Jump to content
mud4fun

Battery weight/Performance tests

Recommended Posts

Folks, member @Snakehands on a recent thread about a relative novice using a basic Grasshopper buggy (that would also be used by his kids) and who specifically said he was not that interested in performance,  suggested that to improve performance the OP should fit a 1500mah soft skin LiPo (helo/aircraft) battery and an adaptor to fit his Tamiya buggy.

I (and a few others) disagreed and suggested the OP buy the highest capacity battery they could afford to give long run times which would in our view increase enjoyment of the buggy. The weight being largely irrelevant as the OP was not bothered by performance.

Snakehands insisted that using the super lightweight packs gave considerable performance boosts to these vintage buggies and that swapping batteries every 5 minutes was perfectly acceptable for the increased 'performance'.

I insisted that I would never recommend the smallest capacity packs or soft skin packs to novices using buggies. I would opt for the largest capacity I could afford and instead improve performance by setup changes, better tyres, different shocks, different motors, gearing or shedding weight by using lighter receivers and ESC's etc. I also did query snakehands theory because we actually had to add front biased weight to our buggies to gain performance in postal racing on wet grass.

After a rather public spat with Snakehands (sadly I have a large character flaw in not suffering fools lightly) I did start to wonder if he did indeed have a valid point?

So I ordered a new Turnigy 1000mah LiPo (and the adaptor as recommended by Snakehands)

I intend to test this against all the other batteries that the Mud family use in our vintage buggies. Snakehands was concerned that I was using a high performance race buggy which would affect results. Although, as I said to him, if weight really was such an important factor then it would surely give improved results regardless of the chassis. He conceded and suggested my race spec Cougar would improve my round 7 postal racing average lap time from 6.4 seconds to 6.2 seconds by ditching my 7.6v 120C 4400 shorty and using a 7.4v 35C 1500mah soft skin helo battery instead. To me this sounded a bit odd, so I'd sacrifice 20-30 mins run time, equivalent to four 5min races to gain 0.2 seconds per lap on a single 5 minute race before having to change battery? and that is if it even lasted for full race distance!

So I have prepared a plan to test out Snakehands theory. I will use my Thundershot, which is a vintage buggy which I think even Snakehands will concede is not a modern race spec buggy. My thundershot has squared off battery tunnel so can run any battery we have so is ideal for this test. I will test a whole range of batteries ranging from 65g aircraft soft skin LiPo to hugely heavy 9.6v NiCd. 

I plan to do the following tests on each battery:

  • 1) Run postal racing round 7 track on wet/muddy grass for 3 x 5 minute races on each battery and take the best result for each type
  • 2) Run postal racing round 7 track on tarmac for 3 x 5 minute races on each battery and take best result for each type
  • 3) Do a 3 x 300 foot long drag races with each battery type and take the best result from each battery. (GPS max speed)

I intend to use a SkyRc GPS unit to do to drag race tests and a LapMonitor, transponder and tablet for the round 7 track races.

I will capture and record: (best of 3)

  • Fastest lap time
  • Most laps per 5min race
  • Total runtime
  • Run time per 1000mah
  • Laps per 1000mah
  • Max speed

The packs have the following weights:

  • Turnigy soft skin 7.4v LiPo - 65g
  • Absima 4000mah 7.4v LiPo - 190g
  • Absima 4400mah 7.6v HV LiPo - 196g
  • Absima 5000mah 7.4v LiPo - 222g
  • Absima 3600mah 7.2v NiMh - 353g
  • Sanyo 2000mah 8.4v NiCd - 411g
  • Sanyo 2000mah 9.6v NiCd - 467g

battery_tests.thumb.jpg.1a402bf04a5d563d4d6da435a7540c4f.jpg

 

Is this fair do you think? can anybody suggest any more tests that could show performance differences between the packs?

I will start the tests this weekend but because of lockdown I will not be able to do the GPS speed tests or tarmac races until after lockdown ends.

 

  • Like 1

Share this post


Link to post
Share on other sites

I was also considering doing all the tests on four different motors:

  • a brand new stock silver can
  • a brand new sport turned silver can
  • a Reedy 19T spec
  • a 13T Dyna Run SuperTouring

would anybody be interested in that?

I will also include the number of laps per 1000mah to give an indication of relative performance for capacity.

Share this post


Link to post
Share on other sites

Sounds like a very interesting set of tests though I still prefer to get a bigger capacity battery if possible. I just hope that user accepts your results for better or worse, some people may not be able to see science and facts for what they are. I say do the tests but don't get too hung up on trying to convince him/her if your first round of tests don't get accepted by them. They aren't the ones open to trying the tests on their own so let them do a second round to try and disprove your results if they contest it. If they contest it then maybe consider their successful test and replicate it if you are willing to go down that rabbit hole even more.

  • Thanks 1

Share this post


Link to post
Share on other sites

Thanks @nel33, don't worry, the tests are actually for my benefit (and may prove useful to others too). 

At the time Snakehands suggested I'd see a 0.2 second per lap gain, the round 7 postal racing results had not been published. As it happens, a 0.2 second per lap gain would have given me 1-2 additional laps over the 5 minute race which would have meant a win instead of third place!!!

so I am 100% interested in the results and am very open to see if it works out.

while I would still recommend the higher capacity to the novice, I may be willing to live with a short run time for a postal race if it gave me a measurable improvement in performance. :)

 

  • Like 1

Share this post


Link to post
Share on other sites
2 minutes ago, mud4fun said:

Thanks @nel33, don't worry, the tests are actually for my benefit (and may prove useful to others too). 

At the time Snakehands suggested I'd see a 0.2 second per lap gain, the round 7 postal racing results had not been published. As it happens, a 0.2 second per lap gain would have given me 1-2 additional laps over the 5 minute race which would have meant a win instead of third place!!!

so I am 100% interested in the results and am very open to see if it works out.

while I would still recommend the higher capacity to the novice, I may be willing to live with a short run time for a postal race if it gave me a measurable improvement in performance. :)

 

heck even i try out some things that i think may improve something sometimes. i see nothing wrong with satisfying personal curiosity and if it gets faster times at the cost of run time then all the better for the racing results. my current battery capacity is 5000 NIMH as thats how high my first charger can handle, im not really interested in Lipo at the moment and the extra maintenance with them. i wouldn't choose anything under 2600MAH if i had the choice for a higher capacity simply for run time.

  • Thanks 1

Share this post


Link to post
Share on other sites

Could be interesting results!

Just to throw in a curve ball,  I use a 3200mah 110C shorty, with a 35g under Lipo weight, seemingly a Low Centre of Gravity helps.

Can't imagine you, having a spat....🙄😂

  • Thanks 1

Share this post


Link to post
Share on other sites

Was hoping to start the tests this weekend, then I saw the weather forecast.....

Seems I may need to test snow tracks instead....:lol:

Share this post


Link to post
Share on other sites

IF you go through with this, I throroughly commend your patience and dedication; and await the results.

I dont currently run LiPO for any cars, still running NiMh for everything; anywhere from 2400mAH to 5000mAH depending if im just trying to kill time or test a new build/upgrade - or is usually the case - whatever is charged, haha.

I do find on the re-re's (all running sports tuned cans) 4000+mAH is the sweet spot; it gives a good burst of performance early on (as always bumpier surfaces or thicker grass will drain them quicker), but still gives me the run time to enjoy some more technical stuff without fear of too much power causing me to crash out and do damage - oh my poor HotShot.

My XV-01 and F104w are still both running stock silver cans, so on these any strength battery in my collection gives me a good run.

Though as stated in the past, im not looking to eek every ounce of performance out of a car i can, but your results may sway me - at least on the battery front.

  • Thanks 1

Share this post


Link to post
Share on other sites
5 hours ago, nel33 said:

I just hope that user accepts your results for better or worse, some people may not be able to see science and facts for what they are.

It's not right to blindly accept results of a test because 'science' - the test may be flawed and not take certain things into consideration. This kind of thing can have serious consequences in the 'real' world regarding scientific research (like loss of funding for something that would be beneficial).

I'm not suggesting @mud4fun's test is flawed, but perhaps it is naive to suggest that simply lowering the mass of the battery (and make no other compensatory changes) will have the best outcome on performance. 

As the OP stated himself, he once had to add mass to the front to improve grip, so removing mass will reduce grip. 

Conversely, removing mass improves acceleration, under the assumption that the motor's torque is the same with both batteries, but since torque is proportional to current, which is proportional to voltage, and since voltage drops faster in batteries with lower capacity, this may not be the case over a full 5-minute race. 

Also, depending on the track layout and surface quality, improved acceleration may outweigh loss of grip, or vice-versa.

Regarding mass, depending on how the battery's mass is positioned in the thundershot, simply reducing it may not be optimal, and at least some mass may need re-adding to recover lost downforce over a particular set of wheels.

Removing mass from the battery also gives you the chance to re-add it at a lower level, reducing the car's centre of mass and therefore improving handling characteristics.

So while simply replacing the battery with a lighter one may tell you if that change in isolation gives you a performance boost on your particular track layout/surface chosen for the test, it may not be the general solution to the question: 'will a lower capacity battery improve my lap times?'. 

  • Like 2

Share this post


Link to post
Share on other sites

Looking forward to the results on this. I would not be surprised if a test with a heavy battery gives a better time. Let me explain:

A couple of times a year I spend a few days at my BIL home  where we race 1/10 speedway cars. We have a mish mash of setups with NIMH/brushed, LIPO/brushed and LIPO/brushless. I was always of the opinion that the lipo cars would always be quicker due to the batteries being half the weight (5000mah NIMH and 4200 mah lipo). Once we got a computer timing system in, we quickly worked out the playing field was pretty much level even though some cars had a much higher top speed. 

The "track" is an oval shaped driveway most days of the year and it is not a super smooth surface. We found that some of the cars with NIMH batteries handled better around the corners and were less likely to spin out on acceleration as they had no where near the punch of the lipo cars. The lipo/brushless were fast, but harder to handle.

One thing that massively changed my thinking about how to set up a car was running a GoPro on a car with the telemetry turned on. We could see the G forces on turning and top speeds etc etc. We weren't topping more than 50kph on the straights, so there was no point running a 4000kV motor, when a 3000-3300 was plenty for the top end with the benefit of it being easier to manage.

When we did 2 race nights in January. The A-Main winners were a brushless/lipo on night 1 and a brushed/nimh on night 2.

 

So my suggestion to you is if you can get a hold of a GoPro (or similar), put in on the car and see if it can provide more data.

  • Thanks 1

Share this post


Link to post
Share on other sites

I've found that on most cars, using a lighter battery than what the car was designed for will do screwy things with the weight balance and mess up handling.

Case in point:  an M04 I helped set up at the track. That thing had the battery ALLLLL the way to the back, to provide weight for the rear wheels. With a NiMH in there (what it was designed to do) it ran okay-ish, but was nearly undrivable with a Lipo in there. I added in a bunch of lead weight in a hollow section of the rear, and it would improve dramatically.

  • Thanks 1

Share this post


Link to post
Share on other sites

Yes absolutely agree @rich_f and @GooneyBird 

my tests may well be flawed and far from perfect however they should give some indication of relative differences. As you say, if it looks like performance will increase significantly it may then be worth following that up with modifications to better make use of that, even if it is just adding more weight more evenly distributed to gain better balance or lower CoG.

And yes your points illustrate why I myself disagreed with the other member. Context should be taken into account. If you know that a relative novice/newbie to the hobby is asking for advice where it is clear that person may have limited desire, ability or funding to modify the car to suit a significantly different weight of battery then you should add some caveats. IMHO simply saying that reducing weight improves performance in a blanket statement without caveats is misleading and in some cases may be untrue. My first thought is that should a person follow that advice and find they then need to pay out for different springs, damper oils or parts to retain the smaller battery etc it will incur costs and issues that they were not expecting. 

As you mentioned, we found that both our 2WD cars needed weight adding or distributing more to the front to gain performance on a wet muddy surface for that particular round of postal racing.

Also dropping the weight of a pack by a significant amount, say 150g could play havoc with the cars handling. Especially if Tamiya designed the car to use a heavy NiMh and fitted stiffer springs and different shock geometry to compensate for it. Fitting the lighter pack on its own without any other changes would lead to a bouncy car that would be  poorer performing over rough ground? (Conversely, as in the case of my daughter's new DT03, the rear end was saggy with a NiMh so maybe Tamiya designed it for a LiPo LOL)

And yes @GooneyBird we had same with our Avante2001\Egress. The car was originally designed for a heavy NiCd which sits on one half of the chassis to compensate for the heavy motor and steering servo on the other side. After switching to LiPo the car was a nightmare, would not jump flat, constantly landed on its front left wheel and broke the hub numerous times, would have odd handling so cornered better one way than the other. It was solved eventually by using a heavier square section high capacity LiPo and putting the ESC receiver etc as far over the battery side as I could, along with the transponder.

I will do the tests though because I have never directly compared so many different batteries in the same car so I am genuinely curious as to the results.

I'm personally predicting the 7.6v 110C 4400mah shorty to deliver the best lap times and the 9.6v NiCd to give the best top speed over the long drag strip. This is based on previous experience with those in numerous buggies. 

 

Share this post


Link to post
Share on other sites

Go science!

Enough talk of how to science, let talk about the science:  the grasshopper in question, ie will a smaller capacity battery produce better results?

A couple things to think about:

1. Results in one car may not produce equal results in another.  Everyone has noted factors to consider here - position, type of car, 2wd/4wd, etc.  Not to be critical, Mud’s experiment is flawed in this respect, ie his results are only pertinent to the car he tests, and does not actually resolve the original question.

2. The GH has a max battery size.  As it turns out, I have a GH.  The 5000mah NiMH Onyx brand battery I have will not fit without employing a hammer.  The 3000s barely fits lengthwise, but will fit. I haven’t tried my 5000 shorty LiPos yet.

3. What constitutes “better” results?  This is a purely subjective question, so several things should be taken from the data so we can better understand the differences.  Is longer run time vs faster speeds more desirable???  Is the difference in performance worth the time to change or not change out the battery???

That said, I’m willing to send my GH to Mud so he can do it right...

Go science!

Terry

 

  • Haha 1

Share this post


Link to post
Share on other sites

@Frog Jumper Thanks Terry. We do have a DT02 to test with too but the reason I avoided that was because it hardly fits any batteries in! None of our hard case LiPo fit other than the shorty and it won't fit the 7 or 8 cell NiCd's either. The Thundershot will fit all of them so I thought it would be best to use that. At least it would remove one variable as the car would be the same for all tests. The ESC, RX, Servo etc would also be the same as well as the driver and the track. So quite a few variables negated or minimised? :)

You're right though. Both the Cougar and DT02 had different track performance depending on where the shorty was fitted (fore or aft). In our case we found the forward position gave better results for the last round as it gave us less understeer under power.

All this is largely irrelevant though, in reality swapping from one tyre pattern/compound to a different pattern/compound gave us as many as 10 laps more in one 5 min race!!! At the end of the day it is the four tiny patches of rubber on the ground that can dictate how much power you can get down and how well you can corner. No point in having a blisteringly quick accelerating car or with a high top speed if it ploughs right on at the first corner.....:D

  • Like 1

Share this post


Link to post
Share on other sites
17 hours ago, rich_f said:

It's not right to blindly accept results of a test because 'science' - the test may be flawed and not take certain things into consideration. This kind of thing can have serious consequences in the 'real' world regarding scientific research (like loss of funding for something that would be beneficial).

I'm not suggesting @mud4fun's test is flawed, but perhaps it is naive to suggest that simply lowering the mass of the battery (and make no other compensatory changes) will have the best outcome on performance. 

As the OP stated himself, he once had to add mass to the front to improve grip, so removing mass will reduce grip. 

Conversely, removing mass improves acceleration, under the assumption that the motor's torque is the same with both batteries, but since torque is proportional to current, which is proportional to voltage, and since voltage drops faster in batteries with lower capacity, this may not be the case over a full 5-minute race. 

Also, depending on the track layout and surface quality, improved acceleration may outweigh loss of grip, or vice-versa.

Regarding mass, depending on how the battery's mass is positioned in the thundershot, simply reducing it may not be optimal, and at least some mass may need re-adding to recover lost downforce over a particular set of wheels.

Removing mass from the battery also gives you the chance to re-add it at a lower level, reducing the car's centre of mass and therefore improving handling characteristics.

So while simply replacing the battery with a lighter one may tell you if that change in isolation gives you a performance boost on your particular track layout/surface chosen for the test, it may not be the general solution to the question: 'will a lower capacity battery improve my lap times?'. 

Mud4fun isn't mythbusters, it's not possible to do all the tests just to satisfy one user's idea to cut down time. More mass to add weight that can translate to speed. It comes down to snakehands claiming something because they have the idea that less weight equals speed. Mud4fun is just doing some tests to prove or disprove that idea out of personal curiosity. Let's just see what results he gets and if snakeheans idea that lower weight doesn't pan out. It will then be in snakehands court to contest the results of this battery of tests (pun intended).

i dont know snakehands has any data held back to prove that statement or is unwilling to test a larger battery size but mud4fun is willing to test it out. one of these 2 have a more open ended view of the statement  so let the data tell the story and then see whish sort of battery performs the best.

Share this post


Link to post
Share on other sites

The basic grasshopper has a 380 motor? 

That'll neutralise any higher C rated battery advantage, as they'll just not demand the amps, (why some people who swap over to Lipo, don't see the massive performance jump than others....🙄) and would also make the biggest difference shedding weight? 

Share this post


Link to post
Share on other sites
9 minutes ago, Wooders28 said:

The basic grasshopper has a 380 motor? 

That'll neutralise any higher C rated battery advantage, as they'll just not demand the amps, (why some people who swap over to Lipo, don't see the massive performance jump than others....🙄) and would also make the biggest difference shedding weight? 

True @Wooders28 but Snakehands suggested that we would all see performance gains from running a 1500mah helo soft skin pack, regardless of buggy or motor. I even pushed that point and explained I ran a 7.6v 4400 110C shorty with a 38K rpm brushed motor but he insisted the 7.4v 1500 would give better performance? I'm not convinced but remain open minded. First set of results (wet grass track) should be done tomorrow tonight :)

  • Like 1

Share this post


Link to post
Share on other sites
22 minutes ago, mud4fun said:

Snakehands suggested that we would all see performance gains from running a 1500mah helo soft skin pack, regardless of buggy or motor

Naa,  wouldn't agree with that. Running a 6.5t motor in my old RB5, I noticed a lap time difference just going to a better esc (the 6.5t was at the esc max limit , may be a bit over ), and then again going from a 65c to a 120c, just loads more punch out of the corners.

380 powered Grasshopper , I'd agree, it needs every bit of help it can get, but the more powerful the motor, the less of an effect a little extra weight has and can sometimes help, if in the right place (like adding an under Lipo weight, works a bit like a keel on a boat) 

  • Like 1

Share this post


Link to post
Share on other sites

@mud4fun is it worthwhile noting the discharge rate of the batteries? Regardless of battery chemistry, surely the discharge rate will have an influence on the acceleration, but will it translate to faster lap times?

For the speedway cars with lipo batteries, almost all of them have lead weights on the front to try and counter the wheel lift and help with turn in.

 

 

Edited by LeftyAl
typo
  • Thanks 1

Share this post


Link to post
Share on other sites

Thanks @LeftyAl I will look into that. 

And yes, we added 90g of lead sheet wrapped around bumper on a DT02 to reduce understeer under power on wet muddy grass in the last round of postal racing, also to counter it's tendancy to wheelie whenever you touched the throttle! :D. I also moved battery forward and added weight to front end of my Cougar for same reason.

  • Like 1

Share this post


Link to post
Share on other sites
9 minutes ago, LeftyAl said:

@mud4fun is it worthwhile noting the discharge rate of the batteries? Regardless of battery chemistry, surely the discharge rate will have an influence on the acceleration, but will it translate to faster lap times?

For the speedway cars with lipo batteries, almost all of them have lead weights on the front to try and counter the wheel lift and help with turn in.

 

 

That's a good point, and something I have been wondering about for NiMHs in particular. Different brands advertise different discharge rates, but most of them match the mAh of the battery (i.e. 4200mAh battery is shown having a 42C discharge rate) which I can't believe is accurate. The few that don't are vastly under that--like 15C for a 3800mAh battery--so I'm not sure which value they're giving, whether it's a "peak" value or something like a "nominal" or "steady" discharge rate, or if it's a difference in measurement or something.

Share this post


Link to post
Share on other sites

The 1000mah helo pack has a constant rate of 35C, burst at 75C. My 4400mah 7.6v shorty has a claimed constant of 110C? Who knows, short of hooking them up to a test meter. Proof will be in pudding. My Thundershot is running a 13T Dyna Run Super Touring with a suggested draw of 35-45 amps (depending on the source of the info). 

I was thinking of using my Novak Super Rooster ESC which is 200amp rated so will be more than capable of handling any of the test packs. 

 

Share this post


Link to post
Share on other sites
On 2/5/2021 at 11:06 PM, mud4fun said:

The 1000mah helo pack has a constant rate of 35C, burst at 75C. My 4400mah 7.6v shorty has a claimed constant of 110C? Who knows, short of hooking them up to a test meter. Proof will be in pudding. My Thundershot is running a 13T Dyna Run Super Touring with a suggested draw of 35-45 amps (depending on the source of the info). 

I was thinking of using my Novak Super Rooster ESC which is 200amp rated so will be more than capable of handling any of the test packs. 

 

...and then he went all quite. Results not to his liking? He originally badgered me into giving a figure for how much faster a lightweight car might be. I gave him a figure in the end just to shut him put. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...