Solar Controller Battery Draw Amount?

[BFL13]

This is a confused sort of post because I am confused.

I was trying to get to the minimum amps for knowing when my AGMs were truly full and to do that I tried to get all the other draws down to near zip as possible. I was even looking at how the Trimetric monitor has its own draw and you should "zero" it, but I have not done that.

I discovered that my solar controllers each have a draw on the battery bank without any array connection. (When connected they are supposed to take care of any "charging the array" at night, but that does nothing about their own draws on the battery)

I got tangled up trying to isolate the controller draws (I have two MPPT controllers in parallel on the bank) from other rig standing draws, but I was seeing quite high draws I think by the change when disconnecting them one at time from the bank--up to 1.5 amps in one case, but that might have been a false reading.

I am not clear on all this for amounts--I would have to take more time and effort to isolate them, and see what is "repeatable" to verify the amounts.

So to save me a bunch of work---has anybody else seen how much their controllers draw just from being connected--as a sort of "parasitic" load-- (never mind the debate on which loads are that, 🙂 )

Thanks

[mike-s]

As long as you're using the 500/50 (or 1000/100) shunt, you're fine.

[BFL13]

I have a 2000w PSW inverter. I do not have an inverter/charger.

I think Doug meant what has been said above, and I took what he said too far.

I will do a measurement of my solar controllers' draws just to get that info. They would not be disconnected by any battery disconnect switch if you used that instead of taking the wire off the battery post

EDIT draw was very small. I must have had "measurement error" before.

[mike-s]

BFL13 wrote:
I probably got what Doug said confused too. Here is what he said:

"..... Inverter/Chargers supply power TO THE BATTERIES, then the batteries supply power to the RV 12 volt systems. ........"

Well, that's just plain wrong. You can't have power both go into and out of a battery at the same time. Like many solar controllers, no doubt many inverter/chargers need to initially draw power from the battery to power up their control circuits and become operational. But, once they start charging (using either solar or AC power input), they're powering themselves, and what's left goes to the battery.

And, as long as everything is wired through the shunt as it should be, the Trimetric will only see what's actually going into/out of the battery. It doesn't know or care about anything connected to the "load" side of the shunt.

Again, what size is your inverter?

[BFL13]

pianotuna wrote:
If I use the main battery disconnect, because my inverter/charger is direct wired to the battery bank, I would have no loads while charging. The same is true of the solar.

Not quite the same. If you had the disconnect on the battery side and disconnected the batteries, you would get nothing to the loads since the charger part would not work.

If you did that with the solar controller or converter you would get power to the loads (except for some controllers that want the battery connected too or they will fry)

[pianotuna]

If I use the main battery disconnect, because my inverter/charger is direct wired to the battery bank, I would have no loads while charging. The same is true of the solar.

[BFL13]

I probably got what Doug said confused too. Here is what he said:

"..... YES, I am saying, MOST Inverter/Chargers will not function the Charger section if NO batteries(good or bad) are connected. Remember, Inverter/Chargers are NOT like CONVERTERS. Inverter/Chargers supply power TO THE BATTERIES, then the batteries supply power to the RV 12 volt systems. Inverter/Chargers NEED a load(batteries) to determine what to do with the 12 volt charger section........"

I always understood that the loads come first because they take from the higher voltage source like the 13.x volt converter instead of from the 12.x volt battery.

I suppose I am getting mixed up between the time before the charger starts charging, when it is drawing 12.x from the battery, and after it starts charging when it gets its "12v" from itself?

Except apparently, the charger part of an inverter/charger can't make its own? I need more coffee! 😞

[Sam_Spade]

BFL13 wrote:

If you have an inverter/charger can you recharge the batts with no load on the batts?

Yes. You are a bit confused.

[MrWizard]

Barry
Your still overthinking this
The inverter combo, might need the battery to 'activate' it
But once on,, DC power only flows one way and the load is supplied by the charger up to the point you attach some DC load that exceeds what it can supply,
Which is unlikely, unless you take up stick welding using your house batteries
Or use the emg start button to start the coach with the generator on, or shore cord plugged I

Not being a power supply, just means not automatically turned on
It's not going to melt down, just because the batteries need 50 amps for three hours

[mike-s]

Doug is wrong, unless you've wired in a non-standard way.

If an inverter/charger is wired directly to the battery, and not via the shunt, any current in/out of the battery from/to it won't be seen by the Trimetric. Everything should go through the shunt, even if you need a bigger one to support whatever current is drawn when using the inverter. How big is your inverter? The Trimetric will work with up to a 1000A/100mV shunt, and I'm guessing you don't have a 10KW inverter.

[BFL13]

Yes about the Tri. Doug said (shouted!) an inverter/charger is different from a converter in that all 12v loads come from the battery and the charger part only recharges the battery.

So I can't figure out if that means loads do not come first as with a converter or controller, which would make the Tri see net amps in that case.

[mike-s]

BFL13 wrote:
I was trying to get to the minimum amps for knowing when my AGMs were truly full and to do that I tried to get all the other draws down to near zip as possible. I was even looking at how the Trimetric monitor has its own draw and you should "zero" it, but I have not done that.

So, you're looking for when the charging current tapers down to some level so you know the batteries are full.

You're overthinking this.

Unless you've installed it in some completely non-standard manner, your Trimetric already does that as it is. You don't have to do anything. The shunt is on the negative battery cable, and the only current going through it is what's going in/out of the battery. When the battery is being charged, current to the controllers and all other DC draws isn't being measured by the Trimetric - it ONLY shows what's going in/out of the battery. The current going to other loads is coming directly from the charging source before it goes through the shunt and into the battery. They're "stealing" power which would otherwise go into the battery - the Trimetric simply doesn't see them.

When there's no charging going on, sure, it will show the current the controllers are drawing, because that current is coming from the battery.

[BFL13]

CA Traveler wrote:

BFL13 wrote:
If you have an inverter/charger can you recharge the batts with no load on the batts?

No unless the house loads are disconnected. All rigs have loads connected to the batteries, it might be small like CO2 detector, etc.

The charger, solar, house loads and battery are all connected together. Charging from any source supplies the loads and what's left if any goes to the battery.

Not sure why you singled out a charger/inverter???

This seems to contradict what Mr Wiz and LY said, but not sure on that.

The Tri measures only what is going on with the battery via the shunt. The confusion I had was about a possible draw at the same time, where we know the Tri does not measure "net" amps. Loads come first, so there is no "net"---it just looks like there is.

The inverter/charger, unlike a converter is not a power supply and the inverter/charger unit cannot operate without being connected to a battery--the pass through 120v does not operate the unit, so I suppose it needs the 12v input to light it up?

So it could be different in that maybe the load does not come first, and the Tri does measure "net" in that case? I am really confused now.

[CA_Traveler]

BFL13 wrote:
If you have an inverter/charger can you recharge the batts with no load on the batts?

No unless the house loads are disconnected. All rigs have loads connected to the batteries, it might be small like CO2 detector, etc.

The charger, solar, house loads and battery are all connected together. Charging from any source supplies the loads and what's left if any goes to the battery.

Not sure why you singled out a charger/inverter???

[CA_Traveler]

BFL13 wrote:
Thanks. So that's one. Note that when trying for 0.5 amps on a 100AH AGM, 0.2 matters.

Yes it does, which is why I don't check the solar output but rather check upon the Trimetric. Even if there were no house loads the calibrated Trimetric shunt is more accurate than my CC and I suspect most readings.

And then there is my Magnum charger. 50A display means 50A more or less. 1A means it's clueless.