1,2 Both Switch - When on Both do the 2 batteries even out on charge?

[Bru]

But with what I'm proposing I wouldn't be fiddling with the switch either. I would only use it in an emergency and then it would give me the easy option to isolate or link the banks.

I realise I am probably missing something...

____________________

'Fraid so, the main thing being that with nothing charging your emergency starter battery, when you need it it will almost certainly not have enough charge to be of any use

All lead acid batteries self discharge over time.

 

[lw395]

"Please feel free to play the Devils advocate..."


Well not really, but after a wrestle with my memory I have just recalled how my set up works. I have something v similar to what you propose. But:

- I can start the engine on either battery or both. This will then charge either one or both.

- The house battery is on a separate isolation switch to services. The start battery is not wired to power the boat, it can't without jump leads.

- The house battery is charged additionally by a windgen with overcharge protection.

- The house battery is monitored by a Nasa BM1 and the start battery voltage can also be checked.

When I first had the boat it was more sophisticated.
In practice, with the revised system, all I do is charge the start battery now and again from the engine and keep an eye on things. It just sits there doing very little till the day I flatten the service battery totally.
The key attraction to an electrical num-nuts is that I can understand it and if it goes wrong it will be easy to deduce why.

That is a sound approach.
I have spent some amusing time trying to diagnose 'superior' systems over the phone, when the owner doesn't really know what they've got, or how it's been set up.
It's all very well for those of us with some knowledge, but the acid test is 'can I explain this to SWMBO?'

 

[RichardS]

Also not so, when the sense side of the VSR reached the preset voltage, the batteries will be paralleled until the voltage drops below the preset. Charging and (which most people forget) discharging will then happen across all the batteries as if they are one bank

That's interesting as my system uses twin solenoids which appear to work in this way rather than VSRs and I've always wondered whether my system is less effective because of it, although it seems to work perfectly well.

Basically, I have twin engines each with its own alternator. The house battery bank is connected to one side of both solenoids whilst the starter battery is connected to the other side of it's own solenoid along with the charging output from the alternator from that engine. When the engine is not running the heavy duty contacts in the solenoid are disconnected and the house bank is isolated from both of the starter batteries which are isolated from each other.

When one engine is started the starter battery for that engine begins to charge immediately and the solenoid coil is then activated by the alternator current and the charging current is then directed to the house bank paralled with that engine's starter battery.

When both engines are started, each alternator charges it's own starter battery and both alternators are paralled to charge the house bank.

As far as I can see there is no "voltage sensing" in my system (ignoring the regulator in the alternators) other than the fact that the solenoid "senses" that the alternator is producing an output and closes the heavy duty contacts. If this is, more or less, the same as a VSR, why don't other boats use it?

Richard

 

[PaulRainbow]

Also if my vsr were to fail I have an effective manual override with a switch.

You will have with separate switches.

When we did a season around the Hebrides in the Jeanneau my (newish) house bank died and I had to keep the engine on if I wanted instruments on the way back.

I had the same thing happen, also on a Jeanneau. Luckily i had already replaced the Jeanneau switches, so i didn't have you problem.

For anyone with a Jeanneau that is fitted with dualbattery banks, controlled by two red and one black isolator switch, there is a very simple upgrade. Remove the two negative cables from the black switch and connect them together. I good sized bolt will suffice, well insulated, not insulation tape, fix a piece of rubber hose over the join. Then connect a new cable from the engine switch load terminal to one terminal on the black switch and another new cable from the load on the domestic switch to the other terminal on the black switch. Mark the black switch "emergency", or whatever takes your fancy. Painting it yellow might be nice.

If you had done this with the Jeanneau Shuan you would have just isolated the faulty house bank and turned the yellow switch on. Job done.

Paul Rainbow. An independent thinker but fails to back up his opinions with reasoned evidence. 3/10 see me after class.

Apologies for assuming you would have read the whole thread, where i explained my thinking in more detail

I'm trying to be be able to isolate either bank should they fail. My thinking is that adding a switch in the way I describe gives me something "extra" to the standard way boat builders do it now. (Which has let me down once)

But I am, as Noddy says, all ears...

_____________________________

Your idea is certainly better than nothing. But as you will have everything you need to make an even better system, apart from the switch, it makes sense to buy the alternative arrangement. IMO.

Arrive at boat for the weekend, switch domestic switch on. Domestic circuits live, engine still isolated. Decide to do some work on the engine, can still leave domestics on, no worries about working on the engine as it is isolated.

Need to use engine, switch engine bank on. Engine is now working, battery is still separate from domestics so cannot be flattened.

A battery bank fails. Isolate the faulty bank by switching it off. Switch the emergency switch on. Domestics and engine now powered by the good bank.

All switches clearly labeled, SWMBO and even the daftest crew member can't get it wrong.

 

[PaulRainbow]

As far as I can see there is no "voltage sensing" in my system (ignoring the regulator in the alternators) other than the fact that the solenoid "senses" that the alternator is producing an output and closes the heavy duty contacts. If this is, more or less, the same as a VSR, why don't other boats use it?

Richard

Yours is charge sensing, same as older caravan systems used to be. It's one step up from wiring the solenoids to the ignition switches.

A VSR would be better in a couple of scenarios. In the event of a low engine battery it will prioritise that battery before charging the domestics, to a degree. In the event of a problem with the domestics, where a battery had failed it might be possible to discharge the engine batteries as the solenoid will not disengage, a good VSR should.

 

[BabaYaga]

As far as I can see there is no "voltage sensing" in my system (ignoring the regulator in the alternators) other than the fact that the solenoid "senses" that the alternator is producing an output and closes the heavy duty contacts. If this is, more or less, the same as a VSR, why don't other boats use it?
Richard

I do, on a single engine charging system, and I wonder the same.
In my view, a heavy duty relay (or solenoid) that senses alternator D+ output, paralleling the batteries, gives a system that is robust and predictable and with very few drawbacks.
Not saying that a VSR cannot work well, I'm sure it can, but judging from the many threads about VSR chatter and problems relating to multiple charging sources, it seems to me the 'dumb relay' route should be given more consideration, instead of the 'fit a VSR and everything will fine' kind of advice often given here.

Yours is charge sensing, same as older caravan systems used to be. It's one step up from wiring the solenoids to the ignition switches.
A VSR would be better in a couple of scenarios. In the event of a low engine battery it will prioritise that battery before charging the domestics, to a degree. In the event of a problem with the domestics, where a battery had failed it might be possible to discharge the engine batteries as the solenoid will not disengage, a good VSR should.

In the first scenario, a low engine battery will most likely be known to the boat owner (too much unsuccessful cranking), so will therefore allow the engine to run for a while in order for the batteries to charge up. But yes, perhaps this is a small drawback.
In the second, would a failed domestic battery really be able to discharge the starter battery faster than the alternator could charge it? Seems a very remote possibility to me.

Are there no other (better) selling points for the VSR over the dumb relay?

 

[ghostlymoron]

It seems to me that there's a lot to be said for a low loss diode setup as the batteries are never in parallel (as far as drawdown is concerned). The drawbacks are chatter and not fully charging the starter battery before putting charge into the house.
I speak as one who has in the past removed diodes and replaced with a BEP VSR.
I believe modern VSRs are chatterproofed. And a dual sensing would charge both batteries from say a solar panel.

 

[PaulRainbow]

I do, on a single engine charging system, and I wonder the same.
In my view, a heavy duty relay (or solenoid) that senses alternator D+ output, paralleling the batteries, gives a system that is robust and predictable and with very few drawbacks.
Not saying that a VSR cannot work well, I'm sure it can, but judging from the many threads about VSR chatter and problems relating to multiple charging sources, it seems to me the 'dumb relay' route should be given more consideration, instead of the 'fit a VSR and everything will fine' kind of advice often given here.



In the first scenario, a low engine battery will most likely be known to the boat owner (too much unsuccessful cranking), so will therefore allow the engine to run for a while in order for the batteries to charge up. But yes, perhaps this is a small drawback.
In the second, would a failed domestic battery really be able to discharge the starter battery faster than the alternator could charge it? Seems a very remote possibility to me.

Are there no other (better) selling points for the VSR over the dumb relay?

Yes, the answer to which addresses your comments about chatter and multiple charging inputs too. Reports of chatter relate to older or cheaper (rubbish) VSRs. Newer/better VSRs don't suffer chatter. I have a Victron Cyrix dual sensing VSR, which has some microprocessor control. It doesn't chatter. It also allows me to connect the alternator to the engine bank and the solar controller to the domestic bank. That allows the alternator to charge both banks with the engine running and the solar panels to charge the engine battery when i'm in the marina.

It is possible for a failed battery to discharge faster than the alternator can charge. It is also possible for a failed alternator to discharge a battery in seconds. I have seen both, more than once. A couple of weeks ago I was called out to a Volvo with a totally flat battery that stopped on the side of the road. I connected a jump pack, which wouldn't even illuminate the dash lights and after less than a minute, the jump pack was flat.

I am not saying that a VSR is the "be all and end all" for every situation, but for most smallish boats it does provide a reasonable and cost effective solution.

 

[PaulRainbow]

It seems to me that there's a lot to be said for a low loss diode setup as the batteries are never in parallel (as far as drawdown is concerned). The drawbacks are chatter and not fully charging the starter battery before putting charge into the house.
I speak as one who has in the past removed diodes and replaced with a BEP VSR.
I believe modern VSRs are chatterproofed. And a dual sensing would charge both batteries from say a solar panel.

Yes to both, if a good quality VSR is used.

 

[BabaYaga]

I have a Victron Cyrix dual sensing VSR, which has some microprocessor control. It doesn't chatter. It also allows me to connect the alternator to the engine bank and the solar controller to the domestic bank. That allows the alternator to charge both banks with the engine running and the solar panels to charge the engine battery when i'm in the marina.

All the above, except the last option, also applies to the dumb relay activated by D+.
The benefit of the engine battery being charged by the solar panels is rather small in my view, how does this need arise?
Furthermore, the VSR not only allows this to happen, it makes it happen, whether desirable or not.
I don't think it is much of a problem with solar, but it could be if a mains charger were left permanently connected. At least this should be considered before installing a VSR, IMHO.

 

[ghostlymoron]

What do you class as a good quality VSR, BEP?

Yes to both, if a good quality VSR is used.

 

[pvb]

I'm increasingly attracted to low-loss isolators rather than VSRs. Solid state, no chatter, no contacts to erode, no current drain.

 

[shaunksb]

Arrive at boat for the weekend, switch domestic switch on. Domestic circuits live, engine still isolated. Decide to do some work on the engine, can still leave domestics on, no worries about working on the engine as it is isolated.

Need to use engine, switch engine bank on. Engine is now working, battery is still separate from domestics so cannot be flattened.

A battery bank fails. Isolate the faulty bank by switching it off. Switch the emergency switch on. Domestics and engine now powered by the good bank.

.

This sounds like the sort of arrangement I'm after.

It's a quick visit to the forum for me now so I will have another read tomorrow to get my head around it.

Never confuse reading the whole thread with understanding the whole thread...

_______________________________

 

[PaulRainbow]

What do you class as a good quality VSR, BEP?

Not sure if things have changed, but the BEP ones were where a lot of the chatter complaints originated. I'd recommend Victron.

 

[PaulRainbow]

All the above, except the last option, also applies to the dumb relay activated by D+.
The benefit of the engine battery being charged by the solar panels is rather small in my view, how does this need arise?
Furthermore, the VSR not only allows this to happen, it makes it happen, whether desirable or not.
I don't think it is much of a problem with solar, but it could be if a mains charger were left permanently connected. At least this should be considered before installing a VSR, IMHO.

I can't think why it would be undesirable to keep the engine battery fully charged. The need arises from the natural tendency of lead acid batteries to self discharge, but this may be small, as you say.

I also don't understand why you think leaving a mains charger permanently connected would cause a problem due to the VSR ?

 

[sailorman]

It seems to me that there's a lot to be said for a low loss diode setup as the batteries are never in parallel (as far as drawdown is concerned). The drawbacks are chatter and not fully charging the starter battery before putting charge into the house.
I speak as one who has in the past removed diodes and replaced with a BEP VSR.
I believe modern VSRs are chatterproofed. And a dual sensing would charge both batteries from say a solar panel.

Or shore charger or any charging source from either direction

 

[BabaYaga]

I can't think why it would be undesirable to keep the engine battery fully charged. The need arises from the natural tendency of lead acid batteries to self discharge, but this may be small, as you say.

I also don't understand why you think leaving a mains charger permanently connected would cause a problem due to the VSR ?

Not saying it is undesirable for the engine battery to be fully charged. But it most often already is, long before connecting to shore power. Then on top of that, having to sit at 14,4V or more (Sterling) all night while the domestic bank charges up will not necessarily do the start battery any good.

May not be harmful either, but my point is to think this through before installing the VSR.

If connected for longer periods much depends on how good the charger is at reducing to float voltage and staying there, despite parallel loads (the main reason for boat owners wanting to be permanently plugged in). Most modern chargers do this well, some older do not. This relates to the VSR in my opinion, as the starter battery is more vulnerable to over charging, being smaller usually and having no loads.

As you say, self discharge of the engine battery could be an issue in the long run, like over winter, and should be taken into consideration. It will vary a lot with battery type.
I think my own view is influenced by having a quite small AGM engine battery. It has very low self discharge but is probably more sensitive to prolonged periods at peak voltage.

 

[sailinglegend420]

Not saying it is undesirable for the engine battery to be fully charged. But it most often already is, long before connecting to shore power. Then on top of that, having to sit at 14,4V or more (Sterling) all night while the domestic bank charges up will not necessarily do the start battery any good.....

Overcharging
It is possible with all these automated systems that the starter battery can be overcharged when paralleled to a large service bank. The starter battery only loses 1-2 Ah to start an engine but the service bank may be depleted by 200-300 Ah, so when they are both being charged the service bank may need 6-10 hours at 14.4 volts before it falls to float mode. The starter battery will be charged very quickly and will also be sitting at 14.4 volts for 6-10 hours, but it may have reached near to 100% charge in a very short time.

Those who sell split charge or battery combiners say this causes no problems because the battery will automatically limit the current that it receives. But overcharging is not too much current, but too much voltage for too long.

So consider when charging only the starter battery just how long the charger would normally stay at absorption voltage before it falls to float. With only 1-2 Ah to replace it will not take very long. That is why a lower float voltage is used to protect batteries from overcharging.

Next consider what happens when a VSR joins the two banks together and the starter is nearly fully charged, but the service bank is heavily depleted. There will be a large discharge of current, maybe 100 amps or more, from the starter to the service bank as the voltages equalize. In this situation the starter bank may have lost more Ah, but it will still not need 6 hours at 14.4 volts before it should be dropped to float voltage. This discharge is also an unnecessary extra load on the starter battery and another good reason why manual switches or automatic battery combiners are not the best solution to split charging.

Service Bank Priority
VSRs and battery combiners must be wired so that the service bank has charging priority. This means all the available charging current is directed to the service battery. All other loads such as an anchor windlass should be wired to the service bank as well. The alternator will then be supplying current immediately to these heavy loads just when they are needed. The starter battery is only then used to start the engine, so it needs to be no larger than is necessary just to crank the engine.

 

[PaulRainbow]

Overcharging
It is possible with all these automated systems that the starter battery can be overcharged when paralleled to a large service bank. The starter battery only loses 1-2 Ah to start an engine but the service bank may be depleted by 200-300 Ah, so when they are both being charged the service bank may need 6-10 hours at 14.4 volts before it falls to float mode. The starter battery will be charged very quickly and will also be sitting at 14.4 volts for 6-10 hours, but it may have reached near to 100% charge in a very short time.

Those who sell split charge or battery combiners say this causes no problems because the battery will automatically limit the current that it receives. But overcharging is not too much current, but too much voltage for too long.

So consider when charging only the starter battery just how long the charger would normally stay at absorption voltage before it falls to float. With only 1-2 Ah to replace it will not take very long. That is why a lower float voltage is used to protect batteries from overcharging.

Next consider what happens when a VSR joins the two banks together and the starter is nearly fully charged, but the service bank is heavily depleted. There will be a large discharge of current, maybe 100 amps or more, from the starter to the service bank as the voltages equalize. In this situation the starter bank may have lost more Ah, but it will still not need 6 hours at 14.4 volts before it should be dropped to float voltage. This discharge is also an unnecessary extra load on the starter battery and another good reason why manual switches or automatic battery combiners are not the best solution to split charging.

Service Bank Priority
VSRs and battery combiners must be wired so that the service bank has charging priority. This means all the available charging current is directed to the service battery. All other loads such as an anchor windlass should be wired to the service bank as well. The alternator will then be supplying current immediately to these heavy loads just when they are needed. The starter battery is only then used to start the engine, so it needs to be no larger than is necessary just to crank the engine.

Very entertaining read, i also enjoyed The Chronicles of Narnia. Whilst an alternative World in the back of my wardrobe might be fun, i don't think any of us would enjoy your alternative World of battery/charging technology.

 

[GHA]

The starter battery will be charged very quickly and will also be sitting at 14.4 volts for 6-10 hours, but it may have reached near to 100% charge in a very short time.

Those who sell split charge or battery combiners say this causes no problems because the battery will automatically limit the current that it receives. But overcharging is not too much current, but too much voltage for too long.

How come it isn't it a problem for millions of cars with alternator regulator set to 14 plus volts?


From Chris Gibson, designer of smartgauge :
http://www.smartgauge.co.uk/controllers.html

Most modern alternators already charge at 14.2, 14.4 or even 14.6 volts. That is how they come from the factory.
For some reason that we cannot fathom there seem to be various people who (for whatever reason) will not accept (or admit) that modern alternators already charge at these higher voltages, as they come from the factory, without any modification. They simply refuse to believe it. All one has to do is measure one with a voltmeter!
Modern batteries do not use excess water if charged at these higher voltages for long periods of time. If they did, then all the truck and car batteries round the world would be dying very quickly because they are charged continuously at higher voltages. They aren't all dying. If anything, they are lasting longer than they used to.
Times have changed. Batteries have changed. Alternators have changed. Alternator controllers are not required on modern systems. They will achieve nothing.