Trojan L16 Battery issues

learaviator

I have 12 L16 Trojans, 370ah, 8 JA Solar 285W panels, 24 volt system, Magnum MS4024-PAE inverter and a Flexmax 80 Charge Controller. Batteries are 5 years old and the same battery in each bank is bad. I have always fought SG issues in those batteries and can't figure out why. It is the third battery in line in each bank. I wonder if I should have been rotating battery positions? 

I now will be replacing my existing panels with 8 new REC 330W panels and adding a second Flexmax 80. Really tired of dealing with servicing batteries and cleaning cables.  Can't decide between 12 more SEALED L16's or 4 Simpli-Phi lithium batteries. Any thoughts on the SG issues or switching to Lithium? 

BB.

Assuming that you are using distilled water (or filtered rain water after a the first showers have cleaned the roof), you have clean/tight terminals, good cables, and are monitoring SG over time...

Yes, there have been a few people here that have seen their FLA batteries seemed to be positionally sensitive in series strings.... And they have addressed this by "rotating positions" of the batteries once a year. (I have no idea why this was happening to them--No obvious environmental issues such as batteries next to windows/hot engine/etc.).

I always like to go back to basics... And see what the charging current is. Typically 10% to 13% rate of charge is probably optimum for FLA batteries. 5% can work for weekend/emergency backup. And >13% (to 20% or 25% max) can work (highly suggest a remote battery temperature sensor to keep the bank from overheating).

Also, confirm that the solar array is wired for Vmp~60 volts "optimum" minimum for your 24 volt battery bank. And your array is mostly in the sun without ANY significant shading during most of the day.

Don't know what your existing array wattage is, but based on rate of charge, the suggested array sizes would be:

• 3 * 370 * 29.0 volts charging (4 series * 3 parallel strings of batteries) * 1/0.77 panel+controller deratings * 0.05 rate of charge = 2,090 Watt array minimum
• 3 * 370 * 29.0 volts charging (4 series * 3 parallel strings of batteries) * 1/0.77 panel+controller deratings * 0.10 rate of charge = 4,181 Watt array suggested Full time off grid minimum array
• 3 * 370 * 29.0 volts charging (4 series * 3 parallel strings of batteries) * 1/0.77 panel+controller deratings * 0.13 rate of charge =5,635 Watt array typical cost effective maximum array
• 3 * 370 * 29.0 volts charging (4 series * 3 parallel strings of batteries) * 1/0.77 panel+controller deratings * 0.20 rate of charge = 8,361 Watt array near maximum array

Don't know what your daily loads are (by season), or where the system is installed (near Denver?)... What is your typical discharge cycle (discharge often below 50% or below 20% State of Charge)? Or do you shallow discharge a lot (less than 10% or so discharge)?

Not that this would help the batteries--But this is a pretty large battery bank (1,110 AH @ 24 volts)... Even a 10% rate of charge is 111 Amps... Not a small amount of current--An an 80 Amp charge controller would be around (80a/1,110ah) 7% rate of charge (if you currently have just one Outback 80 amp controller. If so, then adding more charging current/array/charge controller would probably help battery life/SG.

Another option... Look at a 48 volt battery bank (and AC inverter/backup AC charging with genset)? That would get you down to (for example) 8s * 2p for (16x batteries) for a 740 AH @ 48 volt battery bank... And a 10% rate of charge would be 74 Amps (just one Outback 80 amp controller).... Especially if you plan on "growing" the system (large inverter, larger battery bank storage, larger array, etc.).

-Bill

JRHill

learaviator said:

4 Simpli-Phi lithium batteries...  switching to Lithium? 

Absolutely recommend. They won't care about the lower charge rate and have zero (or .1 hour) absorb requirements. They charge AND discharge more efficiently. Your required maintenance time will approach zero as well. Very few downsides like absolute fool proof High and Low voltage protection and low temperature protection if applicable. Your biggest decision is whether to go 48v now and that is recommended before you buy the batteries as you do NOT put 24v PHIs in series to make 48v later.

I've had mine for 2.5 years and all I've done is fine tune the programming for our needs. I don't charge them to full and they rarely get below 45%. They have an easy life and should (hopefully) be the last batteries I buy.

Dave Angelini

Strings of flooded batteries, often not wired correctly, are probably your problem. Post a picture if you want to solve this.

learaviator

Dave Angelini said:

Strings of flooded batteries, often not wired correctly, are probably your problem. Post a picture if you want to solve this.

I contacted Trojan about this and they said it was good. I think rotating batteries in the strings might have fixed it. Going to four 3.8 Simpli-Phi 24volt batteries now, and an FM100 instead of a second FM80. 

littleharbor2

If the problem battery is always in the middle string you should run Bus Bars and individual, equal length, cables from each string to the bus bars

JRHill

He'll definitely be using then with the PHIs,