solar controller voltage

[FidoDido]

I've recently bought a Bimble panel (170W) and their cheap 30A solar controller (budget is tight).. I'm waiting for the panel to arrive, but the controller turned up, so I thought I'd go and install it and all the wiring ready.

 

The controller however, shows a voltage 0.2A lower than my Mastervolt MASS inverter is telling me. e.g. batts currently at 13.48V on inverter panel, 13.47 on my Clarke multimeter, but showing 13.2V on the controller. (mains charger was on, but I switched it off to measure the voltages - bats go back to 12.74 at rest)

 

Now, I'm not particularly fussed that its inaccurate, as I'm not going to use it to monitor batteries as I have better instruments. But I'm thinking that it might be a problem when the batteries are full, but showing 12.4 on the controller, rather than 12.6? Will the controller think the bats are still not full and overcharge them?

 

I dont really know how these things work, but I'll be away from the boat 3 days a week, and dont want the batteries to be overcharged. Everything else will be off for these days.

 

Do I send the controller back for a replacement? Could 1 170W panel possibly overcharge 420Ah of batteries?

 

 

Another very dumb question, which I've searched for but not found a simple answer. Topping up the water level in batteries. Cant see the side to see max/min marks. do i go to a few mm below the top of the battery, or leave a bit more space?

 

Thanks for advice

 

[blodger]

The other way round you want the plates just covered and plenty of space. Overwatering dilutes the electolyte too much so it is a bit of a compromise. You do not want the plates exposed next time you check them so it is about gaining the experiece at guaging it.

 

By the time you have your panel connected you are likely to find the situation regarding the voltage at the controller reversed with an emf gradient along the cable to the batteries. Regardless, I would just keep the difference in my head. I do not think the meter is involve in the control electronics of the controller affecting its performance. It is a better indication of battery condition than the traffic light LED's of the even cheaper ones

[FidoDido]

I'm probably overthinking it!! Thanks for advice. I will more likely use the temp sensor than the V reading on the controller!