Charging LIFePo4

[tx2sturgis]

Yes to all that,

but a batt could only show lower,  not higher right?

Yeah I doubt any normal, rechargeable battery we would be using could show a high enough voltage to 'fool' the controller.

This same technology is used on laptop chargers and many other consumer devices.

I haven't tried this but let's say you had 2, 12v batteries that were each discharged to 7 volts. Hook them up in series.

Then attach an auto-sensing controller like the Victron and presumably it will settle on 13.8 volts!

Ooops...

 

[John61CT]

Any 12V chemistry I know of, get down to 7 even 9V it's dead dead.

With LFP that would be permanent, no coming back even in "limp along for another season" mode.

And even with super tolerant FLA I would definitely do immediate 20-hour load testing after any attempt to resuscitate; if 20% down on rated capacity straight to the scrap yard.

 

[tx2sturgis]

Any 12V chemistry I know of,  get down to 7 even 9V it's dead dead.

Yep...it was a hypothetical. Not a recommendation, as I said, I have never done it either.

 

[Zardor]

Thank you guys for having this discussion. Just today I set my max to 14.6 per battle born's manual for recommended settings. I just dropped it to 13.8 as you guys have recommended. I'm a complete noob and appreciate seeing information like this.

 

[John61CT]

Out of all the drop-ins that's one I've heard good things about by people that have had them more than a few months.
But no long-term (years) reports from credible testers, dropins are just not generally taken seriously for House bank usage by the boats and expedition truck crowd. Plus if the only batt, blowing out electronics if the BMS shuts off.

Their G31 does fit nice in an ArkPak 730, but I know at least the builtin charger on that isn't LFP suitable so not worth the money IMO, I'm sure we could DIY a better value portable kit from a Pelican type box or ammo can.

Sure beat the big Yeti too!

 

[jimindenver]

Today she was getting 25a when the sun broke though and bank was up to 13.3v after being at 12.5v this morning.

I thought Kat spoke to you so maybe she should list her system. The controller is a Victron 60 amp I believe. She was going to use the Morningstar until they told her it would die if the battery was disconnected while the solar was still connected. She also has a issue of having the 60 amp breaker going off occasionally which is odd because even on a 60 amp controller her panels don't have the ability to produce that kind of amps.

Interesting stuff

 

[John61CT]

Today she was getting 25a when the sun broke though and bank was up to 13.3v after being at 12.5v this morning.

I thought Kat spoke to you so maybe she should list her system. The controller is a Victron 60 amp I believe. She was going to use the Morningstar until they told her it would die if the battery was disconnected while the solar was still connected. She also has a issue of having the 60 amp breaker going off occasionally which is odd because even on a 60 amp controller her panels don't have the ability to produce that kind of amps.

Interesting stuff

Amps are OK then. You talking resting V or with the SC pumping? Loads isolated yet?

Have not comm'd with Kat other than public threads, my memory's shot, don't keep track of who's got what nor take time to search for past threads.

Don't think anything specific to Victron is an issue here. What model? Kept within specs? Hook up to PC possible to see logs and any settings customization ?

I only use fuses at big amps, trustworthy CBs way too pricey.

 

[tripper]

I'm still testing my drop in LiFePo4. I had dropped the voltage down to 13.8 volts but noticed a considerable loss in usable amp hours (as measured by the lowest voltage the battery drops to overnight powering a Whynter 12v fridge). I am using a Victron 85 amp controller, which btw also claims it will blow up if disconnected from battery while solar power is flooding in. I noticed the battery only takes 2 hours to fully charge at 13.8v bulk and takes 3 hours at 14v bulk; this charging is all down during the first few hours of morning daylight, so anywhere from 1 to 30 amps going in.

I know in theory the 13.8 volts should charge the battery almost as well as 14v, but in practice on this particular battery/controller it does not appear that way. I will continue testing out the battery.

 

[VanKitten]

In l o n g. Conversations with Justin at Victron....he assured me that the disconnect of the battery with solar still connected would cause no harm. This is the reason I selected Victron in the first place.

The Victron dial is set to 7. LIFePo4. That is all.

So, last week John and I spoke on the phone....hey, you were stuck in traffic in Texas at the time. We concluded that the Victron was probably the problem. In doing diagnosis with Justin on the phone...he came to the same conclusion I am barely limping along with this Victron. Cannot continue like this. Yesterday Justin said he would shipping immediately, that very day (Monday) a replacement so I get it by Friday. Then he didn't.

So...I am going to set the charge side relay to cut out at 14.8. Per manufacturers spec. Since that is what the cell manufacturer says...that is the number I will use. Then...I am going to install that Morningstar 60 and figure out how to do the set up.....have it cut off at 14.6.... just to keep it below the drop-dead level the relay will use. I have had this new Morningstar in a box since June. Was going to trade it at the swap-meet.

However...since the Morningstar is not intended for lithium....I get no answers from their tech service. I am seeking answers here on how to set each and every parameter on the Morningstar. That is my original question.

 

[John61CT]

as measured by the lowest voltage the battery drops to overnight powering a Whynter 12v fridge

What is the voltage before and after?

How big is the bank, vs average AH draw of the fridge?

My understanding is the actual capacity difference even between 13.8 and 14.4 is low single digits.

Good prismatics usually are rated lower than they ship. In all cases the 13.8 Full point has actually still been a higher capacity than rated, at least after the breaking in period.

Of course that may not be the case with all prismatics, or any drop-ins, never seen the latter properly tested to know.

Only way to really tell is 20-hour load testing. Too many variables with voltage curves for that to really tell anything accurately.

 

[John61CT]

However...since the Morningstar is not intended for lithium....I get no answers from their tech service. I am seeking answers here on how to set each and every parameter on the Morningstar. That is my original question.

OK, I'll try to remember to leave the voltage issue alone for you, you've certainly gotten that input.

What else do you need that isn't covered in my canned blurb?

Hit your voltage and stop, that is all, no Absorb stage, no Float.

Since no charge source does that automatically, see if you can remember to do it manually whenever it's convenient.

Unless you want to try my previous suggestion to use an adjustable OVD relay to cut the connection between the panels and SC.

The real-life compromise all LFP owners I've discussed this with do, is:

set Absorb hold time to absolute minimum, adjusting target V down if that has to be more than a few minutes.

and set Float to 13.1, so there is no actual measurable current flow.

Put your clamp meter on, and make sure you are **not** letting trailing amps drop below 2-3A (opposite of Lead logic). With that higher voltage personally I advise using 5A.

All these suggestions are based on the original objective of avoiding damage to longevity which comes from overcharging.

That high Absorb setpoint is already taking you way past that point, so IMO it's even more important for your case to follow them.

But the "canned" LFP settings on the Victron unit (which I also told you to avoid) would probably have been just as bad or even worse.

I have been told by authorized Victron dealers, that they were designed to work strictly in conjunction with the Victron packaged LFP systems, large prismatic cells managed by their proprietary external BMS. I think it's possible the two devices are intended to be coordinated with each other, perhaps by an AH counting calculating device.

Since all the charge profile parameters are at least as adjustable as the Morningstars (AFAIK) IMO that is the better way to accommodate non-Victron batteries.

Again, there are no charge sources on the market claiming to be LFP ready that actually do the right thing.

The key to success is user customizability of the setpoints.

So, if you have questions on the meaning or ramifications of any of the programming options on the Morningstar unit, feel free to ask about them, ideally one at a time, and we'll do our best to help.

 

[VanKitten]

Perhaps you did not look at the Victron model. -TR

It has a dial on the bottom....instructions are...for LIFePo4 set dial to number 7

That is the total "canned" settings on this model. No other parameters, etc. just set the dial and done,

 

[John61CT]

Perhaps you did not look at the Victron model. -TR

It has a dial on the bottom....instructions are...for LIFePo4 set dial to number 7

That is the total "canned" settings on this model. No other parameters, etc. just set the dial and done,

Yes. If that is addressed to me, I'm not sure what the point is. Again, I would not advise anyone to use such a setting. On any charge source device on the market.

A user customized profile, as in not a "canned" one, that lets you tweak the setpoints is the way to go.

Which I believe is just as available on your Morningstar?

If you already got all that above and were not addressing me, sorry pleasr ignore.

TR?

 

[tripper]

I believe the Victron controller is excellent for LiFePo4 batteries as all functions are user definable. I agree with John that I would not use the factory set LiFePo4 switch.

My Victron, on a typical day is taking 3 hours to achieve BULK (0730 to 1030am) sitting at around 32 amps by 1030 this time of year (flat solar panel), then switches to ABSORB, the absorb mode is very short lived, it usually takes 15 minutes for it to hit float from absorb mode.  The absorb is programmable on the Victron, I believe I can set it to 1 minute if I want. I do not see why the Victron won't work as a lithium charger, it reads right out on the screen the voltage and current. The Victron allows you to set the voltage, any current you want (0 to 85 amps on mine), the absorb time, and the float voltage. Mine also has a built in relay that is user voltage setable.

As I said earlier though I found I needed to set bulk/absorb to 14 volts on the controller to get a good usable capacity on my lifepo, 13.8 volts on mine noticeably lessened the usable capacity. 13.1 volts float seems like it might be a hair too low also, the controller will not send any charging to the battery for about 20 minutes once a load starts as the battery sits around 13.15 volts under light loads and has to drop to 13.1 before it trickles power to it.

I have a stand alone computer controlled 120 volt lithium 15A charger, it does not do as well as my Victron in my opinion charging the battery.

I suspect I may have some voltage loss between the solar controller and the battery and that is why I need to set it to 14v instead of 13.8

 

[tripper]

Switch 7 (LiFePo4 setting) on the Victron Controller (mine has it too) sets Bulk/Absorb to 14.2 volts and float to 13.5. It also turns off temp compensation and equalize modes.

BTW older firmware on the Victron controllers allowed for a different BULK and Absorb voltage, but now they have one combined field.

 

[John61CT]

13.1 volts float seems like it might be a hair too low also, the controller will not send any charging to the battery for about 20 minutes once a load starts as the battery sits around 13.15 volts under light loads and has to drop to 13.1 before it trickles power to it.

Actually that is a good thing. Remember, LFP sitting at high SoC is actually unhealthy, you **don't** want to "keep the bank full" for more than a few minutes.

So, you should only let your bank get to full when you know loads are going to start pulling SoC right back down.

If you know the solar will carry the loads, the optimum would be letting it do that while keeping the bank at a low SoC, then using solar to charge the bank later in the day.

Yes it seems counterintuitive, but that's the biggest challenge managing LFP, unlearning "lead thinking".

Have you got a good AH-counting BM?

 

[John61CT]

BTW older firmware on the Victron controllers allowed for a different BULK and Absorb voltage, but now they have one combined field.

Excellent, I always thought that was a bit odd, never came across a batt vendor recommending separate values, and it does complicate things.

My theory was that using a higher V increases acceptance without harm in early stages, "fast charging" when it causes no harm, and then you lower V as SoC is higher to avoid overcharging.

 

[ZacLee]

Actually that is a good thing. Remember,  LFP sitting at high SoC is actually unhealthy, you **don't** want to "keep the bank full" for more than a few minutes.

So, you should only let your bank get to full when you know loads are going to start pulling SoC right back down.

I think being concerned about keeping the batteries at 100% charge for more than a few minutes is a bit excessive.  While lithium chemistry batteries do age faster when stored at full charge, the difference would not be significant unless the batteries were stored that way for weeks or, at least days.  In daily cyclic use, this should not be a concern.  Limiting depth-of-discharge (to perhaps 75% depth-of-discharge) has a much larger effect on battery life.

 

[John61CT]

Yes of course to that last.

But the point remains, as to breaking the lead mindset, and why there should be no Float.

Best and easiest IMO is to just manually charge, no real need to put things on automatic, and no real need to bother with solar in many cases, under an hour's charging every once in a while's all you need, just do it when you need it.

 

[tx2sturgis]

 Limiting depth-of-discharge (to perhaps 75% depth-of-discharge) has a much larger effect on battery life.

This is only part of the equation.

Any battery will last 'longer' (measured in number of years) if used less, but, are you actually getting more 'use' out of it?

Probably not. 

If you discharge a battery only 25% for 600 times, or 50% for 300 times, its the same amount of 'life', measured in total number of amp hours or watt hours derived (not counting peukert's derating curves).

If you never discharge the battery at all, ever, then it will last a VERY long time....but you will have gotten little use out of it.