Why was my SLA pack better then my LiFePo4 on the hills?

[jamo96]

Went home, plugged in the charger and once again it worked it's way up the voltage scale stopping at 43.8 volts. This time I gave the system 45 minutes to balance and just like before it balanced all the cells to 3.3 volts.

Do you mean 3.3V? Should be charged to ~3.6V

 

[www.recumbents.com]

A hill like that takes about 2000 watts to get up, maybe 1500 watts if you have a running start. If your motor is only 800 watts, that's not enough. Will that motor take a 48 volt battery? Also the BMS on your LiFePo4 battery may be limiting the current. You can try bypassing the BMS and hitting your hill to see what happens, but I wouldn't run it like that for long.

-Warren.

 

[e-beach]

Do you mean 3.3V? Should be charged to ~3.6V

Yes..the cells have all balanced at 3.33 volts consistently now every time.

 

[e-beach]

If your motor is only 800 watts, that's not enough.

But that is the thing. My 12v 12ah SLA's when they were new took me all the way up the hill. It was only 5 mph at the top, but they took me up there. :lol:

And when I pulled them 8 months later, they still took me 2/3 the way up the hill before I need to pedal. This Headway pack can not match that. I can, however go 20+ miles on a 90 minute charge, but I may have to get a hotter charger that will go to 45 volts provided my BMS will take it.

The charger I am using is supposed to be a "fast" charger and now I know why it is. Even though it is 12 amps, It only charges to 43.8 volts and then the BMS balance's the cells down to 3.33 volts. Looks like I am not getting all my volts.

 

[DAND214]

By the picture of the charger, there is a pot to turn up the voltage. It should be near the fuse and output cable.

3.3v is still too low for a full chargered LiFePo battery.

They should be able to blow the lead off the road. Lighter and more powerful, if fully charged. Maybe there is a bad cell, not voltage but hi resistance (bad connection) which is cauding a bad voltage sag.

Dan

 

[e-beach]

By the picture of the charger, there is a pot to turn up the voltage. It should be near the fuse and output cable.

I haven't opened the charger yet. I was wondering if it had an accessible pot to turn up the voltage some...but her is the thing about that. It is a smart charger that shuts off when it reads 43.8 volts from the pack. So how would one not only turn up the actual voltage AND trick it into thinking the higher voltage was 43.8 volts?

In other words, if I trimmed a pot for higher voltage, would it not just pump out more amps faster and just reach 43.8 volts faster and still cut out at 43.8?

They should be able to blow the lead off the road. Lighter and more powerful, if fully charged.

One would think that is the case...but maybe not. As noted earlier by Warren, I would need to bypass the BMS and power the motor directly with my LiFePo4's to see if the BMS is limiting the amps to my motor. If I can figure out how to do that then I will try it later.

Maybe there is a bad cell, not voltage but hi resistance (bad connection) which is causing a bad voltage sag.

The pack connectors are either the metal bars supplied with the batteries or 10 gauge wire with connectors well soldered on to them. All the wiring on this pack is equal-to or better-than the wiring on my SLA pack so I would day it is not a connection issue.

After all the help on this thread, I have two theories going:

1) My charger just doesn't charge my back high enough to get a full charge. (Perhaps it is designed that way to help extend the life of the cells.)

2) The BMS is choking the amps to my motor. (Perhaps it is doing so to keep the cells from going past 3C on it's discharge.)

I will try to bypass the BMS today and see if that changes anything.

 

[dnmun]

that is not a smart charger, that is a lipo charger.

lifepo4 chargers do not shut off when the charger voltage reaches the end voltage. lipo chargers do shut off when they reach the final voltage.

but of course it is not clear if it really does shut off. you need to insert your wattmeter in the charging line and measure the current when it reaches the 43.8V level. if the current stops then you need to change chargers so your pack can balance. or you have to raise the output voltage high enuff that it will remain on even when the pack has climbed to 45V.

the BMS does not balance the cells by dropping the voltage to 3.3V.

the BMS does not modulate the current output from your battery.

the headway BMS will balance your cells to exactly 3.65V when you leave it on the charger. that is how the BMS balances the cells, while they are charging, not afterwards.

removing the BMS will prove nothing.

 

[e-beach]

that is not a smart charger, that is a lipo charger.

lifepo4 chargers do not shut off when the charger voltage reaches the end voltage. lipo chargers do shut off when they reach the final voltage.

but of course it is not clear if it really does shut off. you need to insert your wattmeter in the charging line and measure the current when it reaches the 43.8V level. if the current stops then you need to change chargers so your pack can balance. or you have to raise the output voltage high enuff that it will remain on even when the pack has climbed to 45V.

the BMS does not balance the cells by dropping the voltage to 3.3V.

the BMS does not modulate the current output from your battery.

the headway BMS will balance your cells to exactly 3.65V when you leave it on the charger. that is how the BMS balances the cells, while they are charging, not afterwards.

removing the BMS will prove nothing.

Well....aaa...ok. I guess all I can say is:

I must be unclear on the concepts.

This is what I know.

When charging my pack the charger fan is fairly loud so I can tell when it is working hard.
I do not have an inline amp meter at the moment but I can meter the voltage at the charger plug on my pack.
As the charger runs my voltage meter slowly climbs 41.6, 41.7, 41.8 etc.
When the Charger fan stops running the voltage is 43.8 like the rating states.
(edit) Once the charger stops running the voltage slowly starts to drop.(edit end)
If I check the cells just after the the charger fan stops they read between 3.39 and 3.51 volts
If, after checking the cell voltage I plug in the charger again and leave it there for 45 minutes and recheck the cells, the cells all read 3.33 volts.
If I make a run at my little 10% grade hill with the slightly higher charged batteries the outcome is the same as balanced cells. The motor cannot drive me up the hill as far as my SLA's did.

I have not pulled the charger just after the fan stops running and just let the pack sit for a while to see if the system balances by it self without the charger.

I will leave the charger on the bike overnight tonight to repeat the test as I have only done that once and I want to make sure the outcome is the same.

Dogman has stated that balancing takes a long time and by this statement

the headway BMS will balance your cells to exactly 3.65V when you leave it on the charger. that is how the BMS balances the cells, while they are charging, not afterwards.

I will assume you are in agreement with him on this point.

Thanks for the help.

 

[e-beach]

Ok, since my little brain is exploding with wonder, I did a bit more research.

that is not a smart charger, that is a lipo charger.

lifepo4 chargers do not shut off when the charger voltage reaches the end voltage. lipo chargers do shut off when they reach the final voltage.

It is said to be a LiFePo4 smart charger, and a lipo charger....and a SLA charger.

This from; Headway headquarters where I bought it from.

FEATURES: Intelligent charger designed for 12 cell LiFePO4 battery packs.

http://stores.headway-headquarters....charger,-lifepo4/Detail.bok?category=CHARGERS

This from the internet:

Detailed Product Description

36V 12A battery charger for lead acid battery, silicon battery and lithium battery.
Apply to battery: LiFePO4, Li-ion, Li-polymer, Lead acid battery pack
3)Completely automatic battery charging: CC,CV, Float or Cut-off.

3)Completely automatic battery charging: CC,CV, Float or Cut-off.

It sounds smart to me. :lol:

I just think this "all Headway Headquarters" system is doing exactly as it meant to do.

PS. I have been charging my pack this morning. It went up to 43.8 volts as described previously, then the fan on the charger went off and the voltage in the pack slowly dropped to 40.1 volts or 3.33 to 3.34 volts per cell....just as before. It has been 40.1 volts for over an hour now :?

 

[dogman dan]

Hmm. I'm getting more confused too. 43.8v should be 3.65v per cell, yet you've never seen a cell higher than 3.5v. That's a bit odd.

It should start slowly losing the exess charge that helped it balance, then as the surface charge dissipates, it should settle at about 3.5v per cell. It shouldn't happen real fast on new cells, but it does with older ones.

One thing I've seen, is that just because a pack reads 43.8v when it's got the charger on, does not mean it's at 43.8v. Some of those last few volts are coming out of the charger.

I see two likely possibilites here. One is that the charger shuts off too soon. So it's not really charging to 43.8v, but rather closer to 41v. Does the light turn green when the fan shuts off? The other is that the bms, which should be draining cells once they get above 3.65v, is actually starting up at about 3.3v.

First thing I'd do, is go buy the very cheapest possible 36v lifepo4 charger I could find on ebay. Try it. If it works better, bingo it's your charger.

Of course, as usual, you could have a problem with both items. Another possible approach would be to try charging the battery with your charger, but with the bms unplugged. If it holds a charge of 43.8v, bingo your problem is the bms.

 

[e-beach]

OK, stright out of the testing department....

I went for a ride, went up my short 10% grade hill, went up my short 12% grade hill, went down the 12% grade hill, went up another hill and then down the long 10% grade hill that is too long to go up right now.

Plugged in the charger and monitored the voltage.
At 43.8 volts it stopped charging.
Immediately pulled the plug and metered the pack. It read 43.5 volts.
The voltage then started to drop little by little.
Went for another quick ride and started to recharge.
Charger quit at 43.8 but I left it plugged in this time.
2 hours later I checked the voltage and it was 40.0 volts.

One thing I've seen, is that just because a pack reads 43.8v when it's got the charger on, does not mean it's at 43.8v. Some of those last few volts are coming out of the charger.

Perhaps a few tenth of a volt, but by my testing not 2 or 3 volts.

I see two likely possibilities here. One is that the charger shuts off too soon. So it's not really charging to 43.8v, but rather closer to 41v.

When I pulled the charging plug the pack read 43.5 volts.

Does the light turn green when the fan shuts off?

Yes

The other is that the bms, which should be draining cells once they get above 3.65v, is actually starting up at about 3.3v.

That seems to be true by my testing, or in other words, the the charger cuts at 43.8 and the bms drains the voltage to 40 volts.

First thing I'd do, is go buy the very cheapest possible 36v lifepo4 charger I could find on ebay. Try it. If it works better, bingo it's your charger.

Guess "I'm not so think as I dumb I am" cuz I was thinking the same thing. :lol:

Of course, as usual, you could have a problem with both items. Another possible approach would be to try charging the battery with your charger, but with the bms unplugged. If it holds a charge of 43.8v, bingo your problem is the bms.

I am going to try that tomorrow! Thanks. It will defiantly help isolate what might be multiple problems.

It has been hot around here, like every where else, so it could be the weather, but today I notice that the wiring to the motor was warm to the touch during my uphill climbs. And, the motor itself has been making a whining sound when the throttle is depressed. It didn't make that sounds with my SLA's. :x
When I let-off the throttle the sound stops.

My conclusion on that is that the motor is being starved of amps under heavy load and the wiring is heating. So because I can isolate the bms out of the equation tomorrow, that's what I will do and see if I have any changes.

 

[JimmieD]

Okay, have not fully read through everything but it is getting late and I need to hit the rack so if this has already been said or addressed I apologize.

e-beach, have you modified your charger yet by removing the safety PCB from within the charger? This PCB prevents the charger from 'talking' with the BMS so once the BMS 'tells' the charger to stop charging because of a HVC on a cell, the charger will turn off and will need to be unplugged from the battery and from the power source to 'reset' itself and then you can begin charging again. If the safety PCB in the charger is removed, the charger and BMS will work with each other so that when the BMS is balancing the cells at the top of the charge, the charger will turn off, and once the BMS allows charging to resume, the charger will turn on again automatically.

It very well can be that the charger is 'off' although still powered and needs to be reset which is why even if it is left connected even overnight that it is not working as a charger to assist with balancing it is only charging to the proper voltage and shutting off since it is being 'told' to shut-off.

Send me an email (so I know which customer you are...just in case I need to send you an RMA! :wink: ) and I will send you some info in the morning and will also post the information up here also in this thread for some clarification on what I am talking about.

Again .....I apologize if I am making no sense...I am tired!

 

[e-beach]

e-beach, have you modified your charger yet by removing the safety PCB from within the charger?

Jimmy..Jimmy where have you been man?

Haven't opened the charger...Might violate some sort of rule, regulation or policy or something. :wink: ...Makes me wonder why the charger was shipped set to 220 volts and the PCB thing is still in the way.... :?

Send me an email (so I know which customer you are...just in case I need to send you an RMA! :wink: )

I gave you a couple of calls today, but no answer. Guess you were out. But I got to tell you that I am not an account, never have been, never will be and don't like paperwork.

I like human contact when I spend my money.

I will try you again tomorrow.

Also, any other info you can post to clarify the situation will be appreciated.

Thanks for the late-night post.

PS, those battery holders still stink like an electrical fire...I had to go to All-Battery to get clean ones.

 

[e-beach]

Send me an email (so I know which customer you are...

Jimmie, I just checked your website and you don't have an email listed there....There is only an email for the accountant.

What is your email.

Thanks

 

[dogman dan]

Glad to see you here Jimmy, but do feel free to work this out in private messages.

I'm personally the most confused by the way the batts are dropping in voltage after the charger stops. Sure, dropping to 3.5v is normal enough, but all the way to 3.3v sounds pretty wierd.

It makes sense to me if the charger is not holding the battery at 43.8v long enough, and it's simply not really charged past 3.3v. Or if the bms is somehow wanting to draw the cells down to 3.3v.


Regarding the motor getting real hot, any hubmotor in 26" will do that if asked to climb 10-12%. When it gets hot enough, it will lose power and umph. So some of the problem could be the weather. Hot weather should perk up the battery though, so I don't think hot weather is bothering the battery any. Should have less sag than in cold weather.

 

[JimmieD]

Here is an excerpt from our DIY kit guidelines:

"Modifying the charger:

The charger has an automatic shut-off circuit board integrated in the charger itself. During charging, the BMS will shut-off charging if any cell is being overcharged (greater than 3.85V~3.95V), and once the cell voltage falls below the shut-off (aka recovery voltage) voltage, the BMS will allow charging to resume. Without the modification, when the BMS ‘tells’ the charger to turn off, the charger will turn off, but when the BMS ‘tells’ the charger to resume charging, the charger will remain off and will need to be disconnected from the battery and disconnected from the power source in order to reset itself to resume charging.

Modifying the charger will allow the charger and BMS to work together. The charger will charge, the BMS will ‘tell’ the charger to turn off, the charger will turn off, the BMS will allow the charger to resume charging, and the charger will then turn back on without having to reset it by unplugging from the battery or from the wall or other power source. This will also allow the BMS to properly perform the balancing function.

Remove the top two outside corner screws from the end plates of the charger and remove the top lid. There is a small circuit board that is located near the charger output, the fuse and the LED side. It is perpendicular to the main PCB and is connected with a 5 pin connector. This is what needs to be removed for the mod. The pins can be cut (be sure not to damage any of the other components), or, this is the method that I prefer to use, very carefully wiggle the circuit board back and forth being sure not to cut/wear through the existing wire insulation or from damaging other components and it will break off.

Once this is removed, replace the cover, and screws and the charger is ready to go!"

This is the ONLY modification to the chargers that we allow and still honor the warranty, and as long as no other components were damaged while performing the mod, the warranty will be valid. Any adjustments of the pots will void the warranty.

Haven't opened the charger...Might violate some sort of rule, regulation or policy or something. :wink: ...Makes me wonder why the charger was shipped set to 220 volts and the PCB thing is still in the way.... :?

We modify the charger and change the switch from 220Vin to 115Vin when we build the battery pack to ensure the charger and battery pack function together and properly before shipping, unless of course it is going to a country that has a 220V grid, then we leave it at the 220Vin. The modification 'procedure' is sent out with our DIY kits, but that is as far as it goes (went). Other than that, we really do not know how the charger is being used so we leave the charger 'as is' just as it was shipped to us.

Due to your post, we are now sending out this modification with all of our chargers that are over 1S, along with a reminder about checking the correct Vin switch depending on the power grid for chargers greater than 600W. All other chargers have automatic detection. So thank-you for letting us know a better way to assist the customers!

As for the smell on the spacer blocks, that is how we received them from Headway China, so not sure what had happened, but we will do a better job in the future.

I apologize about missing your calls yesterday, large shipments came in and we were pretty tied up with inventory. Great talking with you and walking you through this on the phone this morning.

 

[JimmieD]

Glad to see you here Jimmy, but do feel free to work this out in private messages.

I'm personally the most confused by the way the batts are dropping in voltage after the charger stops. Sure, dropping to 3.5v is normal enough, but all the way to 3.3v sounds pretty wierd.

It makes sense to me if the charger is not holding the battery at 43.8v long enough, and it's simply not really charged past 3.3v. Or if the bms is somehow wanting to draw the cells down to 3.3v.

Hey dogman, thanks but wanted to just share with everyone about KingPan charger mods to help others in the future that may have this issue and are scratching their heads. The 3.5V and 3.3V scenario is what grabbed my attention too and I then knew at least where to start with the trouble shooting, that safety PCB that is put into the charger to protect a battery that does not have any type of balancing circuitry (ie BMS, DB8, etc).

So now will wait and see if this takes care of e-beach and his battery!

****Remember, we can only speak for ourselves with this mod as far as warranty issues go!

 

[dogman dan]

It does sound to me, like he doesn't want that pcb in there for his battery system. That's why it wouldn't continue to balance and charge when left on the charger. The charger was not restarting as it needs to with a bms. I bet it will not stop so soon now, and more completely charge the battery.

I just hope there is nothing going on with the bms as well. How many times have you had it be the case that you had multiple problems to troubleshoot? Way too many times for me.

Thanks for helping, and making us aware of it for any others that may have the same charger that may ask us.

 

[dnmun]

ping has a thread on it from 2 years ago.

 

[e-beach]

Modifying the charger will allow the charger and BMS to work together.

Jimmie, thanks for picking up the phone today and walking me through the process. It seems to be working.

Next time I buy a charger I will be sure to ask just what part of the pcb I should tare out of the box. :lol:

I went for a ride and then put it on the charger about an hour ago. I pulled the charger and tested the cells. 11 are reading between 3.59 and 3.61 volts. The 12th is reading 3.44 volts at the moment. I will leave it on the charger for a while longer then check it again to see if that cell comes up to 3.59+ volts.

Thanks to everybody who contributed to this thread.

Dogman, you were right it was the charger.
dumun, you were right is was a lipo charger, until I tore the part out.
dand214, yes there is a pot to turn up the voltage. In my case it is vr2 (very-able resistor 2) but, I am going to leave it alone so I don't void the guarantee. :wink:
amberwolf posted the fix on the Endless-sphere wiki.

There is a lot of competency on this board! 8)
Thanks again!

 

[dnmun]

leave it on the charger until every cell measures at least 3.65V while charging, then you can remove it. it is gonna take a long time because they left no headroom in that charger but the headway BMS is very accurate so eventually i think you can get all of them charged.

may take forever. but they don't allow you adjust your own charger.

 

[e-beach]

may take forever. but they don't allow you adjust your own charger.

If I do ever get to the point that I want to turn up VR2 on my charger, what is a maximum I should over-volt to, providing the board can do it?

 

[amberwolf]

I wikied a link to this post
http://www.endless-sphere.com/w/index.php/Chargers_Modifications_Listing
but if anyone is willing to create a full article in the wiki on the modification (or any of hte others linked there), it would be appreciated.

Here is an excerpt from our DIY kit guidelines:

"Modifying the charger:

The charger has an automatic shut-off circuit board integrated in the charger itself. During charging, the BMS will shut-off charging if any cell is being overcharged (greater than 3.85V~3.95V), and once the cell voltage falls below the shut-off (aka recovery voltage) voltage, the BMS will allow charging to resume. Without the modification, when the BMS ‘tells’ the charger to turn off, the charger will turn off, but when the BMS ‘tells’ the charger to resume charging, the charger will remain off and will need to be disconnected from the battery and disconnected from the power source in order to reset itself to resume charging.

Modifying the charger will allow the charger and BMS to work together. The charger will charge, the BMS will ‘tell’ the charger to turn off, the charger will turn off, the BMS will allow the charger to resume charging, and the charger will then turn back on without having to reset it by unplugging from the battery or from the wall or other power source. This will also allow the BMS to properly perform the balancing function.

Remove the top two outside corner screws from the end plates of the charger and remove the top lid. There is a small circuit board that is located near the charger output, the fuse and the LED side. It is perpendicular to the main PCB and is connected with a 5 pin connector. This is what needs to be removed for the mod. The pins can be cut (be sure not to damage any of the other components), or, this is the method that I prefer to use, very carefully wiggle the circuit board back and forth being sure not to cut/wear through the existing wire insulation or from damaging other components and it will break off.

Once this is removed, replace the cover, and screws and the charger is ready to go!"

This is the ONLY modification to the chargers that we allow and still honor the warranty, and as long as no other components were damaged while performing the mod, the warranty will be valid. Any adjustments of the pots will void the warranty.

Haven't opened the charger...Might violate some sort of rule, regulation or policy or something. :wink: ...Makes me wonder why the charger was shipped set to 220 volts and the PCB thing is still in the way.... :?

We modify the charger and change the switch from 220Vin to 115Vin when we build the battery pack to ensure the charger and battery pack function together and properly before shipping, unless of course it is going to a country that has a 220V grid, then we leave it at the 220Vin. The modification 'procedure' is sent out with our DIY kits, but that is as far as it goes (went). Other than that, we really do not know how the charger is being used so we leave the charger 'as is' just as it was shipped to us.

Due to your post, we are now sending out this modification with all of our chargers that are over 1S, along with a reminder about checking the correct Vin switch depending on the power grid for chargers greater than 600W. All other chargers have automatic detection. So thank-you for letting us know a better way to assist the customers!

As for the smell on the spacer blocks, that is how we received them from Headway China, so not sure what had happened, but we will do a better job in the future.

I apologize about missing your calls yesterday, large shipments came in and we were pretty tied up with inventory. Great talking with you and walking you through this on the phone this morning.

 

[Holocene]

Your SLA's climb better because they will put out 5C discharge for a few minutes. With a 12Ahr pack, that's 60 Amps available to your 30 amp controller. You'll only get 5 Ahr's out of them used this way, but you're only climbing at 10% for a minute!

Your Headways are only 1.5 C discharge, maybe even only 1.0 C so with a 15 Ahr pack, you've got max 22 Amps and maybe as little as 15 Amps available to the controller. So no oomph to climb vs. the SLAs.

Solutions? First get a Cycle Analyst. Then consider RC Lipo. It'll give you better than 5 C discharge, and is still lite. Want to buy more Headways? You'd need 30 Ahrs to match the short-term power potential of SLAs. So the weight and expense has creeped up again.

Most people here would say 'Go Lipo'. But it's not your charger or low voltage. It's low C rate.

Cheers,
Holocene

 

[e-beach]

Your SLA's climb better because they will put out 5C discharge for a few minutes.

5c.....Really!!! That explains a lot though.

Your Headways are only 1.5 C discharge, maybe even only 1.0 C....

I went for a run on that hill this morning and got 2/3 the way up. That is as good as I have gotten so far with this pack so 1.5C is probably a good number.

Solutions? First get a Cycle Analyst.

That is moving up on the list, but at the moment it is not in the budget.

Then consider RC Lipo.

I don't like the flame factor.

Want to buy more Headways? You'd need 30 Ahrs to match the short-term power potential of SLAs. So the weight and expense has creeped up again.

OUCH

Thanks for the info. I ride that hill almost every day. But I am into the Headways for the moment so I will just petal a bit more the I used to. I will make-it-up by just not pedaling at all for the other 20+ miles of the ride. :lol:

Cheers,