Factory Drivers and NiMh
08-14-2008, 07:14 PM
#61
Tech Adept
[QUOTE=xrayeddy;4738300]Sort of answers the question I"m going to ask, but is there a voltage regulator that could handle the amperage from a 2s lipo pack so the 1/12 guys could run a lipo pack yet only put out 4.8v ?
[QUOTE]
You know what? this is a very good idea. I remember an old Tekin charger had in the instructions to add a resistor (think basic voltage regulator) in line while charging 4 cell packs in order to reduce the voltage.
Definately could use some further research. Adding an approved, sealed regulator inline could be the ticket to ease of comatability, and you could still used your 2s lipo in your TC and 12th. It's not like capacity would be an issue due to energy usage by such a regulator, since capacity is OTT for 12th anyway.
Well done that man!
[QUOTE]
You know what? this is a very good idea. I remember an old Tekin charger had in the instructions to add a resistor (think basic voltage regulator) in line while charging 4 cell packs in order to reduce the voltage.
Definately could use some further research. Adding an approved, sealed regulator inline could be the ticket to ease of comatability, and you could still used your 2s lipo in your TC and 12th. It's not like capacity would be an issue due to energy usage by such a regulator, since capacity is OTT for 12th anyway.
Well done that man!
08-15-2008, 04:57 AM
#63
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I think before we rush into any situations with regulators or things of that nature we should give the manufacturers a chance.If I understand li-po construction correctly the voltage is dependent upon how many layers of material are laminated during construction, so if you decrease the layers you should decrease the voltage. Now we just have to prove that it would be profitable for the cell manufacturers to produce a lower 1s cell, say in the 2.5v range. making a 2s lipo cary an average voltage of around 5v.Any other thoughts on voltage for a 2s = 4 cell lipo?? I know peak voltage on a subc pack is in the 5.2 range so using that as aa starting point I think 5v would be a good place to start a 4 cell equivalent lipo.
08-15-2008, 08:31 AM
#64
Eh, not that simple. It would only be useful for RC at this point. Existing chargers wouldn't be able to function. Much like if there were a .8 volt Nimh battery. It just would throw off the electronics completely.
I'm keeping my eyes open for some sort of Lipo 1/12th battery though. then I wouldn't need my nimh's anymore.
Paul
I'm keeping my eyes open for some sort of Lipo 1/12th battery though. then I wouldn't need my nimh's anymore.
Paul
08-15-2008, 12:22 PM
#67
A123 has a device that increases the voltage output from their packs, not decrease.
Danny- I think the 1s lipos are the way to go. I'm sure they put out a little more voltage than 3.7 and with the lighter weight, probably are just about even with a nimh equipped car. Also, nice job on the proto 1s lipo.
Danny- I think the 1s lipos are the way to go. I'm sure they put out a little more voltage than 3.7 and with the lighter weight, probably are just about even with a nimh equipped car. Also, nice job on the proto 1s lipo.
08-15-2008, 12:35 PM
#68
Tech Fanatic
Sort of answers the question I"m going to ask, but is there a voltage regulator that could handle the amperage from a 2s lipo pack so the 1/12 guys could run a lipo pack yet only put out 4.8v ?
Or, as you mention , a 1s lipo pack with say a 17.5 bl motor in a class of nimh/21.5 cars , 1s/13.5 with nimh/17.5 , and so on .
Or, as you mention , a 1s lipo pack with say a 17.5 bl motor in a class of nimh/21.5 cars , 1s/13.5 with nimh/17.5 , and so on .
BMI will be selling a LiPo 'tray' to go with a 7.4v saddle configuration (one sat atop the other) on their 200mm World GT BMI DB10R that brings the weight back to a pack of NiMh cells - this works.
I've switched to EnerG cells, and they are terrific. Behave just the same way that cells used to - no storage problems, no dead cells, give good performance for many runs and keep their match. That's why it's good to know SMC are still in that market.
08-16-2008, 09:54 PM
#69
Ok, time for an update, I promised I'd do a test & I just got back from it a couple of hours ago(but had to watch the Olympics first, 
), & it did produce some interesting data. As I said, I have the Novak Sentry, which I've added the current sensor to, & I did a back to back test, with my car(a Tamiya TRF416) setup exactly the same, & I used the same motor(my Novak 13.5 Pro), same gearing, same tires, & even prepped them EXACTLY the same each time. And I also ran enough times to make sure I drove consistently, so there wouldn't be too many anomalies in the readings(since a hard impact can create a bit spike in amp draw & affect the batteries' voltage), & I got two good runs back to back, first with a pack of Ener-G 4600's( a decent one by Team Hurricane, average voltage of 1.233 per cell on the label & it's run strong in racing) & the second with my SMC 5000 hardcase pack that I bought back in April & have run a LOT since then( at least 3 or 4 runs on it per race or practice day). And I did notice that the NiMh's beginning voltage was higher than the LiPo(8.687V for the NiMh & 8.403V to start for the LiPo), but through the run & with a race load on it, the NiMh dropped off a bit more at each pull of the throttle. For example, at about the 1 minute mark, the NiMh would drop to about 7.554V at full throttle when amp draw is highest, at 37.05 amps & then go back up to 8.046V once the loads eases. But the LiPo, at the same 1 minute mark & full throttle only goes down to 7.837V(& the amp draw was 39.488 amps) & then recovers to 8.214V. And at the 5 minute mark, the NiMh drops to 7.27V at full throttle(amp draw at 31.2 A) & recovers to 7.742V, but the LiPo at the same point only drops to 7.459V(with a 34.125 amp max load) & recovers to 7.742V. So at that point, the resting voltage for both is the same, but the LiPo simply doesn't drop off at load as bad as the NiMh. And for the test's full runout, I just used close to the Sentry's max time setting(at least for being able to store 10 runs, at that setting it can test for 8 minutes & 23 seconds) & ran them both the full test length, for that, the NiMh's average voltage was 7.549 with an average amp draw of 17.692, & the LiPo showed an average of 7.75V for that time at an average draw of 16.37 amps. Bottom line, the NiMh shows more voltage at rest in the beginning, but as soon as the load is placed on them, the LiPo holds up better, & builds a bigger advantage the longer it runs. If the NiMh can have ANY edge, it's only in the first couple of laps of a run(if that), from then on, the LiPo is as good or better. And I have also done race runs with them back to back(before the indoor season ended), & the lap times bore that out, it was nearly impossible to tell any difference in lap time between the two, except that it seemed easier to do fast ones at the end of a run with the LiPo, but the best laps I did that night were within a tenth of a second(or less) between both. And of course, there's NO WAY I could run the NiMh as hard as I do the LiPo(namely, do all practice runs with it, then all 3 qualifiers & the main, just LITERALLY plugging it back into the charger as soon as I pull the car offtrack & get it out of the car), & the LiPo never seems to heat up at ALL(unlike the NiMh which gets pretty warm both on the charger & in the car, & it has to cool down for at least a couple of hours before it can be safely charged again). So any more doubt as to why LiPo's are getting so popular? 
), & it did produce some interesting data. As I said, I have the Novak Sentry, which I've added the current sensor to, & I did a back to back test, with my car(a Tamiya TRF416) setup exactly the same, & I used the same motor(my Novak 13.5 Pro), same gearing, same tires, & even prepped them EXACTLY the same each time. And I also ran enough times to make sure I drove consistently, so there wouldn't be too many anomalies in the readings(since a hard impact can create a bit spike in amp draw & affect the batteries' voltage), & I got two good runs back to back, first with a pack of Ener-G 4600's( a decent one by Team Hurricane, average voltage of 1.233 per cell on the label & it's run strong in racing) & the second with my SMC 5000 hardcase pack that I bought back in April & have run a LOT since then( at least 3 or 4 runs on it per race or practice day). And I did notice that the NiMh's beginning voltage was higher than the LiPo(8.687V for the NiMh & 8.403V to start for the LiPo), but through the run & with a race load on it, the NiMh dropped off a bit more at each pull of the throttle. For example, at about the 1 minute mark, the NiMh would drop to about 7.554V at full throttle when amp draw is highest, at 37.05 amps & then go back up to 8.046V once the loads eases. But the LiPo, at the same 1 minute mark & full throttle only goes down to 7.837V(& the amp draw was 39.488 amps) & then recovers to 8.214V. And at the 5 minute mark, the NiMh drops to 7.27V at full throttle(amp draw at 31.2 A) & recovers to 7.742V, but the LiPo at the same point only drops to 7.459V(with a 34.125 amp max load) & recovers to 7.742V. So at that point, the resting voltage for both is the same, but the LiPo simply doesn't drop off at load as bad as the NiMh. And for the test's full runout, I just used close to the Sentry's max time setting(at least for being able to store 10 runs, at that setting it can test for 8 minutes & 23 seconds) & ran them both the full test length, for that, the NiMh's average voltage was 7.549 with an average amp draw of 17.692, & the LiPo showed an average of 7.75V for that time at an average draw of 16.37 amps. Bottom line, the NiMh shows more voltage at rest in the beginning, but as soon as the load is placed on them, the LiPo holds up better, & builds a bigger advantage the longer it runs. If the NiMh can have ANY edge, it's only in the first couple of laps of a run(if that), from then on, the LiPo is as good or better. And I have also done race runs with them back to back(before the indoor season ended), & the lap times bore that out, it was nearly impossible to tell any difference in lap time between the two, except that it seemed easier to do fast ones at the end of a run with the LiPo, but the best laps I did that night were within a tenth of a second(or less) between both. And of course, there's NO WAY I could run the NiMh as hard as I do the LiPo(namely, do all practice runs with it, then all 3 qualifiers & the main, just LITERALLY plugging it back into the charger as soon as I pull the car offtrack & get it out of the car), & the LiPo never seems to heat up at ALL(unlike the NiMh which gets pretty warm both on the charger & in the car, & it has to cool down for at least a couple of hours before it can be safely charged again). So any more doubt as to why LiPo's are getting so popular?
08-17-2008, 01:20 AM
#70
Thanks for that info Grizzbob. It helped to back up what I was thinking.
I realized that lipo discharged under load without dropping in power as much as nimh through two things. One day, I decided to use some old nimhs and forgot to turn off the lipo cutoff on my GTB. The GTB was cutting off because it detected low voltage under load, but I was unsure about how much of the voltage drop was due to the cells simply being old. Secondly, I had to re-tune my cars significantly to handle increased wheel spin when I switched to lipo. I even switched to a different chassis because my old car wouldn't handle too well with the increased punch of lipo in comparison to nimh.
I realized that lipo discharged under load without dropping in power as much as nimh through two things. One day, I decided to use some old nimhs and forgot to turn off the lipo cutoff on my GTB. The GTB was cutting off because it detected low voltage under load, but I was unsure about how much of the voltage drop was due to the cells simply being old. Secondly, I had to re-tune my cars significantly to handle increased wheel spin when I switched to lipo. I even switched to a different chassis because my old car wouldn't handle too well with the increased punch of lipo in comparison to nimh.
08-17-2008, 09:00 AM
#71
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good stuff Grizzbob, maybe that info since it's so complete needs to be stickied somewhere somehow.
having been screwing around with lipos for about 2 years now your quanititative results have just proved out my own expereinces.
having been screwing around with lipos for about 2 years now your quanititative results have just proved out my own expereinces.
08-17-2008, 11:11 AM
#72
Grizzbob,
I'd be really curious to see the test on the LiPo run again with some heat in it. A starting temp around 120F or so. It seems universally accepted that heat further improves performance, and helps the LiPo hold more voltage under load (though doesn't seem to affect its resting voltage).
I'd be really curious to see the test on the LiPo run again with some heat in it. A starting temp around 120F or so. It seems universally accepted that heat further improves performance, and helps the LiPo hold more voltage under load (though doesn't seem to affect its resting voltage).
08-17-2008, 01:12 PM
#73
Interesting test results for the Nimh/Lipo comparison, but the answer to the initial question is quite simple. The reason you have not seen all the top pros go to Lipo is because they all run modified. In modified racing, batteries no longer matter. Regardless of what battery they use the weight is the same therefore the static tire load is the same. The efficiency of modern brushed and brushless motors is so good that you have plenty of runtime available. And with the the selection of motors available you can motor up to the limit of adhesion. That is why it is all about sponsorship and why for the average racer it makes no sense to base their buying decisions on what pros drive. For spec racing, I believe Nimh can offer significant advantage if managed properly, but the increased cost and work really begs the question; Why not run mod? I know in my spec racing I give away an advantage in power to a rival running Nimh, but I figure the time and money he spends on batteries, I can spend on setup and tires.
08-17-2008, 05:48 PM
#75
Tech Regular
iTrader: (3)
Im sorry to say this guys but i feel the ep touring class is going to die down soon. This class is getting too fast for anyone to have any fun and the manufactor's are making very competitve cars that where some are costing around $500 and they are straying from the fact that this hobby is suppose to be fun which isn't making it fun for us and you might be having fun now but wait until next year or the year later when everyone makes another car and its going to be around $750. i have actually stopped racing 1/10th touring because of the prices.