Charging House Bank While Underway

[Mambo42]

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.

The difference between you and Shrew is that you are charging roughly 250 Ah with 200 A (total) alternators.
Shrew on the other hand is trying to charge 300 Ah with a 55 A alternator plus run the normal boat instruments and appliances.

 

[O C Diver]

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??

While my preference is obviously for a large second alternator to charge the house bank, have you looked at replacing the original alternator (save it for a get home spare) with a larger amperage one that would fit in the same location and use the same belt configuration? Don't know if a 100 amp alternator that was a direct swap and would use the same belt configuration is available. A 25% increase could make a significant difference as none of your loads or battery charging should change.

Ted

 

[Jeff F]

Let's keep the comparison valid. Angus99 has 1,450 ah installed capacity supported by 2*100a rated capacity. The OP has ~800 ah installed supported by 80a rated capacity.

I don't think there has been enough information provided by the OP to support the claims that a larger alternator is necessary or beneficial for their use case. It might be, but it also might be time and money invested to solve a non-existent problem.

 

[O C Diver]

It would also be helpful to know if the alternator is optimized with an external multi stage regulator and protected by a temperature sensor on the alternator. If not, adding them to the charging system, may make enough improvement by itself.

Ted

 

[Jeff F]

It would also be helpful to know if the alternator is optimized with an external multi stage regulator and protected by a temperature sensor on the alternator. If not, adding them to the charging system, may make enough improvement by itself.

Ted

Right. Add a good regulator now, and go use the boat. Nothing will break or be damaged. If after that you recognize the need for more charging capabilities you can upgrade the alternator. Or add solar.

I knew we'd reach a consensus [emoji3]

 

[bshanafelt]

My system as described, is now 14 years old. The original battery bank was replaced in 2020 & I sold that 'used' bank for about 60% of the price I paid in 2008.

my point is that if you build your system robustly enough and compensate for heat and operate it under max capacity, then all parts will last.

The following comments are from 10 years ago.

Previous posts:


There is no question that bigger is better when talking alternators and DC charging systems. The heat issue ends up being the biggest enemy of the solid state parts as well as bearings etc on the alternator.

Using a large frame unit, then de-rating it via a smart regulator will ensure a long life for your system. Always use temp sensors on both the alternator and battery bank.

My boat came with a stock 60A small frame and when I asked it to try and charge a house bank around 500Amps, it simply could not do the job.

I then upgraded to a small frame on steroids 120A unit coupled with a smart regulator, which did an adequate job, but got REALLY hot.

Since my motor has a serpentine belt, it was a fairly simple matter to fit a large frame 200A unit, which charges my now very large 1350AH bank quite nicely. I have de-rated the alternator to 160A so it never runs at the max design in any circumstance.


If you have room and pulley/belt ability, just get a truck alternator - Ebay has lots of choices Leece/Nev 160-200A units are around $200.


It is always easier on the entire system to use less charging than you have available.


If you decide to upgrade the capacity of your Alternator, it will mean a number of 'other' costs as well.

First you must determine if your pulley/belt arrangement will be adequate. The normal rule of thumb is a single belt will safely give 100A or less. Dual belts or serpentine for greater than 100A. Determine if the side loading of the main bearing or waterpump you take off will be a problem.

As mentioned, if you change frame size, there can be mounting brackets etc to install/design.

Next, if you trade out a stock 60-70A internally regulated unit for a high-amp one, the cables will need to carry the extra juice - this normally means wire that is big enough - be sure to check a table or two for sizing properly - Don't forget fusing.

Of course, the Regulator will need to be a multi-stage unit. Balmar, Ample etc make some good equipment which will survive the marine environment well. The nice thing about these regulators is they are fully programable for the different stages of charging, battery types etc.

Then will come the 'how do I keep my start battery charged?" issue. These days an echo charge unit is hands down the best solution to the problem - Balmar, xantrex etc make good ones. This gets rid of the battery isolator - which never works well and makes more unwanted heat.

By this time you have spent some $$ and time designing a good DC system, so you will have already determined your usage needs and sized the house bank appropriately, and may decide it is time to make the bank bigger - thus necessitating buying an entire new house bank of AGM batteries to accept all these amps you now can produce.

You must also have a way of monitoring the beast - a link or other 'smart' monitor is pretty important to the health of your system.

It is a slippery slope when you really look at what is necessary to 'oversize' things.

The good news is you may just not need a generator after you get your DC system in shape.

below is a schematic showing the arrangement on my boat.

I have the ability to stay anchored in one location for up to 6 days and still be above 50% of Bank capacity. We usually stay 3 days max in any one place, but the option is there.

Good luck

 

[cafesport]

Lifeline recommends .2C output current chargers for deeper than 50% DOD charging. I think they understand a bit more about the charge acceptance rates of their batteries than most who have commented so far.

I also doubt the OP is consuming 300 amps overnight, but even if he was his current alternator is fine as long as he lets the generator do the heavy lifting of bulk charging before departing.

Per Rod Collins’s experimental data, doubling the charge rate to .4C shortened the time to full charge by only 12 mins or about 3 percent of the total charging time. It shortened bulk phase by an hour and lengthened the absorb phase by an hour. It took 5.2 hours to recharge to float vs 4.2 hours at .2C for a total time of 5.5 hours. Of note is the charge acceptance rate after 1 hour at .4C. Take a look at his website photos (20 amps). This was in actuality .2C and dropping fast.

 

[88FuHwa]

Low Idle Alternator Output

I had a stock 90 Amp Motorola alternator on our Perkins 6.354 driven vessel with an internal regulator. My house banks were always depleted after a day's cruise. Before getting the external regulator from Wakespeed installed I was advised to get the alternator internal regulator removed by a marine electrical shop. Once I told the technician what the purpose of the external set up was he reminded me that most trawlers like ours run at low speeds and, ergo, a stock alternator also does not produce the full amps. This is not my expertise but after they told me that their main clientele are party boats captains that go fishing outside the Golden Gate. Once out there, these boats also mostly run their engines either at idle or low speeds. The solution that the shop presented was a 100 Amp low idle alternator that does not require external regulation.
This solved my problem with keeping the house bank 4 x 6v golf cart batteries charged while underway. If interested in more info or you want to discuss with the alternator dealer, his shop is in downtown SFco, let me know.

 

[catalinajack]

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?

Goes without saying. I was responding to a guy who has needs.

 

[MVDarlin]

Wow. Complec issue. I have made it even more complex on my boat. My house bank is lithium.