dual battery solar charging and 1 2 both switch

[PaulRainbow]

Just sizing the cable for installing the Victron Energy Cyrix-ct 12/24V-120A intelligent battery combiner.
My alternator is rated for 40amps which I believe is what you base it on. The cable runs would be pretty short so I am thinking 6 or 8 AWG, which is 13.3 or 8.37 mm squared. The third little wire to the starter negative I'm not sure how to determine but in one post somewhere I read 1 mm squared (AWG 17). Feel free to confirm anyone?

10mm sq for the cables to the batteries, 1mm or 1.5mm for the negative. Forget about the start assist wire, the 1-2-B takes care of that. Don't forget to fuse at least one of the 10mm cables (both if any chance of shorting the cable). Fit as close to the batteries as possible.

 

[vyv_cox]

Why would you want to add a VSR when you already have a dual bank controller? It may not be as sophisticated as a VSR (not sure if that is true) but it basically does exactly the same thing.

I doubt very much that using the dual bank controller on 'both' will do it any harm. It is not often that I do it but certainly not unknown. I have had two controllers, one a very old one by SunWare with mechanical switching and my current one by SunWorks that I have owned for many years, 15 I think. No problems with them, other than the switches in the SunWare.

 

[FairweatherDave]

Quote "Originally Posted by halcyon
Should add 13.2-13.5 volt is no where near full, to fully charge a flooded lead acid battery you need 15.4/15.6 volt.
Once an alternator starts to regulate the voltage, say 13.6 volt, charge current will fall to a very low amperage, and will not recharge the battery any further."
Brian

Quote"Exactly my long term issue. I have capacity for all my needs and make enough through involuntary engine use but if I had a few days in a row where I was able to sail all day then the hour or so in and out of harbour would not be enough at the 1 or 2 amps I'm getting in at 13.3 volts."
Rupert

I don't understand this. Is the implication that if you fit a VSR you significantly slow down the final bit of fully charging the batteries? Or is it simply about alternators and significantly discharging and recharging batteries.

 

[Stemar]

For what it's worth, I have solar panels with a twin battery regulator. It's set up so it charges the engine battery first, then turns its attention to the domestic one. The reason for this is that lights being as bit faint is a nuisance. Not being able to start the engine is, potentially, a disaster on a boat that is less than greyhound-like under sail. The fused outputs go directly to each battery. The 40w of panels provide enough power to replace what we use at anchor during the summer and replace what I use over a weekend working on the boat by the next weekend in winter.I have a cheap split charging relay, the cubical type that used to be used as a headlamp relay in cars. It's activated from the alternator side of the ignition warning light circuit. This is at 0 volts, no matter what the state of the batteries or the output from the solar panels, until the alternator is spinning fast enough to provide a few volts, so no risk of the panels upsetting it. It draws no power until it's activated, when the drawer is irrelevant. The alternator is wired directly to the engine battery. I also have a 1-2-both switch, which only to decide which battery is going to be used to start the engine. It's off when I leave the boat, on 1 when I'm on board, to use the engine battery but can be switched to 2 (domestic) or both if necessary. It never has yet. This has proved to be a robust, easily managed system over the past several years, was simple to install at minimal cost (apart from the panels) and I recommend it to owners of small boats with modest electrical needs.

 

[FairweatherDave]

Why would you want to add a VSR when you already have a dual bank controller? It may not be as sophisticated as a VSR (not sure if that is true) but it basically does exactly the same thing.

I doubt very much that using the dual bank controller on 'both' will do it any harm. It is not often that I do it but certainly not unknown. I have had two controllers, one a very old one by SunWare with mechanical switching and my current one by SunWorks that I have owned for many years, 15 I think. No problems with them, other than the switches in the SunWare.

Thanks Vyv. I'm simply going off the installation manual which stipulates independent isolated batteries. I have asked the supplier by e mail about the 1 2 both switch but I have not heard back, which is frustrating.

 

[PaulRainbow]

I don't understand this. Is the implication that if you fit a VSR you significantly slow down the final bit of fully charging the batteries? Or is it simply about alternators and significantly discharging and recharging batteries.

It's about Ruperts alternator not putting out enough volts. Nothing to do with VSRs as such.

 

[PaulRainbow]

Why would you want to add a VSR when you already have a dual bank controller? It may not be as sophisticated as a VSR (not sure if that is true) but it basically does exactly the same thing.

Not quite. The VSR ensures that all batteries get charged by the solar controller or the alternator, no matter where the switch is set. It also means no fiddling with the switch to get different batteries charged. It also means no chance of any issues with the solar controller if the switch gets left on "Both" (although it should never be there in the first place).

 

[vyv_cox]

Not quite. The VSR ensures that all batteries get charged by the solar controller or the alternator, no matter where the switch is set. It also means no fiddling with the switch to get different batteries charged. It also means no chance of any issues with the solar controller if the switch gets left on "Both" (although it should never be there in the first place).

But that is exactly what the dual bank controller does.

 

[Buck Turgidson]

But that is exactly what the dual bank controller does.

The VSR will connect both banks if it sees 13.8V on either side for 4 seconds or 13.0V on either side for 10 minutes. It will remain connected until it sees 12.8V for 10 minutes or 11.8V for 4 seconds.

So there is no need to switch the 1,2,B to B except to start the engine in emergency.
Just leave it at 1.

When there is solar the batteries will parallel. When the engine is running the batteries will parallel, when shore power charger is used the batteries will parallel. They will remain paralleled until no charge is available on either side and the voltage drops to 12.8 at which point they will isolate. If they are paralleled and something drags the voltage down rapidly to 11.8v they will split.

There really is no need for the 1,2,B as the VSR has an emergency parallel function via a momentary switch which can be wired to the unit. It will parallel the batteries for 30seconds. This is the equivalent to Both for start.

My only gripe is it would appear to be best suited to two batteries that are well matched as for example if you have a massive fully charged house bank and a tiny well discharged starter battery there could be quite a rush of current when they first connect which may or may not be a good thing.

 

[Poey50]

But that is exactly what the dual bank controller does.

I connected my dual output PMW controller (which looks like a different badged version of the OPs) direct to both batteries so they charged with the switch off. Switching to both turns them into one big battery and, as previously said, didn't cause any problem with the controller that I was aware of. (But I take all Paul's points about the potential problems of paralleling.)

The truth is, surely, that there is a variety of approaches to this issue. I had a poor output alternator so went with another solution which is the Sterling Alternator to Battery Charger giving a boost charge to the house bank and an unboosted charge to the engine battery.

(Although I should add that at the same time I added a dedicated engine battery, combined the other batteries for form a house bank and moved to the three switch separate circuit system which for a turnip-head like mine is the best defence against forgetting to fiddle with the 1, 2, both. I kept the same controller which then charged both fully independent house and engine batteries.)

 

[PaulRainbow]

But that is exactly what the dual bank controller does.

Without the VSR your controller will charge both batteries, nothing more. See below for what the VSR gives you.

The VSR will connect both banks if it sees 13.8V on either side for 4 seconds or 13.0V on either side for 10 minutes. It will remain connected until it sees 12.8V for 10 minutes or 11.8V for 4 seconds.

So there is no need to switch the 1,2,B to B except to start the engine in emergency.
Just leave it at 1.

When there is solar the batteries will parallel. When the engine is running the batteries will parallel, when shore power charger is used the batteries will parallel. They will remain paralleled until no charge is available on either side and the voltage drops to 12.8 at which point they will isolate. If they are paralleled and something drags the voltage down rapidly to 11.8v they will split.

Thanks, saved me some typing :encouragement:

There really is no need for the 1,2,B as the VSR has an emergency parallel function via a momentary switch which can be wired to the unit. It will parallel the batteries for 30seconds. This is the equivalent to Both for start.

I'm not a fan of the "Start assist" function on the Victron VSRs, i never connect it. If the engine battery is flat, it's a big ask of the relatively small gauge VSR wiring and indeed the VSR itself to expect it to start the engine. Also, if the engine battery fails altogether there is no easy way to keep the engine running. My preference is to always fit an emergency switch.