onboard charging/balancing solution

P

powersupply

100 W
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Apr 14, 2013
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235
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Santa Monica
Hi all,
I am considering LiFePo4 instead of 4x SLA batteries on my scooter.
I also am getting 2 SmartBMS (set to 12s lipos, which I probably need to reprogram somehow).

Having plenty of space -weight is not a problem, too- I want everything to be on the bike and as easy to operate as can be.
I am willing to invest much time and effort to get it to be "plug it in and forget about it", for the least cost.

Right now I am stuck with the charger, I read about putting isolated (meanwell) PSU in series, but they are not CC/CV from what I understand.

What voltage do I need? 16x4.2=67.2?

Or do I need some headroom?

I do have basic knowledge of low voltage and power electronics.

Thanks in advance for your kind input!


Long version:
After reading the many posts on what chemistry, charging and balancing I am more confused than ever.
So I am turning top this great board for help.
It says disconnect the balancer or it will bleed the battery to death, then there are (expensive) chargers with balancing built in, and then I see batteries on ebay with the balancer acrually built into them (what happened to bleed to death?)
So I understand that some balancers probably draw more than others? Then there are chargers where you'd need to plug the batteries into (not possible in my setting) and disconnect them after charge.

Then some balancers you'd need to connect between the bike and the battery (or put between battery and charger for charging?)

Then the chargers: CC/CV, got it, but balancing AFTER it charged? Basically discharging the pack in a way? I read about active vs passive, but active are sooo expensive and even they are lossy.

I have no need for ultrafast charging, in fact, I prefer slow (less than C) charging.
16s LiPo/15Ah overnight (10-12 hours) is totally fine.

And trickle charge (or not with LiPos?) while it is connected, so it is fully charged when I need it.

The SLA thing was really easy, you'd just plug in the 3 prong plug and that was it!
Will that be possible with LiPo's, too?
 
powersupply said:
The SLA thing was really easy, you'd just plug in the 3 prong plug and that was it! Will that be possible with LiPo's, too?
Click to expand...

Lipo is a dangerous battery chemistry. People have lost their bikes and even their entire homes from fires caused by mishandling lipo batteries. Personally, I'd say the answer is absolutely not when using lipo, to your question. There are at least two ways you can make a lipo light on fire. Over charging lipo and damaging lipo. If you could be exceptionally vigilant and prepared for a lipo battery fire, I'd say that you could use it, but you want something that is extremely simple, plug and play, I suggest going with lifepo4. If you need a higher C rating, go with a123 cells. Pre-made lifepo4 packs would probably suit you best.
 
16s is an oddball config. 67.2V fully charged. First thing to do is make sure your controller can handle that voltage. Most 48V controllers are limited to 63V because of using 63V caps. Putting 67V into them may blow them. Check your fets too and make sure they can handle the voltage. With the higher voltage to you 48V controller it's likely some of the features won't work properly too, like regen or eabs braking. These can be made to work again by raising LVC if you know how. Default LVC for 48V controllers is usually 42V. Perfect for 12s lipo. Not so good for 16s. But as long as you know what you're doing 16s should give you a good boost in power and speed.
And I'd never leave lipo charging unattended without being awake and close by or having it in a fireproof place.. That's a recipe for disaster.
 
If you want ease of use in a vehicle, go with Li-Ion. LiFePo4 are too heavy and require a strong balancer.
The easy plug and play solution with a simple bulk charger, you want, is Li-Ion. Look into Sony's Konion cells.
 
The odball voltage/configuration is due to the given 4s hardcase packs.
12s are too low. so I went with 16s.

Yes, I prepared my controller already, it uses 75V and 100V caps so it is borderline ok. FETs are also ok.

http://endless-sphere.com/forums/viewtopic.php?f=2&t=53324

I might use LiFePo4s.


I am just looking for a way to make everything stationary connected to the bike.

Charger, balancer etc.

Thanks!
 
Plug and forget lico? I don't. After 3 years playing with that stuff I still don't trust it. I watch it close. I love the idea of removing the packs from the bike, and seeing if they are puffed, or all hot, or all stinky, every ride. Then I charge them in a place that's somewhat fire resistant. And store them in a "bunker".

If you are not doing that, then you need to make the battery box superb. NO WAY for the packs or wiring to rub holes and start shorting. Make it extremely tight around the packs so they don't move and chafe, and have tidy wiring. You have the hard packs, but the packs must still not bounce around. Inside the hard case, it's still possible to have a cell chafe a hole if they bounce around in the box all day.

If Methods still has any of the "complete lipo protection system" left, that is what you wanted. Methtek is the E address.

You can't make a 12s bms run 16s. But you can run 12s with them. You'll have to find a 4s bms to go with the last set of packs.

Once you get the bms set up, it will bleed down the battery slowly, so don't set it aside for the winter with the bms disconnected, and recharge a bit before riding if left a few days.

You can use any lithium charger that has adjustable voltage output. You'll need to turn up the volts, and then likely turn down the amps just a bit, so the wattage is not too high for the unit to last.
 
You might go get a cheap remote thermometer, and put the sensor in the battery pack. then you'd get a readout on the dash of the battery temps, and know if your pack was about to burn your garage down. As a pack gets discharged below 2.5v, it will get hotter and hotter. That would help clue you in.

Before finalizing your pack, sort out any packs with a bad cell. That's the single most important safety thing with lico. So watch it close the first 20 cycles or so, and sort out the ones that show a problem.
 
Thanks for that, dogman.

I plan to use the 2 SmartBMS to each balance 8 cells.

I also wanted to be able to check on those cells with a CelLog, as explained here:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=53613

I would disconnect the - from the batteries through a relais from the charging power, from what I read they go high Z when not powered.

What I still don't get is the BMS thing.

Do the BMS need to be disconnected after charging?
Because I read that it is after the charging when they do their balancing act.

Would I need to reconnect the charger again after the cells were balanced?

No problem with that per se, could use a timer with those notches to turn everything on/off
timer.jpg

And of course the charger itself, how do I mod the meanwells to operate as CC/CV?

The bike is outside on concrete.
 
Sounds like you want a plug an play charging solution for 16s. . I don't use or like any of the BMS's for lipo, but that's one solution. Get a 16s bms for lipo and wire it up. Then get a 75.2V charger for it.
http://www.bestekpower.com/592v16spcmbmspcbforli-ionli-polymerbatterypack/
Chargers
http://www.bmsbattery.com/18-alloy-shell

And stop using the battery pack when it gets to 56V. Don't run it down til the BMS shuts off at 3.0 volts per cell. You'll end up killing it faster.
http://www.ebay.com/itm/Waterproof-Digital-Voltmeter-DC-15V-To-120V-Red-Led-Voltage-Digital-Panel-Meter-/170846310527
 
Couldn't I just use the 2 SmartBMS I bought already, in series?

This is what I'll be getting:
http://www.bmsbattery.com/smart/330-lifepo4lithium-ion-smart-bms-for-513-cells-in-series.html

From what I read they can be programmed to any LVC (let's say to 3.5V), I would use that trigger/alarm.

Worst case, with 2 relais, I could split the 16s into two paralell 8s (at their ultimate + and -) , introducing losses and extra wiring.

I could not find any documentation on the my mentioned SmartBMS, just some jpegs so I still don't know if I can keep them hooked up to the batteries at all times (anybody?).

The longest the bike would be sitting is 2 weeks. (I read about long term damage of charged LiPo cells)

The bike will be used on a daily basis.
 
You bought a lifepo4 bms. Lifepo4 charges to 3.65v per cell. Won't work with lico, which charges to 4.2v per cell.

Try to sell the lifepo4 bms, and look into a lico bms.

I think learning about lico is done quickest by doing it the more tedious way. Get an RC charger that will balance your packs, and a cellog. Run your pack, and check on it with the cellog. Learn how it behaves, make mistakes, but catch them before your burn the house down.

Later on, if you want to take up bulk charging lico, you will know a LOT more about it from having been a human bms for a time.

You want to buy lipo, plug it in and not worry about it much. Buy some good house insurance bro, and I hope you don't have children or grandma in the house.

Get some nice safe lifepo4. You already have the bms for that.
 
My understanding was that the SmartBMS I'll be getting uses the OZ890 from O2 Micro, which is programmable to the attached chemistry.
I did thorough research on that, but being a newbie/noob, I still might be wrong.

I truly don't wan't to go through the tedious way as you mentioned it.
Just getting to the batteries in that scooter is a 1/2 hour job.
RC chargers are way too expensive and with 16s you'd need to manually disconnect them, so again, a no-go.

I don't understand the phobia with LiPos, with Talking the Heads off about "burning down the house".

A lead acid 12V battery could do the same, and probably has.

It is all about correct engineering and design, one needs to implement mechanisms which prevent disasters in a case of any failure.

Anyhow, considering that I don't know how to serialize the 2 BMSs, and if they can stay hooked up at all, and the many variables I have not found any answer to, yet, and given that I do have a 54V CC/CV charger which I could tune to LiPo, I am thinking of using just 12s for now, and see how that works.

Maybe this is a compromise I should take at this point....






dogman said:
You bought a lifepo4 bms. Lifepo4 charges to 3.65v per cell. Won't work with lico, which charges to 4.2v per cell.

Try to sell the lifepo4 bms, and look into a lico bms.

I think learning about lico is done quickest by doing it the more tedious way. Get an RC charger that will balance your packs, and a cellog. Run your pack, and check on it with the cellog. Learn how it behaves, make mistakes, but catch them before your burn the house down.

Later on, if you want to take up bulk charging lico, you will know a LOT more about it from having been a human bms for a time.

You want to buy lipo, plug it in and not worry about it much. Buy some good house insurance bro, and I hope you don't have children or grandma in the house.

Get some nice safe lifepo4. You already have the bms for that.
Click to expand...
 
I'd have sworn that yesterday I clicked on your link to a lifepo4 bms. I thought I had read that you had that bms in your hand.

Sometimes I read stuff completely wrong, and screw up peoples threads. I'm sorry about that, West Nile Virus really screwed me up two years ago. Some days I'm just really stupid when overtired.

Anyway, some of us just aren't going to say, go ahead and ignore lico packs, and park in the garage next to the baby's bedroom, or the apartment.

Bet you never saw this picture. This is what a large lico pack looks once it goes off.

I have held a lico pack in my hand that was too hot to hold on to. Shrink wrap all melting off, and the cells puffed till it looked like a catchers mitt. That was because one connector unplugged during a ride, discharging that pack to 0v. Just a very simple fault, but had I rode into the garage and parked that bike and walked off, I'd be typing this from a rental house.

It's just not like having a little thing go wrong with lifepo4. That's all. When lico goes off, it goes OFF.

Get your proper BMS for lico, and a good "smart" lithium charger to go with it. But then, VERIFY that all is well. Pack that lico into the scooter well protected so the hard packs don't bounce around in there, and make your wiring neat and tidy, and IMPOSSIBLE TO HAVE A PACK DISCONNECT ITSELF. With a thermometer in there, anything going wrong will give you enough warning to not park the thing where it will burn the house down. Have a secondary port for cell voltage monitoring. That way you can plug a cellog in anytime, and see that your bms is still working properly.
 
I'd have sworn that yesterday I clicked on your link to a lifepo4 bms. I thought I had read that you had that bms in your hand.

Sometimes I read stuff completely wrong, and screw up peoples threads. I'm sorry about that, West Nile Virus really screwed me up two years ago. Some days I'm just really stupid when overtired.

Anyway, some of us just aren't going to say, go ahead and ignore lico packs, and park in the garage next to the baby's bedroom, or the apartment.

Bet you never saw this picture. This is what a large lico pack looks once it goes off.IMG_0196.JPG

I have held a lico pack in my hand that was too hot to hold on to. Shrink wrap all melting off, and the cells puffed till it looked like a catchers mitt. That was because one connector unplugged during a ride, discharging that pack to 0v. Just a very simple fault, but had I rode into the garage and parked that bike and walked off, I'd be typing this from a rental house.

It's just not like having a little thing go wrong with lifepo4. That's all. When lico goes off, it goes OFF.

Get your proper BMS for lico, and a good "smart" lithium charger to go with it. But then, VERIFY that all is well. Pack that lico into the scooter well protected so the hard packs don't bounce around in there, and make your wiring neat and tidy, and IMPOSSIBLE TO HAVE A PACK DISCONNECT ITSELF. With a thermometer in there, anything going wrong will give you enough warning to not park the thing where it will burn the house down. Have a secondary port for cell voltage monitoring. That way you can plug a cellog in anytime, and see that your bms is still working properly.
 
After reading the many horror stories about fake and recycled lifpo4 I still might consider LiFePo4.
If I was 2 years earlier, then yes, I'd get some DeWalt etc A123s, but now...

A real track record about the degrading rate of current lifpo4s is not available yet (A123s excluded). Even brands like Headway are thumbed down here on ES.

Maybe in a few years, when lithium sulfide batteries become available and mine wear out, LiFePo4 become more affordable.

Thanks for warning me again and agian about the danger LiPos pose, I truly got that message, thank you very much!

Right now I am just concerned about the actual hookup of the SmartBMS to the charger and the LiPo battery I ordered already.

Lacking any actual manual of the SmartBMS and reading conflicting things here on ES regarding leaving the SmartBMS attached to the batteries at all times was the main reason to start this thread and ask for help about those specifics.
 
@ dogman:

What do you mean, when you say Lico? Any Li-Ion cells or LiPo? Maybe you could clarify.


@ powersupply:

If you want a carefree solution without the fear of burning your house down, necessity to use a BMS or having to take extreme measures, just go with the Sony cells and these worries will be over. There are so many points in favour of these cells, that - in my view - this is the only nobrainer, when building an ebike.
 
Sigh...
Ok then, lets rephrase this.

How do I hook up the mentioned SmartBMS
http://www.bmsbattery.com/smart/330-lifepo4lithium-ion-smart-bms-for-513-cells-in-series.html
to a charger and the CellLog and LiFePo4 batteries?

So it is plug and play basically.

This is a Vespa style scooter, with its batteries buried deep inside it, in its belly.
It takes way too long to get to the batteries and dig them out and hook them up to something.

So it must be a constantly hooked up solution. I could implement some relais here and there, but the only thing I will be able to connect and disconnect is the power to the charger itself!

Now that we use LiFePo4 and have this amazing buring down your house thing out of the way, could we please focus on that please?

For instance:
1) considering that the SmartBMS takes care of balancing, does the charger need to be CC/CV or can it be a simple stabilized power supply? And if so, at what voltage for 12s LiFePo4?

2) Can the SmartBMS stay hooked up to the LiFePo4 batteries at all times without interfering with their operation? (I am not concerned about 5 milliamps of drain).
For instance, will short fluctuations trigger some balancing procedure?

3) Does the charger/power supply have to be turned off after a while, considering that trickle charge is not required with LiFePo4s?

4) will the SmartBMS continue balancing the battery even after it has finished at some point, i.e. will it continue to drain the battery (again, up to 5mA are no problem)?

THESE are the questions I am REALLY seeking an answer to.

THANK YOU!
 
The key question is, whether the balancing current of the BMS is sufficient to keep the LiFePo cells balanced. I can't answer that, but the balancing current of the SmartBMS (withouth tweaking it with different resistors) is pretty low.

I do have a programming interface here, which I can lend you, if you want to program yours. You can also send your bms to me and I'll set you the values, you want, ... for free, of course.
 
hey PSU ;)

1) Yes, the BMS will shut down if the battery is empty and you connect a high power PSU. The current that rushes into the battery is too much, you need some kind of limiting (CC). If you use a lower power PSW like 250W then it might work since the PSU limits amps and though limits power, in fact that's what a CC/CV PSU/charger does

2) yep

3)nope, you can leave it for weeks without damaging anything

4) If you set the "idle balance register" to "1", it will behave as you describe.

Hope this helps.
 
About wiring up the BMS.

You have one + hookup for everything. Battery, charger and discharge (controller) They all go together.

The - pole is split three ways: one for battery, one for the charger and one for discharge. Depending on the version you bought, you'll have one charging fet and two or three for discharge.

Connect the battery minus first, then the balancer, then battery plus, and then the rest.
I've broken a few of those, so you might want to buy a spare one and be careful with it.
 
'What do you mean, when you say Lico? Any Li-Ion cells or LiPo? Maybe you could clarify".
Same. Robert, Bob, Bobbie.
Thinking to hard good buy a built plug and play battery for your scooter. Please tell us the voltage needs of your controller and it's amps demands. Yes both please.
 
Sorry, I still don't get it:

Is LiCo
1. Li-Ion: like the Sony Konion cells
2. LiPo: Like Turnigy cells
 
Thanks all for these informative replies!

Schwibsi , the SmartBMS schematic has the charger - go to a different pin than the battery -.
There are some FETs between the two - points.
But I can still connect it as you suggest?
Actually there is a shunt between motor - and BMS, too.
As mentioned, that's why I'm getting more and more confused.
Thank you for the reprogramming offer, I really apreciate it!
I was diving into that and also found Crossbreaks posts about this controller

BTW, the programmable oz890 controller I had linked to is now indeed gone from bmsbattery.com's website!!

Crossbreak, thank you really much for your reply!
1a) Thanks for clearing that up!
The charger I would like to use then is my SLA 48V charger (for the same scooter) tuned a few Volts up or down to suite the needs of the batteries.
As typical for SLA needs, it first charges with much A and then falls into a trickle charge mode.
So it is in a way quite similar to a CC/CV charger.

2) again, thanks!

3) that's exactly what I want/need.

4a) I am going to use the scooter nearly every day, longest downtime will be maybe a few days when it rains or so.
At max 2 weeks when on vacation or so.
So would the trickle charge setting of my charger be ok in my setup? Would I still need to reprogram it?

I truly want to recycle as much as possible, used parts from a dead UPS to enhance the controller (caps and FETs etc) .

But if needed, I would buy a CC/CV charger of course.


The controller needs/wants question:
It is a 48V brushless controller with hall sensors. I enhanced it to 75V and lower Ohm FETs.
The scooter comes originally with 4 x 18Ah(up to 22Ah) SLA batteries in series. It is advertised with a 750W motor, the federal maximum in the US for bikes.


Here is some info on the controller/scooter.
http://endless-sphere.com/forums/viewtopic.php?f=2&t=49287

http://endless-sphere.com/forums/viewtopic.php?f=2&t=53324


Thanks!!!!
 
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