Henry111's free tech support thread

[r3volved]

nice job
Thanks for posting your success too and not leaving everyone hanging.

If only all problems were that easy to fix

 

[dnmun]

it just dawned on me that these batteries in a case with the switch could be retrofitted with a precharge resistor to charge up the input caps before the switch is turned on and that would stop the erosion of the contacts in the switch so they would last longer.

the big blue wire coming up to that spot is the B+ of the battery. the reason the charger lead goes there is so that the battery can charge while the switch is off.

if you can find a convenient spot to drill a hole for a push button 'momentary on' switch next to the key switch then it could be installed there and the momentary switch would connect to the same spot as the charger lead, at B+ there on the back of the switch.

then run the resistor from the other side of the momentary switch over to the red wire terminal of the key switch so that when you pushed in the momentary switch it would precharge the caps on the input, and then you could turn the key switch on. so no spark at the key switch.

all the parts would be inside and none would be hot until the momentary switch was depressed. it could even be an on/off switch if you were capable of remembering to turn it off later. so a momentary push button is best solution imo.

 

[Henry111]

it just dawned on me that these batteries in a case with the switch could be retrofitted with a precharge resistor to charge up the input caps before the switch is turned on and that would stop the erosion of the contacts in the switch so they would last longer.

the big blue wire coming up to that spot is the B+ of the battery. the reason the charger lead goes there is so that the battery can charge while the switch is off.

if you can find a convenient spot to drill a hole for a push button 'momentary on' switch next to the key switch then it could be installed there and the momentary switch would connect to the same spot as the charger lead, at B+ there on the back of the switch.

then run the resistor from the other side of the momentary switch over to the red wire terminal of the key switch so that when you pushed in the momentary switch it would precharge the caps on the input, and then you could turn the key switch on. so no spark at the key switch.

all the parts would be inside and none would be hot until the momentary switch was depressed. it could even be an on/off switch if you were capable of remembering to turn it off later. so a momentary push button is best solution imo.

Thanks for info dnmun. These batteries go on bikes that I convert for customers. So I don't want to complicate life for them. However, if I am ever in a tinkering mood I'll try it.
Thanks again.
Henry

 

[Henry111]

Nice when you can positively identify the problem (and fix it).

I'm glad I had a second similar battery on which to verify where that disconnected wire goes.
But If I had not I'm sure dynum would have advised me.

 

[Henry111]

Would a 36V/10Ah Lithium battery and 20am controller be suitable for driving a bike with an 800 watt motor?
What would happen to the performance compared to a 36V/14Ah and 26am controller?

 

[bowlofsalad]

Would a 36V/10Ah Lithium battery and 20am controller be suitable for driving a bike with an 800 watt motor?
What would happen to the performance compared to a 36V/14Ah and 26am controller?

http://www.ebikes.ca/tools/simulator.html This tool might help you understand the answer to some of your questions.

The idea that you might need to understand is C rating. C rating is a batteries capacity in watt hours multiplied by a number to state it's continual output without harming the cells of that particular battery pack. Lets pretend, whatever battery pack you have in mind, has a C rating of 1. Then, we have it's capacity, 36v times 10ah = 360 watt hours (volts times amps equals watts). So, to find a packs continual rating its C x wh, or 1 x 360, which is 360 watts. If you were to draw 20 amps at 36 volts, that would be much higher than this theoretical power packs C rating.

Rather than just telling you the answer, can you tell me the minimum C rating needed for your 36v 14ah pack if you wanted to draw 26 amps at 36v?

 

[dogman dan]

For a typical 20amps controller, it's typically actually 22 amps. 36v 10 ah can be a bit on the small side for a 20 amps controller, but it all depends on the quality of the cells used.

Typical cheaper cells found in ebay batteries, or similarly priced bargains, they are rated for 2c but don't like it much. They really prefer 1c. ( for 10 ah, 1c is 10 amps) 14 ah pack with 20 amps controller would be a better setup, if your use will be hard.

What's hard use? Amp spikes when you start up, and long steep hills. So a weaker 10 ah pack may be fine for a ride that's flat, few stops, and you don't weigh 250 pounds or more. Cruising at 20 mph ish, you will be using about 14-16 amps. So it's at least under 2c cruising.

But if you will be riding trails, or even if you ride in the city with stops every block, then you want a better c rate, or a larger pack.

Now take the 14 ah pack. At 1c, it's doing about the rate that will let you cruise at 20-25 mph. So even with the 26 amps controller, you are still better off with the 14 ah pack, if it has the weaker cells.

Lastly, if the 36v 10 ah pack is a very good one, it may have 3c or better cells in it. There are some very stout cells out there now, and a few vendors are using them. In this case, 3c would be 30 amps, and it should be able to take some amp spikes from the 26 amps controller reasonably well. But, it will tolerate the amps even better in a 14 ah size.

 

[made_in_the_alps_legacy]

C rating is a batteries capacity in watt hours multiplied by a number

...
C unit is [/h] so [Ah] x [/h] = [A] and [Wh] x [/h] = [W]

 

[Henry111]

I have two LiFePO4 batteries, 36V/12Ah.
The chargers have been test so I know the chargers work.
Battery #1: When the charger is connected, the green light comes on and my volt meter read "0" but the batter will not take a charge even after being charge for 10 hours--still volts "0".
Battery #2: When the charger is connected the green light come on and my volt meter reads 29.5 volts. It will not charge above 29.5 volts even if left on charge for 10 hours.
Any suggestions will be sincerely appreciated.

 

[dogman dan]

I'd say chances are good you have dead cells in both packs.

Pack one could be entirely dead cells, or it could simply be completely disconnected from where you are taking your voltage measurement.

Pack two likely has some dead cells, so when most of the cells are fully charged, the bms stops the charging.

I don't know your level of mechanical/electrical skills. But I doubt you can do much harm now by unwrapping the battery, or removing it from the box, to investigate the charge level of the packs cell group by cell group. It's entirely possibly the pack 2 can be saved simply by balancing it manually, using a small 5v power supply like a phone charger to bring up the voltage of low cells.

 

[Henry111]

Thanks dogman, I sincerely appreciate your expert advice.
I'm going to open and work on these batteries, starting with Battery #1, because I suspect you are correct in that I have a disconnect where I measure the voltage so it (hopefully) will be the easier one to solve.
Then I will move on to Battery #2 on which I agree with you in that I probably have dead cells.
Note dogman, that these are both brand new batteries, both from the same company.
I will shoot and post photos as the work progresses and I will probably be back again for more of your expert advice, so I sure would appreciate it if you would stay with me on this. Hopefully, it will prove informative for other folks on the site.

 

[Henry111]

I removed both ends from Battery #1.
See photos below.
All wires seem to be connected OK.
Now please don't laugh!
But it was at this point that I decided to check the fuse. Check the simple things first! Right?
Duh!
Fuse is bad. Replaced the fuse and now Battery #1 charges up to 42.2 volts.
So now on to Battery #2.

 

[999zip999]

Be cafeful as just looking inside a battery can be danerous. It's very alive. Just one cell can start a fire let alone 60 cells. Never charge a lifepo4 cell above 3.6 with a ghetto charger. when it reaches 3.45v it will race very fast to higher charge and not stop. Good to hear of the fuse. Good luck. but a lot of stored energy. Many fires by packs like those lately. I would check the voltage of each of the parelle cells and list like.

1. 3.4v
2. 3.5v
3. 3.3v



12. xxx volt
Edit : please post.

 

[999zip999]

A balance battery is important. So check.

 

[Henry111]

Thanks for the advice xip999.
Years ago when we used Ni Cads in RC model aviation I was soldering up a bunch of them while wearing my wedding ring. Guess what happened. I still have the scar.
So yes, I will be careful.
By the way, before going any further on Battery #2 may I ask:
What is the possibility of this being a BMS problem--cutting off the charge at 29.5?

 

[dogman dan]

Great that you fixed number one so easy. I hope the reason the fuse blew was a fluke.

Yes, be very careful when inspecting the next one. very easy to touch two voltmeter probes to each other while checking voltages at the plugs.

With luck, number two is just very badly out of balance, and just needs some tlc to get it to balance better.

Just still guessing, but if badly out of balance, the bms is cutting off charge early, as it should in that situation. It stops the charge when any one group of cells reaches 3.6v or so.

The safest way to balance manually can be to drain high cells, vs charging low cells. Then put back on the regular charger. Either way, you do need to watch it like a hawk, and not go too far.

 

[Henry111]

So I got this sucker out of the aluminum case and open. See first photo. The other two photos are pics I got off the web someplace. I include them just for further clarity.
As you can see, this is 12S4P. (36V12Ah)
I don't mind admitting that I am a bit fearful of proceeding--not fearful of getting shocked--just fearful of making things worse than they already are. So suggestions will be sincerely appreciated.
What I do first?
How do I discharge the "full" cells?
Another question:
In RC modeling we have chargers that will balance the cells as it charges. In the e-bike industry, don't we have such chargers or devices that will do the same?

 

[Henry111]

So I got this sucker out of the aluminum case and open. See first photo. The other two photos are pics I got off the web someplace. I include them just for further clarity.
As you can see, this is 12S4P. (36V12Ah)
I don't mind admitting that I am a bit fearful of proceeding--not fearful of getting shocked--just fearful of making things worse than they already are. So suggestions will be sincerely appreciated.
What I do first?
How do I discharge the "full" cells?
Another question:
In RC modeling we have chargers that will balance the cells as it charges. In the e-bike industry, don't we have such chargers or devices that will do the same?

 

[dnmun]

don't do anything until you can charge it up to full charge and let it stay charging for several days until it balances and then measure the cell voltages at the sense wire pin plug on the BMS. you can put the voltmeter probe pins into the solder at the spot where the sense wire plug is soldered to the BMS. measure voltage of each adjacent pin without shorting them together with your probes. post up the recorded voltages. keep track of those numbers so you can refer to them later if you have problems with your battery.

 

[dogman dan]

In the bottom pic, to the left, that's the plug that has each cell groups balance wire.

if you have 13 wires, one wire will be negative, then all the rest the + wires, one for each group.

if only 12 wires, the large negative wire is the first wire.

You already tried to charge it for a long time, (I thought) so I'd look at voltages now. No harm trying to leave it on the charger now though.

If you find that one or two cells are at 3.5-3.6v or more and the rest at 3v or whatever, a cars turn signal light bulb can be used to drain just one cell. Then you could try the charger again.

 

[Henry111]

Anybody in the Los Angeles area who really understands e-blike lithium batteries and how to work on them?
If so, I have a proposition for him.

 

[999zip999]

Yea Henery when I was a pimp a woman gave me a 3.5 oz gold braclet. Was working on a washing machine changing the fuse and bam a plasma flash and a chunk on ea. side of the braclet blow off in a bolt of lighting. No harm no foul. It was a mine blowing to see that.

 

[Henry111]

I have a very nice Micargi beach cruiser that I really like. I am considering converting it to electric using the 750 watt 8fun kit--36volt, maybe a 48 volts. But this Micargi is a single-speed bike. Most posts I have seen regarding the 8fun discuss multi-geared bikes. I would appreciate opinions regarding the pros and cons of putting the 8fun on a single-speed bike. By the way, I have added a front rim brake to supplement the rear Coaster brake.

 

[dusan]

I guess, you are writing to non hub forum, you are speaking about bafang bbs
if you don't like your bike bottom bracket, lets do it, probably you will never get that in previous state
i'm really sorry for guys who did it, but you know, life is easy.

 

[cjh]

Check if the Micargi has a BMX BB. If so, you will need an adapter. Also, your coaster brake will become non-useable as the BBS02 has a built-in freewheel.