RV 24V System

Suntrekker

640W 24V LiFePO4 280AH 

I jumped from the build thread (https://forum.solar-electric.com/discussion/356634/life-cell-internal-resistance#latest) and will post off grid system details, performance and experiences.

Thnx Bill/Forum members for the support!

Suntrekker

System hardware under the bunk.

Suntrekker

I’m dry camping in national forest, northern Arizona.  Off grid system has power to spare, running all appliances including AC (no generator).  I’m a happy camper!  : )

And 24V battery is clicking on all cells (credit the active cell balancer), it floats under 27V (90%+ SoC).

The only issue was a 60A fuse meltdown between the SCC and battery. …my fault, I installed an audio fuse. 

BB.

Yep... "Good/Solid" fuse blocks and fuses usually "bolt on" are not cheap (for high current systems).

MRBF holders and fuses are relatively small form factor--If space is an issue:

https://www.bluesea.com/products/category/16/72/Fuse_Blocks/Terminal_Fuse_Blocks



Also, I don't remember your actual battery charging current (maximum/continuous)--I like to always suggest that battery charging circuits (wiring/breakers/fuses) be rated for 1.25x (1/0.80 or 1/80%) of charging current. For example, if you are really charging at 60 amps, suggest:

• 60 Amps * 1.25 for NEC continuous current derating = 75 Amp or larger wiring/current protection device (CPD)

For North American fuses/breakers they are generally rated to "trip" at 100% or greater current, and "not trip" at 80% or less of rated current.

When charging batteries--A well discharged battery can usually accept maximum/rated charger current (i.e., 60 amp charger) for "hours" (600 AH bank @ 10% rate of charge = 60 amps)... And a 50% discharged bank can take that current for upwards of 5 hours continuous rated current flow. A fuse/breaker (and wiring) running at 100% of rated current (or for example 60 amp fuse * 0.80 NEC derating = 48 amps suggested max continuous current flow) is going to run hot and possibly trip after hours of rated current flow.

You could also replace the fuse with a breaker (with manual trip) and have the OCP and "switch" function too (turn off for service, winter storage, etc.).

-Bill

Suntrekker

Bill, good info (as always)!
Yeah I installed another fuse and happy to report all’s good.

Suntrekker

Off grid hardware:

REC 320NP mono 320W panel (2)

Tamarack tilt kit

Outback FM60 SCC

Aims 3K pure sine wave inverter 

Aims remote LCD display 

DC converter 60A

LiFePO4 24V 280AH battery bank 

Active cell balancer 

Cole Hersee solenoid 24V 200A

PowerMon smart battery monitor

Perko main disconnect switch 250A

Assorted breakers, fuses

Suntrekker

Love Off Grid - away from the hubbub.

Suntrekker

Hi Bill and fellow members, update after a year.  All’s good, the lithium 24V battery performs well!

BB.

Thank you for your updates... Always wonderful to read about successful solar installations.

Take care,
-Bill

Suntrekker

  

JRHill

Whether boondocking or just plain living off grid in the middle-of-nowhere is something many do not desire or relate. Ask a city or urban dweller the last time they stopped and listened to snow flakes hitting the trees. You'd have to pull the ear buds out.

BTW, nice set up. TY  for the beautiful pictures.

Horsefly

Very nice pics!  I'm still amazed that you don't have a BMS, but it seems to be working for you.

Be aware that I had that exact active balancer and something went haywire on it while I was testing. One side (around 50% of the capacitors) got too hot to touch, and the board was draining one of my cells pretty quickly. That cell would have been destroyed had I not checked on the system when I did. Since then I only plug in the active balancer when the cells look out of balance, which I can see on my BMS Bluetooth app. I unplug it again a few hours later after it's done its job.

Suntrekker

JRHill 

Thnx Horsefly for mentioning the active balancer, I’ll keep it in mind.  Battery performance is monitored by phone (Bluetooth).  All looks good!

And I’ll post more pics of my surroundings, BLM land and Prescott National Forest.  

…phone/internet service is spotty but I’m not complaining 

Suntrekker

Rare snowstorm in the desert.

Suntrekker

Cold nights (20°) have prevented solar charging until the battery warms up.  I didn’t foresee camping in low temps (or take the necessary precautions).  …charging has been reduced to 4 hours/day.