48v 30ah battery Best cell config? BMS? Controller?

[xl-frame]

Need to build a 48v battery that I will be using to convert a bike with 20" moped rims and a 48v 1500w hub motor. I'm looking more for range than speed (mostly flat where I live). Every day I need to ride continuously for at least 7-8 hours--but prefer up to 9-10 hours-- at 15-20mph. Although I also need a top speed of 30mph, at times. If my math is right, in order to accomplish this I need to build at least a 14s8p battery.

Better voltage and capacity recommendation for my needs? Which S and P Config?
Which 18650 cell will perform best?
Should I just use any standard 14s 30aH BMS?
Most sufficent wattage and max capacity of controller for battery and hub setup?

What else should I be considering in this build?

Any help would be much appreciated! Thx

 

[baltimorebiker]

I would recommend either getting a chevy volt 44v 45 ah module, and using a 12s hobby charger. This would cost around $800. The chevy volt battery is widely known as one of the highest quality, cost effective battery.

http://www.diyelectriccar.com/forums/showthread.php?p=379463#post379463

Or you can wait for sales on hobby king and build a battery. Best option right now seems to be Multistar LIPO. Sometimes you see great sales.
You can build a 44V 32 AH battery for $450 worth of raw LIPO. You can pair that with a Turnigy 200W charger for around $100. Make sure to get an XT90 balance board, along with XT 90 series harness. Probably cost around $650 total.
http://www.hobbyking.com/hobbyking/store/__66487__Multistar_High_Capacity_6S_16000mAh_Multi_Rotor_Lipo_Pack_AR_Warehouse_.html

Of course, you could buy a 48v 30 ah battery off Luna cycle, ebay, em3ev, etc for a lot more $$$$

Neither of these options have a BMS. I would stray away from BMS and rely more on good hobby chargers to save on cost, and increase realiability/longevity.

 

[titooon2014]

Hello,

Riding at 20 mph with my foldable bike (48V 13A limited), I get around 4h autonomy (80 miles) with my 13s9p (48V 26Ah) pack that uses 18650 LG MG1 (2900mAh).
I do pedal a bit, and it's mostly flat here.
In 48V I can reach 30 mph. Slowly but I get there (only 13A max).

I doubt you'll get 10 hours autonomy, even 7, with a 14s8p battery even using the latest 3500mAh cells.

I would consider a minimum of 40Ah to start with if you want to reach 10 hours.

If you can oversize a bit your pack and charge only @4.10V (about 90% full) per cell you will increase lifespan quite drastically.

13s BMS are common and cheap. G**gle is your friend

 

[TristanP]

Need to build a 48v battery that I will be using to convert a bike with 20" moped rims and a Leaf 48v 1500w 5T hub motor. [...] If my math is right, in order to accomplish this I need to build at least a 14s8p battery.

For a 48v battery you need a 13S config; 14S will make it a 52V pack. It is however something worthwhile to consider, as long as you bare in mind that the other parts of your setup should be compatible with that. (It will increase the capacity and likely decrease discharge rates and positively affect speed.) How much cells you need in parallel depends on the discharge characteristics of the used cells and the capacity. Notable is how it 's pretty much capacity vs discharge current.

Given the 1500w motor you probably will have some peaks of up to 25-30A or maybe even have a high discharge rate if you ever consider higher speeds than the earlier mentioned 15-20mph. For that a 5P setup of the Panasonic NCR18650B (3350mAh) will be sufficient, as it will perform well with a discharge rate of 6.7A per cell. The NCR18650PF (2900mAh) does well with a discharge rate of 10A, so in regards to that you only need 3 in parallel. With other cells you may find they perform much worse at such high discharge rates and affect the relative capacity badly, so it's advisable to use more in parallel. Also a high discharge rate may affect battery life negatively. (if you only drive 15mph continuously the average discharge rate will be relatively low though.)

In regards to price vs capacity the Samsung INR18650-29E (2900mAh) is cheaper than previous mentioned cells. Also at a 3C discharge rate (8.25A) it's relative capacity is still 92%. Then again you actually need a lot more cells to build your 48v/30Ah pack, which may make manufacturing the pack considerably more expensive.

Another factor to take into consideration is the influence of temperature on the relative capacity. When you use your e-bike in winter, with temperatures slightly above zero, their relative capacity will be a lot lower then at room temperature.

I'm not about to suggest you any cells, as doing your own research and comparing datasheets is actually real fun. I personally like the NCR18650B cells as they are really versatile for all kind of battery packs. I would buy them from NKON as they for sure sell genuine cells and are quite often the cheapest supplier of cells. (They ship internationally.)

In regards to building the pack I would keep in mind that the thing should be rigid and it's mechanical integrity should be guaranteed at all times. If you use nickel strips, please bare in mind the wrap around a cell is really fragile and you want to make precautions against shorting. Either by using a cell holder or by using those self adhesive isolators. Personally I also care about using good silicon wire and crimped connectors, which do met UL/TÜV standards. (And I totally advise against the Deans plug crap.) If you want to use tape for certain things, you better use kepton tape instead of regular tape.

Bonus: A nice tool for calculating how much energy you need to perform your cycle activities, is to be found here. Also please note that the correct unit for capacity of a battery is watt-hour. (And with a reason.) Ah is perfectly fine however for comparisons and makes head work a lot easier.

 

[dogman dan]

Well, you are going to need 14s. that's the highest voltage 48v you can conveniently use, easily get a bms for, etc. 14s bms not hard to find even though lots of 48v packs now are 13s.

30ah is a lot of battery,, assuming you discharge conservatively and or some of the cells put out less than spec, still 25 ah usable, so you will have 1250 wh there to use. At 20 mph average,, assuming you pedal hard the whole time, you can get down near 20 wh/mi. Including some bursts where you use 40 wh/mi, I still think you can hit that number for an average. That's 62 miles, taking 3 hours traveling at 20 mph.

For most, that's a lot of range, but no way 10 hours of continuous use without a charge. you will need a fast charger,, or rather, as fast as you can get away with plugging in someplace. One solution will be to have several batteries, so you can plug in two chargers.

Two 48v 20 ah, and two satiator chargers ( 350w each) is the setup I have always wanted for long range rides. I can't pedal hard, so I tend to hit 25 wh/mi. That would give me 70 mile range, and could get 700 wh more in a one hour stop if I find a plug.

You'd have to carry 90 ah to have 9 hours riding without a recharge, or battery swap. If this is for a pedicab or deliveries, you need multiple batteries, with two in the shop charging at all times.

48v 30 amps controller will get you the wattage you need for the bursts of speed. A huge motor still runs plenty efficient when you are traveling sub 20 mph. So no problem with that. But if your ride is lots of stop and go city riding, a geared motor that goes closer to 25 mph top speed will be more efficient. For one thing, it can coast. But mostly it will be more efficient in the first 10 feet leaving stop signs.

I think for efficiency,, you might re think the whole thing, unless this is for a big heavy cargo hauler.

 

[xl-frame]

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[xl-frame]

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[999zip999]

There are much better cells out there I would go for a higher amp rating as I cut that advertised amp rating in half for daily use. There 20amp cells out there. Headroom long lasting.

 

[dogman dan]

I'm no expert on building batteries. But for a 30 amps controller, you need a big pack, as I said before. Think in terms of more than 20 ah for your earlier stated needs.

I'm confused why you need a controller, when the leaf kit comes with one,, but spares are always a good thing,

I'm still curious what you are doing, that you need 8-10 hours of use out of it. I think you need at least 3 20 ah packs for that kind of time, with two of them charging most of the day.