Battery Knowledge Base - WIP - Rough Draft

I don’t understand how you calculate the Vdrop at peak current (from datasheet?) but think that this website will help as it has loads of discharge curves and battery reviews (http://lygte-info.dk/review/batteries2012/Common18650comparator.php). I would also like to know your opinion on these two batteries (https://eu.nkon.nl/rechargeable/18650-size/panasonic-ncr18650pf-3-7v-2900mah.html) and (https://eu.nkon.nl/rechargeable/18650-size/samsung-inr18650-29e.html) as I am planning on a 7s 6p setup for commuting and found these are cheaper than the samsung 25Rs have a larger capacity and still a decent discharge (hoping that I won’t need to pull more than 40A on a 7S on flat tarmac roads.

I already have all of Henrik’s data (the owner/writer of Lygte) for the relevant cells along with my own experimemtal data.

different li-ion chemistries with different characteristics

http://batteryuniversity.com/learn/archive/the_high_power_lithium_ion

Does anyone have an opinion on the batteries I posted above considering my setup - would they be ‘better’ than the 25Rs - they have a higher capacity and I was already going to limit my current using the VESC to 40-45A max?

@Print3r To be honest, u might as well try in this topic:

I think more users are hooked up there, plus maybe this topic for now could be kept for general questions related to all batteries and the finalization of what kind of info needs to be gathered / told about etc.

I cannot really compare these, maybe take Sanyo GA or 30Q and then take a look how they compare.

If you are not straining them to the max, it might be okay, especially considering that you wont pull 40A on flats probably… unless going like +40kph I imagine.

Many thanks, apologies for steering this off-topic.

@PXSS, You should really stop creating this on here, it’s a horrible medium for making a factual in-depth review of batteries, and it’s going to be messy (and already is). Make a website, and simply link it, that way you can make it properly. For example, when saying something, link it to things that prove it (more things the better), and try to offer alternative thoughts as well to show you’re not just thinking of one scenario, @lowGuido has already given you a shining example of how LiPo’s can be arranged to make an ultra-slim and cost-effective board.

Also some constructive criticism: -

If it’s a battery knowledge base, why are you starting with your conclusions? You should present information and let people make up their own minds, and based on what you wrote you’re definitely biased. Why can’t you think of a single reason to use LifePo4? And why are you insinuating that only poor or un-skilled people use LiPo’s? You should phrase it more tactfully, like listing the pro’s of Lipo’s as “being cheap” and “already come with connectors”

I personally think that without having all three types of battery to test on a board, you can’t really present anything substantially useful, it’s all good shouting out numbers, but you ideally need hard evidence to back up any performance claims.

Your spreadsheets in post 28 look good, but you should substitute it for bar charts, it’ll display that info far more elegantly (even better, present both the spreadsheet and bar chart). Also, why aren’t you adding in the hidden costs of making packs? Where’s the cost for the spot welder factored in?

*Sorry if i’m attacking your post, really didn’t want this to read like it, but I think I failed that

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@PXSS I have to agree with @riva_00. The organization could use some work. I could be beneficial to make a pros/cons list in a google sheet and share it here. Then when people have new ideas they can comment/add to the sheet and we can arrive at the best Battery Knowledge base that is easy to come by, rather than having to read through an entire thread.

@PXSS I hope you dont mind what other folks are saying here… just keep on doing the work, man :wink:

As to @riva_00 I understand your concern about some of the ‘‘flames’’ PXSS made… though I think he will explain his beliefs… and once he makes the info more structured, it will be way more easy to look through it…

He just said he spent a night during calculations or such, so I must say his output (visual style) might not be the best one yet because of the time constrain…

He just put the stuff he made, so we can see and share our thoughts onto…

If not him, it was already outpointed to, that Lifepo pack out of A123 cells are very good for ‘‘power dense’’ system, utilising only 1P config of batteries but for them to perform to their ‘‘best potential’’ they need to be properly cooled, otherwise they just get too hot to continue their current delivery…

If im not mistaken, this might be some of the early concerns the A123 had… or what might have caused them to cease their operation a bit…

I agree with both of you, @riva_00 and @Challlsss. My post reads horribly right now. It was something I whipped up at midnight and really only posted by accident before I had any time to put any real meat and substance to it.

I do not want to create a website as I feel that defeats the purpose of reaching members of this forum and will eventually be forgotten. Here, it will get more visibility and help guide people.

The OP will at some point have all the information to help people make the right choice on batteries. That is not the case right now. It also reads very biased as is right now because as I said, it wasn’t meant to be published just yet and most of the little snippets were just self reminders to fill certain sections and some points I want to touch upon.

I have lots of experience with both Li-ions and Lipos in skateboards and other applications. I have a lot of test data to back up my claims that i will hopefully be able to upload to a google drive at some point. The main reason I don’t want to do this right now is that I need to make sure that everything I post on here doesn’t overlap with my job. I am an aerospace engineer that does performance analysis and design on electric powered aircraft and my work is proprietary and some of it government property, so I need to walk a very fine line on not using any data that I have acquired through work. This makes it hard for me not to seem biased as there is a lot I cannot share…

As far as scenarios I have not taken into account, like the one brought forward by @lowGuido. That is trully the purpose of this thread. I fully appreciate that input! The more people find holes in the OP, the more I will be able to add to it and have a better guide for all!

I appreciate your input and it’ll take some time to get this thread to the point of being a true database and guide but we have to start somewhere…

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I tested the voltage of all my new batteries. They range from 3.407 to 3.61 Does the state of charge out of the box mean anything? Should I mix up the high and low ones to make parallel groups or put the ones with similar voltage together and let the BMS fix it? I have 4 extra should I just discard the ones with the lowest voltage?

The voltage can and will vary. Usually batteries within the same batch and shipping come with the same voltage. In my experience close to 3.5v per cell, sometimes there are some cells with lower voltage and some with higher. I wouldn’t worry too much about it. You can’t really tell the health by voltage.

The best way to check health is by checking the internal resistance of the cells. This can be done manually by fully charging the cells and then waiting at least 5 minutes for the voltage to stabilize for no load. You can then load the cells at 1A and measure the voltage. Unload them and wait another 2-3 minutes, measure voltage and then load them at 3A and measure voltage drop. Repeat for 5A. Then with this you can calculate the internal resistance by using this equation: Rint = (V0 - V1) / I R = internal resistance V0 = No load voltage V1 = Voltage under load I = Current Then you can take the average of the three values. Some RC chargers also do this process automatically, for example my iCharger 308 Duo, has 2 channels which can measure up to 8 cells in series. so I can measure the internal resistance of 16 cells in less than a minute.

The lower the internal resistance of the cells the better. So you can choose the 4 cells with the highest internal resistance and not use them, or if they’re all fairly close then you can just use them all

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My feelings exactly. I use lipos because li-ion sag too much for me in a 12s4p config. I am going to be trying a 12s5p config soon which should hopefully be a bit better, but for my own personal boards, lipos perform way better. You stay at a higher voltage for longer, so late in my ride, I only lose 1-2 mph in top speed. With li-ion, I lose 5-6 mph later in my ride. Also, because of less sag, I get more range from an 8Ah lipo than a 10Ah li-ion. A lot of the energy near the end of the li-ion can’t be used without sagging it to levels that could damage the cells.

I wouldn’t say lipos are only a poor mans choice. They are good if:

  • You need to save money
  • You need to minimize sag (which is for anyone with steep hills)
  • You want to maintain performance through out the entire ride
  • You want to fit the battery into a small space that li-ion simple can’t fit.

Saying they are a poor mans choice only is simply not true.

@evoheyax What Li-ions have you tried? I’m sure your issue was either having the wrong liion (25R) or wrong settings.

IMO, Lipos are good for the first and last of your points. Steep hills can b e conquered with the right Li-ion cells as I’ve stated before. Now if you want a board with serious power, I mean lots of power, then yes. Lipos are the way to go. Maintaining performance through the entire ride is a matter of wrong settings IMO

Ask @mmaner, he’s got a 25R 10S4P pack, a Lipo pack and a 30Q 10S4P pack. I think he’s also tried a Lifepo4 pack before. His 30Q pack is anything but lacking in power

I have and I have. I love the 30q pack, it has as much torque as my 10s lipo packs. It’s obviously more expensive but you get more charges/discharges so it comes out pretty close to even. I only use my 10s 25r pack on my beater board, it says in hills pretty bad.

I still feel that lipos have a place in powered boards, they are cheap and powerful, they are easy to purchase and easy to build series packs with.

Given a large budget, I’d probably go with 30q’s but when you constantly build boards that’s not really an option :grinning:.

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I made this 18650 lithium ion cell identification reference guide a while back for another community. maybe its of use to some here.

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Any follow up on this one?

IF someone wants to go ‘‘webpage style’’…

I found this page to be higly educational and informative (also from the ‘‘looks’’ perspective:

https://www.dozuki.com/Tech_Writing/chapter/4


I’ve grown way too busy at work to keep up with this shamefully… Currently working 14 hour days and my dog takes up the rest of my time…