New battery replacement

[asdex]

I'm replacing my 24 volt 420ah battery bank soon. They are 6 volt lead acid batteries. I am looking at lead carbon and lithium. How reliable is the midnite classic in charging lithium batteries to 100%? I am also adding 4 x 410w solar panels and a 50 amp Epever tracer controller. These panels will face north east. My existing panels are 6 x 320 watt facing true north. Both these systems will charge the same new battery bank. Does this sound like it will work OK? We need more capacity and I'm finding it hard to get matching panels to the six I have, plus we miss alot of morning sun.
Thanks,

[ClassicCrazy]

Other options to consider are
Replace battery with 48 v and get more power out of existing Classic.
Replace all the PV with  new ones of  same type that will match each other making it easier to match strings.
Personally if I wanted to add another controller I would stick with another Classic that could integrate with the other one via Follow Me .
Or just for the better monitoring options ( and proven reliability).
You should check with Lithium battery suppliers because the internal BMS will determine some of the charging scheme and not sure how it would handle two different controllers that aren't on the same page talking to each other for Absorb, Float , voltage variations, etc.

Larry

[asdex]

OK, thanks. Will have a think about all that. Its maybe a bit drastic to replace all my panels. Possibly a second classic and separate array. To go to 48v I would have to replace a perfectly good Outback inverter.
cheers

[ClassicCrazy]

OK, thanks. Will have a think about all that. Its maybe a bit drastic to replace all my panels. Possibly a second classic and separate array. To go to 48v I would have to replace a perfectly good Outback inverter.
cheers

Yes I understand it is hard to replace a good working system.  Difficult choices to make during upgrade.
The PV panels is something I didn't consider either when I put my system up. Looking back it would have been smart to get at least one extra for spare just in case .
Of course PV panels were very expensive at one time , the the price came down and down and down . That makes used one not worth as much . And batteries - always the hardest decision.
Lithium is looking more and more like the best choice - if you consider the amount of available power you can get a smaller capacity than lead acid and have the same amount of power. With lead acid if you want longevity then you only take out 20% of capacity .
I may be upgrading one of these days - my biggest problem with lithium is I don't have a good warm place for them in winter yet. And not good to be charging them below freezing.

Larry

[Steve_S]

I transitioned from 24V/856AH FLA to 24V/910AH LFP (LiFePO4) and just about to complete finalizing my LFP bank when I install the last 280AH Pack bringing the LFP bank up to 1190AH/30.464 kWh.  That will give me, 3X 24V/280AH + 1X 24V/350AH all together.

The 280AH Packs are simple 8S Configuration using 8, EVE 280AH LFP Cells.
Operational Range is 2.500-3.650 volts per cell or 20.0-29.2V with Nominal Power being 3.200V per cell.
Operational Temps are 0°C to 55°C, some chemistries allow for charging below 0C.
Typical Discharge Rate for ESS (Energy Storage System) Grade cells is 1.0C and 0.5C for Charge Rate. 
- IE:  280AH Cell = 280A Discharge for 1 hour and 140A Charge Rate MAX.

My Midnite Classic-200 Settings: (not the usual)
Absorb: 28.2 for 15 minutes
Equalize: OFF
Float: 27.9V
MIn Volts: 22.0 Max Volts: 28.7
Rebulk Voltage: 27.7
End Amps: 14A

This get's the bank charged to full with high amps (Constant Current) and then float (Constant Voltage) tops off so the cells are on average between 3.475-3.500. I am running 7/24/365 so float is used up by the Inverter + provides whatever the packs will take to top off.

NOTES:
- I use a Chargery BMS8T-300 Battery Management System on each battery pack, with a 300A DCC (Solid State Smart Contactor).  This BMS has "Passive Balancing" which is used only during CHARGE.
- I also use a QNBBM-8S "Active Balancer" on each battery pack.

LINKS:
Chargery BMS8T:  https://www.chargerystore.com/index.php?route=product/product&path=20_26&product_id=86
Chargery DCC-300: https://www.chargerystore.com/index.php?route=product/product&path=62&product_id=66
Deligreens QNBBM-8S: https://deligreen.en.made-in-china.com/product/WveQLpcrgqYh/China-24V-Lithium-Ion-8s-Qnbbm-Battery-Active-Equalizer-BMS-for-Battery-Protection.html
*NB Chargery link MAY error pending on browser being used.

ATTACHED is the Luyuan Basic LiFePO4 Doc on assembling your own battery packs and an LFP Voltage Curve Chart, prepared by Yours Truly.

Also I will echo what ClassicCrazy stated above, you'd be far better off getting a second MidniteClassic and using Follow-Me to interlink them.  I am now looking at doing this and adding another Classic-200-SL along side my existing 200 to run a second array.  I am PONDERING this and another option as my current C-200 needs a Refresh and once I add the cost of a Refresh (If still available and practical) + new C200SL it may be more than other products that are available.  The Practical Issue is I am 100% offgrid and cannot go without an SCC to keep me running while someone does a refresh for however long it takes.

Hope it helps, Good Luck
Steve_S

PS:  Much more details & info at https://diysolarforum.com/threads/my-diy-off-grid-cabin-setup-in-ontario-canada-24vdc-120vac.1484/

[ClassicCrazy]

good to hear those lithium cells are working out for you Steve.
I may make a switch one of these days .
since you have 15 minutes absorb time and 14 ending amps - which usually comes first ?

Larry

[asdex]

I'm a bit wary of the lithium batteries as their quite technical but often my batteries don't get fully charged for a few days and it think this isn't a problem for them. I'm having trouble finding info on lead carbon but the send classic might be best as it would simplify setting up two solar arrays. I think my main problem with batteries is getting them fully charged each day as the run a fridge and freezer overnight.

[Steve_S]

good to hear those lithium cells are working out for you Steve.
I may make a switch one of these days .
since you have 15 minutes absorb time and 14 ending amps - which usually comes first ?

I am running 4 packs ATM so End-Amps doesn't really work and I am Not taking them above 3.5V per cell.
I am so pleased with these compared to Lead, they charge faster and deeper my only outstanding issue is charging in December, just not enough panels for the low Sunhour Days.  Sadly there are no great places like Santansolar up here in Ontario Canada.

Right now in March, I am hitting FLOAT by Noon, I rarely saw that by noon with my Lead Battery Bank.

@asdex  An FYI:  IN Winter I have to use Genset to charge occasionally.  4 hours of charging from my L5:30 port (120V/30A) plug on genset through my Samlex EVO Inverter/Charger set to charge at 80A gives me 2 days + run time, from 40% SOC to full takes roughly 7 hours of genset time.  Now while Charging, I am also running Pass-though power to home concurrently which does affect the charging a bit.

24V/420AH Lwad you are currently running only provides you with an actual 210AH of useable.

8x 280AH LFP Cells makes 24V/280AH/7.168kWh battery pack.
Cost for Grade-A (Factory Matched) $1,016.00 USD delivered DDP
Cost for Bulk Grade-A (Unmatched) $ 729.00 USD delivered DDP
*DDP = Duty, Taxes & Fees included.  (Prices from Luyuan Tech)
1X  8S BMS from $150USD and up pending on features
1X MRBF Fuse (BlueSea (Bussman/Eaton)) $30 USD +/-
1X Box or Casing your choice many possibilities.

Will last 3500 Cycles, no maintenance, watering or other nonsense.  LFP is the safest chemistry, no catching fire & exploding.  Funny how noone mentions Lead can do that too...  Shhhh  it's a zekret !

A NOTE ON LEAD & Variants
Many Battery companies have changed over the past few years.  Merger's & Acquisitions have been crazy and it has not been good for Joe & Jane consumer because quite often the Bean Counters of the Investment firms have chopped quality to hell.  General Consumer batteries have degraded as a result.  IF you are determined to stick with ANY form of Lead Stick with KNOWN NAME BRANDS for Solar such as Rolls Surette, Trojan etc and keep away from Experimentals / New Products from "new" companies and wild claim products (some are as bogus as a $3 bill).

My Lead Bank uses Rolls S-550's / now S6-L16-HC which are selling for around $400 ea and I have 8 of them. 
Rolls Lead $3200 for 428 useable Amp Hour or TWO LFP 24V/280 as noted above for $1216 ea X 2 (in Parallel) = $2190 for 560AH useable.  I'd use a better BMS around $225 ea though, so +$150.

[asdex]

That sounds pretty goo to me. I'll do a new wattage usage plan to see if 430ah is needed still.
I have some lithium batteries in mind https://www.trademe.co.nz/3011233224
I'll still add some more NE facing panels and double check if I could use my existing classic or not. I've never seen it above 60amp charging current.
Cheers,

[asdex]

Actually these look better as they have a meter in them.

https://www.trademe.co.nz/3012679002

Can the classic be set to limit charging current?
and does it limit pv current to 96 amps even if the panels are producing more?
Thanks

[ClassicCrazy]

Actually these look better as they have a meter in them.

https://www.trademe.co.nz/3012679002

Can the classic be set to limit charging current?
and does it limit pv current to 96 amps even if the panels are producing more?
Thanks

Yes and yes to your questions.

Larry

[Vic]

asdex,

Here is how to Limit battery charge current with Classics:
http://www.midniteftp.com/support/kb/faq.php?id=37

And,  Classic 150s can have an OUTPUT current (to the battery) as high as 96 A Maximum only with 12 V batteries,  and within a certain range of PV String voltages,  as depicted here:
http://www.midnitesolar.com/pdfs/classicPowerChart.pdf

SO,  as Larry noted,   Yes,   and  Yes  ...    Vic

[asdex]

That sounds good. I'll probably go for the 24 volt lithium battery once I telly up ah's needed and either buy a second classic for the new array or just use the old one and replace all my existing panels.

[asdex]

I've been looking at LiFePO4 batteries and find the recommended charge rate is around 40 to 60 amps. Is this normal? One had a recommended charge current of 20amps max 50amp. At that rate it would be had to fully charge on solar.
Thanks,

[ClassicCrazy]

I've been looking at LiFePO4 batteries and find the recommended charge rate is around 40 to 60 amps. Is this normal? One had a recommended charge current of 20amps max 50amp. At that rate it would be had to fully charge on solar.
Thanks,

You have to look at the battery specs . Some are C1 charge rate ( capacity times 1)  and some may be C2 .
It just means how much power you can put into the battery at one time - you still can charge at slower rate until the batteries are full.

Larry