SCC settings for LiFePO4 battery (new approach for me)

[Sojourner1]

All 12 vdc loads are seen on the GBS display, fridge & interior fans, furnace, electric awning, slides, bigfoot levelers, water pump, misc 12v lights all register on the display when in use.

 

[Sojourner1]

Randy, how much solar do you have?

 

[RandyP]

300 AH battery (Much smaller system than yours) and about 645 watts solar for now.

 

[RandyP]

For what its worth, these are the setting I've been using for the past 5 years. Magnum 3000w hybrid inverter/ charger, Magnum PT100 SCC, ME-ARC50. The scc follows the exact settings that the inverter/ charge is set for. When on occasion I use either the Honda eu2200i or a eu2000i generator I'll set incoming loadshare to 15a and charge at 100a.

If on shore power I'll turn off the charger (on the inverter/ charger) and use only solar to top off the batteries and then float , depending on the furnace run time during the night nighly consumption is 25-35ah or 5-7% DOD.

The following parameters are for programming the ME-ARC Version 4 advanced control.
Setup 02B LBCO Setting: Volts = 12.0
Setup 03C Battery Type: = Custom
Set Absorb Volts: = 14.1v or 14.2v (depending on season)
Set Float Volts: = 13.6
Set EQ Volts: = 14.1
Set EQ Done Time: = 0.1
Setup 03D Absorb Done Time: = 0.1 (minimum)
Setup 03E Max Charge Rate: = 100%
Setup 03G Final Charge Stage: = Float

Thanks for the battery charging settings.

 

[RandyP]

-I'll be using a Victron smart SCC, will use the settings V absorb 14.2, V float 13.8, and a return from float to Boost as close to 13.8 as possible.
-I'll set the Magnum Hybrid MHS inverter/charger to absorb 14.2 v, float 13.2v so the SCC will perform the battery top off maintain function as long as the solar is good.
-Considering an occasional (maybe once weekly when boon docking) SCC or Magnum 14.4v equalize charge to 14.6v maintained for 15-20 minutes to force a BB cell top balance with the BB BMS.

 

[RandyP]

-I'll be using a Victron smart SCC, will use the settings V absorb 14.2, V float 13.8, and a return from float to Boost as close to 13.8 as possible.

This keeps me in the manufactures (BB) suggested charging range. 14.2 v being the lowest Bulk/Boost charge BB specifies and 13.8 v being the highest float charge BB specifies. Thereby operating the battery in the 13.8 to 14.2 bandwidth when the sun is plentiful. Meets my desire to operate the BB batteries in a narrow bandwidth to optimize SOC at the end of the solar day, and keeping the Boost voltage as low as possible to extend the life of the batteries

-I'll set the Magnum Hybrid MHS inverter/charger to absorb 14.2 v, float 13.2v so the SCC will perform the battery top off maintain function as long as the solar is good.

These settings are also within the BB recommendations for charging the batteries I have. Buy allowing a low float from the inverter/charger, the top end of the battery charge will be completed by the SCC in the sunlight. Inv/Charge will only be done when shore power is available or when the sun does not keep up with my battery use and a generator is required.

-Considering an occasional (maybe once weekly when boon docking) SCC or Magnum 14.4v equalize charge to 14.6v maintained for 15-20 minutes to force a BB cell top balance with the BB BMS.

BB CEO Dennis is quite adamant about charging the BB bats to 14.2-14.6 v and holding them there for 15-20 minutes per battery string to top balance the batteries with the BMS BB has provided in the 100AH 12V battery. I believe this is a passive top balance. Then allow the batteries to float at 13.2 with the Magnum in the dark or 13.8 with the SCC if the sun is out.

 

[Sojourner1]

When you say

Then allow the batteries to float at 13.2 with the Magnum in the dark or 13.8 with the SCC if the sun is out.

are you on hookups? In my opinion 13.8v float is still a little high even in an daily use, 13.6v is plenty.

 

[RandyP]

It's all about the bandwidth the SCC works in. The sooner the SCC starts a Bulk charge, the sooner the battery is recharged to 14.2 v and the higher the battery SOC is for night time use. This re-Bulk charge would only happen on sunny days when there is sufficient load on the dc panel to reduce the battery voltage below 13.8 volts with max solar float assist (more power demand than the solar can provide at a 13.8v float level). 13.8 v is within the manufacturers (BB, cylindrical LiFePO4 cells) specs for float voltage. Hookups are only with a Honda 2000i inverter/generator when the solar cannot keep up with use. The Honda 2000i can run the AC until it runs out of gas with help from the Hybrid inverter and 12v battery for AC compressor startups inrush current.
I only have 300 AH 12 V Battery to work with if the battery is at 100 % SOC. If sun were to not shine for three days, I might need the Honda 200i to bring the battery back up.

 

[RandyP]

are you on hookups? In my opinion 13.8v float is still a little high even in an daily use, 13.6v is plenty.

We both have LiFePO4 batteries.
-My battery is composed of Cylindrical cells.
-Yours might be Prismatic cells.
There might be a difference in battery charge voltages because of the difference in cell types.

 

[Sojourner1]

The great thing about lfp is you can choose what you believe to be best with manufacturer recommendations or enough researching.

I understand what your saying I been living off my system a long time now with daily use of 175-250ah. As of today it's been 1,881 days the system has been on, out of that 1,705 have been boondocking off of solar. Occasional hold over charge from the Honda generator during winter months to raise the SOC, I don't fully charge the batteries with it just live in a PSOC range. The 176 days that have been on hookups I turn off the charger (inverter/ charger) from 120v and only use solar but leave the inverter on incase theres a power outage in the rv park, what minimal 12v loads there are are covered by solar and top off the batteries, "floating" at 13.6v.

Here are #s from previous years use/ production.

Day 1 installed 4/13/16, fulltime use.

Days boondocking
2016_ 200 of 261 days
2017_ 365
2018_ 365
2019_ 344 of 365 days (rv repairs)
2020_ 282 of 365 days. (Covid, moved 5th wheel closer to crews.)
2021_ 149 of 160 (as of 6/12)

As of 6/12/21
1,705 (boondocked) of 1,881 days.

 

[RandyP]

Thanks for the kind reply and explanation of your electrical system use. Very Impressive record keeping. What is 'Hours on Work time' entry. Just curious.

 

[Sojourner1]

That is the time SCC wakes up in the morning till it goes to sleep for the night.

I forgot to add the generator averages about 24 hours total use time in a year.

 

[RandyP]

I see that you use a battery chemistry LiFePO4 with Magnesium added to the Cathode. "EPS uses batteries made by GBS. GBS, like LiFeBlue and Relion, use Lithium Iron Phosphate (LFP) chemistry. However, GBS has an added Manganese to the cathode material and are referred to as LFMP cells."

 

[Sojourner1]

I've been extremely happy with them. LFMP I think can handle a little more draw than LFP over the long run but I could wrong.

Heck, I'm sitting here in the National forest right now with air conditioner going off of solar/ batteries for the past 1.5 hours cooling the rig down some.

 

[RandyP]

There's a hot spell passing over the Coast of CA. I'm sure it will make its way thru the West. You might get a chance to use the AC more than a few hours a day.

 

[Substrate]

The great thing about the GBS cells is that their terminal connections reduce the possibility of rotational torque loosening them. I especially liked the purple plastic snap on covers, as that meant I didn't have to diy some sort of top protective plate.

I did loosen the compression straps and re-align the dimples on the cells so that they would mate together better. That way, if the cells did try to align themselves into the little dimples, it wouldn't put any stress on the bus-bars.

The dash of manganese turns them into LFMP, but they are/were also favored by some for EV use, since in the case of a crash and resulting cell damage, the electrolyte is reputed to have addititives that are less toxic than others.

 

[RandyP]

Another look at narrow bandwidth solar charging at a moderate max SOC setting.

 

[grizzzman]

Nope, the generic mppt Genasun for LFP is hard coded at 14.2v. If one has a more specialized need then they can simply custom order for a different voltage limit. Just a CC/CV. Nothing to set. Just hook panel and battery up properly and done. No other concerns.

They don't offer large-current controllers, although I suppose if one was in love with them, you could do multiples on a single battery ... but errr.. yeah that's a different decision to make.

Normals - heh, no that means people more interested in camping or whatever with their batteries than trying to figure out "Wait, you guys spent 5 years arguing about something called top-balancing? Isn't that vertigo? You guys need to go to the doctor!"

You may find this info a bit entrusting.
"Many “charge controllers” sold with the word “lithium” in the accompanying pamphlet are simply unusable, some to the point of being purely destructive. Some of the most infamous examples are the “lithium” versions of the Genasun GV-5 / GV-10 solar MPPT controllers: these little marvels of engineering and efficiency respectively deliver up to 5A and 10A at a steady 14.2V output… forever! There is no way to adjust anything and no way to turn them off without seriously hacking the circuit boards. These are the best lithium plating controllers on the market. Genasun exited the lithium arena many years ago now, but they keep marketing some of the garbage technology that was destroying their batteries."