Is this fine as a backup battery for music

[R055]

Hey guys, my sound system consists of 3 amplified tower speakers and 2 regular inside the boat. I want to get a second battery just for the piece of mind although I basically don't need it more than to play an hour of music with engine off. My problem is I can't fit the big batteries easily in my battery area but this battery would fit perfectly. Would it be fine for like an hour of listening to music at low-medium volume?

Mod EDIT R55 referenced a lawn mower battery

 

[wrench 3]

I doubt that it would run things for very long. But what size are your amps?

 

[ezmobee]

You're going to need a full sized deep cycle battery for that system and likely an external charging method to top it back up as well.

 

[R055]

My amp is 400 watts rms although I'm never going to have it over 40% volume when the boats not on. I'm running 2 speakers on two channels and 1 speaker bridged on the other 2 channels. I'm only looking for about an hour of use at 20-40% volume.

 

[rallyart]

You want a deep cycle battery. Using a conventional battery for that purpose will kill the battery fairly quickly. Not just discharging quickly, actually killing it. A starting battery can deliver the poser but it is not made to stay discharged for any length of time. Look up a sealed agm or gel cell and you can lay in on its side or transport it without risk.

 

[airshot]

Might want to consider one of the new lithium ion (lipo) batteries on the market, small in size hugh on power! Half the size of a typical deep cycle with almost 50% more power and longer run life before recharge. That said they are not cheap and do need a special charger but would definetly do the job in a small size...their big draw back is they don't do well in cold....but hey you have a boat....sure you don't do much boating in cold weather.

 

[Silvertip]

Have you ever seen a LiPo fire? Mistreat one of those (drop it, puncture it, short it, use the wrong charger, or charge it improperly) and I hope you are close to shore!

 

[R055]

Hmm definitely not a big fan of fires on my boat. The thing is I'm only going to need the second battery like 2 times per year which is when I go camping to Eastern Washington and have my boat docked. Like to go and sit on the boat at night with music playing. Since this only happens about 2 times a year, didnt really want to invest in an expensive battery or big battery that requires modification to my battery compartment. I'm fine with a battery half the size of a regular battery as long as it will last me an hour at 40% music I'll be happy.

 

[R055]

Found what I'm looking for. Getting a group U1 agm battery. Only 5 inches wide and deep cycle. Shows it can last 20 hours at 35amp discharge rate. So should last me atleast 1 hour?

 

[airshot]

Have you ever seen a LiPo fire? Mistreat one of those (drop it, puncture it, short it, use the wrong charger, or charge it improperly) and I hope you are close to shore!

Yep, very familiar with lipo batteries, been using them for years. it is one battery that is not forgiving....no one else in the household is allowed to have anything to do with them except me. You can drop them, and they can be punctured and it will not explode but it does kill the battery. Fires are caused by wrong charger or shorting them out. Numerous companies make lipo storage boxes that are safe, to help eliminate problems from being careless. I have used lipos for about 8-9 years without any issues at all but care is needed.

 

[H20Rat]

Found what I'm looking for. Getting a group U1 agm battery. Only 5 inches wide and deep cycle. Shows it can last 20 hours at 35amp discharge rate. So should last me atleast 1 hour?

I buy a bunch of those batteries for computer equipment UPS use. They are not 20 hours at 35 amp. They are rated at 35 amp/hour, so they will last 35 hours with a 1 amp draw under perfect conditions. (and that only works with a very low 1 amp draw, that doesn't mean they can also run 35 amps for an hour) A battery that could do 35 amps at 20 hours would be at least a 700 amp/hour battery. The largest 12v consumer battery trojan makes is a 254 amp/hour beast that also weighs around 160 pounds.

A typical stereo will probably average out to around 10-20 amps under low/moderate volume, so your runtime is going to be about an hour give or take. So it should make your goal of an hour, just barely. It is abusive to the battery to go that low, even for a deep cycle, so the battery life is going to be pretty bad.


If it were me, I'd find a location to do a proper dual battery setup in your boat. Lots of advantages beyond just having more stereo run time. You gain redundancy on a very critical system!

 

[H20Rat]

Yep, very familiar with lipo batteries, been using them for years. it is one battery that is not forgiving....no one else in the household is allowed to have anything to do with them except me. You can drop them, and they can be punctured and it will not explode but it does kill the battery.

I've tried this same test with the same results. I'm not puncturing another one to test ever again! Technically yeah it doesn't explode, it just generates a very intense fire that can't be put out and gives off some very noxious fumes.

https://www.youtube.com/watch?v=wUFxlf4fXjo

 

[R055]

I buy a bunch of those batteries for computer equipment UPS use. They are not 20 hours at 35 amp. They are rated at 35 amp/hour, so they will last 35 hours with a 1 amp draw under perfect conditions. (and that only works with a very low 1 amp draw, that doesn't mean they can also run 35 amps for an hour) A battery that could do 35 amps at 20 hours would be at least a 700 amp/hour battery. The largest 12v consumer battery trojan makes is a 254 amp/hour beast that also weighs around 160 pounds.

A typical stereo will probably average out to around 10-20 amps under low/moderate volume, so your runtime is going to be about an hour give or take. So it should make your goal of an hour, just barely. It is abusive to the battery to go that low, even for a deep cycle, so the battery life is going to be pretty bad.


If it were me, I'd find a location to do a proper dual battery setup in your boat. Lots of advantages beyond just having more stereo run time. You gain redundancy on a very critical system!

Not that easy to do in a 19 foot bowrider that already has a dedicated compartment for the battery with wires and everything already running to it. If it gives me an hour im happy. Is it okay to charge the deep cycle amg batteries with the alternator or is the charge too much or I should charge it with a charger?

 

[rallyart]

A deep cycle battery will charge just fine off tn engine alternator. You could also consider a solar charger, but they have very low output.

 

[airshot]

I've tried this same test with the same results. I'm not puncturing another one to test ever again! Technically yeah it doesn't explode, it just generates a very intense fire that can't be put out and gives off some very noxious fumes.

https://www.youtube.com/watch?v=wUFxlf4fXjo

If you read the instruction on disposing of lipo batteries the mfgr recommends slowly puncturing a couple holes in them then drop them in salt water. I have punctured more than I can remember with no fire and no explosion....but you don't smack them with a hammer!! Most lipo fires are caused by improper charging!!