How to build a LiFePo4 battery bank.
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Mar-31-2021 08:39 AM
this video is pretty decient on how to do it, what is missing is some sort of case. the Prismatic cells like to be clamped togeather slightly if you going to be running high currents. I have seen cases made out of wood with threaded rod providing the pressure, and several other ways also.
also I am not a fan of the BMS he uses, there are lot better ones, but he explains he needed the high capacity one to do a torture test on the cells.
so he builds a 280Ah 12V battery in this video, if you need more you could build 2 and then just tereat them like two 12V batterys and run them in parralell, or just build it all in series and do a 24V set up if you want to do the higher voltage systems.
280Ah LFP build
Steve
2016 Cougar 330RBK
1991 Slumberqueen WS100
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Oct-26-2021 06:47 AM
time2roll wrote:
Not really an expedition vehicle. Not likely to be in Canada in winter.
dont lump all of canada into thoes cold winters haha. my normal day time high in the winter is 32 degrees but I onlu have to drive a short distance to drop that significantly. on the island if you around victoria the normal day time high is 42 in the winter, but if we go to winnipeg then it could be -40
Steve
2016 Cougar 330RBK
1991 Slumberqueen WS100
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Oct-26-2021 01:25 AM
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Oct-25-2021 06:54 PM
I assume it is good to 20f, maybe lower, and covers about the worst I would see. Could be they never activate. Glad to know they are there to buy some time so as not to create an immediate panic to roll out.
Not really an expedition vehicle. Not likely to be in Canada in winter.
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Oct-25-2021 06:39 PM
time2roll wrote:
Currently I have it set for 35F on, 45F off. Will see how it goes. Thinking about going 38 to 42 or similar.
Not sure it is a huge deal to be exactly something to be perfect.
With ambient to 37F, What were the settings for on and off when you saw the 44F low at the battery? Did the heaters come on at all?
Good that it all worked.
on Ford E350-460-7.5 Gas EFI
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2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.
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Oct-25-2021 04:48 PM
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Oct-25-2021 03:21 PM
Any idea how cold it got and what the high temperatures were during the day time? I'm glad it has worked out so well.
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.
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Oct-25-2021 12:59 PM
Absolutely no issues. Could have completely ignored any battery or power related activity and just focus on everything else.
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Oct-08-2021 06:06 AM
I've posted before that all my cells (20) have a temp readings, I can see compartment temp and know what outside ambient temp is, even when I was in a strech of nighttime temps of 13-17f, daytime temps 37-45f none of the cells ever dropped below 40f by morning and during the day would warm up to low 50f. Even having a small load 7-9a on the pack all the time will not warm the pack.
I would let the batteries charge at what ever the solar would produce and being winter that's not awhole bunch till 9-10 when the sun would get some height and be able to hit the front panels along with the panels down the door side of the 5th wheel.
If needed and throwing a hold over charge of 100ah (.2c charge rate) from the inverter/ charger & generator with the cell temps at 45-50f seems not to effect the batteries performance yet after 1,800 partial cycles.
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Oct-07-2021 08:10 PM
I don't know if the -10C stop discharging is a good idea. What if some unusual night the heat pads can't keep up and the batts get to -12C? If the cells can take -20C, and the BMS can be set there why not use that? What does it do for you not to use all the margin it could have?
Worst thing is no 12v all of a sudden. Now the heaters won't work except from the truck's starting batt, or the gen (night time event) -20C setting would give you more margin to still have 12v.
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.
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Oct-07-2021 07:25 PM
Not sure it is a huge deal to be exactly something to be perfect.
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Oct-07-2021 07:09 PM
time2roll wrote:StirCrazy wrote:My BMS cuts charging at 1C and discharge at -10C.
I was thinking about this at work, and I may be wrong... it all depends on the BMS and how it is configured for the internal pass through of power. if it is just one line then the cold weather will kill the whole battery, but if they spent some money and used diods and did two internal paths then you could controle charging and discharge independently. I guess we would have to dig into the BMS construction to know for sure...
Steve
What would you set the Tstat relay temp at to turn on the heat pads so there is time as the temp drops to arrest the fall in batt temp before it gets down to -10C and turn it around to climb back to the Tstat set temp?
You need to know how long it takes for the heat pads to have enough effect so they get turned on in time. If you leave them on at some "low" then you need to learn how much they can do vs ambient to keep above -10C or 1C as needed.
Thinking of a desert scenario down that way where it might get cold at night but you want the batts at 1C or better at sunrise so the solar can start its work.
-10C isn't all that cold so not much margin if the temp drops fast in the night. Can the heat pads counter a fast temp drop like that? Guess you will find out and adjust as required.
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.
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Oct-07-2021 06:40 PM
StirCrazy wrote:My BMS cuts charging at 1C and discharge at -10C.
I was thinking about this at work, and I may be wrong... it all depends on the BMS and how it is configured for the internal pass through of power. if it is just one line then the cold weather will kill the whole battery, but if they spent some money and used diods and did two internal paths then you could controle charging and discharge independently. I guess we would have to dig into the BMS construction to know for sure...
Steve
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Oct-07-2021 05:16 PM
time2roll wrote:Ivylog wrote:Almost too good of a price. Please update when you get them.
I just paid $350 for 8-280AH cells and $370 for 8-310AH cells.
I agree but I’ve gotten confirmation of them being shipped.
Sold 04 Dynasty to our son after 14 great years.
Upgraded with a 08 HR Navigator 45’...
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Oct-07-2021 04:02 PM
StirCrazy wrote:time2roll wrote:Itinerant1 wrote:Heaters will be wired on the load side of the BMS. If the load side is powered by generator, solar or vehicle, the power will go to the battery heater.
If the heating pads are wired directly to the batteries terminal and if needing them because the actual cells are below 32f and not the ambient temp how would a generator help unless you have a heater cube plugged into it throwing heat to the compartment.
Are you going to add extra insulation on the walls/ floor to help keep heat in and cold out during the colder months if using them during that period?
Insulation will not be added unless it seems to be needed. Most camping is in fair weather. Not intended to be a north pole expedition vehicle. Just some minimal protection for a mild cold snap.
I think everyone is going on about a mute issue, unless the batteries are totaly dead then just the charging is going to be cut off at 32 degree ish, the discharge will still be available so the heating pads will work untill it gets down to a heck of a lot colder. if you insulate good around the batteries you may never come to this as the discharge from using/charging the batteries will create there own internal heat and with the right insulation it might be enough to keep them above zero down to a pretty cold temp, but that just theory...
Steve
I was thinking about this at work, and I may be wrong... it all depends on the BMS and how it is configured for the internal pass through of power. if it is just one line then the cold weather will kill the whole battery, but if they spent some money and used diods and did two internal paths then you could controle charging and discharge independently. I guess we would have to dig into the BMS construction to know for sure...
Steve
2016 Cougar 330RBK
1991 Slumberqueen WS100