Battery/Solar questions!

[Robster100]

Hi

I have very recently purchased a motorhome and p/e my caravan.

In the caravan I had a Car Current Tester, permanently attached to my leisure battery, so I could monitor the amp draw or or top up coming from my solar panel.

At least I am reasonably sure that is what I had, a - number was always higher the more devices I turned on and a + number when very little draw and a nice summers day, going into a partially depleted battery.

I wanted to do the same on my Burstner but I am not getting the readings I would expect, they are always - numbers, I can certainly increase the Amps being drawn by turning on all the lights and the playing a dvd i the tv, but with everything largely switched off I still get a -0.3A regardless of how sunny the days is.

However, the battery IS being recharged, because having run it down yesterday to around 12.5V, it was again showing 13.8V when I checked it midmorning today.

I am hoping someone on here could point out the stupid thing I have done or not understood!

I am attaching a couple of photo's of the device and my battery compartment, which shows where the device connects to, basically replacing the fuse from the solar charger .

Hope someone can spot my dumb mistake. :-(

 

[Robster100]

Please ignore the crocodile clips, they are my temporary solution for a 12V extension lead to provide 12V sockets that my van is sorely lacking!

Robin

 

[funflair]

So is it the grey thing the "shunt" that you fitted to measure amps? and is that in the cables from the solar controller.

Martin

 

[Lenny HB]

If your control panel is switched on it's normal to have a current draw of 0.3 to 0.5 amps, with the panel turned off the system will still draw 0.1 to 0.2 amps.
However during daylight hours the solar input should more than compensate for it.
The battery when on charge either from mains or solar will get up to 14.2v volts then after the absorption phase it should drop to a 13.8v float charge.

 

[Vipar]

Greetings peeps welcome from West Kent

^{_{Subscribers  do not see these advertisements}}

 

[ramsthom]

Try turning the car current tester the other way in the fuse holder and it may show a + value

 

[Robster100]

My answers to some of the responses.

1. Yes, control panel is switched on, I am not hugely worried about that light draw, it is the lack of seeing the solar panel working that concerns me.
2. Hello peoples in West Kent!
3. Yes the grey shunt is connected to the solar controller output to the battery, the red lead is coming directly from the solar controller to the battery terminal.
4. Ummmm, okay, I was SURE I had tried the shunt both ways, obviously not!

However, now it is show a pretty steady +0.45A and this does not change, turning on the TV/DVD player, turning on all the lights, or even turning everything off including control panel, still sits at the same level regardless.

So I guess this is truly just showing me the power coming into the battery from the solar panel, but why did it dip to -4.5A when I had the shunt the other way around?

 

[Lenny HB]

You need to turn a load of stuff on in the van to run the batteries down a bit. Then you should be able to see if the solar is working.

 

[Robster100]

I did that this morning, had all lights on, most electrics and tv running a DVD, battery dropped from 13.8V to 12.5V, still only showing 12.8V

 

[stevewagner]

I see that the MPPT controller is next to the battery. If you have a multi-meter try getting a reading from the output side. If not connect your current tester to it and you'll see what the real output is.

^{_{Subscribers  do not see these advertisements}}

 

[Robster100]

MPPT?

 

[funflair]

MPPT?

Solar controller.

 

[autorouter]

The grey 'shunt' is connected into the positive wire from the MPPT controller to the battery. In that position is can only measure the current from the solar controller to the battery, not the current to the habitation loads.

The solar controller current depends on the sunshine level, obviously, but it also depends on how charged the battery is. If the battery is fully charged, very little current will flow. If you turn on a load, the battery voltage will drop a bit, and the solar panel will supply current. Ideally it would supply just enough current to power the load, and leave the battery fully charged. If the panel isn't powerful enough to do that, it will supply what it can, while the battery provides some too.

So that's why the solar controller current varied with the load as well as the sunshine level.

You could use a positive 'bus bar', and connect the shunt between the battery and the bus bar. Then connect the solar controller, habitation loads and mains charger to the busbar instead of directly to the battery. Then your shunt will read exactly what is going into and out of the battery, regardless of where it's coming from or going to.

Usually a shunt is connected on the negative side, but it should work just the same on the positive side like you have it.