Charging House Bank While Underway

[Shrew]

I completed some upgrades to the 12V system at the end this last season.

1 x 4d Starting Battery (Lifeline AGM)

2 x 8D (parallel) Houses Bank (Lifeline AGM).

Each battery bank has a dedicated BlueSeas remote battery shutoff.

There is a Blue Seas ACR tying the two banks together.

The entire boat is connected to the house bank.

Engine is connected to the starting bank.

I kept the stock 80amp alternator

===================

I'm now considering whether this might be too much for the alternator.

Should I be adding a second 100amp alternator for the house bank??

 

[utclmjmper]

If the alternator is belt driven,, why not replace it with a 160 amp unit.??.>>>Dan

 

[catalinajack]

I completed some upgrades to the 12V system at the end this last season.



1 x 4d Starting Battery (Lifeline AGM)



2 x 8D (parallel) Houses Bank (Lifeline AGM).



Each battery bank has a dedicated BlueSeas remote battery shutoff.



There is a Blue Seas ACR tying the two banks together.



The entire boat is connected to the house bank.



Engine is connected to the starting bank.



I kept the stock 80amp alternator



===================



I'm now considering whether this might be too much for the alternator.



Should I be adding a second 100amp alternator for the house bank??

Your 80-amp alternator, internally regulated, may not last long trying to charge those nice, new AGMs. Take the suggestion, get a larger alternator, externally regulated, with battery and alternator temp sensing.

 

[rslifkin]

Whether it'll kill the alternator or not will depend on how hot the alternator actually gets at full output. It's going to be somewhat sub-optimal charging though.



For the last few years I've been using ACRs to charge the house bank while underway. The stock 55A internally regulated alternators on my engines have done just fine, even when they've run at full output for sustained periods. I think they're just low enough output relative to their size that they don't cook themselves.

 

[Comodave]

If you go above 100 amps you will probably need dual belts or a serpentine belt. What engine are we talking about? I know there are kits to convert to serpentine belts for some engines. But the 80 amp alternator is out of its depth in this application, especially if it internally regulated. Agree go with a big frame alternator with a good external regulator. I like to buy a bigger alternator and then use the regulator to limit its output so it isn’t working at it’s max output all the time.

 

[firehoser75]

The way most boats come "stock", their alternators are setup (like cars) to recharge the engine start battery, supply power for running the engine, and not much more. They usually (in my experience and from talking to many others including marine electricians) as wired with a stock setup, do a very poor job of recharging a (largish) house bank.

Suggestions given so far are good. To recharge a house bank reliably, you should have external 3 stage regulation (user setup allowed), the alternator should be wired to "sense" the house bank, not the start battery, it should be wired to first recharge the house bank, and to avoid burning out the alternator you should have temperature sensing for both the alternator and the batteries (house). Using a larger alternator (as Comodave suggests) to avoid overworking the alternator is great advice.
My Tug had the standard "stock" setup with an 80 amp (auto style internally regulated) alternator, and it never added much if any charge to the house bank, even after long runs. I did not "correct" this, as my large solar array met my house needs nicely, backed up by a 9 Kw generator (if needed).
Good luck and Happy New Year!

 

[Simi 60]

Our large frame alt didn't last long charging AGM.
Smoke two of them
Gave up even trying in the end and if needed to charge during a passage will run the Genset and push in some decent amps.

 

[Jeff F]

I'd approach this incrementally. For sure you want a modern external regulator to prevent alternator overheating and optimize battery health.

Unless you want faster charging a larger alternator may not be required. Your OEM alternator will likely be happy putting out 40a continuously. Take out 15a for house loads underway, and you've got a bulk charge rate of 25a. Maybe that's all you need.

I put in a larger alternator on my boat. In hindsight that was unnecessary for my typical use.

 

[RCook]

I replaced the stock Cummins 19si 105 amp alternator with a 145 amp version from Seaboard. Modified it to external regulation, done with a Balmar MC614.

Charging a 420 ah house bank, and 210 ah start, 210 ah windlass and bow thruster, and 105 ah stern thruster banks (all g31 agm) through ACR's, it lasted some 4000 hours over six summers before finally overheating. Repaired it, and got another new one, also modded to external reg, all for less than $600.

 

[DavidM]

I think a Balmar high output alternator or a high output, externally regulated Leece Neville would be a better choice than the 19i. Externally regulated is usually the key feature for a heavy duty alternator.

For the poster with the twin Yanmar 4LAs on his MS 350, his options are more limited to probably Balmar alternators.

David

 

[O C Diver]

I have a large frame Leece Neville 220 amp alternator with a Balmar external regulator. Each morning after spending the night on the hook, the alternator is putting out near full amperage for a half hour to an hour. Then it progressively reduces amperage. Probably 90+ percent of DC and AC (through the inverter) power is produced through that alternator. It now has 5,000 hours of use over the last 7 years. Right tool for the job.

While underway and most of the time at anchor, my pure sine wave inverter is on. The bow thruster batteries are charged and maintained by a battery charger that funs off the inverter. The engine and generator batteries are maintained by a charger when on shore power. The point is that with a big alternator and a good inverter, it's pretty easy to charge and maintain other boat batteries.

Ted

 

[catalinajack]

Whether it'll kill the alternator or not will depend on how hot the alternator actually gets at full output. It's going to be somewhat sub-optimal charging though.



For the last few years I've been using ACRs to charge the house bank while underway. The stock 55A internally regulated alternators on my engines have done just fine, even when they've run at full output for sustained periods. I think they're just low enough output relative to their size that they don't cook themselves.

Agree, 100%, but an 80-amper, unregulated will go full-tilt-bozo trying to pump current into batteries that have a charge acceptance rate of .4c. It will heat up fast and hard and won't last long with no temp sensing and ramp-down feature.

Consider this article to be found on marinehowto.com.

https://marinehowto.com/marine-alternator-installation-tips-tricks/

 

[sunchaser]

Agree, 100%, but an 80-amper, unregulated will go full-tilt-bozo trying to pump current into batteries that have a charge acceptance rate of .4c. It will heat up fast and hard and won't last long with no temp sensing and ramp-down feature.

Consider this article to be found on marinehowto.com.

https://marinehowto.com/marine-alternator-installation-tips-tricks/

There are thousands of vessels getting by just fine with "standard" alternators. The need to invest time and money into a large external regulated alternator really depends on required charging rate, ER temperatures, cruising regimen, battery design, single Vs twin alternators and past history. Then Balmar Vs Leece Neville (Prestolite) - which is better?

 

[Iggy]

Your 80-amp alternator, internally regulated, may not last long trying to charge those nice, new AGMs. Take the suggestion, get a larger alternator, externally regulated, with battery and alternator temp sensing.

Yep!

The last owner of my boat took out the 80A Alt and replaced it with a 120A. With an external regulator. The engine uses V-belt. To go bigger would mean more money and work. To be safe I added the temp sensor.

40A more does not seam like a lot, but when I did the math. I am only using between 30 to 35A underway. Thats on the high side. Plus, If I have been on the hook for more than a day. I start the genset for 15 to 20mins before leaving. Turning on the inverter charger (90A) so the Alt does not take a big hit on startup.

 

[O C Diver]

There are thousands of vessels getting by just fine with "standard" alternators. The need to invest time and money into a large external regulated alternator really depends on required charging rate, ER temperatures, cruising regimen, battery design, single Vs twin alternators and past history. Then Balmar Vs Leece Neville (Prestolite) - which is better?

Balmar doesn't make alternators. If you take a long hard look at the largest Balmar alternators, I think you will find they look exactly lthe same as Leece Neville alternators. There is also a really bad Chinese copy of a Leece Neville alternator. Hope they're not reselling that one.

Ted

 

[HeadedToTexas]

Won't the 80 amp alternator charge the bank at whatever rate it can, and the 160 amp alternator will charge it at almost twice that rate? Both will get the job done, and it's a choice about how long you want to run your main engine to produce the charge.

 

[guy with a boat]

Won't the 80 amp alternator charge the bank at whatever rate it can, and the 160 amp alternator will charge it at almost twice that rate? Both will get the job done, and it's a choice about how long you want to run your main engine to produce the charge.

This is true if both are externally regulated and setup (limited) properly. Also it is important to know that you won’t get 80a out of the smaller one over time.

Small frame alternators are made to top off start batteries and not designed to run at full capacity for long. They will either reduce the output to a fraction of the nominal output, or run at full capacity until the magic smoke comes out. Either way, its not well suited to charge a larger AGM bank or, even more demanding, a LFP battery or bank.

Large frame, high capacity, good quality alternators can run near their nominal output for the hours that it may take to charge a large bank. They almost always still need throttled down a bit (10% is what I use) to prevent have the temp sensor shut them down to 50% output. Without a temp sensor and external regulator, even the large frame units can be overtaxed, and out comes the smoke.

 

[HeadedToTexas]

My example is very, very simplified, and perhaps has no practical application at all because there are a lot of combinations of alternators and their associated regulators.

That said, if the original equipment 80 amp alternator will charge a single 200 amp-hour AGM with the correct profile and experience a normal life, is the only reason it won't have the same life if tasked with charging two 200 amp-hour AGM batteries that it spends that much more time producing current at bulk charging voltage?

 

[guy with a boat]

Balmar large (maybe all) alternators are based on Leese Neville units. Balmar apparently modifies or hot rods the units to higher durability specs. I don’t know if they have LN build them to Balmar specs or if Balmar does the mods themselves and adds their white paint and labels.

Someone here probably knows the technical differences between the units, but the Balmar is priced significantly higher. The LN by comparison is a good value for a similar component, but we’ll need one of the smart electrical guys on here to discuss what actual improvements are incorporated in the Balmar unit.

 

[guy with a boat]

My example is very, very simplified, and perhaps has no practical application at all because there are a lot of combinations of alternators and their associated regulators.

That said, if the original equipment 80 amp alternator will charge a single 200 amp-hour AGM with the correct profile and experience a normal life, is the only reason it won't have the same life if tasked with charging two 200 amp-hour AGM batteries that it spends that much more time producing current at bulk charging voltage?

I think the challenge for smaller alternators and larger battery banks is that the alternator will run at max amps output for a longer period of time. Small frame alternators tend to overheat if run hard for longer than a few minutes. Large frame units are designed to run hard longer without overheating.

AGM batteries will have a higher acceptance rate, meaning they may suck up the full output of an alternator for a longer period.

As you point out, the endless combinations of specific alts/regulators/batteries makes blanket statements more difficult. That being said, the amperage output is the demanding part, not so much the voltage.

 

[cafesport]

A bigger alternator will only shorten the time your lifelines take to go from bulk to absorb, from there the batteries will become limited to how much current they can accept. Rod Collins did an experiment on a group 31 lifeline agm. The difference in time to full charge from 50% soc was 12 minutes when comparing .4C charge rate to .2C. For your situation start the genny and charge to absorb first thing in the am. Underway your alternator should be able to handle the rest of the absorb to float cycles. No point in burning up what you have trying to charge lifelines in bulk as they can accept 5C during bulk phase.

 

[HeadedToTexas]

I think the challenge for smaller alternators and larger battery banks is that the alternator will run at max amps output for a longer period of time. Small frame alternators tend to overheat if run hard for longer than a few minutes. Large frame units are designed to run hard longer without overheating.

AGM batteries will have a higher acceptance rate, meaning they may suck up the full output of an alternator for a longer period.

As you point out, the endless combinations of specific alts/regulators/batteries makes blanket statements more difficult. That being said, the amperage output is the demanding part, not so much the voltage.

That makes sense. And that means that having an alternator correctly sized to the battery bank it charges becomes more and more important as the capacity of those batteries to accept charge, yes? For instance, LiFePO batteries would "ask" the alternator to charge at full output even longer.

 

[rslifkin]

That makes sense. And that means that having an alternator correctly sized to the battery bank it charges becomes more and more important as the capacity of those batteries to accept charge, yes? For instance, LiFePO batteries would "ask" the alternator to charge at full output even longer.

As you get batteries that can accept more current, you gain the ability to charge faster if you have a big enough alternator. But a smaller alternator will still work fine (just with slower charging) as long as it has output adjusted to its cooling capacity or has temperature monitoring so that it doesn't overheat. There's nothing wrong with the alternator putting out as much as it comfortably can for a few hours.

 

[O C Diver]

A bigger alternator will only shorten the time your lifelines take to go from bulk to absorb, from there the batteries will become limited to how much current they can accept. Rod Collins did an experiment on a group 31 lifeline agm. The difference in time to full charge from 50% soc was 12 minutes when comparing .4C charge rate to .2C. For your situation start the genny and charge to absorb first thing in the am. Underway your alternator should be able to handle the rest of the absorb to float cycles. No point in burning up what you have trying to charge lifelines in bulk as they can accept 5C during bulk phase.

That doesn't reflect consumption while underway. If you have a 30 amp consumption while underway, the difference between a 100 amp alternator versus a 220 amp could be 3 times as long in the bulk phase. Further in the absorption phase the time reduction could be substantial depending on the size of the bank. A 1,000 amp hour bank will have an absorption rate above 70 amps (100 amp alternator less 30 amp underway load) for a substantial time. Lastly, how many hours do you want an alternator at 100% capacity as opposed to a large frame alternator for an hour or so?

Ted

 

[guy with a boat]

That makes sense. And that means that having an alternator correctly sized to the battery bank it charges becomes more and more important as the capacity of those batteries to accept charge, yes? For instance, LiFePO batteries would "ask" the alternator to charge at full output even longer.

Yes, it becomes more important to control the alternator output to what it can handle, since the “ask” will be greater.

An LFP bank will have the alternator running at full output (or regulated max) until the batteries are fully charged, since there is little to no taper. As a side note, adding another alternator won’t split the load, both will run at max output until batts are full.

 

[PierreR]

A lead acid battery will take a .4c charge rate for a very short period of time before the charging rate drops substantially. That is why your 50 amp boost on a car charger will shut off quickly if you are not cranking. Lead acid batteries are really 20c and will not take a continuous charge rate much above that. You can feed all you want to it but it won't take much more than it can. The voltage will quickly jump to 13.5 even though the battery is just about dead. Two 8'ds are about 500 amp hour and 500 amp hour divided by 20 = to a continuous charge rate of 25 amps.
A start battery is a lot of amps for a very short period of time. The chemistry does not have time to adjust so they will replenish that charge quickly. Yes they will take all 80 amps but a deep cycle has the chemistry near balanced and will not take a charge fast for replenishing. 80 amps should be enough for 2 8'ds. If they are low it takes a long time to recharge them, likely more time than you are running in a day.
Lithium is twenty times faster to charge and discharge. That is why they keep up.

 

[Jeff F]

That makes sense. And that means that having an alternator correctly sized to the battery bank it charges becomes more and more important as the capacity of those batteries to accept charge, yes? For instance, LiFePO batteries would "ask" the alternator to charge at full output even longer.

Yes, the batteries will generally accept as much as the alternator will put out until they're fully charged.

It doesn't necessarily call for a larger alternator though. The need for a higher capacity alternator is entirely dependent on how fast you want to charge.

What is important is the heat regulation of whatever alternator you use. A smaller alternator if well regulated will do the job, but take longer.

 

[Mambo42]

I agree with others who have suggested a larger alternator. You have about 300 usable Ah from the 4D's and 100 from the 2 D. However, the start battery should not use too much when starting up.

The main focus is on the 4D's and with an 80 A alternator charging those batteries plus run the boat itself, that is a bit on the low side. You would basically need a minimum of 6 to 7 hours (probably even much longer) to charge those batteries.
Personally I would go to a 150 A alternator but add a wakespeed WS-500 regulator as well. That one will make sure that charging the batteries is done at the best possible way. It is not a cheap regulator, but it is apparently the best there is available at this time.

 

[angus99]

Glad my alternators can’t read this thread or they might throw in the towel. I installed a pair of Delco DN10s, nominally 100 amps, modified for external regulation (Balmar 614s, temperature compensation and Centerfielder). We have a 1,250 AH house bank and 200+ AH start bank. Typically, after a night on the hook, we’re at ~80% SOC on the house bank. After a five-hour or greater run, we seldom see less than 97% SOC when it’s time to anchor or dock again—higher if we run longer. House loads underway are usually modest and include fridges, freezer and occasional microwave use, I monitor the alts’ temperatures as part of hourly ER checks and the outside casing is usually around 135* F. I considered Balmar/Leece-Nevilles at the time but these $100+ Delcos have done the job for us for the past seven years. I do realize the OP has a different set of challenges with a single alternator, but with twins “smaller” alts work for us without changing belts or pulleys.

 

[Iggy]

I agree with a lot that have been posted. For those that have small ALTs. they will run at 100% longer. That may cause it to over heat and burn out. But if they install a temp sensor that should back of the charge rate and save the Alt. Yes?