So who has maxe their own battery packs?

[Pine_marten]

I have been studying You Tube videos on pack building and have a vague overview on the basic points. Paying $900 for a high capacity pack seems kind of outrageous and it is obviously where a good bit of the profit comes from for ebike kit suppliers. IIRC, my 48v, 20 ah pack with 21700 cells cost about $700 .
Were I to attempt it, i would avoid lipo cells and go with lithium iron ones. But more study and research is definately in order. In this case it is the knowing and not the doing. I need to know a bit more.

 

[Pine_marten]

Where are the good suppliers for cells, cell holders and bms units? Seems that a good deal of the expertise in the ev field is on the West coast which is not surprising. While i'm sure there are tech savy folks here in fly-over country, they are hard to find.

 

[harryS]

The build vs buy decision for batteries is easy. You buy them if you only need one or two.

I've built a few packs. I spent several hundred dollars buying the welder, and cell test equipment and I don't even have good stuff.
I have built a 48V15AH battery in a Hailong case, using LG 21700 cells. I estimate about $450 for the cost of goods for a 20AH pack, which makes your $700 look pretty good, if they gave you real LG/Samsung cells.

Check out 18650batterystore.com for cell prices, and cell holders, but I would buy battery cases which use different holders. Buy the BMS from the same seller. There are so many crappy BMS being sold out of mailboxes in China. Most of the ones on amazon are crap.

And a lot of those youtube videos don't use good techniques.

 

[FrankR]

I leave this to the experts.

No way I would take this on. But kudos to those who can, safely.

 

[JES2020]

I leave this to the experts.

No way I would take this on. But kudos to those who can, safely.

Agree 100% . It's too dangerous an item just to save a couple of hundred bucks.
How much is your life worth?

 

[harryS]

There's a lot of people who have no knowledge of electricity, trying to build batteries by looking at pictures. The IKEA generation, Kaboom.

 

[wjbender]

I recently built a 7S2P pack that provides 4.7Ah of useable capacity. It fits in my seat bag and I can ride 26 miles on a charge. That is more than my typical ride. My total cost to build the pack was about $130 using Samsung 18650 25R cells. I use a balancing charger to charge and do not use a BMS. The low voltage cutoff and current limit is set in the bikes TSDZ2 controller. I also added an inline fuse between motor and battery. So far very pleased with the result.

 

[MWRider]

I recently built a 7S2P pack that provides 4.7Ah of useable capacity. It fits in my seat bag and I can ride 26 miles on a charge. That is more than my typical ride. My total cost to build the pack was about $130 using Samsung 18650 25R cells. I use a balancing charger to charge and do not use a BMS. The low voltage cutoff and current limit is set in the bikes TSDZ2 controller. I also added an inline fuse between motor and battery. So far very pleased with the result.

The fuse is a Really Good idea! I work on a lot of electric powered lifts, scrubbers, forklifts, etc. and quite a few of them have fuses. Those that do not, I have added fuses which saves the controllers and motors when batteries go low and operators do not have enough sense to stop.

 

[Pine_marten]

It is certainly doable without risking life and limb. I have a 10 year old Giant light weight single speed that would work well with a small battery like that. A rear hub drive with regen braking would be ideal on that bike.

 

[JES2020]

It is certainly doable without risking life and limb

There is always going to be a risk to life and limb. Even in the best of circumstances, eg Tesla fires, we see there is always a risk when dealing with high energy flammable chemistry.

 

[harryS]

It is certainly doable without risking life and limb. I have a 10 year old Giant light weight single speed that would work well with a small battery like that. A rear hub drive with regen braking would be ideal on that bike.

A hub capable of useful regen would likely be a huge deficit on that Giant, being heavier than a geared motor, and its internal magnets fighting you when coasting or pedaling w.o power. I realize that with an advanced controller, you can keep the hub powered so you won't feel any drag when coasting. How does that save battery power overall?

 

[harryS]

I recently built a 7S2P pack that provides 4.7Ah of useable capacity. It fits in my seat bag and I can ride 26 miles on a charge.

Di you program the TSDZ2 to run on 24V? I realize 7S is 29.4V at full charge. That's like a 100-120 watt-hour battery or 4-5WH/mile. Nice, My wife sometimes gets 5-6Wh/mile on her rides, but that's a hubmotor.

 

[Pine_marten]

A hub capable of useful regen would likely be a huge deficit on that Giant, being heavier than a geared motor, and its internal magnets fighting you when coasting or pedaling w.o power. I realize that with an advanced controller, you can keep the hub powered so you won't feel any drag when coasting. How does that save battery power overall?

No, the regen would be primarly for managing long downhill stretches.

 

[MWRider]

No, the regen would be primarly for managing long downhill stretches.

I am familiar with equipment sold with “regen”. It is pretty much a pipe dream with little effect on BSOC. IMHO, It is just a sales gimmick. If you do the “real math”, you will see what I mean. Nobody gives you real working values. My .02

 

[harryS]

Pine_Martin is, I believe, just looking to save his brakes on a long downhill stretch. I might have to drive 1000 miles to find a long downhill.

 

[AHicks]

I am familiar with equipment sold with “regen”. It is pretty much a pipe dream with little effect on BSOC. IMHO, It is just a sales gimmick. If you do the “real math”, you will see what I mean. Nobody gives you real working values. My .02

Normally I would agree with you, but there is one system where regen can be used much more effectively. Check out Grin's GMAC system.

Here's a hint - the system uses a geared hub motor that will have the armature turning 5 times faster than other regen set ups, making it 5 times as effective....

Nearly all other geared hub motors, and mid drives, all use a clutch to uncouple the motor for to allow coasting efficiently. The GMAC does not have this clutch, and relies on some pretty fancy electronics that allow a small amount of power to the motor when it's not being asked to brake.....

Point being, this "pipe dream" is based on reality.....

 

[MWRider]

Pine_Martin is, I believe, just looking to save his brakes on a long downhill stretch. I might have to drive 1000 miles to find a long downhill.

Thanks, I missed that. I can see the benefit in that.

 

[MWRider]

Normally I would agree with you, but there is one system where regen can be used much more effectively. Check out Grin's GMAC system.

Here's a hint - the system uses a geared hub motor that will have the armature turning 5 times faster than other regen set ups, making it 5 times as effective....

Nearly all other geared hub motors, and mid drives, all use a clutch to uncouple the motor for to allow coasting efficiently. The GMAC does not have this clutch, and relies on some pretty fancy electronics that allow a small amount of power to the motor when it's not being asked to brake.....

Point being, this "pipe dream" is based on reality.....

That is a very Good point. Is there any kind of wet brake available for Ebikes or is that something one would have to fabricate? That is something for me to think about. We do have some long hills in southern WI.