Need help selecting a battery

[zoom2136]

Hi guys I need help selecting a battery.

My selected component will be a Crystalyte HS3540 motor, with an Infineon 36-72V 40A controller and I was looking for a 48V 20Ah LifePo4 battery.

What is the difference between these 2 LifePo4 batteries, except the price?

48V20ha with a charger for 499$ http://www.bmsbattery.com/48v/537-48v-10ah-lithium-ion-electric-bicycle-battery-pack.html

48V20ha (38120) without a charger 530,10$ http://www.bmsbattery.com/packs/161-48v-20ah-38120-lifepo4-battery-16-cells-2p16s-ebike-battery-pack.html I know that this one is mandated for the Magic Pie... so maybe there is something there...

Thanks in advance.

 

[bowlofsalad]

Did you read the descriptions? I am not sure what else can be said beyond reading their descriptions and repeating what is observed in the description. This isn't really a battery technology question so much as it is a how to read description question.

One appears to include a charger, each are made out of different kinds of cells. The dimensions are left blank on one of the batteries, but I'd guess that they have different dimensions. They have different weights. If you want more detail or information, I suggest e-mailing these people for more information on each battery, some data is clearly not included.

Spend some time (30 seconds should do it) reading descriptions of things before you consider buying them. I also recommend researching (this involves using the search function or a search engine) places selling things. People sometimes like to write their opinions and experiences with various sellers, this might be useful to you as well.

 

[Gregory]

The cheaper one is made of low 0.75C rated pouches, and can only supply 15A continuous. You'll be stressing that battery with a 30A controller. It will be smaller and lighter.

The other uses 38120 cells which is presumably Headway cells that should be good for at least 3C rates (at a guess - I haven't tested the Headway cells) i.e. 60Amps continuous. It'll be heavier and larger.

 

[dogman dan]

Yep, I read it the same way. The second one is capable of a higher discharge rate, and is the one you need for a big fat watt hog 40 amps controller.

Choosing the first one, with a 15 amps discharge capacity to run a 40 amps controller would be battery murder.

HS and 40 amps, to me that's when the risk of fire and or increased complexity with lipo becomes more worth it. Or 20 ah a123's. You pick the fast stuff, then choose a battery that will have more voltage sag?

 

[zoom2136]

Thanks Dogman and Gregory. Your help was most appreciated.

As for the other guy... :?

I will be getting the more expensive ones.

 

[dogman dan]

Took some time for my replies to be worth reading. I just practiced a lot. No way would I have understood the battery descriptions at first either. Nor are all battery descriptions entirely the truth. Cut all c rate claims in half is one rule of thumb.

Bowl of Salad has made lots good comments and questions in other threads.

 

[zoom2136]

No problem

 

[zoom2136]

Ok, so the 48V20ha (38120) without a charger is available in:

15-30 AMP
30-60 AMP or
50-100 AMP

So if I understand you guys correctly I should probably get the 15-30 AMP (the estimated consumption is 21.6Wh/km at 100% throttle 1% grade as per ebikes.ca simulator).

Is there any downside, dangers, or any other reasons why I should not buy the 30-60 amp one, other than I'm trashing some money...

Thanks

 

[dnmun]

it's your money but the sun-thing28 guy on ebay is cheaper when delivery charges are finally piled on by BMS battery. he sells the 48V15Ah pack for $425 delivered.

 

[999zip999]

You have a 40 amp controller so the 30-60 bms is the min if a lot of long hills you might need the higher one. Depending how the bms are setup. The 40 amp. controller needs a C.A. so you can lower the amps demanded from the battery. The controller demands the battery to give and at 40amps or 55v charged times 40 amps 2200 watts. 55 x 40 = 2200 watts. The bayyery is like a horse and willl run till it dies. Just throw out the salad bowl it's been rotten for a while.

 

[dogman dan]

30-60 bms for that 40 amps controller.

Don't get a 15 ah sunthing lifepo4 for a 40 amps controller.

But you could be well advised not to trust bms battery as well.

 

[dnmun]

sun-thing28 guy only sells the 48V20Ah packs now. still the best deal around in spite of the unwarranted hostility towards him.

i guess it is part of the dislike of new things. like i said it is you money but this is a better deal than anything you get from BMS battery:

http://www.ebay.com/itm/NEW-48V-20AH-LiFePO4-Battery-Ebike-Rechargeable-Powerful-BMS-5A-Charger-DHL-/130907886557?pt=US_Rechargeable_Batteries&hash=item1e7ab7d3dd

 

[dogman dan]

My mistake, he wasn't talking about a 15 ah battery.

A 20 ah 2c cell could be run on a 40 amps controller without killing it. But not if I was riding it.

If he was offering the 4c cell you discussed the other day, that's different. Is he?

I just keep going by the cut all c rates in half rule. It applies to all. Sunthing, bms battery, pingbattery, sanyo, headway, A123, hobby king(where it's cut to 25%).

All of em. I'm hostile all right, to needlessly buying a battery inadequate for a big powerful controller. People seldom buy them to poke around at 20 mph.