Lipo: series vs parallel

[MFM]

Ok I want to explore this a little. I under that running two lipo packs in series will give more power and parallel will give you longer run times.
my question is when doing this do the batteries have to be identical. I know it’s the safe way but that’s not what I’m asking. Example : series- 6s 5000mah 100c + 2s 5000mah 100c = 8s 5000mah 100c?
parallel - 6s 5000mah 100c + 2s 5000mah 100c = 6s 10000mah 100c ?
Do the batteries have to have to same specs to safely run them in series or parallel? I’m not trying to blow my poop up or burn out my equipment here. I’m trying to grasp more info on running series vs parallel. I have a few different lipo batteries.
(2)spektrum 6s 5000mah 100c soft packs, 2s 5000mah 100c hard pack, 3s 5000mah 100c hard pack.
power hobby 6s 6500mah 100c softy,
HRB graphine 6s 6000mah 100c softy.
Orion 4s 7200mah 15.2v 120c hard pack

I’m trying to figure out which ones I can run in series for 8s vs which ones would be safe to run parallel (if any).
Thanks. I hope this makes sense. I’m usually a one batt per rig but looking to safely expand on powa!!

 

[Performance nut]

On paper, your reasoning has some logic to it. Execution, they will fight each other in parallel (safety issue), be limited by weakest link in series (safety and economics issue). If you choose to try this, have a fire extinguisher handy that is rated for LiPo fires.

Voltage differences you quoted are too great to risk. Stick with similar voltages.

 

[MFM]

On paper, your reasoning has some logic to it. Execution, they will fight each other in parallel (safety issue), be limited by weakest link in series (safety and economics issue). If you choose to try this, have a fire extinguisher handy that is rated for LiPo fires.

Voltage differences you quoted are too great to risk. Stick with similar voltages.

What about running the spektrum 6s 5000 100c w 2s 5000 100c. Both spektrum both new-ish (3 runs on ea) in series for an 8s run? It’s not for bashing just for a few speed runs?
or are you suggesting that I buy 2 new 4s 5000 100c in series for my 8s speed runs?
When running parallel; assuming mah identical between batts, does the cell count and discharge rate (c) also have to match? So in theory, running parallel AND series should ONLY be done w two identical packs?
I almost bit the bullet and purchased a 8s pack but quickly realized I don’t have the charging capacity for an 8s lipo...
thanks again.

 

[arrmadillo]

Whenever I run 2 packs together they are always same brand, mah, voltage, C rate, age.

 

[JvG]

Always use exactly similar lipo's when connecting them in series or parallel, it's not like LEGO.

 

[Performance nut]

What about running the spektrum 6s 5000 100c w 2s 5000 100c. Both spektrum both new-ish (3 runs on ea) in series for an 8s run? It’s not for bashing just for a few speed runs?
or are you suggesting that I buy 2 new 4s 5000 100c in series for my 8s speed runs?
When running parallel; assuming mah identical between batts, does the cell count and discharge rate (c) also have to match? So in theory, running parallel AND series should ONLY be done w two identical packs?
I almost bit the bullet and purchased a 8s pack but quickly realized I don’t have the charging capacity for an 8s lipo...
thanks again.

Its not the brand, its the voltage. 6s runs at 22.2V and 2s at 7.4V. You should never run batteries in parallel with that much of a voltage gap. In theory they should work but in reality it doesn't work that way. If memory serves me, when connected in parallel the lower voltage battery will heat up and fail (usually resulting in a fire). In series, I still believe the 2s will fail but not 100% on that.

Folks tend to use the same manufacturer because they are putting faith in the manufacturer's ability to produce consistent batteries. Mixing manufacturers puts to the possibility of inefficiencies but not necessarily dangers (unless one battery is poorly designed). Again, in theory a 6s 5000mAh 100C battery is the same no matter who makes it. In reality, there are different ways to make a battery and always corners that can be cut. Sometimes these "differences" don't play nice with each other. With that in mind, sticking with the same manufacturer that you trust is always a good policy but not necessary a requirement. Sort of like tires, you don't put 4 different brands of tires on your car expecting to get the benefits from all of them. Stick with one brand.

Lastly to your question about getting 2 new 4s LiPo's, yes, I definitely recommend that for speed runs. Any time you draw large amounts of current for long periods of time (talking electrical time... anything not measured in milliseconds is a long time) you should not cut corners. Pay attention to ratings and buy the same brand. Don't cut corners when you are pushing limits which speed runs do.

There are those who really like to push limits and take things to the bleeding edge. The good ones are the ones who know their science and engineering. Get to know these folks, there are some great folks on this forum . I speak from industrial electrical experience with some RC experience. There are guys on here who really know the ins and outs of RC scale electrical which is basically the same but with differences due to scale.

 

[MFM]

Its not the brand, its the voltage. 6s runs at 22.2V and 2s at 7.4V. You should never run batteries in parallel with that much of a voltage gap. In theory they should work but in reality it doesn't work that way. If memory serves me, when connected in parallel the lower voltage battery will heat up and fail (usually resulting in a fire). In series, I still believe the 2s will fail but not 100% on that.

Folks tend to use the same manufacturer because they are putting faith in the manufacturer's ability to produce consistent batteries. Mixing manufacturers puts to the possibility of inefficiencies but not necessarily dangers (unless one battery is poorly designed). Again, in theory a 6s 5000mAh 100C battery is the same no matter who makes it. In reality, there are different ways to make a battery and always corners that can be cut. Sometimes these "differences" don't play nice with each other. With that in mind, sticking with the same manufacturer that you trust is always a good policy but not necessary a requirement. Sort of like tires, you don't put 4 different brands of tires on your car expecting to get the benefits from all of them. Stick with one brand.

Lastly to your question about getting 2 new 4s LiPo's, yes, I definitely recommend that for speed runs. Any time you draw large amounts of current for long periods of time (talking electrical time... anything not measured in milliseconds is a long time) you should not cut corners. Pay attention to ratings and buy the same brand. Don't cut corners when you are pushing limits which speed runs do.

There are those who really like to push limits and take things to the bleeding edge. The good ones are the ones who know their science and engineering. Get to know these folks, there are some great folks on this forum . I speak from industrial electrical experience with some RC experience. There are guys on here who really know the ins and outs of RC scale electrical which is basically the same but with differences due to scale.

Thank you so much for the education. I’m good at building them. Finding the sweet spot between power and weight and temps.
I WILL have the worlds fastest 6s Mojave any day now but may want to venture into multiple lipo to ensure getting max performance out of it. Like I mentioned, it’s only short bursts not for bashing. When I back, I gear down a little and go balls out. Speed runs much more delicate.

 

[Acidsnow]

Challenge accepted! Mine won't be ready any time soon mind!

Thank you so much for the education. I’m good at building them. Finding the sweet spot between power and weight and temps.
I WILL have the worlds fastest 6s Mojave any day now but may want to venture into multiple lipo to ensure getting max performance out of it.

 

[MFM]

Challenge accepted! Mine won't be ready any time soon mind!


View attachment 121337

That’s sick! Plz tell me how u got the bumper that low! That ain’t no Mojave on the left?! Lol.
may the fastest win! I’m ready to rollout. Just waiting for the northeast weather to give me a break so I can go record WR speed!

 

[Performance nut]

(1) Mad Max Beyond Thunderdome (1985) - Two Men Enter, One Man Leaves Scene (4/9) | Movieclips - YouTube

 

[MFM]

Hahahaha. Come on, pop the top. Show and tell!

 

[Acidsnow]

Lol No worries MFM, for now tho, there is literally nothing to see! It wooden go far! Just working out if it's possible. It is! While you're ready to rollout, Ah'm no even ready tae roll! Just keeping myself amused while unemployed. Can't justify buying too much stuff just now having just finished another build that got spendy! Good luck with the record tho, for now!

The bumper is mounted that low with masking tape! I have figured how it'll mount tho, fabricate a lower version of the stock one from a piece of kydex. Just wish ah'd lifted more from work! Or made less mudguards!

Just short of diffs and unsure what towers and shocks to use. Mocked up at mojave arm width, fronts good but the backs a bit neat. Need to figure out suspension travel for the 6s road cars and possibly the typhon.

Work in progress tho, apologies for derailing yer thread!

 

[MFM]

Awesome. That’s pretty cool!! Thanks for the idea for the front bumper!

 

[MFM]

Following this build!!

 

[Acidsnow]

Cheers MFM, d'ye have a build thread on the go for yours? Mines a tarmac basher, having a full mojave for spares just sat there seemed a waste! Wonder what the least amount of parts that justifies a new build is tho!

 

[MFM]

Cheers! Here’s the build thread for the castle install. https://www.arrmaforum.com/threads/mo-powa-baby-1100kv-build.29984/

I guess having any parts better than stock that serve purpose other than looks would be considered “built”. At least I see it that way.

 

[Acidsnow]

poop the bed! Some machine, that's definitely a build!

 

[olds97_lss]

FYI, c-rating with different capacities isn't the same current output. In case you wanted to try and run a 4000mah 3S 50C with a 5000mah 3S 50C to get 6S.

A 4000mah 50C pack is capable of 200A output.
A 5000mah 50C pack is capable of 250A output.

So even though both are 50C, the 4000mah pack is going to work harder than the other one to deliver the power, and of course, will also go dead faster just due to the fact that it's smaller capacity, which may not work well with an LVC cutoff circuit.

 

[MFM]

All my packs are 100c. Most 5000 but have a 6000, 6500, 7200.
Think I’m gonna get gens 4s 6000 100c packs for 8s 100c 6000.
and 4s 6000 100c in parallel
For 4s 12000 100c w the same brand new packs.
does that make sense? I’m a little nervous since I seen all these castle xlx2 burning up... kinda why I stayed 6s...
might just do it all on a beefy 6s pack...

 

[jkflow]

You have to type gens in it's full name just for the fun factor.

4S 12Ah really makes no sense imho, unless you want to run for an hour straight, but yes it's feasible.
Note: there is no such thing as a 100C pack but yes I own a few myself but it's pure marketing magic and not actual. They are all in the true 30-40 range on a good day.

As long as you stay within the same manufacturer you minimize your potential problems as you can be certain that the individual cells come from the same lot or process.

Parallel must always have the same voltage or something will blow up (with Lipos, it will be spectacular). Capacity is not that important here but should be within reason (not a 60000mAh in parallel with a 200mAh).

In series, they must have the same capacity (mAh) and the same C rating). Being off means that one pack will overheat due to different dynamics during discharge. It will result in different cell resistance values and it all goes downhill quickly due to heat. Nothing dramatic but cells will degrade in performance across 2-3 runs.