DC to DC Battery Charger

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Andrew_Trayfoot

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I would like to upgrade my charging system.
Currently I have
1/2/Both switch
75A Alternator on my Beta 20
30W PV Panel going into a low cost charge controller that has 2 outputs to:
110A leisure battery
Engine start battery.
Hard wired 6A mains charger (Lidl) that can be plugged into shore power.


The boat originally had just a 110A Leasure Battery for everything.

I tend to use the leisure battery for everything and occasionally fall back to the starter battery to start the engine if I have pushed the leisure battery too far...

Historically this setup has worked well, but as the kids are leaving home we have more extended time to spend on the boat the extra house demand is starting to push the leisure battery 's capacity...

So before I start thinking about increasing the house/leisure battery capacity I though it might be a good idea to improve the charging system.

Any recommendations for improved DC/DC charge controller - not necessarily the most expensive options would be helpful.... :-)
 
Scrap the 1-2-B switch, fit separate switches** and a Victron VSR. Sorted (y)

Three new switches, one for the engine battery, only for the engine.
One for the domestics.
One as an emergency switch, connected to the load side of each of the other switches.
 
Andrew_Trayfoot said:
Paul, can youpist appriporte link please....
Thanks,
Andrew
Click to expand...

How about a schematic:

Charging-2-banks-VSR.png
 
Nice diagram. I am not familiar with the VSR setup. In your diagram with the Engine switch closed the alternator charges the Engine battery only, The VSR has lines to the Positive of the Engine and Domestic battery. How does the VSR sense the domestic battery state and charge it as required.

David MH
 
The VSR is a relay with contacts or sometimes electronic switch. This is activated by a voltage comparator circuit which essentially snaps into operation at a set voltage and releases at another lower voltage. The operate voltage is typically around 13.5 volts. So engine starts and charges engine battery when this voltage rises to 13.5 volts (typical of an alternator charging a reasonably charged battery) then it connects the house battery. The house battery is then subject to the same charge voltage amnd current will depend on charge state of the house battery. (tapering off when it is charged) When you stop the engine the charge voltage disappears and engine battery (and house battery voltage drops to something like 12.5 volts and VSR opens disconnecting and isolating the house battery.
Now you can start engine from house battery. But better start from engine battery. many people with 1,2,B switch start and run on both. Which is OK except you never know if the engine battery or the house battery have degraded where they can not do the job alone. To always use it on both means you ahve one battery double sized.The whole idea of 2 battery systems is firstly so that you can discharge the house battery but still be able to start engine. Isolation. A secondary advantage is that you have a spare battery for jump start if and when engine start battery dies.
Some people have 2 identical batteries which is OK except that batteries are optimised in design for engine start or deep cycle discharge for domestics. An engine start battery will be smaller and cheaper being mass produced for cars. A deep cycle house battery will be bigger and more expensive.
So an ideal set up is engine start battery for engine deep cycle for house. The disadvantage is if charging house battery from engine is that charge current falls away quite quickly and you do not get a lot of total charge from a engine run.
The battery to battery charger does much the same thing as VSR but has the advantage that it can actually increase the charge voltage to the house battery this means more voltage (16v ) so current to get battery more charged than if just hit with 14v from alternator. It senses when battery is charged and reduces current and voltage.
This effect so called "smart charging" can be achieved by fitting a smart regulator to the alternator. Requires usually opening up and disconnecting original regulator.
So the VSR will automate what you should be doing now with 1,2,b switch. It is well recommended. However to get more/quicker charge of battery from engine run you need the smart charge of a new regulator or BtoB charge. ol'will
 
davidmh said:
Nice diagram. I am not familiar with the VSR setup. In your diagram with the Engine switch closed the alternator charges the Engine battery only, The VSR has lines to the Positive of the Engine and Domestic battery. How does the VSR sense the domestic battery state and charge it as required.

David MH
Click to expand...

Andrew_Trayfoot said:
Thanks Paul.
I have the same question as David.
Click to expand...

As mentioned in post 2, the VSR is a Victron one, which is dual sensing (other dual sensing makes are available, most are dual sensing these days). So, when either battery voltage reaches the set point the relay will close and allow charging of the other battery.
 
That’s really useful. @PaulRainbow I have twin engines and currently a single off/on/both switch [Blue Sea 5511e] with 2 separate banks, one to start each engine. How should I wire that and could both alternators be utilised to charge either or both banks?
 
Scarron said:
That’s really useful. @PaulRainbow I have twin engines and currently a single off/on/both switch [Blue Sea 5511e] with 2 separate banks, one to start each engine. How should I wire that and could both alternators be utilised to charge either or both banks?
Click to expand...

You could fit two Victron Argofets. Connect one to each alternator and the outputs in parallel to each bank. You can use the 3 output version to charge both engine banks and a domestic bank, if that's what you have.

Charging-2-banks-from-2-engines-with-Argofet.jpg
 
Many thanks @PaulRainbow

I like that, with 1 dedicated 120ah/1100mca start battery it should light up the first 6 litre Sabre then with the alternator contributing charge the second should be easy, it looks to me that with this scheme it won’t matter which starts first?

I’ll also now have 3x 120ah domestics and by adding another 3x should put me in the right territory to add a 3000w inverter.

Is the software in the Argofets clever enough to load balance the two alternators [AC5 RS 12v 55amp] so that I could get a theoretical 110 amp charge to anywhere that is calling for it?

I have a Victron Blue Smart charger 12/30A with twin outputs so I assume just a feed to each bank?

Thanks. Paul.
 
Scarron said:
Many thanks @PaulRainbow

I like that, with 1 dedicated 120ah/1100mca start battery it should light up the first 6 litre Sabre then with the alternator contributing charge the second should be easy, it looks to me that with this scheme it won’t matter which starts first?
Click to expand...

No, doesn't matter which starts first.

I’ll also now have 3x 120ah domestics and by adding another 3x should put me in the right territory to add a 3000w inverter.

Is the software in the Argofets clever enough to load balance the two alternators [AC5 RS 12v 55amp] so that I could get a theoretical 110 amp charge to anywhere that is calling for it?
Click to expand...

No software in the Argofet, but the full charge from each alternator will be available for the batteries, should they be able to accept it.

I have a Victron Blue Smart charger 12/30A with twin outputs so I assume just a feed to each bank?
Click to expand...

Yes.
 
@paul rainbow
I have Solar charging with a controller to charge two banks,
Would the solar charge cause the VSR to combine the banks?
 
Thankyou, Paul, but I think that negates the argument in favour of a VSR. I I would not have confidence that the engine battery wouldn't discharge in sympathy with the domestic bank unless I remembered to isolate it, so I might just as well stick with my simple off/1/both/2 switch and remember to switch that to 2.
Unless I have misunderstood.
 
chewi said:
Thankyou, Paul, but I think that negates the argument in favour of a VSR. I I would not have confidence that the engine battery wouldn't discharge in sympathy with the domestic bank unless I remembered to isolate it, so I might just as well stick with my simple off/1/both/2 switch and remember to switch that to 2.
Unless I have misunderstood.
Click to expand...

The VSR will only be closed if the battery voltages are above the set point, so it won't discharge one bank, that's the point of it. No need to remember to isolate anything.

Not sure what you're thinking of doing (or not) ?
 
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