Go Back   EcoModder Forum > EcoModding > DIY / How-to
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 04-15-2013, 08:54 AM   #1 (permalink)
EcoModding Lurker
 
Join Date: Apr 2013
Location: Miami, FL
Posts: 6
Thanks: 2
Thanked 0 Times in 0 Posts
Audio system capacities to solve voltage sag?

I couldn't find anything about this on the web, but I am running 6 8v lead acid batteries in my golf cart based commuter. During acceleration, as expected, voltage drops and then rises and stabilizes when I get to top speed.

My question is whether I can effectively increase the range (and potentially the life of the batteries) by installing car audio capacitors across every 12v bank of batteries to reduce voltage sag? My guess is that it would improve performance as well.

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 04-15-2013, 10:36 AM   #2 (permalink)
Master EcoModder
 
Join Date: May 2012
Location: USA
Posts: 2,643
Thanks: 1,502
Thanked 279 Times in 229 Posts
Yeah, you can buy some large off the shelf caps now. I have a 10 farad on my subs, but Ive seen up to 20 for less than 100 bucks.
  Reply With Quote
Old 04-15-2013, 10:54 AM   #3 (permalink)
EcoModding Apprentice
 
Join Date: Mar 2012
Location: Adelaide, Australia
Posts: 235

F Truck - '77 Ford F100 2x4, single cab, lwb
90 day: 8.75 mpg (US)

Bombodore - '98 Holden Commodore Exec Wagon
90 day: 21.35 mpg (US)

Civic - '93 Honda Civic GL
90 day: 36.62 mpg (US)

Jim The Prius - '09 Toyota Prius
90 day: 36.66 mpg (US)
Thanks: 154
Thanked 62 Times in 35 Posts
Capacitors drain their power very quickly, which is good for an audio system when you have a sharp bass hit that last for less than a second but i doubt it would do much for your car when you need the power during acceleration, unless you got a really really big cap or lots of them... in which case its probably cheaper/more effective to just get more/bigger batteries (which funny enough is also what i recommend for customers audio systems if they listen to music with more than just sharp bass hits (aka pretty much all music))
__________________


(Posted in 2020) 2009 Prius Off Road project: https://ecomodder.com/forum/showthre...ide-38366.html

(Posted in 2012) 1977 F100 Project: http://ecomodder.com/forum/showthrea...tml#post310326
  Reply With Quote
Old 04-15-2013, 12:17 PM   #4 (permalink)
EcoModding Lurcher
 
mort's Avatar
 
Join Date: Dec 2010
Location: Los Angeles
Posts: 333
Thanks: 148
Thanked 109 Times in 80 Posts
Quote:
Originally Posted by Furyous View Post
I couldn't find anything about this on the web, but I am running 6 8v lead acid batteries in my golf cart based commuter. During acceleration, as expected, voltage drops and then rises and stabilizes when I get to top speed.

My question is whether I can effectively increase the range (and potentially the life of the batteries) by installing car audio capacitors across every 12v bank of batteries to reduce voltage sag? My guess is that it would improve performance as well.
Hi Furyous,
Audio caps for cars are rated at car battery voltage (16 volt is the nearest standard voltage), so there doesn't seem to be an efficient way to use them for a 48 volt system.
And...
Each farad can store about 100 joules at battery voltage (about 14.5 volts) 1 joule is 1 watt-second. So 1 F could store 100 watt-seconds. That's if you can convert the whole charge down to 0 volts. I guess you'd better assume you could use the top 30%, 14.5 volts down to 10 volts - you need 3 times as many capacitors.

The Stinger seems to be a combo capacitor & lithium battery which emulates 50 F.
If you attached 60 of these to pairs of batteries, 15 for each pair, you'd gain 750 farad at 48 volts. If you could use about a third of that (14.5 v down to 9.6 v) it would provide about 25,000 watt second. Or 20 amps at about 48 volts for 26 seconds. 20 amps might be noticeable and 26 seconds might be how long you want help accelerating. Or it could provide as an additional 100 amps for 5.2 seconds for climbing short steep driveways.
And that would only cost $11,700.
-mort
  Reply With Quote
The Following User Says Thank You to mort For This Useful Post:
Furyous (04-15-2013)
Old 04-15-2013, 06:24 PM   #5 (permalink)
Master EcoModder
 
Join Date: May 2012
Location: USA
Posts: 2,643
Thanks: 1,502
Thanked 279 Times in 229 Posts
I wouldnt worry. Just get bigger batteries or use less amps.
  Reply With Quote
Old 04-16-2013, 08:33 AM   #6 (permalink)
EcoModding Lurker
 
Join Date: Apr 2013
Location: Miami, FL
Posts: 6
Thanks: 2
Thanked 0 Times in 0 Posts
So, even if I get 4 2.5 farad capacitors and wire them up to each 2 batteries, there will be no benefit, even with regards to battery life?
  Reply With Quote
Old 04-16-2013, 09:06 AM   #7 (permalink)
Master EcoModder
 
Ryland's Avatar
 
Join Date: Jan 2008
Location: Western Wisconsin
Posts: 3,903

honda cb125 - '74 Honda CB 125 S1
90 day: 79.71 mpg (US)

green wedge - '81 Commuter Vehicles Inc. Commuti-Car

Blue VX - '93 Honda Civic VX
Thanks: 867
Thanked 433 Times in 353 Posts
They would help, but not for the reasons you'd think, the motor draws electricity from the battery in pulses, every movement of the motor changes what coils are connected via the brushes, lead acid batteries do not like these pulses and it starts to act like they are being discharged at the rate that is the peek of the pulse, so if you put a capacitor in there it evens out the peeks and valleys and the battery ends up with less stress, giving a longer range and longer over all battery life.

Bottom line tho is that if you are putting a high enough load on to see your 48v pack sag to under 40v, then that right there is shortening your range and battery life.
  Reply With Quote
The Following User Says Thank You to Ryland For This Useful Post:
Furyous (04-16-2013)
Old 04-16-2013, 02:11 PM   #8 (permalink)
EcoModding Lurker
 
Join Date: Apr 2013
Location: Miami, FL
Posts: 6
Thanks: 2
Thanked 0 Times in 0 Posts
Thanks! That hasn't been a problem. The pack was new in October and I rarely let the resting voltage drop below 50, nor have I seen voltage drop below 48 during acceleration.

So what you are saying is $100 worth of capacitors might be worth a few extra months if battery life? Why wouldn't everybody do this?
  Reply With Quote
Old 04-16-2013, 09:27 PM   #9 (permalink)
Master EcoModder
 
Ryland's Avatar
 
Join Date: Jan 2008
Location: Western Wisconsin
Posts: 3,903

honda cb125 - '74 Honda CB 125 S1
90 day: 79.71 mpg (US)

green wedge - '81 Commuter Vehicles Inc. Commuti-Car

Blue VX - '93 Honda Civic VX
Thanks: 867
Thanked 433 Times in 353 Posts
I was told that not only would they extend the number of cycles you could cycle the batteries but that it should extend your range because it's going to be gentler on the whole pack.

I tend to see my resting voltage bounce back up to 50v higher depending on the state of charge, 52.6v is "fully charged at rest" if I remember correctly and I can drive 4 miles to work over some hills and still read around 52v after I turn the key off, but my voltage under load drops to 44v or even 42v sometimes and as the batteries discharge I see it get down close to 40v if I've driven a lot that day and am climbing a steep hill.
  Reply With Quote
Old 04-18-2013, 06:38 PM   #10 (permalink)
Master EcoModder
 
Join Date: May 2012
Location: USA
Posts: 2,643
Thanks: 1,502
Thanked 279 Times in 229 Posts
Are these lead acid batteries? Have you tried the usual stuff like check the electrolytic level, add water as needed and maybe hook each battery itself on a charger over nite to "balance" it. Better yet, get a desulfur type of charger?

  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com