Battery upgrade time

Diesel Pro

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Jul 21, 2021
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8
Off grid cabin-away 99% of the time. Magnum 4k inverter, Midnite solar Classic 150 controller. 4 solarworld 320w panels on a stationary pole mount

I have a 24v 430ah wet battery bank that is going on 5yrs old and pretty much cooked. Looking to replace with lithium and be done with it. I very seldom use much if any of my capacity. Hunting season we run the lights a little and TV for an hour or two. Maple season run a small transfer pump short duration. On one occasion I ran my R.O. off teh cabin power but usually use my Honda EU2000i for this because after a few hours the battery bank will be depleted. I've been looking at various options. I run Ionic batteries in my boat and really like their APP to see SOC etc on the BMS of each unit. Ionics are pretty darn expensive though. Been looking at Big Battery for a nice packaged unit that would take the place of my battery "box". The Big Battery Hawk series seems to fit the bill. 200ah range should match what I have pretty close but I question if it may be more practical to back it down to even 120ah. If demand somehow grows add a second unit paralell.


I'm not always the one to check in so I really like the idea of having a heads up SOC so I can send anyone in and they can see that the battery bank is 9x% full etc. Even snap a pic of the display.

Suggestions?
 

iamrich

Solar Addict
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Dec 17, 2020
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767
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Elgin, Texas
Is cold an issue? LiFePo doesn't like the cold, especially unsupervised charging in the cold. I wonder if it might not be a better idea to buy a 4 pack of 100ah 12v AGMs and be done with it for another five years?
 

Diesel Pro

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Jul 21, 2021
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I do have a small propane heater and maintain temp above freezing, but I would want low temp protect to be safe in case the pilot goes out. I've become so fond of the lithium now that I put them in my boat. With the lead acid I end up changing my charge profile seasonally because short winter charge time and if I get an overcast day it really pulls them down. That Magnum inverter seems to have a pretty fair parasitic load.

Realistically, I could and probably should just shut down the system most of the time and only use on demand, but I do have a small fan that moves air from room to room that is nice to have.
 

rhino

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Jun 6, 2020
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Minnesota
You can get DC fans so you wouldn't need the inverter if that is what you ultimately would prefer.
 

rhino

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Jun 6, 2020
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493
Location
Minnesota
Also note that if you search for "bigbattery" on here you will see some unhappy campers.
 

Diesel Pro

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Jul 21, 2021
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DC fan would be an option, BUT I have my wiring all behind drywall or wood.

Will's videos on Big Battery got me started, especially the form factor, but yes I have seen some issues with them. I need to dig deeper. Seems like a lot of customer service issues.
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
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Oct 29, 2019
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5,435
Location
Rural NE Ontario Canada
From 430AH of Lead you only get 215AH when in new condition. I jumped from a Rolls Surette bank of 428AH gross to 1190AH LFP. Using a Midnite Classic 200 even. I bought one prebuilt out of China (ShunBin nightmare written up here), after that I built my own packs using EVE-280AH cells. There is no turning back.

BTW, I use a recovered RV Furnace (direct vent) Suburban-NT20S from a 5 year old wreck complete with all fittings and thermostat & dual tank regulator for 350. Electronic ignition, no pilot and runs off 12V, so I have a 12V battery small SCC and 100W Panel just for that, works peachy ! Sure beats the old Duo-Therm I had with a Pilot Light.... that thing was cursed I'm sure. Call around the RV/Trailer repair shops, especially ones where they tear them down.

My Midnite 200 Profile for LFP
All equipment MUST BE Voltage Corrected & Calibrated (VERY IMPORTANT) see link in my signature on how to do it.
Divide Values X2 for 12V. Multiply X2 for 48V.
Absorb: 28.2 for 15 minutes (3.525vpc) (some call this boost)
Equalize: OFF
Float 27.9V (3.4875vpc)
MIn Volts: 22.0 (2.750vpc)
Max Volts: 28.7 (3.5875vpc)
Rebulk Voltage: 27.7 (3.4625vpc)
End Amps: 14A (*1)

(*1): End Amps is calculated from the Highest AH Battery Pack in a Bank. IE: 200AH X 0.05 = 10A 280AH X 0.05 = 14A.
NB: Victron Forum discussion says EndAmps = TailCurrent
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.

** Coulumbic Efficiency for LFP is 99%
 

Diesel Pro

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Jul 21, 2021
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I've done some searching on Big battery, unfortunately those are pretty common search terms. I see a bit of discontent, but nothing widespread or epidemic-or am I missing something?
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
Joined
Oct 29, 2019
Messages
5,435
Location
Rural NE Ontario Canada
I've done some searching on Big battery, unfortunately those are pretty common search terms. I see a bit of discontent, but nothing widespread or epidemic-or am I missing something?
Sadly there are many varied issues with Big Battery over time, they are trying and improving but not there yet. Now some of it is their own fault and some wasn't, mostly how much demand there is overwhelmed them and they "rushed" and got sloppy (haste makes waste). There are currently a couple of threads I've seen on the "Hawk" batteries ?

These search results are sorted by date with title only search for "Big Battery"
 

niktak11

Solar Enthusiast
Joined
Mar 14, 2021
Messages
90
I have a 48V HSKY from big battery. Aside from some quirks with the BMS, it's a very well made battery. It also seems to be their most power dense lifepo4 battery.
 
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