Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
li ion and NiMh
#1
I was wondering, (i bet i am not the only one here. Big Grin )

Is it possible to connect a 24v NiMh pack on some 24v li ion packs?
For example: 4 x 24v li ion packs and add one NiMh pack also 24v.
The whole system will be 24v.

The thing is, i also have obtained a 80 -100 good 1,2v NiMh cells above 7500mah.
I wont like to throw them away.
Or will it be a to big hassle to going to use them for energy storage in combo with li ion.

Thanks in advance
Still learning English. Learning Li ion and solar technology.
+/- 1500 Li ion cells harvested, none checked and counting.

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
Reply
#2
(03-04-2019, 08:22 PM)100kwh-hunter Wrote: I was wondering, (i bet i am not the only one here. Big Grin )

Is it possible to connect a 24v NiMh pack on some 24v li ion packs?
For example: 4 x 24v li ion packs and add one NiMh pack also 24v.
The whole system will be 24v.

The thing is, i also have obtained a 80 -100 good 1,2v NiMh cells above 7500mah.
I wont like to throw them away.
Or will it be a to big hassle to going to use them for energy storage in combo with li ion.

Thanks in advance

A double no.

Voltages are different, charging behaviour is different, charging losses are different, discharging voltages are different.

You can sure use NiMh, but have to deal with them separately.
Korishan likes this post
0,8kWp in Test
4 kWh battery target
Ultra low cost
Reply
#3
Hmmm, shoot, to keep it polite.

Then i understand the german hybrid power wall builder wrong.
He used(i thought) in combo with li ion and some lead battery's to build a hybrid system.

I will read his documents and work again.
For my NiMh they will be build in a led light for my use at my work.
The agm battery is getting old (12v 45 amp), its done in one hour instead of two

Thanks for youre replay it is very welcome, i have a lot to learn and read again.

With best regards
Still learning English. Learning Li ion and solar technology.
+/- 1500 Li ion cells harvested, none checked and counting.

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
Reply
#4
In theory the answer is yes, you can use them together. However you shouldn't connect them in parallel because of all the reasons that have already been given. So in practice that is a No for your use case. However you could connect them in series though if you like to create a higher voltage battery, but that also comes with its own drawbacks.

A hybrid system will most likely use some sort of transfer switch to switch the load between two otherwise separated systems. Can't imagine someone is using a hybrid lithium and lead acid system with both chemistries active at the same time. You could do it but it wouldn't make much sense.
Reply
#5
In a nutshell that will be my dilemma when going to li ion.
Right now I have a 48V nominal lead acid bank that is being maintained with solar. It will have at least another 3 to 5 years of life in it.
I am in the process of collecting at least 2800 18650 cells for a 14s200p bank.
The question is how to separate the 2 banks.
My thought is to have a switchover system that can feed the lead acids till they are full and then automatically switch to the li ion bank to continue charging that. Or visa versa whichever will work the best.
I was thinking of placing a capacitor bank on the bus bars positive and negative to kind of absorb the shock of the quick changeover from a fully charged bank to a depleted bank and allow the mppts and inverters to stay connected. The inverters themselves have capacitors in them but this would reduce the shock to them.
At least that is my thinking.
Question would I have to switch both the neg and pos or keep a common neg and just switch the pos?
The other dilema is the mppts would need to be adjusted to the different chemistries every time.
Or do I just charge the li ion bank and figure out a creative way to "float" the lead acids as more than likely those will only be used in an emergency.

Wolf
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 70mΩ or less Smile
Last count as of 3/22/2019
Total Number of Cells           3679
Cells  >80% of Capacity        2389
Cells <80% of Capacity         1265
Cells ≥2200mAh & ≥ 80%     1653
Google Drive for info https://drive.google.com/drive/folders/1...sp=sharing
Not your average Wolf       
            Cool



Reply
#6
You probably want to split your solar in half with dedicated chargers and inverters for each chemistry and then switch the load between them.
Reply
#7
(03-06-2019, 07:24 PM)DarkRaven Wrote: You probably want to split your solar in half with dedicated chargers and inverters for each chemistry and then switch the load between them.

That was my initial thought also and I may still do that for the sake of simplicity. The problem is that the lead acids really don't like to be exercised like the li ions. You really can't pull down a Pb chemistry to ≈1.96V esentally ≈90% DoD on a consistent basis without repercussions esp. if you have a slow solar day the next day. Additionally cycle life is drastically reduced.
So my thought is to keep the Pbs at reserve charge in essence on float. Give them an occasional exercise so they dont forget that they are batteries after all. Problem is if I split my Solar then I am wasting at least 80% of that split on nothing as the batteries on float really don't take anything to keep them there. A this point I am cycling them between 90% to 100% SoC.
Now with li ion that does not become so much of a problem if we go from 4.1V to ≥ 3V. Also charging is not an issue as we don't necessarily have to go to 100% SoC so the bad solar days won't have as much of an impact on our battery chemistry matter of fact li ion likes it a little lower anyway.
So in conclusion yes splitting would be the easiest solution but not the most effective at least I think.  At this point I partially agree with you but I want to avoid the 80% loss of solar if I split my system.

Wolf
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 70mΩ or less Smile
Last count as of 3/22/2019
Total Number of Cells           3679
Cells  >80% of Capacity        2389
Cells <80% of Capacity         1265
Cells ≥2200mAh & ≥ 80%     1653
Google Drive for info https://drive.google.com/drive/folders/1...sp=sharing
Not your average Wolf       
            Cool



Reply
#8
What's the capacities we're talking about here and how much solar power do you have? Maybe a ratio other than 50:50 might be a solution. Or maybe you can go 100% lithium and repurpose the lead acid batteries. It's not really the most sophisticated advice, you probably don't need me to tell you that this might be an option Big Grin
Reply
#9
(03-05-2019, 08:19 PM)100kwh-hunter Wrote: Hmmm, shoot, to keep it polite.

Then i understand the german hybrid power wall builder wrong.
He used(i thought) in combo with li ion and some lead battery's to build a hybrid system.

I will read his documents and work again.
Link, please. I am german.

(03-06-2019, 08:58 PM)Wolf Wrote:
(03-06-2019, 07:24 PM)DarkRaven Wrote: You probably want to split your solar in half with dedicated chargers and inverters for each chemistry and then switch the load between them.

That was my initial thought also and I may still do that for the sake of simplicity. The problem is that the lead acids really don't like to be exercised like the li ions. You really can't pull down a Pb chemistry to ≈1.96V esentally ≈90% DoD on a consistent basis without repercussions esp. if you have a slow solar day the next day. Additionally cycle life is drastically reduced.
So my thought is to keep the Pbs at reserve charge in essence on float. Give them an occasional exercise so they dont forget that they are batteries after all. Problem is if I split my Solar then I am wasting at least 80% of that split on nothing as the batteries on float really don't take anything to keep them there. A this point I am cycling them between 90% to 100% SoC.
Now with li ion that does not become so much of a problem if we go from 4.1V to ≥ 3V. Also charging is not an issue as we don't necessarily have to go to 100% SoC so the bad solar days won't have as much of an impact on our battery chemistry matter of fact li ion likes it a little lower anyway.
So in conclusion yes splitting would be the easiest solution but not the most effective at least I think.  At this point I partially agree with you but I want to avoid the 80% loss of solar if I split my system.

Wolf

I second your thoughts on the behaviour of the chemistries. So hold Chargers and Batteries separate, and switch the PV, not split it. In steps or groups.
The inverters can stay , switch them as well.
just my 2 cts idea.
0,8kWp in Test
4 kWh battery target
Ultra low cost
Reply
#10
Everything has a value. Unless you have a personal attachment to your batteries, sell them! And then put the money towards 1 chemistry. That's my advice. Or else you will be chasing 2 inverters, 2 charge controllers, etc, for a set of batteries that dont really have that much life left in them. Dunno how much you have Wolf, but 100kwh-hunter has <1kwh of NiMh, and that's 1% of 100kWh!
Reply


Who read this thread?
46 User(s) read this thread:
Sean, Korishan, PAF, wim, watts-on, Stefaan De Ridder, BlueSwordM, Geek, DarkRaven, ChrisD5710, Oz18650, Jensk, Charly144, djuro, drchips, gpn, Crimp Daddy, Ibiza, Cherry67, Gummiadler, Sammm, emuland-metroman, Beholder, Wolf, Bastler_Ro, camthecam, Dallski, stevelectric, ajw22, kevinjaye, LEDSchlucker, Powersaver, Richard, Church1182, beserker786, Aussioffgrid, Lucan, Havskum, Greenbatt, mixedbrasil2014, FishStormEight, 100kwh-hunter, graphenebattery, JimU, fatpeter55, JonSon

Forum Jump:


Users browsing this thread: 1 Guest(s)