Check my 24v settings please

[Scott Martinez]

Hi, I have eight T105 setup in series/parallel for 24v. Per the data sheet I have a bulk charge setting in my charge controller at 29.1, float 27.1. For the health and safety of the bank, I have the cutoff set 24.2v or 50% state of charge. Is that too conservative? When at rest, the bank measures about 25.5v fully charged.

https://www.trojanbattery.com/pdf/datasheets/T105_Trojan_Data_Sheets.pdf

 

[snoobler]

Why did you decide to not follow Trojan's recommendations?

Bulk should be at 29.64
Float should be at 27.00

Your bank voltage depends on your loads. A fully charged bank under a heavy load could be pulled down to 24.2V even when at a very high state of charge. Do you want your inverter tripping off at 80% SoC?

A better option is a quality battery monitor that counts current used. The Victron BMV-7XX units also consider Peukert's effect and adjusts SoC for current higher than the C20 value.

Do you have temperature compensation active? Unless FLA batteries are stored in a controlled environment, temperature compensation should be used.

When at bulk/absorption voltage, you should check all your 6V batteries to confirm that they are all at very similar voltage levels. I wouldn't want them off by more than 0.1V or so... new batteries should be even closer than that.

Read and re-read and learn these:

https://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf

Trojan Battery | Battery Maintenance

The key to achieving optimum performance and long battery life is to follow a regular care and maintenance program. Read our tips for high performance battery maintenance.

www.trojanbattery.com

Trojan FLA have the potential to provide a long service life, but that depends on you putting in the work.

 

[Scott Martinez]

I didn't provide enough information. The float is set for 27v and the bulk for my charge controller maxes out at 29.1v. I do not have an option at the moment to equalize per Trojan's recommendations. -So not ideal. I'm using an MPP Solar 2424 unit mostly keep the batteries topped off for emergency use, and providing active solar to about 500 to 800 watts of load on it's inverter output. I probably should have went with a dry cell solution when I started this, but am wanting to get the 5+ years out of what I have. The batteries are in a well ventilated controlled environment.

I guess I was mostly wondering what I could get away with for cutoff in an emergency to say run the fridge, or possibly cycle the forced air gas furnace. The default of the charge controller/inverter is 23.5v or about 30% capacity on the data sheet.

The batteries all seem to be within .1 of each other. I am not using a BMS at the moment, but do check with the multi-tester when checking the water monthly.

I could take the batteries offline and equalize either one or a pair at a time. Is there a resting voltage or some indicator to let me know when this should be done?

Thanks for your wealth of information on this Snoobler.

 

[Scott Martinez]

I Just read the info on the data sheet about equalization...

 

[eXodus]

It's to conservative in my experience, I'm running T105 in Golf Carts regular down to less about 30% and they still die of old age then loosing capacity somewhere between 6-8 years.

It's not that critical when you don't do that every day. At 50% a T105 does like 1000-1500 cycles - so depending if you use those in the 6-8 year lifespan - you can discharge deeper.

So see - how many days you would discharge the battery a year. At 180 working days a year - (and not every day is a 50% day) the batteries don't have capacity issues, until one shorts out.

 

[Scott Martinez]

It's to conservative in my experience, I'm running T105 in Golf Carts regular down to less about 30% and they still die of old age then loosing capacity somewhere between 6-8 years.

It's not that critical when you don't do that every day. At 50% a T105 does like 1000-1500 cycles - so depending if you use those in the 6-8 year lifespan - you can discharge deeper.

So see - how many days you would discharge the battery a year. At 180 working days a year - (and not every day is a 50% day) the batteries don't have capacity issues, until one shorts out.

Thanks for the real world information. I think I'll set my cut off at about 23.6 while it's sunny and they'll get a full charge the next day. I'll watch the log a few days to see how far down they actually go down to. I'm drawing 200 to 700 watts depending on what the family is using with the inverter as of now. I still don't quite understand the math on these. If I understand correctly, I can get 25 amps for seven hours x 2 since I am running 8 of these at 24v. I'll do SBU till the weather turns on the output, then run it SUB. I'm am solar only for now, but will add the utility if a wind storm is forecasted.

 

[snoobler]

Again, better to get a quality battery monitor that can report an actual SoC based on battery rated capacity, current and actual capacity used.

 

[Scott Martinez]

Again, better to get a quality battery monitor that can report an actual SoC based on battery rated capacity, current and actual capacity used.

I am not familiar with battery monitors since I've only seen them used to monitor cells in the DIY power walls. I've just been checking each 6 volt battery at rest when checking water monthly. Is there something I can get for my lead acid bank worth investing in?

 

[snoobler]

Are you also checking your SG and logging it?

Battery monitors are very common even with lead-acid batteries. They involve a shunt installed at the battery (-) through which all charge and discharge current passes. The device counts the net current and direction and provides an estimate of the SoC based on the input total bank capacity.

They're spendy, but I violently recommend the Victron BMV-7XX.

700 is the base model
702 allows for battery temperature monitoring OR for a second battery voltage.
712 is the 702 but with bluetooth and VictronConnect access (highly recommended)

You enter all of your battery bank parameters and charge termination criteria, and it maintains a running count. When it detects that the full charge criteria are hit, it synchronizes to 100%.

 

[frodo2222]

Are you also checking your SG and logging it?

Battery monitors are very common even with lead-acid batteries. They involve a shunt installed at the battery (-) through which all charge and discharge current passes. The device counts the net current and direction and provides an estimate of the SoC based on the input total bank capacity.

They're spendy, but I violently recommend the Victron BMV-7XX.

700 is the base model
702 allows for battery temperature monitoring OR for a second battery voltage.
712 is the 702 but with bluetooth and VictronConnect access (highly recommended)

You enter all of your battery bank parameters and charge termination criteria, and it maintains a running count. When it detects that the full charge criteria are hit, it synchronizes to 100%.

I'm having a issue and cannot afford the Victron battery monitor..the one I got asks for the High Voltage and low voltage to figure out the % but not the capacity..ANY Ideas as to what that actual number is? Based on the numbers you put up for trojan
Bulk should be at 29.64
Float should be at 27.00