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LiHV value if track doesn't allow

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LiHV value if track doesn't allow

Old 02-22-2021, 07:07 PM
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Default LiHV value if track doesn't allow

Time to buy a few new batteries as I move into 17.5 buggy racing from a spec class. Track doesn't allow LiHV voltages so I won't be able to take advantage of that part of the battery. Question becomes, is it worth it to still buy LiHV and just charge to the 4.22 the track allows per cell?

I know LiHV batteries are essentially better quality LiPo cells so is the increased discharge potential where the value is?

Lastly, if I do decide to do that, I figure that last .13 volts is going to contain a significant amount of their capacity so how much do I need to upsize the capacity knowing I won't get to use a fair amount of it?
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Old 02-22-2021, 08:17 PM
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SMC claims there is no performance increase at 7.4v.

On capacity, this protek lihv shorty goes from 4600 at 7.6v to 4000 at 7.4v, or about 15 percent capacity loss. That probably holds across different brands and capacities
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Old 02-22-2021, 08:52 PM
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Just get the HV packs. Charge them to spec for when they check voltage, try charging them to 8.7 and see if you can go a little faster in practice. If you ever race somewhere that allows HV you can use your packs to their full capacity.
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Old 02-23-2021, 05:28 AM
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Bullet, can you afford to maintain an inventory of both? Perhaps a couple LiHV 7.6V for tracks that allow them, and the remainder conventional LiPo 7.4V?

Regarding undercharging the LiHVs: take into consideration what Tech is using to measure battery voltage at the track(s) where you race. For example, I tech my battery voltage using a HobbyWing program box. It measures slightly different than what charger voltage indicates. Usually lower, but why take the chance of getting bounced out of tech?

I mention using both as an interim transition until rules packages for battery use/mix at various tracks stabilize. My back yard track allows for both. 7.4V 2S x 4600 LiPo shorty is the spec pack for the 17.5 ST's. The 7.6V LiHV 2S x 4600 shorty's are an option pack for my 21.5 ST's.

Cheers. 'AC'
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Old 02-23-2021, 05:45 AM
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Originally Posted by AHR43 View Post
Bullet, can you afford to maintain an inventory of both? Perhaps a couple LiHV 7.6V for tracks that allow them, and the remainder conventional LiPo 7.4V?

Regarding undercharging the LiHVs: take into consideration what Tech is using to measure battery voltage at the track(s) where you race. For example, I tech my battery voltage using a HobbyWing program box. It measures slightly different than what charger voltage indicates. Usually lower, but why take the chance of getting bounced out of tech?

I mention using both as an interim transition until rules packages for battery use/mix at various tracks stabilize. My back yard track allows for both. 7.4V 2S x 4600 LiPo shorty is the spec pack for the 17.5 ST's. The 7.6V LiHV 2S x 4600 shorty's are an option pack for my 21.5 ST's.

Cheers. 'AC'
I'm not replacing everything and with LiPos you don't need the total number of packs that we used to. I am adding 1 car to the fleet and will need another race battery for it. Just wanting to place my money in the right place as the 17.5 class is relian and good motors and batteries.
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Old 02-23-2021, 05:54 AM
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Originally Posted by Silverbullet555 View Post
I'm not replacing everything and with LiPos you don't need the total number of packs that we used to. I am adding 1 car to the fleet and will need another race battery for it. Just wanting to place my money in the right place as the 17.5 class is relian and good motors and batteries.
Agree. My inventory is considerable lower with LiPo / LiHV than what it once was with NiMH round cells. Maintain two LiPo's and two LiHV's in active status. Rotate them between six ST's for events, practice and test. For bench test, maintain a 2s x 3500 LiPo shorty. It is quick to charge for test and discharge for storage.

Trying here to keep a thumb on the pulse of what is going on with or without track transition to 7.6V. Lot of guys will not be able to fade the expense of a rapid change-over. See it as possibly a phased transition over time, if at all.

Cheers and good luck racing. 'AC'
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Old 02-23-2021, 06:43 AM
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Originally Posted by Khan48 View Post
SMC claims there is no performance increase at 7.4v.
Unfortunately this article doesn't discuss the potential for LiHV to perform better at 4.22/cell when charged at 40A..... while a regular LiPo cell can get about the same performance if also boosted at 40A, most cells will degrade very quickly where LiHV cells can handle the abuse of 40A charge rates, boosting is discussed more here and something I personally have found to be a distinct advantage in stock racing:

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Old 02-23-2021, 07:16 AM
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I just run Reedy packs and the newest ones are only available in HV and I charge them to HV some times when theres no tech but not that often. Especially with my wheeler that uses the thin pack. They are the 6100mah shorty and 4100 thin at high volts and about 5400 or 3700 at normal voltage.

Usually I just charge them to 4.2v/c and that is nice because you aren't charging the cell to its full capacity and extends its life. When I run mod I even cut it down to 4.1 or 4.05 to get rid of the crazy punch for the first couple laps. Its nice to be able to charge to HV in some situations but since your club techs for it most of the time it doesn't really matter.

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Old 02-23-2021, 07:30 AM
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Seems that if I stay in the 4500ish range on capacity it should work out pretty well. And, if the track ever changes to allow LiHV I won't have to feel a need to buy something else. And, if I want to smoke my son when he starts to beat me on the track, I can up charge a little. ;-)
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Old 02-23-2021, 05:46 PM
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Originally Posted by Khan48 View Post
SMC claims there is no performance increase at 7.4v.

On capacity, this protek lihv shorty goes from 4600 at 7.6v to 4000 at 7.4v, or about 15 percent capacity loss. That probably holds across different brands and capacities
How do you like the protek lihv shorty?
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Old 02-25-2021, 02:22 PM
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Do you guys set your cut off voltage on your esc higher, for hv packs?

In other words, is the minimum voltage per cell higher with lihv?

I went ahead and set my cut off at 3.4 per cell on my rx8, just to be on the safe side.
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