Using SLA chargers for LiFeP04 batteries

[hulagun]

A 24v charger for lifepo4, or other lithium charger with adjustable voltage would be the thing. It will go to 0 current at the end, rather than a tiny trickle that might overcharge a cell if left long enough.

To clarify, if you had a bms, then the trickle would matter less. But you might have too low a voltage at the end to kick on the balancing of the bms.

Just go to ebay, and find a cheap lifepo4 charger in 24v. Should be one well under fifty bucks.

Thanks to previous posts including IIRC some of yours Dogman that is sort of where I already landed. But the problem is ebay sellers don't provide the specs of their chargers. And as far as "adjustable voltage" I don't recall seeing that offered in an inexpensive LifePo charger unless you mean a CC/CV charger.

What I *think* I need is a CC/CV 24v charger putting out about 29.6v/5A, and terminating (off) at around 28v.

This looks close - except no adjustable output and for some reason it says right in the listing "Not for use without BMS".????
http://www.ebay.com/itm/Bioenno-Power-AC-to-DC-Charger-5A-for-24V-LiFePO4-Batteries-w-GX16-Plug-/171049236996?pt=Battery_Chargers&hash=item27d3543a04

 

[dogman dan]

Yes, the adjustable voltage pot is not found in the cheapest chargers. The metal shell "kingpan" type often does have the pot. Those a fairly pricy 5 amps chargers.

Chances are, the cheap 2 amps plastic charger is set close enough to your voltage, if it's for lithium. If possible, look for one labeled lifepo4. In 24v and 48v, the limn and lifepo4 voltages match pretty good. In 36v, there is more difference between the right voltage for differing chemistries.

 

[DVDRW]

Using this 2,5A charger for Goldenmotor 10ah Lifepo4. Works great and its ~16$ . It should be not problem put these chargers in parallel while connected to battery.

 

[hulagun]

Thank you for all your patience with my noob questions.

Clean Republic did finally respond, they recommend 14v charge minimum (15v max, 10A maximum). They stated " No BMS" inside the bamboo case. My new batteries also arrived today, they are nice, light weight, and the cases are quite handsome.

I'm finding some chargers advertised that appear to be slightly nicer quality than the $20 2A plastic chargers on ebay. I'm looking at the $30-$50 range lifepo chargers from Ping and Stark and BiennoPower, which offer 4A-7A. Some may require I swap out the plug for a 3 pin GX16 plug to fit the scooter charge port. There are even nicer looking 5A, 7A, and 10A chargers available online, that are fused, fan cooled, and in aluminum housings. However these run $75-$130, and still have no adjustment pot.

Some new noob questions, assuming a CC/CV lithium charger is going to be used:
- what are the specific real world advantages of a 5A, 7A or 10A charger over a 2A or 4A charger?
- is it necessary to use a backup timer to fully terminate charging (once I determine how long that typically takes)?
- assuming I do not want to install an onboard watt meter, what is the best way to determine when to recharge?
- if a watt meter is vital, what exactly will I be looking for to determine when to recharge my (24v, 2x 12v-9ah) lifepo4 batteries?
- is there a bolt-on handlebar-mount affordable watt meter available?

Thx again.

 

[dnmun]

if they have no BMS then you can take them apart and rewire them all in series and then wire up a BMS to balance and protect them. it should be illegal for them to sell these imitation motorcycle batteries with no BMS.

hopefully nobody else will buy them.

 

[dogman dan]

5 amps would be the max you'd likely want to use on that size of battery, if for no other reason than the cost of the charger. Slower charging is said to stress the cell less, faster charging is more convenient but the charger costs more, somewhere there is a balance that meets your individual needs.

I don't see why you would need a timer with a charger that does stop. A lead charger slows way down, but does not completely stop. But some feel safer using a timer.

Determining when to charge is simple, if you discharged one watt, time to charge. In other words, don't try to go days to save a cycle. Charge whenever convenient, and get more cycles. The battery prefers the shallow cycle to the deep one. Very deep cycles tend to unbalance the cells.

There is a don't go below this voltage, so you can stop based on a voltmeter. It will look fine one minute, then dive off the cliff the next. So a wattmeter to anticipate when the voltage will dive helps a lot with lifepo4. With experience, you could tell when it's coming with a speedometer. By 3v per cell, you will need to stop. About 24v. Past that, voltage will drop like mad.

Cheapest wattmeters are the blue ones on ebay, about 15 bucks. Handle bar mounting them is a pain, either you hack the device, or run full power through the handlebars. Lots of wire.

 

[spinningmagnets]

I asked a couple of friends recently about using a common 12V charger for 4S LiFePO4. If running from 2.8V-3.8V per cell, 4S = 11.2V-15.2V

My cheap and robust 12V charger actually puts out 14.0V, and I don't know if it's adjustable to 15V. One of my friends recommended experimenting with a Meanwell 12V unit. Or even better, get paired Meanwells for 24V, adjust for 30V to charge an 8S LiFePO4 sub-pack?

Would this work? Could I charge two 24V sub-packs in parallel with a 24V meanwell set-up, then series them for 48-ish volts (16S LiFePO4)?

Also, is 2.8V-3.8V per cell the best operational range? (I never used LiFePO4 before)

 

[Gregb]

I am certainly no expert on Li batteries but have done a lot of reading and one thing seemed apparent that a standard battery charger is not really suitable. A L/A battery charge is a chemical reaction that is reversed by applying a reverse battery, i.e charging, mode. Li batteries have a totally different method of storing charge (they actually store electrons in a matrix is the best concept) and require a constant current charge for most of the charge cycle. A constant Voltage cycle is then applied that allows a gradual "topping off" of the cells, preferably via the sense leads to allow the cells to be balanced and charging to stop before the V exceeds 3.8V nominal. (the constant voltage limit) . It is possible to bulk charge cells just like a L/A battery but maximum storage will not be achieved. Not all cells in a typical L/A battery are balanced either when discharged but can be brought into a semblance of it by constant "trickle" charging. ( we used to, many many years ago, even put a battery into overcharge mode, until it " gassed" in an effort to bring low cells up to scratch. These were large glass open batteries for telephone exchanges) Li batteries cannot be treated this way as "overcharging" will damage/destroy them. So by all means use your L/A charger but it is unlikely your cells will achieve maximum capacity and if their critical voltage is exceeded you WILL damage them.
My two bobs worth

Greg

 

[EZgo]

Sorry for the slow reply to the new post's but I'm in central PA so I don't have much additional riding time on the Bamboo's. That said the 3 bikes I have in inventory that are using these batteries are still working as advertised. 2 of these are 36volt (3 12V) using stock E-BikeKit 36 V SLA Chargers & my regular bike running 60 volt (5 12V) using the proper LifeP04 chargers. ( 1 - 58.4 volt LiFeP04 charger & 1 - 14.8 volt)

If you have not already done so I would recommend purchasing a 24 volt LiFeP04 charger. ONLY because you have to buy one anyway & the price difference should be under $20. The only difference that I have both observed & read about is the way in which the 2 chargers cycle through the charge & the total output. A lot of the better SLA chargers have a trickle (float) charge which can be detrimental to the LifeP04 battery. Using the timer as you stated will eliminate that problem. SLA charges also put out slightly less voltage. Whether this can actually be felt or measured in actual use I can't say because I've never done back to back comparisons.

However, at the moment I am replacing the batteries on a customers older 24 volt Currie Electro Volt. This Currie used 2 12 volt 12 amp SLA's. It seems the newer ones use 10 amp sla's. I was going to put 2 of the 12 volt 10amp bamboo's in it but instead used a 24 v 10 amp pack I had built this spring using 8 - 3.2V Headway 38120S 10Ah 10C cells with a BMS board. I did this for a couple of reasons.

1 - I think the Headways pack more of a punch.
2 - I'm still unsure of how long these bamboo's will last without a BMS.
3 - I was willing to let it go at the same price as 2 of the Bamboo's.

The Currie 24 v sla charger as per my meter puts out 26.2 volts. My RideKick 24 v sla charger puts out 27.8 volts The Bamboo chargers put out 14.4 or 28.8 volts if used as a pair. The LifeP04 charger for my Headway pack puts out 29.4 volts. I will offer the LifeP04 charger to my customer for $25 & suggest that he will be better off with LifeP04 charger because of the higher voltage. Will 3.2 volts make a difference? I don't know but if our Arctic weather breaks in PA I will try to do a side by test. If I do I'll let you know.

The bottom line on the Bamboo's boils down long term testing & price. Until C.R. puts a BMS in these OR guarantees them to last at least 1,000 cycles when used in multiples or gets their selling price down I can't recommend them. By the time you wire them together & then buy the appropriate charger your not saving enough money to warrant the unknown life expectancy. That said they are a neat little package & easy to work with. If I can continue to buy them on Ebay for $85 or less DELIVERED I probably will.

Matt

 

[hulagun]

Thanks all!

Based on emails from Bioennopower, and on other info I read on the web, I ordered a Bieonnopower 24v - 5A charger for Lifepo4 batteries with a GX16 aircraft plug that fits my scooters charge port. Just got it today, and already have it topping up my scooters Clean Republic bamboo batteries. For $55 incl. shipping, it looks to be a high quality aluminum boxed charger with fan cooling.

I did consider using 2 of the cheaper ($20) Clean Rep. Lifepo4 smaller plastic chargers, which would have provided 29.6v if re-wired properly... but for a few more $$ I'm hoping the Bioenno units 29.2v output will work just fine.

 

[dnmun]

i just got a BMS from one of those bioenpower packs and i discovered there are no shunt transistors to allow the pack to balance. i have never seen any manufacturer sell a BMS with no shunt balancing transistors. i was just gobsmacked when i saw it. no way for the pack to balance. almost as bad as those clean republic fake motorcycle batteries.

 

[hulagun]

Well, it's not looking good.

I received my CR Lifepo4 batteries OK, and my Bioennopower charger arrived, too. The stuff all looks great. I popped the batteries into a Razor e300 scooter to test them out. The batteries checked out at 13.4+ volts or each, so I didnt see the need to charge immediately. They had near 27v when in series. Soon as I took the scooter outside, the neighborhood kids all wanted to try it. They spent about a half hour taking turns going back and forth on my block. I figured it would be good to cycle the batteries and then do a full top-up charge with the new charger. The last kid to ride it said "hey it just ran out". I didn't think much of it, just assumed it was time to recharge.

All went well, the charger appeared to work fine, and at 4 hours the green LED came on indicating the charger had terminated (fixed setting at 29.2v). I unplugged everything and went off to bed.

Checking it today, the scooter was dead as a doornail. I opened it up and check all connectors and found nothing bad. The batteries test at near 21v though. One was 11.8v and the other 8.9v or so. I replugged in the charger and the light showed green. Wierd... with those readings, it seems like it should show a red LED and the fan should come on.

I took the batteries out and clipped them individually onto a SLA 12v charger. It seemed to be working, the 11.8v battery came up to 13v. The other battery came up to 9.1v after sitting a bit, but the SLA charger wouldn't initiate charging it. It seemed to lose voltage on the SLA charger.

I've sent emails to Clean Republic and to Bioennopower asking for some advice and tech support. I have a feeling I just burned a bunch of dollars, though. Hopefully I can salvage something here...

Yes I'm a noob, but voltage is voltage. What am I doing, or have I done, wrong?

Thanks for any helpful advice.

 

[dnmun]

you were bound to ruin it anyway so you really didn't do anything wrong. why don't you post up a picture of the battery after you cut off the top and measure the voltage on each of the cells. do you know how long they ran it at full power?

 

[hulagun]

you were bound to ruin it anyway so you really didn't do anything wrong. why don't you post up a picture of the battery after you cut off the top and measure the voltage on each of the cells. do you know how long they ran it at full power?

Thanks, dnmum, I did read your dire warnings but the horse was already out of the barn. and I meant to ask you, what is a "fake motorcycle battery" exactly? There are photos of one of these Clean Republic batteries opened up by someone else, in the early posts on this thread. If Clean Republic doesn't want mine back, I'll probably give them to a friend who enjoys playing with discarded batteries way more than I do.

I watched the kids ride back and forth for at most 25 minutes. Probably less. They had a great time and it seemed to run fine.

 

[dnmun]

with no LVC protection they are bound to over discharged or overcharged. but the controller LVC would have cut off the discharge so some of the cells inside the cases may still be ok. some may be damaged from discharging too low, but even then you can salvage the good cells and make a battery from it and add a BMS to protect it and go from there.

 

[Gregb]

If you don't have a BMS then you really need to buy a BVM-8s for a 24V system. Overdischarging is probably worse than overcharging. This little meter has a built in alarm system including visual and audible indication of a the low voltage limit you set. If the batteries don't have sense wires you will need to install them. I use it on my bike to great effect.

 

[dogman dan]

Well that was a great example of how to potentially ruin a brand new battery. Lifepo4 has a very flat discharge curve, so it seems like it's pretty full when it's not.

You ended up severely unbalancing the pack with a deep discharge on half charged new cells, but you might be able to salvage it with a balancing charge. Hard to do though, the way they build those packs.

Hopefully you didn't ruin the cells too much, but you might have.

 

[EZgo]

I took the batteries out and clipped them individually onto a SLA 12v charger. It seemed to be working, the 11.8v battery came up to 13v. The other battery came up to 9.1v after sitting a bit, but the SLA charger wouldn't initiate charging it. It seemed to lose voltage on the SLA charger

A lot of chargers have a low voltage / safety shut off so they can't accidentally spark when they are not hooked to anything & or shut of a low voltage.

Wire your bamboo's in parallel ( 2 batteries 12 volts) & charge them. This will allow the charger to kick on. After they are wired together check the voltage. Connect the charger & recheck them. Is it higher? Assuming it is let them charge for a few hours together, the goal is to get them to 12.8 or above. At that point you should be able to properly charge them with the Lipo charger

DON'T GIVE UP! I have a lot of these batteries. I too am unsure of how these things will last but my oldest ones are approaching a year & I have yet to have a failure.

dogman is the most pessimistic person I have met in this forum. He's NOT WRONG, just negative. He's been shorted out 1 to many times.

Worst case you're dealing with Clean Republic in the USA. Explain the problem & ask them to send you 2 fresh batteries FROM THE SAME LOT! Tell them that your friends from Endless Sphere don't think very highly of these batteries & you would like to prove them wrong.

Definition of "Motorcycle Battery" How dogman describes any small 12 volt battery that is to be used in a conventional 12 volt starting system.

Read "Staring System". It has very different characteristics from what we are attempting to use them for. Look at my pics on page 1 of this post. See how they are snugly sitting inside an expandable foam insulation. That & the lack of any extra electronics means they will take a pretty good physical beating. As a 12 volt starter battery & probably even in a UPS they will last a long time.

Knowing all of this I'm still willing to experiment with them for the sake of cheap & easy e-bike power. If you can get better than lead acid acid power at 1/4 th of the weight it boils down to overall value. If you can get LifeP04 performance & at least a 500 cycle life for 60% of a BMS supported battery it's probably worth it.

For what it's worth. When I get a new bamboo I hook up a 55 watt 12 volt halogen bulb & a meter & plug it WHILE I'M WORKING IN THE SHOP so it can be monitored. They all come through with a 12.4 through 13.1 volt charge on them. Run them down to 11 volts. WATCH CLOSELY !!! WHEN THEY HIT 12 VOLTS THEY START DROP LIKE A STONE. I then use one of their 14.8 LifeP04 charges & bring them up to max which is as per my muti-meter 14.9 or 14.77 with my Watts Meter. If you want to test them again & I always do, using 1) 55 watt 12 volt halogen it should take 1) 12 volt bamboo 1) hour to discharge from 14+ volts down to 12 volts & another 10 min. or so to get down to 11 volts. DON'T GO BELOW 11 VOLTS as you can damage the battery pack.

FINAL NOTE: THERE IS NO WAY TO CUT THIS PACK APART TO A POINT WHERE YOU CAN CHARGE THE INDIVIDUAL CELLS UNLESS YOU HAVE NO INTENTION OF PUTTING THEM BACK INTO IT'S ORIGINA. BOXL. ALSO... ONCE THE PLASTIC COATING IS SCRAPED THROUGH AS IN MY PICTURES THE METAL CASING IS NOT ISOLATED FROM THE GROUND ( - ) I.E. you can get a reading up to 3.3 volts between any 2 battery casing's & up-to the total pack voltage from the ground ( - ) terminal & one of the battery casing's.

Hope this helps. Email me direct or call me if you need more info.

Matt
ezgo-now.com

 

[hulagun]

Matt and all thanks for all the advice pessimistic or otherwise. It is easing things.

The second battery that seemed to be OK on the SLA charger, suddenly decided to drop to 0.01v. Maybe at 13.6 v the charger went into a float cycle and that somehow caused this? So confusing!

Bioennopower wrote back on Sunday night (amazing service from them so far) and said "If the setup is not working out, you can ship the unit back and we can provide a refund". Before throwing in the towel and returning the charger, I decided to wait and see what Clean Republic said.

Today Clean Republic wrote back this "after talking with our production manager, we believe that the battery that was reading 9.8v was defective and we will ship a replacement today. Sorry for this inconvenience. Hopefully this new battery will get everything up and running as it should. Thanks!" They included what looked like a receipt indicating that a new battery had already been shipped to me. WOW This is unexpected.

I immediately wrote back to Clean Republic telling them I preferred to start fresh with 2 NEW batteries from the same lot (per Matt's advice), and that I would be happy to pay for the second battery. I also told them I'd attempt to save the first pair of batteries by charging them in parallel (also per Matt's advice). I await a response.

Will post updates. Thanks again!

 

[dnmun]

this thread is totally full of really disastrous misinformation. i tried to explain how you could see if any of the cells are still ok, but it was a total waste of time.

 

[hulagun]

this thread is totally full of really disastrous misinformation. i tried to explain how you could see if any of the cells are still ok, but it was a total waste of time.

dnmun,

Sorry you feel that way. But your posts haven't been detailed or timely, so your explanations have not been much help.

Other people have successfully used these batteries in the same series 24v manner I have, without problems, so it's not like this set-up can't work. Clearly I'm either doing something wrong, or I was sold bad components. Or both.

OR there's something else you think but you haven't been real clear on (other than saying a BMS is a requirement, and everyone else here is misinformed or wrong).

Could you be more specific with what you want to say here?
Thanks!

 

[dnmun]

i already told you to cut open those boxes and measure the cell voltages. you have no idea how badly damaged they are until you measure.

 

[dogman dan]

At least you have some experience with these particular batteries EZ go. I don't.

Do I get pessimistic when people take a half charged new battery and hand it to kids to play with? I guess so. It's not exactly my recommended new battery break in process.

I hope you did no permanent damage, but cannot say you didn't. Discharged deep enough to have the chargers refuse to start is a real bad way to begin, in my pessimistic opinion.

If you get sent new batteries, I suggest you charge them before using them this time at least. You also need a way to know when to stop discharging. It would appear your low voltage cutoff is plenty low enough to allow over discharge.

 

[hulagun]

If you get sent new batteries, I suggest you charge them before using them this time at least. You also need a way to know when to stop discharging. It would appear your low voltage cutoff is plenty low enough to allow over discharge.

Yeah apparently I screwed up, thanks. I kind of assumed that already, you may have noticed. I am a noob after all. OTOH it's not like I just dove in blind. Reading up on the topic extensively beforehand I saw no dire warnings posted about having to top up new LifePo4 batteries prior to use. Nor receive any instructions with the batteries (at all). One reason I chose Life_Po4s was for longer run time between charges. These metered at +26v when I installed them, so I ran the scooter to see how they worked. The kids saw me and got excited and it made me happy to see them having fun with it for like 20 minutes maybe. No, I didn't expect 25 minutes of light use (level ground) would deplete new LifePo4 batteries enough to damage them.

Is it possible that one battery had a flaw or internal short, caused by vibration, causing an over discharge, taking out both batteries? I have no idea, which is why I asked here on the forum. Clean Republic seems to think it could be a bad battery.

Looks like I am going to end up with 2 new batteries, and start the whole process over.

So, as far as "stop discharging", is there a solid and simple way to know when to do this without spending $165 for a Cycle Analyst? To your point about NOT running full power up to the handlebars and back, I was hoping for something more basic - akin to an LED at the handlebar that flashes at a preset voltage... say 11.5v per brick or 22.8v net or something. I also have a small matchbox size LED monitor that shows voltage in numbers, would that help? I don't have a way to house or mount it but could make something. Also, the controller is connected directly to the charge port, using very small gauge wires. So it occurs to me that it may be possible to connect (small gauge wiring) here to monitor battery voltage.

 

[dnmun]

no, there is no way to protect the battery unless it has cell level voltage monitoring through a BMS that can shut off the discharge before the cell is over discharged. that is why the salesman's claim that you can use it down to 11V or whatever is disinformation. you do not know anything when you measure the voltage of 4 cells in series. it can be 11V, with three cells at 3.5V and one cell at .5V and in the case of your situation where you ran it down to 30V before the controller LVC shut it off, that would be an average of 10V for every 4S so the average of 2.5V would leave you with most of the little boxes having cells that are over discharged because the lifepo4 is inherently outa balance when in use. if they sit for long times before they are sold, the self discharge can have already drained one of the cells to below the 2V limit already so charging and balancing them is impossible. even before it was used under heavy current for a long time. that is why some of the cells are now dead.

they should not be able to sell these batteries without a BMS to protect them. it was inevitable that you would kill it because there is no way to balance the 4S string. that is why the BMS was developed so that people who know nothing about batteries cannot kill them by accident.