Help My Scooter is Loosing Its Mojo

[Beagle123]

I was very happy with my scooter's power until just recently. It used to be zippy and it could go 20 miles on a charge. Now it only goes 10 miles, and its lacking power.

I have a 10 mile commute, and I used to be able to go up the slight hill leading to my house at 18 mph. Now when I reach home, its ablout 13 mph. And I know it would be dead shortly if I contiunued to use it.

I'm pretty sure my batteries are the problem.

I have an amp meter hooked up to the batteries. Under maximum load conditions I used to be able to pull 30 amps. Now the maximum is about 25 amps (full throttle uphill). Thiis is weird to me because the discharge rate for SLA batteries is 200+ amps. For example these batteries, which are similar to mine have a discharge rate of 250 amps:

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2176

Also, fetcher posted a video of his vego scooter that had much smaller 10 aH batteries, and he was drawing 60 amps! And they were recycled!

Are my batteries duds?

Another test I did was to hook up a voltmeter, and watch it when I ride. When I was drawing 20 amps, the voltage would sag to 30 volts. I saw it go as low as 28 volts. (I think I even saw it at 22v--it was dark).

What is considered a normal sag? What does this mean?

I bought a desulfator when the problem started, and it seemed to help a little.

These batteries are only about 4 months old. I've always had them hooked up to the charger when not in use. I've drained them almosst completely a couple of times. I took two long rides in one day once. I've been storing my scooter in a hot garage. It get to be perhaps 90-100 degrees on a hot day. I ride it about 10 miles per day.

What went wrong? Fetcher said he was using 6 year old batteries.

 

[Toorbough ULL-Zeveigh]

What went wrong?

This is what went wrong.

I've always had them hooked up to the charger when not in use. I've drained them almosst completely a couple of times. I took two long rides in one day once. I've been storing my scooter in a hot garage. It get to be perhaps 90-100 degrees on a hot day.

Probably charging while hot did more of the damage than 100% DOD but the deep discharge was just salt on the wound.

FWIW I get the same short life out of SLA whenever I've tried them & am impressed if not baffled at how people are getting years of use out of theirs. The fault is all mine because I got spoiled by the absue NiCads can tolerate & wasn't prepared for the amount of babying lead requires.

 

[xyster]

What's the peak voltage of each of these 12v SLAs? I'm wondering if one or more of the 2-volt cells didn't reverse and die during one of the total discharge events.

 

[maytag]

I believe Fechter is using 6 year old Hawker batteries, big difference. Ive used very old Hawker batteries (probably just as old as Fech's) and totally abused them. Let them sit for around a year in a hot garage then found out there was going to be a race in town so started prepping my electric pocketbike. Voltages were roughly 10v,9v,5v,5v (48v system). After a few cycles they were well enough for the races (did great actually). Hawker's are expensive but the pullout recycled ones are a bargain if you can find any. Another good SLA brand are the B&B's. From my experience cheap SLA's out of China are terrible.

 

[safe]

I'm using (3) 12V 38 Ah batteries. That's a lot of lead. The disadvantage is that you carry around a lot of weight, but the advantage is that I usually don't drain down below 12 volts from a starting voltage of about 13 volts. The controller will allow you to drain all the way down to 10 volts. So that's the "problem" most likely. Using small batteries with SLA produces extremely fast wear.

It's time to switch to the newer batteries... either that or design a bike that can carry 86 lbs of lead like mine can. Anything less than what I've done as far as SLA weight will not give you much battery life.

You need to double your battery if you want to go SLA... from 17 Ah to 38 Ah...

 

[Beagle123]

Thanks for all the good advise. I'm really learning a lot about how to make a better bike. Obviously SLAs are very limited.

I guess I'm going to change my plans on my next bike and go straight to lithium.

Tonight I'm going to convert my first bike to 48v and use the 4 batteries that I bought to make my next bike. Hopefully I'll be able to run a few less amps at 48v which will hopefully make these batteries last longer.

WHen they go dead, Maybe I'll try these:

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2538

What do you guys think?

By the way, what is the normal sag voltage I should expect when drawing about 25 amps?

 

[Beagle123]

xter, all the voltages are fine, all batteries are at aabout 13v.

 

[xyster]

By the way, what is the normal sag voltage I should expect when drawing about 25 amps?

If I remember correctly, the 48v 10ah SLA pack on my scooter would sag about 8-10 volts at 30 amps.

 

[TylerDurden]

You might also check the drivetrain. Everything spin freely?

You could whiff the motor too... see if it smells toasty. Safe cooked one of those unites. Maybe they burn fast.

:?

 

[xyster]

WHen they go dead, Maybe I'll try these:

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2538

What do you guys think?

Too expensive; NiMH cells have too many balance issues in large packs like that. I like your 'skip straight to lithium' idea better -- that's what I did.

 

[Beagle123]

Thanks xter,

Update: I installed 3 new batteries that are exactly the same as the old ones. Now it sags from 38.5 volts to about 35 volts. It has noticably more power.

I think this battery situation is another good argument that bikes should be as light as possible. My bike is heavy, and I think that stressed the batteries.

I'm going to try to compensate by adding another battery, making it 48v.


I"m really starting to realize that the best plan is to have a 40 lb bike with a 6lb motor and 15lbs of lithium batteries. Or, like safe said, a 50lb bike a 10lb motor and 90lbs of SLA batteries.

 

[Beagle123]

One more question:

How can I avoid torching these new batteries? You guys said that I shouldn't charge them when its hot, but I can't leave them depleted. That does more damage. When I arrive home and its hot what am I supposed to do?

My normal procedure is to just keep it plugged in all the time. Actually, my normal procedure is to ride it 5 miles, park it for 8 hours, ride it home, plug it in, repeat each day.

Maybe I should try to find an outlet where I park so I can charge it before riding home. This would avoid having it sit with a 70% charge for those 8 hours. Opinions?

Also, I'm using a cheap charger from ebay. Its called "Intelect Charger." When its done charging at 1.8 amps, it holds the voltage at about 40.3 volts. Isn't that too much? Could that be a problem? (13.43v per batttery)

Safe mentioned that he has a battery charger that has 5 stages. Do y'all think I should ge a fancy one?

 

[xyster]

One more question:

How can I avoid torching these new batteries? You guys said that I shouldn't charge them when its hot, but I can't leave them depleted. That does more damage. When I arrive home and its hot what am I supposed to do?

I'd not heard Toortle's admonition against charging hot SLAs before. He could be talking out his butt.

Safe mentioned that he has a battery charger that has 5 stages. Do y'all think I should ge a fancy one?

Doubt it will make much difference. I'd put the money towards better batteries. You're a big EV DIY'er -- DIY yourself a pack of LiMn or LiFePO4 powertool batteries.

 

[Beagle123]

Update: My Scooter Got its its Mojo Back!

I just added a battery to my scooter, and changed to a 50amp 48v controller:

http://tncscooters.com/product.php?sku=101210

Now it SCREAMS.

On the hill that I mentioned where I max-out at 18mph, I just flew up at 23mph, and I could have gone faster. Also, I have to walk it up a lawn area to get to my driveway, and now it drives right up it. When I first tried it I almost ran into a garbage can because it accelerated so fast.

 

[fechter]

Sounds like you got it flying now.

Does the motor get hot?

One reason my old Hawkers have lasted so long is I don't ride that often.
If I was doing daily commutes, I'm sure they would have died long ago.

Overdischarging your batteries can also lead to premature death. They'll last much longer if you never use more than 50% of their capacity. Now you have a bit more energy on board, so if you go slow, you should get more range. It's really really hard to go slow when you have more power though

 

[Eric G]

Nice looking machine you got there Beagle....I've been running 3/12v7.2ah sla on my crate with a 600 watt brushed clyte motor. The batteries are still as good as new ,I got them 5 months ago.My riding habits are much like yours ~5 miles & back daily. I'd most definitely be charging them on that 8 hour stop. I use a 36 volt charger for charging whilst I'm on the road (every chance I get and as soon as I stop if I can) and every evening I use a 1.5 amp 12 volt charger with the batts hooked up in parallel for a slow overnight charge. If possible take the batteries inside from the garage and charge them in an air conditioned area. SLA's hate heat and degrade as the temperature rises esp. ~100 deg F.
Your float charge of 40.3v doesn't sound unreasonable but I wouldn't float them indefinitely,two days or so at most I'd think.

My old Sla's lasted me ~3 years,and two of those bricks are still good but one of the three ended up with a shorted cell and I won't mix old batts with new ones.

GOOD LUCK with the new SLAs

Eric

 

[Toorbough ULL-Zeveigh]

He could be talking out his butt.

No battery likes to get cooked.
When have I steered you wrong b4? :?

Glad you got it all sorted out.
Just to respond to your question about the nimh pack, nimhs fare even worse in the heat.
When the time comes to replace them LiFePO4 would be your best bet.
Valence Saphions come in lead-acid form factors specifically intended for the replacement market.

 

[xyster]

He could be talking out his butt.

No battery likes to get cooked.
When have I steered you wrong b4? :?

SLA's discharge much more energy at higher temps than lower (within a typical cold-day/hot-day range, obviously); and SLA's live longer when kept fully charged. So why wouldn't SLA's charge more completely at higher temperatures too, thus living longer, more fruitful lives?

 

[Toorbough ULL-Zeveigh]

Glad u axed!
From the ole <A HREF="http://www.batteryuniversity.com/partone-13.htm">B.U.</A>

Correct settings of the voltage limits are critical and range from 2.30V to 2.45V. Setting the voltage limit is a compromise. On one end, the battery wants to be fully charged to get maximum capacity and avoid sulfation on the negative plate. A continually over-saturated condition at the other end, however, would cause grid corrosion on the positive plate. It also promotes gassing, which results in venting and loss of electrolyte.

The voltage limit shifts with temperature. A higher temperature requires slightly lower voltages and vice versa. Chargers that are exposed to large temperature fluctuations should be equipped with temperature sensors to to adjust the charge voltage for optimum charge.



A hot battery may fail to reach it's voltage limit, causing severe overcharge.

You should know by now I don't post anything I can't back up.

"Thank you for your co-operation" <(!)>

 

[xyster]

Glad u axed!
From the ole B.U....
You should know by now I don't post anything I can't back up.

Thank you, Turtle, for furthering my knowledge.

Total number of posts; "get him to show his ignorance so I can look smarter" games -- you like to compete on everything, don't you? :lol:

OK, I'm game. Now, let's find a good spot to race our ebikes...

 

[Eric G]

You couldn't have said that better Mr.Toorbough...

Eric

 

[Toorbough ULL-Zeveigh]

Don't wish to take undue credit.
I was citing Isador Buchmann from the Battery University website.

Even prior to the technical explanation why it happens I've seen it numerous times, having replaced a boatload of melted SLA's out of old UPS's (which I'm sure Doctorbass could probably attest to).
I think Maytag has it exactly right it's the cheaper batteries that are the problem & would add something that Mr. Buchmann points out, cheap chargers as well.

 

[safe]

My normal procedure is to just keep it plugged in all the time. Actually, my normal procedure is to ride it 5 miles, park it for 8 hours, ride it home, plug it in, repeat each day.

Maybe I should try to find an outlet where I park so I can charge it before riding home. This would avoid having it sit with a 70% charge for those 8 hours. Opinions?

You have two major factors working against you for SLA:

1. Battery Size is Too Small - So you are forced to work the batteries harder than they like to be used.

2. Long Periods of 70% Charge - Which really kills SLA's because their rate of deterioration is directly related to time spent at less than full charge.

Switch to LiFePO4 and you will be fine... well... your wallet will hurt more and people will now want to steal your bike, but other than that things will be better... :wink:

 

[safe]

Temperature Drop - SLA Voltage Losses

It was 90 degrees or more for the last week or so and it has suddenly dropped down into the 80's. My Project #001 bike had been sitting in the heat with a flat for over a week and I just fixed it today and went for a ride and the voltage was really low. After running the desulfation on the batteries a few times and recharging it's now back to normal. I think what happens is in higher temperature the battery works better, but it also seems to lose charge faster. When the temperature is reduced you would expect that "extra" charge to make the overall battery more highly charged, but it seems to work in the opposite direction in that you seem to lose energy as the battery cools. SLA's seem to have a lot of those "lose lose" situations.

Anyway...

The secret to getting those older batteries back to full energy seems to be the desulphation. Despite what is said of SLA about them NOT wanting to be used much, if you let them sit idle in high heat they seem to lose their charge pretty fast. You can let the battery sit all winter with no ill effects, but in the summer if you don't use it, you lose it. And you lose it again when the weather cools off.

So things are okay again, but when I started the bike this morning and when for a short test ride I came back with a voltage of 12.5 volts which is normally where I end the ride after 10 miles of fun. This was after 1 mile and it seemed low to begin with. After the desulpation and a two recharges it is back to it's energetic self.

Something for me to remember... in the summer, you can't leave your battery doing nothing like you can in the winter...

 

[Eric G]

You'll also find that when using sla batteries during cooler temperatures they seem to loose there umph. When I ride in the fall and winter the sla's act sluggish but once spring and summer arrive they're back to their usual selves again.

Eric