Need LiFePo4 battery and solar help.

Anything electric, AC or DC

Need LiFePo4 battery and solar help.

Postby zzzizxz » Sun Sep 08, 2019 6:43 pm

Hey experts!

I'd love some help please.

I built my own electrical system and have not been getting the amount of juice I expect. I would love to have someone look over my setup and let me know if I'm missing something, or if I have messed up somehow.

I have a 100Ah Lithium Ion Phosphate battery, coupled with a 100W solar panel. My Charge controller is a 20A MPPT, Epever TRIRON 2210N.

My issue is that according to the charge controller, I will go two or three days for my battery to go from 90% to 50%, and then will go to 0% overnight.

For example, I just got back from a camping trip. The only thing I was running was my Dometic cooler and white noise machines at night.
The cooler is rated at approximately 0.77ah/hr, ((Ambient = 90°F Compartment Temp = 41°F): 0.77Ah/h)

The white noise machines are rated at 0.5ah/hr.

I left the house Friday at 4pm, and the charge controller said the battery was at 85%.

I ran two sound machines from 8pm until 8am.

At 8pm Saturday, the charge controller said I had 48% battery left.

I only ran one sound machine Saturday night. The battery died at 0545 Sunday morning.

From the time I left the house until the time the battery died was 37 hours.

Sound machine usage the first night was 12ah. (0.5 x 2 x 12hrs)
Sound machine for second night was 5ah. (0.5 x 10)
Cooler usage for the whole time is 33.3, call it 35ah. Probably less, as temps were in the high 50s at night, and high 70s during the day. (This number is factoring cooler usage at 0.9ah/hr for 37 hours)


Total amp usage for the total trip should have been no more than 60ah, and actually closer to 50. I should have been able to go the whole time just from the battery, and not needed the solar panel. Even starting at 85%, I should have been at 30% left.

During the day, I did have the solar panel up, but we were shaded, so wasn't getting the best charge, but I was still getting 12.8v to the battery for most of the day.

Why would my battery go from 85% to 48% over the course of 24 hours, and go from 45% to 0% in 10 hours?!

Any help would be appreciated!!
zzzizxz
Teardrop Advisor
 
Posts: 83
Images: 142
Joined: Wed Oct 10, 2018 4:44 am

Re: Need LiFePo4 battery and solar help.

Postby tony.latham » Sun Sep 08, 2019 7:20 pm

I don’t know what’s going on but just because your system says it is producing 12.8 volts in the shade doesn’t mean it’s producing a measurable amount of power.

My new solar panel/controller shows 12.4 volts in the shop under the LED lights and 0 watts and 0 amps.

And I’m lithium dumb to boot.

Tony


Sent from my iPad using Tapatalk
User avatar
tony.latham
Gold Donating Member
 
Posts: 3932
Images: 17
Joined: Mon Jul 08, 2013 4:03 pm
Location: Middle of Idaho on the edge of nowhere

Re: Need LiFePo4 battery and solar help.

Postby bdosborn » Sun Sep 08, 2019 7:28 pm

Put an amp-hr meter on the battery for some insight into what is happening.

Inexpensive amp-hr meter

Bruce
2009 6.5'X11' TTT - Boxcar
Image
Boxcar Build
User avatar
bdosborn
Donating Member
 
Posts: 4483
Images: 482
Joined: Wed May 05, 2004 11:10 pm
Location: CO, Littleton
Top

Re: Need LiFePo4 battery and solar help.

Postby troubleScottie » Sun Sep 08, 2019 7:42 pm

Lots of things.

First, all things being equal your math is accurate.

Second, you are assuming that your mppt controller is giving you accurate information. Your particular controller does understand lithium batteries. I assume that is selected.

However, it does not have a shunt. The shunt is needed to accurately determine the state of charge of the battery, starting from a full charge. Without it, the information is a guestimate. Given lithium batteries often show full voltage before dropping off sharply, the guess could be wrong.

Most likely you really want something like a battery monitor eg Victron BMV-700H. There are probably less expensive monitors which are as accurate. Go to the Victron site. Lots of video on how they work, are set up, etc.

Third, there might be other things in the system. Is there an inverter for the white noise generator? Or the frig. I am guessing this is a DC frig, but you did not state that. Inverters are often tremendous power draws even when nothing is plugged into them. And they are not very efficient, so addition power consumption. BTW, the controller is drawing power while not charging.

Fourth, you are hoping that the power consumption is correct. You really need something to measure the power consumption of each device. I know there are AC ones. I presume there are DC equivalents. You need to really test each device.

Finally, it is possible that you have a short that is draining the battery. Not sure how to test.
Michael Krolewski
Scottish Terrier Fancier
troubleScottie
Donating Member
 
Posts: 245
Images: 11
Joined: Sat Apr 11, 2015 5:02 am
Location: Seattle, WA
Top

Re: Need LiFePo4 battery and solar help.

Postby John61CT » Sun Sep 08, 2019 8:00 pm

Any charge source that claims to know your SoC is lying.

Unless it is reading from a proper SoC meter with a shunt at the bank counting Ah in and out.

And even then just an educated guesstimate, needs frequent calibration.

Add more solar, use the alt and / or get a gennie.
John61CT
1000 Club
1000 Club
 
Posts: 1372
Joined: Thu Nov 17, 2016 4:36 pm
Top

Re: Need LiFePo4 battery and solar help.

Postby John61CT » Sun Sep 08, 2019 8:03 pm

Recharge every day, don't try to go 2-3 in between.

Get a clamp style ammeter and DMM, absolute minimum basic starting point for knowing what's going on.

Never trust meters that are part of other gear, measure independently.
John61CT
1000 Club
1000 Club
 
Posts: 1372
Joined: Thu Nov 17, 2016 4:36 pm
Top

Re: Need LiFePo4 battery and solar help.

Postby John61CT » Sun Sep 08, 2019 8:05 pm

Link to your Dometic cooler. Or is it a compressor fridge?

Depending on ambient vs internal setpoint, 15Ah up to 50Ah per day is normal.

Double that working as a freezer.

Get a coulometer and actually measure drawn Ah per 24hrs, forget "ratings" or mfg claims.
John61CT
1000 Club
1000 Club
 
Posts: 1372
Joined: Thu Nov 17, 2016 4:36 pm
Top

Re: Need LiFePo4 battery and solar help.

Postby John61CT » Sun Sep 08, 2019 8:09 pm

Battery is not charging properly unless it gets up above 14V for many hours per day.

12.8V is the bottom point, you don't want to go anywhere near that at rest if you care about longevity.
John61CT
1000 Club
1000 Club
 
Posts: 1372
Joined: Thu Nov 17, 2016 4:36 pm
Top

Re: Need LiFePo4 battery and solar help.

Postby zzzizxz » Sun Sep 08, 2019 8:18 pm

All,

To answer some questions, I do not have an inverter, everything I'm running is a 12v system.

Fridge is the Dometic CFX50W.

It looks like the main answer is that since I do NOT have a amp-hour meter, the MPPC charge controller is not giving me truly accurate info. I'll be getting an AH-meter and finding out actual numbers.

This seems to be the main piece in my system that I was missing.

Thank you!
zzzizxz
Teardrop Advisor
 
Posts: 83
Images: 142
Joined: Wed Oct 10, 2018 4:44 am
Top

Re: Need LiFePo4 battery and solar help.

Postby nemoskull » Fri Sep 13, 2019 12:23 am

okay, just looking off amazon the mppt charger needs a seperate module for lifepo4.
second off, lifepo4 has a pretty flat and non linear discharge curve, so keep that in mind.
livepo charging a cell is 3.65v max, so that works out 14.6v absoulute max charging voltage. id check with a voltmeter with the panel in the sun on a sunny day to make sre battery voltage is below this, it should never get avout 14.6v ever. (keep in mind im used to lipo, there a little different.)
as far as i know, you cant tell state of charge from voltage with lifepo4.

the other major issue is the battery it self, lifepo4 sometimes (always?) have an internal protection circuit. meaning there is a whole nother charger inside and mosfet that will cut power to the terminals when voltage gets too low. check with the mfg of the battery to see if it has internal protection.

a lifepo4 battery should never go below 3v a cell, or 12v in your case, in generally (some might push it to 2.5v a cell, but im really fuzzy here).

you need better information, i use these
https://www.amazon.com/gp/product/B07DL ... UTF8&psc=1
they measure watts and amps in. they only work one way, so i have two.

im a little off here, i use lipo in my trailer, so there a bit different than lifepo4.
nemoskull
Teardrop Builder
 
Posts: 39
Images: 2
Joined: Fri Nov 25, 2016 5:04 am
Top

Re: Need LiFePo4 battery and solar help.

Postby Vtec44 » Fri Sep 13, 2019 12:55 am

Can we go back to some of the more basic information first? :)

What's the brand of your battery?
What's recommended charging voltage for your battery?
Is the charging parameter of your charge controller set to that recommendation?
160826
User avatar
Vtec44
Teardrop Builder
 
Posts: 41
Images: 1
Joined: Wed Apr 10, 2019 2:51 am
Location: So Cal
Top

Re: Need LiFePo4 battery and solar help.

Postby RJ Howell » Fri Sep 13, 2019 6:39 am

I use these meters. One coming and one outgoing. I like these because they have cumulative watt hrs. https://www.amazon.com/Digital-Multimeter-DROK-6-5-100V-Voltmeter/dp/B07KPXVNY5/ref=sr_1_12?keywords=12v+meter&qid=1568376624&s=hi&sr=1-12

Is your charge controller designed for lithium? Not just any will work and charge properly.
What lithium battery did you buy? I bought a 100ah unit and it only tested out to 40ah
RJ Howell
The 300 Club
 
Posts: 417
Images: 34
Joined: Sat Jul 27, 2019 6:08 am
Top

Re: Need LiFePo4 battery and solar help.

Postby John61CT » Fri Sep 13, 2019 12:57 pm

Link to battery, ideally a manual, or at least a data sheet.

And yes, what are the settings on that SC?
John61CT
1000 Club
1000 Club
 
Posts: 1372
Joined: Thu Nov 17, 2016 4:36 pm
Top


Return to Electrical Secrets

Who is online

Users browsing this forum: No registered users and 1 guest