Oxygen Lepton LiFePO4 conversion help

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queensland
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Oxygen Lepton LiFePO4 conversion help

Hi all,

I know this topic has come up in the past but I'm not sure I understand the work arounds for a problem. Sorry I'm not an electronics expert either. This spring I switched from SLA batteries to a new LiFePO4 pack and an external Lion smart charger. The bike had an SLA charger onboard but the LiFePO4 batteries are not connected to it now. Haven't had power or performance problems and the charger is working, so I think the batteries themselves are OK, but I suspect (based on some forum posts in the past) the Lepton's electronics can't read the battery status. The displayed available range has dropped despite a charge after each trip and now the low battery warning light is on. According to the owner's manual the scooter will shut down to protect the battery if the charge gets too low. Of course I'll check the battery charge itself, but wondered if anyone else has a good solution for this one? It would be great to retain the Lepton's battery status/range display but I can easily use the odometer mode instead. I just don't want to be staring at that flashing battery warning light forever or have the scooter try to shut itself off. Thanks!

dogman
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Re: Oxygen Lepton LiFePO4 conversion help

Get a voltmeter and check the battery itself. If total voltage after a full charge is low you know you have a battery problem. If so, then you can use the leads to the bms to check the voltage of each cell. The first should be 3.5 or so, the second 7, meaning the second one is also 3.5 and so on. Some of the less expensive packs with lots of round cells have had cells fail one by one, till the total battery voltage drops. You might be able to ride a while, but the pack would start out lower than usual, and the bms shut it down earlier too.

Nice as lifepo4 is, the usual method of constructing a pack requires all of it to work, so if the pack has 144 cells, you have 144 opportunities for it to fail. With a sla 36v pack, you have 18 cells, so less chances to fail.

Be the pack leader.
36 volt sla schwinn beach cruiser
36 volt lifepo4 mongoose mtb
24 volt sla + nicad EV Global

dogman
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Last seen: 14 years 4 months ago
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Re: Oxygen Lepton LiFePO4 conversion help

Get a voltmeter and check the battery itself. If total voltage after a full charge is low you know you have a battery problem. If so, then you can use the leads to the bms to check the voltage of each cell. The first should be 3.5 or so, the second 7, meaning the second one is also 3.5 and so on. Some of the less expensive packs with lots of round cells have had cells fail one by one, till the total battery voltage drops. You might be able to ride a while, but the pack would start out lower than usual, and the bms shut it down earlier too.

Nice as lifepo4 is, the usual method of constructing a pack requires all of it to work, so if the pack has 144 cells, you have 144 opportunities for it to fail. With a sla 36v pack, you have 18 cells, so less chances to fail.

Be the pack leader.
36 volt sla schwinn beach cruiser
36 volt lifepo4 mongoose mtb
24 volt sla + nicad EV Global

queensland
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Re: Oxygen Lepton LiFePO4 conversion help

I checked the 2 batteries. Each shows 24-25v (the total pack reads about 49v) after a charge. This still leads me to think the scooter just can't read the battery state correctly.

"Tis better to remain silent and be thought a fool than to speak and remove all doubt." Abraham Lincoln

antiscab
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Re: Oxygen Lepton LiFePO4 conversion help

that doesnt sound right.

each "24v" battery should have 8 cells.
25v is 3.125v, which at no load is just about dead for a LiFePO4 battery.

I cant comment on how the original indicator determines remaining capacity (pack voltage? pack sag? Ah count?)
perhaps someone else can fill us in on this

Matt

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km

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