Battery recommendation for house/starter combo

[dzeppos]

Apologize in advance for another battery thread, but I think the question is simple:

My 2016 242LS came with two cranking interstate 24M-RD batteries with the standard VSC switch.

I have two 600 watt amps installed, I'm going to need more power, although I won't beach for more than 2 hours of music playing at a time per day.
Question:
1. Can I have a starting cranking battery, and a deep cycle house battery. (My stereo installer said they should be the same (cranking both or deep cycle- I think he's wrong)
2. Can I have a Group 24 cranking, and then use a Group 27 or 31 for deep cycle house battery? (Can I get two sizes, provided that they are the same type (both flooded or both AGM)
3. Should I just get two Dual purpose batteries?

Finally, maybe a high quality Group 24M deep cycle house battery is sufficient? (For 1-2 hours of music) -without having to go to a larger Group 27 or 31.

Any suggestions are greatly appreciated!
Thanks in advance

 

[rkim808]

Aloha @dzeppos i’m not the knowledgeable battery guy. But I have a AR240 with the stock batteries, and I have a 1000w and a 600w JL amps. I play music all day sometime sitting for 2-3hrs slamming the sounds. I’ve never had any issues with killing the house battery or not being able to start the engines(knock on wood). So I’m just saying that I think ur good as far as batteries is concerned, for ur use. Just my 2 cents.

 

[Dean P]

Apologize in advance for another battery thread, but I think the question is simple:

My 2016 242LS came with two cranking interstate 24M-RD batteries with the standard VSC switch.

I have two 600 watt amps installed, I'm going to need more power, although I won't beach for more than 2 hours of music playing at a time per day.
Question:
1. Can I have a starting cranking battery, and a deep cycle house battery. (My stereo installer said they should be the same (cranking both or deep cycle- I think he's wrong)
2. Can I have a Group 24 cranking, and then use a Group 27 or 31 for deep cycle house battery? (Can I get two sizes, provided that they are the same type (both flooded or both AGM)
3. Should I just get two Dual purpose batteries?

Finally, maybe a high quality Group 24M deep cycle house battery is sufficient? (For 1-2 hours of music) -without having to go to a larger Group 27 or 31.

Any suggestions are greatly appreciated!
Thanks in advance

I would get 2 AGM deep cycle batteries and you'll be fine. That's what I did. I also purchased an onboard battery charger to make sure they stay in their best state possible. Check signature for more info. Good luck.

 

[dzeppos]

Got it. On Board ProMariner 12 is on the way, and now looking for the Deep Cycle Batteries- I assume you have no problem starting your engines with them
thx

 

[Jack Long]

My boat came with the same set of batteries as yours.

I had to replace both of them at 230 hours this summer.

I kept them on a charger when not in use in storage all year round.

Like you I added more and better sound equipment and played the tunes sitting for 3-4 hours at a time as well as 3 trips to the Exumas.

They will last but I would change to a deep cycle battery when they do die.

On a side note, the day I knew it was time to replace, "the music died" we started singing LOL

Boat cranked up fine with no codes but house battery would not hold a charge after that.

 

[Dean P]

Got it. On Board ProMariner 12 is on the way, and now looking for the Deep Cycle Batteries- I assume you have no problem starting your engines with them
thx

Its been noted these engines (yours and mine) do not require a lot of cranking power. I purchased 2 Duracell AGM deep cycles for my Chaparral. No problems at all.
Assuming you don't mind drilling a big hole in your boat, you may consider the NOCO plug too. Place it up high and on the side that makes the most sense for you.

 

[ralphsmithiii]

Got it. On Board ProMariner 12 is on the way, and now looking for the Deep Cycle Batteries- I assume you have no problem starting your engines with them
thx

If you live by a SAM's club and have a membership or know someone who does, they sell a very popular Duracell Group 31 battery normally for $179/each which is a solid deal. But, if you're lucky, you can catch them on sale there for $159/each. I held out and ended up buying two myself which is plenty for a larger (I400watt) system

Oh and you're in luck, just looked and the batterys are on sale now: Duracell AGM Deep Cycle Marine and RV Battery - Group Size 31 - Sam's Club

 

[feziwig]

Our boats require very low amounts of power to start and a deep cycle will start them fine. In the waverunners, they just use a motorcycle battery.
I have 2 Duracell group 27 and an 800 JL amp. I’ve had the music going for 2-3 hours, and never needed to change to the other battery, they always start fine. I still like knowing it’s there and charge them both when not using the boat.

 

[dzeppos]

The feedback is super appreciated. I'm going the Duracell AGM route. My boat has 160 hours on it, but I haven't been good about keeping the original stock batteries on a tender, so I will buy new ones shortly (or at least wait until Spring - why let is sit out there)
My only last two questions are stay with Group 24, or go with a larger Group 27 or 31. Seems like for my use - a Group 24 Deep Cycle suffice.
However, if I went bigger, I assume putting i can use the screws holes for a new battery tray, or that its not a big deal screwing in new holes for a bigger battery tray.

 

[dzeppos]

Sorry for over-working this, but how hard is it to change over from stock group 24 battery trays to group 27/31 battery trays.
Will they simply screw in or will I need to drill down new holes to fasten the battery trays to the boat?

 

[ralphsmithiii]

Sorry for over-working this, but how hard is it to change over from stock group 24 battery trays to group 27/31 battery trays.
Will they simply screw in or will I need to drill down new holes to fasten the battery trays to the boat?

For my 2015 240, the battery trays where held in with 4 Phillips screws each. The bottom part of the battery compartment is hardwood so all I had to do was unscrew the trays, swap them for larger marine certified (I think that's what they are called) trays that fit the 27/31 and screw them back down. Super easy to do. I just reused the same screws and a drill and it was pretty quick and painless.

 

[dzeppos]

Perfect. I ordered my 2 Duracell 27 AGM dual purpose, along with new battery trays per the recommendation above. I thought about boxes but too bulky, and will Ensure to cover the terminals with caps/covers I also mounted my promariner sport 12 on a woodboard and velcroed the board right to the side wall carpet in the compartment.
Should be enough power for the 1400 watt stereo i just installed

Thanks to all for the excellent advice

 

[FLJetBoater]

Perfect. I ordered my 2 Duracell 27 AGM dual purpose, along with new battery trays per the recommendation above. I thought about boxes but too bulky, and will Ensure to cover the terminals with caps/covers I also mounted my promariner sport 12 on a woodboard and velcroed the board right to the side wall carpet in the compartment.
Should be enough power for the 1400 watt stereo i just installed

Thanks to all for the excellent advice

I'm about to do this type of install as well.

Is it accurate to assume that a 1000W amp (wetsounds syn-dx6, 6 revo6 and 2 revo8) has the potential to draw 83 amps?

Roughly calculating, for a battery that's rated for say 105AH which can only be drawn down to 50%, you're looking at 52AH. If you're running that amp at full volume it's not even going to last 1 hour. Am I missing something? 2 batteries would get you like an hour and a half. Any idea what the TRUE draw of an amp like this is at say, half volume or something reasonably loud but not deafening? I'm wondering whether to grab a 2nd house battery or just keep it as 1. I don't think the stator will provide much charge to these so on shore charging will be a necessity.

 

[FLJetBoater]

I actually found a nice explanation on Crutchfield.

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).

(in my case, =1000W)

Double it to account for amplifier inefficiency (600 watts X 2 = 1200 watts),

*2 = 2000W

then divide by the average output Voltage of an alternator, 13.8 volts (1200 divided by 13.8 = 87 amps).

I'll use 12V, since battery won't have a charge flowing to it.
2000 / 12 = 166A.

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 while playing music at top volume.

166 / 3 = 55A

So, 55A at top volume.

I think there is consensus that Class D are more efficient than 50%. Using 80% (I have seem some state they are closer to 90%) the calculations rework to 1000 / .8 = 1250 / 12 = 104 / 3 = 34A at full volume which is 3 hours on 2x105AH batteries.

 

[FLJetBoater]

Found another interesting article....to increase the sound level of a speaker 3db, requires a doubling in wattage.

The Revo6 6.5" are rated @ 90db/1w@1m. 90db loud @ 1watt @ 1meter away from the speaker.

Since it's pretty difficult to ever get more than 1 meter from a speaker on the boat, does that mean I could play these things with almost no power to them @ 1W and they would be 90db? It would seem, that playing these at a small volume while say docked, engine off, sitting on the boat, you'd be consuming < 1W of power per speaker? Many places say anything over 85db is considered "loud"

 

[212s]

@FLJetBoater Your math seems right and yes most people don't realize that 1w of power is all you need to hit the rating of the speaker. When listening at comfortable talking volumes, amps use far more energy powering the regulation and control circuits than powering the outputs which is why your amp will feel warm even when it's turned right down to zero. Typical volumes for background music is much less than 1w of output power. Human hearing follows a logarithmic amplitude scale (the decibel or dB) so to get double the apparent volume at your ears you need 10x the power. That's why a head unit with 5-10w of usable output per channel sounds so weak compared to a good 50-100w amp (other factors also apply, but this is the basic concept).

 

[FLJetBoater]

@FLJetBoater Your math seems right and yes most people don't realize that 1w of power is all you need to hit the rating of the speaker. When listening at comfortable talking volumes, amps use far more energy powering the regulation and control circuits than powering the outputs which is why your amp will feel warm even when it's turned right down to zero. Typical volumes for background music is much less than 1w of output power. Human hearing follows a logarithmic amplitude scale (the decibel or dB) so to get double the apparent volume at your ears you need 10x the power. That's why a head unit with 5-10w of usable output per channel sounds so weak compared to a good 50-100w amp (other factors also apply, but this is the basic concept).

Thanks. This really makes me feel better about the amount of battery life I'll get out of my stereo! I've conceded to the fact that the only way I'll know the true draw is to hook up an amp clamp and see what it is under 20%/50%/75% volume...