1kwh pack recommendation

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Archer321   10 W

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1kwh pack recommendation

Post by Archer321 » Jun 29 2019 7:11pm

So if anyone remembers from my "Lead acid anyone?" thread, I am involved in Electrathon racing.
For the last four years I have been competing exclusively in the lead acid class but am now contemplating a change to lithium. I have a new car design in the works that would really be much more feasible with a 15lb lithium pack vs a 73lb lead acid one.
Electrathon rules require a lithium-ion pack weigh in at no more than 15lbs and not exceed 1kwh per manufacturers specifications. A lithium-iron-phosphate pack is limited to 29lbs and the same 1kwh capacity.
I have flexibility on the voltage from 36 to 60v and will pull an average of 900w continuous with occasional bursts of up to 2500w (probably 5 seconds or less).
My question is, what is the most cost effective way to go about this? Lithium-ion? Lithium-iron-phosphate?
Obviously I want to maximize the capacity and I'll want cells that are actually putting out what they are rated at (or more).
I have zero experience with lithium batteries and I'm not promising I'm actually going to make the switch, but I'm really kind of enamored with my new car design and it would definitely benefit from a lighter, smaller pack than the lead acid I currently use.
Cost is always an important factor however so it may not end up being a change I can afford to make.
But I gotta start somewhere...
So, recommendations?
( The more specific, the better)

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Rassy   10 MW

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Re: 1kwh pack recommendation

Post by Rassy » Jun 29 2019 10:44pm

For what it's worth, I like the relative safety of the LiFeP04 as compared to some of the other battery choices. If I was faced with your decision I would probably check out a 48V 20AH (about 1000WH) from Ping. The weight would be about 20 pounds.

https://www.pingbattery.com/servlet/the ... ate/Detail

Although more expensive and heavier then some of the others it makes most of that up by being good for more cycles. With the high rate BMS it will allow discharging at 3C, but using the battery at 1C or less will prolong its life. Cost is currently a little over $700 shipped.

Good luck with your project. :D

EDIT: Another thing I like about LiFeP04 is the discharge curve. The voltage holds at a fairly steady voltage during the majority of the discharge, unlike lead acid and some of the other battery choices that have a continuous voltage drop during the discharge cycle.
-Rassy-

Two Delta Trikes equipped with a Bafang BBS02
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999zip999   100 GW

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Re: 1kwh pack recommendation

Post by 999zip999 » Jun 29 2019 11:44pm

Please tell us more of the use of these battery . For what use please ? Yes tell us everything. Everything.

Archer321   10 W

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Re: 1kwh pack recommendation

Post by Archer321 » Jun 30 2019 12:14am

999zip999 wrote:
Jun 29 2019 11:44pm
Please tell us more of the use of these battery . For what use please ? Yes tell us everything. Everything.
Electrathon racing is a type of electric efficiency competition. Small, lightweight, generally 3 wheeled vehicles compete for an hour to see who can go the farthest on a battery capacity of 1kwh or less. The tracks vary from large parking lots to actual race tracks of differing types. Two of my favorites are a local half-mile oval stock car track and Barber Motorsports Park which is a 2.4 mile road course.

Rassy,
Thanks for the recommendation.
I'll check it out.

Archer321   10 W

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Re: 1kwh pack recommendation

Post by Archer321 » Jul 01 2019 6:31pm

And I suppose there's the whole question of using 92 or so cylindrical cells vs fewer of the prismatic cells.
More stuff of which I have no idea...

92 of anything seems like a pain...

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Rassy   10 MW

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Re: 1kwh pack recommendation

Post by Rassy » Jul 01 2019 8:00pm

A Ping LiFeP04 48V 20AH pack is made up from 64 5AH 3V prismatic cells 4P16S format. So it's still sort of mind boggling to think about, but I've personally purchased 7 of his batteries for myself and friends and never gone inside any of them except for a couple of BMS replacements. All except 1 are still in use, and it was damaged by a DIY friend several years ago and he simply replaced it with another Ping battery. These batteries are currently between 3 and 7 years old.
-Rassy-

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j bjork   10 kW

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Re: 1kwh pack recommendation

Post by j bjork » Jul 02 2019 2:13am

My thougt is lipo would have to be the only answer?

*Low IR means low voltage drop=more speed (if needed), and less heating of the battery= less wasted energy.

*Small and lightweight.

High working voltage compered to nominal.. I am not sure about this, but I think lipos are considered to have a nominal voltage of 3,7V? But at 3,7V they are near empty.
But when calculating Wh you are using nominal V x Ah right?

Archer321   10 W

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Re: 1kwh pack recommendation

Post by Archer321 » Jul 02 2019 6:17am

j bjork wrote:
Jul 02 2019 2:13am
I think lipos are considered to have a nominal voltage of 3,7V? But at 3,7V they are near empty.
But when calculating Wh you are using nominal V x Ah right?
That's the way I understand it.
Got a specific recommendation?

j bjork   10 kW

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Re: 1kwh pack recommendation

Post by j bjork » Jul 02 2019 7:51am

No, I dont have any specific recomendation. Most people here seems to use Turnigy from hobby king (me too). There are probably better altarnatives.

I think other Li chemistries usually used in 18650:s etc would hold less Wh because they are often empty at near 2,5V, but they still have 3,7V nominal. And higher internal resistance would give more losses, I don´t know if it will be markedly on the low powers you will be using. But if it is down to the last meters..

I guess you will have to settle with 13s, then you can overcharge and not pass 60V..
I don´t know how high you can go, but I know I have red that "lifeforphysics" charge his cells to 4,35V when it is racetime. If you go 14s you will only be able to charge to 4,25V before you pass 60V

I don´t know much about LiFeP04, but as far as I know their thing is long life and not very energy dense. So it seems like it is not so interesting for racing, but I might have missed something.

Archer321   10 W

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Re: 1kwh pack recommendation

Post by Archer321 » Jul 03 2019 6:46pm

Well after doing some internet snooping, it appears that lifepo4 packs may be cheaper to build. Even with their greater weight than lipo they are significantly lighter than my lead-acid batteries. I can put together a 960wh pack of "Topband" 25ah cells for about $480. The cells are listed as "new-open box".
Of course I have never heard of "Topband" but then again being new to lithium, I haven't heard of any of these manufacturers really. Anyone know anything about them???
I was momentarily tempted by the Headway 38120s cells because of their 10ah capacity and screw terminals but a 960wh pack with those would cost me about $800.
I'll keep researching but there are a LOT of options out there and I'm sure at least half of them are probably crap. It's easy to get lost...

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Rassy   10 MW

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Re: 1kwh pack recommendation

Post by Rassy » Jul 03 2019 7:44pm

Those "Topband" cells do look interesting. So if you put 12 of them in series you would have a nominal 36V 25AH battery. In your estimate did you include shipping, a BMS, and a charger?

If you do make your own battery from these cells please document the details. I could see making a 48V 10AH battery pack from 16 of their 10AH cells for my trike. I would probably use a BMS from Ping, because I like the way the LED display informs you that all cells are balanced and fully charged at the end of every charging cycle.

Whatever you decide to do, I think a LiFeP04 battery would be a good choice for your application where you are after efficiency instead of quick acceleration and high speeds needed in many types of racing.
-Rassy-

Two Delta Trikes equipped with a Bafang BBS02
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Archer321   10 W

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Re: 1kwh pack recommendation

Post by Archer321 » Jul 03 2019 7:56pm

Rassy wrote:
Jul 03 2019 7:44pm
Those "Topband" cells do look interesting. So if you put 12 of them in series you would have a nominal 36V 25AH battery. In your estimate did you include shipping, a BMS, and a charger?
Shipping, yes. Bms and charger, no.

Still have to research those.

Archer321   10 W

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Re: 1kwh pack recommendation

Post by Archer321 » Jul 04 2019 4:10pm

Checking out the Ping battery site.
Their 48v 20ah pack looks pretty good but I don't see any markings on it anywhere.
Maybe they just didn't show them in their pics.
I am required to have factory markings in place on my race batteries to show what they are (size, chemistry, etc.)and who made them.
And while they refer to it as a 48v 20ah pack (960wh), they state that the nominal voltage is 51.2v which would put it at 1,024wh.
Just over my 1kwh limit.
If their factory labeling said 48v I could probably use them, if it says 51.2v, I can't.
If there's no labeling at all, I can't.

Anybody got a Ping pack and could answer this???

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Rassy   10 MW

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Re: 1kwh pack recommendation

Post by Rassy » Jul 04 2019 4:56pm

My older Ping battery has no specification information on it, but my newer one (over 5 years old) has a label on it that says "Lithium Battery Pack", "MODEL 20V 4400mAh Battery", and "Date of production: 201505", along with other general info.

It does not say Ping or Ping Battery, etc on it. The 20V would not be voltage, since it is a nominal 48V 10AH Battery, which I would think would be listed as 4800mAh, but he may ship them partially discharged.

Ping probably had these labels printed up when the shipping rules started changing, and I have no idea what his current batteries may say on them.

My best suggestion is to ask him via email, and even explain why it is important to you, as he might be able to accommodate you if his current labeling isn't sufficient.

PINGPING227@Hotmail.com

Perhaps someone with a fairly new Ping battery will respond.
-Rassy-

Two Delta Trikes equipped with a Bafang BBS02
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Archer321   10 W

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Re: 1kwh pack recommendation

Post by Archer321 » Jul 04 2019 6:30pm

Rassy wrote:
Jul 04 2019 4:56pm

My best suggestion is to ask him via email, and even explain why it is important to you, as he might be able to accommodate you if his current labeling isn't sufficient.

PINGPING227@Hotmail.com

Perhaps someone with a fairly new Ping battery will respond.
An excellent suggestion.
I shall do so.

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