Big stereo build - charging method

[Brandonloos21]

Planning on building my stereo this spring, going to consist of ~1500 watts to interior speakers, ~2200 watts to towers, ~6000 watts to subs. Batteries are going to be 6 or 8 6v 225ah deep cycles. 
 

The issue I’m having is figuring out how to charge. I will have an onboard charger and charge when at the house or a dock with power, I see a lot of people separate the stereo and only use onboard charger, though I still want the ability to charge off of alternator. 
 

Im going to upgrade to the larger 170a alternator (is there any bigger alternator that can fit on m6di). Any ideas for being able to charge the stereo bank off of alternator? Is there a way that I can have one way charging, but the amplifiers only drawing from the stereo batteries? (If I wire the amplifiers directly to battery, will this work where it charges the batteries but stereo does not pull from my starting battery).

Edited November 23, 2022 by Brandonloos21

[MLA]

Id use the systems estimated DC amperage draw, rather then the amp's advertised wattage AC output. THis may give you a better picture of what your DC supply system needs to be like. 

Its completely feasible to have the audio system draw from a house bank only, while the alternator supplies a charge to both while the engine is running. I beleive Malibu calls it Battery Option 2? 

[Ken10]

Look up stinger battery isolator it’s automatic inline never a misshap with manually switching perko I’m sure there is other comparable products this has been good for me 

[Brandonloos21]

1 hour ago, MLA said:

Id use the systems estimated DC amperage draw, rather then the amp's advertised wattage AC output. THis may give you a better picture of what your DC supply system needs to be like. 

Its completely feasible to have the audio system draw from a house bank only, while the alternator supplies a charge to both while the engine is running. I beleive Malibu calls it Battery Option 2? 

That’s what I was hoping. I guess my question is, if I have the boat running, switch is in 1+2 so both battery banks will be getting charged, and only have the amps hooked up to house bank, will it draw from the cranking bank as well since the 1+2 switch is “connecting everything”?

[IXFE]

3 hours ago, Brandonloos21 said:

Planning on building my stereo this spring, going to consist of ~1500 watts to interior speakers, ~2200 watts to towers, ~6000 watts to subs. Batteries are going to be 6 or 8 6v 225ah deep cycles. 
 

The issue I’m having is figuring out how to charge. I will have an onboard charger and charge when at the house or a dock with power, I see a lot of people separate the stereo and only use onboard charger, though I still want the ability to charge off of alternator. 
 

Im going to upgrade to the larger 170a alternator (is there any bigger alternator that can fit on m6di). Any ideas for being able to charge the stereo bank off of alternator? Is there a way that I can have one way charging, but the amplifiers only drawing from the stereo batteries? (If I wire the amplifiers directly to battery, will this work where it charges the batteries but stereo does not pull from my starting battery).

I’m 2023, the alternator upgrade is a 250a. So I’d assume that upgrade is pretty straightforward on your boat. 

[MLA]

10 hours ago, Brandonloos21 said:

That’s what I was hoping. I guess my question is, if I have the boat running, switch is in 1+2 so both battery banks will be getting charged, and only have the amps hooked up to house bank, will it draw from the cranking bank as well since the 1+2 switch is “connecting everything”?

With a OFF/1/1+2/2 style switch in the 1+2 position, both banks are combined. So, the stereo will draw from both bank. Now, this is not really an issue with the engine runnning, in terms of running the main battery down. However, with the engine off and the switch still in the 1+2 position, you do run the risk of running the main cranking bank down. 

With the updrade Malibu battery switch/ACR mentioned earlier, you can keep the house and main banks isloated all the time, have the house/stereo loads only draw from the house bank (your group of 6V's) and have the alternator supply both bank while engine running. 

[Brandonloos21]

9 hours ago, IXFE said:

I’m 2023, the alternator upgrade is a 250a. So I’d assume that upgrade is pretty straightforward on your boat. 

Oh sweet, I had no idea. Emailing my service dept right now  

[Brandonloos21]

1 hour ago, MLA said:

With a OFF/1/1+2/2 style switch in the 1+2 position, both banks are combined. So, the stereo will draw from both bank. Now, this is not really an issue with the engine runnning, in terms of running the main battery down. However, with the engine off and the switch still in the 1+2 position, you do run the risk of running the main cranking bank down. 

With the updrade Malibu battery switch/ACR mentioned earlier, you can keep the house and main banks isloated all the time, have the house/stereo loads only draw from the house bank (your group of 6V's) and have the alternator supply both bank while engine running. 

So I checked my build sheet, I was pretty certain I ordered option 2 (which I did). It is only the regular 1, 1+2, 2, both switch. Do you have a PN for the ACR?

[MLA]

Maybe Malibu call it option 3. 

[Brandonloos21]

On 11/23/2022 at 11:30 AM, MLA said:

Maybe Malibu call it option 3. 

Would you be weary of adding an acr if your alternator puts out more than the rating? 170a alternator with 120a continuous 210a 5min rating?

[shawndoggy]

52 minutes ago, Brandonloos21 said:

Would you be weary of adding an acr if your alternator puts out more than the rating? 170a alternator with 120a continuous 210a 5min rating?

https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

[MLA]

3 hours ago, Brandonloos21 said:

Would you be weary of adding an acr if your alternator puts out more than the rating? 170a alternator with 120a continuous 210a 5min rating?

if that was your FB post about using 6 or 8 6V for a stereo bank, you wiould be better served with a traditional OFF/1/1+2/2. A large deeply depleted bank will cause ACR to not act right untill the voltage recovers some. With a large bank, this would take awhile. I would also not want to introduce that large of a load to the alternator after a long day in the part cove. The manual switch will allow for this isolation once back underway.  

[Steve B.]

59 minutes ago, MLA said:

The manual switch will allow for this isolation once back underway.  

While the engine is running? I guess I've read several times it's okay, but have never done it. I think they are make before break switches, but I think I'd worry about a spark, especially if there is a big load on the alternator.

Steve B. 

[shawndoggy]

14 minutes ago, Steve B. said:

While the engine is running? I guess I've read several times it's okay, but have never done it. I think they are make before break switches, but I think I'd worry about a spark, especially if there is a big load on the alternator.

Steve B. 

No I think he's saying take the automated feature of the relay out of the picture and stay off a heavily depleted stereo bank altogether till a shore charger has a chance to do some charging and reconditioning back at the dock.

You could accomplish the same thing with the ACR by putting a switch on the ACR's ground wire so that you could manually disable the ACR and prevent it from combining.

Edited December 1, 2022 by shawndoggy

[Brandonloos21]

1 hour ago, MLA said:

if that was your FB post about using 6 or 8 6V for a stereo bank, you wiould be better served with a traditional OFF/1/1+2/2. A large deeply depleted bank will cause ACR to not act right untill the voltage recovers some. With a large bank, this would take awhile. I would also not want to introduce that large of a load to the alternator after a long day in the part cove. The manual switch will allow for this isolation once back underway.  

Yeah that was me! It was always my understanding that an alternator would provide charge to a bank and not necessarily know the size. What would be the reasoning that a large bank would strain an alternator rather than a small bank? I thought that it would just end up taking longer to charge a big bank but would charge at same rate. 

[Tsumi]

4 hours ago, Brandonloos21 said:

Yeah that was me! It was always my understanding that an alternator would provide charge to a bank and not necessarily know the size. What would be the reasoning that a large bank would strain an alternator rather than a small bank? I thought that it would just end up taking longer to charge a big bank but would charge at same rate. 

It's the same reason you don't want to use an alternator to charge a lithium battery: you risk burning out the alternator. The typical alternator is not designed to run at its full rate for extended periods of time, which it would be with a depleted battery bank.

If you want to be able to charge while underway without risking alternator damage, I would suggest looking into a DC-DC charger. Alternatively (pun not intended), you can get a Wakespeed alternator regulator or something similar that has alternator temperature sensing to limit output when it gets hot.

[MLA]

13 hours ago, Steve B. said:

While the engine is running? I guess I've read several times it's okay, but have never done it. I think they are make before break switches, but I think I'd worry about a spark, especially if there is a big load on the alternator.

Steve B. 

with out getting too deep into the weeds on when and when not to move a switch's position. Im simply referincing that, with the manual 1/1+2/2 switch, you can anchor on the house bank and run on the main cranking bank, and the alternator will never "see" that depleted house bank. With an auto-combining relay, once the engine is running, the ACR will attempt to close, combining the low house bank to the charge system. 

13 hours ago, Brandonloos21 said:

Yeah that was me! It was always my understanding that an alternator would provide charge to a bank and not necessarily know the size. What would be the reasoning that a large bank would strain an alternator rather than a small bank? I thought that it would just end up taking longer to charge a big bank but would charge at same rate. 

Alternators are load sensitive. It can tell the difference between between a glove box light and a window lift motor, and its output will be accordingly. A 65 Ah group-24 at 11V is a smaller load then 3-4 250 Ah 12V (6 or 8 6v) at 11v. 

 

With lithium, you need a dc to dc to buffer the alternator ouptut, more to protect and properly supply the lithium, more then protect the alternator. Now, if you are using the dc-dc to buffer the load of a large depleted 12V WCLA or AGM, i dont think its worht it. The time to recharge under this scenario would be way to long. Id rather just let the bank be, and plug up my shore charger later. 

[Tsumi]

1 hour ago, MLA said:

with out getting too deep into the weeds on when and when not to move a switch's position. Im simply referincing that, with the manual 1/1+2/2 switch, you can anchor on the house bank and run on the main cranking bank, and the alternator will never "see" that depleted house bank. With an auto-combining relay, once the engine is running, the ACR will attempt to close, combining the low house bank to the charge system. 

Alternators are load sensitive. It can tell the difference between between a glove box light and a window lift motor, and its output will be accordingly. A 65 Ah group-24 at 11V is a smaller load then 3-4 250 Ah 12V (6 or 8 6v) at 11v. 

 

With lithium, you need a dc to dc to buffer the alternator ouptut, more to protect and properly supply the lithium, more then protect the alternator. Now, if you are using the dc-dc to buffer the load of a large depleted 12V WCLA or AGM, i dont think its worht it. The time to recharge under this scenario would be way to long. Id rather just let the bank be, and plug up my shore charger later. 

True, a regular alternator won't have the right charging profile for lithium either, but for most 12v LFP batteries they can tolerate the standard alternator voltage output.

You are right that a DC-DC charger will be slow. Good high output ones are very expensive. The best option for charging under way will most likely be the Wakespeed regulator as you can charge with full alternator output but limit output when it gets too hot. It also gives the possibility of using lithium batteries as it can alter the charge profile. That said, with the Wakespeed you'll still want an ACR if using lead-acid. ACRs don't work right with lithium.

[Brandonloos21]

1 hour ago, Tsumi said:

True, a regular alternator won't have the right charging profile for lithium either, but for most 12v LFP batteries they can tolerate the standard alternator voltage output.

You are right that a DC-DC charger will be slow. Good high output ones are very expensive. The best option for charging under way will most likely be the Wakespeed regulator as you can charge with full alternator output but limit output when it gets too hot. It also gives the possibility of using lithium batteries as it can alter the charge profile. That said, with the Wakespeed you'll still want an ACR if using lead-acid. ACRs don't work right with lithium.

I have been looking into some DC-DC Chargers, so what they do pretty much is take the charge from one (not strained) battery and use it to charge a strained bank?

[Tsumi]

15 minutes ago, Brandonloos21 said:

I have been looking into some DC-DC Chargers, so what they do pretty much is take the charge from one (not strained) battery and use it to charge a strained bank?

They just take the charge from one bank and put it in the other bank regardless of what charge level either bank is at. You'll want to wire the charger to a switch or the ignition so it isn't pulling power when it's not supposed to.

[MLA]

On paper, a higher output DC-DC sounds good for a larger hank. However, that that DC-DC isnt pulling the juice out of whole cloth. its coming from the very alternator you are trying to limit the load it sees.  

[Brandonloos21]

17 minutes ago, MLA said:

On paper, a higher output DC-DC sounds good for a larger hank. However, that that DC-DC isnt pulling the juice out of whole cloth. its coming from the very alternator you are trying to limit the load it sees.  

It seems as if it does limit the charge being pulled such that it doesn’t strain the alt, correct?

[MLA]

14 minutes ago, Brandonloos21 said:

It seems as if it does limit the charge being pulled such that it doesn’t strain the alt, correct?

Well, maybe. A higher DC-DC output is going to have a higher inout demand then the lower output DC-DC unit. They dont create the output, its coming from the exitsing supply. So if the goal is to limit demand on the alternator, then a high-output DC-DC may not be the answer, It hAS to draw more, to put out more. No way around it. 

[Steve B.]

Few notches beyond my understanding but I do know the goal, ha. I wonder if there's way to scavenge energy back to the battery's somehow via the prop or shaft or something to be as energy efficient as it could be.

Steve B.

Edited December 2, 2022 by Steve B.
spell check

[Brandonloos21]

1 hour ago, Steve B. said:

Few notches beyond my understanding but I do know the goal, ha. I wonder if there's way to scavenge energy back to the battery's somehow via the prop or shaft or something to be as energy efficient as it could be.

Steve B.

Sooner or later these electric boats will have regenerative braking or resistance like the EV’s on the road! Lol