Even More Batteries!!

[deacon]

I used to shoot uncle sugar's .30 carbine back in the day. Seems to me the can was about four inchs wide about ten inches long and maybe six inches deep. that is just my weird memory so I'm not sure about it. That was about fifty years ago.

I am a believer in recycling stuff. I mean honest to god I live about two miles from the home depot, but I would rather figure out what will work from my stash of old parts. I love to recycle stuff.

At the moment I have a homemade trike sitting in my shop. it has a twenty inch front wheel in a real fork. The frame was a girly bike so I removed the top rail running from the front head piece to the seat post holder. I was planing to make a drift cycle but I put that on hold till figure out how to propel it when the motor fails. There are no pedals or rear sprocket.

Anyway I'm really looking forward to this. I found some 12gauge single strand wire. I found about two feet, I probably will use it. I always use a household electrical extension cord as a connector. Female end on the battery pack and male end on the controller. I also have the male end on my charger so that I can plug it into the pack. I expect to have some kinks to work out but it doesn't seem much different from making a NIMH pack except I'm going to try not to burn this one up.

 

[cannonball2]

Use a stiff wire for the cell connectors. Try Lungcookies hammered 12/2 method. The wire basically holds the cell pack together after soldering. You must be thinking backwards on wire gauges 12ga is pretty large and probably overkill but I woudnt use less. Funny thing the phase wires on the hub motors are tiny in comparison. I would group my 3 cell groups by voltage if you are not going to break them down to individual cells. Put the better ones together and mark the lesser ones so you can check them first if you begin to have cell failures. Thats the cool thing about modular, I can read/balance/replace a 12cell 7.2v brick individually. Remember the battery is basically only going to be as good as the weakest cells. I over bought expecting to cull a few. If you have any below 3.0v thats not too good, especially if you have no way to charge/load test cells or groups. I found that cells in the 2.5v rest range usually didnt load test well even if the charge voltage looked good. Do this right and you will have a good pack, otherwise you wont be happy.

Thats a cool bike Lungcookie! I see you went the same route on the big front chain ring so you can pedal upwards to 30mph.

 

[deacon]

I will give the attachment of the two three packs together a 12gauge stiffy, but I think the end attachments need to be flexible. I have never had much luck with stiff wires on sla packs they tend to break off because they can't flex with the vibration of the bike.

My batteries should be here today or tomorrow.

 

[cannonball2]

Your right the solid wires just connect the cell groups. The groups are easy to build and dont require taping together to solder if you build a little jig or hot glue them together like Lungcookie did.

 

[Lungcookie]

deacon, pretty close, its 10x7x3.5, fit my "48v" 10ah LifePo4 almost like it was made for it. Got that one from my grampa in the way back I kinda felt bad cutting a hole in it, now it has a new life.
Actually can get 6 more cells in there, that would be 54 cells of these Lifepo4. They are like a long C cell battery just a bit larger than the cells you and CB2 are running.

CB2
Yeah I like to pedal at 20mph this gearing works good up to about 25mph.16/52 gears
Its fine in the flat land and I only run under 300w cruising, 10ah lasts me longer than I want to be on the bike. I don't have much in the way of hills where I ride so it work pretty good.

 

[deacon]

Those hills devour the AMPs that's for sure. I test my batteries on a six mile round trip to the lake. It has three killer hills in each direction. It's a good way to test drain them without riding ten miles.

On the size of the ammo boxes. I loaded a few onto a helo in Thailand in my time. They can be pretty darn heavy when filled with belts.

I went to dollar tree this morning and they had plastic pencil holders on a table by the door. They were screaming to me 'buy me, buy me,' So I got one that is about 8" by 5" by 3" so I hope I will have more than enough room, so I can pad the bottom and sides. It has a top so I would like to be able to remove the top and then get inside to put a meter on the stings of six to get a voltage read on them.

CB if I get this built, I will be buying more cells for sure before they disappear from Ebay. It looks like the BMS is for guys like my son in law who wants to plug and play all the way. I love to tinker. Wife says I ride my trike and hour then come home and work on it two hours at least. She is right of course.

Ps I have a lot of stuff left from my nimh fiasco. One of the things is some paper tape I used to hold the batteries while assembly. I expect I will use that to hold the three packs together for assembly.

 

[deacon]

Well my hats off to you guys who made this work. I just ruined them all. It's back to the bullet proof SLA for me. I am riding a trike so I have less of a weight issue than a two wheeler.

I have no idea what I did but when I got it built it had the power of a flat SLA but the weight was good. After I ran them a mile or so and had to pedal repeatedly, I began to experiment with them. Me with soldering iron was the death of the batteries. I did learn that I like the weight. If I ever buy one it will be a 48v 20ah at least, I learned that for a hundred bucks rather than learning it for four hundred so it wasn't a total loss.

 

[silverbear]

Ah man, I'm sorry to hear that. You sure they're cooked?
SB

 

[cannonball2]

Post some pics deacon maybe we can see a mistake or something. Soldering the cells doesnt hurt them unless maybe your on the cell too long. Did you read the cells voltage before you started assembly?. Did you install inter cell connectors?

 

[Lungcookie]

That sucks!
Pics or new thread maybe someone can help, I saved and improved my battery with help from this great forum. I had 1 cell that was killing off the rest. Maybe you have a bad cell/cells.

 

[cannonball2]

Update on the home built batteries. The original pack is on the way out. I expected this. it was built from cells that were purchased for the least $$ as an experiment. It still charges and works but the range is diminishing.
Conversely the modular battery is an excellent pack. It has been sitting quite a while as I have been running my purchased 48v pack and the R/C lipos. I noted the rest voltage when I set it idle and after about a month it was only a few points of a volt diminished. I put it into the MP2 bike and did a 5mi high speed run around the area. I expected the voltage to drop like a rock because I was often pulling the controllers limit and it hadn't been charged since set up. When I got home I let the pack stabilize and it had only dropped 2v.
Point is if building an 18650 pack buy cells from an honest seller that will certify the voltage. All these cells came in with rest voltages at 4v or better. Any cell that is under 3.6/3.7v is suspect.
Great cells make a great pack!

 

[cannonball2]

So after grinding on about what I great pack I have(turns out it really is). I figured since its due for a charge I would break out the R/C charger and charge each 7.4v brick individually to get a basic balance charge. Plugged in the volt meter to get a reading and what!? Only voltage in the 30s! Read the bricks and the last two read 0v! After a bunch of fooling around I figured I had toasted the pack. Since the voltage was in the low 30s I plugged in my 36v charger to see what happed. After a short time the charger shut off and the voltage read in the mid 40s!(too quick to have done any charging)
So the seller of the cells had kindly sent me replacement cells for the culls I had plus a few extra. These were the same AH but a different brand than the bulk which were Samsung. So I put them all in the last two cells.
So I guess I had a brain fade yesterday before tearing around the hood. I started with the pack at 47v and came in just under 45. Fine for a 48v pack. Problem is this is a 55.5v pack(63v) charged.
I am thinking the odd cells were protected and finally shut out? The voltage must have later dropped below the protection limit? Does raising the voltage open the protection circuit?
The pack is merrily charging, currently at 60v(in the middle of my concrete garage floor for sure!) and seems normal.

What yall think?

 

[snellemin]

Just keep an eye on it and check the temps of the cells during charge. It's cool than you are getting new cells by the seller.

I check for Ah used rather than voltage when I ride. This way I know exactly how much range I have left. The voltage isn't stable enough to keep that as a reference on capacity.

 

[cannonball2]

OK nothing is up with the pack. Sadly my trusty Fluke meter is giving up. Borrowed a neighbors VOM and everything reads properly. Would have never guessed the meter could behave so strangely.

Thanks for your reply Snellemin!