* * * The 1000 Mile Club * * *

[xyster]

At only 12 volts discharge that's pretty shallow and should not wear the battery very much.

12.0 volts is not shallow. Mine are about 80% drained by that point. And 500 full charge cycles isn't realistic either.

 

[safe]

12.0 volts is not shallow. Mine are about 80% drained by that point. And 500 full charge cycles isn't realistic either.

For SLA? You use a different battery chemistry. The lowest that my controller will allow is 10 volts. I know I start at 13 volts at the beginning and so I figure that I'm only allowing it to drop 1 volt out of a possible 3 volts.

2000 miles / 10 miles = 200 cycles so far...
.

 

[xyster]

12.0 volts is not shallow. Mine are about 80% drained by that point. And 500 full charge cycles isn't realistic either.

For SLA? You use a different battery chemistry. The lowest that my controller will allow is 10 volts. I know I start at 13 volts at the beginning and so I figure that I'm only allowing it to drop 1 volt out of a possible 3 volts.

Have you bothered to measure the voltage on your SLAs individually? Ride until you get to 12.0 volts, then see how much farther you can ride. With 38ah (or whatever they are) SLAs, your C draw is much less, so maybe you can ride yours' all the way down to 10.0 volts -- which still won't buy you much more range. Both my 10ah and 12ah SLAs are 80% depleted by 12.0 volts, and beginning to sag so bad the ride might as well be over.

 

[safe]

With 38ah (or whatever they are) SLAs, your C draw is much less, so maybe you can ride yours' all the way down to 10.0 volts -- which still won't buy you much more range. Both my 10ah and 12ah SLAs are 80% depleted by 12.0 volts, and beginning to sag so bad the ride might as well be over.

I stop early. I never let the bike get to the voltage cutoff and the lowest I've ever gone is 11.5 volts. I do think that 80% is probably being used up, but it's that last 20% that actually does the damage. As long as I abandon the last 20% and keep the voltage to 12 volts as a minimum it should extend the life of the batteries. Even if I only got 500 "good" cycles (after all batteries tend to suffer a slow death) that still means:

500 cycles * 10 miles = 5000 miles.

So I'm only half way to the end of these batteries even in the worst case scenario... after all... they only cost $138. :wink:
.

 

[oatnet]

With the use of a desulfinator, couldn't you theoretically make SLAs last forever? I was impressed when my desulfinator recovered a few of my dead car batteries to better than new, but of course an ebike's discharge is much much deeper than a typical car battery.

-JD

 

[safe]

With the use of a desulfinator, couldn't you theoretically make SLAs last forever?

My charger is the four phase type.

1. Desulphate.

2. Charge at either 2, 6, or 10 amps. (selectable)

3. Step down the amps when it nears full.

4. After being full... wait a while and then cycle a float charge on and off.

My guess is that these newer chargers do a better job than the old ones and with luck I'll get a minimum of 5,000 miles out of my batteries and at best the 10,000 mile "dream" limit.

 

[Johnbear]

I have been using one for a month now. I cannot tell yet what the results are but the batteries are over a year old and are going strong. There must be over 250 cycles on them by now. I will keep testing and see how they go. I hope they last a long time. We will see if i can reach the 10,000 mile, 16,000 km mark - will take a couple of years because I have 5 e-bikes.

 

[Toorbough ULL-Zeveigh]

This information was obtained from the Panasonic Sealed Lead Acid Batteries Technical Handbook, 1998-1999 It applies to most sealed lead acid batteries.


Cycle Life
The cycle life is the number of charge, discharge, or rest cycles a cell or battery can provide. Cycle life is usually expressed by the number of cycles available before duration of discharge decreases to a half of the initial value.
Cycle life of the battery is dependent on the depth of discharge in each cycle. The deeper the discharge is, the shorter the cycle life (smaller number of cycles), providing the same discharge current. The cycle life (number of cycles) of the battery is also related to such factors as the type of the battery, charge method, ambient temperature, and rest period between charge and discharge. Typical cycle-life characteristics of the battery by different charge/discharge conditions are shown by the Figures. This data is typical and tested at a well-equipped laboratory. Cycle times are different for each battery model. Cycle times are also different from this data when using batteries under real conditions.

 

[safe]

Cycle Life
The cycle life is the number of charge, discharge, or rest cycles a cell or battery can provide. Cycle life is usually expressed by the number of cycles available before duration of discharge decreases to a half of the initial value.
Cycle life of the battery is dependent on the depth of discharge in each cycle. The deeper the discharge is, the shorter the cycle life (smaller number of cycles), providing the same discharge current. The cycle life (number of cycles) of the battery is also related to such factors as the type of the battery, charge method, ambient temperature, and rest period between charge and discharge.

I've got a pretty big battery pack (3) 38 Ah SLA. I usually start at about 13.2 volts and end before 12 volts. Today I went 12 miles and ended at 12.2 volts and that's a typical ride for me because I can just start to feel the power going away and in my opinion I just don't want to ride the bike when it's underpowered. (note: my battery seems to have a higher voltage than some others I've seen published elsewhere)

So my question is this:

"How do I know what percentage of the battery capacity that I've used?"

...the chart showed everything in terms of total capacity, but what does that mean? Can I estimate capacity by my ending voltage? If my controller has a cutoff voltage of 10 volts then I'm ending my rides well ahead of the cutoff value, but would that cutoff be where the "capacity" figure is calculated?

I've got a 40 amp controller, but I also have gears and do a good job of screaming the hell out of the motor all the time. This results in me spending a larger percentage of time in the higher rpms where the current drops below 40 amps. So I figure my average is about 30 amps drawn with more when on a hill. (and have no choice)

The chart below is for a similiarly sized battery (40 amp) but a different brand than mine...

 

[xyster]

Those are voltages under load, correct?

I've looked, but never found, a 'resting voltage versus capacity' discharge chart for SLAs. I'll continue to maintain 12.0 volts resting is about 80% DoD. Maybe someone with a CycleAnalyst or battery analyzer would be willing to make such a chart?

 

[Toorbough ULL-Zeveigh]

<A HREF="http://www.batteryuniversity.com/parttwo-41.htm">A lead-based battery must always have a charge and the open terminal voltage should read 2.0V/cell and higher. If below 2 volts, a sulfation layer builds up that makes a recharge difficult, if impossible. An open terminal voltage of 2.10V/cell indicates that the battery is roughly 50% charged.</A>

Since you go below 12.6V/50%DoD then you're cycle life will be less than 500 cycles at best.

 

[xyster]

<A HREF="http://www.batteryuniversity.com/parttwo-41.htm">A lead-based battery must always have a charge and the open terminal voltage should read 2.0V/cell and higher. If below 2 volts, a sulfation layer builds up that makes a recharge difficult, if impossible. An open terminal voltage of 2.10V/cell indicates that the battery is roughly 50% charged.</A>

Interesting. So for 12v SLA's, 12.0 volts is ride-over time, and 12.6 volts is 50% DoD -- that jives with my experience.

 

[Eric G]

Here's the gauge for open circuit terminal voltage for my
GS portalac Sla batteries.I've seen other gauge graphs for sla's and they're all pretty much like this one...

Eric

 

[safe]

I'm up to 2000 miles and will report how far I go...

 

[Toorbough ULL-Zeveigh]

I'm up to 2000 miles and will report how far I go...

But where are you to go once you've gone too far?

I was going to add that Fechter's Law (or whoever it is that his sig is quoting) trumps all.

 

[Johnbear]

Quoted from http://www.electricrider.com/batteries/index.htm
"I gathered the informtion below from alot of different places on the internet and have put them together in a way I hope will be informative for the user at large. It should be noted that the cycle lifes stated are for general purpose batteries which are the ones commonly used because of low cost.

Some batteries like the B&B Batteries EB Series of batteries are made for high cycle life with deep discharge and will provide more cycles then standard batteries when used for electric transportation needs. The voltages listed below are still valid for all SLA batteries.

This Information is for Sealed Lead Acid (SLA) Batteries Only:

12 Volt batteries have 6 cells each
24 Volts = 12 cells
36 Volts = 18 cells
48 Volts = 24 cells
Fully charged cell voltage = 2.1 Volts
Nominal cell voltage = 2.0 Volts

The recommended end-of-discharge voltage for sealed lead-acid is 1.75 Volts per cell. The discharge does not follow the preferred flat curve of nickel and lithium-based chemistries. Instead, Lead-acid has a gradual voltage drop with a rapid drop towards the end of discharge.

The sealed lead-acid battery should not be discharged beyond 1.75 Volts per cell, nor should it be stored in a discharged state. The cells of a discharged lead-acid sulfate, a condition that renders the battery useless if left in that state for a few days. Always keep the open terminal voltage at 2.10 Volts and higher.

The cycle life of sealed lead-acid is directly related to the depth of discharge. The typical number of discharge/charge cycles at 25°C (77°F) with respect to the depth of discharge is:

* 50 - 100 cycles with 100% depth of discharge (full discharge)
* 150 - 250 cycles with 70% depth of discharge (deep discharge)
* 300 - 500 cycles with 50% depth of discharge (partial discharge)
* 800 and more cycles with 30% depth of discharge (shallow discharge)

Cycle life measured until 80% of original capacity can no longer be recovered by charging."

 

[xyster]

These must be voltages under load. Per the other graphs, and my experience, there's no way 2.0 volts per cell (12.0v for a 12v SLA) is above 50% capacity -- more like 20% capacity. The cycle life info sounds about right though.

This one looks about right to me for open-terminal voltages:

 

[Eric G]

I think alot has to do with plate construction... lead-calcium plate grids (which is what my Sla's are made of) raise the voltage by 5%to 8%

When my 36 volt pack of sla are charged up and have rested for 12 hr. the voltage is ~39.7 volts.

Eric

 

[safe]

I start out at a resting voltage of about 13 volts (2.1 volts per cell) and end at 12 volts. (2.0 volts per cell) So I don't think that I'm cutting off at much worse than about 50% capacity most of the time. I usually don't ride the bike until it can't do anything anymore. (then it's no fun) Once I hit about 8 miles then I head home (usually starting from my track) and it's about 2 miles to get home. I very often end the ride right at 10 miles which for (3) 38 Ah batteries is not very long. My rides are nothing more than 2 miles to the track, six or seven laps and then 2 miles to get home... 30 minutes of riding.

There is an advantage in observng and obeying your SLA sag... by ending your ride early you do preserve your batteries.

So "sag" might be like "nag" which is the batteries saying:

"I'm tired, I want to go home and rest."

 

[Toorbough ULL-Zeveigh]

These must be voltages under load.

Defiantly.
Need to keep clear whether referring to voltage under load or no load.

Safe was specifically asking for 'resting' or open-terminal voltages (which isn't a particularly accurate method of gauging charge level but will do as a rule of thumb), so that's what I tried to provide.

As with any battery it's more meaningful to measure the voltage under load because sometimes a dead battery will still measure full voltage but can't provide any current beyond powering a voltmeter.

 

[xyster]

As with any battery it's more meaningful to measure the voltage under load because sometimes a dead battery will still measure full voltage but can't provide any current beyond powering a voltmeter.

Perhaps more meaningful, but also less practical. Open circuit voltages provide a common reference for all of us without on-board current-measuring capability, as well as those with, as well as standardizing the reference for different system current limits.

 

[safe]

In my case I keep improving the bike over time (Project #001) so the bike gets faster and faster. In that sense I have a hard time noticing the battery getting any weaker. I think that the improvements are now fewer and far between on the bike compared to the early stages so from now on out I should be able to observe changes in the health of the battery. (this new transaxle with precision bearings is so much smoother than previous versions that I'm getting much more power)

One thing is that higher temperatures allow the battery to work better, but those same higher temperatures make the motor work worse. So in the summer I have more power at the beginning (when the motor is still cool) and a longer range if I am careful about motor overheating. In the winter (cooler) rides the battery is weaker, but the motor doesn't heat up as much and so it can run stronger longer.

So the two factors seem to operate in opposite directions.

The best rides are when the temps are in the 80 degree range both for performance and rider comfort.

 

[miro13car]

Hi all!
Count me into 1000mile club. I got 7100km right now on 500W restristed Canadian version Tidal Force. I still use original hub wheel NMH battery along with newly constracted e-moli based 9Ah pack of my own making.
Typical daily trip 16km , on weekend typical trip 50-60km.
MC

 

[safe]

I just passed 2,500 miles.

 

[fechter]

I just passed 2,500 miles.

Slowly?