I have tons of used 18650's from old laptops. Is it possible to hook them all up in parallel so that I don't need to worry about balancing them and increase the voltage to 220? I would like to use them as a free battery bank possibly with solar panels. Any thoughts/ideas? Thanks

 

I have tons of used 18650's from old laptops. Is it possible to hook them all up in parallel so that I don't need to worry about balancing them and increase the voltage to 220? I would like to use them as a free battery bank possibly with solar panels. Any thoughts/ideas? Thanks

Unfortunately, no. Those cells don't balance well. OEMs get away with it because they enforce specifications and can even sort cells to ensure each cell in a pack is as similar as possible to the others. After a lifetime in a laptop, followed by a time in storage, there's no way they'll be the same.

Putting then in serial is problematic also, because a weak cell in the chain will see a damaging reverse voltage.

For goofing around you could attempt to sort cells into series strings of 3 or 4. This would give you enough voltage to power an inverter to get your 220VAC. Strings could be placed in parallel to get the current you need. Just don't expect much longevity to its all.

 

Welcome to AAC!

Is it possible to hook them all up in parallel so that I don't need to worry about balancing them and increase the voltage to 220?

You meant connecting in serial, and, no, connecting a bunch of mismatched batteries to get 50 times their nominal voltage isn't a good idea.

I would like to use them as a free battery bank possibly with solar panels.

Litium ion batteries don't take to charging abuse. Lead acid is more common.

Any thoughts/ideas?

Connecting batteries in series and/or parallel is a compromise. It should only be done with batteries in the same relative condition.

Paralleling Li-ion batteries can result in shorts and fires. Connecting them in series will quickly kill the weakest battery.

 

220 DC or AC?
Not answering your question but perhaps pointing out another thing you might need to study!

 

Thanks for the responses. I meant to ask if there is a way to bring up the voltage even though they are all connected in parallel ie an inverter. @DraxDomax you're right, I meant AC not DC.
To summarize, if I parallel tons of these batteries it can cause a short/fires? Why is that? I thought that putting them in parallel would cause the voltage to be evenly distibuted?

 

To summarize, if I parallel tons of these batteries it can cause a short/fires? Why is that? I thought that putting them in parallel would cause the voltage to be evenly distibuted?

https://batteryuniversity.com/learn/article/serial_and_parallel_battery_configurations

 

Thanks for the prompt reply! In other words it seems like I should just throw them out? Any suggestions what I can do with tons of old 18650s?

 

Thanks for the prompt reply! In other words it seems like I should just throw them out? Any suggestions what I can do with tons of old 18650s?

Sort them by condition and use them like you would for any other 18650. Just don't think you can put dozens of them in series or parallel.

I have dozens of AA NiMH batteries. Over time, some of them get weak and eventually die. I label the weak ones and don't use them with batteries that are in better condition. When I change the batteries in a device, I do a quick check to see if one or more are significantly weaker than the rest. The weak ones get marked and separated from the stronger ones.

When you have several batteries in series, stronger batteries will drive the weaker ones into reverse voltage if the pack is allowed to run down. Reversing at low current is enough to kill batteries.