72v Lipo Bulk Charger Output?

[mybike]

I am going to update my lipo pack now to make 72v and bulk charge the pack.
I have emailed Paul at em3ev to set the charger voltage output and was told they will oblige.

The charger I have chosen is
Link: http://em3ev.com/store/index.php?route=product/product&path=35_37&product_id=153
It has 3 output settings.

Part of my email response:
Cells in series: 20 cells
Charge Voltage: (Typical Value) 83.25v

Charge Voltage: (Typical Value) 83.25v We can set it to 83.2V or 83.3V. Setting it to 2 decimal places is a bit too fine a tolerance.


My question is are the 3 setting below right and what they are for my 72v lipo pack?
100% = 83.2v or 83.3v? (they said Setting it to 2 decimal places is a bit too fine a tolerance)
90% = ?
50% = ?

 

[Syonyk]

How are you getting 83.25v?

A 20S pack with "standard" 4.2v cells will be 84v at 100% SoC.

Either one is fine. The difference in capacity at the very top end of the charge is minimal.

I'd set it to 83.2 and not worry about it.

 

[mybike]

Sorry I got this wrong don’t ask how . It pays to double check that’s why I posted and you can see I messed up right there

Below settings for the charger
100% = 83v (that’s 4.15v per cell)?
90% = ???v
50% = ???v

Please confirm the 3 settings be for this 72v pack and what should the other 90% and 50% setting should be?

 

[millzy555]

4.15v per cell should be pretty safe for longevity, any lower and you sacrifice top end punch. If its only pulling low amps you will be fine
Feel free to go to 4.10v if you're really keen to keep batteries long term

 

[dogman dan]

If you are going to bulk charge naked (no bms), 4.15v per cell is a good place to stop. This gives you an extra .5v of wiggle room on balance

Have them set 90% to 4v per cell. you can use that setting a lot, or charge to that, then the next morning, hit it with 4.15v just before you ride.

This is what I do with my 48v lipo packs, and it works great. If you are not discharging too deep or too high c rate, you can then balance your packs about 4 times a year, after sorting out any packs with a dud cell.

 

[mybike]

Thanks dogman dan clearing that up. Will be using the 90% setting and then before a ride then charge it to 100% setting 4.1v per cell. I have no BMS.
There are 3 settings on the charger is 3.5 per cell sound right for storage setting? (see my setting below I will email paul for the charger to be set at).

100% = 83v (that’s 4.15v per cell)
90% = 80v (4v per cell)
50% = 70v (3.5v per cell for storage)

 

[Syonyk]

3.5v is usually below 50%.

Assuming a standard chemistry, I'd charge to 3.65 or 3.7v/cell for storage.

 

[mybike]

OK thanks Syonyk
I will have the charger set to 3.7v per cell (74v) for 72v lipo pack for storage.

100% = 83v (that’s 4.15v per cell)
90% = 80v (4v per cell)
50% = 70v (3.7v per cell for storage)

Sorted! I will purchase the charger on Monday coming and message paul at em3ev to set the settings on the charger before shipping.

This will be my 3rd order from em3ev always had my orders within 7days to UK.

 

[wesnewell]

Personally I'd have them set to 84V, 82V and 77V for storage. 70V is too low for storage. I've been charging my 24s pack to 100.8V for over 4 years and 15K miles now. I just never let them sit at full charge for long before using it. Usually recharge once they get to 20% soc. Have never run them below 10% soc.

 

[cal3thousand]

4.15v per cell should be pretty safe for longevity, any lower and you sacrifice top end punch. If its only pulling low amps you will be fine
Feel free to go to 4.10v if you're really keen to keep batteries long term

I agree!

I actually run mine at 4.0V for 90% of the time, only charging to 4.2V for occasional top balancing and top speed runs. There is not a ton of energy at the very top .2 Volts. Like a rubber band, stretching it tighter hits harder, but for most intents and purposes, you don't need to stretch a rubber band to yield.

 

[mybike]

I will be pulling maximum 40Amps from my 72v lipo made up pack. At the moment I am running 55.5v and bulk charging this pack for over a year and recently brought and fitted a programmable controller from Paul.

4.15v per cell is perfect for my needs as longevity of lipo pack is what I am looking for. I balance the pack through the balance tabs one by one while still in series and parallel mostly to 4.1v rather then 4.2v had no problems so far.

 

[dogman dan]

Sounds like a good plan, though I'd store closer to 3.8v. Honestly, I rarely use the store charge on my Em3ev charger. I usually stop by 3.75-3.8v anyway.