Battery problems

[lcyn]

I have a problem with my 48 V life PO4. when I turn on the switch2 my CA goes on for a second, then shuts off. If I unplug and replug it in a few times, it will stay on and I can ride the bike with no problems, but if I shut it off It will not turn back on unless I unplug it and replug a few times. I tried a different battery and all worked normal, so I know it is not my switch or CA.
Any ideas?


Thanks

 

[floatingdog]

Bad connector? The one you unplug and replug would be the suspect. If it sparks when you plug it in, it may be a little burned up. If they look burned, try polishing up both ends of the connector. You might be able to roll up a little piece of sandpaper to polish up the female part. If that seems to help, replacing the connector will probably be in order. If they don't look burned or corroded, I would still suspect a connector defect such as a bad crimp or loose wire.

Anderson connectors are great if you get a decent crimper. The stamped steel crimpers stink, but the plier types work great. You don't need the high dollar ratcheting crimper. Search for 'Anderson' on this forum for opinions and alternatives, and discussion of soldering vs. crimping. Crimping worked great for me.

The above are available from http://www.powerwerx.com. They have good prices and outstanding service. (No I don't work for them.)

Buy a 10 connector set such as this http://www.powerwerx.com/anderson-p...30-amp-red-black-anderson-powerpole-sets.html

These housings will hold the 15A, 30A, or 45A blades. The 30A blades fit 12 GA wires like a glove. For smaller wires, the 15A blades work better. For 10 GA wires, you would need the 45A blades. I bought a 10 connecter 30A set and a pack of 15A blades shown in the following link. That covers everything on my bike. I don't have monster wires, so I didn't need the 45A blades. You will end up with more blades than housings, but 10 housing sets will probably cover you for a while and you'll have lots of extra blades to perfect your crimping technique on. You can buy individual connector housings in different colors if you want to get fancy.

http://www.powerwerx.com/anderson-powerpoles/housings-contacts/1332-15-amp-powerpole-contacts.html

 

[lcyn]

I am not sure if it is a connection problem. The plugs look okay--no damage there. It will work okay if I replug it in a few times, but if I flip the toggle off and then turn it back on it goes on for a second and then shuts down. This battery is different from my Ping in that it is a 3c output. Otherwise it is the same (48v 10AH)

Could the CA or the controller cause an immediate shutdown?

Also another question. What is a good brand/style of on/off switch for the battery? I use a little toggle switch from Radio shack which is rated 40 amp @ 12v, and I have looked for something better, and had no luck. I wish some of these dealers of 48V packs would sell a compatible DC switch.

 

[Rassy]

Icyn, I've used several of these heavy duty breakers over the last several years. None have ever failed yet. They are also standard equipment on some 48V scooters:

http://www.werelectrified.com/ProductDetails.asp?ProductCode=Breaker+Switch

 

[Demosthenes]

Not an expert here, but could the inrush current could be tripping the BMS or something of the sort?

 

[lcyn]

That is a good point. How would the current be modified to stop the tripping of the BMS?

 

[amberwolf]

Add a "precharge resistor" so that when you are going to plug in, the resistor makes first contact between the positive battery connections, then after a few seconds you can finish pushing the plug in to make full contact around the resistor. The ground (negative) connection can simply be plugged in straight, before plugging in positive.

 

[tycreek]

I concure with amberwolf...
I had a very similar problem description with 2 different 48v batteries and not with other batteries (without BMS). Was related to controller charge, where one controller would trip the BMS all the time (BMC 50A) and another just sometimes (Kelly 75A). A double flip of my power/on switch with just right timing would get things to power up (not good for switch or connector). I now use 2 switches to power things up. Switch one (low current) has a precharge resistor that gets flipped on first until the CA reads 35v when I flip on the main power switch and toggle off the precharge switch. My current resistor is 2p470ohm 10w (235ohm 20w) though I don't claim these ohm/watt specs of my solution to be ideal by any means. I wanted a double throw switch but I didn't find one rated up to 50A.

 

[lcyn]

Thank You for your help. That sounds like a logical solution. Now I need to find the parts and do the install. The people on ES are A great help and very friendly.

 

[Demosthenes]

http://www.scriptasylum.com/rc_speed/_nospark.html
Your best friend for figuring out what ohm/watt precharge resistor you need.

 

[USAEBIKECO]

Battery problems happen to all of us sooner or later. I know the BMS is sensitive sometimes. What makes diagnosing so had is that the problem could be a number of things. The cold alone tripped my BMS several times. The cold would ower the voltage.

Hang in there. This board has some experienced people lurking that can offer good advice.

 

[Lessss]

I gave up on BMS, I want a way to read the voltage of each cell either all at once or serially while in use. Cell loggers are an almost solution. I don't need the logging ability just the direct reading.

 

[cell_man]

As has been mentioned it will more than likely be the BMS tripping with the in rush current that the controller pulls. The bigger the controller and the higher the voltage, the worse the inrush, the bigger the spark. I had this problem with a BMS and as was mentioned above a couple or 3 quick switches on/off will get you started.

 

[dnmun]

you can avoid the spark by leaving the power to the output FETs permanently wired and soldered in. then add a switch for the controller current and you can turn off the controller when not using the bike to prevent the battery from draining down.

the little red wire going to your controller carries the current for the control circuitry. the big wire carries the current that goes through the output FETs to the motor. they are separate circuits. then no need for the precharge resistor, and no problem with the connectors getting loose.

 

[lcyn]

OK--some new problems. It still does the rapid shutdown when I flip the toggle switch to on. That can be resolved by plugging/unplugging a couple of times while the switch is turned to ON position, and it stays on. So I did just that and rode the bike yesterday, about 14.5 miles and used 4.2 AH. I put the battery on the charger, a 5 amp charger, which should charge it up in about 1 1/2 hrs. Well, it ran and ran for about 4 hours, and still did not finish charging. My CA reads 54.5V and just stays there, still running. The BMS gets very hot. So I unplugged it, and this morning tried again, and same problem, it just keeps on running, and does not go past. 54.5V. This is a new battery, with 3C cells. The first couple of times I charged it to 58.v and it shut off, just as it should. I know the charger is OK because I use it on my Ping, and no problems. Does this sound like a bad BMS?

 

[dnmun]

no, it doesn't sound like a bad BMS. why would you think that?

the shunt resistors normally get hot when the cell it spans has charged up and the shunt current is bypassing the cell.

you should start by measuring the cell voltages, write them down and keep a record of how it changes as you charge up the pack.

 

[lcyn]

Thanks Dnmun

I have had it on the charger all morning, and it has finally moved to registering 58.3V on my CA. It is still running so I want to see if it eventually shuts off as it should. The BMS is no longer hot to the touch--in fact it is just at room temp

 

[lcyn]

The battery charged fine, and I used the bike Sunday--rode about 14 miles and used 3.8AH. Recharged and everything is ok in that dept. I think since it is a brand new battery it took longer to charge up after the first use.
I am going to try the precharge resistor as suggested and see how that works. I will have more opportunity to use this battery in the coming week, and will post my impressions on the reviews forum.