Point 1 LiPO BMS Issue?

[Uplink]

I was hoping someone could enlighten me on this BMS/charging issue I am having. Have this 37v 15AH LiPO battery with 3 amp charger I bought from EVtech last year. Usually, when you plug in the charger you get an amber power light, and a red charge light that turns green when the bat gets to 42.1v. The other day when I plugged it in, it started with the green light on, and didn't send any noticeable amps to the battery. At first I thought I had a charger problem.

Tested no load voltage on the charger: 42.1 volts. Load plug on battery: 39.2v. Charger plug on the battery 38.8 volts. Hmmm. Why should the battery have different voltages on the load side and the charger side? Never tested that before, so I don't know if that is normal or not. Tried hooking the charger to the load side of the battery, and got the red light and amps flowing. Hooked it back up to the charger side, and still no go.

Any help with the following questions would be greatly appreciated:
1. What could be the problem here?
2. How can I fix it?
3. Can I get away with charging through the load side of the battery?
4. Am I going to have balancing and safety issues if I charge the battery through the load side?
5. Is 700 miles all you get out of a $650 battery?

 

[Rassy]

Uplink asked:

Can I get away with charging through the load side of the battery?

I would say probably not. You would be bypassing the BMS and one of the cells in your pack may be overcharged before the total pack voltage reaches the charger's shut-off voltage.

As far as the possible problem, I have installed a connector between the BMS and the battery to allow me to both bypass the BMS during discharge, and/or to hook my Watts Up ahead of the BMS. If I try to check the voltage at the charger port with the BMS bypassed the voltage reads a little lower than the actual pack voltage, but I do get a voltage indication.

So, I would guess you either have a BMS problem, or maybe just a bad connection between the BMS and the battery.

Good luck.

 

[Ypedal]

Yeah.. unless you can access cell level voltage and check it manually .. i would not charge via the discharge wires.

You may have one low cell.. that will cause all the others to overcharge.. if it's a matter of 0.01v it's not a big deal but if you have one dead cell the others are going to go way high.. = bad with Li-Cobalt !!!!!! realllly bad !

 

[knoxie]

Hi

Yes sadly it sounds like the BMS or a bad cell, I have about 8 of these packs!! and have seen it on 2-3 of them, I dont understand why you are getting readings that differ on the charge and discharge leads though? on all my packs they are connected just inside the battery?, you may simply have a poor connection on this inside.

I have stripped and repaired a few of these, the point-1 bms monitors each cell and uses a bank of fets to cut the negative lead out of the battery, when you charge, it will open the BMS when the battery is charged and the charger light will go from red to green. You can charge it down the power leads as it is the same connection, I can show you pictures of this as I have pictures of the packs split open, Jozzer can verify this.

You may have a cell problem though, charge it through the power leads until the light goes green, then load test the battery, if it cuts out on you under load then you have a bad cell, if its ok it looks like a bad connection inside the battery.

The other thing is the point-1 factory used copies of Anderson connectors on the chargers and the batteries check those, they can be poor!! I changed all mine for proper Anderson connectors, if you change them remember only cut 1 wire at a time!! :lol:

You can take the packs apart and swap out bad cells, Jozzer did this to DCs packs, its a bit of a job though, check the connectors on that charging lead first, try it again, if it charges down the power lead, give it a full charge and check it again try that first and let me know, the chargers are intelligent as well and you can charge without the BMS and still get the green light but it is a little risky.

You should get a couple of years from one of these packs, all of mine are still performing very well, I did blow 1 bms board and changed that, I don't know if Doug has spare cells or does any repairs on them? its a messy old job though they fill the batteries with wax! gets everywhere!

Try that first and it may be a good idea to keep an eye on the battery when you charge it to test this just in case, I very much doubt you will have a problem but better to be safe, I don't keep or charge any of my cells in the house, even my NIMH packs, I prefer to store them in the garage.

Good luck and let us all know how you get on

Knoxie

 

[stew007]

I have no idea about BMS etc, but if its going to be a case of throwing the battery out, then it might be worth a shot to try and convert the pack so it can be charged by one of the new computer controlled balance chargers, they monitor each cell, they balance the pack while charging by draining the cells that are at a higher voltage, balanced right down to +/- .002v , and if any cell in the pack ever exceeds 4.215v it stops the charge, it also detects faulty cells and terminates the charge if there is a problem, so very very safe. Like the Hyperion Duo charger, but the pack would need balancing taps fitted for 6 cells and a separate one for the remaining 5 cells, and separate power wires, so to split the pack effectively into a 6s and a 5s, But this might be very tricky to do, not to mention dangerous if you short out the pack with a soldering iron. and also the tabs on some cells are aluminium, so a special flux is required. You would also need a low voltage cut off on the bike set to 3.3v per cell to protect it from over discharging.

 

[miro13car]

LIFe4 charger should read 44V no load, I also have 36V LeFe4.
MC

 

[MidniteTweeker]

Recently had a similar problem with an EVTech system. In my case, instead of the normal amber light that indicates charging is underway there was nothing but the red pilot light.

I did the basic voltage checks and found ~40-41 volts no-load coming from the charger. Since the system was only a couple weeks old, I called Doug at EVTech. He suggested connecting the battery to the bike & powering up, then watching the voltage on the CA over a couple hours. Sure enough, it slowly rose. But even after 24 hours the green light never came on.

During that time I also noticed that the cooling fan on the charger was not working anymore. All indications were a problem with the charger.

Doug mentioned there are two styles of chargers for this particular app; one with a plastic housing, one with aluminum. Mine was aluminum.

I returned mine & Doug sent a replacement which worked fine.

Before sending it back I removed the end of the charger where the LEDs are and noticed that a resistor next to the LED block appeared to be seriously fried. Made me wish I had a schematic.

Don't know whether your charger could have experienced a similar problem, but I wouldn't rule it out.

MT

 

[disadvantage]

I am late to this thread, but I'll post anyway. It might help.

I've had troubles with the EV Tech battery also. The rescue of my $650 battery starts here:
http://endless-sphere.com/forums/viewtopic.php?f=6&t=3672&start=19

It is possible to charge the battery directly with the red-amber-green charger that comes with it.

However, you must manually balance the cells periodically. That is why I added a 9-pin connector, so I can access each individual cell for testing and charging. I use a single li-ion cell charger from batteryspace.com.

I manually balance my battery every 2 to 4 weeks, or after a particularly draining (long and/or hard) ride.

 

[Uplink]

Fixed! Yeeehawwww. This one was full of expanding foam instead of wax...what a pain to clean off the BMS...

It did turn out to be a bad connection, so Rassy and knoxie called that one!

You can see the orange wire snapped right off. Must have been a brittle connection.

Does anyone have any ideas on what to use instead of spray foam to immobilize the innards? I suppose I can refill it, but that foam doesn't come off gracefully. Also, the tape that held the BMS on looked like celophane type packing tape. Does anyone know if packing tape will work?

Thanks for the help!

 

[disadvantage]

Glad to hear you got it working, Uplink.

Does anyone have any ideas on what to use instead of spray foam to immobilize the innards? I suppose I can refill it, but that foam doesn't come off gracefully.

Hmm, I made my case to exactly fit the battery, so this wasn't an issue for me. I think wadded-up newspaper would work, despite being a low-tech. Nobody else will know, because they can't see what's inside the box.

Also, the tape that held the BMS on looked like celophane type packing tape. Does anyone know if packing tape will work?

I used sticky clear plastic packing tape to put my pack back together. It is working fine, and I would expect it to do the same for you.

 

[Toorbough ULL-Zeveigh]

packing tape begins to disintegrate after a year, depending on the brand & whether or not it's exposed to sunlight or air maybe a little longer.

 

[Link]

Does anyone have any ideas on what to use instead of spray foam to immobilize the innards?

Hot glue the wires down, and then stuff it with some foam something or other. Fixes EVERYTING. :wink:

 

[Tiberius]

I like hot melt glue too. Its very useful.
I've even got some black stuff that I use instead of epoxy for potting small circuits.

Nick

 

[knoxie]

Hi

Glad you fixed it ok! they are making these different to the packs I have, mine are not like this battery at all? these dont look like point-1 cells unless they have changed the build. I would solder it back on and tack the wires with hot glue, packing tape will be fine, I have boxes in the loft with packing tape on that is 20 years old and still ok, I am pretty sure it will outlast the battery.

I must post a picture of 1 of my packs, its a packing tape job! I used the tin lid off a battery screwdriver box for the lid, looks ugly but its safe and works great!!

Glad you got it fixed and glad we could be of some help

Knoxie