How to Charge Batteries in Parallel With Different Capacity

In this video, I will show you the ins and outs of how to charge batteries in parallel, mainly focusing on charging lithium batteries and LiFePO4 batteries in parallel. I'll dive deep into what you need to consider if you're dealing with different capacity batteries in parallel, ensuring you understand the critical aspects of wiring batteries in parallel to maintain balance and extend their lifespan.

Wiring batteries in parallel is more than just connecting cables; it's about understanding the chemistry behind your batteries, whether lithium or lead-acid, and ensuring they're matched for optimal performance. I'll explain why it's crucial to use batteries of the same voltage and chemistry and what happens when you mix different types or capacities.

Charging lithium batteries in parallel comes with its considerations, especially when ensuring each battery shares the load equally to prevent premature aging called current sharing. I'll show you how connecting batteries in parallel differs from a series connection, including how batteries in parallel balance themselves automatically, a feature not shared when wiring in series.

The video also covers the importance of current sharing among batteries wired in parallel, demonstrating with practical examples how to achieve optimal wiring configurations for both small and larger battery setups. You'll learn why busbars may become your best friend for minimizing resistance and ensuring even current distribution across all batteries.

For those curious about wiring different capacity batteries in parallel, I'll address the common concerns and scenarios where it might be necessary, providing clear examples to help you understand the potential impacts on performance and lifespan.

Selecting the right fuse and wire sizes is critical when wiring batteries in parallel, and I'll guide you through the calculations to ensure safety and efficiency. Whether you're expanding an existing solar system or building a new one, understanding the role of fuses and the correct gauge of wiring is essential for protecting your investment.

Whether you're a seasoned solar power enthusiast or new to the concept of charging LiFePO4 batteries in parallel, this video is packed with valuable insights. I'll share tips on expanding your solar system by maximizing capacity without increasing voltage, ensuring your batteries deliver power more efficiently and last longer.

[bradk]

Thank you so much for the generous candid info that is presented so CLEARLY.
Received your book from Amazon three days ago 👍

[mrhalfstep]

I wasn't searching for this topic exactly, but your site was the first hit that I got. You didn't address the issue that I was asking about, but I bet that you are the guy that can answer my question, all the same, and other folks may also have the same question, so if I might....
I have an assortment of 12.8 volt LFP batteries that are of various ages, but none have seen a lot of use. They also vary in their capacities from 100AH to 300AH. I have them to connect to various inverters as I need them when my power goes out, rather than all connected together to one big grid down backup system. It's just the way it has evolved for me as I started fooling around with LFP batteries. They keep getting cheaper and lighter and smaller and I keep buying them. My issue is that I want to have them stored in a convenient place with some sort of charger that will keep them at a good maintenance charge until I need one of them. I'm old and I just don't trust myself to remember to go around and charge each one if I suspect I'm going to need it during a spat of bad weather, for instance. I want them to always be at the ready when they need to be put into service. They won't have any load on them, they will just be sitting on shelves.
My vision is a 20 amp charger set to 14 volts or so, connected to 2 solid aluminum bus bars, about 3/8 X1/2 inch in cross section, with a bunch of 12 AWG wires with small alligator clips connected to them so that I can unclip a battery, use it, leaving the other batteries connected, and then return it to be reconnected when I'm finished with it. Maybe even several batteries at one time. I may make it a little more sophisticated than that, but that's the basics. My question is, do I need to be concerned with keeping wire lengths the same and fusing each charging lead, since I'm not going to be actually discharging them while they're in the rack?
Thanks very much for any help you can offer.

[pathfinder]

Just watching the video made me hit the like button and you showing all the wirering diagram made me hit the Sub, thanks for sharing

[kenkrommenacker]

Thank You for all the info, and also just ordered your book.

[aaronb]

i never considered all those issues. Everything you said made complete since to me.

[philbrooke-little]

Lithium and lead acid work very well together so long as the lithium has a programable BMS. The advantage of doing this is that it saves the cost of having to get lithium profile chargers and it protects an alternator in the event of a BMS disconnect. It also gives redundancy. I’ve been running hybrid for several years and so have many other boaters.

[donm]

Thank you for the PDF download, I just want to say that your disclaimer with conductor sizing based on the 90°C column really should be based on the 75°C column because most devices that will be terminated to that cabling will not be rated with a 90° C termination. Therefore the possibility of excessive heat being transferred through the terminations to the device could either destroy the equipment or cause a warranty issue.

[DiHandley]

What an excellent and very helpful channel. I have just installed 3 x 120a 12 volt batteries in parallel connected via two very thick solid copper busbars for a total of 360 amps. I took the negative off the first battery and the positive off the last and then ran them up to separate busbars for distribution to - 240vac/12dc charger, dc to dc converter and a 3000 watt inverter. I hope I did the right thing. I have now subbed to your fantastic channel. Thank you.

[jeremygrebe]

Hi
From Colombo, Sri Lanka
I am using a microtek 2335 hybrid inverter, 2 x 12v 200ah Okaya Opgel and 3 x 375 REC panels.
I operate with smart metering ie - Day time 5.30 am - 6.30 pm, Peak 6.30 pm -10.30pm, Off peak 10.30pm - 5.30 am.
I auto switch off the peak time by way of timer and contactor thereby zeroing peak current and charge in off peak, and save during day time via solar.
Net saving has been almost 65%.
My house is single phase and I have split wired my house as follows.
1. All lights, fans, TV, Fridge, audio including plug points in room through inverter /solar hybrid.
2. Iron, Oven, Microwave, Electric Kettle, Air Fryer, Washing Machine induction all direct to grid.

Although system works fine if I operate at full capacity during peak I found my battery id's almost fully utilized and insufficient if I have an extended power cut.

Watching your video I want to increase this same system by 6 batteries of same type. Make 3 sets of 24v x 200ah and connect each set to a 24v/200ah 5 stage intelligent charger ( so total 3 sets of batteries & 3 chargers) I will set a timer/contactor to charge these during off-peak and day time only.
This will give me 19w reserve and hopefully many years of use.
I intend connect 1st set to hybrid inverter and balance 3 sets as tag on parallel (with their grid chargers)
Please advise your thoughts.
Thanks and Regards
Jeremy
PS - Anyway I can discuss with you [phone]

[subbuk]

Excellent explanation one query please, I have connected 3 batteries in parallel first 200mah second 200 mah and the third 150 mah to an inverter 950VA/12V, what will be charging and consumption sequence, request your feedback thanks

[ChrisSgaraglino]

I just watched this video, thank you! I have (4) 100Ah batteries going into my exiting 12v RV with a 1000W inverter. Each battery has a max in/out of 100A. I also have a 150/35 Victron Solar Controller. I’m going to use your Bus Bar recommendation, but I am a little confused on what size fuses I should put on each battery. A little help here would be much appreciated!

[davidhughes]

Question: I have 2 100 AH batteries and one 200 AH battery wired in parallel to busbar. Do you recommend a charging equalizer?

[rzroluo]

At the 5:00 mark of the video, you have shown that the load from the inverter, and all of the chargers (solar & battery charger), are all connected to the same buss bars, and therefore to the same "corners" of the battery array.

I have 4x 6v lead acid batteries in a typical series/parallel arrangement. I was advised some time ago, that the +/- connections for the CHARGING circuit, should be at "opposite" corners of this battery arrangement, while the +/- connections for the LOAD circuit, should be at the opposing corners of the battery arrangement. So, the charge connections are at opposite corners compared to the load connections.

How important is this? Your diagram is simpler and makes sense to me!

[tombloemker]

Love your explanation! I want to build a dc power box, with solar charging. I want to use various tool batteries of the same voltage but diffrent capacities. Could I connect the charge controler to the bus? I assume the cut off would not hurt the smaller capaticy packs?

[jamesalles]

Personally, I would avoid mixing differing capacities with lead-acid chemistry. I believe that is following most manufacturers recommendations, also.

[Aphong]

What if i want to charge it from a separate solar charge controller?

[Milldog]

So glad i found this page, im just about to hook up inverter and a ton of wet batteries i bought pre cov, i noticed one of the solar panels has a nick in the rear panel bit. I still ok to use? i have a pip 2424msxe brand new, So i have a feeling im gonna be loving this page for sure.

[jhay_mstv]

Clear! Thank you sir, I'll subscribe

[cndbrn]

I have a 72v 40A (max) 500watt (motor) and i'm thinking of using 4 12v 18ah lifepo4 batteries and 2 12v 20ah lead acid batteries.

The 4 to be wired in series and the 2 acid to power a boost converter, to gain the extra
24v needed? Using a bus bar to connect the 4 & 2 together before connecting to the boost converter, then to the load.

Can you give me any insight to this arrangement? ..

[rainerinedinburgh]

I think you've made a mistake. You emphasize the importance of having the same series resistance in the charging wires. You correctly recommend a pair of bus bars from which the wires to all battery terminals are of equal length. But your alternative solution for 5 batteries does not achieve equal resistance. If you have five batteries with four red and four blue link wires as shown at 2:50, then for batteries 2, 3, and 4, the series resistance consists of two link wire resistances (counting from the points where the main red and blue cables first split). There are two blue links for battery 2, two red links for battery 4, and one red plus one blue for battery 3. So far, so good. But batteries 1 and 5 each have four link resistances (one red plus three blue, or three red plus one blue). Surely, for equality, the main red wire should go to battery 1 and the main blue wire to battery 5. That way each battery has four link resistances in series with it.