Alternators, Charging Circuits

[Meantime]

15 hours ago, PaulN said:

Not sure why this format is inefficient but would be a major job to change. However I accept any advice, but not sure what you recommend I should be doing.

I suspect Annv is making comment about the way the battery bank is connected to the rest of the boat and it is actually a very easy thing to correct.

If I look at your picture above the two Red Rolls batteries are labelled as bank2. Lets call the bottom battery A and the one above it B. You have two cables connected to battery B, one to the negative and one to the positive terminal. These are then connected to the corresponding terminals on battery A. There are then two thick wires that run off to the right which presumably supply various circuits around the boat. Let's call these the load wires. The correct way to wire the bank of batteries to the load wires is to have either the positive connected to battery A positive and the negative connected to battery B negative or the positive connected to battery B positive and the negative connected to battery A negative. It will be as easy as moving the negative load wire from your battery A negative to your battery B negative.

Every piece of wire no matter how short has a resistance and the more power you draw the more the resistance goes up. Voltage will also always take the path of least resistance. The way your bank is currently configured more power especially under heavy loads will be drawn from battery A and once the load is removed battery B will slowly discharge into battery A until they are both equal again. Connecting the load wires across both batteries ensures equal drain and wear and tear on both batteries.

Looking at bank 1 in your picture above, lets call the top battery D and the one below it battery C. It is simply a matter of moving the positive load wire from battery C to battery D. If you move the negative instead, it looks like there are two wires running off to the rest of the boat, so both would need to be moved. Fractionally easier to move the positive wire in this case.

 

[Meantime]

On 05/12/2022 at 11:28, Vaughan said:

The intelligent regulator fools the alternator into providing a few more amps than it wants to, to complete the final charge of the batteries.

As a battery charges its voltage goes up and as the voltage goes up the alternator starts to reduce the amps it puts out, thus you never really fully charge a battery from an alternator. An intelligent, or advanced regulator drags the voltage from the alternator lower, thus making it provide more current. The regulator then steps the voltage up on the output side, whilst providing enough current to fully or very slightly over charge the battery.

Fully charging or even slightly over charging a battery occasionally helps to prolong the life of the battery. It is my personal opinion that you do not need to do this every time you charge the batteries. Fully or slightly over charging a battery can very easily cause it to boil some water off. If you are using sealed or maintenance free batteries they will still lose water, but you won't be able to refill the lost water.

The advantage of an intelligent or advanced regulator is that you will charge batteries faster and probably about 10% more capacity than just off the alternator. 

If using sealed or maintenance free batteries I prefer to use an intelligent 3 or 4 stage charger when on shore power to leave the marina with maximum charge and then just rely on the standard alternator as although you won't fully recharge the batteries, it will be near enough and kinder to the batteries in the long run, as long as they do get a full charge on shore power regularly.

[Meantime]

On 05/12/2022 at 12:43, Regulo said:

The  Sterling advanced charge regulator is highly recommended by me, but it does involve getting into the alternator.

The newer option is to use an alternator to battery charger which involves no modification of the alternator. It also removes the need for split diodes. An alternator to battery charger input connects to the output of the alternator and then there are two outputs, one is connected to your starter battery and the other is connected to your domestic battery or bank. When you first start the engine the charger will direct all charge to your engine start battery. Once it reaches a certain voltage, it will then divert charge to your domestic bank using an advanced 3 or 4 stage charge profile. It has the ability to drag the input voltage down to make the alternator charge harder and then regulate the output to the domestic bank in a 3 or 4 stage charge pattern to fully charge the domestic bank.

Should you need to charge two domestic banks as in Pauln's case then you would put a split diode on the domestic bank output from the alternator to battery charger and then connect the two domestic banks to the split diode.

[Regulo]

I'm still confused as to why the domestic batteries are in two banks? What advantage does this confer? There must be a reason - I await enlightenment! 

[Meantime]

41 minutes ago, Regulo said:

I'm still confused as to why the domestic batteries are in two banks? What advantage does this confer? There must be a reason - I await enlightenment! 

I suspect for flexibility. I have 2 x 12V batteries in series to give 24V that power my fridge and heater and coffee machine. I have another 2 x 12V batteries in series that powers the winch for the sliding roof and the invertor that provides 240V. The immersion element is also connected to this bank, however using the immersion really hammers the batteries so I have an isolator between the two banks that allows me to connect the two banks if I want to power the immersion. In normal use the two banks are separate and if I manage to flatten the bank with the invertor connected my fridge is still safe and hence no warm beer.

It's also easier for fault finding. If you have 4 x batteries all in parallel and one of them goes faulty it will drag all four batteries down very quickly. Unless you separate all of them it is hard to determine the culprit.

[Regulo]

That makes a bit more sense, thanks for the explanation. I have to admit I've never come across a split domestic battery set. Knowing the unreliability of some isolator switches, I'd worry I'd be introducing more trouble! 

[mikeyboy1966]

All interesting reading 

for a bit of fun,

can we come at this from a different angle?

clean slate.

Assume these things.

alternator currently fitted will stay

3x 120amp domestic batteries 

1 x120 starter battery.

boat has recently fitted vitron charger on shore power.(fairly high spec I think)

if you had an ultimate spec system what would you fit,from alternator to batteries.

there was mention in a previous post about “intelligent splitters” over blocking diodes but there was no elaboration.

I have no need for inverters and the like,

1xcompressor fridge

1xcompressor coolbox

lights all led.

eberspacher heater

2xelectric loos

12v sockets and usb chargers.

water pumps

bilge pumps and any other normal stuff if I’ve not listed.

performance and reliability are on my want list.

I’d like to be confident to relocate the boat via sea crossings and tidal rivers ,so you guess where I’m coming from.

im also not overly bothered about solar panels .

 

 

[annv]

[annv]

[annv]

Hi Micky This is my choice plus two alternators one of 60 amp and one of 180 amps along with a combined intelligent charger that combines both to charge domestic bank and or engine battery. Ideally you need a bank to last two days with a max load ie heating, fridge, toilet and water pump. Having two banks of two rather than just one bank of four just flogs one bank rather than spread the load over all .this could mean you have to change your battery's more frequently and there for more cost. As with most things there is a cost involved for the best system. Plus adding a solar panel helps no end in maintaining the battery's charge there for adding to there longevity and less cost overall. John PS photos should have come last finger trouble along with no grand son available. John