Hypothetical: I want to Build a LifePo4 battery- But How?

[The Mighty Volt]

Okay,

Suppose I get sick of the sheer awkwardness of my Cammy-CC batteries and decided to build a more reliable battery with superior capacity and superior voltage, how would I go about doing it and what skills would I need?

What batteries would I use, where would I source them and how much should I pay for them?

How do I connect them?

How do I insulate them?

What shape should I arrange them in?

How do I connect a BMS and output wires?

All suggestions welcome.

This, for the time being, is a strictly hypothetical, I am not going to try anything yet. I just want to see if it could be done and if so, how and for how much cost.

Thanks.

 

[deardancer3]

As a stake in the ground, consider using Headway screwtop cells, with highly flexible 8-10 gauge interconnect wire, then you can build the shape you want and be able to physically reconfigure later.

Shape depends on your ebikes profile. A one cell thick square plane woluld be nice, as I am weary of an ebike that is too wide from huge battery cubes; carry it beside the ebike and where one pannier would go.

There is some write-ups here on headway insulation, think it was talking about Battery condominiums or condums or something.

d

 

[dogman dan]

I'd say get the headways too, and read all about it in the headway pack builders thread. Perhaps the Fetcher Goodrum bms, or some other proven one likes pings, depending on the discharge amps you need.

Cellman has some intersting stuff too though. 20 ah a123 pouch cells are sounding real nice.

 

[The Mighty Volt]

I'd say get the headways too, and read all about it in the headway pack builders thread. Perhaps the Fetcher Goodrum bms, or some other proven one likes pings, depending on the discharge amps you need.

Cellman has some intersting stuff too though. 20 ah a123 pouch cells are sounding real nice.

Dogman, do you think it is feasible for me to self-educate myself and go and build a really powerful battery that gives almost motorised performance?

I know its a bit like asking "how long is a piece of string"....I was hoping for something like 72v 40Ah.

What sort of budget would I be looking at?

Cheers.

 

[The Mighty Volt]

Okay I just did some very quick reading and realised the absolute insanity of what I am attempting..... people are talking $5000 for a battery of those specs?

 

[Lyen]

Okay I just did some very quick reading and realised the absolute insanity of what I am attempting..... people are talking $5000 for a battery of those specs?

I'd highly recommend you to build your 72V 40A pack with smaller modular packs. Lets say 4 x 36V 20A packs and configure them as 2S2P (2 series & 2 parallel). This way, your have more flexibility to arrange them. Also, you can select power on demand without carrying all the weight all the time. I know, because I have 2 48V 40AH packs, and multiple 48V & 36V smaller packs. My estimate for the 72V 40A weight should be somewhere between 85-92 lbs depending if your are using 18650 type, A123 type, or pouches.

 

[velowatt]

Well, it's not insane, just a pretty big battery. Headway cells provide around 3.6V each at 10 Ah, so a series string of 20 would give 72V, and 4 of these in parallel would give 72V 10Ah. They cost around 17-22 USD per cell, I think, so you are looking at around 1500 dollars US. This would be fairly heavy and bulky, but would give your desired capacity. What would you use it for? Seems a bit capacious for an ebike? E-motorcycle maybe?

Building as "modules" is a very good idea, as well!

 

[velowatt]

Oop. I meant 72V 40 Ah. Typo.

 

[ahambone]

I've built a 72v 50Ahr pack from Headways. I go into some detail about it over in the Headway Pack Builder's thread around page 12:

http://endless-sphere.com/forums/viewtopic.php?f=14&t=12320&start=165.

That thread is a great thread to read of you are considering building a pack like this. What I ended up with was fairly different and much easier than I was originally expecting and designing for. The cost for a 72vx50ahr pack was just at about $2500 once you factor in the wire, copper pieces and plastic mounting frames used in the pack.

Here's a link to a hi-res of photo of the pack mostly assembled:

http://flashbone.serveblog.net/cabrioletPictures/20091103-batteryPackPictures/IMG_2555.JPG

And completely assembled and being tested in a car:

http://flashbone.serveblog.net/cabrioletPictures/20091130-Test-Setup/IMG_2732.jpg

This is a fairly awesome battery pack. This one pack, according to calculations, will take my EV 16 miles (at speeds <= 45 mph). I haven't put more than 10 miles on a charge yet and won't until I get my Hi-V Cycle Analyst installed so I can monitor amp-hours consumed from the pack. I've put about 10 cycles on the pack so far and maybe 50 EV miles. If the budget doesn't scare you I can certainly recommend this as a pack that can dish out the amps. It barely warms up after a sustained load of 200 amps with peaks of up to 300 amps. I'll post performance data when I get enough data logging equipment in place.

Cheers,
--Adam

 

[Bazaki]

Interessting and nice pack, do you have a BMS that can handle 300A peak ? Or without BMS ?

 

[The Mighty Volt]

Well, it's not insane, just a pretty big battery. Headway cells provide around 3.6V each at 10 Ah, so a series string of 20 would give 72V, and 4 of these in parallel would give 72V 10Ah. They cost around 17-22 USD per cell, I think, so you are looking at around 1500 dollars US. This would be fairly heavy and bulky, but would give your desired capacity. What would you use it for? Seems a bit capacious for an ebike? E-motorcycle maybe?

Building as "modules" is a very good idea, as well!

I want something that hauls ass, I guess. 8)

Maybe 72v is too high, I could live with 66v instead.

I just want something that can, in short bursts, give me vehicular performance.

I think I have been watching too many steveo and doctorbass videos.

 

[Lyen]

Well, it's not insane, just a pretty big battery. Headway cells provide around 3.6V each at 10 Ah, so a series string of 20 would give 72V, and 4 of these in parallel would give 72V 10Ah. They cost around 17-22 USD per cell, I think, so you are looking at around 1500 dollars US. This would be fairly heavy and bulky, but would give your desired capacity. What would you use it for? Seems a bit capacious for an ebike? E-motorcycle maybe?

Building as "modules" is a very good idea, as well!

I want something that hauls ass, I guess. 8)

Maybe 72v is too high, I could live with 66v instead.

I just want something that can, in short bursts, give me vehicular performance.

I think I have been watching too many steveo and doctorbass videos.

Can you please define your vehicular performance? At what speed? Is it for commute or just for fun? There are different optimizations between the two.

 

[The Mighty Volt]

Today, I went out riding and the wind was a constant bitch, pardon my term. It just kept sapping my top speed and forcing me to draw more Ah than I was comfortable with. With my Aoetma hub, the motor likes to get into its groove. The constant gusting of wind and the intermittent hills is hell on a motor that lacks torque and a battery with only 20Ah.

Basically, I want something that can feed a motor and combat the elements which kill speed, namely crap road surface {you guys have it made in the States/Canda, it froze here over winter and the roads are destroyed. I am combating grit, potholes, broken shit surfaces etc} gusting winds, intermittent hills, intersections etc.

One example of something which killed me today.......there is a beautiful stretch of bicycle lane which links two rural townlands along a major route. However, as part of the deal during development, the farms all have access points from their fields onto the road, via the bike lane. No sooner have I built up speed than I am slowing down in anticipation of the gates which lead onto the bike lane from the fields. It kills the speed, and immediately puts the Aetoma back under stress.

At the moment, on these surfaces and with these damned hills, the Aetoma is acting as a glorified power-assist {dont get me wrong, its a grand motor, and I would be lost without it}.
Torque is a major consideration. More torque= less grief.

 

[Lyen]

Today, I went out riding and the wind was a constant bitch, pardon my term. It just kept sapping my top speed and forcing me to draw more Ah than I was comfortable with. With my Aoetma hub, the motor likes to get into its groove. The constant gusting of wind and the intermittent hills is hell on a motor that lacks torque and a battery with only 20Ah.

Basically, I want something that can feed a motor and combat the elements which kill speed, namely crap road surface {you guys have it made in the States/Canda, it froze here over winter and the roads are destroyed. I am combating grit, potholes, broken shit surfaces etc} gusting winds, intermittent hills, intersections etc.

One example of something which killed me today.......there is a beautiful stretch of bicycle lane which links two rural townlands along a major route. However, as part of the deal during development, the farms all have access points from their fields onto the road, via the bike lane. No sooner have I built up speed than I am slowing down in anticipation of the gates which lead onto the bike lane from the fields. It kills the speed, and immediately puts the Aetoma back under stress.

At the moment, on these surfaces and with these damned hills, the Aetoma is acting as a glorified power-assist {dont get me wrong, its a grand motor, and I would be lost without it}.
Torque is a major consideration. More torque= less grief.

Yes, torque and high voltage are your keys in this case. You need a very high power controller. An Infineon 18FETs or above would be ideal. You also need a front suspension only bike since you need a 100 pounds capable strong rear rack to mount at the rear. I'd suggest to also get a big metal tools case to put your cammy cells inside.

 

[dogman dan]

Backtracking a bit on your other threads, Mighty Volt, I see you have two cammy batteries, one 48v and one 36v. Unfortunately better performance than you have now will be hard to get without replacing everything. The aotema motor has no hall sensors, so upgrading the controller is harder to do. Most of the 72v controllers you can buy off the shelf are sensored. So getting real motorcycle performance is going to take a lot of money, not just for battery but also for a stronger motor, like a clyte 5304 or 5303. Then high discharge batteries to go with it, and a bike capable of carrying it all. $3,000 US at least, if not more. Ouch!

But there is some hope, though, for some significant performance improvement without spending quite so much. If it's just better response at lower speeds you crave, then a 9 continent motor may do it for you, and I think for sure a BMC 600 watt would. At 48v either of those motors should not overstress your 48v v power battery too much. Sell off the 36v battery with the aotema motor to someone else. You won't get much of your money back, but $400 or so towards a new motor will help. A good 24v battery series connected with the 48v battery, a 9c motor and 72v controller, should put you in the torque and speed area you want. If you don't want so much speed as torque, just get the BMC and use the 48v battery till it dies.

I think maybe you need to explore some different motors first, since overvolting the aotema is hard to do with most 72v controllers using sensors. For now, you could buy just the 9c motor, and run it on your current controller. That will improve your tourqe for about $200 plus shipping.

BTW, you must have some good steep grades on your roads, most find an aotema at 48v quite sufficient. But it will climb 7% a lot slower than a 9 continent 9x7.

 

[themotorman]

Okay,

Suppose I get sick of the sheer awkwardness of my Cammy-CC batteries and decided to build a more reliable battery with superior capacity and superior voltage, how would I go about doing it and what skills would I need?

What batteries would I use, where would I source them and how much should I pay for them?

How do I connect them?

How do I insulate them?

What shape should I arrange them in?

How do I connect a BMS and output wires?

All suggestions welcome.

I would wait until the end of this year, by then some good BMS's and batteries might be available.. Having had experience with LiFePO4 packs I would be very careful before investing. typical cost is around $1.00 per Ahr for LiFePO4 but the BMS ,you MUST HAVE to get a reasonable use, might cost as much if not more than the cells. The battery sources are IMHO marginal at best and flaky at worst. The BMS sources are about the same. I think that it is a very difficult challenge and will be met , probably by a chip manufacturer who sees the potential in a large volume of chips.. Not easy for the home builder or small developer to compete as chip foundry costs are extremely high.
I suggest you look at NiMH if you do not need the energy density, they are much easier to live with..

This, for the time being, is a strictly hypothetical, I am not going to try anything yet. I just want to see if it could be done and if so, how and for how much cost.

Thanks.

 

[The Mighty Volt]

Anyways, I have now managed to sell one of my duct-tape packs. Assembling the headways seems handy enough, not really a major job, but who here sells a good BMS?? And how to I assemble it!! Thanks.

 

[wookey]

This is a fine BMS, as designed here on this board: http://www.rechargeablelithiumpower.com/oscommerce2/catalog/index.php
You can buy them assembled (or at leastyou could - not sure there are any left in stock at the moment)

 

[biohazardman]

I have seen and hefted the Headway cells they are big and heavy. Having used the Foxpower prismatic cells, I know about heft and sizes as well as the performance hit one takes with the lower cost LifePo4 cells. They werq fine but do not come near the performance of a123s or Lipo. The a123s are less bulky and I believe lighter also per AH and will give one many more amps when needed. The only downside I see is one needs four times as many cells for a similar pack. Not all a downside either as it gives one flexibility in the shape and size of the pack that the Prismatic and Headway cells cannot match. ES posts provide everything you need to know and one can use the same BMS as already mentioned. My only other suggestion would be Lipo and much information is provide here on the ES about that choice also. But let’s not forget the Headway packs either as they have their place for some. Oh, can you tell I am running a123 packs? ;^) I wish you luck in your endeavor

a123 packs http://endless-sphere.com/forums/viewtopic.php?f=14&t=2498

Lipo packs http://endless-sphere.com/forums/viewtopic.php?f=14&t=9170

Headway packs http://endless-sphere.com/forums/viewtopic.php?f=14&t=12320

BMS information http://endless-sphere.com/forums/viewtopic.php?f=14&t=5416