Battery Idea please give feedback

Tokingit

1 µW
Joined
Aug 18, 2024
Messages
1
Location
Sydney
Hi I was thinking of using 4 of these IMG_0439.jpeg
Simultaneously connected in series and parallel in a 4s4p configuration
IMG_0438.png

Those are the specs so I'm looking at a combined 86.4v 12000mAh .

Is my maths correct?
Also would this be okay to power a e-bike at 72v? What drew me to this was the minimal form factor of the batteries which can be very discretely mounted additional bonus is I most likely should be able to directly connect the battery using a hailong style battery mount terminal. Looking at less than 2kg if the above specs are to be trusted .

I understand that main difficulties may come from charging or trying to charge on bicycle , but I plan on always removing all 4 batteries and just charging them individually off bike and that would be how I charge them . Charge to full after every ride. Easy it's not hard

Any feedback and am I missing anything?
I feel I may be missing something because why hasn't anybody done this before but anyways thanks
 
21.6/ 6 = 3.6V 6s x 4 = 24s
I believe that the 21.6V is nominal voltage so it could well exceed the voltage limits of many 72V controllers. 24s fully charged is 100.8V.
340 g x 4 =1360g x 4 = 5.440 kg
Later floyd
 
What floydr understands, but didn't explicitly say, is that you can take 4 of those packs and arrange them in series for 86.4 volts nominal and 3 amp-hours, OR you can arrange them in parallel for 21.6 volts nominal and 12 amp-hours. You can't do both, unless it's 2 in series and 2 in parallel for 43.2V nominal and 6 amp-hours.

I've used those Dyson vacuum cleaner batteries before, but only to make portable powered speakers. They only contain 6 cells of 18650 format, so you would need a lot of them to power a bike. Putting four of them in series would create a risk of destroying their BMSes and rendering them useless.
 
"connected in series and parallel in a 4s4p configuration" ...
16 batteries at $25-$30 each = $400 to $480 plus wiring, connectors, and housing for 4s4p

"I plan on always removing all 4 batteries and just charging them individually off bike"
Did you mean to say all four of the 4p batteries charging each to 21.6V and then connecting them together (86.4V).

"Those are the specs so I'm looking at a combined 86.4v 12000mAh"
Wouldn't you want closer to 20Ah than only 12Ah.

Whatever you decide DON'T buy those cheap Chinese shrink wrap flat (rectanguar) batteries falsely advertised at a higher amp capacity than actual, e.g. ...
Cylindrical 18650 21700 4s4p Li-ion Battery 10400mah 14.8v 20000mah Lipo Battery Pack - Buy 14.8v 20000mah Lipo Battery Pack,Icr18650 4s4p Li-ion Battery 10400mah 14.8v,Lipo Battery 4s 14.8v 22000mah Product on Alibaba.com ... even so still at least $300 if it is any good to give you many charge cycle for good cycle life.

You'd be better off buying a 4s4p pack that's already wired with one charge/discharge connector. Whenever you see the total battery capacity (14000mAh) listed in mAh instead of 14Ah beware as the actual battery use capacity is lower. Also you don't know what kind/quality of a BMS, and no warranty (Buyer Beware).
 
I've used those Dyson vacuum cleaner batteries before, but only to make portable powered speakers. They only contain 6 cells of 18650 format, so you would need a lot of them to power a bike. Putting four of them in series would create a risk of destroying their BMSes and rendering them useless.
Worse than useless. Sometimes dangerous,

When you put batteries in series, you need to make sure that the BMS in each battery can hold off the full voltage of the entire stack. in case it switches off. For four DC16's in series, that is 24S which is about 100 volts at full charge. It's highly unlikely Dyson or any clone battery makers used 100V transistors into a 21.6V BMS.

It's not a theoretical EE exercise either. It's a real limitation. There was a poster on this forum that posted about putting two 48V packs in series. He must have switched one off. That;s 110 volts across the BMS and it popped. Unfortunately it shorted out the BMS, so he lost all protection. He posted later asking why the battery caught fire

Your DC16's don't have switches, but a BMS can turn off for overcurremt, low voltage etc, All you need is one of them to do so. and it's likelyto be damaged.




.
 
Worse than useless. Sometimes dangerous,
Especially if the user is a newbie with limited funds unable to afford a 1st rate quality (expensive) battery and NOT abuse it ,,,
This 16s4p (64.8 nominal volts) with A-Grade 21700 cells is American Made ($1,684), and yet they fail to tell you the name brand and model of the 64 cells Even though American Assembled it is listed as 20000mAh capacity. 4p at 20000mAh implies each cell is 5000mAh (e.g. 21700 Samsung 50E, or 50S), but there is no guarantee when a manufacturer battery label lists capacity in mAh as their way of falsified figuring so as to inflate battery capacity.

It's tempting to buy a cheap 16s4p from Alibaba, AliExpress, when it costs less than $300. This cheap Chinese ebike battery (from Amazon - $319) with nominal voltage listed at 60v (16s4p). Also its Chinese label listing of 25,000mAh capacity is a red flag as its Chinese marketing method for inflated capacity not actual capacity. It's actual capacity may be closer to 10Ah using no brand name chinese cells of questionable quality. Its likely actual cell rating (no data sheet of proof), if 21700 (IF 5000mAh would have an actual 4p capacity of 20Ah and more likely closer to 12Ah ... https://www.amazon.com/Mdxtog-Battery-Motorcycle-Charger-Electric/dp/B0D1VD4FMD?th=1 ... 25000mAh divided by 4p gives a cell rating of 6,250mAh. Whoever believes that is more likely a noob, newbie, newb besides being an OPTIMIST.

... i wouldn't trust that dinky cheap little charger. Wouldn't be surprised if Amazon removed this Chinese battery (with it's inflated capacity rating) ... there are no reviews (newbies are finally wising-up).
Although when on a tight budget some noobs will still convince themselves ... "What sweet a deal"! ... and then when its cycle life is short-lived and find out there's no warranty they will (of course) fault the seller instead of their own lack of due diligence.
1730590332901.png
 
Last edited:
Back
Top