Installing Battery Chargers - Conection advice needed

[Jokani]

I am tidying up some of my existing 12v wiring, and need some advice

To charge my battery banks, leisure and engine, I have:

1. Alternator
2. 240v
3. Solar

Currently instead of multiple battery terminal connections, both the engine and leisure batteries have just a single negative and positive connection lead, which connects to adjacent negative and positive busbars. Both negative busbars connect to a negative stud, that also connect to the engine block and the anode. Which I presume is OK.

The charger installation diagrams aways show the charger leads connecting directly to the battery terminals.

Am I correct in thinking:

1) Connecting the charger positive leads to an adjacent positive busbar is OK, rather than directly to the terminal?

2) Connecting charger negative leads to an adjacent negative busbar is OK, rather than directly to the terminal, and I only need one negative busbar to share between both leisure and engine batteries?

 

[RichardS]

Thats's exactly what I have .... individual cables to all battery and charger terminals all running to beefy -ve and +ve bus bars. When I connected up the solar controller a few weeks ago I just connected that to the same two bus bars with a common negative for all batteries. It all works well.

Richard

 

[Jokani]

Thanks Richard, I'll get cracking.

 

[PaulRainbow]

Richards method and that which you describe are incorrect, if you have more than one domestic battery.

My negatives are linked between all of the batteries, cables go from the last battery to the engine, bow thruster and to my battery monitor shunt, from the shunt to a negative stud, all of those are 35mm sq. All other negative connections are taken from the stud. The stud is simply an M8 bolt.

Positive cable goes from the engine battery to the engine isolator.

Positive cables from each domestic battery are again linked from battery to battery, with a cable coming from the opposite end of the bank to the negative take off going to the isolator switch. Please yourself where it goes from the isolator switch, it can quite happily got to a busbar from here. I have my mains charger and solar controller connected to the switch supply terminals and cables to the switch panel busbar connected to the load terminal.

If you only have single batteries you can just link the two negatives, take a cable from one battery to the engine and another to a busbar. Positives would be engine battery to isolator, to engine and from domestic battery to isolator, from isolator to busbar. If you have a 1-2-both switch the two positives go to the switch and the common terminal connects to the engine and your busbar. I would not connect engine wiring to busbars in your case.

 

[Playtime]

My negatives are linked between all of the batteries, cables go from the last battery to the engine, bow thruster and to my battery monitor shunt, from the shunt to a negative stud, all of those are 35mm sq. All other negative connections are taken from the stud. The stud is simply an M8 bolt.

If any other negative connections go directly to the negative battery terminal (e.g. engine and bow thruster in your description above) then the current drawn through them will bypass the battery monitor shunt and therefore will not register on the battery monitor display. The battery monitor shunt should be the ONLY connection to the battery negative terminal if you want all current drawn to be registered.

I am also surprised if your engine (starter?) is connected to the domestic battery bank. Maybe I am misunderstanding your description?

 

[Jokani]

Richards method and that which you describe are incorrect, if you have more than one domestic battery.

I do have more than one leisure battery. These are installed as per this diagram as are the isolation switches. Installing the busbars and charges is a job for this weekend.

Is my diagram incorrect?

 

[Playtime]

Your diagram looks pretty good to me.

My only query/suggestion would be the Always On circuit. If you want to leave your fridge 'always on' (maybe only when shore power is connected?) I would suggest that a battery guard is also fitted that will automatically disconnect the fridge if the battery is in danger of being completely discharged (e.g. if the shore power is accidentally disconnected or you leave the fridge on by accident when you leave the boat for a long period).

Always On circuits are normally reserved for things like automatic bilge pumps, stereo radios (to maintain the station memory) or a companionway light that can be easily accessed when first entering the boat.

 

[PaulRainbow]

If any other negative connections go directly to the negative battery terminal (e.g. engine and bow thruster in your description above) then the current drawn through them will bypass the battery monitor shunt and therefore will not register on the battery monitor display. The battery monitor shunt should be the ONLY connection to the battery negative terminal if you want all current drawn to be registered.

I am also surprised if your engine (starter?) is connected to the domestic battery bank. Maybe I am misunderstanding your description?

Read the paragraphs where i describe the positive connections. My starter and windlass (why i typed bow thruster is a mystery, must be losing the plot) are connected to the starter battery, via a separate switch.

The reason the negatives for the starter and windlass do not go through the shunt is because i'm only monitoring the domestic bank.

 

[Jokani]

Your diagram looks pretty good to me.

My only query/suggestion would be the Always On circuit. If you want to leave your fridge 'always on' (maybe only when shore power is connected?) I would suggest that a battery guard is also fitted that will automatically disconnect the fridge if the battery is in danger of being completely discharged (e.g. if the shore power is accidentally disconnected or you leave the fridge on by accident when you leave the boat for a long period).

Always On circuits are normally reserved for things like automatic bilge pumps, stereo radios (to maintain the station memory) or a companionway light that can be easily accessed when first entering the boat.

Point noted, this season I'll be sailing without a fridge, put plan to fit it over the winter. I have already purchased a battery discharge protector, that is adjustable between 10.4 - 13v. My plan is try and have low power fridge & enough solar to be able to keep it on when on a mooring - I might be being optimistic, we'll I'll give it a go and take it from there.

 

[PaulRainbow]

I do have more than one leisure battery. These are installed as per this diagram as are the isolation switches. Installing the busbars and charges is a job for this weekend.

Is my diagram incorrect?

That doesn't quite match what i pictured from your description and is totally different to what Richard describes. Anyway............ i can't see the purpose of having so many isolator switches, you don't need the first one on each circuit, but if they are already there, no point in removing them.

Although you have four batteries, as they are wired partly in series they should be viewed as two batteries for the purpose of this thread. How they are wired is perfectly correct Gary. I had pictured each battery being connected to the busbars as Richard describes.

 

[Playtime]

Understood.. I would suggest setting your battery guard to something like 12.0V initially (with nothing perishable in the fridge!) to get an idea of how quickly it discharges the batteries. Unless you get a very efficient fridge they tend to consume upwards of 30Ah per day. A good solar panel would go someway towards offsetting this but would not reduce it to zero (unless it was exceptional weather or a big panel).

 

[Jokani]

Although you have four batteries, as they are wired partly in series they should be viewed as two batteries for the purpose of this thread. How they are wired is perfectly correct Gary. I had pictured each battery being connected to the busbars as Richard describes.

My fault, I should have posted sufficient detail in the first place. But I have the answers now, so should get this complete ove ther weekend.

Thanks all.

 

[PaulRainbow]

My fault, I should have posted sufficient detail in the first place. But I have the answers now, so should get this complete ove ther weekend.

Thanks all.

How much solar are you planning to install Gary ?

I have a fridge on 24/7, LED lights, electric water pump, laptop and phone charger and have not turned the mains charger on since mid Feb. During that time i have also used the Eberspacher a fair bit, on and off. Everything runs from my solar panels, with lots to spare.

 

[Jokani]

How much solar are you planning to install Gary ?

I have 1 x 40w and 2 x 20w permanent panels, the when at anchor or on my mooring I have an additional 100w.

I did have a cool box that wasn't the most efficient, but I could go for a long weekend, batteries would be down to 50%, but the solar would charge them up in the week, ready for the next Friday, I didn't have the box turned all the way down, and it was on a timer so it switched off overnight. But ater a 2 hour drive to the boat on a Friday a cold beer is one of the highlights of the week.

Planning on installing a built-in fridge this winter, if the panels do not keep up then likley I'll add some wind.

 

[Hadenough]

Understood.. I would suggest setting your battery guard to something like 12.0V initially (with nothing perishable in the fridge!) to get an idea of how quickly it discharges the batteries. Unless you get a very efficient fridge they tend to consume upwards of 30Ah per day. A good solar panel would go someway towards offsetting this but would not reduce it to zero (unless it was exceptional weather or a big panel).

Or a keel cooled fridge, ours draws around 16A.

 

[PaulRainbow]

Or a keel cooled fridge, ours draws around 16A.

My compressor fridge draws 5a including the cooling fan.

 

[PaulRainbow]

I have 1 x 40w and 2 x 20w permanent panels, the when at anchor or on my mooring I have an additional 100w.

I did have a cool box that wasn't the most efficient, but I could go for a long weekend, batteries would be down to 50%, but the solar would charge them up in the week, ready for the next Friday, I didn't have the box turned all the way down, and it was on a timer so it switched off overnight. But ater a 2 hour drive to the boat on a Friday a cold beer is one of the highlights of the week.

Planning on installing a built-in fridge this winter, if the panels do not keep up then likley I'll add some wind.

I have 2x 100w back contact panels on an arch, and a pair of old 30w panels on the coachroof (these are not terribly efficient due to their age and shading issues with the boom/mast). If your panels are modern and don't suffer badly with shading you should be ok i think. My fridge is a built in top loading model, seems to be very well insulated.

 

[RichardS]

Richards method and that which you describe are incorrect, if you have more than one domestic battery.

I disagree, of course.

Individual cables from every +ve battery post to a +ve busbar and from every -ve battery post to a -ve busbar is the optimal solution for every multiple battery installation of more than 2 batteries. However, it is more expensive than the usual cabling solutions so avoided by boat builders. The absolute Rolls Royce solution is to have all the cables exactly the same length but as long as they are a similar length then a Bentley is good enough for most people.

Richard

 

[PaulRainbow]

I disagree, of course.

I wouldn't have expected less of you Richard

Individual cables from every +ve battery post to a +ve busbar and from every -ve battery post to a -ve busbar is the optimal solution for every multiple battery installation of more than 2 batteries. However, it is more expensive than the usual cabling solutions so avoided by boat builders. The absolute Rolls Royce solution is to have all the cables exactly the same length but as long as they are a similar length then a Bentley is good enough for most people.

Richard

Sorry, but this is not the Rolls Royce method. It could be marginally better than how mine are wired, but only if the cables are exactly the same length, otherwise it is considered to be a waste of time and money.

The "Rolls Royce" method is method 4, here : http://www.smartgauge.co.uk/batt_con.html

That said, i should have said "Richards method and that which you describe are unnecessary", rather than "incorrect".

 

[RichardS]

I wouldn't have expected less of you Richard



Sorry, but this is not the Rolls Royce method. It could be marginally better than how mine are wired, but only if the cables are exactly the same length, otherwise it is considered to be a waste of time and money.

The "Rolls Royce" method is method 4, here : http://www.smartgauge.co.uk/batt_con.html

That said, i should have said "Richards method and that which you describe are unnecessary", rather than "incorrect".

Good grief Paul ..... you would have to be out of your mind to use method 4. More like spagetti than serious cabling. As that guy says about my RR method:

It is actually quite simple to achieve but requires two extra interconnectng links and two terminal posts. The difference in results between this and the 2nd example are much smaller than the differences between the 1st and 2nd (which are enormous) but with expensive batteries it might be worth the additional work.

As my batteries cost £700 a pop, this certainly looks like the RR solution to me.

Richard