Taking the LiFePO4 plunge

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ChrisB
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Taking the LiFePO4 plunge

Postby ChrisB » Fri Aug 07, 2009 10:30 pm

Well after much thought and investigation I'm going to go modern :shock:

Yep I'm pushing the boat out and buying a set of LiFePO4's :shock:

OK so its only a little baby 24v 15Ah pack :oops: but its a start, you've got to start somewhere :lol:

Went for a pack from Ping Batteries in the end (available on e-bay) other LiFePO4 battery suppliers are available :wink:
This is a fish out of water moment for me, I've never had to worry about BMS or overcharging or over discharging etc although it doesnt do any battery much good it does seem to kill Li's pretty quickly and permanently :shock: so as Pings cells come with a BMS it appears they are pretty bomb proof ............ we shall see, any hints or tips on these alien batterys (well alien to me) would be grateful.

So just sit back and see what arrives all the way from the far east, never imported anything from China before so not quite sure how it all works ?

ChrisB
I reject reality and substitute my own !!!!!!

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retepsnikrep
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Postby retepsnikrep » Sat Aug 08, 2009 4:57 am

What are you going to use them in?

The real thing Li hate is over discharge, I don't mean being pulled low with a high load when in a decent soc, I mean being allowed to discharge completely under a light load and then going below minimum safe voltage.

That will kill them fairly quickly, trust me I know :shock:
Regards Peter

Two MK1 Honda Insight's. One running 20ah A123 Lithium pack. One 8ah BetterBattery Nimh pack.
One HCH1 Civic Hybrid running 60ah A123 Lithium pack.

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Jeremy
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Postby Jeremy » Sat Aug 08, 2009 5:33 pm

My experience with a Ping LiFePO4 pack has been very good. You don't need to worry about cell over-charge or over-discharge, as the SignalLab BMS fitted to the pack provides near-perfect protection.

It protects from over-charge and over-discharge at the cell level, plus has over-current protection that, like the cell under-voltage detection, turns the output off if you try and exceed the set limits.

The only downside is the long time that the first charge takes, the pack can take several hours to balance initially, or if recharged after a long period of disuse.

Jeremy

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ChrisB
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Postby ChrisB » Sun Aug 09, 2009 10:53 am

Cheers guys

Yes having read and spoken to so many folks who have lost sets of Li due to prolonged slow discharge its really put me off them, as my electronic skills arent up to building my own BMS I thought I'd start with something pre-built.

Currently my Ping experience is excellent, great comms, answered my questions and according to my tracking number my 15ah 24v pack is on its way

The pack is going into an electric bike with a 200w motor, currently has 24v 12ah SLA's in it as in 2x12v

ChrisB
I reject reality and substitute my own !!!!!!

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Jeremy
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Postby Jeremy » Sun Aug 09, 2009 7:33 pm

I wouldn't be too surprised to find that you may end up with a 50% range improvement with the Ping pack. Although it's only 20% greater in capacity, LiFePO4 has a near-unity Peukert factor, which will add at least another 20 to 30%.

Jeremy

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Night Train
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Postby Night Train » Mon Aug 10, 2009 3:21 pm

It will be interesting to see how these work out for you.

I am working on the basis that I will have to use LiFePo batteries as the only way to achieve usable range and reasonable weight.

I haven't imported anything over from China either (except for the occasional relative but I was able to send them back! :wink: ) so I am interested in how that process works too.

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ChrisB
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Postby ChrisB » Tue Aug 11, 2009 7:21 am

Wow Jeremy, 50% improvement :shock: thats going to be really great.

These LiFePO things are totally new to me and it was funny as I only got the bug after my mum forgot her phone charger and thus couldnt recharge her phone, so me being me thought in for a penny in for a pound and set up a bench power supply, did a quick bit of research on the voltages and currents and gave the battery a quick bench charge, was quite surprised at how easily it went and nothing went bang or failed and thus I thought "well there not that bad, they seem to react similar to other batteries to a degree so lets give it a go"
Yeah I know its an odd way of looking at things but you have to start somewhere :lol:

Night Train : Yep this is a first for me on the import side of things and to date the whole tracking thing has worked really well, saw it leave the sorting office and go to another distribution center and its even now appeared on the Parcel Force website 8) although it does appear that since leaving SHANGHAI sorting office its dissappeared for the past few days :? then again if Parcel Farce have anything to do with it theres a chance it wont ever make it past them :lol: :?

Heres hoping for some more tracking info today ?

ChrisB
I reject reality and substitute my own !!!!!!

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ChrisB
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Postby ChrisB » Thu Aug 13, 2009 7:26 am

Well its in the UK and very local to me according to the tracker 8)

Recon it could get delivered either today or tomorrow 8)

ChrisB
I reject reality and substitute my own !!!!!!

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ChrisB
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Postby ChrisB » Thu Aug 13, 2009 5:29 pm

Its arrived 8)

OMG how excited am I :lol: my first venture in to LiFePO4 stuff.

Got to say I am extremly impressed with Pings packaging, its very good, considering its been halfway round the world theres hardly a dent in the package.

Have to say its slightly heavier than I thought but then its no where near as heavy as the SLA's and is much bigger capacity.

I think the only comment so far is there was no instructions with it, nothing, just the address details on the front of the package.

I've e-mailed Ping to see if this was an over sight ??

I'll put some pics up later of what ya get and how it arrives

ChrisB

PS didnt get charged any extra either 8)
I reject reality and substitute my own !!!!!!

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Jeremy
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Postby Jeremy » Thu Aug 13, 2009 9:36 pm

This is the text of the instructions for the 24V, 10Ah pack from Ping, might be some help:

User Guide - 24V10Ah

Specification of Battery Pack and BMS
1 Rated Voltage: 24 Volts
2 Capacity: 10 Amp Hours
3 Weight: 2.3 kg
4 Dimension: 150x110x95 mm
5 Suggested Load: 250 Watt
6 Max Load: 350 Watt

Specification of BMS (Battery Management System)
1 Charging Voltage: 31 Volts (Max)
2 Charging Current: 5 Amps (Max)
3 Rated Discharging Current: 10 Amps
4 Max Continuous Discharging Current: 20 Amps
5 Cut-off Current (Max Current): 25 Amps

Specification of Charger
1 Input Voltage: AC100Volts-220Volts
2 Output Voltage: DC31Volts (±2%)
3 Output Current: 2Amps (±3%)
4 Polarity of the Connector (face to the connector):

1. Positive
2. Null
3. Negative
Caution: Please make sure the polarity of the charger connector is corresponding to your battery box or battery pack, positive to charging positive, negative to charging negative. Any mistakes might destroy the battery pack.

Wiring of Battery Output
1 RED Wire (Marked): Positive (Charging/Discharging)
2 GREEN Wire (Marked, thinner than the other two): Negative (Charging)
3 BLACK Wire (Marked): Negative (Discharging)
4 RED + thin GREEN: Charging
5 RED + BLACK: Discharging (Power Output)
Caution: Please be very careful when connecting these wires to your battery box or electric vehicle. If you don’t understand how to connect, please send mail to pingping227@hotmail.com. Any mistakes in this progress might destroy the battery pack.

Tips
1 First charging costs more than 10 hours. Red light turns to green, then turns to red again after a while, again and again. It’s normal. The charger is balancing the capacity of battery cells.
2 The battery pack’s capacity will be activated to its real capacity (10 Amp Hours) after 3 to 5 times cycle. Before being activated, it seems to have 8 to 9 Amp Hours capacity.

Thanks for using our batteries.


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