Using SLA chargers for LiFeP04 batteries

Batteries, Chargers, and Battery Management Systems.

Using SLA chargers for LiFeP04 batteries

Postby EZgo » Sat Jun 08, 2013 12:58 pm

It's a great day for an e-bike ride. This is a charger question.

I have been testing & using 12V 10Ah LiFePO4 (Bamboo) Batteries from Clean Republic with positive results.http://www.electric-bike-kit.com/lithium-12v-lifepo4 sla-replacement These are a 12V 10 amp SLA replacement battery. They are the same size as most of the 12V 9 to 10 amp SLA batteries that you can buy anywhere. I plan to post my results about these batteries here at a later date. It's a fine battery. What I'm using it for is to build competitively priced 36 & 48 Volt battery packs for my bikes. "Competitively Priced" is the operative word here. I have been buying these from CR on EBay & so far have been getting them delivered to my door for an average price of $84.00 per 12V battery. These batteries however do not have any type of BMS inside & does not come with a charger unless you order the optional 14.8 V 5.0 for $19.00. http://www.electric-bike-kit.com/batterycharger.aspx According to CR charging them with a SLA charger is fine. *** (SEE BOTTOM of page for more info)

So my 36 & 48 volt packs are currently being charged with SLA chargers which seem to work fine short-term. My question is what if anything does using a charger designed for lead acid batteries do differently than a comparable LiFeP04 charger? i.e. Voltage, balancing cycles, etc.Through this forum, battery university & other commercial sites I have determined there is defenitley a difference between the 2 but I am confused as to how important that difference is.

To make matters worse I ordered some Smart Chargers (1.8 A) for 38.4V (12 cells ) LiFeP04 Battery P/N CH-LA3618 from BatterySpace.com for $24.95. http://www.batteryspace.com/smartcharge ... dwide.aspx What I received, which looked identical to the picture was a Powerizer Power UNIT (For Pb-acid Battery) Model: 3px0.36V 1.8A Output: DC36V/1.8A.

Since I have several nearly identical SLA chargers already I compared the one from Battery Space with one of my other ones through a couple of charge cycles over the course of a week & could NOT measure any appreciable difference. They all seem to bring both SLA & LiFeP04 batteries up to 13.8 volts. I took pictures of the chargers label & emailed Battery Space explaining the mistake. After consulting with their "engineering department" (their words) they said that this in fact is the correct charger I should use it. Long Story short, I sent them back any way. *** I have also compared the optional 12 volt charger from Clean Republic with my fairly new high quality 12 volt automotive charger. The CR charger is labeled & puts out 14.8V at 5.0 amps. ( I only checked voltage, not amperage) My 12 volt auto charger puts out 10.8 volts on 2 amp float, 13 volts on 10 amp fast charge & 14.6 volts at 50 amp boost. So any other differences aside it does put out a higher voltage.

The battery packs I build are for the electric bike conversions I do on bikes that I purchase to sell to my LOCAL customers. I need to make sure that they are getting the best product that I can deliver.

Is there any appreciable difference between a comparable lead acid charger and its LiFeP04 counter part? If so will it effect performance & or shorten the life of a LiFeP04 battery? Can the way in wich you use a lead acid charger for a LiFeP04 battery be modified extend life/increase performance? i.e. unplug it as soon as the intial charge is done.
Lastly as I said in the beginning, these are 12 V 10amp LiFeP04 replacement batteries with NO BMS. I'll address the no BMS issues with some more questions in this forum at a later date.

Any & all thoughts are welcome.

Thanks
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Re: Using SLA chargers for LiFeP04 batteries

Postby dogman dan » Sun Jun 09, 2013 9:37 am

The chargers are nearly identical, but they have one main difference. The lifepo4 charger should shut off nearly completely when it gets the green light, while the lead charger will keep charging but at a very low amps.

In general, using the lead charger with a bms can be ok, since the bms will start discharging any overcharge. I charged a bms equipped lifepo4 with lead chargers for at least a year with no apparent harm. Also, your lifepo4 battery can tolerate a bit higher voltage than the lead might, so a lead charger will often tend to charge to a lower voltage, such as 56v for lead, while lifepo4 might be set to 58 or even 60v.

If your lead chargers are set to 56v and 42v, they won't be likely to overcharge them. But I wouldn't leave them plugged in for days or weeks on the charger, either kind, with out the bms. Overnight should be fine.
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Re: Using SLA chargers for LiFeP04 batteries

Postby EZgo » Fri Jun 14, 2013 2:02 pm

Thank you for the reply. I have spent a fair amount testing & researching & pretty much have discovered exactly what your telling me & It' s quite satisfying to have somebody with experience confirm it. I'm going to stick to my original plan of offering the lower cost SLA charger with the packs I'm building but have the more expensive lipo charge available for an additional charge. It would be great just to find a decent low cost lipo charger to use in the 1st place but I can't find anything under $40 something w/freight.

BMS has a 120W or 180W LiFePO4/Lithium Ion/Lead Acid 120W Battery Charger available for $16.90 or $25.00 respectively but I'm afraid I'd end up with the same thing I got from Battery Space. A lead acid charger that works for lipo batteries. Unlike Battery Space however BMS claims their cheap charger will adjust to the proper voltage based on what it's pluged into. B.S. just stated that their charger put out 42 volts. The most I ever recorded & the highest my LiFeP04 pack ever charged to was 39.1 volts.

At this point I need to find another affordable "LiFeP04 charger only" so I can measure the difference between the two. I'm positive that what ever that final voltage difference is, it will be able to be both felt & measured in performance & run-time. At least this is what I've been telling my customers.

As a final note I have some 12v LiFeP04 chargers that came with a few of the 12V batteries I bought. By charging 3 of these 12V batteries using the 12 Volt chargers (14.8V) that came with them I'm able to bring a 36 volt pack to 44.4 volts. Unfortunately after they are assembled & run down for an hour or so the highest voltage I ever get them back to using the 36V SLA charger is 39.9V.

I suppose if I never said anything my customers would never know. But I would & if I can't build it right then I won't sell it to someone else.
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Re: Using SLA chargers for LiFeP04 batteries

Postby dogman dan » Sat Jun 15, 2013 5:01 am

Hmm, substituting an sla charger for your own use is one thing, but selling it would be another. Customers might do things you wouldn't with it.

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Re: Using SLA chargers for LiFeP04 batteries

Postby dnmun » Sat Jun 15, 2013 10:58 am

can you post up a picture of the inside of the charger so we can tell you if it can be adjusted up in voltage to the correct voltage for the imitation batteries?

with no BMS to protect them these little batteries are gonna be dead pretty fast anyway. so we can see if the voltage can be adjust up on the charger.
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Re: Using SLA chargers for LiFeP04 batteries

Postby etriker » Sat Jun 15, 2013 12:00 pm

Why do you say they do not have a bms inside ?

These, right ?

http://www.electric-bike-kit.com/lithiu ... ement.aspx

Without a bms it needs balance wire leads so it can be balance charged now and then ?
Last edited by etriker on Sat Jun 15, 2013 12:15 pm, edited 1 time in total. View post history.
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Re: Using SLA chargers for LiFeP04 batteries

Postby The fingers » Sat Jun 15, 2013 3:54 pm

They would look nice on an e-bike with a bamboo frame. 8)
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Re: Using SLA chargers for LiFeP04 batteries

Postby dogman dan » Sun Jun 16, 2013 6:02 am

Could he modify the sla chargers to be lifepo4 chargers fairly easily? Obviously I'm clueless how to do it.

Does a typical bms actually shut off current to cells? I thought they (bms) just started draining high cells, and when enough cells got high, the charger itself shut off current when the green light goes on.
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Re: Using SLA chargers for LiFeP04 batteries

Postby 7tronics » Mon Jul 15, 2013 12:52 pm

I ordered two of the Bamboo replacements from Clean Republic as well. I am using a Currie 24v "Lithium" charger which came with a Currie Via Rapido and 24v LiFePO "RTMB" rack mount pack. I am replacing the 24v AGM/gel cells on the two Trailz ebikes with two Clean Republic LiFePO batteries. The same charger connector is used on both, but the Lithium charger does bring the 24v pack up to higher voltage and I don't see the "float" mode kick in as on the AGM/gel cell batteries.

Can anyone else verify that the Currie charger for RTMB Lithium batteries is indeed setup for Lithium battery chemistry?
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Re: Using SLA chargers for LiFeP04 batteries

Postby Nineballboy » Fri Jul 19, 2013 12:43 pm

The RTMB battery pack is not LiFePo4! You may not want to use that charger! :shock:
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Re: Using SLA chargers for LiFeP04 batteries

Postby dumbass » Fri Jul 19, 2013 6:58 pm

There are a few companies that sell similar 12v lifepo4 packs that also do not have a BMS. I have several of the old Thunder Sky and others. From my experience if you charge these packs without a method to balance the individual cells it will come out of balance very quickly. And without a low cell cutoff you will kill the pack. To me this is a bigger issue then the type of charger that is used.

I would love to know the dementions of the cells without the bambo box around it. And what type of cells are actually in the box. Maybe without the bambo boxes there might be room in the stock Currie battery box to also fit a small BMS.

Bob
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Re: Using SLA chargers for LiFeP04 batteries

Postby 7tronics » Fri Jul 19, 2013 10:14 pm

Oh, so this the "24v 2a" Li-Ion charger:
https://www.curriestore.com/bikes-scoot ... 201119396/

And I see it and the RTMB battery pack lists "Li-Ion" not LiFePO4 chemistry.

I'll check the terminal voltage, so I see now that Li-Ion tends to have higher voltage limit per cell for charging (3.7v/cell while charging) than LiFePO4 (3.2v per cell while charging).

Thank you for noting this! For now it appears a non-desulphating lead acid charger will work until I receive a charger with the correct voltage profile during charging.

BTW - the Bamboo CR1210 is nearly identical in size to a 12v 7ah gel cell: 151x65x95mm

Some alternative "12v SLA replacements" are listed in this thread: Homemade Battery Packs

There are a number of BMS boards available from the batteryspace.com site.
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Re: Using SLA chargers for LiFeP04 batteries

Postby veloman » Wed Jul 24, 2013 9:56 pm

I've been using a yescomusa 48v sla charger for my 16s a123 pack for a while. Sometimes it does charge it up near 60v or so. But usually stops at 57.6v. I never leave chargers plugged in when done.
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Re: Using SLA chargers for LiFeP04 batteries

Postby DAND214 » Wed Jul 24, 2013 11:05 pm

veloman wrote:I've been using a yescomusa 48v sla charger for my 16s a123 pack for a while. Sometimes it does charge it up near 60v or so. But usually stops at 57.6v. I never leave chargers plugged in when done.

Dose it have a BMS? Or do you single cell balance it?

Dan
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Re: Using SLA chargers for LiFeP04 batteries

Postby 999zip999 » Wed Jul 24, 2013 11:40 pm

Selling ? You have to know whats inside. This is E.S. you got to cut one open. Yes the one you will use on your bike. Take pic's.
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Re: Using SLA chargers for LiFeP04 batteries

Postby 999zip999 » Wed Jul 24, 2013 11:52 pm

A lifepo4 being charge with a sla charger will find a weak cell and unbalance the battery over time. You need a bms or sesnse wires to check. Will work for a while but how long ? No bms ?
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Re: Using SLA chargers for LiFeP04 batteries

Postby veloman » Fri Jul 26, 2013 9:11 am

DAND214 wrote:
veloman wrote:I've been using a yescomusa 48v sla charger for my 16s a123 pack for a while. Sometimes it does charge it up near 60v or so. But usually stops at 57.6v. I never leave chargers plugged in when done.

Dose it have a BMS? Or do you single cell balance it?

Dan



It has a BMS. Occasionally I may use a proper 58.4v charger (6amps) to top it off and let it sit to make sure it has time to balance.
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Re: Using SLA chargers for LiFeP04 batteries

Postby gogo » Fri Jul 26, 2013 10:11 am

7tronics wrote: For now it appears a non-desulphating lead acid charger will work until I receive a charger with the correct voltage profile during charging.

It seems B&D smart chargers have a selectable 'reconditioning' mode that sends some sort of high frequency through the battery for 24 hrs., but no charging current. I'm not sure what effect that would have on lithium batteries, but its probably worth avoiding. Its difficult to wade through the marketing speak, but the charger may be using that high frequency during the regular charging mode as well.

Some of the more feature rich models have an 'equalization' mode that requires the removal of the vent caps so that when it overcharges at a higher than normal voltage, the liberated gasses can escape. Would this be considered a top-charge balance of the cells?

You'd definitely not want to use that 'equalization' mode on anything but flooded lead acid. It takes a pointy object such as a ball point pen to actuate that mode.
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Re: Using SLA chargers for LiFeP04 batteries

Postby 999zip999 » Fri Jul 26, 2013 1:50 pm

The sla charger does not charge at a high enough voltage for the bms to bleed off the high cells and balance by bring up the low cells. charging to 54.8v is not high enough for the lifepo4 bms to balance the cells. The cells will drift apart over time. Unless you have 16 prefect cells all the same and all the same over time.
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Re: Using SLA chargers for LiFeP04 batteries

Postby EZgo » Thu Aug 22, 2013 6:57 pm

The last I looked at this post was towards the end of June when it had 3 or 4 replies. Today I was looking for something & it came up in a Google search with about 10 more replies so I decided I should provide more information. If anybody thinks I should start a new thread let me know. For now this what I know.

Months ago when I bought my 1st bamboo battery it was to test it & then take it apart. Long story short over a 2 month period I bought about 18 more of them. I did a lot of testing & built 3 36 volt bikes & 2 48 volt bikes. 1 48 volt is sold with a 48 volt sla charger. Another 48 volt is in my shop along with 2 36 volt bikes. I'm currently testing the 48 volt bike & charging it with a 58.4 volt LiFeP04 smart charger from battery space.

I will also start charging it with a 48 volt SLA charger from E-BikeKit in another week or so to see how they compare performance wise. I'm using a Watts-Up meter & a Bell Dashboard 100 cyclometer for gathering data. I have not made any provisions for testing individual cells & that is my single biggest concern with these 12 volt Bamboo Batteries. Will these be any good in the long run? Can they be made to last just by monitoring the whole pack? In the short term they seem to be great.

dumbass wrote:There are a few companies that sell similar 12v lifepo4 packs that also do not have a BMS. I have several of the old Thunder Sky and others. From my experience if you charge these packs without a method to balance the individual cells it will come out of balance very quickly. And without a low cell cutoff you will kill the pack. To me this is a bigger issue then the type of charger that is used.

I would love to know the dementions of the cells without the bambo box around it. And what type of cells are actually in the box. Maybe without the bambo boxes there might be room in the stock Currie battery box to also fit a small BMS.

Bob


OK then,... this is what a 12 volt 10 amp LiFeP04 SLA replacement battery by Clean Republic looks like on the inside. I was hoping someone else would have done this by now. For now it is neatly cut open & I can put it back together & continue using it. I'm sure someone out there can identify these cellls with out me tearing the whole thing apart. Here is the nitty gritty.

Inside dimension of the box is 2 5/16" W x 5 1/2" L x 3 7/8" H. There is a 1/4" space between the end of the battery & the case at 1 end.

Each cell measures 1 1/8" x 2 1/2" L. . Unless there is an empty spot inside, there is room for exactly 12 of these cells. The voltage is 14.27 & the total weight of the battery is 2lb 9 oz.

My 48 volt bike at the moment is running 5 of these. Hot of the charger the Watts up meter reads 68.88 volts. 30 minuets of normal running brings them down to 64.35 volts. In that condition if I open it up from a standstill on an uphill grade (no pedaling) it will just hit 22 amps & dip to 58.82 volts by the time it hits 22 mph uphill it goes to 20 amps & 61.44 volts. When I hit the leval I'm doing 25 at 7 amps & back to 64. volts. To charge my 5 battery bike I use the 58.4 volt LiFeP04 smart charger from battery space & a 14.8 volt LiFeP04 charge from C.R. (the one that comes with the battery)

Keep in mind that C.R. is selling these as a SLA replacement battery so it's quite possible they may last a very long time in that type of application.

The only comparison testing I've done has been a seat-of-the-pants test using the above bike with one battery removed & an identical 48 v E-BikeKit using a 48 v 9 amp SLA battery pack.

The results?.... Their is HUGE difference in the first 60 seconds & it gets progressively worse pretty quick.

I have pictures of the bike on my blog at:http://ezgo-now.com/local-sales/night-rider-the-ultimate-e-bike-for-work-or-play. I'll try to update this or start a new thread as I learn more about these batteries. For now about the only advice I can give on the charges is if you use an SLA charger of any type unplug it as soon as you think the battery is charged. I use a $10 110 volt timer & set it for how long it needs to be on. You won't know that until you charge it a few times. My 48 volt 10 amp LiFeP04 will take about 2 hrs to charge after I have put about 2 hrs on the clock with the SLA charger. The LiFeP04 charger is faster.

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2 lb 9 oz.
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C.R. LiFeP04 Bamboo charger
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14.28 volts
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Room for 12
IMG_0007.JPG (22.56 KiB) Viewed 4259 times
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inside from the botoom
IMG_0005.JPG (32.78 KiB) Viewed 4259 times
Attachments
IMG_0004.JPG
close up of cell
IMG_0004.JPG (29.3 KiB) Viewed 4259 times
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Re: Using SLA chargers for LiFeP04 batteries

Postby Gab » Fri Aug 23, 2013 5:05 am

One other thing u can do if you are worried about leaving the battery on the charger and it won't cut off, is to measure how long it takes to charger a fully flat battery. And then get a simple wall plug timer, and put the timer on the charger a short time after the pack is charged to cut power to the power supply.

As long as u have a good quality timer that's keeps working ! u shouldn't have any problems if u tune the time correctly.
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Re: Using SLA chargers for LiFeP04 batteries

Postby hulagun » Mon Jan 20, 2014 2:48 pm

I would like to revive this thread.

EZGo, if you read this, I would love to find out how things have worked out for you with the Clean Republic batteries. I have a couple of their Bamboo LifePo4 batteries on the way that I plan to run in series in a 24v Razor 300 scooter.

They claim the simplest way to recharge is to use the 24v SLA charger that comes with the scooter. I didnt get a charger with the scooter, so am wondering if I should buy a nicer charger instead. I have several SLA chargers already, but am pretty sure they all have a float mode which I understand is not the best way to go.

Any advice you have would be welcomed.

One possibility is to buy 2 of the $20 Clean Republic 12v chargers (which they recommend as designed for LiPo use) and charge the batteries separately and simultaneously at 12v.

This idea isn't unappealing but carrying two chargers is a minor hassle. (Could mount them both in a box, rewired to a single 110v inlet plug, I guess). I'd also have to figure out a modified dual input plug setup to attach the two 12v charge inputs, which I assume is possible.

No matter what charger I end up using, I do still plan to measure charge times and then use a timer to cut power to the charger at a preset interval.

Thanks for any advice.
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Re: Using SLA chargers for LiFeP04 batteries

Postby Hillhater » Tue Jan 21, 2014 1:34 am

Has anybody asked CR if these 12v batteries actually has a BMS inside ?
Essential to know i would think..especially if you are on-selling to paying customers. :roll:
If it were me, i would tear one down to be sure.
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Re: Using SLA chargers for LiFeP04 batteries

Postby hulagun » Tue Jan 21, 2014 2:27 am

Hillhater wrote:Has anybody asked CR if these 12v batteries actually has a BMS inside ?
Essential to know i would think..especially if you are on-selling to paying customers. :roll:
If it were me, i would tear one down to be sure.


Thanks HH. Assume no BMS. CR has been asked that question. See previous posts (also see photos in previous posts). It's still unclear if there is a BMS in there, but CR doesn't claim there is. At the price point I paid (USD $80 each) I just assume there is no BMS.

FWIW I've read that a BMS is not mandatory IF LifePo4 cells are carefully matched at assembly. I'm no expert, but if this is true, then these batteries should do exactly what I want, which is directly replace SLAs.

Admittedly, I'm gambling an extra $130 or so over just buying SLA's. But the CR batteries are designed to directly replace SLAs. If they deliver what I hope: a significantly longer useful life, slightly longer run time, noticeably lighter weight (already a given), and quicker recharge time, they'll be worth it. And hopefully keep 4 or 5 pairs of SLA's out of the recycle bin.

Unfortunately I haven't found much definitive info on what charger to buy, which is what I was asking...
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Re: Using SLA chargers for LiFeP04 batteries

Postby dogman dan » Tue Jan 21, 2014 6:54 am

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.
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