SLA Batteries, the Peukert Effect on 24v 12Ah

[imorton]

Hello Everyone, I should introduce myself. I just bought a Currie Ezip 750 scooter on sale (new) from Walmart and I am throughly enjoying it, and I am hooked on electric scooters. I can see that a brushless motor and Lipo batteries are in my future.

My issue today is that I have the original new 24v 12Ah battery pack that came with the scooter, and I purchased two 12v 12Ah batteries from eBay to make myself a spare (longer range) battery pack. I have gone through @ three full discharge and full recharge cycles to "break-in" my SLA batteries. I am using a Watt Power meter to track Volts, Amps, Wh, Wpeak, Vminimum, and Total Wh & Ah usage.

Now the more that I research scooters I see that the Peukert Effect will come into play here. My 24v 12Ah battery pack will realistically give me 7-8 Ah due to the high discharge rate (scooter draws @ 10-16 amps while cruising) as I am @ 235 lbs.

My question is, would I be better off by throwing the spare battery pack into my rear basket and swap it into my battery tray when the OEM battery runs low, OR should I put the spare battery pack in the rear basket and actually wire it in parallel with the OEM battery system?

The way I understand the Peukert Effect is that the higher discharge percentage vs the battery pack capacity is what affects the loss. EX: cruising speed uses @10-16 amps, which is drawn from one battery pack at a time, VS cruising speed using @10-16 amps but being drawn from both battery packs simultaneously? Hmmmmm.. decisions decisions...

So if I draw @ 10-16 amps from one 24v 12Ah battery pack, I may only achieve a 40-50% usable Ah capacity (ex: 40-50% of 12Ah = 4.8 - 6 Ah x 2 battery packs = 9.6 - 12 Ah useable), YET if I have both banks tied in together (24v 24Ah) and draw the same cruising amperage, my Peukert Effect will be less, possibly being able to use 60-70% of the whole two battery pack Ah capacity thus achieving more range. (ex: 60-70% of 24Ah = 14.4 - 16.8 Ah useable)

I hope my english is making sense and that I am using the proper battery lingo

PS: after doing some research I see that Lithium A123 cells would be an ideal battery technology for my scooter, just not ideal for my pocketbook, maybe on my next one.. hmmm

[dogman dan]

If you can conveniently parallel the two packs and run them as one bigger battery, DO IT.

You will see a big improvement in the peukerts effect voltage sag. So you will have more volts under load increasing performance. Plus, since the now larger pack is being discharged at a lower discharge rate, it will also deliver more AH with less damage. In effect, each battery now will only discharge 5-8 amps, not 10-16 amps. That's good for them.

However, you will still see longer cycle life if you try to keep discharge to 50-70% maximum. If you discharge deeper anyway, you will see a bit less damage from it if the battery is larger.

When I did the same thing to a lead powered bike, doubling my battery tripled my range. It was very heavy, but worth it.

[The fingers]

Nice rig, room in the trailer or under the seat for the extra pack.

[imorton]

If you can conveniently parallel the two packs and run them as one bigger battery, DO IT.

You will see a big improvement in the peukerts effect voltage sag. So you will have more volts under load increasing performance. Plus, since the now larger pack is being discharged at a lower discharge rate, it will also deliver more AH with less damage. In effect, each battery now will only discharge 5-8 amps, not 10-16 amps. That's good for them.

However, you will still see longer cycle life if you try to keep discharge to 50-70% maximum. If you discharge deeper anyway, you will see a bit less damage from it if the battery is larger.

When I did the same thing to a lead powered bike, doubling my battery tripled my range. It was very heavy, but worth it.

Thanks Dogman for the reply. So it looks like my research about SLA's makes sense

So if I understand correctly, by putting my two 24v 12Ah battery packs in parallel which gives me a combined 24Ah's and running them combined VERSUS running them individually would greatly improve the Peukert Effect, voltage sag, DoD, and cycle life? You said that you got three times the range versus just double? Tell me more about your experience/tips...

Fortunately I now have installed a black wire basket on the rear deck that could handle a 24v 12Ah battery pack, so it would just be a question of running the 10awg jumper wires to the battery tray under my feet.

Now about charging, I have also bought a spare 24v 1.6A battery charger ($12) for the second pack, so I could using the charging port to charge both battery packs, or if charging time is an issue, i could easily disconnect the second battery pack and us the 2nd charger to charge the 2nd (spare) battery pack. Would it make more sense or be better to use one or two chargers?

Thanks again for replying, it's really appreciated... IAN.

[wineboyrider]

I have the same scooter with a bigger controller and run at 13s lipo and the motor holds up well

[imorton]

Nice rig, room in the trailer or under the seat for the extra pack.

Thanks for the reply

My dog was saying to me... "Dad, there's room in this trailer for a battery, groceries, and Me...lollll"

I now have a black wire basket like the front one now installed on the rear deck, so I will look into wiring the two battery packs in parallel.

From what I hear, it should almost triple the range since it would reduce the voltage sag, reduce the ever so important Peukert Effect, and reduce the DoD... Is my thinking correct on this?

[imorton]

I have the same scooter with a bigger controller and run at 13s lipo and the motor holds up well

Wow, tell me more, don't just tease me like this, give me more details

13s Lipo means what exactly, voltage, Ah, discharge etc..... Do you have a link from HobbyKing, since they have Zippy, Nano Tech, Lipoly, etc.. brands, so confusing

Do you have a link for your controller? I would love to run better batteries and not sure how to do it all

You got me curious... IAN.

[wineboyrider]

I have the same scooter with a bigger controller and run at 13s lipo and the motor holds up well

Wow, tell me more, don't just tease me like this, give me more details

13s Lipo means what exactly, voltage, Ah, discharge etc..... Do you have a link from HobbyKing, since they have Zippy, Nano Tech, Lipoly, etc.. brands, so confusing

Do you have a link for your controller? I would love to run better batteries and not sure how to do it all

You got me curious... IAN.

Link for the controller http://www.electricscooterparts.com/spe ... 6volt.html
Item # SPD-36750B
As for the lipo you need to monitor the voltage so as not to go below the recommended lvc for your lipo pack. The lipo rules are never discharge below 3.5 so lvc for 10s lipo would be 35 for 13s lipo 45.5 ( i use 46) I use a simple ebay purchased 15-100v meter for $8.00 that I wire into my battery leads.
here is a link from the same vendor though http://www.electricscooterparts.com/met ... voltmeters
As for the lipo before you dive in learn more about how they operate, but http://www.hobbyking.com is the link for that one. I'll see if i can get some pics up for you too see. Now pulling a load might be a little much for this motor, but I am 205 lbs and run the motor upwards too around 1000w continuous for about 2 miles and the motor holds up surprisingly well. Bear in mind at also that at close to 30 mph it's a bit scary....lol
The controller seems to be a great combination for 10s lipo, but at 10s lipo+++ pops wheelies!

The stock controller that you have can easily run 6s 7s or 8s lipo an example of an 8s lipo pack would be 2 of the 4s car case hobbyking lipos that when in stock sell for $20 some dollars. 4 4s hardcase packs would make a 8s2p that's 8 series cells and 2 parallel cells for a 28v 10ah pack about $90.00 for a pack that won't sag hardly!
As far as brands go anything 15c or higher is great for this use any lipo should work, but also lifepo4 would be a good choice for plug and play. If you have other questions, you could start another build thread and there are lots of people who can help you make the right choices. The

[imorton]

I have the same scooter with a bigger controller and run at 13s lipo and the motor holds up well

Wow, tell me more, don't just tease me like this, give me more details

13s Lipo means what exactly, voltage, Ah, discharge etc..... Do you have a link from HobbyKing, since they have Zippy, Nano Tech, Lipoly, etc.. brands, so confusing

Do you have a link for your controller? I would love to run better batteries and not sure how to do it all

You got me curious... IAN.

Link for the controller http://www.electricscooterparts.com/spe ... 6volt.html
Item # SPD-36750B
As for the lipo you need to monitor the voltage so as not to go below the recommended lvc for your lipo pack. The lipo rules are never discharge below 3.5 so lvc for 10s lipo would be 35 for 13s lipo 45.5 ( i use 46) I use a simple ebay purchased 15-100v meter for $8.00 that I wire into my battery leads.
here is a link from the same vendor though http://www.electricscooterparts.com/met ... voltmeters
As for the lipo before you dive in learn more about how they operate, but http://www.hobbyking.com is the link for that one. I'll see if i can get some pics up for you too see. Now pulling a load might be a little much for this motor, but I am 205 lbs and run the motor upwards too around 1000w continuous for about 2 miles and the motor holds up surprisingly well. Bear in mind at also that at close to 30 mph it's a bit scary....lol
The controller seems to be a great combination for 10s lipo, but at 10s lipo+++ pops wheelies!

The stock controller that you have can easily run 6s 7s or 8s lipo an example of an 8s lipo pack would be 2 of the 4s car case hobbyking lipos that when in stock sell for $20 some dollars. 4 4s hardcase packs would make a 8s2p that's 8 series cells and 2 parallel cells for a 28v 10ah pack about $90.00 for a pack that won't sag hardly!
As far as brands go anything 15c or higher is great for this use any lipo should work, but also lifepo4 would be a good choice for plug and play. If you have other questions, you could start another build thread and there are lots of people who can help you make the right choices. The

Today I added a second battery pack in parallel.... We'll see what range that I get, double or maybe 2.5-3 times the range?

Do you have a link for the Lipo's, as HobbyKing has hundred of batteries sizes and chemistry to pick from?

[999zip999]

One thing at a time. Lot's of info from a lot of different people so do some reading first on your next project. But the volt/ watt metter is a must. Plus you can get some good connecter's maybe 4mm gold and plastic case connector's. Cheap from Hobby king USA.

[dogman dan]

More on what I experienced. At the time I had an EVG electric bike, in 24v. This was a pretty inefficient brushed hubmotor bike, using the heinzmann motor. These motors were internal gear motors, with a very low ratio. So the 24v bike could climb a wall, but never go faster than 12 mph on the flat. The problem was, riding it on trails really sucked a lot of power. So 12ah sla's never worked that good on trails pulling 800-1000w. It quickly sagged the batteries, greatly increasing the peukerts effect compared to riding on the flat at 150w or so.

So I put a rear rack on it, and piled on two more sla's. Now with less peukerts, I had much better range on steep singletrack trails. So this is why I ended up tripling my range. I REALLY needed the bigger battery to tackle the hills at that rate of discharge.

Re other battery choices, I bet a 15 ah lifepo4 battery would get you fantastic range with that scoot. Any kind of lithium should be the next thing for you to get. But if you treat your lead right, you should not have to make that investment till 2014.

[imorton]

More on what I experienced. At the time I had an EVG electric bike, in 24v. This was a pretty inefficient brushed hubmotor bike, using the heinzmann motor. These motors were internal gear motors, with a very low ratio. So the 24v bike could climb a wall, but never go faster than 12 mph on the flat. The problem was, riding it on trails really sucked a lot of power. So 12ah sla's never worked that good on trails pulling 800-1000w. It quickly sagged the batteries, greatly increasing the peukerts effect compared to riding on the flat at 150w or so.

So I put a rear rack on it, and piled on two more sla's. Now with less peukerts, I had much better range on steep singletrack trails. So this is why I ended up tripling my range. I REALLY needed the bigger battery to tackle the hills at that rate of discharge.

Re other battery choices, I bet a 15 ah lifepo4 battery would get you fantastic range with that scoot. Any kind of lithium should be the next thing for you to get. But if you treat your lead right, you should not have to make that investment till 2014.

Dogman, thanks for the reply. Now with the 2nd battery pack in the rear basket, the scooter is definitely heavier. I have noticed the reduced voltage sag already just doing short runs compared to using just one battery pack.

Last night I used just one SLA battery charger and I notice this morning that my charge voltage is a 27.75, so I can use the charger port on the scooter to charge both packs (albeit slower). I guess if recharge time is an issue I can disconnect the second battery pack and use my spare battery charger to charge each pack individually.

Now a question comes to mind? If I use the scooter built-in charger port to charge both paralleled battery pack, is this a good and effective way to charge? (ex: do both packs get charged properly this way?)

Thanks for your replies, IAN...

[Holocene]

Last night I used just one SLA battery charger and I notice this morning that my charge voltage is a 27.75, so I can use the charger port on the scooter to charge both packs (albeit slower). I guess if recharge time is an issue I can disconnect the second battery pack and use my spare battery charger to charge each pack individually.

Now a question comes to mind? If I use the scooter built-in charger port to charge both paralleled battery pack, is this a good and effective way to charge? (ex: do both packs get charged properly this way?)

Thanks for your replies, IAN...

Hi imorton,

It's normal for an SLA charger to 'float' your batteries at 13.8v each, so 27.75v is fine for the your 24v pack. Just don't be surprise when this 'surface charge' quickly burns off on the first use *and I mean in seconds* then the batteries should settle at around 12.8v each, or 25.6v for the pack fully charged.

Both packs will charge fully when paralleled, as long as they both have the same capacity. But if you parallel a 12 AmpHr pack with a 15 AmpHr pack, the 12AmpHr one will be overcharged and get damaged, while the 15 AmpHr battery won't be fully charged. Same thing goes when paralleling old batteries that have lost some capacity with new fresh batteries.

It's okay to charge your SLAs slowly, but the one thing you must not do is charge them too quickly. They can vent hydrogen gas and burst, sending acid flying, if charged too fast. The max charge rate for SLAs is about 1/3 C, so for your 12 AmpHr batteries that would mean max 4 amps charge rate, or for your 24 AmpHr pack no more than max 8 amps charge rate. Slower is actually better, as long as you don't mind waiting. Personally, I have a 3 Amp charger for my 12 AmpHr pack. And it's fine to leave the pack plugged into the charger whenever you're not rolling, as the charger will just 'float' the batteries.

One *bonus* tip for maximizing the life of SLAs: always recharge IMMEDIATELY after finishing a discharge cycle, even a shallow one. Don't leave them discharged. The batteries will sulfate if you leave them for even a short period. Definitely don't want to leave them for hours.

Regarding discharge rate, if you use a 1 C rate (that's 24 Amps from your 24 AmpHr pack) then you'll get about 6 or maybe 6.5 AmpHrs from the pack before it's near empty, which is about 11.5 volts per battery. NEVER take your batteries below 11 volts each, doing that damages them. Yes, and that includes the voltage sag when you punch it

Happier news, if you can limit Amp draw to 0.5 C (12 amps continuous from you 24 AmpHr pack) then you'll get about 8 AmpHrs (33% more) from your pack, maybe even more if you take short breaks. Just watch the volts recover when you stop. You'll see the sag disappear right away, then within about 30 sec or so the batts will steady up. That's their new resting charge voltage, and should tell you how much energy is left.

I have 14 years of experience with these 12V/12A deep cycle batteries on ebikes, and when used within their limits, SLAs can provide 3 years of economical, worry-free service. Abuse them, and they'll be dead in a month.

Any more questions, just ask!

[SamTexas]

Both packs will charge fully when paralleled, as long as they both have the same capacity. But if you parallel a 12 AmpHr pack with a 15 AmpHr pack, then 12AmpHr one will be overcharged and get damaged, while the 15 AmpHr battery won't be fully charged. Same thing goes when paralleling old batteries that have lost some capacity with new fresh batteries.

This is wrong. It's perfectly ok to parallel battery with different capacity. You must be thinking about serializing.

[Holocene]

This is wrong. It's perfectly ok to parallel battery with different capacity. You must be thinking about serializing.

Hi SamTexas,

That's okay if you're paralleling at the cell level. Do you think that's what our new friend has done?

How many cells are in the typical 12V SLA? Just saying, let's keep it simple.

[SamTexas]

How do you parallel SLA at the cell level!!???

It's perfectly ok to parallel lead-acid batteries of different capacity.

[imorton]

Last night I used just one SLA battery charger and I notice this morning that my charge voltage is a 27.75, so I can use the charger port on the scooter to charge both packs (albeit slower). I guess if recharge time is an issue I can disconnect the second battery pack and use my spare battery charger to charge each pack individually.

Now a question comes to mind? If I use the scooter built-in charger port to charge both paralleled battery pack, is this a good and effective way to charge? (ex: do both packs get charged properly this way?)

Thanks for your replies, IAN...

Hi imorton,

It's normal for an SLA charger to 'float' your batteries at 13.8v each, so 27.75v is fine for the your 24v pack. Just don't be surprise when this 'surface charge' quickly burns off on the first use *and I mean in seconds* then the batteries should settle at around 12.8v each, or 25.6v for the pack fully charged.

Both packs will charge fully when paralleled, as long as they both have the same capacity. But if you parallel a 12 AmpHr pack with a 15 AmpHr pack, the 12AmpHr one will be overcharged and get damaged, while the 15 AmpHr battery won't be fully charged. Same thing goes when paralleling old batteries that have lost some capacity with new fresh batteries.

It's okay to charge your SLAs slowly, but the one thing you must not do is charge them too quickly. They can vent hydrogen gas and burst, sending acid flying, if charged too fast. The max charge rate for SLAs is about 1/3 C, so for your 12 AmpHr batteries that would mean max 4 amps charge rate, or for your 24 AmpHr pack no more than max 8 amps charge rate. Slower is actually better, as long as you don't mind waiting. Personally, I have a 3 Amp charger for my 12 AmpHr pack. And it's fine to leave the pack plugged into the charger whenever you're not rolling, as the charger will just 'float' the batteries.

One *bonus* tip for maximizing the life of SLAs: always recharge IMMEDIATELY after finishing a discharge cycle, even a shallow one. Don't leave them discharged. The batteries will sulfate if you leave them for even a short period. Definitely don't want to leave them for hours.

Regarding discharge rate, if you use a 1 C rate (that's 24 Amps from your 24 AmpHr pack) then you'll get about 6 or maybe 6.5 AmpHrs from the pack before it's near empty, which is about 11.5 volts per battery. NEVER take your batteries below 11 volts each, doing that damages them. Yes, and that includes the voltage sag when you punch it

Happier news, if you can limit Amp draw to 0.5 C (12 amps continuous from you 24 AmpHr pack) then you'll get about 8 AmpHrs (33% more) from your pack, maybe even more if you take short breaks. Just watch the volts recover when you stop. You'll see the sag disappear right away, then within about 30 sec or so the batts will steady up. That's their new resting charge voltage, and should tell you how much energy is left.

I have 14 years of experience with these 12V/12A deep cycle batteries on ebikes, and when used within their limits, SLAs can provide 3 years of economical, worry-free service. Abuse them, and they'll be dead in a month.

Any more questions, just ask!

Holocene, a very very big thank you for the reply. You have given me some technical facts that I have not been able to find on the web by myself.

I regards to Peukert Effect, I see the javascript calculators throw out the factor of 1.1, 1.2, 1.3, etc.... and I didn't know what mine would be.

Since I am pulling @ 12-13 amps while cruising full throttle on flat land, I didn't know what Peukert factor to use with a 12Ah or 24Ah battery pack? You surprise me with the 8Ah available from my 24Ah paralleled battery pack

I thought that by paralleling my two battery packs, I thought I would greatly increase my available Ah capacity. I figured if I was pulling 12-13 amps from a 24v 12Ah pack VERSUS 6-6.5 amps from a 24v 24Ah paralleled battery pack.

How much Ah capacity would I be getting from a single 24v 12Ah battery pack if I am cruising and pulling 12-13 amps? How do I calculate the advantage/comparison between 12Ah versus 24Ah?

In regards to charging or combining batteries, I am fortunate that I bought an identical spare battery pack when I purchased the scooter, so I figure they are almost evenly matched in age and of the same capacity.

Your reply did bring up a question though, when people say IMMEDIATELY charge your batteries after a discharge, this is where I get confused. Let's say, my battery packs are fully charged in the morning and I take my bike for a 2 mile run and stop for breakfast, but I want to use it in an hour or so, than go another 2-4 miles to go shopping. Can I just recharge it all up at the end of the day? It doesn't always seem practical or feasible to charge during the day...

Again, a big thanks for sharing your time, knowledge, and experiences... IAN.

[imorton]

How do you parallel SLA at the cell level!!???

It's perfectly ok to parallel lead-acid batteries of different capacity.

Hi SamTexas, I thank you for replying and I am fortunate as I paralleled two batteries of the same capacity and age. Since I have a houseboat and RV, I try to keep things simple and efficient..

IAN..

[999zip999]

Enjoy your scooter and after a 1.5yr or 2yr. with luck. And sla's like to be left in a full state of charge and not left or forgotten on empty. You will have time to read up on a batteries and save money in the battery jar as put your change in every day .50- 2.00.. You have time and it will get you have way there maybe more and wouldn't be so painful.
Bacause a contoller and chargher with the 36v15ah lifepo4 will add up. Welcome to E.S. as it's a hobby now as you have got bitten by the bug, new info cost new money.

[imorton]

Enjoy your scooter and after a 1.5yr or 2yr. with luck. As sla like to be left in a full state of charge and not left or forgotten on empty. You will have time to read up on a batteries and save money in the battery jar put your change in every day .50- 2.00.. You have time and it will get have way there maybe more and wouldn't be so painful.

Hi 999zip999, thanks for reply and I agree, enjoy the scooter and with time by saving my spare change I can get myself either a new scooter or battery technology when the need arises.

I can now see that these electric scooters can be very addictive and there is always the "need for more speed" whispering in my ear ...

[Holocene]

How much Ah capacity would I be getting from a single 24v 12Ah battery pack if I am cruising and pulling 12-13 amps? How do I calculate the advantage/comparison between 12Ah versus 24Ah?

Hi Ian,

To begin, read this reference from the 'Battery University' website:

Calculating the Battery Runtime

The Peukert Exponent for your deep cycle SLAs should be near the average of 1.20 for that chemistry + construction. If you haven't seen it, the Peukert equation is:

C = Iⁿ x T where:
· I is the current (usually measured in amperes)
· T is time (usually measured in hours)
· n is the Peukert number or exponent
· C is the theoretical storage capacity of the battery (measured in amp-hours).

However, to actually calculate the Peukert exponent for your SLAs, you need to do some tests. Basically, you need to measure the time for voltage to drop from fully charged down to a fixed low voltage (ie: from 25.2 to 24.0 volts). You'll need to do this test twice to measure 2 different fixed load (ie: a constant 6 amp draw, and a constant 12 amp draw).

The initial voltage will vary a bit with the temperature and load, but should steady up right away. Just make sure the pack is fully charged when you start the test. Then keep drawing that same steady current until the pack voltage hits your lower limit, ie: 24.0 volts. Carefully record the time in minutes and seconds that it took to discharge from full to cutoff. This discharge time, and the load current, define the Peukert exponent.

You can use a javascript online calculator to solve for the Peukert Exponent of your 24 Ahr pack. If you prefer using some Excel magic, you can calculate everything you'd like to know, and keep records, all in one place with this:

A Peukert spreadsheet in Microsoft Excel format by Chris Gibson

Here's a bit more in-depth discussion about conducting this test. Again, expect your answer after all this to be close to 1.2 so I wouldn't put on extra cycles just to do the test, just try to work it into your daily rides:

Lee Hart on High Current Battery Use

Cheers, and have fun!
Holocene

BONUS CALCULATOR!

Once you have found these two AmpHour ratings, you can use this javascript online calculator to predict how long your battery will last at any given load (note that it calculates the Peukert Exponent for you!)

Calculator | Determine Run Time for Specific Load

[D-Man]

I make my sla battery's puke all the time. Some like to puke in parallel. Some like to puke by themselves. Some just heat up and dry heave.

[The fingers]

I make my sla battery's puke all the time. Some like to puke in parallel. Some like to puke by themselves. Some just heat up and dry heave.

Mine have rot gut.

[999zip999]

What if your stomach boiled and you pruked up your guts would you be dead. Or just lost some life ? Big puke or little puke. Your date say's your out.

[gman849]

Hello,
I'm gman849. This has been a very interesting post. I too recently bought an EZIP 750 on sale from WALMART. I feel good about it since the price recently doubled. Anyhow, I am really enjoying it. I am using it for a commute of about 7.5 miles its just that I just barely make it. This depends on wind conditions its that close...I would like to also wire another battery pack in parallel it would take the stress out of the commute. I would really like to duplicate your set up with the batteries in a rear basket. Is it possible you could diagram and /or explain how you managed the wiring. And how you attached the basket. Thanks I will buy 4 new batteries to start the whole thing fresh....