1120ah Bank Build for 12V... Opinions Wanted Please

[Ram5500 CamperThing]

Hi All

New guy here, almost done building my mid life crisis off the grid dream camper...

Its all setup to run off electricity and eliminate propane, etc... I am running electric induction stove, electric water heater, microwave, and AC

Current setup is (2) 375 watt LG residential panels in series on the roof, Sterling 60amp DCDC charger, and one LifeBlue 300ah battery, Victron 3000 watt inverter charger, Victron 150/70 amp solar controller

Having now used the camper, microwave, water heater and AC a bunch on several trips, its all working perfectly as planned.

Well... Provided its sunny out... hahahaha.

Last trip had crappy weather the entire time, and got down to 22% SOC and decided i needed a bigger bank to be prepared for less than ideal solar conditions.

I am fortunate the way i built this camper, i left a ton of room around the battery and inverter for expansion if i needed it.

I am considering building a 1120ah bank made up of the 280ah cells in Wills video. I have the room...

I wont bore y'all with questions usually asked 100000x, but i did have a few that i cant seem to find answers on...

I know 750watts i'snt ideal for a 1120ah bank, neither is the 60amp DCDC charger.

The solar is maxed out on the roof due to space. I could upgrade the DCDC to the Sterling 120amp.

I also have the camper setup for shore power when near utilities. Generator isnt an option, i am very much against them, and the noise they make at camp!

My main 2 questions really is:

-Would a bank that big have any drawbacks other than slower charging than ideal for the capacity, or would i be better off with a smaller bank (thinking 560ah) and keeping it easier to top off?

-If prepared and built properly with spacer between the cells and everything secured, would they be able to handle excessive vibrations in an offroad environment? Example: Last year i did the Dempster Hwy to the arctic circle and logged about 1000 miles of dirt corrugated roads.

Thanks

If anyone is interested in the offroad camper stuff, my link is in my sig

 

[CyrusL]

I built that same battery: 280ah x 16 in a 4s4p arrangement. I love it so far. I don't understand how having it be "easier to top off: would be somehow better. If you went out boondocking for a few weeks and some if the time it was cloudy, it sounds like you'd be able to get by just fine. A battery that big would take a long time to charge up with that amount of solar, but who cares. If it's sunny and you are using less than the panels are creating each day, it would eventually fill up.

I'm not an authority on the excess vibrations, but I've heard that they should be just fine. Someone else can speak better to that topic.

 

[DThames]

I think you might be confused on your amp hour value for your suggested battery. Four 280 amp hour cells in series is 280 amp hours, 12v if you are talking about LiFePo4 cells (Will talks about often). If you draw down 250 amp hours, that is about 3000 watt hours from the battery. You will need 5 or more hours of good sun to charge that back up with those two panels.

But if you go from 300 to almost double that, on that same trip your battery would have been about 40% instead of 22%. So what is that worth? Also, you might pack some of those thin flexible panels that you could lay out on the ground to boost your charging when conditions were not ideal.

I see no major drawbacks of just a larger battery on the same system.

 

[Ram5500 CamperThing]

I built that same battery: 280ah x 16 in a 4s4p arrangement. I love it so far. I don't understand how having it be "easier to top off: would be somehow better. If you went out boondocking for a few weeks and some if the time it was cloudy, it sounds like you'd be able to get by just fine. A battery that big would take a long time to charge up with that amount of solar, but who cares. If it's sunny and you are using less than the panels are creating each day, it would eventually fill up.

I'm not an authority on the excess vibrations, but I've heard that they should be just fine. Someone else can speak better to that topic.

Thanks for chiming in and good to hear you’re digging yours! Happen to have any pics or diagrams of the layout To share?

 

[Ram5500 CamperThing]

I think you might be confused on your amp hour value for your suggested battery. Four 280 amp hour cells in series is 280 amp hours, 12v if you are talking about LiFePo4 cells (Will talks about often). If you draw down 250 amp hours, that is about 3000 watt hours from the battery. You will need 5 or more hours of good sun to charge that back up with those two panels.

But if you go from 300 to almost double that, on that same trip your battery would have been about 40% instead of 22%. So what is that worth? Also, you might pack some of those thin flexible panels that you could lay out on the ground to boost your charging when conditions were not ideal.

I see no major drawbacks of just a larger battery on the same system.

Yeah, good point, i worded that poorly.

I meant a total of 16 cells. 4 banks of 4

 

[DThames]

Yeah, good point, i worded that poorly.

I meant a total of 16 cells. 4 banks of 4

That would indeed take a while to charge. But if you go on a trip fully charged and the trip is of limited duration, that would be a win. Have you considered a second layer of panels on some type of a fold out with some legs? Sort of like a rigid canopy with panels on top.

 

[HRTKD]

I have 4s2P for 560Ah and it works great with my 640 watts of PV on the roof. I do not run air conditioning off of my batteries. I use the generator for that, mainly because my inverter is too small to support the load the air conditioner draws. In the winter I deploy 640 watts of PV on the ground to supplement the roof PV. That works well enough that I have enough surplus watts to run an electric space heater so that the propane heater doesn't run as much.

Once I get a properly sized inverter, I'll be deploying the ground panels and using air conditioning if I need it.

As suggested above, more battery Ah is fine, as long as you have a defined period that you expect to be out. Going home with the battery bank at 20% is OK as long as you're going home because it's time to go home, not because you're out of Ah.

I do not worry about my state of charge with the LiFePO4 bank like I did when I had a 225 Ah lead acid bank.

 

[Ram5500 CamperThing]

That would indeed take a while to charge. But if you go on a trip fully charged and the trip is of limited duration, that would be a win. Have you considered a second layer of panels on some type of a fold out with some legs? Sort of like a rigid canopy with panels on top.

Not as of yet, but nothing is out of the question at this point in my build!

 

[Ram5500 CamperThing]

I have 4s2P for 560Ah and it works great with my 640 watts of PV on the roof. I do not run air conditioning off of my batteries. I use the generator for that, mainly because my inverter is too small to support the load the air conditioner draws. In the winter I deploy 640 watts of PV on the ground to supplement the roof PV. That works well enough that I have enough surplus watts to run an electric space heater so that the propane heater doesn't run as much.

Once I get a properly sized inverter, I'll be deploying the ground panels and using air conditioning if I need it.

As suggested above, more battery Ah is fine, as long as you have a defined period that you expect to be out. Going home with the battery bank at 20% is OK as long as you're going home because it's time to go home, not because you're out of Ah.

I do not worry about my state of charge with the LiFePO4 bank like I did when I had a 225 Ah lead acid bank.

Good feedback! Thank you!

 

[rickst29]

I would not use "precious" off-grid electric power to run the water heater, and a traditional propane furnace is also pretty effective in cold weather. I'm keeping propane in place for those purposes - although my LFP battery bank is less than half the size of yours. OTOH, I've got a normal Trailer with an A-frame hitch -- and my propane tanks do not consume valuable RV living and storage space. If you're putting batteries where your propane tank used to be stored, then I can only say .

 

[Ram5500 CamperThing]

I would not use "precious" off-grid electric power to run the water heater, and a traditional propane furnace is also pretty effective in cold weather. I'm keeping propane in place for those purposes - although my LFP battery bank is less than half the size of yours. OTOH, I've got a normal Trailer with an A-frame hitch -- and my propane tanks do not consume valuable RV living and storage space. If you're putting batteries where your propane tank used to be stored, then I can only say .

I had horrendous experience with my last Propane setup in extreme cold at elevations over 8-9k feet (where i do most of my camping). Also, the propane heat was a wet heat, and caused condensation. It worked maybe 50% of the time, if that. I tried everything, and had many "experts" look at it, and just gave up.

For this build, i used the Espar D2L diesel heater and it is plumbed right into my main full tank of the truck and running on high, it will use less than a gallon of fuel. Never have to worry about refilling tanks, etc... The heat is dry, and causes zero condensation, and it sips power (2ah).

Details of my setup in my videos, in my sig below. I built this entire camper/truck from scratch fixing all the issues and downsides i had previously.

 

[HRTKD]

I would not use "precious" off-grid electric power to run the water heater, and a traditional propane furnace is also pretty effective in cold weather. I'm keeping propane in place for those purposes - although my LFP battery bank is less than half the size of yours. OTOH, I've got a normal Trailer with an A-frame hitch -- and my propane tanks do not consume valuable RV living and storage space. If you're putting batteries where your propane tank used to be stored, then I can only say .

This is my experience also. My propane powered water heater runs from the time I put water in it at home until I bring the trailer back and drain the tank. I camped last October at 9,000' elevation and it got down to -8° F. Zero problems with the 15 year old Atwood water heater.

 

[Bob B]

The only time I have seen propane heat be "wet" is with something like one of those Mr Buddy heaters that some people run in their RV ..... I wouldn't have one of those in my RV either.
If you monitor CO2 levels in an RV ... they get high enough without something like that ... and there IS a lot of moisture from those also.
My propane furnace with circulates warm air in the battery compartment and around the holding tanks and does a good job and uses outdoor air for combustion. Maybe a little less efficient with the heat exchanger, but I have 2 large propane tanks and haven't had a problem.
I also have an Attwood propane heater that works fine ... Mine is only 14 years old. Only problem I ever had with it is when I forgot to bleed off the pressure before replacing the anode .... take my word for it .... don't do that.

 

[Ram5500 CamperThing]

So as i am planning this out, a few questions have popped up that i cant seem to find answers to.

I was planning on (16) 280ah cells, for 1120ah. Essentially making (4) separate 12v batteries using 4 cells for each. Sounds like @CyrusL has done similar

Is this referred to a 4s4p arrangement? Where can i find the designations for various arrangements? I haven't had much luck looking.

I need to do some more detailed testing on my max draws, but as of now, it seems the water heater is my biggest draw, at around 160amps.

So to have a buffer, i'd probably run a 250amp BMS. With 16 cells, how does one wire up a BMS? Almost all i have seen have only 8 leads on them

I've read some suggestions on here that folks are suggesting a separate BMS for each battery. That seems a bit much. But is that the best way?

Thanks

 

[HRTKD]

Yes that's a 4s4p configuration. The Resources section of the forum may have a listing of the various configurations.

You need one BMS for each 4s battery. An Overkill Solar 120 amp 4s BMS on each battery would give you 480 amps of throughput.

 

[vtx1029]

I run my ice fishing trailer off of a 560ah battery i built (4s2p). It works great! I've been able to boondock for a week without charging at all. that's running my 2kw diesel heater in sub freezing temps. I also have a 2000 watt inverter and do all my cooking on a pizza oven. Also run my tv and satellite dish from it. I'm planning on doing some sort of solar this summer but it will be a smaller system around 300 watts of solar. That should be able to keep me from ever depleting the battery. The biggest difference in your setup is you run an AC so yes I would double the capacity in that case. I used 2 separate BMS's for my build for 2 reasons. 1. higher current capacity for less $ and 2. for redundancy. if something happens to one bms or battery I'm not putting my self in a life or death situation.

FWIW the problem you had with propane heater is you were using a non vented heater. if you would have used a vented heater like a normal RV furnace you would have not had the moisture problems. But I do agree I have had my propane regulator freeze up in -50*f temps (not fun)

 

[Sipma02]

Don't forget—if you are camping in cold weather, the batteries will need to be kept above 32ºF to be charged. LFP can be discharged below that, but not charged. @HRTKD has a good thread on a battery warmer setup, he did a nice job. I have a similar setup for our 280ah, it doesn't turn the battery heater on until it gets to around 40ºf, which rarely happens because our battery cells are in the cab. (heated by a diesel heater)

 

[Ram5500 CamperThing]

Yes that's a 4s4p configuration. The Resources section of the forum may have a listing of the various configurations.

You need one BMS for each 4s battery. An Overkill Solar 120 amp 4s BMS on each battery would give you 480 amps of throughput.

Perfect! Thank you sir! Found it in the resource section and saved it on the PC. Perfect!

Im on a lot of forums for various things, and the amount of info on this one that folks are able to bookmark and use is absolutely amazing!

 

[Ram5500 CamperThing]

I run my ice fishing trailer off of a 560ah battery i built (4s2p). It works great! I've been able to boondock for a week without charging at all. that's running my 2kw diesel heater in sub freezing temps. I also have a 2000 watt inverter and do all my cooking on a pizza oven. Also run my tv and satellite dish from it. I'm planning on doing some sort of solar this summer but it will be a smaller system around 300 watts of solar. That should be able to keep me from ever depleting the battery. The biggest difference in your setup is you run an AC so yes I would double the capacity in that case. I used 2 separate BMS's for my build for 2 reasons. 1. higher current capacity for less $ and 2. for redundancy. if something happens to one bms or battery I'm not putting my self in a life or death situation.

FWIW the problem you had with propane heater is you were using a non vented heater. if you would have used a vented heater like a normal RV furnace you would have not had the moisture problems. But I do agree I have had my propane regulator freeze up in -50*f temps (not fun)

Wait a second here... Hold up....

A PIZZA OVEN WHILE CAMPING????

Link please!

 

[Ram5500 CamperThing]

Don't forget—if you are camping in cold weather, the batteries will need to be kept above 32ºF to be charged. LFP can be discharged below that, but not charged. @HRTKD has a good thread on a battery warmer setup, he did a nice job. I have a similar setup for our 280ah, it doesn't turn the battery heater on until it gets to around 40ºf, which rarely happens because our battery cells are in the cab. (heated by a diesel heater)

Thanks for the reminder.

Yeah, i highly doubt the inside of my camper box (where the batteries live) will get below that, but just in case, i will have one of these under them:

Under Floor Heating Fabric, 12 volt

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