Battery capacity question

[DLK83]

I was at the hobby store last night, they had a 4s, 4600mah 110/220c Powerhobby battery there that was considerably physically smaller than any 4s battery I have or have been looking at... I have a Powerhobby 6s 5000mah 100/200c battery that has been cycled a ton, completely submerged under water and all around abused, it still takes a charge great, has good run time and great power... my question is, even tho C ratings are mostly snake oil, do you think 2 of the 4600mah 110/220c batteries would get the job done in an 8s drag Infraction? They would provide a huge weight savings, and allow for far more room on the chassis to place esc, cap pack, GPS, etc... I'm trying to keep the stock chassis so any extra room is always welcome and weight savings can't hurt in a drag race scenario, what are your thoughts?

 

[LibertyMKiii]

Short packs are the go-to in drag racing right now.
It is understood that the shorter distance across the cell helps them deliver the high amperage needs better.

I wouldn't imagine you need tons of mAh for drag racing, assuming the voltage does not sag too much. (higher mAh helps combat that some)

 

[Killacam]

that's basically 2 shorty packs stacked on top of each other, which are used for 2s racing. i don't think you'll have an issue. i use powerhobby batteries and they are high quality.

 

[DLK83]

Thanks guys, appreciate the feedback! Is there any sort of formula/equation that can be used to get a baseline for what the minimum size battery you should use for a certain application? Is it as simple as just making sure your supply is greater than the demand as far as amps?

 

[SrC]

For No prep drag, the events are short and brief. Low capacity lipos are great for this reason. Lower capacity Lipos are def. an advantage. C rates matter for successful trap speeds. And saving weight matters. Much is trial and error what lipo(s) works for you and your gearing setup.

 

[21STalion]

Shorty packs are so good, amazing how much smaller they are, almost as if they are made with a different technology (but not)

Once I started buying Shorty packs I don't want to use my full size ones anymore

 

[SrC]

Yea I tend to lean to 5k capacities. Give or take. My favorite. I rather have several smaller packs and swap them out as needed. Rather than having that one 8k mah pack. Added weight makes the rig handle less nimbly. Added weight creates more heat and taxes the drivetrain more. Extra weight adds more damage when you wreck. Lipos eject easier ripping/tearing out your velcro straps and lipo tray, then the ESC's rip out, etc. The fire liability increases with all this. Been there.

 

[DLK83]

Follow up question to this; are the claimed specs(c-rating/mah)of a "HV" lipo only true when the battery is charged to 4.35v per cell?? As opposed to a regular lipo where claimed specs are met at 4.2v per cell? I am asking because I was going to buy 2 of the batteries I pictured in the first post, but just found these batteries, they're slightly smaller in capacity but have a slightly higher claimed c-rating, which probably wouldn't be noticeable anyways in the given application, but they weigh 4oz less each, which is another 1/2lb savings... which one of these would be most beneficial in a drag car application? Also a $40 difference...

 

[RedOctobyr]

Follow up question to this; are the claimed specs(c-rating/mah)of a "HV" lipo only true when the battery is charged to 4.35v per cell?? As opposed to a regular lipo where claimed specs are met at 4.2v per cell?

I have not researched, or shopped for, High Voltage LiPos, which are apparently referred to a LiHV, from what I'm reading. But it would require additional energy/capacity into the battery, to charge past 4.2V.

Given what we all know about Marketing Departments, I'm going to guess that they will list the largest numbers possible. Making up values, if a LiHV pack stored 1000mAh at 4.2V, but could be safely charged to 4.35V, and stored 1100mAh at that voltage, how do you think they would list it? My money is on 1100mAh. I think they'll rate capacity based on the LiHV voltage.

That seems more likely than them taking the "honorable" approach and listing it as 1000mAh, to be comparable with standard LiPos, and silently also giving you an extra 100mAh, but being too-humble to mention it

 

[Hector_Fisher]

Follow up question to this; are the claimed specs(c-rating/mah)of a "HV" lipo only true when the battery is charged to 4.35v per cell?? As opposed to a regular lipo where claimed specs are met at 4.2v per cell? I am asking because I was going to buy 2 of the batteries I pictured in the first post, but just found these batteries, they're slightly smaller in capacity but have a slightly higher claimed c-rating, which probably wouldn't be noticeable anyways in the given application, but they weigh 4oz less each, which is another 1/2lb savings... which one of these would be most beneficial in a drag car application? Also a $40 difference...

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My experience is generally that HV batteries will list the mah for the 4.35v per cell, not the 4 2v per cell. At 4.2, you're likely to be around 3700-3800 from what I've seen.

Remember, C rating means basically nothing.