Parallel charging Lifepo4 batteries of different brands and sizes! Extreme Parallel Part 2! 

You can use different amp hour capacity batteries together, the problem is when you are discharging them in parallel. Each batteries different amp hours will kick off the lower amp hour batteries when the BMS turns off on your lower amp hour batteries. And that can cause strain on your other higher amp hour batteries. Also when you charge all your batteries together it can get out of balance on all your different battery cells. Best to keep batteries same amp hour rating and voltages together. They will balance better and drain better without their BMS turning them off.

Yo need to use atleast 8 awg gauge wires. Keep in mind you need to use fuses that are rated a little higher than your amp hour battery. So if you have a 50ah battery then you can use a 70 amp fuse, if you want to be safe you can use minimum 50 amp fuse. But fuses need a little leeway for amp draw. You use 12 awg gauge wire for anything lower than 30 amps. Any amp loads that are higher, such as your lifepo4 battery, use higher amp fuses and lower gauge wire.

That's incredible!

Excellent, your experiments tell all, thank you!

Very interesting, just like being in science class. Well done.

You answered my question of have same voltage batteries with different storage capacities. Thank you

good show , i might add another batt from other brand to my kit now

Thanks. Interesting. I was thinking about adding to my small cabin system. Looking forward for the journey. Thanks again.

That was interesting how the charge fluctuated to get each battery fully charged. It's good none of them received too much!

You need to leave the charger connected for 30 minutes per 100 Ah of capacity. This will give the BMS time to balance the cells, this is the absorption cycle. You will notice during this time a small charge going to the battery. If this is not done the cells will soon be imbalanced affecting performance. Once absorption finishes they should be close to 14.2 volts.

Interesting experiment. I suspect the voltage differences and the varying amp push/draw might be due to each pack having cells made by different manufacturers, that there may be some variances in those that affected how they took in charge and their voltages, and how their voltages dropped when taken off charge. Might also be some differences with the BMSs causing some unexpected variances as well.

Exactly what I wanted to see. It proves that all batteries will eventually charge completely. Also the gauge of wire isn’t a factor since during the final charging there is such a low current.

The length of the cables must be the same to have a perfectly balanced system, and I doubt that dissimilar batteries can ever be balanced. I would expect differences in charging and discharging between them which would likely cause some to fail sooner than others. I like your experiments!

Awesome vid many thanx from aus.

This was a cool series of videos. Thank you for sharing. I've been too scared to try this due to the long-time warning of keeping safe size and brand of battery.

I'm thinking that you are going to be limited by the battery with the lowest "full charge" voltage. With that battery, if you charge it to more than that, it is going to drop down to that once you disconnect it from the charger. The battery with the higher "full charge" voltage will then be charging the lower voltage battery, but the lower voltage battery will not stay at that level, thus the charge is wasted. This will continue until the higher "full charge" battery is at the same level as the lower "full charge" battery. Another way to visualize this would be like water flowing into tanks... Let's say you have two open top tanks, each 13.7" tall, but one of them being 10" wide and the other being only 5" wide. Let's also says that you have a water supply hooked up to both that will allow you to fill each up to the 13.7" level. Let's also run a small diameter line interconnecting the bottom of the two tanks so that they seek equilibrium. And lastly, let's add a small overflow hole near the top of each tank -- at the 12.5" level on the smaller tank and at the 13.4" level on the larger tank. These overflow holes might not even be the same diameter which would thus simulate different discharge rates. You fill the two tanks up to 13.7" which causes the water supply to be shut off. At this point, but tanks are leaking water out the overflow holes. The larger tank is going to get to it's overflow level and the water will stop coming out of it. If the smaller tank has not reached this level yet, then it will continue until it reaches the level of its overflow hole. But since the two tanks are connected and the smaller tank has a lower overflow hole, the water from the larger tank is going to flow into the smaller tank through the interconnect line. This will raise the level of water in the smaller tank above the overflow hole which will cause the water to go out it. This is going to continue until the larger tank is at the same level as the smaller tank. With a battery bank, this energy has go go *somewhere* and it is most likely dissipated as heat due to that whole "Conservation of Energy" thing that we *should* remember from high school Physics class...

I'd never have considered charging different amperage batteries in parallel, like this. Theoretically it should be fine! They all have Control Modules, which should be fine, "theoretically". I think you have just provided evidence it works in practicle application. So long as all the batteries together do not draw more current than the charger provides. I thinnk, Right? The question is, how do they survive long term in such an configuration. Also, would the results be the same (or similar) using a solar array? Good test.

What you find very strange at 6:45 I found to be completely expected. You connected the cells together when they were somewhere down the SOC curve but there is no way to know where each is because the curve is so flat. The 100Ah was obviously at a lower SOC when connected and it doesn't really matter how long they are connected, they will not get close until you take them to near 100%SOC. I would also say that your wires are too small and all the same gauge. You would be better off by connecting paralleling wires between the three + and three -. I connect my paralleled batteries with 4/0 cables so that they are all at the exact same voltage. Your system was always going to have different voltages on each of the batteries and that is not really parallel. To be parallel, all batteries must be at the exact same voltage and that is only done by having interconnecting wires big enough to not produce voltage drops to each battery. As for your tester. Those usually have less than 180w for the max draw. You said that your three batteries have a total capacity of 425Ah so at a nominal voltage of 12.6v that comes to 12.6v x 4250Ah = 5,355W. at 180w discharge max that will come to about 30 hours for the test.

thank you very much for this video i like it...

Thnks now i know🙌🏻

Great Video. 👍

I had a lot of questions on this on the subject of hooking up batteries with different mah but same volts in parallel. I have about 15 18650 batteries all with different mah and few have no label to know the mah of the battery, so I was wondering what would happen if I hook them all up, but I think your video has shed more light on that (i.e they all even out) And while charging, it all depends on how dumb your charger is to not figure out that one of the batteries is fully charged. Am About moving to the part three. please can u make a video to show an EASY way to check the mah of batteries

Really great video, Can you show me your charger and where to buy it ?

Now do 2 lead acid and 2 lithium and make a 48v and see how that goes.

Hellow sir, can i parallel the lifepo4 32650 ang gel type batteries? 120ah lifepo4 and 50ah gel type batteries?

Late to the party, but this video is saying that you can mix different types of lithium batteries on a charging block. I want to know if I can mix a couple of different 100ah lithium batteries on my camper? I bought a camper a few months ago and it has one 100ah battery and I would like to add a 200ah battery in my battery box so that I have 300ah. Will it safely charge both batteries off of the solar?

Hmmm interesting. Another test will be w a load and charger. And then solar w the different batteries and mppt. I’ve always tried to use same battery models in systems out of paranoia of balancing over many cycles and loads of battery w heaters as we operate off grid in them wild. Will be interesting to see your tests

So in the end they balanced themselves out?

Settings wheel--->Playback Speed--->1.25

voltage does not tell the full story on lifepo, top balance them together is a good idea, still, it will work no probleme, i do that with my battery bank, one is 24v 280, the other is 230 and the last one is 130 amp, no probleme for month .

Wish I had this much time to waste...

Nice experiment