two or more Li-poly batteries in parallel?

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Hi All

 

I am using 4.2V 2200mah li-poly batteries and also charging them using Li-Poly charge at 500mA.

 

Is it safe to join 2 or more batteries in parallel to increase the capacity for my application?

 

Thanks

 

 

Thanks

Regards

DJ

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I would not do it. Order a bigger battery. It might be smaller than two individual units.

Unless your charger can charge them independently and manage them during dischege look dor a better solution

Jiust my opinion though

Jim

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djoshi wrote:

I am using 4.2V 2200mah li-poly batteries and also charging them using Li-Poly charge at 500mA.

Is it safe to join 2 or more batteries in parallel to increase the capacity for my application?

 

What is "batteries"? Are you talking about multi-cell pre-assembled batteries with built-in protection circuitry? Connecting these in parallel, especially for charging, might not be a good idea.

 

If you are talking about naked "aluminum pouch" LiPoly cells, then connecting these in parallel is perfectly fine. We have been doing it in R/C applications on everyday basis for a long time already. It is basically a "standard" thing to do. Just make sure that the cells are identical and have the same state of charge at the moment when you join them. They will automatically maintain balanced state as long as they are connected.

Last Edited: Fri. May 17, 2019 - 10:52 PM
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I have read "on the net", as the saying goes.
That when some manufacturers make a battery pack they match them.
And if these batteries are from the same pack and have been through the same cycling conditions, that individual supervision of each battery may not be required.
I have been using batteries from such a pack and have found no problem with not individually supervising each battery.
The batteries I have been using came from avionics equipment, where I work they are changed regularly, and were made in the good 'ol USA.
I also recharge them at a very slow rate, so they don't even get warm.
Have run them like this for years and a check shows they still show identical voltage and charge.
I use them in a low level LED lighting units in systems though out my house.
Charges in the day off the solar system and they turn on at night from their own local battery, thus not loading the main battery system overnight. Also not affected by power outages.
I only use processor controlled PWM variable rate charging on them, and with temperature sensing on the pack for safety.
Did hardware and software for them, I call them "The world's most complicated lights".
Have an LCD to show various parameters and any problems, so far none for many years.
I have encased them in heat shrink and they are in a die cast case sitting in a thick steel plate.

Last Edited: Sat. May 18, 2019 - 08:25 AM
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jgmdesign wrote:

I would not do it. Order a bigger battery. It might be smaller than two individual units.

Unless your charger can charge them independently and manage them during dischege look dor a better solution

Jiust my opinion though

Jim

 

Ok it is just that i got 100's Li-poly batteries , and thought I could combine two or three to increase capacity.

 

Thanks

Regards

DJ

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Surprisingly - this paralleling is very common.

 

Example 1:

I have had a Bosch drill battery rated at 18V 4Ahr. It failed so I pulled it apart. It consisted of 10 Li-Ion cells in size 18650, a series combination of pairs of paralleled cells.  There was a thermistor buried between them and a simple LED bargraph voltmeter chip. This pack failed because one cell became leaky (literally) and that discharged it's twin resulting in low voltage for the entire pack. Most of the other cells were good though and it has been a good source of 18650 cells for other experiments and equipment.

 

Example 2: I have a workshop LED lamp. It's a big yellow floor standing thing that illuminates a large area. The Li-Ion cells inside are 3 18650 all in parallel. Just two wires connect this pack to the lamp but there is a long narrow PCB buried within the wrapping of the cell. it carries what look like a SMD fuse & an IC . I would have to destroy it to reveal more.

 

Example 3:

OK, This is an extreme case where Tesla manufacture an individual 24V battery module consisting of 6 series connected groups of either 74 or 86 cells. Their battery pack consists of 16 of these modules connected in series.

 

Enjoy the pictures and note the individual cell fuses for safety.

https://teslamotorsclub.com/tmc/threads/pics-info-inside-the-battery-pack.34934/

http://skie.net/skynet/projects/tesla/view_post/20_Pics+and+Info:+Inside+the+Tesla+100kWh+Battery+Pack

 

 

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AndreyT wrote:

djoshi wrote:

I am using 4.2V 2200mah li-poly batteries and also charging them using Li-Poly charge at 500mA.

Is it safe to join 2 or more batteries in parallel to increase the capacity for my application?

 

What is "batteries"? Are you talking about multi-cell pre-assembled batteries with built-in protection circuitry? Connecting these in parallel, especially for charging, might not be a good idea.

 

If you are talking about naked "aluminum pouch" LiPoly cells, then connecting these in parallel is perfectly fine. We have been doing it in R/C applications on everyday basis for a long time already. It is basically a "standard" thing to do. Just make sure that the cells are identical and have the same state of charge at the moment when you join them. They will automatically maintain balanced state as long as they are connected.

 

Yes they have a protection circuit. The batties as shown in the image.

https://cdn.shopify.com/s/files/1/2311/3697/products/lithium-polymer-battery-1000mah-batteries-and-chargers-contains-generic-oem-cool-components_576_x700.jpg?v=1547033570

 

Is this the Aluminum pouch you mentioned?  The cells are all identical and from the same batch as well.

 

What is meant by the same state of charge?   Do you mean the charge level?

 

 

 

Thanks

Regards

DJ

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Just go to hobbyking.com and order up a 2200mAh 2P pack and you are done. Packs for RC use properly matched cells and usually bring out an internal connection point so the balance can be checked during charging. They may also include thermal monitors too.