Capacitors and SLAs

cannonball2

cannonball2

Well-Known Member
Some where I read of adding capacitors to SLA batteries to improve performance. Would some one explain the advantage ,what caps to use, wiring, etc.

Thanks!
 
I suppose Theon is on the right track. I've never heard of this but I'd speculate that the 'advantage' might be the ability of the capacitor to store energy from the battery then give it up quickly when needed without overheating and destroying itself.

But I'm sure you couldn't get any effect from a capacitor like type that is to be found in small electronics. They couldn't possibly hold enough charge to be of any use.

A capacitor that would actually hold any usable amount would probably be as big as your bike.

I'm no expert on this. But I'll bet I'm in the right ballpark.
 
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Cant remember where I read on this but the jist was it was a form protection against to high a momentary amp draw which is hard on SLAs. I don't think it added much capacity. I would think caps similar to those used to start electric motors might have been used. Seemed the article I read also indicated a more regulated voltage from the battery bank. If the caps were similar to motor start units then they would be small enough to be practical to use.
 
cannonball2 said:
Cant remember where I read on this but the jist was it was a form protection against to high a momentary amp draw which is hard on SLAs. I don't think it added much capacity. I would think caps similar to those used to start electric motors might have been used. Seemed the article I read also indicated a more regulated voltage from the battery bank. If the caps were similar to motor start units then they would be small enough to be practical to use.
Click to expand...

This would certainly seem to make sense.

But I'm afraid that I'm already in over my head. For instance, I don't even understand why caps would be needed to start an electric motor.

Some folks who know more might come along with something that you can sink your teeth into.

I"ve never priced capacitors. Can enough be had without spending an arm and a leg? If so, you might need to do some experimenting.
 
It's a long time ago, I studied these things, and they may have improved in 20 years, but I doubt your just looking for a motor start capacitor, and your right in all areas, but you'd need a fair capacitor to make any real difference.
 
Look I just think if it it was that cheap, why wouldn't be it done by manufactures.
In early electric cars, they were talking about running big capacitors, for extra sudden torque requirements, but they weren't just 40uF. They were talking revolutionary super capacitors, that they found would only work at absolute 0. (colder than Alaska).
AC and DC are very different, and the discharge of a capacitor can be very quick.
Which suits 50/60 hz.
But you need a huge capacitor to maintain any sort of current for any more than an instant.
How ever the high draw on a DC motor is prolonged untli it reaches 'speed'.
Where as the AC capacitor is constantly being recharged every 20m/s.
But if you do find a really big capacitor it will go in parallel, and hope to hold your voltage up under very short power bursts.
I'm a sparky by Trade, but don't use it so much anymore, so you'd be better of doing some proper DC motor theory/ AC motor theory, and then you'll know what your looking for.
But I'd be buying as many of those little 40uF capacitors as you can fit on your bike.
Sorry.
Brushless motors are usually kinder on battery's, but the controllers are a lot more expensive. 'Inverter Technology'. and an inverter will have some big Cap's in it. but working to Filter the AC, so constantly charging/discharging.
 
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Well it was a good thought any way. My one experience with this concept was with a particular RC receiver. It was prone to brown out and temporary loss of signal under high load from the servos. The addition of a capacitor totally solved the problem stopping the low voltage spike. Guess the capacity needed for the SLAs would be too great to be practical.
 
Probably cheaper/easier just to have more battery capacity.
You would find on your RC that the Cap was likely only feeding the receiver, not being drained by the servos.
 
Some of the KERS systems (Kinetic Energy Reuse System, or something to that effect) used in Formula 1 Racing for a season involved capacitors. See what you can find on KERS. There was also a KERS system that involved a high speed flywheel.
I know that some older televisions and older computer monitors used very large capacitors (large enough to deliver a fatal shock). You may be able to use them as a source of powerful capacitors.
 
These are quite doable. It would take 5/battery(13.5v) making a 100F pack. They are small about C cell size. Basically unlimited cycles. Price is not bad@ $65/pack. Should pack a whallop of surge amperage. Not sure what this means in the real world usage. I guess the batteries become chargers for the caps?
 
Sorry I didnt' read the second link,
interesting and something like this may have an effect,
However I feel the advertising is a little misleading.
For example running a motor bike, the charge coil would be continuously charging, I've found a lot of bikes run just fine with out any sort of battery, only problem is you may blow your head light from too higher voltage if you use hi rev's, the battery is really only a Regulator in this instance, and the Cap's are just doing the same.
Advantage of more batteries for $ outlaid is you increase your overall Ah capacity far more than the capacitor will, as well as increasing max current draw.
I'd be thinking of putting the $65 in to more Batteries.
 
Would be curious to see how long the Cap's wind that car over for?
If car is hard to start, the capacitor would not do it.
On an electric vehicle, your looking for a sustained high Amperage.
 
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