Split charge relay problems

[Dave_Beard]

Hi all my current split charge system for my four battery banks is a 90amp split charge relay 1in 3 out with the 4th bank being taken from one out to a conventional split charge relay also my solar panels are connected via controller directly to the house battery bank. I want to upgrade the whole charging system and my idea is to replace the scr with 3 vsr's and take the alternator, mains charger and solar charge all to the start battery and then use first vsr between start and house the second vsr between house and stern and the 3rd vsr between stern and bow does anyone know if there is a better way to wire this system up.

[Robbo]

How come 4 banks? Starter, house, bow? It's best to have one big bank than multiple small ones (apart from starter, bow, house which are separate due to location or function).

 

All charging devices should go to the main house bank as this will be the one that will be the most discharged.

 

I have 3 banks and two VSR's, I use two bus bars, one positive and one negative that everything is connected to for ease of cabling. I'll dig my wiring diagram out.

Edited January 29, 2017 by Robbo

[Robbo]

This is how mine is wired up

 

I've used blue sea VSR's and terminal fuses.

Edited January 29, 2017 by Robbo

[Dave_Beard]

I have four batteries in the centre of boat 1 start and 3 house then two batteries at the stern for fridge and Inverter and one in the bow for Thruster

[WotEver]

... does anyone know if there is a better way to wire this system up.

The charging sources should all go to the house bank.

 

Then I would suggest a VSR to the start batt and a couple of VSRs to Bow and Stern from the Start batt. It sounds good to me.

 

So, three VSRs, with the house bank taking the heavy charge current direct and the start batt next priority, followed by Bow & Stern.

[Robbo]

The charging sources should all go to the house bank.

Then I would suggest a VSR to the start batt and a couple of VSRs to Bow and Stern from the Start batt. It sounds good to me.

So, three VSRs, with the house bank taking the heavy charge current direct and the start batt next priority, followed by Bow & Stern.

Sounds bad to me, you have to go through two VSR's to charge a heavily (potentially) discharged stern battery, connect the VSR's and charging devices too one bus bar as well as a direct connect to the main house bank as it will reduce connections and voltage drop. Edited January 29, 2017 by Robbo

[Dave_Beard]

Hi thanks for suggestions here is my wiring proposal

 

[Robbo]

Hi thanks for suggestions here is my wiring proposal

 

 

Split Charge Wiring.jpg

You have everything connected to the starter, this is the battery that doesn't get discharged, the others do. The chargers should be connected to the bank that gets discharged the most.

[Dave_Beard]

Hi Robbo i see your point and i will change the plan to connect all charge sources to the house do you think any fuses should go in any where on this charge circuit?

[Robbo]

Hi Robbo i see your point and i will change the plan to connect all charge sources to the house do you think any fuses should go in any where on this charge circuit?

I would use bus bars as well as you will have a lot of cables connected to the house bank. Yes all connections from the batteries will need fusing, if you look at my diagram I have a fuse from the battery for the cable leading to the busbar, this protects all cables from this busbar. I've used blue sea terminal fuses, as these are fuses that sit on top of the battery terminal so reduce the cabling further.

[Robbo]

Excuse the quality...

 

[Dave_Beard]

yeah good ideas thanks i like those fuses that sit on the bat terms great idea what rating should i use

and also i am warming to the busbar to as it cuts down on a lot of wires i am also thinking about cable sizes do you think 16mm2 is overkill when at least one battery bank is about 15ft away?

[Robbo]

yeah good ideas thanks i like those fuses that sit on the bat terms great idea what rating should i use

and also i am warming to the busbar to as it cuts down on a lot of wires i am also thinking about cable sizes do you think 16mm2 is overkill when at least one battery bank is about 15ft away?

With fuses you need to fuse for minimum size cable for that circuit. However you have 3 charging sources so if we add them all up we could have quite a few amps in total in use at the same time.

 

Alternator, solar and charger may go over the max amount of one fuse and for the size of the VSR, etc. Instead of a bus bar, something like this may be more appropriate... https://www.bluesea.com/products/7748/SafetyHub_150_Fuse_Block

 

16mm2 may be too small, I have 40mm2 running to my bow batteries.

Edited January 29, 2017 by Robbo

[jonathanA]

Others will know definitely but I think the BSS mandates 25mm

 

Haven't done the sums but 16mm feels a bit light. I'm a believer in the KISS principle and this seems complex but in fairness you may be proposing the simplest solution it just seems to need a lot of 'stuff'

[Dave_Beard]

Its a bit weid the size of cable 25mm that seems right for the voltage and current but the existing cable between the fitted scr and batteries is only around 2.5 to 4.00mm max their must be a lot of voltage drop. For that matter my last boat only had thin 4.0mm cables between splitter and battery banks odd

[Dave_Beard]

Thanks for all the input i will use 35mm to 50mm cables and connect my charging sources to the house bank.

 

Regards

 

Dave Beard

[Dave_Beard]

Hi all i just found this which might be of interest

 

TSB-1001_wire_size.pdf

[WotEver]

Sounds bad to me, you have to go through two VSR's to charge a heavily (potentially) discharged stern battery, connect the VSR's and charging devices too one bus bar as well as a direct connect to the main house bank as it will reduce connections and voltage drop.

Yup, move the stern and bow VSRs from starter to main. That'd be neater. Agreed.

[Robbo]

I have four batteries in the centre of boat 1 start and 3 house then two batteries at the stern for fridge and Inverter and one in the bow for Thruster

 

 

As it looks like you will be (re)running wires from centre to stern/bow it may be better to review the locations of the batteries. The stern batteries will be fairly well under charged due to the voltage drop. Ideally I would move the stern batteries (and inverter) to the centre and use one house bank. If this is impractical another option would be to use separate chargers on the remote banks. If your on shore power mains alot then this would be a good option.

[WotEver]

With fuses you need to fuse for minimum size cable for that circuit. However you have 3 charging sources so if we add them all up we could have quite a few amps in total in use at the same time.

 

Alternator, solar and charger may go over the max amount of one fuse and for the size of the VSR, etc. Instead of a bus bar, something like this may be more appropriate... https://www.bluesea.com/products/7748/SafetyHub_150_Fuse_Block

 

16mm2 may be too small, I have 40mm2 running to my bow batteries.

The fuses shown on your diagram protect the cables from each battery and so their sizes may be determined by the maximum charging current that the Battery may demand. Therefore if the Bow batteries are say 220Ah then the maximum current they could demand even if completely flat is 200A.

 

The maximum available charging current becomes irrelevant, the batteries determine the demand not the charge source.

 

If the cables are too big and allow for a minimal voltage drop then heavily discharged batteries will cause the VSRs to drop back out as the 'remote' batteries drag down the house battery voltage.

 

To do this properly I think we need to know cable lengths and the sizes of the remote batteries.

 

 

As it looks like you will be (re)running wires from centre to stern/bow it may be better to review the locations of the batteries. The stern batteries will be fairly well under charged due to the voltage drop. Ideally I would move the stern batteries (and inverter) to the centre and use one house bank. If this is impractical another option would be to use separate chargers on the remote banks. If your on shore power mains alot then this would be a good option.

Agreed. It's messy right now and introduces many complications as my above post highlights.