Off grid charging problems

Re: Off grid charging problems

Welcome to the forum... And now to "pick your pocket";):

First, do you have a DC Current Clamp Meter (here is one that is "good enough" for our needs from Sears for ~$60).

Basically, you can clamp on each wire coming from a solar panel (or series string) and measure the DC current in the middle of the day (just one wire at a time to measure current in wire). You can quickly see if each panel is supplying the expected current or not (failed panel, poor electrical connections, etc.).

Next--Is this a XW MPPT type 60 amp charge controller or a C-60 PWM controller. There have been reports of C-XX controllers working well for years and then just stop charging (sounds like you are still getting current through the controller). Seeing a peak of ~82 Amps seems a bit high for either controller (XW 60 should never go above 60 amps--C-60 may go above 60 amps and then shut down as it overheats).

And when you talk about things going down hill--What is going down hill? Amount of charging current/hours on charge? Batteries taking longer to recharge (long time to reach 14.8 volts?), batteries dieing after a night of use? Are you measuring Specific Gravity?

Are your loads consistent, or your loads are growing over time?

Do you have any measurements of how many Amp*Hours or Watt*Hours per day your loads are?

Do you have a Battery Monitor (Victron another good brand)?

Also, using the DC Current Clamp Meter, you can measure the current flow into each battery (or series connected battery string). Also, use the DMM part to measure voltages across each 6 volt battery.

You are looking for "differences". Poor electrical connections, Open/Shorted Cells, etc.

Logging specific gravity of each cell over time should help you track the health of your battery bank. And weak cells may need equalization--and if they do not recover, you may need to replace that battery (or whole bank if all are low).

Lots of questions and can be very confusing on how best to proceed... Normally, I would suggest focusing on the battery bank.

• Rewire if needed to "balance" the charging current.
• Clean connections.
• Recharge battery bank to 100% full (should be to maximum SG reading on pilot cell, all cells should be equally bubbling). May need to assist with genset/AC battery charger (up to about 5 -13% of battery bank AH rated capacity--If I understand correctly, your bank should be ~1,680 AH @ 12 volts???? or around 84 to 218 amps of charging current--Trojan recommend ~10% or 168 amps).
• Focus on Specific Gravity... Logging each cell, if cells are more than 0.015 to 0.030 sg units apart, recharge at ~15 volts. Checking SG every 30 to 60 minutes, when low cells stop rising between readings, stop equalization. Log SG readings

Once the batteries are fully charged (and hopefully still functional), need to understand Solar array configuration (all panels in parallel?) and solar charge controller (C-60 vs XW 60 MPPT, etc.).

My guess is that you are significantly undercharging the battery bank (deficit charging) which will cause early sulfation. There is also a possibility that the batteries are not properly sharing current (need rewiring, poor connections, one or more failed cells, etc.). If you have open/shorted cells, you need to pull them out of the battery bank (same if you can identify severely sulfated batteries). And build a "good string" out of what is left.

At this point, I would suggest way too large (Amp*Hour) capacity battery bank for 12 volt system... At the very least you need a larger array and a second charge controller to get enough current to properly recharge your battery bank (looking at two 80 amp MPPT charge controllers).

Understanding your loads better will help... In some cases, too much battery bank is a problem--Not enough solar array to quickly recharge, and so much current needed you need several very expensive / high current charge controllers.

You could go to 24 or 48 volts (if you need this size battery bank for your loads), and then the charge controller current requirements would be cut by 1/2 or 1/4 (Power=Volts*Current--Double the bank voltage means 1/2 the current for the same amount of power).

Ideally, define your daily loads (and if they vary by season) first. Then define your battery bank AH size and bank voltage (i.e., roughly 1,200 watts peak power, 12 volt bank. 1,200 to 2,400 watt peak power look at 24 volt bank. Over 2,400 watts, start looking at a 48 volt battery bank).

Once the loads and the bank capacity has been defined, the rest is cook book sizing of array and charge controllers (vs wallet capacity).

Sorry for the confusing/complex post--Jumping into the middle of a problem battery bank is difficult. And, since a battery bank is easily damaged by charging problems or over discharging--Like to get the battery bank back to a healthy voltage/condition first (the longer the battery bank is discharged/has problems--the faster it will die).

-Bill