Mix and match chargers

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Graham_Wright

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I have two 50W solar panels with controllers, a Stirling three output mains charger, a 50 amp engine driven alternator, a 130 amp engine driven alternator, a starter battery and two house batteries.

On my camper van, I diode orde (never thought the spell checker would let that go!)a 100 watt solar panel, a mains charger and the engine charger. There is probably a bit of loss through the diodes but it works for me.

On the boat, I think a bit more thought is called for. I guess it is safe to common the outputs but the voltage sensing is more of a concern. The other consideration is to be able to choose sources and destinations. I don't mind a bit of switchery, in fact I love it!

Any sensible suggestions please?


 
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It's hard to say much about the likely outcomes unless you can give a lot of background about the use of the boat.
For instance, having a mains charger is one thing, but do you plug in to shore power every night?
What discharge takes place during a normal week?
How many engine hours do you run each day?

You have all the ingredients for shortening the life of your batteries by overcharging, but it's only going to happen if your regular use looks something like:
Charger fully charges batteries overnight.
Solar then kicks in with two hours of over 14V
Engine then runs for a few hours.
A few loads drop the volts so the solar kicks in again
etc etc
Your batteries could be fully charged and held at boost volts for 8 hours a day.

Most people struggle to overcharge batteries, but it is becoming the most common cause of unreasonably short battery life according to a battery rep I talk to.
Quite common in campervans.
OTOH, the boat I sail on most would probably more likely have the opposite problem, low engine hours, plugs into the shore very rarely, used early and late season when there isn't much sun.
 
lw395 said:
It's hard to say much about the likely outcomes unless you can give a lot of background about the use of the boat.
For instance, having a mains charger is one thing, but do you plug in to shore power every night?
What discharge takes place during a normal week?
How many engine hours do you run each day?

You have all the ingredients for shortening the life of your batteries by overcharging, but it's only going to happen if your regular use looks something like:
Charger fully charges batteries overnight.
Solar then kicks in with two hours of over 14V
Engine then runs for a few hours.
A few loads drop the volts so the solar kicks in again
etc etc
Your batteries could be fully charged and held at boost volts for 8 hours a day.

Most people struggle to overcharge batteries, but it is becoming the most common cause of unreasonably short battery life according to a battery rep I talk to.
Quite common in campervans.
OTOH, the boat I sail on most would probably more likely have the opposite problem, low engine hours, plugs into the shore very rarely, used early and late season when there isn't much sun.
Click to expand...

Good points.

Forget the usage. If I am on board, the Nasa monitors give the states of charge.

I assume the 50 amp alternator is self regulating and will normally only charge the starter battery.

The 130 amp alternator is by Prestolite and the data confusing. It has an adjustable output and also the facility for remote sensing. If, however, it is charging both house batteries by some means, how do I connect the sensing input? Maybe a VSR would be the answer.

The solar should not overcharge according to the controller blurb, but again, it could be charging both batteries. Each panel could be connected to one battery which would make it easier (and could be left like that when not aboard). If the panels are series connected as it recommended from time to time, the original sensing problem reappears.
 
Graham_Wright said:
I have two 50W solar panels with controllers, a Stirling three output mains charger, a 50 amp engine driven alternator, a 130 amp engine driven alternator, a starter battery and two house batteries.
Click to expand...

The obvious choices would be ;

50a alternator to engine battery
130a alternator to domestic bank
Mains charger to both banks

The solar panels should probably both go to the domestic bank, through one controller. Depending on the controller and where the panels are located, in terms of shading, they could be connected in series or parallel.

I would hope the batteries are on separate circuits, with separate switches and an emergency start switch.

Regarding the Prestolite alternator and the domestic bank, it will be charging both batteries as they will be connected in parallel. As far as the sensing goes, the sensing wire goes to the positive terminal of the battery bank, same terminal as you use to connect the load cables to.

Connecting as above, when you are using the engine and the engine battery is fully charged, the potential 50a from that alternator could be going to the domestic bank. In all likelihood you won't see much loss by not using it, as the 130a alternator is probably going to churn more out than the batteries will need. You could use some form of split charging with that alternator, but i see little point with your setup.

The solar panels won't be charging the engine battery, again i don't see this as much of an issue, unless you leave the boat unattended for long periods. If you feel the engine does need a maintenance charge the simplest and cheapest solution would be a 10a solar panel, with no controller.
 
PaulRainbow said:
The obvious choices would be ;

50a alternator to engine battery
130a alternator to domestic bank
Mains charger to both banks
Click to expand...
Mains charger three separate outputs. All batteries are separately switched.[/QUOTE]

The solar panels should probably both go to the domestic bank, through one controller. Depending on the controller and where the panels are located, in terms of shading, they could be connected in series or parallel.

I would hope the batteries are on separate circuits, with separate switches and an emergency start switch.

Regarding the Prestolite alternator and the domestic bank, it will be charging both batteries as they will be connected in parallel.
Click to expand...

My understanding is that that is bad practice as one can take down the other. They are separate and individually selected but can be paralleled.

As far as the sensing goes, the sensing wire goes to the positive terminal of the battery bank, same terminal as you use to connect the load cables to.
Click to expand...

But assuming the batteries are not paralleled, the sensing needs to be correct.

Connecting as above, when you are using the engine and the engine battery is fully charged, the potential 50a from that alternator could be going to the domestic bank. In all likelihood you won't see much loss by not using it, as the 130a alternator is probably going to churn more out than the batteries will need. You could use some form of split charging with that alternator, but i see little point with your setup.
Click to expand...

I like the possibility of redundancy so being able to switch between the 50 and 130 amp alternators would be good (and easy).

The solar panels won't be charging the engine battery, again i don't see this as much of an issue, unless you leave the boat unattended for long periods. If you feel the engine does need a maintenance charge the simplest and cheapest solution would be a 10a solar panel, with no controller.
Click to expand...

If the starter battery does sag after a period, I can use the house batteries.
 
Graham_Wright said:
Mains charger three separate outputs. All batteries are separately switched.

My understanding is that that is bad practice as one can take down the other. They are separate and individually selected but can be paralleled.

But assuming the batteries are not paralleled, the sensing needs to be correct.
Click to expand...

You've created more issues than there need to be by keeping the domestic batteries separated, IMO. If you parallel he two batteries they work as one, the Prestolite will charge them both and the sensing wire goes to the same terminal as the loads connect to.

Keeping them separate Keeping them separate is not necessary and causes complication with the charging, resulting in more equipment being needed and a greater potential for failures and user error. I would keep it simple and connect them in parallel, you have emergency switch if a bank goes down, which is enough.

I like the possibility of redundancy so being able to switch between the 50 and 130 amp alternators would be good (and easy).
Click to expand...

You already have some redundancy. If one alternator stopped charging you can parallel the engine and domestic banks to keep everything charged until you get some where for a fix. There are more complex and/or expensive solutions, such as fitting a split charge system with two inputs and two or three outputs, but that's vastly overkill with what you have. You could simpler split charge systems such as a VSR or low loss splitters, so both alternators charge both banks, but you may run into problems with the battery sensing, so i wouldn't recommend that.

I would have the engine battery on its own circuit, charged by the 50a alternator. The domestic batteries in parallel, charged by the 130a alternator, battery sensed. The solar panels charging the domestic bank, in series or parallel, as i mentioned previously, via one controller. The mains charger will independently charge the two banks. An emergency switch, connected to the load side of the two isolator switches.

This is more redundancy and backup than most single engined yachts have. The switch arrangement allows you to parallel both banks for emergency starting, to isolated a faulty bank and use the good bank for both circuits or to parallel both banks in the event of an alternator failure. Considering how reliable batteries and alternators are, i think that's a very reasonable setup.

Attempts at addition equipment/switching etc just add more failure points for no real good reasons.

If the starter battery does sag after a period, I can use the house batteries.
Click to expand...

Indeed, if it happens regularly fit a 10w solar panel, rather than keep running the battery low and shortening its life.
 
PaulRainbow said:
You've created more issues than there need to be by keeping the domestic batteries separated, IMO. If you parallel he two batteries they work as one, the Prestolite will charge them both and the sensing wire goes to the same terminal as the loads connect to.

Keeping them separate Keeping them separate is not necessary and causes complication with the charging, resulting in more equipment being needed and a greater potential for failures and user error. I would keep it simple and connect them in parallel, you have emergency switch if a bank goes down, which is enough.



You already have some redundancy. If one alternator stopped charging you can parallel the engine and domestic banks to keep everything charged until you get some where for a fix. There are more complex and/or expensive solutions, such as fitting a split charge system with two inputs and two or three outputs, but that's vastly overkill with what you have. You could simpler split charge systems such as a VSR or low loss splitters, so both alternators charge both banks, but you may run into problems with the battery sensing, so i wouldn't recommend that.

I would have the engine battery on its own circuit, charged by the 50a alternator. The domestic batteries in parallel, charged by the 130a alternator, battery sensed. The solar panels charging the domestic bank, in series or parallel, as i mentioned previously, via one controller. The mains charger will independently charge the two banks. An emergency switch, connected to the load side of the two isolator switches.

This is more redundancy and backup than most single engined yachts have. The switch arrangement allows you to parallel both banks for emergency starting, to isolated a faulty bank and use the good bank for both circuits or to parallel both banks in the event of an alternator failure. Considering how reliable batteries and alternators are, i think that's a very reasonable setup.

Attempts at addition equipment/switching etc just add more failure points for no real good reasons.



Indeed, if it happens regularly fit a 10w solar panel, rather than keep running the battery low and shortening its life.
Click to expand...

I chartered in Greece one year - a Feeling 48. One day. the engine failed to start. A quick radio call, and a work boat appeared with two batteries. They replaced both. The theory they offered was that if one dies, it would wreck the other rapidly. I have heard the same elsewhere. You do not subscribe to that view?

I can couple the two house batteries via switching.
 
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Graham_Wright said:
I charted in Greece one year - a Feeling 48. One day. the engine failed to start. A quick radio call, and a work boat appeared with two batteries. They replaced both. The theory they offered was that if one dies, it would wreck the other rapidly. I have heard the same elsewhere. You do not subscribe to that view?

I can couple the two house batteries via switching.
Click to expand...

If the two batteries are in parallel they get equal charge/discharge cycles, so if one dies of old age (won't hold it's charge properly) then it's prudent to change both as the other will be just as old. This isn't something you have to factor too much redundancy into, as you'll get a bit of warning, when your batteries don't last as long as you're used to.

If you suffer a catastrophic failure of one of the batteries it can flatten the other battery, depending on how/why it failed. You are covered here by turning that bank off on the isolator and switching the emergency switch on. You can the identify the affected battery, disconnect its negative cable and turn the good battery back on, turning off the emergency switch. All of this means the 130a alternator will still be charging whichever battery you are left with and the battery sensing will still work.

Having the batteries on separate switches and normally having them in parallel might sound attractive, in as much as you cold separate them without disconnecting cables, but you would have to be mindful of the alternator charging. You can easily be in a situation where the battery that you turned off is the one that the alternator is connected to, so no domestic charging without swapping cables or using the emergency switch to charge from the engine alternator.

It's worth noting that in your situation, with two alternators and no VSR, that whatever happens you must not isolate a bank with the engine running. This also applies to your current setup, you should not change from one domestic battery to the other with the engine running, unless you switch both on first, then turn one off. In other words, the alternator must never be disconnected from its battery whilst it's charging.
 
PaulRainbow said:
It's worth noting that in your situation, with two alternators and no VSR, that whatever happens you must not isolate a bank with the engine running. This also applies to your current setup, you should not change from one domestic battery to the other with the engine running, unless you switch both on first, then turn one off. In other words, the alternator must never be disconnected from its battery whilst it's charging.
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I assume that is to avoid blowing the alternator diodes. A make before break switching system would ensure that.

There must be other methods of protection? Zeners?
 
Graham_Wright said:
I assume that is to avoid blowing the alternator diodes. A make before break switching system would ensure that.

There must be other methods of protection? Zeners?
Click to expand...

Make before break is how modern 1-2-both switches work. Users of those can still blow the diodes by turning the switch to "off", but you don't hear of it happening, so i doubt it's a problem worth worrying about.

Single engined boats commonly only have one alternator, so tend to have split charging systems, which reduce the risk of accidentally turning the isolator off, you would need to turn both isolators off with most systems.

Yours is slightly different, because you'll only have one bank connected to each alternator. So you could turn the domestic bank off with the engine and damage the alternator. That applies equally with having the domestic batteries separate, turn the one off that the alternator is connected to and no diodes. It's probably easier to do if you keep them separate, more switches/options/opportunities to make a mistake and more bits of kit/connections to fail.

You could fit a VSR, which would mean you would have to isolate all of the batteries, but with having two alternators and battery sensing on one, there is the risk of introducing some new problems to a system that doesn't have any. You could fit a VSR and have a changeover switch for the alternators, so you only use one or the other, normally using the 130a one and keeping the 50a one offlne as a backup. That would mean you had to turn all of the isolators off to damage the diodes and you have a spare alternator already to use.

In all honesty though, i think there is a danger here of over complicating things for no good reason.
 
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I have found a fault in my 50 amp alternator which I suspect may be brushes. I'll strip it and find out.

In the process of the investigation, I found a very useful source of information from TB training. However, the circuit diagram illustrated seems to carry an error. http://www.tb-training.co.uk/marinee08.html. The reverse path from the battery seems to be blocked by the diodes.

Or am I being thick?

The alternator also shows a zener diode across the output which is alleged to stop disconnect incidents.
 
Graham_Wright said:
I have found a fault in my 50 amp alternator which I suspect may be brushes. I'll strip it and find out.

In the process of the investigation, I found a very useful source of information from TB training. However, the circuit diagram illustrated seems to carry an error. http://www.tb-training.co.uk/marinee08.html. The reverse path from the battery seems to be blocked by the diodes.

Or am I being thick?

The alternator also shows a zener diode across the output which is alleged to stop disconnect incidents.
Click to expand...

The main -ve diodes are the wrong way around?
 
The diagram is slightly simplified in that the regulator is a 3 terminal device. It needs connections to the aux diodes, ground and field. Field is one side of the rotor, the other side is either ground or the + from the aux diodes as shown.
 
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