Blinky racing battery help
 

Hi all. Been racing for many years with buggies and have tons of experience but I am struggling to understand an issue with blinky racing. We are thinking of running a buggy class with 13.5 blinky and some of the drivers have said with today's low profile lipos they would dump in the race. The batteries are ok with a 7.5 with boost but a 13.5 blinky would take up too much power and the battery would dump. Can anybody explain too me how a 7.5 with boost used less power than a 13.5 blinky. Many thanks.

13.5 would use less power by far, afraid they are talking out there butts, you would not dump.

It wouldn't.

Even Trish from Schumacher said on his you tube video that he used a full thickness shorty lipo to win the stock class at Eos daun because of this. I just don't see how it uses more power.

I think they are using the wrong terminology. I’ve read that with touring cars for example you would suffer because the voltage drops a bit (so does not ‘dump’ like the old days) and that loss of performance means you can’t win etc This is because you don’t have an excess of motor power, like in a mod class, so need every scrap of performance you can eek out of the vehicle. Hence why you might need full size Lipo to keep higher voltage.

That's exactly it, because you're on full throttle a lot more and even then acceleration isn't stunning you notice the drop. Also they tend to be geared high, which draws a few extra amps, exaggerating the issue of acceleration when a little down on voltage.

A racer at our club was using a 13.5 in a cougar laydown with a 23 pinion and kit spur running a little boost. He dumped after 4 and a half mins with a low profile 3200 lipo. I don't see how as I run lipos that are 3200 with a 10.5 with boost and it's fine.

Hi,


You'd need to check if he had fully charged the lipo.



Also was it a one off. Bad pack / uncharged pack.


Did he try a larger capacity lipo eg 5000mah.
If he did what did he take out of it in a run?


Are you sure he dumped the pack and not thermaled the motor?


A lower capacity lipo should not have the same puch as a larger lipo.
(C-rating / max amps the lipo can provide.)


But a 3200 should have more than enough for a 5 minute run.



MiCk B. :-)

I'll find out.

Malkin is massively under geared ;)

oh the joys of blinky racing, battery and motor wars!

Less applicable in offroad IMO

I ran 13.5T stock Blinky last night at MB raceway on EOS carpet.

I used my Intellect 4200mAh, a new 4400mAh, and 5000mAh packs, 4200 in practice, and 4400 and 5000 in Qual and Finals. I normally use 4200 and the new 4400 in mod racing, 5000 in my 4wd.

I didn't feel a difference between the 4400 and 5000 in speed, punch or have any fade at the end. They each took about 1665-1700mAh in recharge after the runs, so used about the same for the run. I was playing with gearing. I didn't race with the 4200 as they are a bit older than the 4400. I'll back to back the 4400 and 4200 at some point to see if i can feel the difference. All my packs are less than 1 year old at most. I replace mine every year.

I think I preferred the 5000mAh as I made less mistakes with this. I rolled the car landing a few jumps with the 4400, and didn't with the 5000. I think the added weight helped settle the car, so I went faster overall in the 5 min run due to less mistakes, but the added weight didn't slow the car down.

I normally take more out of each pack in Mod (6.5T) on same track. Blinky certainly used less in a 5min run than running mod.

That's a very insightful evaluation. I am going to pass this on to my mate who had the dumping issue in response to the argument that a 3200 mah low profile lipo cannot sustain a 13.5t motor in blinky for a 5 min run. Thanks

Cheers.

To comment on your racing buddy's situation with 3200mAh packs, I'd suggest the packs may just be experiencing a voltage drop under load. This may be triggering the low voltage cut off on the speedo, and so if looks like the packs dumped. Has he disabled low voltage cut off on the sppedo? If not, do this.

At this point we don't know the age or condition or numbers of charge/discharge cycles of those packs. I suspect they aren't new.

If you assume 1665-1700mAh (that I was pulling in 5 mins) from a 3200 pack, you are using over half the capacity. If those packs were LiHV (and not Lipo), then they wont be charged to 3200mAh anyway, so indeed he would be puling far more more than half of the capacity out of the pack. A pack under load will experience voltage drop.

I think the current draw (and therefore voltage drop) profile from a modified motor will be significantly different to that of a stock motor. Mod will likely be lots more spikes as you are on and off the throttle more, whereas stock will be more constant. Modified motors will potentially draw higher current for less time, with stock motors pulling a more constant load. The output capability of the pack will therefore be felt more in stock racing, where as its may not be as noticeable in mod.

Take home message is: buy a new battery... :thumbsup:

Why would that be?

For the HV 7.6v packs, the mah rating will be if the pack is charged to capacity.
But as for racing we can't charge to the maximum voltage the pack will go to, only to the maximum voltage allowed for racing then the pack will not have the full capacity in it.
Hopefully that makes sense.

What's it like running the 13.5t blinky Neal? Is it good fun and do you have a few of you running them?

I have just bought a 17.5t to try out for a bit of fun!

Nope lol. What's the maximum allowed for racing? How is that checked?

In the BRCA rules it states lipos cannot be charged over 4.2v per cell i.e. 8.4v for a 2s. This is a hard and fast rule. If caught charging over this you could be removed from club/meeting etc.


At BRCA sanctioned events voltage is measured before each run.