Charge controller recommendation

Anything electric, AC or DC

Charge controller recommendation

Postby TimC » Thu Aug 19, 2021 8:20 pm

I have two Renogy 100w panels (RNG-100D - wired parallel). I'll be installing a LiFePo4 battery bank soon(100aHr). I've been using an Epever Tracer 3210N MPPT charge controller for my old AGMs and it has worked well. It is LiFePo4 compatible but I can't seem to find information about limiting it to charging to 80% or 90% charge on the new batteries. Searching other forums it seems to be quite the task to program it; if it can be done at all. So, I'm thinking of upgrading to a smart ch controller. I'm hoping it is smart enough to be user friendly. I'm not confident about that though! I'm not one to monitor production and load beyond what my two ammeters tell me. So bluetooth is not necessary but it looks like that is the way the market is going. I just won't use that capability much.

My panels are rated as follows (each):
Pmax 100w
Voc 22.5v
Vmp 18.9v
Imp 5.29a
Isc 5.75a

I'm not sure which value I multiply by two and add 25% to determine a charge controller that fits (Imp or Isc). I see Lauren has the Victron 75/15 smart Ch Cont. Would that be suitable? I'd like to keep the price around $100.

Thanks,
Tim
Tim
Niagara, WI
My First Benroy Teardrop Build Thread - A 5x8 Woodie - http://www.tnttt.com/viewtopic.php?f=50&t=63575
My Second Teardrop (partial) Build Thread - Started August '16 - http://www.tnttt.com/viewtopic.php?f=50&t=66939
#3 My son's Benroy Foamie team build - Started July '20 - http://www.tnttt.com/viewtopic.php?f=50&t=72877

Image
User avatar
TimC
Gold Donating Member
 
Posts: 1364
Images: 732
Joined: Sat May 23, 2015 4:15 am
Location: WI/MI border

Re: Charge controller recommendation

Postby saltydawg » Thu Aug 19, 2021 10:25 pm

Use the victron 15 amp, the odds of ever seeing 15 amps out of the panels would be slim. And you could feed it with 100 amps and you will only ever get 15 out of it. It just cant send more out, it wont matter.

as for settings go in to the custom battery settings and set the max voltage at 14.2-14.4, with the storage voltage at 13.6.

or do the settings here if you want to be more precise.
https://diysolarforum.com/ewr-carta/diy ... arameters/
Scott
Lost in Maryland
2021 just said to 2020, hold my beer and watch this.
saltydawg
500 Club
 
Posts: 647
Joined: Tue Apr 24, 2012 8:34 pm
Location: Maryland

Re: Charge controller recommendation

Postby John61CT » Fri Aug 20, 2021 4:17 am

The ideal definition of Full for LFP longevity in normal cycling

is "13.8V and stop" isolate the LFP bank from the charge source, no holding Absorb / CV stage at all.

This can be accomplished with a simple HVC circuit, for use with any charge source.

And only charge to Full a short time before loads need to start feeding off the bank. Do not Float the bank at any voltage

When not actively cycling, keep them isolated between 12.4 and 12.8V, but never allowed to drop below 12V.
John61CT
1000 Club
1000 Club
 
Posts: 1958
Joined: Thu Nov 17, 2016 4:36 pm
Top

Re: Charge controller recommendation

Postby TimC » Fri Aug 20, 2021 6:54 am

Thanks guys.

I'm taking another look at my Epever. I actually have the MT50 remote meter and haven't used it as I didn't care about remote monitoring. I just found a reference to programming the Epever via the MT50 to set User parameters for the new LiFePo4. I have no idea what they are describing but I want to investigate/study this further before changing to the new smart charge controllers. I'm hoping the MT50 will allow me to program the charge controller to stop charging at about 90% SOC. I'm guessing that I have some work to do to figure out how that is done. Doing a capacity test sounds like the first step.

Will P has a video on programming the MT50 for a Battleborn LiFePo4. Until I hear from my battery supplier for their suggested parameters I am going to go with those changes. However, I don't know if Will's suggestions will accomplish what I am trying to do... charge to 85-90%.

Tim

Image
Tim
Niagara, WI
My First Benroy Teardrop Build Thread - A 5x8 Woodie - http://www.tnttt.com/viewtopic.php?f=50&t=63575
My Second Teardrop (partial) Build Thread - Started August '16 - http://www.tnttt.com/viewtopic.php?f=50&t=66939
#3 My son's Benroy Foamie team build - Started July '20 - http://www.tnttt.com/viewtopic.php?f=50&t=72877

Image
User avatar
TimC
Gold Donating Member
 
Posts: 1364
Images: 732
Joined: Sat May 23, 2015 4:15 am
Location: WI/MI border
Top

Re: Charge controller recommendation

Postby saltydawg » Fri Aug 20, 2021 8:37 am

John61CT wrote:The ideal definition of Full for LFP longevity in normal cycling

is "13.8V and stop" isolate the LFP bank from the charge source, no holding Absorb / CV stage at all.

This can be accomplished with a simple HVC circuit, for use with any charge source.

And only charge to Full a short time before loads need to start feeding off the bank. Do not Float the bank at any voltage

When not actively cycling, keep them isolated between 12.4 and 12.8V, but never allowed to drop below 12V.


Again your wrong, 12.4-12.8 is basically between 10 and 20% soc. Every manufacture and user who knows what they are doing keeps them around 60 to 80% charged or around 13.2 volts for long term storage. Lifepo4 has around a 5% self discharge, so trying to store it at 10-20% means any where from 2 to 4 months the battery is going to be at zero and start hurting its self.

Also another thing your wrong on is top voltage, you need to every so often charge it to 14.0 or more depending on the bms, ideally right before use. As most bms wont start cell balancing around that until some where over 14.0. You should also do this at low current if possible.
Scott
Lost in Maryland
2021 just said to 2020, hold my beer and watch this.
saltydawg
500 Club
 
Posts: 647
Joined: Tue Apr 24, 2012 8:34 pm
Location: Maryland
Top

Re: Charge controller recommendation

Postby John61CT » Fri Aug 20, 2021 4:44 pm

A badly designed BMS should not dictate abusive charging.

But sure so long as you can see your cell level voltages a good pack cared for properly might only need rebalancing once a year so NBD.

And 14V as a high point is 3.5Vpc much better than datasheet maximum, again OK.

A 60% SoC storage setpoint is fine too, but 80% is way too high. 12.8V isolated at rest is more like 50%, that is why LFP is nominal 3.2V

10% is close to 12V, but for practical purposes best to call it zero.

Good quality LFP cells have near zero self-discharge isolated in cool conditions, even over 15 years. So long as no circuitry is hooked up, especially BMS, very often the cause of expensive banks getting murdered.
John61CT
1000 Club
1000 Club
 
Posts: 1958
Joined: Thu Nov 17, 2016 4:36 pm
Top


Return to Electrical Secrets

Who is online

Users browsing this forum: No registered users and 9 guests