# connect 2 LiPo batteries in parallel?

I'm trying to add this PowerCell Quickstart Guide - SparkFun Electronics to my system , so that it can run on a battery.

but even given a 2000mAh single cell battery, the capacity still looks low.

so is it feasible to connect multiple LiPo batteries in parallel and treat it as one ?

thanks
Yang

You could do that if the cells are identical (same AH capacity and hopefully same manufacturer)
You need to verify they are both charged to the same voltage before making the parallel connection.

It is not practical to do this because they will age differently. You at least have to pass the output of each through a diode before joining them together to stop them cross charging.

Grumpy_Mike:
It is not practical to do this because they will age differently. You at least have to pass the output of each through a diode before joining them together to stop them cross charging.

All examples I've ever seen just connect them together directly, after ensuring that they're charged as closely as possible to the same voltage.
It's very, very common to see them connected in this way, without diodes. I've never seen diodes used.
(I'm talking about two cells of the same capacity, made by the same manufacturer, and the same age.)

teddyyyy123:
I'm trying to add this PowerCell Quickstart Guide - SparkFun Electronics to my system , so that it can run on a battery.

but even given a 2000mAh single cell battery, the capacity still looks low.

so is it feasible to connect multiple LiPo batteries in parallel and treat it as one ?

thanks
Yang

My friends have Quadcopters and R/C Airplanes that use parallel connected LiPo batteries all day, every day, without any diodes.

As pegwatcher stated:

1. Same Make & Model & Manufacturer
2. Same size / mah
3. Charged to same voltage - measure before connecting in parallel

Not a problem. You can safely connect them in parallel!

Just make sure that the voltage is pretty equal before, otherwise a lot of current cal flow for a short moment.

// Per.

My friends have Quadcopters and R/C Airplanes that use parallel connected LiPo batteries all day, every day, without any diodes.

Connecting batteries in parallel is stupid no matter who does it friend or not.
Perhaps the only people who might recommend it are those that are interested in selling batteries.

Grumpy_Mike:
Connecting batteries in parallel is stupid no matter who does it friend or not.
Perhaps the only people who might recommend it are those that are interested in selling batteries.

It's done in commercially sold batteries. Series, parallel and series-parallel.

Grumpy_Mike:
Connecting batteries in parallel is stupid no matter who does it friend or not.
Perhaps the only people who might recommend it are those that are interested in selling batteries.

There is absolutely no problem in putting Lithium chemistry in parallel, with one caveat: They need to be the same chemistry.

The good thing about Lithium is that the SOC and voltage follows along just nicely, so there is absolutely nothing wrong by connecting a 100Ah and a 1Ah cell in parallel.

Battery University
Cited from site: "Most battery chemistries allow parallel configurations with little side effect."

// Per.

Zap,
If you're gonna quote, then quote it all.....
"Most battery chemistries lend themselves to serial and parallel connection. It is important to use the same battery type with equal voltage and capacity (Ah) and never mix different makes and sizes. A weaker cell would cause an imbalance. This is especially critical in a serial configuration because a battery is only as strong as the weakest link in a chain. An analogy is a chain in which the links represent the cells of a battery connected in series (Figure 1)."

From that, sounds to me like the diodes might be a good idea (added safety).

Electric car batteries use a combination of series and parallel connections.

From that, sounds to me like the diodes might be a good idea (added safety).

If you perceive safety as a concern, make the parallel connection with a polyfuse, or better, a fast blow fuse. Diodes drop the voltage by 0.7 volts, a large loss in efficiency and complicate the charging process.

teddyyyy123:
I'm trying to add this PowerCell Quickstart Guide - SparkFun Electronics to my system , so that it can run on a battery.

but even given a 2000mAh single cell battery, the capacity still looks low.

so is it feasible to connect multiple LiPo batteries in parallel and treat it as one ?

thanks
Yang

Looking to start a fire, eh? Don't parallel LIPO... EVER!!!!!!!

See pages 34 and 35.

Pegwatcher
You are not suggesting that the batteries be charged in parallel are you?

Grumpy_Mike:
Pegwatcher
You are not suggesting that the batteries be charged in parallel are you?

It's done that way in almost every laptop, thousands of times a day.

Typical laptop internals, a 3S2P-setup:

// Per.

Of course, why not? The new parallel combination is treated as a single cell, in every way.

Grumpy_Mike:
It is not practical to do this because they will age differently. You at least have to pass the output of each through a diode before joining them together to stop them cross charging.

Grumpy_Mike:
Connecting batteries in parallel is stupid no matter who does it friend or not.
Perhaps the only people who might recommend it are those that are interested in selling batteries.

QuadCopter LiPo Battery Packs, with parallel cells, come prepackaged from the manufactures.
They are called "3S2P".
3S means 3 cells in series.
2P means 2 cells in parallel.
This combination of 6 cells has been working perfectly for over 200 deep cycles, now.
Where do you get your information that it does not work?

Example of a 3S2P Battery
3S2P LiPo Battery

You are an odd sort of cove mrsummervill, you insist that you need a resistor for input pins for safety any yet you insist that this is safe.

Still no accounting for foybols is there?

I am fed up of this slanging match. Go to bed.

The 36V 16Ah lithium battery in my bike is made up of 70 cells connected in a series-parallel configuration, 10s7p. It's lithium-ion though, not lithium-polymer. Not sure if that makes a difference?