Electrikery

[Plato 13]

Hi,

I must admit to electrikery not being my strongest subject

Recently I replaced the House battery with a larger one (85 to 105ah)

I carefully photographed all the wires, tied the common ones together, and then connected the new battery exactly the same way as the old one.

Only trouble now is that the new one won't charge as it did in the old installation.

I can get the new house battery to charge if I connect it in parallel with the starter battery (jump lead to +ve posts)

 

I have two independent battery switches and can't link in parallel in case of an emergency (I have jump cables on board just in case, but far from ideal)

I therefore want to provide a fixed parallel battery switch, which will also be a hack for charging as I simply can't find the problem.

 

Attached is my understanding of the boat's wiring, and in blue the proposed parallel switch.

 

Please can someone who knows more about this than I, look it over and advise if there are in errors in my understanding or thinking

And maybe comment on why the new battery won't charge as in the past.

 

All comments will be most appreciated!

Boat wiring diagram.pdf

[Crazyhorse 47]

House battery wont charge until the switch board supply master is on or the emergency parallel switch....or both.

[mattm 106]

I guess your understanding of things is a little off, or your boat has strange wiring. According to your diagram, the switch panel is fed off the alternator, which has a permanent connection to your start battery? That would mean you can’t switch power to the switch panel off, and that your house loads always draw off either both house and start, or just start, depending on the switches. Not right.

[Plato 13]

Thanks Matt M,

So it seems like the alternator is incorrectly connected - and I will check more carefully.

In this circuit, should the alternator be connected to the battery side of the switch, or the other (lets say functional) side of the switches?

But yes - Its not right

[Island Time 1,293]

Sorry guys I don't agree with that. The batteries should go to a fuse, then a switch. Many engines are now supplied with alt output directly to starter terminal.

Yes, if you switch off the battery whilst engine is running it will blow alt diodes. Don't do it.

However if the alt goes to the batt side of the switch, and it has an internal short, there will be an electrical fire that you can't stop. You must be able to turn off the battery!

Battery fusing (except start batt, which is only recomended) is required in the current electrical regs. Switches are required on all batt banks.

[Beccara 25]

Yeah I'm with IT here, MRBF at the battery terminal and alt to some form of a disconnect switch. any cable or internal fault would cause a fire. If you don't like the idea of a starter fuse blowing then put a bypass switch in. Even a small modern lead battery can chuck out 500-600-700+ amps.

 

Plato whereabouts are you located? 

[Beccara 25]

Starters have a relay close to the battery which limits the ability for a cable fault to when it's starting. A starter on a boat without a fuse/switch/relay would be able to fault at any time.

 

edit:// Slightly false information, Starter relays can be on either + or - side of the starter so may or may not offer protection for a cable fault however would offer protection from an internal fault in the starter

[marinheiro 364]

Fuses on the Start (and other high load batteries) can be covered using one of these (if space is tight)

https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

I have them on my Start and Winch battery with 250amp fuses

House battery is better with a Class T fuse

[Plato 13]

Hi Beccara I'm moored at Westhaven.

(This is getting really confusing)

[Plato 13]

Thanks everyone for your input.

I will need to quietly sit down and synthesise all the points made, and workout an upgrade that will provide a safer and more efficient installation.

The big take away, no matter what else I do, is to fit some fuses!

[Island Time 1,293]

Indeed. Fuses can be the type that go on the batt terminals (easy!!) or a couple of others (eg ANL) but whatever they use, they MUST be IP rated (Ignition Protected), so they cant cause an explosion if the fuse blows in an explosive atmosphere (battery gassing etc).

 

[Crazyhorse 47]

I put a 200amp ANL fuse in line with a direct link from alternator to house batteries. As IT said, these fuses are OK for use in a flammable situation. Incidentally, this is in parallel with the alternator output going to the starter motor which of course is in line with the start battery but it is connected to the battery side of the starter solenoid so remains live. Designed that way. I would suggest you consider using grunty circuit breakers for essential items like coms, winch etc. Stay with tye current rating for the gear you are protecting! Fuses can over time suffer from "sagging", sudden surges that are too quick to pop the fuse but actually weaken the conductor, can take years, then just as you grab the Mic to warn someone...they pop!

[Farrari 4]

Aside from the fusing issue, you may want to think about using a Voltage Sensitive Relay (VSR) between your start and house batteries instead of the proposed manual switch.  You ought to disconnect the switchboard from the ALT otherwise you are bypassing the VSR when you have both red switches engaged and risk running the start battery flat as the house battery is drained.  If your cabling on the red circuit is of insufficient size you may also risk a fire.

 

If finances allow you should also think about installing a smart charger otherwise it is going to take a month of Sundays to reach full charge on your batteries.  The end result probably being you won't achieve full charge so A/ you won't maximize the capacity use and B/ you will reduce the life span of the batteries.

[Island Time 1,293]

I was going to post one of my installations circuits - but that one is fine. Only difference I do is I fuse the batts first, before the switch. That way if ANYTHING on the circuit goes, including the switch, you are protected. He's done that on the start bank, but not the house.

Many don't fuse the starter circuit, but I do. Use the right fuses, and you'll be fine.

Oh, and use proper marine certified cable. Do proper voltage drop calcs, and use the right size cable. Use quality terminals and crimping tools. 

Most people don't have the gear (especially for battery cables), and prefer to have a professional do the design and install. It can be done DIY, but requires a bit of knowledge or learning to attain that knowledge first.

[Dtwo 157]

(This is getting really confusing)

 

KISS principle applies here.  I am in the same group as you - working out where these invisible electrons are whizzing around is a big challenge for me.  Simplicity is preferable over complexity as it enables you to understand what is going on - and adjust your "management" to suit.  As in, if you know you need to turn on Switch A to do something, then you know it.

 

Personally, Voltage Sensitive Relays (as an example) introduce a level of complexity that I am not comfortable with. And when they fail, trying to work out how to turn the lights on when the kids are screaming and the wife has lemon lips is more stress than I need.

 

So, my advice is - make it as simple as possible, even if that means you miss out on the latest and greatest technology.

[Farrari 4]

In its most basic form a VSR is a very simple device, a smart charger perhaps not quite so much.  Think of a VSR as a smart relay that closes when the start battery reaches a predefined voltage i.e. when it's charged. This saves the operator having to operate a manual switch when they think the start battery is charged and then disconnect it again when the motor is turned off.

 

Many have manual override so if you suspect there are issues with the VSR, it can by bypassed and it will act as a manual switch.

[Plato 13]

Hi Lateral

In your circuit, where is the start bettery?

Or is it the reserve bank(125ah) in the bottom right corner?