Odd Occurrence with L-16s
I have been living off-grid for 12 years now. I am experiencing an odd occurrence with my batteries and I am looking for thoughts. I am having L-16’s go bad in the middle of my strings. I am going to replace the batteries this week to the tune of $5k - $6k but I need to make sure there is no other issue in my system before doing so.
1st, I will admit I am not the greatest at maintaining my batteries and when this current set of L-16s was 42 months old I went about 2 months without checking the water level. UGH, and other non-printable words. What an idiot as I discovered a few of the batteries had the plates exposed. But, it is what it is and I wanted to give some background as to the history of the batteries. When the batteries were 46 months old I did end up replacing 2 of the L-16s. The batteries are currently about 54 months old.
The original PV system was a 1.92kW PV, 48v system, 24 L-16 batteries wired in 3 series –parallel strings, 2 SW5548 inverters with 1 Outback MX60 charge controller with a Kohler 11RMY generator. When the system was about 4 yrs old the PV was increased to 2.08 kW when the PV modules were replaced under warranty. This was the size system in place when I failed at my maintenance.
When the batteries were 46 months old, which is when I replaced those 2 L-16’s, I increased the size of the PV system to 4.6kW, adding a new Outback charge controller and redesigning the previous inefficient battery layout: the 3rd string at end of 2 side by side strings which had unequal length cables coming off the inverter feeding the 3 strings. I now have 3 side by side strings with the cables coming off the inverters to a buss plate with other equal length cables going from the buss plates to the strings.
The generator normally ran about every 2 days or so in the winter time. In the summer time the generator ran about every 4 – 5 weeks. The generator ran for the 1st time about 10 weeks after increasing the PV output the middle of last summer and this winter the generator did not run but once a week until the mid-part of January when it started to run about every 3 – 4 days and this past week it has run daily. I also am once again started religiously checking battery water level every 4 – 5 weeks and only add a little bit of distilled water each time. However, I am now checking the water level weekly but again adding very little water.
Below are the odd occurrences since last October:
October: Checked battery water level at 4 weeks since checking last time and found all batteries in the middle string had plates exposed. What!*? I do not remember if I checked the battery water level before or after the generator ran for that 1st time 10 weeks after not running, which was the time prior to making this discovery. All I know is I checked the water level every 4 weeks since I discovered the exposed plates at 42 months old. So, filled them all up and went on my merry way.
February: 3 weeks ago I discovered 4 bad batteries…well, 1 is kind of bad..in all 3 strings. So, I dropped from 3 strings down to 2 strings, leaving 4 batteries connected to each other but not connected to the PV system. There was 1 bad battery @ 1.x v in 1 string, and 2 @ 4.xv in another string. That is 3 bad batteries and the 1 kind of bad battery? It is not in the system now and still reads 6.2v without having been charged in over 3 weeks But, it was in the 3rd string & I pulled it out because I discovered the cable had gotten so hot the outer sheath had pulled back over the inner sheath and the cable actually pulled itself thru the lead terminal, leaving me with 1 string completely disconnected in the middle.
February: this past 4 days I have replaced 2 L-16’s using the disconnected 6.2v batteries. I now have one of those 2 L-16s reading 4.9v after it read 6.2v when I put it in the string. And, it is in the middle of the string. Also odd was one of the end batteries did not read 6.x v..it read 11.x volts whereas the other batteries all read 6.xv (after I changed the 4.x battery out). The next day it read 2.x v so it got changed out.
It does appear the cables...guessing about 12" long in an s-shape do have corrosion inside as I can hear crunching noises on some of the ones I have removed when I try to straighten them.
It appears the middle batteries in 1 string are going bad.
Any thoughts as to why the middle batteries are going bad?
Any thoughts as to what would cause that middle battery cable to get so hot it pulled thru the terminal
Can I still use that melted terminal battery if I clean up (file the terminal flat again) the terminal and sandwich the cable to the terminal somehow, using larger diameter washers, etc?
Anyone ever use metal bars to connect the batteries instead of cables? If so, where can I buy them? I would think that would be better for corrosion purposes, but worse given the safety aspect of more exposed metal connecting the batteries vs. just the terminals.
Inverter settings can be provided if needed. Inverter is set to come on automatically once voltage drops to about 47.6v over 2 hours, if I remember correctly. Voltage usually ranges from about 49.2v – 50.2v during the evening when we are home using things and the fridge is running, tv is on, freezer runs, well pump comes on, etc, and is about 1/2 - 3/4 volt less in the morning when we wake up, usually about 48.8 – 49.4v.
Thanks for the thoughts as if there is an issue with this system I want to get it fixed before I drop money on new batteries.
EDIT" PS..the room with the batteries is unheated.
Modules: 5.395 kW:
(16) Kyocera KC130TM
(12) Kyocera KD-210GX-LPU
(3) Kyocera KU265-6MCA
(24) Trojan Solar SPRE 02 1255
(2) Zomework trackers (KC130TM modules, 8 per tracker, landscape position) - facing due south
(1) Unirac ground mounted fixed rack (all KD210 modules, landscape position) - facing slightly southwest
(1) Unirac roof mounted fixed rack (all KU265 modules, landscape postion) - facing due south
(2) Trace SW5548
(1) Outback MX60 - for (16) KC130 modules
(1) Flexmax60 - for (12) KD210 modules
(1) Flexmax60 - for (3) KU265 modules
(1) Kohler 14RESA propane