Onboard dual bank charger and VSR issue

[Ferg]

Around a month ago installed a Noco Genius 2 bank charger, and it charged both house and start banks just fine.

This morning I installed a new BEP VSR cluster, because the old one wasn’t paralleling, and now it is.

Now only one bank is lit up on the Noco charger, the other has no lights whatsoever.

Here’s my question:
Is a dual charger really required when you have a VSR?

I’m thinking of returning the dual charger (while it’s still in the grace period), and getting a larger amperage single bank, utilizing the VSR to charge the house bank.

What am I missing?

Thanks

[Ferg]

Got it figured out. One charger bank didn’t see my battery type. When I selected AGM, it fired right up

[smckean (Tosca)]

I'm not an expert, but I have a thought or two. If I'm wrong about this stuff below, someone please correct me.

The VSR should only be involved with the circuit that brings amps from your engine alternator to the battery banks. The dual output charger circuits do not pass thru the VSR, but instead each charger output should be permanently attached to one bank or the other (with both banks on one or the other of the 2 charger outputs).

The alternator doesn't know about multiple banks, it just puts out amps. That's why you need the VSR in order to direct those amps to the starter bank only while it needs charging, and then when the starter bank is fully charged, the VSR switches the alternator output to the house bank. OTOH, the charger has the smarts to operate the 2 outputs independently -- supplying amps to each bank only when that bank needs the charge no matter the state of the other bank. I suspect only one bank is lit up on the charger because the other bank is fully charged.

[Ferg]

Thanks Sandy

I agree that a VSR is primarily for use when you’re underway.

The VSR doesn’t care where it gets its voltage from, from the engine when underway or from the house charger when not. Once it sees 13.7v, the relay closes to parallel start to house. That’s why I considered one charger.

But now that both banks are charging from the onboard charger, I have another thing to consider. I’m not quite finished mounting the cluster, but this new one has the option to isolate the VSR when the boat isn’t running by connecting it to the ignition circuit. I just may do that, because I don’t like idea that it’s basically always paralleled

[smckean (Tosca)]

Ferg,

I am puzzled by your use of the word "parallel". To me the use of that word means the battery banks are connected "in parallel" meaning positive to positive and negative to negative. But if I understand the function of a VSR properly, its purpose is just the opposite. That is, the VSR insures that the 2 battery banks are never in parallel (unless manually switched to be so as one would do if one had a dead starter battery), but rather that the amps from the alternator flow to either bank but never both. I thought that is the entire reason for having a VSR since you don't want a low SOC (state of charge) battery connected to a high SOC battery.

P.S. You enlightened me about a VSR and the charger. It seemed wrong to me (as I mentioned) that a charger circuit would pass thru the VSR; and altho that is strictly true, I never considered that since the charger and the VSR are both directly connected to the battery bank, when the charger is on, the VSR will "see" the 13.7v from the charger and think the battery is fully charged. Never thought of that!

[Ferg]

What the VSR does is checks the voltage on the starting battery, and when it’s fully charged to 13.2 volts it parallels it to charge the house bank.

When the start battery voltage drops below 12.7 it isolates the house bank

Here’s the info:

https://www.bepmarine.com/en/p/710-140a

[TyBoo]

[Ferg]

I finished the installation today, and I’m happy with the setup, and I think I’ve remedied my concerns.

My boat is generally out of the water, connected to an onboard two bank charger. Once I installed the VSR, because it saw over 13.2 volts, it combined both banks, effectively combining house and start. So when I go to start the engine both banks are engaged. That’s not good

This new VSR cluster now has a configuration to allow you to switch the VSR off and on. It’s off until I’ve started the engine, and then I close the switch and let it do it’s thing.

BEP calls it “Storage Mode”

[thataway]

One confusing item is that the VSR combines if the voltage is over 13. X volts (some are .2 and some .6) on either side of the VSR. Thus the reason to turn off the VSR when using a smart battery charger like the NOCO Genius series.

The start and house battery may be different capacity or even type, or age. For the relatively short time, when charging off the engine alternator that does not make any difference. But when in storage, and the NOCO is sampling periodically and applying charge, you want each battery isolated.

[Ferg]

Thanks Doc, your affirmation of my analysis makes me think I did the right thing

[smckean (Tosca)]