SLA charger for LiFePO4?

Batteries, Chargers, and Battery Management Systems.

SLA charger for LiFePO4?

Postby Patriot » Fri Oct 10, 2008 8:12 pm

SLA charger for LiFePO4?

I ask, because these chargers are regularly found on Ebay for only about $20. E-crazyman has them for very good prices.

If you have a BMS circuit installed to your battery, can't you then use a regular charger that would normally be used for just SLA batteries?

It seems logical since your BMS is now doing all the cell balancing and overcharge protection.

Am I wrong here?
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Re: SLA charger for LiFePO4?

Postby Kurt » Fri Oct 10, 2008 8:49 pm

Doesn't life need a little more voltage to fully charge ?

I think my own ecrazyman 48v sla charger only charges to about 53 or maybe 54v tops.

I was under the impression that pings 48v chargers topped up to 60v?
perhaps they could be modified to give out more voltage ?

I would like to know also.
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Re: SLA charger for LiFePO4?

Postby Rassy » Fri Oct 10, 2008 8:57 pm

Kurt wrote:
I was under the impression that pings 48v chargers topped up to 60v?

You are correct. I have a 48V charger from anna that tops out at about 61V to allow balancing to take place. The battery comes hot off the charger at about 59V, but settles down to about 55V before use, and goes down to 53+V as soon as use starts.
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Re: SLA charger for LiFePO4?

Postby dogman » Sun Oct 12, 2008 8:12 am

My Ping 36 v has been charging for about 80 cycles or more on sla chargers. It's still balanced since it has not needed balancing. I discharge at a lower rate, under 1.5 c so my pack stays balanced. I recently tweaked one of my soneil chargers to a higher voltage, and I can't tell if it balances, since it would only do it if the pack needed it. When the pack was new, It would do the balancing cycle for awhile every charge, but after a week or so , it stopped doing that, and even when I still had the Ping charger, it never did any balancing after that. One of my chargers, a cheapie, does not have the adjustable voltage, but most of the soneils seem to.

In summary, if you treat the battery pack right, you may need balancing a lot less than others with high discharge rates.
THE LIPO RULES. NEVER ABOVE 4.3V NEVER BELOW 2.7V DON'T PUNCTURE

Ideal charging /discharging range for Lipo, 3.65v minimum 4.1v maximum

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Re: SLA charger for LiFePO4?

Postby snowranger » Thu Nov 13, 2008 1:47 am

This charger supposedly outputs at 60 volts. Any idea if this is compatible with a Ping 48 volt?

http://tncscooters.com/product.php?sku=101155
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Re: SLA charger for LiFePO4?

Postby vanilla ice » Thu Nov 13, 2008 1:55 am

That puts out more than 60v. More like 67 or 68.
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Re: SLA charger for LiFePO4?

Postby snowranger » Thu Nov 13, 2008 1:58 am

First hand experience with that one?
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Re: SLA charger for LiFePO4?

Postby vanilla ice » Thu Nov 13, 2008 2:04 am

Nope. Thats just how SLA chargers are. Divide by 12 then multiply by like 13.4 to get the output voltage.
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Re: SLA charger for LiFePO4?

Postby snowranger » Thu Nov 13, 2008 2:14 am

Understood. If an SLA charger could be modified to 60 volts then there would be no difference from the LifePO4 charger, yes?
Electric: 400 watt BMC Hub Motor w/disc brake/Infineon 48V 30A controller/Dead 48V 20Ah Ping replaced with Headway 48V20ah
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Re: SLA charger for LiFePO4?

Postby dogman » Thu Nov 13, 2008 7:26 am

Pretty much, or at least the same as the ones that you get with a duct tape pack. Many of the soneil chargers have an adjustable pot inside to tweak up the voltage. Many of the extra cheap ones don't have the adjustable pot. Unless you allready have one with adjustment, it might be easiest to just get one from ping. No problem to use a stock sla charger for a while though.
THE LIPO RULES. NEVER ABOVE 4.3V NEVER BELOW 2.7V DON'T PUNCTURE

Ideal charging /discharging range for Lipo, 3.65v minimum 4.1v maximum

See battery technology section, FAQ thread at the top of the page for lipo noob info.

See the frankenbike longtail at the thread below.
viewtopic.php?f=6&t=28389&hilit=bouncing+betty
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Re: SLA charger for LiFePO4?

Postby snowranger » Thu Nov 13, 2008 4:06 pm

I am suspecting that the charger fan may blow at some point. Ping says that my 5 amp charger will work without the fan, so I guess everything is okay.
Electric: 400 watt BMC Hub Motor w/disc brake/Infineon 48V 30A controller/Dead 48V 20Ah Ping replaced with Headway 48V20ah
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Re: SLA charger for LiFePO4?

Postby Don Harmon » Thu Nov 13, 2008 5:43 pm

Charging LiFePO4 requires a slightly different algorithym than SLA. It is true you can use an SLA charger to do LiFePO4, but you won't get a complete and balanced charge doing it. The Soneil's can be purchased "already tuned or tweaked" for LiFeBATT (LiFePO4) and you can order them from some Soneil distributors. OR, you can also contact Soneiel before you try to tweak one of their chargers and they will give you instructions so that you do not lose your warranty doing it on your own. Of course that will depend on what model of Soneil charger you have.

Zivan also offers a LiFePO4 algorithym programmed into their charger - but you have to specify one that has a LiFeBATT approved label on it. Right now I know they are available in Europe, but not sure the U.S. distributor has them in stock ?

Hope this helps /

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Re: SLA charger for LiFePO4?

Postby rkosiorek » Thu Nov 13, 2008 7:04 pm

many cheap chargers for SLA are constant voltage chargers. they put out a constant voltage as the SLA battery charges up the current tapers off. at full charge the current will be almost zero.

this can be bad for the battery as there will always be some current trickling into the battery as lng as it is connected. this can eventually cook the battery.

more sophisticated chargers start with a Constant Voltage and continue charging until the current drops to a certain level. then the charger switches to a Constant current mode. in constant current mode the current is much set to a fixed value and allows the battery to top up. the CC mode will normally terminate after a fixed period of time.

these fancier dual mode chargers are called CV/CC chargers. the charge output for these more closely matches the charge profile for LiFePO4 cells. Soneil chargers have pots for setting both the CV voltage and the current level were it switches to CC mode.

for a 36V CV SLA charger the voltage is set for something between 40.2 and 41.4V. a 36V LiFePO4 CV would be between 43.8 and 44.4V. that is just a bit higher than SLA. the other difference is the charge current. this depends on the cell manufacturer. there is a larger variation in this spec with LiFePO4 than with SLA as the specific Chemistry varies much more with LiFePO4 between manuaftures. a conservative profile would be to charge the cells starting at a 1C rate using CV. once the current drops dpwn to 1/10th C switch to CC mode to finish the charge.

the Soneil and other CV/CC chargers can be tweaked to deliver the higher voltage needed for the CV mode as well as the current trip to set the CC mode. but this does not mean that all SLA chargers will work as well or the charge the battery completely without the CC phase of the charge. also it is much easier to cook the batteries without the CC mode. realy easy if the pack doesn't have a BMS to blunt the impact of not having the CC stage.

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Re: SLA charger for LiFePO4?

Postby Ypedal » Thu Nov 13, 2008 7:14 pm

Is it not the other way around ?.. cc then cv ?
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Re: SLA charger for LiFePO4?

Postby Don Harmon » Thu Nov 13, 2008 7:22 pm

YES, It is CC/CV.

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Re: SLA charger for LiFePO4?

Postby rkosiorek » Thu Nov 13, 2008 9:37 pm

you are right. CC until target voltage than CV to float.

i should not write technical stuff immediatetly after taking a big hit of demerol. just had some dntal surgery. amazed i even spelled CV and or CC right.

i will now slink away in shame until the drugs wear off.

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Re: SLA charger for LiFePO4?

Postby dogman » Fri Nov 14, 2008 7:29 am

I love the forum, they just nail me when I am dead wrong! :lol: :lol: Seriously though, isn't lifepo4 sorta tolerant to overcharging, compared to sla, so why would a charger sla can tolerate cook a lifepo4? I agree with Don, that a $10,000-$30,000 investment in a large vehicle pack requires a coresponding investment in the best possible charger, but for a cheap duct tape pack, I believe a sla charger with the right voltage is fine.
THE LIPO RULES. NEVER ABOVE 4.3V NEVER BELOW 2.7V DON'T PUNCTURE

Ideal charging /discharging range for Lipo, 3.65v minimum 4.1v maximum

See battery technology section, FAQ thread at the top of the page for lipo noob info.

See the frankenbike longtail at the thread below.
viewtopic.php?f=6&t=28389&hilit=bouncing+betty
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Re: SLA charger for LiFePO4?

Postby Don Harmon » Fri Nov 14, 2008 10:40 am

It wasn't me who made the "cooking" statement. LiFePO4 is tolerant of an overcharge - not very tolerant of an over discharge. My point, and you are correct that the regular SLA chargers are not set at a high enough voltage to match LiFePO4, is that even the e-bike packs can take advantage of proper charging simply by making a few adjustments to a standard SLA Charger IF you know how and do it properly. So, why not since the cost is not prohibitive to do this.

Best,

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Re: SLA charger for LiFePO4?

Postby dogman » Fri Nov 14, 2008 5:27 pm

Sorry if I misquoted you, Don. Sometimes when you start reading too many comments, you get confused who said what. I would really want to be carefull what charger I used with a pack worth 5 thou, but on my ping pack worth under $500 I'll risk an experiment.
THE LIPO RULES. NEVER ABOVE 4.3V NEVER BELOW 2.7V DON'T PUNCTURE

Ideal charging /discharging range for Lipo, 3.65v minimum 4.1v maximum

See battery technology section, FAQ thread at the top of the page for lipo noob info.

See the frankenbike longtail at the thread below.
viewtopic.php?f=6&t=28389&hilit=bouncing+betty
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