Losing some weight

on the contrary… I do not have the time… I was being polite!

That’s alright for me then.

didn’t make sense dude…

But it did though. Summary of everything I’ve written so far :

What’s the point of mounting a 200A lipo battery if your setup only draws 50A?

Why not trade higher “wasted” amps for higher capacity instead. That was my point. Higher cap for same weight.

To each his poison, I could not fit lipos in my build. Li-ion just got the bill done. That was my point.

BTW we’re getting off topic ain’t we?

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@Vanarian right now it weighs 13.8 lbs or 6.1 kg. Keep in mind this is with 10s4p Li Ion which makes most of the weight. Its very fun, takes a little getting used to but its by far my favorite board to ride. I like less flex and the mobility.

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Thanks for the tips. Will look at the wheels, right now I have the standard 90mm.

But what I see from most of the comments I should not cut on batteries.

Any more updates on how much your board weighs?

@karma is basically correct. Lipos beat li-ion when it comes to energy density (energy per unit volume). However the specific energy (energy per unit mass) of lipos is identical to that of li-ion. Either way, the difference is really small :slight_smile:

Sources: https://en.wikipedia.org/wiki/Lithium_polymer_battery and https://en.wikipedia.org/wiki/Lithium-ion_battery

Lipos ARE li-ion. They both use lithium ion technology. But cylinder cell li-ions are much more energy dense than lipos.

Just do the math any literally any hobby lipo pack vs a 18650 cell. Here’s an example…

Turnigy 3s 2200mah 208g pack

3.7v * 3s * 2.2ah = 24.2 wh per 208g. Which is 117.4 wh/kg

Samsung 25r 18650 cell 1s 2500mah 43g

3.6v * 1s * 2.5ah = 9wh per 43g. Which is 209.3 wh/kg

This particular liion cylinder cell is nearly twice as dense as a typical lipo battery you’d use for diy.

As for volumetric energy density, you’ll find a similar result. However lipos can be configured to be much flatter than any 18650 pack.

@Cobber @karma

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ok… so a pair of these come in at 133.2 wh/kg… but that doesn’t matter they work perfectly with no sag in extreme use at 12s1p until I hit cut off, the same can not be said for… am I missing something?

This post is about losing weight. I provided an example with math to prove how to effectively lose weight on a board. If you have other questions I suggest making a new thread.

@mptrs is running the equivalent of a 10S1P 30C (continuous discharge) 8000mAh lipo. That allows for a theoretical max load of 240A. 25R cells would need a 12P config to reach this level of discharge capability. Surely that is something to consider? :slight_smile:

@chaka goes as far as building 10s6p packs due to the discharge rates of 18650 cells. That is 2.5 kg of cells.

Appropriate discharge potential for various setups is an entirely different topic… We shouldn’t be spreading false information, though. That said, there are plenty of people that run 10s3p setups which are fairly lightweight. The discharge advantage has already been talked about in plenty of other threads.

There’s a way to do this. I think it’s called working out. Jk

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Yes @Jinra and in context I think lipos provide the lowest weight practical solution. In fact the entire RC industry proves this point.

Yes Baty, that is what I have been alluding to… As for false information trying to say discharge is irrelevant is kind of leading someone down the garden path. With high discharge you can have a tiny battery that weighs less…

the most practical advice for @mptrs to save weight would be to try out his board with only 1 of his existing Lipo’s… still won’t really save that much :frowning: Might be a bit much for his battery depending on rider weight & conditions (hills, wind)… I personally wouldn’t.

You could run a 2P 18650 build with the right ESC configuration, so yes I do think the topic is best saved for something else. There are production boards that run 2P config. Boosted themselves use 1P on a lifepo4 cell…

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Yes by throttling the build you could use a battery that would otherwise be unsuitable… On topic: I do not think OP should drop the coin on such a battery.

Mike has the right idea for low weight :joy:

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:raised_hands: 13lbs for 360wh 10s4p 149kv 6374 and still dropping! Next step is for lighter wheels, which will need retrofitting for pulleys. also have plans for dual diagonal drive and maybe carbon fiber board because it is already very rigid.

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Well the point still is, IMHO, OP should not cut on batteries to save weight and he seems to agree.

Now saying that a higher amp battery allows for smaller battery doesn’t mean you crave equal capacity in that smaller battery (read RANGE here) . You only get a small battery able to deliver sufficient power for your build. I think @Jinra explained it better than I did.

I’m too lazy to do maths for this as it’s not thread topic.

When did it become a Lipo / 18650 contest?

Thanks for shining some more light on this @Jinra. I had been going around thinking LiPos had better Energy density but in reality I was wrong. The discharge rate for LiPos are a lot higher than Li-ion but not energy density. I had to do some calculations and I came up with the same result as you. The best Wh/Kg ratio I found on normal LiPos was around 164Wh/kg. The best I found on Li-Ion was around 250Wh/Kg. THAT IS A HUGE DIFFERENCE.

Here is my conclusion: If you are going to go for a smaller battery and you are going to draw a lot of power from your setup, LiPos will be better due to the extreme discharge capabilities. Something like a 6S1P/8S1P would be a great example where LiPos are a better option. ( You wouldn’t get very far but you could still supply enough power for a little while) If you are going for a bigger battery like 10S4P where discharge from 4 good Li-Ion cells (Like Samsung 30Q) in parallel can handle the need, it would be better to go with Li-Ion cells since you can get the same Wh for around 65% of the weight of LiPos.

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