Help with LifePo Battery - now what?

[leamcorp]

Hi, I just received a Lifepo battery from one of the Ebay vendor. Well, problem is he left out couple of things with this battery - like connector to charge the battery or instruction.

So my question is - how do I hook up a wire for re-charging?

The battery came with 3 wire and its labeled as follow,

- Red cable labeled as (P+)
- Black cable labeled as (P-)
- Blue cable labeled as (C-) This wire is thinner also.

So do I wire up the + and - like a SLA battery using XLR connector? What is the (C-) connector?

I also have another problem with BMS cables, but I'll tackle that after this one. Thanks for your help.

 

[disadvantage]

P+ and P- are Power output, to your controller and motor.

C- is input power from the Charger. Connect your charger to the P+ and C-.

What sort of problems do the BMS cables have?

Given your list of battery connections, it sounds like the BMS is integrated in the battery.

 

[leamcorp]

P+ and P- are Power output, to your controller and motor.

C- is input power from the Charger. Connect your charger to the P+ and C-.

What sort of problems do the BMS cables have?

Given your list of battery connections, it sounds like the BMS is integrated in the battery.

Thank you... But to clarify,

Do I connect the + from the charger to a P+ or C- ?

As for the BMS - 2 of the cable (pins) have popped out (the connector looks like thinner IDE cable for computer). I think I can figure out where they go and try to re-connect them (its all in a series - so it doesn't look like another pattern is possible). Do you know what that those connectors are called (and where to get one?).

I was very confused with this battery though. The one I won on Ebay was for 36v, 15ah Lifopo. The one I received says 48v, 20ah (charger also says 48v). On my volt meter, it goes up to 52-56v though.

 

[leamcorp]

Forgot,

The battery is divided into 2 bricks (blue duct tape), which I assume is 24v, 20ah each. The two batteries are then connected in a series (via quick connector). And BMS is connected into both battery (and power cables).

 

[Rassy]

Hi leamcorp. If your battery is like the standard duct tape LiFePO4's you would hook the charger + to the P+ and the charger - to the C-.

Do I connect the + from the charger to a P+ or C- ?

Where did you get the battery, and how much? It sounds like they sent you a lot more battery than you were expecting. Now that I am using my LiFePO4 on my recumbent, I would like to get a 48V 20AH version that is divided into two bricks so half can hang in a panier on each side of the rack.

 

[leamcorp]

Just sent you a PM.

I'm still dealing with him for couple of other things - so don't mention me until those things are ironed out.

I'm also going to test things out to see if its really 48v/20ah. If it is - I'll probably let him know and pay him extra for the next order. In the end, I may have to sell this battery if my motor gets too hot as I'm already over volting at 36v.

As for the BMS wire - do you think it will damage anything if I don't reconnect them? (and what is the function - the ide like cable?.. the power cable is also connected to the BMS unit).

 

[Rassy]

As for the BMS wire - do you think it will damage anything if I don't reconnect them?

The battery and the BMS are really two separate things. You can use the battery without the BMS but you will be risking over discharge. Since the LiFePO4 holds its voltage fairly constant, and then falls off real fast, you don't have time to respond to a low battery before cells can be damaged. Thats why you should always use the BMS unless you are just doing a known partial discharge. As far as charging, again the voltage goes up slowly, until the end, and then goes up real fast, so without a BMS cells will be damaged during the charge cycle.

the power cable is also connected to the BMS unit

As mentioned above, this is so the BMS can cut off the power if any cell falls below a certain voltage. When I received my second LiFePO4 pack from Anna, the BMS was faulty. So I just removed it (cut the - wire between the battery and the BMS) and made the good BMS so that I could plug it in to either battery. But because the BMS had a cutoff of 30 amps and my controller used 35 amps, I also used this point to just bypass the BMS during usage (for shallow discharges). I have now beefed up the BMS amp cutoff and always use it during discharge. Plus anna replaced the faulty BMS, so each battery has its own. Plus, I use that same point when I want to use my Watts Up meter.

So anyway, you can disconnect the BMS as long as you stay away from the low voltage point, but you do need to use it during charge.

(and what is the function - the ide like cable?..

I don't understand your question here?

 

[Ypedal]

Most of these BMS boards will "ballance" the voltage of the cells at the end of the charge cycle by draining power from the higher voltage cells ( using resistors.. and creating heat )

All the wires need to be hooked up for the " pack " to work as a team with the BMS.

That said... personally.. ( AND I DO NOT RECOMMEND THIS ).. i do not use any BMS's on my lithium packs.. because they either failed.. or did not do what they were supposed to do.

This means i never discharge more than 75 % of my packs AH capacity.. monitored with a CA meter. ( cycle analyst ) .

And i charge with single cell chargers, one charger per cell. yes.. that makes 16 chargers, so i know that every cell gets a full charge.. every time.

Not the best way.. but my way.

 

[leamcorp]

Rassy, where did you get the connector - the connectors from the battery to the BMS unit. It looks like 16 pin connector (this is what I meant by IDE like connector - although its much thinner/shallower dimensionally).

I did re-connect the loose pins, but I would like to re-crimp them with a new one to make sure its on there tight.

Is there anyway test the BMS to see if its working or not? I did order the Cycle Analyst, but it won't help with charging.

Cheers.

 

[Rassy]

Rassy, where did you get the connector - the connectors from the battery to the BMS unit.

Little mis-understaning here. I didn't do anything with the 16 pin connector that came with the battery/BMS except unplug it from one BMS and plug it into the other BMS. The wire I cut was the main negative wire between the battery and the BMS, and just used a standard crimped on 1/4" blade connector for convenience in swapping/bypassing the BMS.

Is there anyway test the BMS to see if its working or not?

You said you tested your charger and confirmed it is for 48V. You said the BMS had 16 little pins/wires, so that would be a 48V pack. You could test your battery with your DVM and if it shows something in the neighborhood of 50V (probably a little more), then you have confirmed it is a 48V pack. So I would say just hook up the charger and confirm that it starts charging. Your DVM should confirm that the voltage goes up to about 59V before shutting off. If balance is needed, the charger should cycle on and off for a while. When the light is red it is charging, etc. Be sure to get the charger polarity right.

 

[disadvantage]

Rassy got it right, on how to connect charger to battery. I should have given as much detail as he did.

I was very confused with this battery though. The one I won on Ebay was for 36v, 15ah Lifopo. The one I received says 48v, 20ah (charger also says 48v). On my volt meter, it goes up to 52-56v though.

The 52-56V you observe is the peak (fresh-off-the-charger, no-load) voltage. The nominal voltage is closer to 48V, and you should see this when you connect everything up with the Cycle Analyst and start riding.

A battery rated at 36V nominal gives about 42.5V peak.

 

[leamcorp]

I think that will blow my enemic Ezip motor... but since I have a spare motor/controller, I give it a go.

I'm also on a fence for Texas Electric's geared motor or the Pheonix Cruiser. I just can't decide between the two.

 

[docnjoj]

If U drill lots of holes in the Ezip motor it might hold up to 48volts?????!!!!! I run 42 thru mine and am about to drill the holes and cover the motor with the K&N filter. See Tylers and EcoforumZ threads for more details!
otherDoc

 

[leamcorp]

If U drill lots of holes in the Ezip motor it might hold up to 48volts?????!!!!! I run 42 thru mine and am about to drill the holes and cover the motor with the K&N filter. See Tylers and EcoforumZ threads for more details!
otherDoc

Unfortunately, I've already done that and at 36v - at fairly moderate use, the motor still get fairly hot. However, since I already have a spare motor/controller, I will try it to see if I could push it further.

In the end, since this is my daily commuter, I will get something bit more robust to make sure it won't break down.

 

[docnjoj]

Maybe consider the TNC true 36 volt motor with 10:1 gearing! Our motors run about 7:1 gears. U should do this if U really plan 48 continous LiFepo4 running! My NiMh are really "gentle" to motors, meaning they suck big time when extra amps are required! My wifes PingPack really makes tis little motor come alive!
otherDoc

 

[leamcorp]

Maybe consider the TNC true 36 volt motor with 10:1 gearing! Our motors run about 7:1 gears. U should do this if U really plan 48 continous LiFepo4 running! My NiMh are really "gentle" to motors, meaning they suck big time when extra amps are required! My wifes PingPack really makes tis little motor come alive!
otherDoc

Thats the spare motor I have. I just haven't installed yet.

But using the stock 24v motor and the 48v Lifepo4 battery - I broke the 30mph barrier. Here's typical speed for each progression,

My weight is 210 and following numbers are for non-assisted (meaning power only) riding on a very flat road.

1) stock 24v SLA top speed = 16mph
2) 36v SLA top speed = 23.5mph
3) 48v Lifepo4 top speed = 31.4mph

Oh, I don't think I'll be running this new battery other than for a quick test above. The motor housing got quite hot for no more than 8-10 minutes full/near full throttle. Again, this is my commuter and I need it to be alive tomorrow.

 

[leamcorp]

For those who have a duct tape Lifepo4 - does your BMS get very hot? Hot enough to not be able to hold them or enough to shrink the rubber casing it came with? Mine did today and I wasn't sure if this was normal. It doesn't seem like it should...

 

[docnjoj]

No, BMS gets warm, but not hot during discharge! Doesnt get hot on charge either! 36 volt, 10 ah Ping. Ridden very conservatively 2-3 ah per hour ride on Bike-e with lots of pedaling over 10 miles in about an hour!
otherDoc

 

[leamcorp]

No, BMS gets warm, but not hot during discharge! Doesnt get hot on charge either! 36 volt, 10 ah Ping. Ridden very conservatively 2-3 ah per hour ride on Bike-e with lots of pedaling over 10 miles in about an hour!
otherDoc

Thats really strange. Only one end of BMS got really hot and shrank the thin rubber casing (sheeting is more like it).

It doesn't get hot when charging and this was 1st time I've noticed it. I've put a question to the seller and hopefully he'll come up with the answer.

 

[Rassy]

leamcorp wrote:

does your BMS get very hot?

I noticed something strange the other day on one of my BMS's. The little wire bridge like resistor that allows the BMS to regulate high amperage during discharge melted the blue plastic wrap, just where the bridge touches the plastic. Out of three BMS's (for two batteries, long story), this is the only one that will support the draw from my WE BD36 35 amp controller without being modified. The batteries are 48V 20AH from anna and the extra BMS came from Ping. I don't know anymore if this was the Ping BMS or not.

 

[leamcorp]

I just got a email back from seller - he basically said that hot BMS was normal.

I don't believe it - this thing was super hot and shrank the rubber casing. I think I'm going to borrow some of the ideas and only use the BMS for charging. When on the road, I'll use the Cycle Analyst to cutoff when certain limit is reached. It will be few more wires, but I just can't trust these BMS's

 

[Pete]

My Ping BMS has gotten warm enough to slightly melt some cheap foam I was using as padding. The padding was originally in contact with the end of the BMS with the power fets. No change in colour on the duct tape or the heatshrink, so it wasn't _that_ warm. After thrashing the pack at 1.5C continuous the BMS is just warm enough that it is obviously warmer than ambient when felt with a bare hand. But that could also be conducted heat from the cells themselves because my pack is sealed inside an ammo tin with pretty much zero air circulation.

My BMS is for a 24v20 pack, so it may be a different design to yours.

 

[recumbent]

The BMS is never supposed to get so hot it shrinks the shrink wrap :? . Or it needs a heat sink.

My 48 volt LIFEPO4 gets warm when used hard for an hour straight, no pedaling, but never hot.

You may just have a bad connection and should inspect it. Might be easy to fix. Unfortunately you have to re-shrink wrap it

It's a bummer when stuff doesn't work like it should. :|

 

[leamcorp]

I took the rubber casing off and it looks like one section was in early stage of melting. This is after no more than 5-10 minutes of moderate use.

How do I attach pictures?

 

[leamcorp]

Okay, I hope one of the reader here bought a 48v duct tape battery recently - that was divided into two brick.

I just got a word from seller that I got the wrong battery, which I don't have swapping with right buyer. But this person should know the problem I've had about the BMS and the cabling issue. I don't want to send the battery and have his person think that I did anything to his battery. So if you're here, let me know and we could do a PM.