RV.Net Open Roads Forum: How to build a LiFePo4 battery bank.

RV Blog

  |  

RV Sales

  |  

Campgrounds

  |  

RV Parks

  |  

RV Club

  |  

RV Buyers Guide

  |  

Roadside Assistance

  |  

Extended Service Plan

  |  

RV Travel Assistance

  |  

RV Credit Card

  |  

RV Loans

Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Do It Yourself Modifications a...

Open Roads Forum  >  Do It Yourself Modifications and Upgrades (DIY)

 > How to build a LiFePo4 battery bank.

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 9  
Prev  |  Next
Sponsored By:
BFL13

Victoria, BC

Senior Member

Joined: 02/15/2006

View Profile



Posted: 10/06/21 09:46am Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

BFL,

Where did 5C come from?


Trojan Trillium charging specs. Also some(all?) drop-in self- heating LFPs have the battery charger (there is your generator requirement) power the internal battery heater and get the bank up to 5C before it switches the charger power over to battery charging. It takes about two hours to warm them up from -20C to 5C I saw somewhere, but not so long when it is just under freezing of course..

The better idea is obviously to not let the batts get that cold in the first place, and the DIY set-up like time2roll has built should be way better than the drop-in method.

If the bank is inside the RV you keep it warm with propane furnace or if in outside compartment, you can perhaps DIY a way to get hot air or hot water (also from propane) to it, or else you are stuck with having some kind of DC heater.

Some say you can charge the LFPs at full blast once they are above 0C freezing, but others say you should/must use a reduced charging rate between 0 and 5C, scaling up the rate, like the Trillium specs.

Not many RVs will have a converter or charger that can do higher rate charging on a bigger AH LFP bank anyway.


1. 1991 Oakland 28DB Class C
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.

time2roll

Southern California

Senior Member

Joined: 03/21/2005

View Profile



Good Sam RV Club Member


Posted: 10/06/21 10:34am Link  |  Quote  |  Print  |  Notify Moderator

I do wonder if these self heated batteries only allow external power for heating.


2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
675w Solar pictures back up

BFL13

Victoria, BC

Senior Member

Joined: 02/15/2006

View Profile



Posted: 10/06/21 06:03pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

I do wonder if these self heated batteries only allow external power for heating.


Should still be able to keep them warm with heat pads, etc. Only then use the charger heating method as an emergency back-up.

I see I forgot the actual Trillium charging specs. They do allow a little charging a little below freezing, but also only allow full charging at 73F. No clue how that may apply to other LFPs.

https://www.trojanbattery.com/pdf/Trillium_UsersGuide.pdf

* This post was edited 10/06/21 07:16pm by BFL13 *

pianotuna

Regina, SK, Canada

Senior Member

Joined: 12/18/2004

View Profile


Offline
Posted: 10/06/21 06:22pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

I do wonder if these self heated batteries only allow external power for heating.


The ones I've found online draw from the battery, and have no provision for an external energy source.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, soon to have SiO2 batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

pianotuna

Regina, SK, Canada

Senior Member

Joined: 12/18/2004

View Profile


Offline
Posted: 10/06/21 06:27pm Link  |  Quote  |  Print  |  Notify Moderator

Thanks BFL13 for the information.

BFL13

Victoria, BC

Senior Member

Joined: 02/15/2006

View Profile



Posted: 10/06/21 06:53pm Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

time2roll wrote:

I do wonder if these self heated batteries only allow external power for heating.


The ones I've found online draw from the battery, and have no provision for an external energy source.


PT, this a typical blurb for a "cold weather" drop-in LFP:

"In cold temperatures, the BMS ( battery management system) disconnects from the cells to protect your battery. Prior to charging, the built-in heating systems draw power from the charger in order to heat up the battery."

Time2roll would set his BMS to allow charging at X temp, and also set his heat pad Tstat relay temp to keep them above that BMS set charging temp.

No idea where his charging rate setting might be for cooler temps, if he even does that. Once set up and camping proven after any adjustments, it should be easy after that to just go camping no worries.

* This post was edited 10/06/21 07:05pm by BFL13 *

StirCrazy

Kamloops, BC, Canada

Senior Member

Joined: 07/16/2003

View Profile



Posted: 10/06/21 06:54pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

Itinerant1 wrote:

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?
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.

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


2014 F350 6.7 Platinum
2016 Cougar 330RBK

Ivylog

Blairsville, GA and WPB, FL.

Senior Member

Joined: 06/30/2004

View Profile


Offline
Posted: 10/06/21 07:05pm Link  |  Quote  |  Print  |  Notify Moderator

I just paid $350 for 8-280AH cells and $370 for 8-310AH cells. Will build 2 12V batteries out of each group of 8 cells. Bought 4 200A BMS for $240 plus probably $100 in cables and parts… works out to 90 cents/AH plus probably 20 hours of my time. Doubt the cells will be grade A so I may only have 1100 AH pushing my price to $1/AH…OH well, I can live with that as 9 months ago I thought I’d done well building 600AH for $1200.

Not worried about charge them below freezing as rarely am I in freezing weather. If needing to charge…turn off the chargers (solar included) and run the generator, putting an electric heater in the outside battery area until the cells are above freezing and then charge.


This post is my opinion (free advice). It is not intended to influence anyone's judgment nor do I advocate anyone do what I propose.
Sold 04 Dynasty to our son after 14 great years.
Upgraded with a 08 HR Navigator 45’...


time2roll

Southern California

Senior Member

Joined: 03/21/2005

View Profile



Good Sam RV Club Member


Posted: 10/06/21 07:14pm Link  |  Quote  |  Print  |  Notify Moderator

Ivylog wrote:

I just paid $350 for 8-280AH cells and $370 for 8-310AH cells.
Almost too good of a price. Please update when you get them.

StirCrazy

Kamloops, BC, Canada

Senior Member

Joined: 07/16/2003

View Profile



Posted: 10/07/21 05:02pm Link  |  Quote  |  Print  |  Notify Moderator

StirCrazy wrote:

time2roll wrote:

Itinerant1 wrote:

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?
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.

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

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 9  
Prev  |  Next

Open Roads Forum  >  Do It Yourself Modifications and Upgrades (DIY)

 > How to build a LiFePo4 battery bank.
Search:   Advanced Search

Search only in Do It Yourself Modifications a...


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:




© 2022 CWI, Inc. © 2022 Good Sam Enterprises, LLC. All Rights Reserved.