A 48V 10.4 Ah battery mount with no connectors.

[nutnspecial]

What is the "it" in the above sentence that discharges the high cells?
What current for discharge?

'It' is a 'battery medic' or similar. I use the knock offs. Something like 300ma drain per cell, and they got hot @ that. See my post today in your other thread trying to explain my take on cells/batteries/balancing.

 

[Boyntonstu]

What is the "it" in the above sentence that discharges the high cells?
What current for discharge?

'It' is a 'battery medic' or similar. I use the knock offs. Something like 300ma drain per cell, and they got hot @ that. See my post today in your other thread trying to explain my take on cells/batteries/balancing.

Thanks,

You have been giving me good advice.

BTW After a dozen cycles, all my cells are in balance.

One thing is strange, my CV charger is set to 49.8V and for the last few days, both 6s strings measure 49.6V.

I measured the charger at the plug and it is 49.8V and the batteries are both 49.6V.

Can you explain it?

 

[nutnspecial]

Although I wouldn't worry at all about the small discrepency, that is interesting.

I find it interesting to observe voltage 'sag' up while charging, and likely this combined with the typical cv/cc charge profile is why you're not seeing a full charge.
Since amperage tapers to zero @ the set voltage, the charge becomes almost infintesimally slower as it completes 100%. Though I've never measured for it or tried rectification, I'm thinking you can either charge longer to get every last bit into the cells, or adjust voltage up (keeping same charge time) to offset the ramp down and cell sag, or leave it be.

 

[Boyntonstu]

Although I wouldn't worry at all about the small discrepency, that is interesting.

I find it interesting to observe voltage 'sag' up while charging, and likely this combined with the typical cv/cc charge profile is why you're not seeing a full charge.
Since amperage tapers to zero @ the set voltage, the charge becomes almost infintesimally slower as it completes 100%. Though I've never measured for it or tried rectification, I'm thinking you can either charge longer to get every last bit into the cells, or adjust voltage up (keeping same charge time) to offset the ramp down and cell sag, or leave it be.

As always, great advice.


I believe that I have a workable idea of how to assemble a pack without soldering or welding.

It would be slightly more involved than to replace an 18650 in a holder or a battery in a flashlight; but very doable.

 

[Boyntonstu]

I went for a 6 mile ride PA at 15+ mph in a loop with pretty strong winds.

Initial average cell Volts 4.15 (49.8V)

The discharge measurement was 4.07 (48.8V)

The four 6s 5200 Turnigys at 48V are pretty impressive after about 25 cycles.

They pack seems to be improving.

Last week I was seeing 3.94V (47.28)

Do batteries get better than this?

UPDATE:

250 mile : Batteries charge to 4.15 per cell average and hold the Voltage for at least 12 hours.

I discovered that I must isolate batteries from the controller and the charger to avoid leakage.

I am upping my average speed to 17.5 mph.

After a 6 mile rid the batteries went from 4.15 V to 4.02 V.

I am using the battery in a very narrow range and always above 3.9 V.

No balancing.

Pretty happy.

 

[Boyntonstu]

Bump UPDATE

 

[miuan]

No. Batteries do NOT get better. They deteriorate gradually from the first couple of cycles.
Furthermore, you are doing your battery no good by keeping it at high state of charge for extended period.
To improve shelf life and long-term performance, store it at lower state of charge, ideally between 3.75 and 3.9 volts. Charge it shortly before ride if you can.

 

[Boyntonstu]

No. Batteries do NOT get better. They deteriorate gradually from the first couple of cycles.
Furthermore, you are doing your battery no good by keeping it at high state of charge for extended period.
To improve shelf life and long-term performance, store it at lower state of charge, ideally between 3.75 and 3.9 volts. Charge it shortly before ride if you can.

I ride twice a day. When do you recommend that I store it at a lower voltage?

 

[Ykick]

A power meter would actually provide some meaningful battery performance data. This helps no one.

 

[dogman dan]

No the pack is not improving, but at any time, you can be learning to ride more efficiently. You might be gaining strength you have not noticed, after lots of riding. Feels the same to you, but pedaling harder.

If you ride and charge twice a day, as I used to on my 30 miles a day commute,, you pretty much are keeping your battery at full charge 18 hours a day. Some time at less when you ride, and the time it takes to get full again.

Better, if your setup allows riding to work, then not charging till you get home.

I would not sweat it, using it that much you are assuredly getting your moneys worth out of them. The one possibility open to you is some kind of timer, so your evening charge starts later. But that means charging lipo while you sleep. That's a huge no no In my world.

 

[Boyntonstu]

Would charging to 3.9 V or 4.0 V extend the life instead of going to 4.15 V?

 

[miuan]

Would charging to 3.9 V or 4.0 V extend the life instead of going to 4.15 V?

Absolutely. Unless you discharge the battery close to empty, where it quickly gets out of its comfort zone.
Generally, you want to stay as close to half charge as practical. Obviously, where you need a lot of range, just top the batt full and enjoy the ride.
You don't want to be a slave to your battery, nor abuse it.

 

[Boyntonstu]

Would charging to 3.9 V or 4.0 V extend the life instead of going to 4.15 V?

Absolutely. Unless you discharge the battery close to empty, where it quickly gets out of its comfort zone.
Generally, you want to stay as close to half charge as practical. Obviously, where you need a lot of range, just top the batt full and enjoy the ride.
You don't want to be a slave to your battery, nor abuse it.

OK Which one is closest to true? I will begin charging to 4.0 V because with 12s it is exactly 48.0 V.

from the web:

ts funny. I've found several charts since I posted. All of them differ.

4.20v = 100%
4.03v = 76%
3.86v = 52%
3.83v = 42%
3.79v = 30%
3.70v = 11%
3.6?v = 0%


4.00V--84%
3.96---77%
3.93---70%
3.90---63%
3.86---56%
3.83---48%
3.80---43%
3.76---35%
3.73---27%
3.70---21%
3.67---14%

This one is very pessimistic. The others have 50% at about 3.85v. This has 50% at 3.95v

100% 4.20 volts
90% 4.15
80% 4.10
70% 4.05
60% 4.00
50% 3.95
40% 3.90
30% 3.85
20% 3.80
10% 3.70

 

[Hillhater]

Results will vary depending on exactly which pack ( brand , capacit, age, etc) , was tested, who did the test, how the test was done, and very relavent...if they were measuring capacity in Amp hours or Watt hours ?

 

[dogman dan]

If all you ride is 6 miles per charge, then you will likely see a very long lifespan. I'd say for what your use is, charging to 4v makes sense.

I'm not sure you'd see significantly more life charging lower. But my experience is that keeping them above 3.7v keeps them very happy. At about 3.65v they start to really drop voltage, and pulling hard on them after 3.65v drives em out of balance more than low discharge rates.

What may actually kill your packs eventually is physical damage. So protect those corners. I believe you did. Crushed corners, and chafing kills more lipo than anything. People toss em loose in a bag, and they rattle around in there.

 

[Boyntonstu]

If all you ride is 6 miles per charge, then you will likely see a very long lifespan. I'd say for what your use is, charging to 4v makes sense.

I'm not sure you'd see significantly more life charging lower. But my experience is that keeping them above 3.7v keeps them very happy. At about 3.65v they start to really drop voltage, and pulling hard on them after 3.65v drives em out of balance more than low discharge rates.

What may actually kill your packs eventually is physical damage. So protect those corners. I believe you did. Crushed corners, and chafing kills more lipo than anything. People toss em loose in a bag, and they rattle around in there.

That is my plan.

After a 4.0 V charge to 48 V and 6.5 miles, they read 46.7 V or 3.89 V average.

I went a little further distance to vote.

 

[miuan]

OK Which one is closest to true?

This one seems the most accurate for Hobbyking lipo:
(no load voltage)

4.20v = 100%
4.03v = 76%
3.86v = 52%
3.83v = 42%
3.79v = 30%
3.70v = 11%
3.6?v = 0%

Actually, You can still extract about 3% past 3.6V but it will harm the battery.
I accidentally overcharged the Zippy to 4.53V once, and it took about 140% rated capacity!
RC racers do this frequently to gain edge on their competitors. Of course, you get a handful of cycles at best, before the battery fails or deteriorates.