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Silver Member Username: CheapskatePost Number: 567 Registered: Mar-04 | i'm looking to upgrade my street party bicycle for more power. right now i'm using a 10wpc sonic impact amp and am getting drowned out 1/4 block outside every nightclub. i just found some smaller panasonic 12v batteries that would be doable on a bicycle where car batteries are too large. all i'm looking for is something like 3-4 hours run at a time with something like a 100wpc amp set to bass boost pushing a pair of lightweight pyle outdoor speakers (93dB X 8 ohms) could a smaller battery do the job? what about running two 12v X 7aHs in series? would that equal 14aHs? i know voltages get added in series but not parallel and that's the extent of my battery knowledge. thanks in advance to anyone who can help me take my mountain bike to the next level (short of a full on custom trailer) |
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Silver Member Username: CheapskatePost Number: 568 Registered: Mar-04 | hello... does no-one here know their battery math? i know almost nothing about car stereo as i don't have a car. as technically knowledgable as some are in the home audio forums, i thought there would be at least one person here with the info on how much battery i need to hook my bike up. |
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Gold Member Username: Killerzracing71Fredericksburg, Virginia United states Post Number: 1992 Registered: Aug-05 | Lol I wanna c that look like the Installers Instittue Bicycle LOL |
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Silver Member Username: CheapskatePost Number: 569 Registered: Mar-04 | it will look something like this, only a bit less "off the shelf". http://takatomon2000.googlepages.com/my_street_party_bike NEXT year i'll do a "show level installation" when i build a trailer for my lowryder and get a custom pain job for it. all these alleged "car stereo experts" and not one person can tell me minimum battery requirements |
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Silver Member Username: Kpa2727Old Bridge,, NJ USA ! Post Number: 985 Registered: May-07 | ah for hells sake ok heres the best way to do it. for a 250 rms 4 ch amp i used to run a sub and 2 speakers off of back in my school days, it got so loud you needed ear muffs. what uneed to do is wire 2 batts pos to neg then to the amp but 24 volt is a bit much i think. i used to 7000 mah 7.2volt rc car batteries and wired them to 14 volts it would run for a few hours maybe 4 or 5 depending on the volume. depending on the size amp u might get away with it cause the battery would be a constant drain, 12 volts would be enough but mah matters cause if it's low it won't last. |
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Silver Member Username: Kpa2727Old Bridge,, NJ USA ! Post Number: 986 Registered: May-07 | btw 10 watts is very low so bettery power needed would be low. depend how much voltage your amp accepts, to much u'll toast it. |
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Silver Member Username: CheapskatePost Number: 570 Registered: Mar-04 | no, i'm looking to go UP in power from 10w. my sonic impact takes 8 AAA bateries. right now, the amp i FINALLY found that i want is a class D blaupunkt rated at 75wpc @ 4 ohms, so it'll be more than twice as efficient as a 100w class A/B like i was considering. originally, i tried to find 50wpc class D modules to no avail. for kits, your only choices are 15w and under or 150w and over, but the blaupunkt is right in that mid powered zone AND i've since learned about compact motorcycle batteries. the only problem is i just can't get anyone to tell me how much juice i need to run the blaupunkt for 4 hours at full. BTW, i'll be driving 8 ohm speakers, so it'll be even easier on the amp. i just need to know if a motorcycle battery can cut it. |
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Gold Member Username: N2audioLawrence, Ks USA Post Number: 1490 Registered: Mar-04 | Well at 8 ohms let's assume 40w/ch - 2 channels, right? So 80w. Assume an efficiency of 75% which should be in the ballpark... 80/.75= 107w 107w/12v = 8.9A That would be full volume for test tones. Music rms power should be no more than 1/3 as much so call it 3A. Seems to me you'd need at least 9-12 Ah to power that amp at 8 ohms stereo loud for 3-4 hrs. Probably more if you account for voltage loss over time. However, if you're planning to use the gain to limit power you might get away with less. Batts in series sum voltage - current stays the same. Batts in parallel sum current, voltage stays the same. |
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Silver Member Username: CheapskatePost Number: 571 Registered: Mar-04 | OK... i remember the series/parallel rule from industrial arts. i'm just totally out of it when it comes to amplifier current draw etc. crutchfield told me that i needed 20 amps to run this amplifier http://www.crutchfield.com/App/Product/Item/Main.aspx?g=120&i=023THA275P&search= Blaupunkt+VENDORID023&searchdisplay=Blaupunkt&tp=115 but looking at the specs, 20 amps is the fuse rating which would seem to me to be more than the amp can actually use. looking at motorcycle batteries, the difference between 18Ahs & 20Ahs is nearly a doubling in price! they must be so expensive because of low volume sales. so taking what you're telling me and what i'm deducing from the blaupunkt's fuse rating, a 15 - 18 amp battery should be sufficient then, right? one question about current, you mean WATTS right, not amps? when you put amps in series, amperage is added too isn't it? that's the only way i could imaging JVC getting 50+ watts out of it's 10 or 12 D cells in the kaboom box. in reading something i came across regarding NiMH battery packs, it claimed that NiMHs are both lighter than lead acid for a given power rating as well as having an 80% longer run time. using my imperfect understanding of battery math, 10 X 1.5v @ 2500mAh D cells in series = 15 volts & 25 amps, right? if so, i could more easily fit battery packs in my frame and use the space more efficiently as well as save weight. correct? thank you for the help you've already given me optidriven. |
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Gold Member Username: N2audioLawrence, Ks USA Post Number: 1497 Registered: Mar-04 | Crutchfield told me that i needed 20 amps to run this amplifier http://www.crutchfield.com/App/Product/Item/Main.aspx?g=120&i=023THA275P&search= but looking at the specs, 20 amps is the fuse rating which would seem to me to be more than the amp can actually use." At optimal output (190w) and my appx of 75% efficiency 20A is almost dead on. "so taking what you're telling me and what i'm deducing from the blaupunkt's fuse rating, a 15 - 18 amp battery should be sufficient then, right?" Yes, making some reasonable assumptions I think that would get it done. "one question about current, you mean WATTS right, not amps?" Umm, I don't think so. Power = watts, current = amps. "when you put amps in series, amperage is added too isn't it?" No, current stays the same, only voltage sums. "that's the only way i could imaging JVC getting 50+ watts out of it's 10 or 12 D cells in the kaboom box." There's probably a circuit that steps up voltage. Just like in a 12v amplifier. "using my imperfect understanding of battery math, 10 X 1.5v @ 2500mAh D cells in series = 15 volts & 25 amps, right?" 15v, 2.5A |
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Silver Member Username: CheapskatePost Number: 573 Registered: Mar-04 | i had to look up amps & watts to see the difference between the two. both measure flow, but amps = closed circuit and watts = used power thanks a bunch for your help optidriven. now i know what i need to know to car amp a bike. for anyone else needing big power on a small budget, just use 12v 20a electric scooter as search engine keywords. until i started searching by volts & amps, i was only looking at motorcycle etc. batteries whiich start at $80 and go up from there while comparable electric scooter batteries sell for half that at $40 and up, possibly even less as i only checked a couple sites. i'll post my new system when i have it built for this summer. thanks again. |
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Silver Member Username: Kpa2727Old Bridge,, NJ USA ! Post Number: 992 Registered: May-07 | btw don't forget u have to solder over the rem or put a powe source to it to turn the amp on. i soldered mine at the time. |
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Silver Member Username: CheapskatePost Number: 574 Registered: Mar-04 | huh? you're saying just wiring the amp won't let me use it? i would have thought that amps just work when they're fed current. i'll definately have to look into amp installation as it seems like i'll need to use specialized connectors too. i would have though that amps just use RCA ins, positive & negative screw terminals for power and either screw terminals or 5 way binding posts for power outs, but the only thing i recognize on the blaupunkt are the RCA ins. i'm sure it has to come with installation instructions. |
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Gold Member Username: N2audioLawrence, Ks USA Post Number: 1513 Registered: Mar-04 | they need a trigger of some kind to turn on/off. They're wired directly to the battery, even when they recieve no signal they draw "idle" current - which can be an amp or more. Without the on/off trigger a car battery can be drained overnight. A 15Ah battery - probably in a couple hours. you can just loop a wire from the B+ terminal at the amp to the remote terminal, and you could put a real simple switch on it to make turning it on and off quick and easy. Trigger current is very low, 10-40mA. |
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Silver Member Username: CheapskatePost Number: 575 Registered: Mar-04 | OK there's something else i didn't know about car audio. is the process something that i have to do once, or every time that i want to use the amp? the setup i was planning on would only have the amp powered up when i'm using it. i was going to make an amp mount that sits on top of the battery mount and only when the system is installed would the amp had been powered. thanks again for all of your help. |