Tidy up/improve my electrics

[robtheplod]

Hi All

 

I was on the verge of starting my long delayed solar project when I thought I'd better get to grips with my electrics - finding out where everything connects and where it all goes. The further i looked the more I thought I needed to sort this first before adding anything. I think the battery wiring is a mess, with inline fuses everywhere. The cables are jumbled and the batteries are not wired for maximum efficiency.

 

My plan is to get this tided up by putting a board on the back wall with main mega fuse/ isolator switches and Victron busbars - add a small fusebox for all smaller requirements in the bay such as
Webasto etc. My isolator switches currently are in the cabin so theres a few backwards and forwards of large cables, and i think having the isolators near the batteries is better?  My battery charger and invertor are in the cabin so also just thinking out loud maybe i can run 95mm from the new busbar to another in the cabin for these?  The Victron busbar is rated 1000A so should be happy (its a 2k invertor)?

 

I'd also like to replace the wiring on the batteries - not sure of the internal diameter of the copper, but outside its about a centimetre... I'd probably go nuclear and opt for 95mm on all cable here? Wiring them + and - coming off at opposite ends.

 

My concern is mounting the board - obviously no holes, so thinking, of gluing it to some batons on the metal, but not 100% sure anything would be strong enough??

 

Can anyone comment on the idea and let me know if there is anything else i need to be considering here - im a sucker for planning so anything that you think should go in the mix that would be great, thanks so much!!

 

pics below, hope this gives an idea of what I'm looking to do....

 

 

[Alan de Enfield]

It'd be a good opportunity to get the wiring in compliance with the ISO 10133 "Small craft — Electrical systems — Extra-low-voltage d.c. installations"  requirements (RCD) which state :

 

10.8 No more than four conductors shall be secured to one terminal stud

 

Your middle battery looks to have 5 conductors on the positive terminal.

[robtheplod]

Thanks Alan, yes I'd look to just have the battery interconnect wires on the batteries themselves.....

[Alan de Enfield]

3 minutes ago, robtheplod said:

Thanks Alan, yes I'd look to just have the battery interconnect wires on the batteries themselves.....

 

Don't forget there is a list of 'things' where you are allowed to have them 'live' at all times (ie before the isolators)

eg ; Solar controller, bilge pump, and any electronics or instruments that require a continuous live feed.

[David Mack]

38 minutes ago, robtheplod said:

 

My concern is mounting the board - obviously no holes, so thinking, of gluing it to some batons on the metal, but not 100% sure anything would be strong enough??

I fitted my solar controller to a steel bulkhead by drilling and tapping holes in the steel. I used a 4.5mm drill (should be 4.2/4.3 mm, but it was the closest Screwfix had), then tapped M5 using a cheapie set of taps and dies. Neat and secure solution, and quick and easy to do.

[robtheplod]

28 minutes ago, Alan de Enfield said:

 

Don't forget there is a list of 'things' where you are allowed to have them 'live' at all times (ie before the isolators)

eg ; Solar controller, bilge pump, and any electronics or instruments that require a continuous live feed.

so, if i keep these off the batteries, the order would be coming off the batteries:

 

batteries -> cable to main fuse -> solar connection -> main isolator switch -> off to all other circuits?

 

presume the main fuse always needs to be the first in the line coming off the batteries...

30 minutes ago, David Mack said:

I fitted my solar controller to a steel bulkhead by drilling and tapping holes in the steel. I used a 4.5mm drill (should be 4.2/4.3 mm, but it was the closest Screwfix had), then tapped M5 using a cheapie set of taps and dies. Neat and secure solution, and quick and easy to do.

my concern is this would be close to the waterline .... is this ok?

[David Mack]

38 minutes ago, robtheplod said:

my concern is this would be close to the waterline .... is this ok?

If this a bulkhead then no problem. If it is the hull side, then it would be better to ensure all holes are at least 250mm above water level.

 

[Alan de Enfield]

1 hour ago, robtheplod said:

batteries -> cable to main fuse -> solar connection -> main isolator switch -> off to all other circuits?

 

Yes, but you will also need a correctly sized fuse in your solar (battery to controller) cable

[Sea Dog]

2 hours ago, robtheplod said:

...add a small fusebox for all smaller requirements in the bay such as
Webasto etc.

If Webasto are the same as Eberspacher in this regard, the unit should be connected to the batteries directly (apart from its inline fuse) to keep joints and voltage drop to a minimum. (If you have a battery monitor, the negative should still be connected through the shunt).

 

Worth checking before you route the Webasto through your new fusebox.

[Bee]

I see what you mean. That's an awful lot of cables. If you are thinking of putting buffalo board on that surface and it is the side of the boat I think it would be OK if you used coach bolts with the square bit beneath the domed head filed round, that would leave a nice rounded 'rivet' head on the outside.  Can't see much water getting through that. Probably OK to use a hex bolt but it'll catch on something sooner or later.

[robtheplod]

1 hour ago, Sea Dog said:

If Webasto are the same as Eberspacher in this regard, the unit should be connected to the batteries directly (apart from its inline fuse) to keep joints and voltage drop to a minimum. (If you have a battery monitor, the negative should still be connected through the shunt).

 

Worth checking before you route the Webasto through your new fusebox.

thanks, would this be an issue located close to the batteries via a short 95mm cable?  are they that sensitive?  

[Sea Dog]

8 minutes ago, robtheplod said:

thanks, would this be an issue located close to the batteries via a short 95mm cable?  are they that sensitive?  

My Eber is about the same distance, but still goes direct. Perhaps at that distance it makes little difference, but it also introduces extra joints and they are known to be voltage sensitive so it might be best to stick with Webasto guidance and leave it out of your new fusebox if they say the same as Eberspacher.

[robtheplod]

57 minutes ago, Sea Dog said:

My Eber is about the same distance, but still goes direct. Perhaps at that distance it makes little difference, but it also introduces extra joints and they are known to be voltage sensitive so it might be best to stick with Webasto guidance and leave it out of your new fusebox if they say the same as Eberspacher.

thanks, will look at their recommendations. The cable from the Webasto across the engine to the batteries is coiled up currently so is much longer than it needs to be plus i suspect its not ideal it goes across the engine re vibrations so might look at better route...   this is a bit like dominos!

[Detling]

I mounted a pump and heat exchanger on a plywood panel which was fixed to the side with PU expanding foam as a glue. Sprayed the back of the panel and held it into place with a sissor jack to the top of the engine to keep it firm against the side, for 24 hours. Been there 6 years now never moved at all.  PU glues are very versatile but as this was a flat bit of ply onto a curved surface I needed the foam, which is essentially just a high frothing version of the glue.

[Tracy D'arth]

Could I just ask, have you ever worked with 95mm cable? It is hard work, its bulky, the crimps are massive, and I would doubt that it is necessary unless you have very long cable runs. I have wired dozens of boats with big inverters and rarely used anything over 35mm cable, just occasionally 50mm.

[jonathanA]

2 hours ago, Tracy D'arth said:

Could I just ask, have you ever worked with 95mm cable? It is hard work, its bulky, the crimps are massive, and I would doubt that it is necessary unless you have very long cable runs. I have wired dozens of boats with big inverters and rarely used anything over 35mm cable, just occasionally 50mm.

I wondered the same and he seemed to be implying 95mm to the ebersplutter....

[Chewbacka]

On 27/06/2021 at 13:47, Sea Dog said:

My Eber is about the same distance, but still goes direct. Perhaps at that distance it makes little difference, but it also introduces extra joints and they are known to be voltage sensitive so it might be best to stick with Webasto guidance and leave it out of your new fusebox if they say the same as Eberspacher.

I think the main reason for direct connection for Webasto units is if it is ‘burning’ and you turn off the power the pump stops and the water in the boiler can boil, also when the Webasto shuts down it goes through a shut down sequence which again would not happen if the power were just switched off, so safer to direct connect to reduced ‘accidents’

[robtheplod]

3 hours ago, Tracy D'arth said:

Could I just ask, have you ever worked with 95mm cable? It is hard work, its bulky, the crimps are massive, and I would doubt that it is necessary unless you have very long cable runs. I have wired dozens of boats with big inverters and rarely used anything over 35mm cable, just occasionally 50mm.

No, I haven't Tracy. I'm just looking at the 'ideal' way to do things and so seems prudent to do it thicker than thinner ??? always happy to take advice though so thanks for the query... ...

[Alan de Enfield]

3 minutes ago, robtheplod said:

No, I haven't Tracy. I'm just looking at the 'ideal' way to do things and so seems prudent to do it thicker than thinner ??? always happy to take advice though so thanks for the query... ...

 

35mm2 cable is rated at ~160-200 amps so is OK for ~2kw inverters etc.

95mm2 cable is rated  at ~310-390 amps

 

With an inverter each Kw draws ~ 100 amps from the batteries 

 

It all depends on the temperature rating of the cable as shown in this extract from ISO 10133 Wiring In Small Boats and is the specification used for RCD compliance.

 

 

 

[Tony Brooks]

I would suggest it is more important to work with the cable length and thus volt drop created as well. If you do that the cable should never get hot enough to worry about the temperature rating for most boat wiring. It won't generate enough heat.

[robtheplod]

3 minutes ago, Alan de Enfield said:

 

35mm2 cable is rated at ~160-200 amps so is OK for ~2kw inverters etc.

95mm2 cable is rated  at ~310-390 amps

 

With an inverter each Kw draws ~ 100 amps from the batteries 

 

It all depends on the temperature rating of the cable as shown in this extract from ISO 10133 Wiring In Small Boats and is the specification used for RCD compliance.

 

 

 

Thanks Alan, so, going on this if I wanted a 3kw invertor in the future, 95mm is the way to go?   This is great as this all allows me to build in 'what ifs' to this change....

[Alan de Enfield]

19 minutes ago, robtheplod said:

Thanks Alan, so, going on this if I wanted a 3kw invertor in the future, 95mm is the way to go?   This is great as this all allows me to build in 'what ifs' to this change....

 

Yes.

The RCD requires that all cabling should be rated at 75C minimum (which is the rating for standard PVC cables).

So called HR cables are 105C

 

Once you get up above that you are looking at Rubber or special polymer cables.

 

NOTE - it is the temperature rating of the insulation (not the ambient temperature) that determines the Current rating

 

Ideally use type B cables (commonly called 'welding cables' note number of starnds) for battery connections as they are less rigid and suitable for repeated movements connecting / disconnecting batteries etc.

 

Welding cables can be found at Industrial welding supply companies.

Edited June 28, 2021 by Alan de Enfield

[robtheplod]

1 hour ago, Alan de Enfield said:

 

Yes.

The RCD requires that all cabling should be rated at 75C minimum (which is the rating for standard PVC cables).

So called HR cables are 105C

 

Once you get up above that you are looking at Rubber or special polymer cables.

 

NOTE - it is the temperature rating of the insulation (not the ambient temperature) that determines the Current rating

 

Ideally use type B cables (commonly called 'welding cables' note number of starnds) for battery connections as they are less rigid and suitable for repeated movements connecting / disconnecting batteries etc.

 

Welding cables can be found at Industrial welding supply companies.

I had this in mind Alan:

Oceanflex Tinned PVC Battery Cable - 95mm² 500A | 12 Volt Planet

[Tracy D'arth]

11 minutes ago, robtheplod said:

I had this in mind Alan:

Oceanflex Tinned PVC Battery Cable - 95mm² 500A | 12 Volt Planet

Very expensive place to buy electrical items. The reason is in the "Ocean" part. Anything marine is overpriced.

Welding cables are much cheaper from engineers' suppliers

[Alan de Enfield]

35 minutes ago, robtheplod said:

I had this in mind Alan:

Oceanflex Tinned PVC Battery Cable - 95mm² 500A | 12 Volt Planet

 

Either go to a local welding suppliers or a truck component suppliers

 

I use :

Partic Motor Spares Ltd. - Truck, Bus and Trailer Parts Specialists

 

Give them the size (mm2) and the length and colour and they will cut to length.

 

Tell them what terminals you want and they will fit (properly) your teminals as well.

 

Works out cheaper than 'just the cable' alone from the likes of marine chandleries, or 12v Planet

 

Ocean flex = £29 per metre

Look on ebay = £14 per metre (95mm2 500 A Amps Flexible PVC Battery Welding Cable Black Red 1 - 100M M Lengths | eBay)

 

Try here :

Welding Cable - BS638 Part 4, 0361TQ, EPR, CSP - 16mm to 185mm | Cleveland Cable Company

 

or here :

Black 0361TQ HOFR Cable - Battery cable 95mm2 Single Core (Copy) - Gecko Energy Wholesale

£11.76 + VAT per metre

Edited June 28, 2021 by Alan de Enfield