? That is about the question. Hard to answer. Seems to me, 11.2 volts, cruising, should tell me, I'm about to need to....push. Lets call it 11 volts, heck, I only had one battery. So cruising, a dead battery is reading 11 volts on my voltmeter.

Using my 2 voltage drops, fresh batteries, and about dod batteries.

I need a set of data to find my slope. V=m(sos)+b. b is 11 volts.
m=change in volts/change in state of charge. m=(12.3v-11v)/(1-0)=1.3***(12.3v is worst case scenario)

The equation is V=1.3(sos)+11.0v
This is for my conditions, my batteries. While under way. Not resting. I have been reading the chart wrong, thinking that moving along, I should be stopping my ride at 11.5 volts. The chart says to wait 6 hours before taking a reading from the batteries, to determine a state of charge. Yea, maybe bring a 6 pack with me, an umbrella, sit on the curb, to take that reading

What is my 50% state of charge now (while moving). V=1.3(.5)+11.0v = 11.65 volts,,durn, thats about where I was cutting my ride off. Now I have an equation that works for, ME.

Thanks for bearing with me, I have never owned an electric vehicle, other than a few trolling motors. I have bought just a few wet cell trolling motor batteries, they take abuse, last for years. I have bought more than a few gel cell trolling motor batteries, 3 lasted one day, the rest, maybe 2 seasons. Lots of agm batteries, they run the equipment in the field, back when I worked hard, lasers, geodemeters, topcon, surveying equipment. Abused the agms', they made me money, go home early, no, time is money, frying a battery while working, is usually better than going home early. Now, pushing my bike home, 5 miles, 10 miles, and its 105 degrees, nah, I'll see how this new chart works, should be plenty of room for error, using the worst case scenario.

time to learn that new foreign language that is infiltrating our shores, html. If you can't beat em, outlearn em.

chuck

[b]AGM BATTERIES[/b]

echuckj5
echuckj5's picture
Offline
Last seen: 11 years 10 months ago
Joined: Wednesday, November 29, 2006 - 07:13
Points: 394
Re: battery charts

The whole reason I started this thread, was I wanted to ride my bike to the North Texas ev club meeting at the downtown airport. I had a perfect route, of 15 miles, mostly safe. Maybe only a mile I really did'nt like. Lot's of turns though, lot's of side streets. Looks like I would'nt of had to of glided, maybe, maybe not. My new gear change has really helped mileage. I did'nt go.

My brakes went out. Hayes mechanical disc brakes, MX2's, a very popular brake, not a store in town had replacement pads. With the gear change, came an increase in kinetic energy, a fun one. Hard on the brakes. I have an old, 1 ton, dually, dodge ram, diesel pick up. I did'nt want to be laughed at, hauling my little bike, in the truck, to the meeting. Looks like the next meeting, will be closer. I'll take pictures, some real nice ev's in this town. Where I live, there is no shortage of electrical engineers. Richardson Texas is the home of Texas Instruments. Lot's of plastic pocket protectors, around here.

chuck

[b]AGM BATTERIES[/b]

Log in or register to post comments


Who's online

There are currently 0 users online.

Who's new

  • Nickel
  • Florix
  • gray62
  • gregorbrown
  • jimtmcdaniels

Support V is for Voltage