Strange behavior

[offgridQLD]

I'm looking at my laptop now (remote app)  and the battery's are on float holding a rock solid 55V as the battery temperature is spot on 25 deg. The wattage going into the battery's from the charge controller (that's showing in the remote app main screen) to hold float is fluctuating between 20 - 38w for the past 1/2 hr :?:

Why so low, how can this be just 38W!

Lets look at the loads. Modem 15w, router 10w , wifi repeater 5w, septic air pump 5w, standby loads 3w, inverter always on self consumption 65w. That adds up to 108w of loads then it always takes a extra 20 or so watts extra over the base loads to hold float. Around 130- 150w. When the fridge kicks in I usually see 230 - 250w.

For a moment I started thinking to myself hmm the inverter must have shut down and I have lost all my loads on the battery. Then I gave it some thought its imposable. The inverter must be on as I am remotely monitoring the system live so the modem, router and wifi repeater all have AC power. So that covers that one idea.

Then about 45 min of this strange low 20 - 38w float wattage  it jumped up to 130w (I that's the fridge kicking in as that adds about 100w ) Only to drop back down to 20 - 30w 1/2 hr or so later.

Its got me buggered how its managing to hold 55v float voltage on a 48v big 1330ah flooded led acid battery + cover 108w of loads with just 20 - 30w going in ? Its even dropping as low as 5w for a few seconds but spending most of its time around 30w and no more than 38w. it doesn't add up as the voltage should just be dropping with this low float wattage as its not enough to cover the loads.

Strange behavior could I have a problem with my classic 150

i took a short 1min video of it below holding 54.8v (slight temp comp at the time) with between 0.2 - 0.6A going into the battery its to low to be possible.
http://www.youtube.com/watch?v=wFiRUEiQQrA&feature=player_detailpage
Ideas?

[offgridQLD]

several hrs later the same thing floating between 5 - 38w holding float voltage of 54.9v. yet covering 108w of loads

Jumping up by 100w every so often to cover the compressor cycle of the fridge then dropping back down.

My thinking is ..One its reading the battery voltage wrong  but unlikely.  Two its showing the wrong charge wattage - Amps going into the battery just on the local app. but its never done this before.

Time will tell when I get to the house this afternoon and find a discharged battery or not 

What kind of internal shunt dose the classic use to monitor the amps its feeding the battery and what would make it do crazy things?

Kurt

[dgd]

I don't think there are current shunts in the Classic, I suspect it's using Hall effect current measuring  devices for in and out current. Not exact but apparently the amps to battery is within and amp or two of the real value.

That 100+ watt load you calculated as the  normal load, how accurate is this?
I was surprised to see my loads were about 45w instead of 150w as calculated. Device such as router and switches and laptops seem to use next to nothing once they get to working temp and are idle. Each time I used the laptop and sleeping parts woke up the 5w used went up to 9w.

Anyway just a thought...

Dgd

[offgridQLD]

Well the 6000w selectronics inverter charger consumes 65w when on and doing nothing. I remember throwing all the small loads on a watt meter some time ago and the numbers I am giving is from memory but even if you 1/2 them all and it took no power to keep the 63kw battery at float its still 1/3 the power going in to whats going out.

So tell me then. Because the classic uses a Hall effect to do current measuring perhaps the reason for it being very inaccurate below say 100w or so.

I have seen very strange behavior from hall effect watt meters. Especially when measuring a low wattage load and you put a additional load on like a old style 240 - 12v  transformer to drive a 50w down light and the wattage actually drops say 20w rather than going up 50w when you flick the switch that's funky but its true. They have some down sides.

Anyhow another hr has passed and now its floating at 11w Im sure its not accurate.

Kurt

[TomW]

offgrid;

I wonder if that 65 watt draw for the inverter being on goes away as the load gets near its value?

I do not know but it just seems that the idle draw would be reduced as the inverter gets active? As in you have a 50 watt load does the inverter draw 115 watts (65+50) or some value between 65 and 115 or the original 65?

I think you may be chasing ghosts or just seeing differences in measuring or something.

I am no expert.

I use the shunt in my epanel to watch the "net" current to my batteries and that helps me see what is actually happening. My Outback FX inverter only shows load in 100 watt steps so tracking what it is using with the internal system is not very accurate. And comparing it to what the classic says it is putting into the batteries just will not work. With the shunt and a zero center ammeter I can tell at a glance if I am balanced, drawing or charging.

Just how I do stuff here.

I think It would be very difficult to be certain what is going on without live simultaneous measurements of the loads and the source values.

Just from here.

Tom

[Halfcrazy]

The Classic uses Shunts to measure current and is generally very accurate. Not saying it can not drift but it should recalibrate every time the relay opens.

Ryan

[offgridQLD]

65w is just the dc consumption to power up the inverter. Its what it takes to run the beast . Its interactive  inverter and charge + a data logger. I think its just what it takes.

Ryan,
         Thanks for that well I'm not sure whats going on then. I'm at the house now so I will see how it plays out tomorrow as i can watch the loads real time but im 99% confident i know the base loads when I'm not at the house as it hasn't changed in the past year.

but 30w isn't enough to maintain (float) voltage and cover the loads that's for sure especially as it did this from 10am - 5pm.




Kurt

[Halfcrazy]

Well remember 1 amp is 48-58 watts depending on battery voltage. So say the Classic was off by 0.5 amps this would be close to 30 watts. I also wonder like Tom did if the inverter becomes more efficient as loaded so the loads are not really seen at the 60-70 watt range?

Ryan

[offgridQLD]

I also wonder like Tom did if the inverter becomes more efficient as loaded so the loads are not really seen at the 60-70 watt range?

Like I said above it just takes some power to run the inverter even under no load. The manual puts this down as 65w and the shunts seem to confirm this.  Though I do kind of see what your getting at that is can provide say up to  50w load  without consuming any more dc power than it dose to sit idle.

I'm not to sure on that perhaps (getting my head around it)

The big difference today is I monitor the system most days and for the past 115 days I have had the classic installed. The lowest float wattage I see is around 120w ( that kind of added up ok to me) This sudden drop today was out of the ordinary.

Kurt

[Halfcrazy]

I agree when you do something that many days in a row and it changes it makes you back up and say HUH?

I guess till you get there and can monitor it we will have to wait patiently 

[offgridQLD]

Yes I am on location now but got to the house just as the sun was going down.It's 9:45pm Friday night where I am and its dark so no action from the controller. Tomorrow once the battery's hit float I will go to the power room and see if i can nut it out (that's if it dose it tomorrow)

Kurt.

[dgd]

The Classic uses Shunts to measure current and is generally very accurate. Not saying it can not drift but it should recalibrate every time the relay opens.

Ryan

Shunts generally do not drift and are physically calibrated when manufactured.
If there were two 150amp shunts in the classic box then I think they would be physically large enough to be noticed. Drifting occurs with Hall effect current sensors and recalibration becomes necessary on a regular basis.
The input voltage and current displayed by the classic are quite suspect as often when compared to output volts and amps the output wattage exceeds input wattage 

Dgd

[Halfcrazy]

Trust me the Classic uses Shunts. I do not have a picture now but will try to find one


Ryan

[dgd]

Trust me the Classic uses Shunts. I do not have a picture now but will try to find one


Ryan

Ok, they must be well buried under those circuit boards...   

Dgd

[offgridQLD]

It would be interesting to see the inner workings and the two shunts. Just to give me a better understanding of the product and the basic layout.

I tend to agree that unless your chasing milliamp  accuracy most shunts I have used even on cheep imported devices tend to be surprisingly accurate over the years without any recalibration. though I would imagine if a shunt was overloaded and over heated that could mess with its accuracy.

I do have a few very small devices $30 (the size of two match boxes ) with a  130A shunt inside of them. Along with lcd screen and other electronic circuitry. So I believe the classic has lots of space for two shunts. Even the cheep devices are accurate to within a few watts (comparing 4 of the same devices on the same fixed load)

My view is perhaps the classic knows whats going on but there is things getting skewed between what the classic is reading and what the local app is displaying. though i don't have anything to back that up 

Kurt