Smart BatteryProtect LVD

dwh

Tail-End Charlie
According to this, I can use a two-bank charger while both banks are connected in parallel without separating them during charging....is that right?

Yes, but any multi-bank charger could do that. If your charger can handle a 230ah bank per charging leg, then you wouldn't need to rig two banks anyway.

And that whole thing about rating the charger by battery bank AH is marketing BS anyway.

With 2 batteries that spec a max of 30a each, you need a max of 60a of charger. The Noco Gen2 is only a 20a charger - 10a per bank.

You could rig one leg to each battery or tie both legs together to feed both batteries.

But no matter how you rig it, you've still only got 1/3 the max specced out for your 230ah battery bank. In other words, pretty much the bare minimum.

No worries, you won't burn down the house. :D
 

jacobconroy

Hillbilly of Leisure
Yes, but any multi-bank charger could do that. If your charger can handle a 230ah bank per charging leg, then you wouldn't need to rig two banks anyway.

And that whole thing about rating the charger by battery bank AH is marketing BS anyway.

With 2 batteries that spec a max of 30a each, you need a max of 60a of charger. The Noco Gen2 is only a 20a charger - 10a per bank.

You could rig one leg to each battery or tie both legs together to feed both batteries.

But no matter how you rig it, you've still only got 1/3 the max specced out for your 230ah battery bank. In other words, pretty much the bare minimum.

No worries, you won't burn down the house. :D

Cool. I have all the time in the world for them to charge when on the NOCO at home, so the 10 amps isn't a problem. On the drive home they will receive a partial, higher amperage charge from the alternator. The NOCO is really just for maintaining them. I've noticed that it takes much longer to drop the rear battery to 12.1 since the NOCO came into play.

There is a lot of conflicting opinions about this on the Interwebs. Some say (including NOCO, thought they have managed to word without actually mentioning a separation), that it doesn't matter if the parallel batteries are separated when using a two-bank charger. Others say that batteries in parallel are "one battery" to outside devices seeking voltage (and I tend to believe this. How on earth could each battery be topped off properly if the charger can't distinguish between the two?). One batter is two years old and I'd rather they be dealt with separately.

So, I am going to separate them with a solenoid during battery maintenance because...why not? I've been trying to find a normally-closed solenoid and so far it hasn't been easy.

I have found a toggle solenoid, but I haven't yet thought of a way (or found the parts) to make this work. Sure, it's great that it will use no amperage during open or close positions...but a normally closed setup will only use amperage during maintenance and that shouldn't matter because there is plenty of amperage available.

Have the feeling that I'm missing something though.
 

jacobconroy

Hillbilly of Leisure
OK. I can't find a high-amperage normally-closed relay or solenoid and I don't want the mess of joining them in parallel. So much for doing this on the cheap.

I'm going to use two Smart Victrons because they can be used as a high-amperage, normally closed relays (thanks to the remote disconnect feature) and will see if this works:
  1. One Victron will go between the engine battery and the coach batteries and set to disconnect at 12.3 volts. The remote disconnect circuit will be broken when the NOCO begins battery maintenance.
  2. Another Victron will go between the two 125 Ah coach batteries and set to 12.1 volts (just to sound the alarm if my voltage gets that low). The remote disconnect circuit will be broken when the NOCO begins battery maintenance.
Unless I have rocks in my head, this will automatically isolate all three batteries when I plug into shore power, protect the starter battery, and give me over 125 Ah to use without abusing the batteries. In short, no more battery worries at home or camp.

My last question is this...now that I have two 125 Ah batteries that will be drawing from the alternator when I leave camp, what amperage rating should I get for the Victrons? Shore power won't be an amperage issue, but I have no idea how many amps will flow through that circuit when leaving camp with two big batteries at 12.1 volts.
 

dwh

Tail-End Charlie
I haven't studied the docs on the Victron disconnects...but it seems to me you've got this backwards...

The issue with dissimilar batteries is the batteries not having equal, or very close to equal, resistance. Tying different batteries during charging doesn't matter, because each will suck up (absorb) power in its own unique fashion until its electrolyte is fully saturated. But having say an older battery tied with a newer battery during discharge is bad mojo. The newer battery will have a lesser resistance, and will do more work, thus wearing out quicker. Eventually, it will reach a state of wear more or less the same as the older battery - but not exactly the same - and then the "which one works harder" situation will ping-pong back and forth between them - eventually causing both to reach a premature end of life.

The same thing happens with equal batteries (same age, brand, model, size, etc.) but unequal wiring.


The idea of "isolating all the batteries when on shore power" is what's backwards. They should be tied together when there is a charging source, so they all get fully absorbed and maintained. The disconnects should come into play when the charge source is removed, to isolate the batteries from dragging each other down.
 

jacobconroy

Hillbilly of Leisure
The idea of "isolating all the batteries when on shore power" is what's backwards. They should be tied together when there is a charging source, so they all get fully absorbed and maintained.

I don't understand this. If you can simply charge multiple batteries in parallel with a single charger, then why do they make multi-bank chargers? I know that you can, but is it the best way to keep multiple batteries in parallel healthy? Or, say, is any theoretical benefit to individual maintenance just not worth the trouble?

Let's say that two batteries in parallel charge at different rates (for whatever reason). Does the single charger overcharge one to bring up another? Or does it charge one properly and undercharge the other? How would a multiple bank charger "maintain" multiple batteries if they are on the same circuit?

Maybe multi-bank chargers are meant for multiple batteries that are being charged by a single alternator, but are wholly different, isolated circuits from then on (like maybe a boat)?

Up until now I was using the 2-back charger to maintain both the engine and coach battery and they are very different batteries. It's worked well and I was disconnecting them manually during maintenance.

You gave me a good idea dwh. :D I guess the coach batteries don't need to be wired in parallel. I was worried about them being different ages anyway. I suppose I could wire the Propex to one coach battery, and the fridge to the other. These are pretty much my only draws. My goal is to stop watching the voltage levels when camping for multiple days. In this scenario I could get a multi-battery isolator (X3). I think that would charge all three batteries equally from the alternator but keep them isolated. And, when I plug in the NOCO it can deal with each coach battery individually.

Thanks, definitely making my brain work today.

Does anyone reading this have a multi-bank charger in their rig? If so, how is it being used?

Thanks.
 

jacobconroy

Hillbilly of Leisure
Everybody and their dog makes all kind of solenoids. Cole Hersee is good as any. http://www.elecdirect.com/media/specsheets/CHh1.pdf

That is one of the spec sheets I was reading earlier today. The only one I've found is a Hersee 24420, and it's rated at 35A amps on the NC contacts, 85A on the NO. I need a NC rating of at least 65 amps (I think)...probably 100A for two coach batteries.

If 35A is enough for the alternator charging two batteries at once it would work, but I'm not sure about the necessary rating for my circumstances.

I'd really rather use solenoids if possible. A standard NO one up front, and a NC one to isolate the coaches. Maybe I just don't know what to Google. A normally closed solenoid seems to be a rare item (so far, they have the same amperage rating as Bosch SPDT relays). Several companies make SPDT solenoids, but they are getting up into the price of a Victron and draw quite a bit more current.
 

dreadlocks

Well-known member
If you can simply charge multiple batteries in parallel with a single charger, then why do they make multi-bank chargers?

For maintaining multiple batteries and marine use.. key word here is "bank" and not "battery".. say you have a trolling motor and a small battery for lights, or a bunch of toys you want to maintain over winter, like lawn mower, camper, bass boat, etc.. or you have a cabin and one bank is backup for pumping and another bank is backup for heating.. or you have a small bank of batteries you want to store long term so you isolate each one so they can be monitored and maintained independently or with different charge profiles.
 
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dwh

Tail-End Charlie
I don't understand this. If you can simply charge multiple batteries in parallel with a single charger, then why do they make multi-bank chargers?

Mostly for marine use, where you have an engine start bank, a house bank, maybe a bow/stern thruster bank, and maybe a generator start battery as well.

But most multi-bank chargers do not actually perform a different "charge profile" for each bank. They just use internal diodes to keep the batteries separate so they don't drag each other down, and use one single common charge profile across all the banks. I suspect the Noco GEN series does the same. (EDIT: Though I could be wrong about this. The fact that they specify it as two separate 10a chargers does mean that it just might have two different computer brains - one controlling each 10a charger. Dunno.)


I know that you can, but is it the best way to keep multiple batteries in parallel healthy? Or, say, is any theoretical benefit to individual maintenance just not worth the trouble?

What theoretical benefit would that be? Even if you used completely separate fully programmable chargers for each battery, they would be set the same would they not? Bulk to 14.whatever volts, absorb at 14.whatever volts, float at 13.whatever volts. You have two batteries that are the same, you are going to configure the chargers the same.

And despite Noco's marketing hoopla of "8 stage charging", it is really just a bulk/absorb/float charger that bulks to 14.4v - with a few tricks added. 14.4v is a nice safe number, and that's why this non-programmable charger can be used for flooded, agm, gel, cranking, deep cycle, etc.

(EDIT: For instance, my pair of Chinese 200ah 4D AGMs specify bulk/absorb as 14.6v-14.8v. I have my Victron set to one of its default profiles, which does bulk/absorb at 14.7v, which works just fine. The Noco profile bulking to 14.4v would also work. And with the desulphation and other tricks, like occasionally bumping up the voltage, might actually work better.)

506427

So again, even if it could do a separate and distinct charge profile for each bank (which I doubt) it's simply going to use the same profile x2.


Let's say that two batteries in parallel charge at different rates (for whatever reason). Does the single charger overcharge one to bring up another? Or does it charge one properly and undercharge the other?

Nope. Each battery absorbs at its own rate until eventually, they both reach a state of 100% charge and at some point the charger drops to a float charge.


How would a multiple bank charger "maintain" multiple batteries if they are on the same circuit?

By performing the exact same "maintenance procedure" that it would do if they were on separate circuits. Since they are basically the same lead-acid batteries, the same procedure works for them all.


Up until now I was using the 2-back charger to maintain both the engine and coach battery and they are very different batteries. It's worked well and I was disconnecting them manually during mainte[nance.

It worked well not because you were separating the batteries, but because the Noco's maintenance procedure works well on all lead-acid batteries.


Thanks, definitely making my brain work today.

Cheers, that's one of my favorite pastimes.
 
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jacobconroy

Hillbilly of Leisure
For maintaining multiple batteries and marine use.. key word here is "bank" and not "battery".. say you have a trolling motor and a small battery for lights, or a bunch of toys you want to maintain over winter, like lawn mower, camper, bass boat, etc.. or you have a cabin and one bank is backup for pumping and another bank is backup for heating.. or you have a big bank of batteries you want to store long term so you isolate each one so they can be monitored and maintained independently.



Ahhhh. See, I didn't know what to Google. ? Had no idea that banks and batteries weren't the same thing.
 

jacobconroy

Hillbilly of Leisure
Mostly for marine use, where you have an engine start bank, a house bank, maybe a bow/stern thruster bank, and maybe a generator start battery as well.

But most multi-bank chargers do not actually perform a different "charge profile" for each bank. They just use internal diodes to keep the batteries separate so they don't drag each other down, and use one single common charge profile across all the banks. I suspect the Noco GEN series does the same.




What theoretical benefit would that be? Even if you used completely separate chargers for each battery, they would be set the same would they not? Bulk to 14.whatever volts, absorb at 14.whatever volts, float at 13.whatever volts. You have two batteries that are the same, you are going to configure the chargers the same.

And despite Noco's marketing hoopla of "8 stage charging", it is really just a bulk/absorb/float charger that bulks to 14.4v - with a few tricks added. 14.4v is a nice safe number, and that's why this non-programmable charger can be used for flooded, agm, gel, cranking, deep cycle, etc.

So again, even if it could do a separate and distinct charge profile for each bank (which I doubt) it's simply going to use the same profile x2.




Nope. Each battery absorbs at its own rate until eventually, they both reach a state of 100% charge and at some point the charger drops to a float charge.




By performing the exact same "maintenance procedure" that it would do if they were on separate circuits. Since they are basically the same lead-acid batteries, the same procedure works for them all.




It worked well not because you were separating the batteries, but because the Noco's maintenance procedure works well on all lead-acid batteries.




Cheers, that's one of my favorite pastimes.


Awesome! You've convinced me and saved me some money too. I can't afford to buy two more batteries of the same age (well I could, but not for a month or so). I have one $300.00 deep cycle battery and was going add another new one of the same model.

Would you recommend that I get two more of the same age instead, then tie them to one 10 amp bank on the NOCO in parallel? I could then use the other bank to charge the Jeep battery. Or put the whole 20 amps to the coach batteries?

Complicated stuff man. I appreciate the learned input.
 

dreadlocks

Well-known member
Batteries are just strings of cells, (12v = 6x2v cells) you can all charge em together.. eventually you get so many cells that the ones in the middle dont charge like the ones on the ends and this leads to that ping-ponging.. so at some point you gotta have different banks you isolate and charge independently, its how you scale up well beyond what most any of us need, especially not at just 2 12v batteries.
 

dwh

Tail-End Charlie
Would you recommend that I get two more of the same age instead, then tie them to one 10 amp bank on the NOCO in parallel? I could then use the other bank to charge the Jeep battery. Or put the whole 20 amps to the coach batteries?

Well, if they are two separate banks feeding two separate loads, the different age doesn't matter - as long as they are only tied during charging and not during discharging.

If you buy two new ones, then I'd tie them permanently into a full-time bank and feed the whole 20a of the Noco to the bank. Due to Peukert's Law, you will actually get more amp*hours out of a 230a bank than you will out of two 115ah batteries.

https://en.wikipedia.org/wiki/Peukert's_law

If you have a dual-sensing ACR, then when the house battery/bank voltage rises, the ACR will tie in the engine battery anyway and it'll get topped up and desulphated.
 

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