Sun Trekker

[Campin]

...building an off grid system to boondock 4-6 months, GS and I thank the forum for great information!
I‘ll post updates here on solar hardware and performance as I journey through the build and Arizona. ?

20’ Jayco TT
Xterra Pro-4x TV
640 watt array
3000 inverter
60 amp mppt
Tilt kit
Smart battery monitor
Active balancer
280AH 24V LiFe battery bank

 

[Campin]

I decided to look at loads that affect AH drain. Two things in particular had to go, the microwave and standard furnace (disconnected), efficiency ranged between 40 and 76%. The replacements are an instant pot, small mr. buddy heater (connected to RV line) and 24V electric blanket. By removing the MW, I gained 2 cubic feet of space too.

btw, system requires a dc step down converter (24-12).

 

[hour]

Is there a good reason for ditching the stock furnace? I gave away my Mr Buddy heater in favor of the suburban whatever btu furnace in my camper. Which I then stopped using in favor of a diesel air heater.

Mr Buddy: moisture, hard to warm up after going in and out
Camper heater: noise, on or off, lowest setting on thermostat would often make for a 90*F camper
Diesel heater: having to carry diesel (my vehicle is gas), otherwise fantastic

 

[Whinny]

I would not consider a Mr. Buddy heater in an enclosed space if it is open flame, the dangers of CO are far too great.
Are the efficiency concerns electrical or propane in nature?

 

[Campin]

hour wrote:
Is there a good reason for ditching the stock furnace? I gave away my Mr Buddy heater in favor of the suburban whatever btu furnace in my camper. Which I then stopped using in favor of a diesel air heater.

Whinny wrote:
I would not consider a Mr. Buddy heater in an enclosed space if it is open flame, the dangers of CO are far too great.
Are the efficiency concerns electrical or propane in nature?

I should clarify what I post here is specific to my Jayco TT and info may or may not be useful in your situation.

I chose the small Mr. Heater because it has good reviews and BTU output for my space. The existing furnace is very inefficient (propane guzzler) and uses electricity. As for moisture, it should be minimal in the desert but I have dehumidifier bags just in case. ...will post an update after field test.

Yeah one needs to pay attention to carbon monoxide. I have two smoke/co detectors and never leave a flame unattended. When sleeping there’s always the comfy 24V electric blanket. Anyway the heater is designed for indoor use w/caution.

I have a portable fan near mr. buddy...forced air heat! : )

 

[Campin]

LW charger arrived today

 

[Campin]

Build supplies trickling in, I ordered an 8S active balancer.

 

[Campin]

My 280AH (8) cells are 3mV apart according to the seller, I’ll test upon arrival and let you know.
3.299
3.299
3.296
3.296
3.297
3.299
3.299
3.299

 

[Campin]

My 280AH (8) cells are 3mV apart according to the seller, I’ll test upon arrival and let you know.
3.299
3.299
3.296
3.296
3.297
3.299
3.299
3.299

@ Gazoo - thnx for mentioning cell voltage diversion...good to know. You ask why bottom balance?? Will Prowse mentioned it in a video and I read online it’s preferred without BMS. Anyway I’ll set SOC range at 15-85% for starters and DOD cell alarm at 3.1V. SCC will manage charge limit and battery temp.

@ ArthurEld - I saw your suggestion to set low SOC alarm at 3.2V (without BMS). Thnx

 

[Ampster]

it’s preferred without BMS.

However most people would agree a BMS is preferred over no BMS.

 

[ArthurEld]

@ArthurEld - I saw your suggestion to set low SOC alarm at 3.2V (without BMS). Thnx

It's a place to start. You should be able to open up the limits gradually while monitoring individual cells.

 

[ArthurEld]

However most people would agree a BMS is preferred over no BMS.

I have 5 BMSs and using them is my preferred method.

 

[Campin]

I ordered the PowerMon (Thornwave Labs) to monitor LiFe systems. It does the usual + SSR (optional) and long distance BT.

 

[Campin]

The 280AH cells should arrive in a few weeks, in the meantime gathering bits and pieces for the off grid system.

The busbars are made of copper flat bar. Hardware (battery pack, inverter, scc, etc.) will be in one area for efficiency and under my bunk to closely monitor or hot seat ?

 

[Campin]

I installed 1” wiremold (in corner) for PV wire and Aims LCD remote panel cable. Panel will be above radio for ez viewing along w/BT monitoring. A battery voltage checker alarm will monitor active balancer and cells too.

 

[Campin]

My solar system without BMS module-

The Smart battery monitor controls a mechanical relay. The relay will disconnect load from LiFe pack at 15% SOC (25.2 volts). Outback SCC will stop current at 85% SOC (26.5 volts). Pack voltage is set by bottom balance and an active cell equalizer. There’s an 8S checker alarm/display to monitor each cell...it‘s very accurate. Also the SCC has a temp cutoff sensor.

I feel confident managing the system w/BT (75’) and LiFe cell stability. After initial startup, monitoring should be seldom.

It looks good on paper subject to field test.... : )

 

[Campin]

more build parts?

 

[Campin]

...LiFe from overseas, I received 2 of 8 cells today. Exciting

 

[Campin]

My 280AH (8) cells are 3mV apart according to the seller, I’ll test upon arrival and let you know.
3.299
3.299
3.296
3.296
3.297
3.299
3.299
3.299

Cells arrived safely, well packed. ...so far so good.
Slight change in numbers.
3.303
3.303
3.300
3.300
3.303
3.303
3.300
3.303

 

[Campin]

Copper stock for bussbars and 24V 200A relay for battery disconnect.