Help w/ converting to LiFePO4 from SLA

[eNdo]

HI, I'm new here. Definitely glad to have found this community! I know I have tons of info to read through now.

Here's the deal, I have an e-bike built using the Wilderness Energy BD-36 kit. The e-bike is a 36v 600watt front hub motor with a 50amp controller. I don't like the SLA batteries that the kit came with so I recently purchased a 36v 20ah LiFePO4 battery from ebay (seller: power_battery_a123).

Now I don't know much about electronics but I gave it my best shot trying to wire the new battery up. The LiFePO4 battery arrived with 2 wires, red and black coming from the battery. I figured I would simply wire those two wires in the exact same place that the SLA batteries were hooked up to. The problem is, the wires coming from the LiFePO4 battery are significantly thicker gauge than the wires coming from the controller. I wired them up anyways and tested the bike but got no power.

What should I do? Do I need a different controller? IS the fact that the battery cables are thicker than the controller cables causing the problem?

The end of the SLA battery pack that came with the Wilderness Energy kit has a special connector on it that fits onto a similar connector coming from the controller. What I did was cut the wires on the battery side and reconnected them to the new battery. This way, the special connector is still intact. Should I have connected the wires directly and eliminated the special connector?

For reference, the power connector I'm talking about looks just like the one in the picture. Its the wire on the far right side:

 

[Ypedal]

Welcome to ES !

That connector is commonly found at automotive supply places, " Trailer Connectors " , they come in 2,3,+ pins.. not the best thing available by any means, if you want to upgrade your connectors look up " Anderson Powerpole PP45 " ..

Got a volt meter ? that's the next thing to know, the battery voltage at those wires. Is there a circuit board between the battery and the controller ? ( bms ) or do the wires go directly to the battery terminals ( assuming you can tell, depends on how much the battery is covered )

Got a digital camera ?

 

[eNdo]

Welcome to ES !

That connector is commonly found at automotive supply places, " Trailer Connectors " , they come in 2,3,+ pins.. not the best thing available by any means, if you want to upgrade your connectors look up " Anderson Powerpole PP45 " ..

Got a volt meter ? that's the next thing to know, the battery voltage at those wires. Is there a circuit board between the battery and the controller ? ( bms ) or do the wires go directly to the battery terminals ( assuming you can tell, depends on how much the battery is covered )

Got a digital camera ?

Thanks for the quick response!

Yes, the battery came with a BMS circuit board. So the battery is connected to the bms, and then the positive and negative wires coming from the bms have been spliced onto the original wires that were originally connected to the SLA batteries and conncected to the controller.

Here is the LiFePo4 battery and the BMS sitting right on top of it:

Here you can see where I spliced the positive and negative wires to the smaller wires that were originally connected to the SLA batteries. You can see the connector that matches the connector coming from the controller.

Here is the same connector coming from the controller:

Here is everything connected, but with no power getting to the motor or the LED power meter on the throttle:

Any ideas? I'm thinking its the wires. They are thick coming out of the bms but thin going into the controller...

 

[Ypedal]

the wire thickness is not your problem, the controller should still power up and run just fine..

The BMS has Charge and Discharge wires, the thicker one's are usually the discharge going to the conroller..

were the wires stripped back and a good twist of both leads making contact before you taped them in ? soldering them would be a good idea if you have the tools.. Crimp tubes also work well..

If you connect the SLA batteries to the controller does the bike power up ?

 

[eNdo]

the wire thickness is not your problem, the controller should still power up and run just fine..

The BMS has Charge and Discharge wires, the thicker one's are usually the discharge going to the conroller..

were the wires stripped back and a good twist of both leads making contact before you taped them in ? soldering them would be a good idea if you have the tools.. Crimp tubes also work well..

If you connect the SLA batteries to the controller does the bike power up ?

Ok I just went and stripped some more wire and twisted both leads really well so I'm fairly confident that they are making a solid connection. When I tested it, still no power.

I reconnected the SLA batteries as they were before and, yes, the bike still powers up as normal. The controller turned on, the LED battery meter lit up, and the motor ran fine. So all the parts still work. The problem is somewhere between the battery and the controller.

I know the battery has charge to it because I touched the two wires together (just to see) and sure enough sparks flew. I hope I didn't damage the battery doing that. I know that wasn't the smartest thing to do. I just had to see if there was juice and don't have the proper tools for that yet.

When I plug in the charger to the bms, the led lights up yellow and shows that its charging. I've already let the battery charge well over 24 hours.

I think I'm going to try to solder the connections next...

 

[eNdo]

I should also point out that when I received the battery from China, the Material Safety Data Sheet that came with the battery says that this is a LiCoO2 battery and not a LiFePO4 battery. I immediately contacted the seller and they insist that they made a mistake and that they only build LiFePO4's. The sellers history on ebay is very clean and no other customers seem to have ever had a problem with their batteries from this seller.

Is it possible to disguise a LiCoO2 as a LiFePO4??? The battery they sent me is definitely lighter than the SLA batteries, as advertised.

What could cause a battery to not work with a particular controller?

If they accidentally sent me a 48v battery pack instead of 36v, would the bike still power on?

 

[billvon]

I know the battery has charge to it because I touched the two wires together (just to see) and sure enough sparks flew.

Yikes, don't do that. If the BMS is working then it will disconnect the output (to protect the battery) and you'll see zero output until it resets. If the BMS isn't working, and those are really lithium cobalt cells, you might see some fireworks.

You definitely need a meter. Resting voltage for a lithium ion battery (i.e. the cobalt one) is around 3.3 to 4.2 volts per cell. So if you have 10 cells in series you'll see 33 volts (almost dead) to 42 volts (fully charged.) LiFePO4 cells are between about 2.2 to 3.6 volts. So you'll see between 22 and 36 volts depending on charge level if you have ten in series.

A fully charged 10-cells-in-series LiFePO4 pack should operate a 36 volt system for at least a little while, until voltage drops below LVCO. If you have fewer cells in series it might not. If you have more, you may exceed the controller's maximum voltage rating.

 

[dnmun]

shorting it out is no test. before you damage anything, go get a voltmeter at harbor freight and read the directions. you should be able to tell what the battery voltage is right away with a meter, sounds like it is dead, just not clear how dead and if it will charge up yet.

i think you should go read the east china music/jimmy wu threads too, have you looked at the other stuff sold by your ebay seller and what his comments look like? is it all the ebay fluff? another name to add to his list i am afraid.

 

[dogman dan]

The first thing I'd do with a voltmeter is check the voltage, while doing that, you will see which wire is actually the positive one. I wonder if it is the black or the red? I'm flummoxed about the two wires though, most lifepo4 packs have a third negative for charging. Does it have another two wires for the charger? Or just two wires. I hope you don't get emails from a mr lau when you ask them about it.

 

[eNdo]

The first thing I'd do with a voltmeter is check the voltage, while doing that, you will see which wire is actually the positive one. I wonder if it is the black or the red? I'm flummoxed about the two wires though, most lifepo4 packs have a third negative for charging. Does it have another two wires for the charger? Or just two wires. I hope you don't get emails from a mr lau when you ask them about it.

There are two wires for the charger which have been soldered onto an adaptor that connects directly to the charger. These are seperate from the other two wires that are red and black, which I assume are the power connections.

 

[Ypedal]

At this point you really need a volt meter.. get your hands on one and we can help you figure out how to use it ! :wink:

ps: You could bypass the bms and hook it up direct but without knowing the voltage you could do more damage to the pack if one of more cells is drastically out of ballance.... or worse yet.. dead cells in the pack are possible and they could be causing the BMS to cut out as intended...


either way.. you need a meter !!!

 

[eNdo]

Ok I'll go and get a meter. Its something I know I've been needing to get anyways. Unfortunately I have to go out of state this weekend and won't be able to get back to this until after the weekend.

I'll get my meter and test the voltage on the batteries soon and post the results here.

Thanks again for helping me with this. I know its total noob stuff but hey, we all gotta start somewhere right?

 

[dogman dan]

We are of course thinking that the battery has been charged. The voltmeter will tell you if it is really charged, and you can check the charger too with it. Sadly, we may have another vendor selling packs with defective bms boards. Most that have had this problem have fixed it by buying a new bms from Ping, eliminating the savings they hoped for.

 

[eNdo]

I just bought a voltmeter and tested the leads on the battery. The meter shows between 41.9 and 42 volts. I tested the original SLA batteries and they came up 39 volts.

So I'm pretty sure this means the battery isn't dead, right?

It seems that no power is getting through the adapter that was spliced onto the power leads (to easily connect to the controller). I tested for voltage there first but got nothing. Then I disconnected the adapter and tested the battery directly and got results. I think the next thing to try would be to wire the battery/bms directly to the controller and skip the adapter connector. I just hope the battery doesn't fry the controller! Here goes.....

 

[Ypedal]

Great !! ( the voltmeter will come in very handy in this ebike business ) :wink:

You want to have a connector between the controller and battery, anytime you are not riding you want to disconect the battery from the system to prevent the controller from draining a small amount of power ( yes, the controller does use power even if the motor is no running ) this is not alot of power but enough to be a problem if you go for a long ride and the battery is near empty.. on a full charge the controller could be plugged in for weeks before draining the pack...

another reason is safety, having a " Live " bike all the time can be dangerous, these silent rigs can really pack a punch when unexpected ( like moving the bike in the house and accidentally hitting the throttle ) :wink:

 

[dogman dan]

Yay! I was hoping it was as simple as a bad plug. Wire it direct for a test, but get some anderson connectors ASAP.

 

[itselectric]

eNdo:

By reviewing your picture of the controller and based on your description, it looks like you have a BL36 instead of BD36. Can you please confirm how many wire is coming out from the motor? What color are the wire?

Assuming that you wire the battery correctly, and you have voltage come from the new battery at 42volt, and you are not able to see the LED come on, can you please switch back to your SLA battery and see if it works. If you switch back to SLA and it works. This is most likely your new LiFePO4 BMS were programmed too sensitive. There is a common thing about BL36 controller, when you plug the battery onto the controller, it will cause a spark. This is due to the capacitor in controller sucking up electricity as soon as it comes into proximity with power. When this happen, some of lithium battery BMS will shut down the battery. It think it is over discharge (over load) the battery. We have the same problem with our early lithium battery. Since our lithium battery BMS had built-in programmable interface, we can re-program BMS to correct this problem.

Please let me know if it works when switch back to SLA battery.

Ken
_________________________________________________________________________________________
Youtube: http://www.youtube.com/powerinmotion
Website: http://us.itselectric.ca

 

[eNdo]

Its ALIVE!!! Its ALIVE!!!

The problem was the connector that came with the kit. I don't know why but power simply was not getting through. I cut the connector out of the equation and wired the battery bms directly to the controller using standard disconnects (to easily disconnect the battery when not in use).

The bike runs great! In fact I think it runs a little faster. I wonder if its because the battery tested 42 volts and not 36 volts. Is that dangerous?

Thank you everyone for your help with this. I am most appreciative. I also very glad to have found this unique community of like minded people! I will definitely be sticking around and posting here.

Now I just need to tune-up my bike. Riding it the last few months with the electric motor has really done a number on that bike. As soon as the bike is back in good shape and safe to ride I will be testing the range of my new LiFePO4 battery! My commute to work from Tempe, Arizona to Scottsdale, Arizona is 16 miles each way. Its quite a nice little adventure.

Again, thank you to everyone who helped out with this! 8)
-Eric

 

[fechter]

The bike runs great! In fact I think it runs a little faster. I wonder if its because the battery tested 42 volts and not 36 volts. Is that dangerous?

-Eric

I wouldn't worry about that. A 36v lead-acid pack will be close to 45v right off the charger. The controller *should* be able to handle that.

Getting rid of a bad connection will increase your speed a little too.

 

[dogman dan]

Now that you mention it, that does look a bit like the BL controller. If it's the Brushed, there will be only two wires to the motor hub.

 

[eNdo]

Now that you mention it, that does look a bit like the BL controller. If it's the Brushed, there will be only two wires to the motor hub.

Uh oh. Don't say that! I'll take a look when I get home today...

 

[dogman dan]

The BL kit is better, running cooler,and going farther.

 

[Drunkskunk]

Its ALIVE!!! Its ALIVE!!!
The bike runs great! In fact I think it runs a little faster. I wonder if its because the battery tested 42 volts and not 36 volts. Is that dangerous?

Welcome to the forum, and glad you got the connector problem worked out!

A note on the batteries.

How many cells does the pack have, and what is the weight?

LiFEPO4 batteries come in a few cell veriaties, usualy with 3.3 volts nominal, and around 3.6 volts fully charged. so a "36" volt pack would be made of typicaly 11 cells, and fully charged at 39.6 volts, although there are a few other cell configurations possable that use diffrent lower nominal voltages, and use 12 cells. these couold possably be charged to 42-43 volts depending, but they will have 12 cells or more in the pack. The battery should weigh 8 to 10 pounds for a 36 volt, 10Ah pack made of flat pouch style cells.

LiCo battery cells come in just 3.7 volts, with a fully charged voltage of 4.2 per cell, and the LiCo batteries sold as "36" volt have 10 cells, meaning fully charged they end up at 42 volts. The type used in a Bike back weighs 5 -5.5 pounds for a 36 volt, 10Ah pack.

Count your cells and weigh it. If it's LiCo, be sure to charge it out doors.