Different voltage readings charge controller and multi meter

Sorry mppt was auto changed to moot

I've got an interesting problem, if anyone can help solve.

My batteries are 2v 3000amp wet batteries X 12 = 24V
The system is 3 X Xantrex 4024 Inverters
4 X 60 amp charge controllers.
40 X 190W Solar Panels

In the beggining the batteries would slowly charge up and when fully charged would take some time to dis-charge. I added the solar panels 8 units at a time over several years until 40 panels were installed.

Upon recommendations from the battery supplier (year 2) I added Tin Sulphate and Sodium Sulphate Anhydrous to prevent the cells in the batteries from corrosion. We did this by adding the powder to the acid and water as a slurry then pouring it into the batteries in a measured amount for each battery.

What a bastard of a thing to do, the sulphates are PH Neutral, so the acidity in the batteries go alkaline, we had to keep adding acid mixed with water to increase the acidity of the battery water. The powder would keep disolving inside the batteries over a two year period. We finaly got the correct acid reading and now it is maintaining these readings.

During this period I added a 10 amp hot water system to the system, silly me, when I had all outputs turned on and then turned on the inverter, the inverter made a shunting noise as the contacts closed. From then on the charge controllers and system controller have had 0.2v of difference in their readings.

The system does not seem to charge up correctly, goes to float very quickly, when in float it does not maintain a 27v charge but allows the batteries to have a rate of 25v instead. I am wondering if the system controler is faulty in its readings from a perhaps spike caused by a sudden overload with all outputs sucking energy from the inverter as the inverter was being turned on.

I have manually done an equalizer through the charge controllers and it seems to hold charge longer, when the equalizer is done through the controller it does not seem to do it properly if at all. Just goes to float way too quickly.

Any suggestions would be great, my email is keithcarrier@optusnet.com.au

Each charge controller has a maximum of around 50 amps flowing into it at peak sun. The average charge controller has 8 to 9 panels wired in parrallel giving 24vdc to each charge controller.

The panels are not facing direct to the sun but are placed on a 7.5 X 7.5m garage in rows of eight. This gives a loss of charge but also makes the panels lie flat on the roof so when big storms come around the neighbour will not be picking up my panels from his lawn. Average current input during peak 200+ amps.

Yea I agree with you the additives gave me some headaches. The powder does dissolve within the acid and the warming of the batteries during charge. I would imagine there is some sulphates that did not dissolve. This could be causing a problem.

I am leaning towards a spike corrupting the software or I have not got the setting correct on the system controller as also a part of the problem. Yesterday I equalized the batteries using individual settings on each charge controller. After equalising the charge controllers reverted to bulk charging. This seemed to work brilliantly and the batteries lasted all night and all day. Today was raining all day. Cool happy about that. Tonight I am on mains and the hotwater was switched to mains this morning.