Mixing lipo and lithium ion batteries

Batteries, Chargers, and Battery Management Systems.
Post Reply
wall0069   1 µW

1 µW
Posts: 4
Joined: Apr 02 2018 8:54pm

Mixing lipo and lithium ion batteries

Post by wall0069 » Apr 02 2018 8:56pm

Lithium ion batteries have high specific energy and lipo have high c rating (high power). Is it possible to put lipo and lithium-ion batteries in parallel if they are at the same voltage and protected by charge control or BMS circuitry? This would give you a battery that has high energy density, but can also deliver short bursts of high power. The lipo would charge up from the lithium ion then deliver high power when needed the way capacitors are commonly used. It would be isolated from the circuit by transistors which would control charging and discharging.

User avatar
Sunder   1 GW

1 GW
Posts: 3038
Joined: Sep 06 2011 11:24pm
Location: Sydney, Australia

Re: Mixing lipo and lithium ion batteries

Post by Sunder » Apr 02 2018 9:26pm

Yes, its possible. Depending on use and diffefence in cell performance, you might not even require the control circuitry you describe.

I am running a 36S LiPo woth 43S LiFePo4 for 18 months with no issues.

I have also run 8S LiFePo4 with 11S LTO for 8 months with no issues.

No control circuits for either.
eBike: Q100H on 16S with Phaserunner FOC Controller
eMotorscooter: Vectrix VX-1 Died... Electrified Ninja in Progress!
eCar: Mitsubishi Outlander PHEV... Warramty expired. Still not game!
eHouse: 6.2kw On-grid solar with battery backup coming soon!

After 5 builds, the best advice I can give, is start with high quality products. I prefer http://www.ebikes.ca

billvon   100 MW

100 MW
Posts: 2864
Joined: Sep 16 2007 9:53pm
Location: san diego

Re: Mixing lipo and lithium ion batteries

Post by billvon » Apr 02 2018 11:00pm

wall0069 wrote:
Apr 02 2018 8:56pm
Lithium ion batteries have high specific energy and lipo have high c rating (high power). Is it possible to put lipo and lithium-ion batteries in parallel if they are at the same voltage and protected by charge control or BMS circuitry?
Sure. I've done it with both Lipo+LiFePO4 and Lipo+NiMH. As long as you make sure the voltage ranges and charge/discharge rates are within the safe limits for both batteries, you are good. You will not get good balance (i.e. the discharges will be neither balanced per pack nor consistent across the discharge curve) but you will get significantly more energy.
This would give you a battery that has high energy density, but can also deliver short bursts of high power.
Well, not quite. You have to make sure that both batteries can handle the max discharge rate. But if both are OK with the max rate, you will definitely see more power due to the reduced ESR.
The lipo would charge up from the lithium ion then deliver high power when needed the way capacitors are commonly used. It would be isolated from the circuit by transistors which would control charging and discharging.
That's completely different, and is way different than putting two batteries in parallel. And will generally reduce both battery life and total power. I'd advise against that.
--bill von

fopoku2k2   1 µW

1 µW
Posts: 1
Joined: May 11 2021 4:33am

Re: Mixing lipo and lithium ion batteries

Post by fopoku2k2 » May 11 2021 4:37am

Sunder wrote:Yes, its possible. Depending on use and diffefence in cell performance, you might not even require the control circuitry you describe.

I am running a 36S LiPo woth 43S LiFePo4 for 18 months with no issues.

I have also run 8S LiFePo4 with 11S LTO for 8 months with no issues.

No control circuits for either.
I need help connecting my existing 16S2P 48V Nissan leaf LIPO battery banks to a new 16S2P 48v LIFEPO4 prismatic cell banks

Thank You

Sent from my Pixel 4a using Tapatalk


leffex   1 kW

1 kW
Posts: 325
Joined: Apr 08 2012 4:39pm
Location: Sweden

Re: Mixing lipo and lithium ion batteries

Post by leffex » May 11 2021 12:16pm

Possible. Yes

But they may have different voltage curves and their specific energy may be in different voltages areas.

So lipos have energy in the higher voltage range and if you compare them to 18650 li-ions they may have their most energy in a lower area around 3,5-3,8v area

What effects does this have to parallell different performance cell?
I don't know more than I'm letting go of my setup of 18s 18650s and 2 s lipo and a 1slife4po. Not because of performance issues but I like to use a technology that is less risky. Also if noted I use a 1s of life4po which is kind of a safety cell as it will just "eat" over-voltage if charged to much for any reason. For my usage it's not needed but it adds a layer of security to my battery.

When paralleling two different battery packs of different types you may have one pack giving out 20% power and the other the rest, that is 80% when the whole pack is fully charged at 100%. However meanwhile and when it is being used this ratio may change as the packs charge each other to make the voltage even between the two paralleled packs. When you are reaching 0% SOC in totalt it may change as well and maybe so much that it's not useable. Or it will be useable. To start you need to follow and check as you go to as not anything bad is happening your batteries when they are being discharged or charged. Like that they don't get to hot to touch or similar.
Salestech in an ebike store

fatty   10 kW

10 kW
Posts: 672
Joined: Nov 14 2020 9:15pm
Location: USA

Re: Mixing lipo and lithium ion batteries

Post by fatty » May 12 2021 9:40pm

wall0069 wrote:
Apr 02 2018 8:56pm
Lithium ion batteries have high specific energy and lipo have high c rating (high power).
LiPo can have specific energy (~220Wh/kg) matching all but the very highest cylindrical cells (~230Wh/kg).

User avatar
fechter   100 GW

100 GW
Posts: 15761
Joined: Dec 31 2006 3:23pm
Location: California Bay Area, USA

Re: Mixing lipo and lithium ion batteries

Post by fechter » May 12 2021 10:09pm

fopoku2k2 wrote:
May 11 2021 4:37am
I need help connecting my existing 16S2P 48V Nissan leaf LIPO battery banks to a new 16S2P 48v LIFEPO4 prismatic cell banks

Thank You

Sent from my Pixel 4a using Tapatalk
Without resorting to a dc-dc converter, you'll have to change the cell count to match the voltages. A 16s LiFePO4 will have a maximum charging voltage very close to a 14s Li-ion pack. As others have pointed out, they have different discharge curves, so there will be a tendency for one to do more of the work in the beginning and there will be some losses from charge shuttling between the packs if the load is not constant
"One test is worth a thousand opinions"

JackFlorey   100 kW

100 kW
Posts: 1310
Joined: Feb 19 2020 7:22pm

Re: Mixing lipo and lithium ion batteries

Post by JackFlorey » May 12 2021 10:48pm

fopoku2k2 wrote:
May 11 2021 4:37am
I need help connecting my existing 16S2P 48V Nissan leaf LIPO battery banks to a new 16S2P 48v LIFEPO4 prismatic cell banks.
You can't do that directly. What you can do:

1) Change the S count to match the operating voltages of each pack. For example, a 16s LiFePO4 might work OK with a 14s Li-ion as long as you matched them in voltage first. It won't work perfectly. You will almost certainly need to charge them separately.

2) Use a current limited buck to drop the 58 volts from the 16S Leaf pack to the 52 volts of the 16s LiFePO4 pack. That would allow you to run the Leaf pack almost flat, then (effectively) switch over to the LiFeP04. By adjusting the current limit you could play with how fast the Leaf pack discharges into the 'main' battery.

Post Reply