Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Lifepo4, need list of components!
#1
Hey everyone, decided to go for lifepo4, but im unsure of exactly what I need to get a system up and running. BMS, can I use a regular tracer 20 A Mppt Charge controller, what about battery isolator, do I need a special one, fuses etc. Links would be great!

Im thinking of a 300w mono panel, and a 90-150Ah bank.

And what physical dangers are there?
Add Thank You Reply
#2
Ok... this is what you need

Batteries...of course.....
Then,

Battery balancer. Battery Management system. Mppt charge controller that can deliver 2-4 stage charging.

Everything else is no different that you would have for any battery system.

The only issues with lithium is that it does not perform well if you charge them when they are too warm or too cold.
Recommend you get the cells encased in aluminum as it will allow heat transfer quicker than the typical plastic. Also.install fans and ventilation. And a low power heating pad.

Also..lithium does not like to be kept at full charge. If you will not be using power for a few days..set your mppt to cut off before full charge.

But these are more of an effect on longevity.

The ones that explode or catch fire are the cobalt lithium.

I recommend you have a talk with the guys at
http://www.electriccarpartscompany.com/

I can post diagrams if you need them....
"I never saw a sight that didn't look better looking back"

1988 Honeywell.  E350 chassis   21'
Add Thank You Reply
The following 1 user says Thank You to RoamingKat for this post:
Scott7022 (08-13-2017)
#3
Good Source and one I had never seen before. I like the sprinter van set up but wonder at the high jump to charge off alternator option Looking back and forth between the two; alternator and sprinter I don't get the price jump. A simple DC to DC controller would do the trick. Like the Sterling or Blue Sea DC to DC, The Blue Sea even has a lithium unit for DC starting to DC house.

Still a great resource. Loads of options and hmmmm points. I got kind lost in the 12 Compressor area for AC...Loads of HMMMMM

I went with Battle Born because of the service and hell yeah it will do it attitude. But I wish I knew about this place earlier!!
Beast Master and Junky Monkey in the You Ain't Right Club. 2 stinking badges and a cluster (I think, Hard to keep track, don't want to be accused of stolen honor) ((Can you steal a you ain't right badge or would that just be not right??))
Add Thank You Reply
#4
Photo 
If you buy an off the shelf 12.8 volt lifepo4, thats a drop in replacement for lead acid. Those already have a BMS, the bms is like a relay if the voltage gets too low or too high it shuts off the battery. You can use any solar charge controller mppt or pwm. They recommend you disable the float voltage but with off the shelf lifepo4 probably not needed. The BMS will also keep the battery balance automatically. The 12 volt ones they sell are usually in the 100ah range. 

If you decide to build your own, you do need a BMS, but they are inexpensive, I use a 30 amp 6 dollar one, but if you want car cranking BMS that will be in 40 dollar range. Also I use an overvoltage relay (7 dollars), that will shut off power no matter what if the battery reaches 14.4 volts, it acts as a deadman switch. On these cheaper BMS, they mostly monitor the balancing, if the battery goes out of balance they shut off the battery before they get damage.  

These are the voltages the lifepo4 operates at, fully charge voltage is 14.6 volts and fully discharge voltage 11.2 volts. Well within the range of lead acid.

I been using my 110ah lifepo4 I built for the past month and it's been connected to my 20 amp ecoworthy mppt, its been performing excellent. I have to crank up the absorb voltage to 14.8 volts to try and fast charge it, at the normal 14.4 volts it charges slowly at about 4 amps. Even at 14.8 volt it charges at 10 amps or less, even though the controller is capable of 15 amps. The controller see's a fully charge battery and keeps the amps down. The battery has so far stayed in balance, but I do have a 14 amp isdt q6 balance charger just in case. To fully charge the battery I do need to use the balance charger and hit it with 10 amps for several hours, the mppt controller so far has never been able to get the battery up to 14.2 volts, its never tripped the overvoltage regulator. Unlike lead acid, lifepo4 doesnt need to be fully charge, it won't get damage from undercharging. 

The off the shelf lifepo4 are design with many built-in safety features, they are as safe as they can be. If you build one, you have to use fuses everywhere, monitor the balancing at all times, make sure you have a good bms, and for me an overvoltage relay is essential to shutoff charging when the voltage gets close to the maximum in case the bms fails. I been using lithium for almost 2 years and never had any problems, I started off using the laptop cells which are more dangerous and built a 94ah pack, lifepo4 is many times safer and at 14.4 volts I find it hard to overcharge. The most dangerous lithiums are the rectangular soft packs used in the RC world, those are very sensitive to catch on fire when overcharged.

picture of my 110ah lifepo4, it shows overvoltage regulator led on the left and the balance voltage led on right. And there are 2 xt60 connectors in the rear where I plug into it. In the month I have been using it, the lowest voltage I seen is 12.9 volts and that's using it all night as I would my lead acid. It holds voltage well. In the morning it mostly sits at 13.1 volts. 
   
Add Thank You Reply
The following 1 user says Thank You to jonyjoe303 for this post:
rm.w/aview (08-15-2017)
#5
I attempted to distill the LFP info from the giant sailing thread into a couple of pages of reading.

The most interesting tidbit from a vandweller point of view is that "Fractional C" use may not require BMS.*  There are folks on the forum running that way right now with good results.  I plan to run mine "barefoot" after my golf cart bank shuffles off this mortal coil.  


* and that BMS failure under normal conditions may be a leading cause of LFP cell death.
blog/brainstorming  | Promaster 159" high roof build <-- white and nerdy
Retirement w/small pension:  May 15, 2025
Add Thank You Reply


Possibly Related Threads...
Thread Author Replies Views Last Post
  List of solar components StarEcho 38 8,650 05-21-2015, 09:41 AM
Last Post: johnny b

Forum Jump:


Users browsing this thread: 1 Guest(s)

Powered By MyBB, © 2002-2017 MyBB Group.