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Discussion Starter #1 (Edited)
TLDR: Toolong didnt read: need help. 120v LiFePO4 pack (36 x 3.2v 260ah winston cells) sat for long time and discharged, BMS wont turn on till pack at 80v, whats the best way to go about charging pack? Can I keep cells in the car and bypass bms and put 120v into it directly?

I have a few questions about my wheego life.

Only ~200 were made in georgia - was actually the 3rd electric vehicle approved in the us behind Tesla Roadster and Nissan Leaf - practically making it a collectors car. However its an imported body shell from china, cracking plastic everywhere and rust and paint job are garbage.

Whats great about this car however is the relatively low voltage (120v) LiFePO4 battery pack (36 3.2v 260AH winston cells wired in series) consistently giving it 80+ miles of range, near 100 if more city driving without ac.

These battery's go 6000+ cycles, perhaps more! Should be in all ev's over the throw away lithium ion crap.

But the EV sat for years and didn't charge. Guy tried to plug it into standard 120v outlet with lvl 1 charger after it sat for that long, and it wouldn't charge ( I think he fried the pack?)
How should I charge this pack, I dont want to take out the cells 1 by 1.
 

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My questions are, the pack was attempted to be charged from completely dead; Would it have damaged all the battery cells or just the first few cells in the series circuit?
Charging a dead pack isn't going to be what killed it. Draining it empty is probably what killed it. If it is.

Also how would I go about restoring this pack/the cells?
How do you go about restoring ashes back into a tree?

If it's dead it's dead.

I thought id just take them out one by one, and over the course of weeks charge them individually with 3 volt phone chargers - bad idea? ( i know about fire risk, overcharging etc)
Where are you getting 3 volt phone chargers?

Regardless, the, what, 5w max you'd be pumping into a 260ah battery is then an 11 day charge per cell? 0.004 C charge rate?

Even if there was a short, I can't imagine that 5 watts on a battery that size would cause enough heat to overheat it. There's enough thermal mass it would dissipate that to its surroundings.

I'd try to charge them manually, supervised, with a car battery charger. It'll get bogged down to nearly zero volts as it's charging up, 2, 5, 10amps or whatever. Even that is only 0.04C, a 26 hour charge. Just make sure you disconnect it before the voltage of the cell rises above 3.3v.

Or, maybe an old PC power supply's 3.3v rail can usually pull like, 20 amps. You'll have to short a pin to make it start up (just google computer PSU bench supply), but that might be your fastest method. Only 13 hours per cell that way. Hopefully it's designed to overcurrent gracefully and not incitefully.

I'd see no harm in trying to charge them in series, they'll either work or they won't. It's just a matter of which ones are dead.

I suspect all are dead. But, find out.
 

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Discussion Starter #3
Charging a dead pack isn't going to be what killed it. Draining it empty is probably what killed it. If it is.



How do you go about restoring ashes back into a tree?

If it's dead it's dead.



Where are you getting 3 volt phone chargers?

Regardless, the, what, 5w max you'd be pumping into a 260ah battery is then an 11 day charge per cell? 0.004 C charge rate?

Even if there was a short, I can't imagine that 5 watts on a battery that size would cause enough heat to overheat it. There's enough thermal mass it would dissipate that to its surroundings.

I'd try to charge them manually, supervised, with a car battery charger. It'll get bogged down to nearly zero volts as it's charging up, 2, 5, 10amps or whatever. Even that is only 0.04C, a 26 hour charge. Just make sure you disconnect it before the voltage of the cell rises above 3.3v.

Or, maybe an old PC power supply's 3.3v rail can usually pull like, 20 amps. You'll have to short a pin to make it start up (just google computer PSU bench supply), but that might be your fastest method. Only 13 hours per cell that way. Hopefully it's designed to overcurrent gracefully and not incitefully.

I'd see no harm in trying to charge them in series, they'll either work or they won't. It's just a matter of which ones are dead.

I suspect all are dead. But, find out.
thanks for the reply. By plugging it into the charger, I believe the BMS didn't even allow a charge to enter the battery cells so I am ok, they just slowly discharged to 0 or near it after 3 years or so.

I am going to very very slowly trickle some current back into the cells at first to wake them up without damage, i dunno if this works/is worth the time but it seems it would in theory.

wish I had a service manual for this car but it doesn't exist.

I assume the wiring isn't any more complicated than most EV's
 

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Whats great about this car however is the relatively low voltage (120v) LiFePO4 battery pack (36 3.2v 260AH winston cells wired in series) consistently giving it 80+ miles of range, near 100 if more city driving without ac.

These battery's go 6000+ cycles, perhaps more! Should be in all ev's over the throw away lithium ion crap.
But this is a lithium ion battery. LiFePO4 describes the positive electrode composition of just one specific lithium ion chemistry.

LiFePO4 was popular for many early lithium EV conversions, including electric vehicles built on gliders (chassis without powertrain) designed for engines. The Wheego LiFe is one of these, built on a Shuanghuan Noble, which in turn is a Shuanghuan imitation of a Smart ForTwo body on a Suzuki Alto chassis. Since then, almost all automotive manufacturers have turned to other chemistries for better performance, with LiFePO4 still popular in non-automotive applications where ease of battery management is particularly important.
 

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One reason for the popularity of LiFePO4 for recreational use (travel trailer and motorhome "coach" batteries) is that the operating voltage range of a set of four cells in series is reasonably compatible with nominally 12 volt lead-acid systems.

I'd try to charge them manually, supervised, with a car battery charger. It'll get bogged down to nearly zero volts as it's charging up, 2, 5, 10amps or whatever. Even that is only 0.04C, a 26 hour charge. Just make sure you disconnect it before the voltage of the cell rises above 3.3v.
I assume that you mean a set of four cells connected in series and charged at the "12 V" setting, or a pair of cells connected in series and charged at the "6 V" setting; either way it will go to at least 3.3 V/cell for these configurations, and normally higher.

One supplier of converter/chargers for RV use has a "lithium series" version which just simplifies the usual multi-stage charging program to a simple 14.6 volt limit (so 3.65 V/cell), which assumes that the battery is protected by its own BMS to cut off before overcharging.
 

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Discussion Starter #6 (Edited)
One reason for the popularity of LiFePO4 for recreational use (travel trailer and motorhome "coach" batteries) is that the operating voltage range of a set of four cells in series is reasonably compatible with nominally 12 volt lead-acid systems.


I assume that you mean a set of four cells connected in series and charged at the "12 V" setting, or a pair of cells connected in series and charged at the "6 V" setting; either way it will go to at least 3.3 V/cell for these configurations, and normally higher.

One supplier of converter/chargers for RV use has a "lithium series" version which just simplifies the usual multi-stage charging program to a simple 14.6 volt limit (so 3.65 V/cell), which assumes that the battery is protected by its own BMS to cut off before overcharging.

this sounds like the best way to go about recharging the cells, hooked in series with 12v. that way its like charging 9 cells instead of 36 separately.

Any issues with this? especially if I am using a laptop battery charger for example. How many amps should go into 12v (4 X 3.2v in series) of lifepo4 battery? they are each 260 AH cells.

at this point whats wrong with just somehow bypassing the BMS and charging my pack directly with 120v? bms wont power on until pack is at 80v... any ideas?
 

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Nothing if you can control the amperage, other than one cell if it has high resistance would have the potential to burn the vehicle and any structure it’s standing in to the ground. However some careful monitoring and putting the vehicle somewhere safe would negate this. If you can control the amperage going to the pack sans BMS then you could quickly bring the voltage up to 85v and then use the bms to do the rest of the work. But going cell to cell gives you the chance to check the resistance and potential risk of failure. It’s time consuming and boring but what’s the alternative, a hundred small chargers.? That’s a painful experience.
 

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this sounds like the best way to go about recharging the cells, hooked in series with 12v. that way its like charging 9 cells instead of 36 separately.

... How many amps should go into 12v (4 X 3.2v in series) of lifepo4 battery? they are each 260 AH cells.
Connecting cells in series changes only the voltage, not the appropriate charging current. For instance, as Matt explained with a 10 amp automotive charger, that's 10/260 = 0.04C (0.04 times the capacity per hour, and more than 26 hours to charge) - which is very slow - regardless of whether you are charging a single cell, four in series, or the whole set in series.
 

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I assume that you mean a set of four cells connected in series
Naw, I meant 1 cell, and just keep an eye on it.

He could do 4 at a time of course, but he wants to test them 1 at a time. And 4 at a time means he has to be switching back and forth and checking because nothing says that 3 aren't dead and 1 cell is taking 14.4 volts itself.

Bottom line, the voltage of the charger is going to get bogged down to whatever voltage the cell is. It's never going to "see" 14.4v, if the voltage is 2v and current is pouring in as fast as the charger can handle, then that'll be what it is. The battery won't ever "see" a higher voltage than it is charged to, so as long as you stop before it rises too high, you're fine.

Because the internal resistance of car batteries is nearly zero, (i.e. that's why they're starter batteries, 700 amps easy), chargers have to be designed to be overloaded gracefully... because a 10A charger is instantly overloaded when connected to a dead starter battery that's trying to suck 700 amps.

To stress, the key is to manually supervise them, because nothing stops the voltage from eventually rising and blowing way past (4x) the top limit.
 

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Discussion Starter #10
What about charging the entire pack (again its 36 3.2v 260ah cells ~30 kwh pack) with 120v and 2-3 amps over 4 days or so?

Even below 80v is that a bad idea?
 

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What about charging the entire pack [...] with 120v and 2-3 amps over 4 days or so? Even below 80v is that a bad idea?
For an extreme example, let's say that 35 of the 36 cells are dead and won't take a charge.

The 1 cell that will take a charge is going to see 120v. It maxes at 3.6v. You're going to blow it up too.

The more cells in series, the more likely you'll overcharge them and the bigger a negative impact that overcharging will have.

I'm normally game for some stupid shit in a controlled environment, but I don't think I'd do that, even as an experiment on known-to-be-dead cells.

I'd go get one or several junk computer power supplies from an electronics recycler (shoudl be free, but not more than $5/each if they're insisting), and rig yourself a 3.3v charger and get started charging. I suspect you're going to find out right away which ones flat out refuse to take a charge.

If you can't figure out how to wire the power supplies I'm happy to walk you through it.
 
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