quick battery question

[bike4life]

So i purchased a 1000w lithium battery off ebay for 170 about a month ago.......
It says there are 13s x 4p, which i confirmed yeilding a total of 52 cells....
Now these are 18650 batteries.....
1000/52 = 20watts hours per cell!!!! Is this even possible, arent 18650 cells rated for
4v x 3 amps approx = 12 watt hours.....

Does my battery actually have 1000watts of capacity??? Or is it a scam. Thanks...
The numbers dont seem to add up...

 

[john61ct]

First off, watts have nothing to do with energy capacity.

Watts measures power, and usually C-rate is a better unit, relative to the mAh, which is your unit for energy capacity.

Exactly what cells are used?

Never buy a pack without knowing that, and lots of fakes out there.

So really you need a known trusted supply chain, both maker and seller.

Which of course means paying lots more than the 99.9% which are liars and scammers.

So 4P, say they are 2000mAh cells, means an 8Ah battery. At 48V nominal maybe 350Wh, but that is not a good unit to use normally.

If the cells are capable of 10C peak, for short bursts then that means 80A, *48 = ~3500W but maybe just a few seconds, and voltage sags.

1000W might be a continuous power rating, so ÷48V = 20A which is 2-3C so that would only be for 20-25min range.

And note you cannot believe the Watt ratings nor C-rates, at all, only actual testing tells the truth.

Capacity in mAh per cell is usually at least in the ballpark, but only with an honest supplier.

 

[spinningmagnets]

Many Chinese companies are not good at English, and to be fair, the US is actually only a small part of their customer base. Chinese customers buy many more times the ebike products, compared to US customers.

There are a lot of 1,000W hubmotor kits being sold everywhere, so this company is likely advertising that this battery pack can supply the needs of the common 1,000W hubmotors and controllers.

1,000W from a 13S / 48V is 21A from the whole pack (which sounds right for a temporary peak), and from a 4P arrangement, that is 5A per cell, which is very believable.

 

[E-HP]

Sounds about right, but at less $3.27 per cell (probably a good bit less due to other parts, and to make room for profit), they are probably no name cells.

 

[MadRhino]

Sounds about right, but at less $3.27 per cell (probably a good bit less due to other parts, and to make room for profit), they are probably no name cells.

Yep. No magic in this world. You get what you pay for. Quality cells are expansive, so are good batteries.

 

[john61ct]

But just because it's expensive, does not mean it's necessarily good either.

Don't you think there is a business / employment opportunity here?

Members doing review & testing services, accepting delivery from the cheap Chinese suppliers,

at least a few on each continent, and

either fixing problems or supporting refund claims,

maybe other members doing custom builds,

all fully transparent here on the forums. . .

 

[E-HP]

But just because it's expensive, does not mean it's necessarily good either.

Yup, you can't guaranty that you'll get what you pay for, but you CAN guaranty that you won't get something you didn't pay for, if it's ultimately sourced from China.

 

[john61ct]

So if only a low C-rate is required

? peak 5C / 2C continuous ?

and say no higher than 2000mAh per cell assumed

plus nothing assumed for longevity past say 200 cycles

what do y'all think would be the minimum price per kWh that would give at least a fighting chance out of the Ali / eBay sellers ?

 

[MadRhino]

Some Chinese sellers are honest merchants. They detail/spec exactly what they sell, and often give you choice to upgrade if you want genuine cells.
Some other just keep silent about specs and assume that you are not expecting a Ferrari for the price of a go-cart.

But, there are many who are deliberately leading people to believe that they will get quality products for unbelievable price. And some clients are delusional believers, or just ignorant beginners, to buy their sh*t. Still, not saying that China has the monopole of crooks and frauds. There are many sellers of the western world who are buying the cheapest Chinese copies, to sell them with huge profit to their naive neighbours.

 

[john61ct]

Yes of course

if some of us systematically self-organized, could help each other earn a fair wage for time spent, be part of the solution.

exactly why communities like this can help be a force for good, more experienced members helping the noobs.

Members doing review & testing services, accepting delivery from the cheap Chinese suppliers,

at least a few on each continent, and

either fixing problems or supporting refund claims,

maybe other members doing custom builds,

all fully transparent here on the forums. . .

 

[MikeSSS]

Battery babble: in general terms

A lithium cell, as in an 18650 cell, has a full charge voltage and voltage decreases as energy is withdrawn from the cell. 4.2 volts is generally considered full charge voltage. I use 3.5 volts as the lowest voltage I want to discharge a cell to. That said, I don't like to charge to 4.2 volts, but prefer to charge to 4.0 volts per cell. Charging to a maximum of 4.0 volts per cell and discharging to a only 3.5 volts per cell or higher than 3.5 volts per cell, is supposed to maximize battery life. My 13s, 4p battery is 3.5 years old and is doing just fine. Charging a lithium battery fully to 4.2 volts per cell and then letting it sit unused for weeks or months is bad for the battery.

A 13s battery, charged to 4.2 volts per cell, has a voltage of 13 cells * 4.2 v/cell = 54.6 volts. This is a stick of 13 cells in series.
A 13s battery, charged to 4.0 volts per cell, has a voltage of 13 cells * 4.0 v/cell = 52.0 volts
A 13s battery, discharged to 3.5 volts per cell, has a voltage of 13 cells * 3.5 v/cell = 45.5 volts
48 volts is sort of a figure of speech, or a nominal voltage, or a voltage under some load.

Voltage is a measure of push the battery has, pushing electrons through wires. A 48v battery will provide more power to a motor than a 36v battery...at full throttle, but we don't ride at full throttle. At a given power setting, a 48v battery will provide that power with less current (amps) than a 36v battery. As an example, if a bike has a 25 mph top speed and you are riding at 15 mph, the 48v battery would power the bike with less amps than a 36v battery. 36v/48v = 0.75, that is the 48v battery would send only 75% as many amps as the 36v battery, to produce the same power. That's the advantage of higher battery voltage. Note, it's easier for a system to handle higher voltage than to handle higher amperage.

Amp hours is a measure of battery capacity. An 18650 cell having 2.0 Ah capacity, holds less energy than a cell with 3.5 Ah capacity. One stick of 13 cells, each cell having 3.5 Ah capacity, still has only 3.5 Ah of capacity. Two such 13 cell sticks, wired in parallel has 2 x 3.5 Ah = 7.0 Ah capacity. This would be a 13s, 2p battery. Four such 13 cell sticks, wired in parallel, would have a battery capacity of 4 x 3.5 Ah = 14 Ah capacity. Note: battery capacity is a measure of how many amps a battery can produce for how long. Example, a 14 Ah battery can produce 14 amps for 1 hour, or 7 amps for 2 hours, or 3.5 amps for 4 hours, or 1.4 amps for 10 hours. There's a little more to it than that, but this is close enough for most ebike purposes.

Watt hours is a measure of how much energy a battery holds. As an example, a 13s, 4p battery is said to be a 48v battery, but really it is a 54.6v battery when fully charged to 4.2 v/cell, and a 45.5v battery when discharged to 3.5 v/cell. Voltage declining during use complicates the math, so we simplify by calling the battery a 48v battery. Volts times Amps = Watts. Volts x Amps = Watts. OK. Watts are the units of power, power causes speed, but not distance. To get distance we need energy, energy stored in the battery. Watt hours, Wh, is a measure of energy storage. As an example, a 13s, 4p battery of 48v and 14 Ah capacity, has 48v x 14 Ah = 672 Wh of energy storage. Now were getting somewhere, Wh are a valuable number for calculating things like range on a charge. Example: during 464 miles of riding, my average Watts of battery use were 163W.

Alright, if I divide my battery energy storage by my power average then I should get my range, right? Example: 672 Wh of energy divided by 163 W of power = hours of riding. 672 Wh / 163 W = 4.1 hours of riding. Woah, not so fast. Reason is that I can't use 100% of my battery energy and have long life from my expensive battery. To have long battery life my operating protocol is to use only about 40% of my battery energy. That is, I never charge to 100% which would be 54.6v, but only charge to 52.0v. Discharge never goes below 45.5v. Hmmm, I'm only using about 40% of my rated battery energy storage. So, 672 Wh / 163 W * 0.40 = 1.65 hours of riding. Now for distance: multiply hours of riding times average speed = distance. 1.65 h x 12.4 mph = 20.4 miles of range. About range, riding slower uses less power and thus increases range. For the 464 miles my actual speed average was about 11.0 mph and calculated average range was 22.6 miles.

So a battery that might give 50 miles range, going from full charge to low voltage cutoff ... is only used for 20 miles more or less? Yes, to extend battery life. If I want to go farther, and often do, I just ride slower or take a second battery.

Cost: My gas bike uses a 33cc Subaru Robin four stroke engine, it costs about 1.7 cents a mile to operate, for gas. The ebike costs only 0.10 cents per mile for electricity. But the battery cost is about 8 cents per mile, if the battery lasts 5 years. Batteries can be considered a consumable item, like gasoline, and an expensive consumable at that. Long battery life for this reason important.

Batteries have a lot of variables and there are many different ways of looking at them and their use.

I hope this helps. Keep us posted on what you get, what you do and how it works out.

Mike

 

[docw009]

Here's a battery to avoid on ebay. 48V20AH 13s-4P, for 1000W ebike, even cheaper than the OP's pack at $140.
https://www.ebay.com/itm/Ebike-Battery-48V-20ah-Lithium-ion-Battery-with-Charger-for-1000w-Electric-Bike/274341708971?hash=item3fe00a44ab:g:sCAAAOSwCKlenHM8

It features four 5AH cells in parallel to get that 20AH. That must be those double secret cells used by the Chinese moon shuttles, as commercial cells doesn't even exceed 4AH.

I guess it's typical ebay liars at work. Is that a scam?

It might work for a while. It should be capable of 20A which is 4A per cell, and that is 1000W. It will have a short life though, relative to quality cells. Maybe 200 cycles before it's half gone.

Best to get a battery made with name brand cells with a known type. There are high capacity and low capacity Samsungs, so you have to know which type. If you can't do that, there are some decent chinese cells, but I dunno what they are.

 

[john61ct]

The very vigorous and objective testing performed by our members results published here should be your guide.

example https://www.google.com/search?q=site%3Aendless-sphere.com+LG+HG2

most recent by respected tech members is better than older opinions by lay ones

http://w.endless-sphere.com/forums/viewtopic.php?f=14&t=103092&start=275#p1528359

 

[bike4life]

Battery babble: in general terms

A lithium cell, as in an 18650 cell, has a full charge voltage and voltage decreases as energy is withdrawn from the cell. 4.2 volts is generally considered full charge voltage. I use 3.5 volts as the lowest voltage I want to discharge a cell to. That said, I don't like to charge to 4.2 volts, but prefer to charge to 4.0 volts per cell. Charging to a maximum of 4.0 volts per cell and discharging to a only 3.5 volts per cell or higher than 3.5 volts per cell, is supposed to maximize battery life. My 13s, 4p battery is 3.5 years old and is doing just fine. Charging a lithium battery fully to 4.2 volts per cell and then letting it sit unused for weeks or months is bad for the battery.

A 13s battery, charged to 4.2 volts per cell, has a voltage of 13 cells * 4.2 v/cell = 54.6 volts. This is a stick of 13 cells in series.
A 13s battery, charged to 4.0 volts per cell, has a voltage of 13 cells * 4.0 v/cell = 52.0 volts
A 13s battery, discharged to 3.5 volts per cell, has a voltage of 13 cells * 3.5 v/cell = 45.5 volts
48 volts is sort of a figure of speech, or a nominal voltage, or a voltage under some load.

Voltage is a measure of push the battery has, pushing electrons through wires. A 48v battery will provide more power to a motor than a 36v battery...at full throttle, but we don't ride at full throttle. At a given power setting, a 48v battery will provide that power with less current (amps) than a 36v battery. As an example, if a bike has a 25 mph top speed and you are riding at 15 mph, the 48v battery would power the bike with less amps than a 36v battery. 36v/48v = 0.75, that is the 48v battery would send only 75% as many amps as the 36v battery, to produce the same power. That's the advantage of higher battery voltage. Note, it's easier for a system to handle higher voltage than to handle higher amperage.

Amp hours is a measure of battery capacity. An 18650 cell having 2.0 Ah capacity, holds less energy than a cell with 3.5 Ah capacity. One stick of 13 cells, each cell having 3.5 Ah capacity, still has only 3.5 Ah of capacity. Two such 13 cell sticks, wired in parallel has 2 x 3.5 Ah = 7.0 Ah capacity. This would be a 13s, 2p battery. Four such 13 cell sticks, wired in parallel, would have a battery capacity of 4 x 3.5 Ah = 14 Ah capacity. Note: battery capacity is a measure of how many amps a battery can produce for how long. Example, a 14 Ah battery can produce 14 amps for 1 hour, or 7 amps for 2 hours, or 3.5 amps for 4 hours, or 1.4 amps for 10 hours. There's a little more to it than that, but this is close enough for most ebike purposes.

Watt hours is a measure of how much energy a battery holds. As an example, a 13s, 4p battery is said to be a 48v battery, but really it is a 54.6v battery when fully charged to 4.2 v/cell, and a 45.5v battery when discharged to 3.5 v/cell. Voltage declining during use complicates the math, so we simplify by calling the battery a 48v battery. Volts times Amps = Watts. Volts x Amps = Watts. OK. Watts are the units of power, power causes speed, but not distance. To get distance we need energy, energy stored in the battery. Watt hours, Wh, is a measure of energy storage. As an example, a 13s, 4p battery of 48v and 14 Ah capacity, has 48v x 14 Ah = 672 Wh of energy storage. Now were getting somewhere, Wh are a valuable number for calculating things like range on a charge. Example: during 464 miles of riding, my average Watts of battery use were 163W.

Alright, if I divide my battery energy storage by my power average then I should get my range, right? Example: 672 Wh of energy divided by 163 W of power = hours of riding. 672 Wh / 163 W = 4.1 hours of riding. Woah, not so fast. Reason is that I can't use 100% of my battery energy and have long life from my expensive battery. To have long battery life my operating protocol is to use only about 40% of my battery energy. That is, I never charge to 100% which would be 54.6v, but only charge to 52.0v. Discharge never goes below 45.5v. Hmmm, I'm only using about 40% of my rated battery energy storage. So, 672 Wh / 163 W * 0.40 = 1.65 hours of riding. Now for distance: multiply hours of riding times average speed = distance. 1.65 h x 12.4 mph = 20.4 miles of range. About range, riding slower uses less power and thus increases range. For the 464 miles my actual speed average was about 11.0 mph and calculated average range was 22.6 miles.

So a battery that might give 50 miles range, going from full charge to low voltage cutoff ... is only used for 20 miles more or less? Yes, to extend battery life. If I want to go farther, and often do, I just ride slower or take a second battery.

Cost: My gas bike uses a 33cc Subaru Robin four stroke engine, it costs about 1.7 cents a mile to operate, for gas. The ebike costs only 0.10 cents per mile for electricity. But the battery cost is about 8 cents per mile, if the battery lasts 5 years. Batteries can be considered a consumable item, like gasoline, and an expensive consumable at that. Long battery life for this reason important.

Batteries have a lot of variables and there are many different ways of looking at them and their use.

I hope this helps. Keep us posted on what you get, what you do and how it works out.

Mike

how fast does your suburu robin go???? Thanks

 

[bike4life]

Here's a battery to avoid on ebay. 48V20AH 13s-4P, for 1000W ebike, even cheaper than the OP's pack at $140.
https://www.ebay.com/itm/Ebike-Battery-48V-20ah-Lithium-ion-Battery-with-Charger-for-1000w-Electric-Bike/274341708971?hash=item3fe00a44ab:g:sCAAAOSwCKlenHM8

It features four 5AH cells in parallel to get that 20AH. That must be those double secret cells used by the Chinese moon shuttles, as commercial cells doesn't even exceed 4AH.

I guess it's typical ebay liars at work. Is that a scam?

It might work for a while. It should be capable of 20A which is 4A per cell, and that is 1000W. It will have a short life though, relative to quality cells. Maybe 200 cycles before it's half gone.

Best to get a battery made with name brand cells with a known type. There are high capacity and low capacity Samsungs, so you have to know which type. If you can't do that, there are some decent chinese cells, but I dunno what they are.

HEY THATS MY BATTERY PACK!!!!!!!!! Its the same model, the blue shrink rap and yellow sticker logo thing on the side..... It seems to drop range and charge pretty fast......