Victron Intelligent Battery Combiner Cyrix-ct 12/24V-120A VCR

@PaulRainbow Can you help me understand what happens when a 25Ah battery is in parallel with a 200Ah battery and they are both being charged at >13.5V but the 25Ah battery is fully charged and the 200Ah battery still needs charging?
What's happening to the 25Ah battery?
Why isn't it over charged and damaged/over heated etc?
 
tony12345 said:
I'm getting there. Thank for your patience :encouragement:
>>It needs a negative cable too, going to one of the other batteries.
The negative line is there but in pencil


Is this correct?
View attachment 75415
Click to expand...

You're basically correct with that sketch, it almost matches mine :)

I see your negative cables, but i mention it as it is important to remember that all of the battery cables need to be sized to start the engine. The VSR cables will be thinner.

Not the end of the World, but it's best practice to connect all of the loads and charging sources to one battery and all negatives to the other. You should also have fuses in any cable that is connected to the batteries, close to the batteries.

Am I correct ref the 'both' or 'Start' switch setting to charge the start battery?
It looks like I can stop the start battery being charged using the switch.
Click to expand...

No, you're mistaken. I note that you are concerned with charging the engine battery via the VSR, those concerns are unfounded. When you leave your boat the solar and wind controllers will be charging the batteries (providing you stick to the drawing and connect them straight to the batteries, nut the switch common), once charged the controllers will go into float. As you will have no loads on any of the batteries whilst you are away the batteries will require nothing more than maintenance charging, so no worries about cooking the engine battery, even though the controllers will sometimes charge at absorption voltages.

When you are onboard and you discharge the domestic bank, the controllers (or alternator) will charge the domestic bank at normal charging voltages. The engine battery will still be OK, you can't force charge into a battery, it's self service, it has to help itself and it will (can) only take what it needs.

As an example (i could give many), my own domestic bank consists of 390ah (3 x 130ah) and the engine battery is a plain old lead acid van battery. I have 260w of solar power and a Victron Cyrix is connected between the batteries. My batteries have been permanently connected to the solar panels and a 30a mains charger for the last three years. I have had no issues. I have fitted many VSRs and know of no-one who as had an issue.

If you're still not convinced, don't fit a VSR, fit a Victron Argofet. That will only charge the engine battery whilst the engine is running.

Regarding battery choice, i'd recommend an Optima Red Top. Whatever size you have room for.
 
tony12345 said:
@PaulRainbow Can you help me understand what happens when a 25Ah battery is in parallel with a 200Ah battery and they are both being charged at >13.5V but the 25Ah battery is fully charged and the 200Ah battery still needs charging?
What's happening to the 25Ah battery?
Why isn't it over charged and damaged/over heated etc?
Click to expand...

Just did, our posts crossed :)

If you think the VSR would cook the smaller battery, what applications do you think the VSR would be used for ?
 
Good question.
So regardless of the switch position the start battery gets charge via the VSR?
The switch just selects which battery supplies power?
Thank you very much for your help/advice. Very much appreciated.
 
tony12345 said:
Good question.
So regardless of the switch position the start battery gets charge via the VSR?
The switch just selects which battery supplies power?
Thank you very much for your help/advice. Very much appreciated.
Click to expand...

That's all correct Tony.

Regardless of switch position all batteries get charged by wind or solar, even if it's switch to the "off" position. With the engine running it will charge all batteries, whether switched to "1" or "2", don't forget, never set to "off" whilst the engine is running.
 
The aerogen has a regulator designed for two separate batteries. It may be that one side can be moved to the start battery. I will investigate.
At the moment when the yacht is laid up I disconnect the batteries and attach a 10w solar panel direct to the batteries via what I believe is a rectifier. No regulator as it's just a trickle charge. Came with yacht. Has a single negative and two positive clips.
That should still work if just connected to the just the domestic bank or the starter battery I guess?
 
tony12345 said:
The aerogen has a regulator designed for two separate batteries. It may be that one side can be moved to the start battery. I will investigate.
Click to expand...

The Cyrix will take care of all batteries, so no point Tony.

At the moment when the yacht is laid up I disconnect the batteries and attach a 10w solar panel direct to the batteries via what I believe is a rectifier. No regulator as it's just a trickle charge. Came with yacht. Has a single negative and two positive clips.
That should still work if just connected to the just the domestic bank or the starter battery I guess?
Click to expand...

Won't be a rectifier. May be a split charge diode. What's it look like ?

Not one of these ? ; https://www.google.com/search?q=spl...wP_fAhWwQxUIHQl_Aa4Q_AUIDygC&biw=1213&bih=624
 
Reg aerogen reg. Not sure if it will like one side being open??
It's a black thing with(maybe) heat sink type fins. Yes probably splits the panel output in two
 
tony12345 said:
Reg aerogen reg. Not sure if it will like one side being open??
It's a black thing with(maybe) heat sink type fins. Yes probably splits the panel output in two
Click to expand...

The Aerogen controller won't care if it's only connected to one battery, there's no point connecting it to both banks as the VSR will close if the windgen is charging.

If the previous owner has connected a 10w solar panel to a split charge diode you may as well not bother, tiny amount of current, through a device that suffers voltage drop isn't a great thing. I assume you're only disconnecting at the end of the season, in which case it just clip a couple of 10w panels straight to the batteries, one to each bank.
 
tony12345 said:
Thank you Poey50.
How are the straps fixed to the locker?
What size Ah CCA etc is your starter battery?
Click to expand...

This kind of thing for the battery straps - 3 vertical straps and 1 horizontal keeps it secure so 8 plastic brackets (16 screws) screwed in retains the straps. https://www.marinesuperstore.com/ba...E9VzCDnhcr91O8kOrEVm04FjRghgF2fEaAiVQEALw_wcB

It's a Red Flash 1100 sealed AGM only 43ah but 500 cold cranking amps (-18C). Very pleased with it on my 29hp Nanni.
 
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tony12345 said:
Can you help me understand what happens when a 25Ah battery is in parallel with a 200Ah battery and they are both being charged at >13.5V but the 25Ah battery is fully charged and the 200Ah battery still needs charging?
What's happening to the 25Ah battery?
Why isn't it over charged and damaged/over heated etc?
Click to expand...

Consider this analogy.

Two water tanks of different capacities representing the 200Ah battery and the 25Ah battery

icsql5.jpg


They are both the same depth D representing their voltage

They contain some water , the depths of the water, d1and d2, representing the states of charge.

They can be filled by a common pump whose pressure is controlled to match the depths of the tanks. This represents the alternator whose output volts is regulated to match the voltage of the batteries.

As the tanks fill the water level will always be the same in the two tanks, water flowing into the smaller tank more slowly than into the larger tank. In the same way the two batteries will always be at the same % state of charge, a smaller current flowing into the smaller battery.

A situation in which the small tank becomes filled ( fully charged) and overflows ( overcharges and overheats) before the large tank is filled will not develop.
 
PaulRainbow said:
That's from post #8 Vic.
Click to expand...

Post #8 reads:

PaulRainbow said:
As i said earlier, replace one existing battery with a new engine battery, so far, no difference to what you have now, no extra parts (except the battery), no new wiring.

You now have a second battery for the domestics. All this needs is a pair of cables to connect it to the existing domestic battery.

If you then add the Cyrix, as per your diagram, all batteries get charged automagically.

Here's a basic diagram, no fuses etc are shown.
Click to expand...

But there is no sign of a diagram :confused:
 
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