US L16HCXC 420amp batteries in 24V bank

Re: US L16HCXC 420amp batteries in 24V bank

Sorry for the reasons of your first posting on the forum.

Hmmm... Sounds like you treated the first bank "right"--So, did you have any indications of things going wrong with the second bank (possibly even when the first bank was failing--I.e., did the first bank actually fail for cause)?

1st bank: Indication of gradual failure was on meter reading of indivual batteries and hydrometer readings plus uneven electrolyte levels (failing cell not "using"). Due to the 5 sets of 6V for the 24V system in the 1st bank, we occasionally moved batteries around within the bank. But these were 72 lb.; the L16s weigh more than I do.

What charge controllers do you currently have? Are you using remote battery temperature sensing?

Original 60amp controller was Trace (before 1st buyout); second, added with addition of more panels, was 60amp Xantrex (before 2nd buyout). Solar panel input to each controller is balanced within 0.2 amps. By sight, the circuit boards of these controllers are identical, but it's very hard to exactly match the settings of two devices with age differences (2001 & 2007).

Charging/discharging voltage? Water usage (higher/lower)? Any problems with over heated cable ends/battery terminals? What are your charging set points, what specific gravity do you measure, how deeply (voltage/specific gravity) do you discharge the battery bank? Does the battery bank get hot (during summer/heavy loading-charging)?

Bulk - 28.2, Float 27.6 US Battery tech said they sh/be 30 and 27. This area had 105 days of 100 or + degrees F. days, drought and blowing dust. Water was rationed and pressure here wasn't sufficient to wash off panels. Normal charge on sunny day is in 90amp range. Can't be specific about discharge as freezer & refrigerator cycle more often in hot weather, fans also used. Year-round is satellite internet, nighttime satellite TV, freezer & refrigerator which shows 9 to 11 amp dischage on TriMetric meter. Voltage falls from 29V to 25.2V under these loads when charge stops (both the J250s & L16s). If it falls to 24.3 before 2am, generator is run. When only load is battery room DC light, a 24.3V reading rises to 24.6V. (Disconnecting the system long enough to get readings at 72 degrees F. would result in food spoilage if it could be done - impossible from April to October.)

Yes, batteries do get hot - this is Texas.

Watering schedule during the first 2-1/4 years was 30 days ~1-1/4 gal. for the 16 6V L16s - schedule changed to 2 weeks after first cell failed. Failing cells overcharging others.

Are the banks wired with "equal" cable lengths for each string (see this web page for battery wiring)?

Cables are from 6-1/2" between those in the series set (short as possible on side-by-side negative-to-positive arrangement) and 27" between paralleled sets (end-to-end of sets). Cables from inverter enter the box from the front at mid-point and are each 7-ft. I do not understand the diagrams on this site unless the voltage application is the same as that of one battery or unless that box represents a series set. If you have access to a Trace 4800 watt inveter manual, our arrangement is that shown Techanical Information section. Our bank is not cross-wired; should I try to cross-wire without blocking access to the cells, cross-wiring cables would have to be long enough to fasten to the back of the battery box. If that would help to balance the charge-discharge, I will try. Please advise.

If you do not have one, I would suggest getting a DC Current Clamp type meter. Use the meter to check the charging and discharging current between all four (?) parallel strings and see that they are properly sharing current. This meter is fairly inexpensive and is "good enough" for debugging a DC battery system.

Link did not work but found others that did. I'd need a good gas mask to move the clamps around while charging and opening and closing the lid.

Anyway--That is where I would start. Hope you get the problem(s) under control. Batteries ain't cheap.

Thank you for your help and suggestions. Spoke to another experienced solar off-the-grider and no one has any long-term experience with the US RE batteries as only on the market about 3 yrs. In that time US has changed the wording on the L16HCXCs on their site which I feel speaks more to the scrubber, sweeper, forklift, etc. applications wherein equipment to used until discharged, then recharged offline.

Re: US L16HCXC 420amp batteries in 24V bank

HEAT
Originally there was one vent point in floor under inverter (coolest air is from under house - house is on piers) - bulk setting calculated compensating for summer heat using Trojan specs. When the automatic 3-speed inverter fan switched to highest speed one day, another larger vent in the floor was added nearest the battery box. We experimented with adding a 12v muffin fan on top of floor vents - then with an input fan at the side entry to the battery box - then an inline fan in the vent stack to the roof which exits the batterybox at the opposite end.
Results in inverse order: The inline fan in the vent stack actually inhibited air flow when not used requiring power 24/7; convection produced as much air flow when metal roof was hot (determined by using thin paper across the battery box inflow point to indicate suction). With inline fan moved, temperaturemeasured with/without the muffin fan on top of 2nd floor vent - no difference as same convection pulled air into battery box. These were the J250s, 1250 amp hr bank,1.9kW array. Reduced the bulk setting using the difference in the temperature compensation readings on the inverter meter.
With addition of panels to 3.1kW, bank was actually 10 yrs. old and beginning to fail very slowly. Still have 16 good ones. Built a box outside for them with lines from a 30 amp 24V battery charger mounted in power room intended as backup. Replaced with the 16 US L16HCXC 420s (1680 amp hrs.) only because nearest distributor, 200 mi trip, had dropped the Trojan line, and added the 2nd Xantrex C60 charge controller. Added a vent hole in the wall of power room above the battery box - left uncovered March-December. First watered the batteries to the split ring like the J250s and had indication around 1 cell that that was too high and changed the watering level to 1/4" below the bottom of the ring. For 3 summers there were no problems - able to run a high efficiency mini-split air conditioner to sunset without the $propane generator.
Sudden cell failure started in November 2011 after heat of summer passed and that's when water usage jumped on all cells. Normally I would have increased the bulk setting for winter but didn't because of the excess water usage.
Equalization for the J250's was to 31v for 2 hrs. ~30 days but TriMetric meter now displays 30.7v as highest point.
Panels mounted on roof both north/south slope - each panel on 4 aluminum rails drilled in three side positions for tilts to be within 7-8 degrees - north row at top mounted high enough on rails for no shadow at bottom of panel from ridge. This permits max air circulation. Angles changed 3 times per yr. but one slant change can be skipped and still be within the 15 degrees. Metal roof has continuous ridge vent; max temperature in attic has been 125 degrees. First 13 panels were MSX-120's, actually two 60 watt mounted in one frame which can be wired for 12 or 24V and one side was wired for 24V when lightning destroyed the other. Mounted 12 as soon as roof was finished June 21-25 2001 & could use power tools to finish the house - other panel was used on the 12'x16' tool shed for small DC refrigerator, lights and DC fan. When BP bought Solarex, this panel was discontinued - added three BP 130 watts after moving in 2004. 1.92kW array, 1250 amp hr. bank, 1.5 ratio, none of it same age. Added 10 Mitsubishi 125W (chosen by the frame size to match rails/structs spacing to avoid ridges in metal roof), these 16 L16s, the second C60 amp charge controller, and the new panels all within 3 weeks in May-June 2009 - 3.1kW, 1680 amp hr. bank, ratio 1.8. Using 12 of those batteries, 1260 amp hr. is ratio 1.8.
Have been reading the replies and looking up system components used trying to determine ratios of arrays/banks. During that time, many visits to the power room checking water/state-of-battery voltage and a third factor has now surfaced - the newer Xantrex C60 charge controller was going from normal digital display to display failure and light indicator of "Load Disconnected" which sh/not happen when jumpered as a charge controller, then back to normal again. Replaced the jumper but on day 3 it stopped returning to normal so is now disconnected - only half the array is charging a 1260 amp bank right now. (4 batteries are disconnected pending decision on the original stop-loss question). Don't know if this controller malfunction was a source of problem or there's a problem between controller and panels or if just defective - may know when replaced with the new C60 en route; disassembling/reassembling/testing. Wires from panel pairs enter the attic to two centered combiner boxes which each have lightning arrestors, ground wire from each runs straight down through a double wall to common equipment grounding for entire system. Moving the wires from one combiner box to the other is easily done to distribute flow to controllers but won't be done pending arrival of the new charge controller this week. All wires are on the shortest route; the attic midpoint combiner boxes are almost directly over the power room.
Removing 4 batteries from the box would provide room to arrange the other 12 and wire differently but still 3 strings. There is no practical way to place a bank outside of the house. The power room has common walls with the utility area and closet with insulation between but is kept much cooler than any outside structure could be. An AC evaporative cooler doesn't work well in humid climates - we had a small one for that 12x16 structure - any water circulation device requires extra loads.
Bill wrote, "It would be nice to have more solar panels for your larger bank."
Bank too large for array? That would be great news! We would rather reduce the bank to match the panels.
Given the verbose explanation of conditions, what amp hr. bank would you recommend?
Sure do appreciate all the replies.

Re: US L16HCXC 420amp batteries in 24V bank

stephendv wrote: »

How long is your absorb time set for? I ask, because I borrowed someone's C40 charger and it had no programmable absorb time, so it was stuck at 1 hour- which is too short for any decent sized bank. Can you change your absorb time to 2-3 hours and then measure the SG once it hits float and see whether they're really fully charged?

Charger doesn't have a timer - changes from bulk, to absorb, to float based on bank voltage.