Solar controller for lithium batteries

[Michael4104]

Hi all, been reading some great info for a while now. So I decided to ask a question and hoping for an answer.
I have 2 2kw 48v lithium batteries from a Chevy Volt battery pack that I have reconfigure to 16v. The reason for 16v is do to charging problems. If I configure them for 12v they will get over charged using the alternator or a non programable solar controller. 12.6v is the max voltage, but I prefer 12.4v.
I need a charge controller that I can program to 12.4v and not go into float mode. Anyone have a solution? 
Ps. I now charge my 16v setup with a solar charger set to Gell (14.1v) and the alternator. Safe, but not very efficient. I have three of the latest and greatest 160w panels so says the manufacturer.

 

[John61CT]

If they're designed for 48V why not keep that, run a 48V inverter and use DC conversion to step down for 12V use?

48V is bog standard for solar, much easier to work with, cheaper wiring. . .

 

[Michael4104]

Your right, but my van is not a off grid home. It is already setup with 320 watts of solar panels a 30 amp tracer charge controller and a 2000 watt inverter. I just want to change my controller.

 

[John61CT]

Sorry in re-reading I'm not clear what your actual setup is, nor how what I said isn't right for a van.

Your bank came out of a 48V setup, how many cells of what voltage are now in each series, how many parallel banks? AH ratings?

What chemistry? What is the per-cell max charge voltage, how much at rest, say 90% full?

You say they currently work at 16V, being charged at 14.1 and you want to charge them at 12.4? I'm too confused. . .

What is the max real-life volts of each panel? Max real-life amps output at 12V? Putting them in series with a right-sized MPPT from Victron may get you a lot more power output, and you can set custom voltage to the bank.

This is likely overkill, but just as an example:
http://shop.pkys.com/Victron-Energy-MPPT-10030-Solar-Charge-Controller_p_3666.html

But since you'll also have to deal with the alternator (concurrently with solar? shore power charging too?) maybe best if you run your charge inputs bog-standard profiles into a big cheap lead starter, and then use a big Battery-to-Battery DC-DC charger with customizable setpoints like Sterling to be your single source output from the LA to the oddball bank.

Just ideas. . .

 

[SternWake]

So I decided to ask a question and hoping for an answer

I apologize, I wish i could be helpful, but I do no know the answers with any significant degree of confidence and wil not speculate in an attempt to be helpful.

We do have a member here who is familiar with lithuim batteries, and actually employs them. If blars decides to step in on this topic, He is the member on this site with the most experinece regarding lithium batteries, as far as I know.

Used Chevy volt batteries employed in this lifestyle...... Well i wish I could answer your questions with any degree of confidencce. I cant . So I wont


Lead acid, fire away. Lithium, sorry

 

[John61CT]

Google says these are a new proprietary Li NMC chemistry from Argonne not LFP. they're not releasing details on setpoints.

I'd say only for techie pioneers willing to take arrows in the back.

 

[blars]

If I was dealing with these, I'd probably use them at 48v and use DC-DC converters for what needs to be 12v. Unlike LiFePO4, your volts per cell can't do a good match to 12v. 48v positive ground stuff is common in the telco industry.

 

[John61CT]

Lots of standard electronics and marine gear designed to go up/down to/from 48V as well.

Trending up in automotive as well
https://www.google.com/search?q=48+volt+automotive

And the 75% lower Amps per Watts can mean huge savings in wiring, switching, fuses etc.

 

[Michael4104]

Ok
The Chevrolet Volt has a 16 kWh / 45 A·h (10.4 kWh usable) lithium-ion battery pack.

I have two 2kw section of the Chevy Volt battery each being 48v I have rewired them to be 16v. The battery is made up of 12 modules of 4.2v at 15 amps. So I rewired it to be 4 modules in series. That equals 16v, but still at 2kw (180 amp), but wasteful.
The reason I did that is because they don't want to be charged more than 4.2v per cell, less is better.
I want to rewire them to 12v. Three modules x 4 equals 12v still at 2kw (180 amps)
We have use this setup using a BMS, but it not very reliable. BMS breaks down.
So I want a charge controller that will charge at 12.1v and not do a float charge.

 

[John61CT]

There may well be others, but the Victron series I linked to above let you set absorption and float equal to each other (so no float), and the current floor stop point.

And also as I said, if you select the model able to handle the voltage of all your panels in series, you can save money by getting the one with the lower Amp rating (or have more room for expansion), and the MPPT functions are likely to give you significantly higher total power output per day.

But note (again) if you are also looking to use other charging sources, like a shore charger and your Alt, then I recommend putting your "smarts investment" into an adjustable B2B like Sterling and route all your more-stock thus cheaper source regulation through that via an off the shelf lead starter.

And finally, maybe you know this but "lithium ion" is not specific enough to inform anyone of the optimum charge parameters.

I believe you specifically have the first-generation NMC formulation from Dalhousie University's Professor Dahn that GM licensed from Argonne National Laboratory.

I hope you are keeping up with the reverse-engineering on this proprietary chemistry since AFAIK the manufacturer hasn't made the current best practice charging specs public since they found deal-breaking problems with the first-gen chemistry.

My point is keep questioning and researching that 4.2V number within the EV community, your cells are not stock LiCo and LiMn nor LiFePO4.

 

[Michael4104]

I am looking into the Victron controller you mention. Alan at Bay Marine Supply is running some test.
I also have a 12v 90amp power wall that I made using 18650 lithium batteries. They have the same charge requirement as my Chevy Volt battery pack. The Chevy volt battery is made with pouches and the Tesla battery is made with 18650 batteries. So I'm not showing any favorite. ?

 

[John61CT]

I've heard Alan's great, does he actually have the Chevy bank to work with?

And I'd love to see how you built that Panasonic "wall", what series/parallel array matrix, how'd you physically connect them? Total cost?

 

[tripper]

The Victron controllers will do exactly what you want. I have three of them and one is on LiFePo.

You can set the float so low that it will never go on, or you can set it to a very low point, say 11v, to prevent completely discharging your batteries.

The way I set my float I believe is slightly below resting voltage for the battery, so when just sitting there it is not sending any charge, but when I use an appliance, say my microwave, the voltage just dips enough so that it goes into float and the solar panels run the appliance (for example it will be putting out 600 watts in float), not discharge the battery. When i shut the appliance off the float generally shuts down within a few minutes.

If I am not using any power the float is not doing any trickle charging, which is great for a LiFePo battery.

When the battery voltage is higher than the float voltage the float just shuts off on the Victron. I use one and it works well. The Victron has 0.01v resolution, which allows you to set it accurately.

 

[jimindenver]

I have custom set several lithium banks on Morningstar MPPT controllers too. Easy to set with MSview and a computer. I use a serial to USB cord but it can be done wirelessly.

 

[VanKitten]

There is two different types of lithium commonly used for RV, cars, etc.

LiFePo4 (Iron Potassium) and LifeyPo4 ( rare earth lithium yttrium).

The charging needs are a bit different for each.

Ask the manufacturer for the spec sheet. LiFePo4 is the more common in RV and marine applications because it is more stable. YPo4 is more common in cars .. etc. it sounds like you might have both? In your planned system? I guess that is true because you say that your batter cells were from various applications.

 

[John TF]

Having been into recycling electronics , I ended up with lots of 18650's mostly from laptop's , I have reconditioned and labeled each for there milli-amp rating , so when I have enough of one group for a project , have many , one of which is to build a power wall .
Have followed lots of lithium battery studies , videos etc.
I did not get the impression that you were combining the 2 battery types , so with that covered .
And this in generic , with repurposing [ pulling from another system - that had BMS ] vs. most of the over the counter 18650's have a BMS chip in the battery - not counting those .
You can build a circuit / board with a min. 3 cut-outs , 1 for max charge voltage , 1 for min charge voltage and the 3rd for over-temp - many times this can be just fuse wire to each cell .
A full BMS covers a lot of things , but for a builder - you just need the above - 3 cot-outs & fusing each cell for over current .
It's not as complicated as general web-search implies - thats mostly lawyers / insurance companies .
But the the old standard is you need to learn & operate at your own to build .
A couple lithium battery builder guys on YouTube -
https://www.youtube.com/channel/UCcMfCkN1juSa49DJFYltOTw
https://www.youtube.com/channel/UC0pBauLp63yzf6sVdEOIUbA

 

[Weight]

I have seen listings for the 18650 size cells using different Li chemistry. Don't mix and match. Play carefully out there.

 

[John61CT]

There is two different types of lithium commonly used for RV, cars, etc.

LiFePo4 (Iron Potassium) and LifeyPo4 ( rare earth lithium yttrium).

There are many many "lithium" cell types.

Large prismatics like CALB, GBS are LFP, aka lithium iron *phosphate*, aka LiFePO4.

Lithium yttrium iron phosphate (LYP) in prismatics is usually Winston, aka ThunderSky, aka Voltronix aka Sinopoly (various brands, spinoffs, same cells) is really just a slight variation from LFP.

Both are very suitable for mobile House banks, just pricey and finicky to care for.


NMC is a very common lithium chemistry for powering EVs and small powerpacks, often cells are pouches, also those little cylindricals like 18650s, high energy density but short lifespan and risky wrt thermal runaway.

 

[Technomad]

Anyone want to recommend off the shelf LFP supplier? I’m probably going to build a very large bank, 500-1000 AH. I don’t want to build up from CALB cells, would rather have a bullet proof BMS-included system to work with.

At this point looks like BattleBorn Batteries are what I need. But they’re about $1k per 100AH vs $600 for DIY.


Sent from my iPhone using Tapatalk

 

[VanKitten]

Beware....battle born is even clear on their website that their pre-set specs on the chargers will NOT be the best for longevity.

At that price point....knowing you are throwing away some of the expected life of those batteries seems like the move a person with a lot of money to burn..now and in the future.

After more than 2 years of research, and 9 months of hands on with my own system...I can tell you that the trade off is always going to be....knowledge for money. The less you are willing to learn, the more you will have to pay.