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Old 14-06-2021, 08:25   #1
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Complicated charging 12V/24V/220V

I am trying to sort out my charging situation and I am getting confused about the best practice approach. It is a mixed 12V/24V/220V power boat, 48 ft.

Charging sources
- Two alternators 120A mounted on 450 hp Cummins, one 24V starting bank
- One generator, 220V with 12V starting battery
- Shorepower with a 24V charger

Batteries
- one 24V starting bank for both engines
- one 12V battery for generator
- one 24V house bank midship
- one 12V bow thruster bank with assoicated 12V charger

Main loads
- Everything is 24V, including windlass, except bow thruster 12V
- Separate 12V circuit for minor electronics through a 24V-12V 30A converter

Currently, all the batteries are charged with via the two 12V and 24V chargers except the generator starting battery which is Teed off the 24V engine starting bank... not ideal. So, my plan is the following:

1. Connect the generator starting battery to the 12V thruster bank in the bow. It will be a long cable run but charging current is relatively small. This way, when connected to shor power or running the generator, all the batteries will be charged properly through 3-stage charging.

2. I would like to be able to charge the batteries while running the main engines. This would require charging controllers for two alternators that supply and 3-stage regulat both 24V and 12V... sounds expensive.

Would it not be easier to connect the alternators directly to a 24V to 220V inverter that will plug into the shore power inlet (via some safethy switch). It will not be super efficient but with these engines, efficiency is hardly a concern. The cost of a simple, cheap inverter is small and I will have solid charging to all batteries.

Is there a simpler way to do this? Will charges run of a modified or pure sine way inverters?

Next question, is it a problem if I leave the alternators connected to the 24V system and install relays on the chargers, so that when the main engines are stopped, the relay disconnects the chargers but the inverter continues to supply 220V from the batteries for house loads (laptops, etc.). The benefit here is that if I can use one inverter for everything, I would buy a high quality sine wave inverter. Otherise, I would need to get separate inverters?

Thank you,
ex-Pizzazz
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Old 14-06-2021, 08:57   #2
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Complicated charging 12V/24V/220V

Get some Victron 24v to 12 v battery chargers. Run everything as 24V and simply drop to 12v as needed. My last boat was 24v. Mains battery chargers and alternators should remain 24V , charge the 12v batteries from the 24 v system via the dc dc converters.

Generally windlass and thruster batteries arnt not hard pushed anyway.

The inverter charger idea is very inefficient

If you have all 24V charging to the main batteries then these is no issues anyway
The key is to pick one voltage as the system voltage and drop from that where only necessary
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Old 14-06-2021, 11:26   #3
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Re: Complicated charging 12V/24V/220V

Thank you for suggesting 24/12V dc-dc battery chargers. The issue here is efficiency both in terms of initial cost and fuel cost. The 24V alternators are cheap and do not produce enough voltage to charge the 24V batteries well. I do understand that the best way is to install an alternator voltage regulator and then the 24V-12V DC-DC chargers but the cost of this setup and the install is significantly higher than the invertor which allows me to fully charge the batteries through the chargers.

On a small boat, the efficiency is key, where you have a 20 hp engine and the alternator may be pulling in 3-4 hp but on 2x 450 hp I just do not see the efficiency as a factor. Not to mention that I now think that the inverter could be used both for charging and providing 220V with appropriate relays to avoid a circular battery-inverter-charger-battery (that would be mega silly).
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Old 14-06-2021, 12:32   #4
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Re: Complicated charging 12V/24V/220V

I would not recommend your proposed solution of connecting a 24v->220v inverter directly to the alternator(s) and then plug into the shore power inlet so that your shore power charging system will charge the batteries. While there are a number of problems with this solution, the most serious one is that the the inverter will shut down whenever the alternator(s) are delivering less power than the charger(s) currently require, because the system has no mechanism to reduce the charging rate to what is available.
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Old 14-06-2021, 12:40   #5
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Re: Complicated charging 12V/24V/220V

Most generators I'm familiar with have a small alternator to charge their own starting battery. Does yours not have this? Could it be easily added?
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Old 14-06-2021, 13:05   #6
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Re: Complicated charging 12V/24V/220V

I use a pure sine inverter that supplies 8kw of 120/240v 24/7. I liveaboard so the inverter is never off. The boat is mostly ac except for nav lights and equipment. All ac goes thru the inverter that transfers power when ac is cut off. Big items like the water heaters are usually only run when on shore or generator power, but inverter will power anything on the boat at the cost of the batteries. I use 2 48v alternators when cruising to keep the inverter bank up without the need to run a generator. I have 12v starting using 8d batteries for 2 mains and 2 generators.

I think if you try to run an inverter directly off an alternator you'll have a high failure rate of the inverter components. Inverters like a steady voltage and amp flow.
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Old 14-06-2021, 22:02   #7
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Re: Complicated charging 12V/24V/220V

Quote:
Originally Posted by Lepke View Post
I think if you try to run an inverter directly off an alternator you'll have a high failure rate of the inverter components. Inverters like a steady voltage and amp flow.
This is a fair point. It needs a battery to keep it steady. My dilemma is that I have these large expensive smart chargers and now I need to buy more alternator regulators to achieve the same task.

How about if the inverter is connected to one of the banks (say house) but I set the inverter to switch off if voltage drops below 26 volts. In this way, I have the circular thing going, house battery - inverter - charger - all batteries but only if the voltage on the house battery increases into charging territory after the alternators kick in. I expect the 2x 120A alternators to produce at least 1/4 of their output which will be enough to power the chargers.
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Old 14-06-2021, 23:39   #8
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Re: Complicated charging 12V/24V/220V

Quote:
Originally Posted by Pizzazz View Post
I am trying to sort out my charging situation and I am getting confused about the best practice approach. It is a mixed 12V/24V/220V power boat, 48 ft.
.....................
Quote:
Originally Posted by goboatingnow View Post
Get some Victron 24v to 12 v battery chargers. Run everything as 24V and simply drop to 12v as needed. My last boat was 24v. Mains battery chargers and alternators should remain 24V , charge the 12v batteries from the 24 v system via the dc dc converters.

Generally windlass and thruster batteries arnt not hard pushed anyway.

The inverter charger idea is very inefficient

If you have all 24V charging to the main batteries then these is no issues anyway
The key is to pick one voltage as the system voltage and drop from that where only necessary
Pizazz, if you truly want 'best practice', take the above advice from goboatingnow however if you only want something cheaper (and more complicated) keep looking.

IMO.
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Old 15-06-2021, 00:08   #9
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Re: Complicated charging 12V/24V/220V

Does the generator self charge generator starter battery when running??
If so you wouldn't need a big charger, just a trickle permanent would keep maintenance low.

Mains 220v to cabin, does this run off 24 v bank and automatically switch to shore power whilst charging bank when plugged in?
If yes, I'd think of adding charger to 220v system.
If generator doesn't recharge its own during operation, intelligent charger might be better choice. They're quality plus cheap. Quality includes functions such as battery recovery in times of need. Also doubles up as 24volt charger with functions in times of need if main charger fails whilst with access to shore power.

Just multiple covering your energy needs but seems to be quick simple solution.

Or as goboatingnow typed.. looks more reliable thus boaty..
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Old 15-06-2021, 00:27   #10
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Re: Complicated charging 12V/24V/220V

1. There is no need to charge the gen battery. The gen will charge itself while running. The only reason you’d need a charger if the boat sits many months without running the gen. To maintain the battery. Disconnect the compleatly wrong center Tap from the engine battery and let it be independent.

If want to maintain it while it’s not running. Then get a dc to dc charger from the house bank. You can’t just join it with the thruster bank. Because then it’s becomes one bank. If you did this you’d have 100s of amps in that linking cable when running the thruster.

2. Charge the 24v banks from the Alts. Just like you are doing. The engine bank Needs very little charge. So you need to make sure both Alts can charge the house. Otherwise you are wasting a whole alt if each one does each bank. There are different ways of doing this. Acr beteeen banks. Both Alts direct to House bank and echo charger from house to engine. Etc The 3 stage reg is nice and will charge a little better. But 98% of the boats out there do not have that and are working just fine.

3. Get a 24v-12v dc charger for the thruster bank and charge from house bank.

If you need more charging then alternators Do each day. Then run your gen a bit with the chargers.

Trying to use your chargers from the inverter is simply dumb.
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Old 15-06-2021, 00:47   #11
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Re: Complicated charging 12V/24V/220V

Two options pictured..

Pros/cons.

Battery to battery charging. 24v bank will always have a load with such charger. Might interfere with shore charger detection of charge.

Whereas plug into inverter output charger. Generator should have own charging system during operation thus plug to charger will require an isolation relay to disconnect charger automatically during generators operation spans.
But when ashore on mains, both banks are kept at optimum service capacity.

Battery to battery would be a better choice bias towards never ashore option IMO because batteries never get rested.

But if cruising from slip, out afew weeks, home again type, inverter is off, plugs have been isolated from such and are traveling main currents, batteries are charging independently of each banks thus maintenance costs reduced regarding life cycles of the big bank.
Plus if main charger breaks, you're already carrying your spare.
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Old 15-06-2021, 00:52   #12
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Re: Complicated charging 12V/24V/220V

Quote:
Originally Posted by smac999 View Post
1. There is no need to charge the gen battery. .

Trying to use your chargers from the inverter is simply dumb.
.
Ain't dumb bro.

It'd sit there on trickle. Barely visible to usage.
Prolonging battery life.
Ensuring a charged battery is present when needed to charge the batteries.

Although, start engines up another option.
Relay and smart charger maybe$200.
48 foot motor yacht?

But I agree. Might as well be turned off for days on end. But there at shore. There to switch on at desire if an extended voyage.

My 2 cents.
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Old 15-06-2021, 02:17   #13
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Re: Complicated charging 12V/24V/220V

Quote:
Originally Posted by Pizzazz View Post
I am trying to sort out my charging situation
Main loads
- Everything is 24V, including windlass, except bow thruster 12V
- Separate 12V circuit for minor electronics through a 24V-12V 30A converter

Currently, all the batteries are charged with via the two 12V and 24V chargers except the generator starting battery which is Teed off the 24V engine starting bank... not ideal. So, my plan is the following:

.

2. I would like to be able to charge the batteries while running the main engines. This would require charging controllers for two alternators that supply and 3-stage regulat both 24V and 12V... sounds expensive.

Would it not be easier to connect the alternators directly to a 24V to 220V inverter that will plug into the shore power inlet (via some safethy switch). It will not be super efficient but with these engines, efficiency is hardly a concern. The cost of a simple, cheap inverter is small and I will have solid charging to all batteries.

Is there a simpler way to do this? Will charges run of a modified or pure sine way inverters?

Next question, is it a problem if I leave the alternators connected to the 24V system and install relays on the chargers, so that when the main engines are stopped, the relay disconnects the chargers but the inverter continues to supply 220V from the batteries for house loads (laptops, etc.). The benefit here is that if I can use one inverter for everything, I would buy a high quality sine wave inverter. Otherise, I would need to get separate inverters?

Thank you,
ex-Pizzazz
I think it'd be cheaper to charge directly from main engines alternators than something I didn't quite understand. Simply a simpler circuit.

I wouldn't touch bow thruster battery because it's already working well.

Generator battery hasn't a load until operational. I'd charge that though, why not.

You read of shore power usage.
Isolation of sources is to protect boom going bang.

I'd have a plug to shore. Then switching relays that switch off inverter and switch on battery chargers.

Those smart chargers will destroy batteries if on whilst battery has load. I know mine will because it'll assume a vehicle needs a jump start and open its electron throttle body.

Hence at shore plug, an automatic priority to mains switching relay relating switches to battery chargers.

Depending upon your boat usage, you can go either way and connect a 12 v charger plug to inverter output or pre switch mains output.
If mains output you can manually charge underway if travelling days on engine by plugging the plug via inverter but need to unplug prior operation. Or expensive with another relay that isolates usages such that there is no physical way to power charger when generator is on.

Sail boats have different usages.
Having studied BachengEE and knowing that sail boat engine a much less turned over generator, I'll be plugging charger in post inverter but between them shall be an physical isolation relay.

Dumb arse me didn't type that above. All good

Probably mistakes in that too. I read like you know Watt you are doing though.
Best luck sir
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Old 15-06-2021, 03:44   #14
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Re: Complicated charging 12V/24V/220V

My apologies for babbling. Different systems using same efficiency.

Most brace clew and seem to embrace clues at a nearer to source point.
Some give the leading edge a clew and enjoy a better higher rpm throttle response to beat towards source in dry comfort.
Some just sit here bored.

A problem with battery to battery is a load whilst ashore on an 'intelligent' charger. AI ain't biological, charger will be confused and risk of fire on boat ain't worth risk.
Plug in doesn't load battery unless inverter in use.

But underway, although would just be a trickle, inverter would need to be big enough to cover that.
I'm out of ideas.

Just reminding you of charging risk from battery to battery if combined with your'intelligent'charger
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Old 17-06-2021, 08:06   #15
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Re: Complicated charging 12V/24V/220V

Let me just summarize what we discussed so far. Generator starting battery gets charged from generator, fine. Thruster batteries get charged from a dc-dc charger to be acquired, fine. Now, the main point in terms of best practice:

1. 24V alternators charge house and starting 24V banks. It will be best if both alternators charge both banks, which means I need an ACR.

2. 24V alternators charge house and starting 24V banks through 3-stage voltage regulators - I think this is best practice, it means I need two voltage regulators and one ACR and some work on modifying the alternators.

3. 24V alternators charge the house batteries only. An inverter is connected to the house batteries as normal. The 220V battery charger is connected to house and starting batteries as normal. When underway, I switch on the inverter and the 220V battery charger. Provided that the alternators generate more current than what the boat consumes, the remaining power will be used to charge both battery banks efficiently.

The boat consums around 15A @ 24V on the average. The two 120A alternators will produce probably 1/3 their rating. I will still have plenty of power to raise the voltage to 28.8V and properly charge the 24V batteries. All I need is a 1500W sine inverter (the charger is 24V @ 50A).

I tend to think that option 2 is best but I fail to see the problem with option 3.

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