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-   -   Amp hours calculation (http://www.wakeworld.com/forum/showthread.php?t=777943)

Matt 03-26-2010 4:13 PM

Amp hours calculation
 
Hopefully someone can help me...
How would I calculate my amperage draw? or amp hrs

I have 5 jl MHD 750/1 pushing 4 jl 10w7 subs & a pair of Wet sounds Pro 485 towers
also 2 jl MHD 600/4 pushing 4 pair of ws-650 coaxles
Alpine deck, WS-420, & HSE

I have 15 led speaker rings & 8+ random led clusters on the boat
Plan on having 3x Shadowcaster s2 underwater lights

I would like to be able to play the radio for 2-3 hrs without killing the battery
How many Optimum yellow top 31 battery should I use Just for the music & leds?
I have 2 seperate batteries for starter & boat with a perco switch
Also I have a 135a Alternator being built

hatepain 03-26-2010 5:10 PM

Get Lifelines they kill Yellow/Blue tops. With all you have check out the GPL-8DA. I have a couple of them in my boat and can run in the neighborhood of 10hours if I needed too. Each battery is 255 amp hours and have a 475 minute discharge at 25 amp rate which you will be well above. They're big though and weigh about 170lbs each.

Matt 03-26-2010 5:19 PM

Where did you stick them? arent they pretty big? You have any pics

hatepain 03-26-2010 5:21 PM

By the way sick ass system man it should be insanely loud. You'll have to post up some pics asap.

hatepain 03-26-2010 5:23 PM

V locker, they are about 25" long by 12" wide by 10" high. They take up some space for sure but so would 10 blue tops which is what they are equivelant too. No pics and I am no where near my boat

polarbill 03-26-2010 5:26 PM

Quote:

Originally Posted by Matt (Post 1566390)
Where did you stick them? arent they pretty big? You have any pics

The batteries Hate is talking about are generally used in commercial vehicles and large yachts. They are huge and weigh around 150 lbs each. Keep that in mind. If you have the room and a crew of people to help you get them in and out they are a great way to have an amazing reserve capacity and add ballast.

If you can't find Lifeline's around your area Deka Seamate's are good AGM batteries and are usually cheaper than Lifeline's.

Matt 03-26-2010 5:31 PM

I have 6 D27F yellow tops, I had a great location picked out and then decided to go with another 10w7 now I can only fit 4 baterys in there... Just trying to figure out if i can get away with 3 batteries with the JL amps they are suspose to use less than 1/2 of the power of say a kicker amp... I may have too try out your lifelines gonna have to do some measuring... Boy thats hard on the wallet $650 each,,,,

I will have a thread on my system as soon as I get a little further into it...
Thanks

polarbill 03-26-2010 5:45 PM

Quote:

Originally Posted by Matt (Post 1566400)
I have 6 D27F yellow tops, I had a great location picked out and then decided to go with another 10w7 now I can only fit 4 baterys in there... Just trying to figure out if i can get away with 3 batteries with the JL amps they are suspose to use less than 1/2 of the power of say a kicker amp... I may have too try out your lifelines gonna have to do some measuring... Boy thats hard on the wallet $650 each,,,,

I will have a thread on my system as soon as I get a little further into it...
Thanks

Damn, that is expensive for those batteries. The similar Deka should be close to or under $500 at least. Matt, I didn't even think yellow tops were Optima's "so called" deep cycle battery. Here is a link to Deka's brochure for marine AGM batteries. It lists sizes and specs. You want to look at the the 20 AH column and the sizes. Notice that a group 24, which is the same footprint as the optima d34 just an inch taller has a 20 AH rating 24 units higher than the optima blue tops.

http://www.eastpenn-deka.com/assets/base/0245.pdf

Matt 03-26-2010 6:00 PM

Now ya tell me... I got a great deal on these batteries they were in a truck built for Sony for SEMA and never used for more than an hr or 2... I paid in the $500 range for the set of 6 deepcycle/starting batteries.. they have a 66 20ah rating each so I figured they would be good until Now. I never imagined there were 250+ 20AH batteries avaliable, thats nuts...

hatepain 03-26-2010 6:16 PM

Brett know his shizz more than or as well as anyone on here about batteries, I was hoping he'd chime in. I'm willing to bet you can get an 8D in the same location you can fit 4 of your blue tops and in all actuality be about the same for amp hours and with less weight. A lot of guys have been digging the Deka's on here too and like Brett said you don't pay for the Lifeline name. I just happen to get a steal on mine when an English Lord decided to redo all the batteries on his yacht when the ones he was replacing were built in 09!!! A couple core charges later I had perfectly good 8D's :D

Matt 03-26-2010 6:38 PM

Awesome, Thanks

Now i'm up to speed on the batteries, Can anyone tell me how much current draw these MHD amps will pull with the music cranking?

Matt 03-27-2010 10:17 AM

I got this off of the Cruchfield Website... Does anyone know if it will be accurate or even close with the JL MHD Amps?

To calculate the current draw of an amplifier, multiply the number of channels by the RMS watts per channel (a 2 channel amp rated at 300 watts RMS per channel would be 600 watts). Double it to account for amplifier inefficiency (600 watts X 2 = 1200 watts), then divide by the average output Voltage of an alternator, 13.8 volts (1200 divided by 13.8 = 87 amps). Since the average music signal requires about 1/3rd of the average power in a test tone, divide by 3 (87 amps divided by 3 = 29 amps). The result is the amplifier's approximate average current draw.

A quick way to ballpark an amplifier's current draw is to divide the total fuse value of the amp by two. For amplifiers with multiple fuses, the rating of all fuses provided with the amp must be added together. This will likely produce a significantly higher estimate than using the proper formula. Although inaccurate, this will err on the side of safety.

Finally, compare the amplifier's approximate current draw to your vehicle's reserve current capacity to determine if the electrical system can support the amplifier.

_vitty_ 03-27-2010 12:03 PM

Check out XS power batteries as well. I am going to be running 3 of the d2700's in my boat this summer. HUGE power on them. According to the Deka link that was posted these batteries outperform them in similar sizes.
www.4xspower.com

joe_crawley 03-27-2010 12:26 PM

750/1s will draw about 20A each- 100A total, 600/4 will draw about 15A- 30A total, decks and EQs wil draw about 5A total, the 23 LED lights should draw about 10A total, and the 3 Shadowcasters will draw about 10A total. So thats about 155A, so to play for 3 hours you'll need a 465AH battery.

This is assuming you are bumping the system and it is isolated from any other electric running in your boat.

You'd need at least 6 of the 75 Amp Hour Optimas to pull this off

Matt 03-27-2010 1:03 PM

Quote:

Originally Posted by joe_crawley (Post 1566570)
750/1s will draw about 20A each- 100A total, 600/4 will draw about 15A- 30A total, decks and EQs wil draw about 5A total, the 23 LED lights should draw about 10A total, and the 3 Shadowcasters will draw about 10A total. So thats about 155A, so to play for 3 hours you'll need a 465AH battery.

This is assuming you are bumping the system and it is isolated from any other electric running in your boat.

You'd need at least 6 of the 75 Amp Hour Optimas to pull this off

Thanks man, Ill have to lose some equipment or find somewhere for more batteries... Thats ok we didnt have room for 16 life vests anyway...

Is the AH the same as the rating on the battery 66 @20ah or what does that mean?

joe_crawley 03-27-2010 3:19 PM

Usually the rating on a battery reads: (x)Ah @ (y)A where x is the capacity of the battery assuming discharge at a rate of y (regardless of time). In short- A battery rated at 100Ah @ 10A could put out 10A for 10 Hr, or 1A for 100Hr, but wouldn't necessarily guarantee 50A for 2 Hr because it is only rated for 10A discharge.

So I guess more specifically, you need a battery rated at 465Ah @ 155A, which is a tall order. The good news is if you are listening to the music at a comfortable level, you might be drawing 75%-80% less current than I estimated (30A instead of 130A) and in that case you could get away with a pair of batteries for a couple of hours.

Also, I'm sure you know, but if you've got 4 subs getting instantaneous 750 Watts (or half that) each you don't want to be ANYWHERE near them if you care about your long term (or short term) hearing. Sounds like a sick system though post up pics when it's done!

mikeski 03-27-2010 3:35 PM

I have a spreadsheet that does a pretty good job. Send me your email and I will mail it to you.

mikeskiw@gmail.com

Matt 03-27-2010 9:44 PM

5 Attachment(s)
Here are a few shots of what it looks like tonight... Very poor quality Iphone pic I know...
Looks like itll be about 2 more weeks on the build then i'll start a thread start to finish... O and before you ask the polished aluminum box is going to be the enclosed amp rack for all the mhd amps


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