How do your alternators recharge batteries?

[MapisM]

Today I learnt yet another peculiarity of my new to me boat.
It's an electrical setup I never heard about before, and I'm curious to hear the panel views on that.

It all started when I asked an electrician (who used to work for the builder) why the "parallel" command is through a toggle button rather than a momentary button.
After all, it's only meant to work for a few seconds, in order to start the engines in the event of an engine battery fault, right?
Wrong. Well, wrong in DP boats, that is.

I was explained that the parallel connection is designed to work at all times while the engines are running, because as soon as the engines are on, three things happen (automatically):
1) the battery charger is disconnected, and
2) the engines + services battery banks are connected in parallel, and
3) both alternators recharge in parallel both battery banks.

Does anyone have a similar setup, and/or have you ever heard of it?
Regardless, what's your take on that?
TIA!

 

[Portofino]

"similiar "
I have a push pararell button - hold it down to nick Dom batt juice incase engine bank can,t turn the starter motor .
You have to push it -spring loaded off

Also a seperate toggle to interupt normal split diode system of recharging the engine batts ; let's face it 10 seconds work for 2 x 180 ah via 24 v -hardly breaking sweat !
Flicking this directs alternators to the Doms 1st they get priority over the engines
Kinda reverses the split diode thingy
The only reason I can think is if on an extended passage ( engines running )
And very heavy Dom predicted comsuption --I don,t know a heavey inverter or something ? You can interfere with the auto bat recharge .
As an aside we no caloifier the only way to heat the water in the hot tank is 220 v shore or an "inverter " so depending when engines running how the Doms are doing - I can in theory I think support them .
Weird v weird

In reality if the boat works -many ways to skin a cat - kinda - just try it use it as you would normally .
Eg .
We have two 220 v chargers a main one for the boat 80 ah and a seperate smaller one for the dedicated Geny bat .
Don,t know if they turn off when engines running and shore power on ( breakers on too ) we turn the shore power off before starting engines -normally .
But I suspect like others in the heat of the mo ,I have fired up before turning or disconnecting the shore power -no harm phew done so far .

 

[halcyon]

Does anyone have a similar setup, and/or have you ever heard of it?
Regardless, what's your take on that?
TIA!

Yes, we bought one out in 1984, fitted to Sealines and others, charged three battery banks from two engines.

Brian

 

[BartW]

Never saw a setup exactly like that
And I don’t completely get the reason why it works as it does,

BUT,

In my Karnic I have a Victron Cyrix battery combiner,
https://www.victronenergy.nl/battery-isolators-and-combiners/cyrix-battery-combiners

which does more or less the same; linking of two battery banks,
the device does this automatic by looking at the DC voltages.
it does not disconnect the charger !
but the device has some intelligence:
when the battery charger is charging, (or one engine/alternator is running) and the voltage is>13V, the combiner will engage automatically, and the second battery will be charged in parallel.
When one of the two battery’s is below <11,5V the device does NOT engage, (as a safety precaution in case there is something wrong…)

At anchor, when the battery voltage is at nominal 12.3v,
the cyrix is NOT engaged,
so that you can’t drain the engine batt bank with domestic consumption.

I don’t understand why your setup disconnects the charger,

You know on BA, on each side the alternator and charger operate in parallel
each time the genny is running during navigation, we have that situation,
And when I engage the momentary parallel switch, they are all in parallel; all batt’s, 2 alternators, 2 chargers, and probably later also the solar MPPT.

You could talk with the Italian Victron guy,
he might know your setup, or have comments about it…

 

[kashurst]

the explanation is not really wrong just short on detail. My T50 did pretty much as Mapism described. It had separate alternators for each engine and a split charge diode pack so one engine could charge both battery banks, When the charging voltage on the two battery banks got close, a voltage sensitive relay would close and effectively I had one big battery bank

Never really understood the point to be honest - but it did work OK

the battery chargers stop charging when obviously the mains voltage goes off. However if you have the engines running and shore power on/gennie on either the battery charger will do the work or the alternators - it doesn't matter.

 

[jfm]

I don't like step 2 if when you start the engines after a night on anchor the engine starter batts are 100% and the house batts are 40%. I'd much prefer a split charger relay.

I'm not too bothered about automatically disconnecting the charger when the engines run, but I don't much see the need for it and it seems pointless. It seems suboptimal if the output of the alternators is less than the max charge acceptance of the batts, which is common, although not the case on my boat

If you have an explanation of why DP did all this, I'd be interested to hear. Maybe they had a good reason

 

[MapisM]

I don't like step 2 if when you start the engines after a night on anchor the engine starter batts are 100% and the house batts are 40%. I'd much prefer a split charger relay.

Bingo.
In didn't mention it in my OP because I wanted to hear other views about it, but that's exactly my concern with the parallel connection of two separate battery banks which (potentially) needs a completely different recharging current.

If you have an explanation of why DP did all this, I'd be interested to hear. Maybe they had a good reason

I did ask Mr. DP already, but aside from mentioning the obvious advantage of a fully redundant battery charging (if one alternator - or even a whole engine for that matter - is disabled for any reason, you still have the other one doing the same job, albeit at half power), he just told me that this was the configuration of all the boats they built, up to 80 footers, and never had any troubles.
He also told me that a sistership of my boat recently changed the six years oldservice batteries ...
If the batteries I just purchased will last that much, I won't complain!

Actually, I suspect that there must be some more clever components somewhere between the alternators and the batteries - I've seen for instance a rather sophisticated Balmar voltage regulator on the ORY 70 whose owner you met, but I didn't have time yet to dig into all these details...

Anyway, whoever designed the electrical system of DP boats surely had some clever ideas, based on what I could see so far.
Aside from some convenient features which I can't remember to have seen on any other boats, like the batteries switches remotely controlled from the p/house, another nice thing I just discovered is the e/r blowers operation, which is thermostatically controlled. Nothing special per se, but the peculiarity is that there are two thermostatic switches.
One is connected to one engine key contact, so it only works while the engines are running.
The second works also when engines are not running (anymore), and is meant to cool down the e/r upon arrival.
This way, it's possible to set the thermostatic switch meant for cruising (when the engines are "breathing" a lot of air) separately from the other one which is meant to cool the e/r upon arrival, after engines are turned off.
Fwiw, the suggested temp is about 45C while engines are running, and 50C after turning them off.

 

[halcyon]

Bingo.
In didn't mention it in my OP because I wanted to hear other views about it, but that's exactly my concern with the parallel connection of two separate battery banks which (potentially) needs a completely different recharging current.

Only a problem if connected in series, effectively the low battery bank will take the charge until near the capacity of the higher charged one, then once balanced they charge as one large bank. This was the theory behind the VSR charging system.

Can you confirm what battery banks you have, i.e. engine & engine + service or common engine & service bank, thinking ref alternators connection.

Brian

 

[Hardmy]

Both my engine alternators charge only the starter batteries. When underway, I have to turn a switch to connect hotel+starter together so both banks are being loaded.

Since I have swapped all my hotel batteries with new gels, while the starter batteries are still lead acid I believe that it is not advisable any more to charge them together. Hotels are now only loaded by solar 10-15A charging current the whole day and genny/shore power. This seems to be enough to keep them topped up.

But this set up is not satisfactory and I am considering installing an AtoB from Sterling. As does a regular 220V battery charger, it would charge 3 different banks of batteries, with an adapted loading curve for each bank. Mapis, did you consider to install such device?

My electrician says, the Sterling has a tendency to catch fire, so does a guy I know from a german forum. But I've also read plenty of positive reviews. Does somebody here have experience with such device? Are there other brands with similar products?

 

[MapisM]

Only a problem if connected in series, effectively the low battery bank will take the charge until near the capacity of the higher charged one, then once balanced they charge as one large bank. This was the theory behind the VSR charging system.

Can you confirm what battery banks you have, i.e. engine & engine + service or common engine & service bank, thinking ref alternators connection.

Brian

You meant "Only a problem if connected in parallel", I suppose?

Anyway, I've got two banks, all 24V:
A) engines (2x12V batteries in series);
B) domestic (made of 2 banks permanently connected in parallel, each with 4x6V batteries in series)
Upon engine start, a relay connects A+B in parallel, and both alternators recharge A+B.

 

[MapisM]

Mapis, did you consider to install such device?

Nope - and I must say that any equipment with a tendency to catch fire doesn't sound very attractive for a boat installation....
What I am considering is an upgrade of the inverter & charger, currently split in two units, of which the first is a very small Mastervolt, which does its job but is only good enough for the TV or phone chargers (all fridges are 24V).
I would very much prefer, based also on the positive experience with the previous boat, a Victron combined unit, with a more decent capacity on the inverter side.
And I might as well take the occasion to give solar panels a thought - btw the boat has a wide area in front of the f/b windshield, good for something similar to what Hurricane did.
But that's all for next winter!

 

[Hurricane]

And I might as well take the occasion to give solar panels a thought - btw the boat has a wide area in front of the f/b windshield, good for something similar to what Hurricane did.
But that's all for next winter!

Wow - maybe another convert.
I'll let you know how mine get on - later in the season.
I wanted to do it sooner but I broke my ankle and boating this year has been delayed.

Having said that, I've been watching this thread and I decided not to mention solar.
The reason is the way that you use your boat.
I know that you go out from your home port and stay overnight on anchor but you have some of the most beautiful cruising areas in the world - on your doorstep.
Meaning that you are less likely to fall into the same problems that I have.
Generally speaking, boat builders install enough battery capacity to last a few days at anchor by running generators to do the "bulk charge" thing and quickly bring them back to a useful state.
In my case, it is the fact that we don't finish off the charging process every morning and that over a period of time (even as short as a week) the battery levels can get dangerously low.
In my case, I am hoping that the solar panels complete the charging process through the day - ready for another night of discharge.
In your case, (and if you were staying close to San Pietro) you would probably want to pop back in to restock food and go out to restaurants etc - and plug back into the shore supply.
After all it is only a short trip back out to those lovely anchorages.

 

[MapisM]

I'll let you know how mine get on - later in the season.
I wanted to do it sooner but I broke my ankle and boating this year has been delayed.

Having said that, I've been watching this thread and I decided not to mention solar.
The reason is the way that you use your boat.
...

Hija, M!
Sorry to hear of your ankle. I'm also having some troubles with one of my Achilles tendons ATM, which is very annoying and takes forever (up to two years, as I'm told!) to recover - though at least there's nothing broke.
Your problem sounds more serious, but hopefully you will recover faster and completely. I sincerely wish you so, anyway!

Your point about the usefulness of solar panels depending on the type of boat use is indeed a very good one.
Probably, for my typical usage, it isn't worth installing the panels and all the other bits.
Funnily, they might be useful for me this summer, 'cause we are thinking to stay as much as possible out at anchor, while heading S along the Croatian Archipelago - in fact, that's what we already did back in the early naughties with the previous boat, staying away from marinas for up to two full weeks in a row!
But there's no way I can add anything to the list (yet to be completed!) of refitting projects at this point in time, and probably it wouldn't be worth anyhow, for one season alone.

Mmm... Yep, maybe it's better to put this in the "possible future upgrades" list (together with gyro stab and a few other things), depending on if and when I will wish to cruise more frequently far from CF - which doesn't seem very likely, in the near future.
Thanks for the very useful thought! :encouragement:

 

[benchmark]

.

I was explained that the parallel connection is designed to work at all times while the engines are running, because as soon as the engines are on, three things happen (automatically):
1) the battery charger is disconnected, and
2) the engines + services battery banks are connected in parallel, and
3) both alternators recharge in parallel both battery banks.

Does anyone have a similar setup, and/or have you ever heard of it?
Regardless, what's your take on that?
TIA!

That is exactly they way it works on my boat too (with a little extra features by the side too) via a small brickshaped device made by CTEK called a Smartpass. the only difference is that i have just one alternator.

I have my Smartpass as a stand alone system which keeps the start battery sacred and all drain is from the House battery. As soon as the engine is running and the alternator is charging, it switched all drain to the extra juice crated from the alternator. it also serves as a battery cut out . likewise automatically gives help from the house battery if the start battery ia not enough to start the engine. Finally, it serves as a battery maintainer for the start battery by trickle charging it when the house battery is fully charged from the battery charger or from my solar panels.