Lithium charging

[Tom47]

I still haven't received my ECO Battery yet, but I have a lifepo4 charging question I'd like to have explained.

I have read the 4.2 volts per cell maximum charge voltage or 58.8 volts for a 14 cell pack is what we should set the charger at.

The following article sort of advises against this. As the article says:

"The most common causes for premature failure of LiFePO4 cells are overcharging and over-discharging. Even a single occurrence can cause permanent damage to the cell, and such misuse voids the warranty. A Battery protection System is required to ensure it is not possible for any cell in your pack to go outside its nominal operating voltage range,
In the case of LiFePO4 chemistry, the absolute maximum is 4.2V per cell, though it is recommended that you charge to 3.5-3.6V per cell, there is less than 1% extra capacity between 3.5V and 4.2V."

If what they say is true, we are only supposed to charge to 49 volts, as 3.5 x 14= 49! I'm sure I am missing something here.

Please enlighten me so I can do the right charge when I get it going.

Reference Link: https://www.evworks.com.au/page/tech...-lithium-batt/

[Ronno6]

That would be a good question for ECO, BB, etal..........
My HSKY has a sticker on it stating that you should NOT charge at 60v....
That's all i know......

[WalterM6]

Your getting LiFePo4 and NMC batteries run together. For a Nominal 48v pack a LFE has 16 cells and is charged to 58.4 for a single cell voltage of 3.65V. A NMC(aka Leaf) has 14 cells and is charged to 58.8 for a individual cell voltage of 4.2v.

[Tom47]

Originally Posted by WalterM6

Your getting LiFePo4 and NMC batteries run together. For a Nominal 48v pack a LFE has 16 cells and is charged to 58.4 for a single cell voltage of 3.65V. A NMC(aka Leaf) has 14 cells and is charged to 58.8 for a individual cell voltage of 4.2v.

Ah, I see Walter! So the ECO Battery has 16 cells not 14 as I thought. Thanks for clarifying this for me.

I'm assuming the ECO branded charger is either factory set for 58.4 or is user adjustable like the Big Battery one is.

In charging the ECO, should I charge when down to 20 to 30% SOC and then let the charger complete the cycle and shut off?

[WalterM6]

I don't have ECO Batteries but I do have LiFePo4 batteries and I charge them after each use. I use a timer. From previous experience I know that a trip to Publix will require 1 and a half hours to recharge. So I set the timer. "They" say not to leave it plugged in all the time that's why I use a timer.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[Ronno6]

Originally Posted by Tom47

Ah, I see Walter! So the ECO Battery has 16 cells not 14 as I thought. Thanks for clarifying this for me.

I'm assuming the ECO branded charger is either factory set for 58.4 or is user adjustable like the Big Battery one is.

In charging the ECO, should I charge when down to 20 to 30% SOC and then let the charger complete the cycle and shut off?

Interesting factoid..... the BB charger fan is always running when it is plugged in.
According to them, the BMS tells the charger when the battery is fully charged, and prevents any further charge to the cells.........

[Pat911]

Originally Posted by Ronno6

Interesting factoid..... the BB charger fan is always running when it is plugged in.
According to them, the BMS tells the charger when the battery is fully charged, and prevents any further charge to the cells.........

NO! NO! NO!

The BMS should not be used as a charge controller. It is a Battery Management System. It is the last line of defence to protect your battery should your charger fail or you go into an over discharge condition.

Your charger should shut itself off, either via timer or once the current drops to 1/10 of the Constant Current value. Only if your charger shut off fails should the BMS intervene. If you rely only on the BMS to prevent overcharging and it fails, you can end up in a potentially dangerous situation.

The answers given in regard to LiFePO4 vs NMC and charging voltage are correct.

LiFePO4 = 3.65v max / cell (certainly not 4.2v as stated in the link above )
16 cells for a 48v battery
58.4v maximum charge voltage

NMC = 4.2v max / cell
14 cells for a 48v battery
58.8v maximum charge voltage

Lowering those maximum charge voltages by 0.05v to 0.1v per cell will extend the life of you battery without much loss in capacity/range (Less than 5%).

Cheers
Pat.

[Tom47]

Originally Posted by WalterM6

I don't have ECO Batteries but I do have LiFePo4 batteries and I charge them after each use. I use a timer. From previous experience I know that a trip to Publix will require 1 and a half hours to recharge. So I set the timer. "They" say not to leave it plugged in all the time that's why I use a timer.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Thank you, Walter! I've got a timer coming!

[Tom47]

Originally Posted by Pat911

NO! NO! NO!

The BMS should not be used as a charge controller. It is a Battery Management System. It is the last line of defence to protect your battery should your charger fail or you go into an over discharge condition.

Your charger should shut itself off, either via timer or once the current drops to 1/10 of the Constant Current value. Only if your charger shut off fails should the BMS intervene. If you rely only on the BMS to prevent overcharging and it fails, you can end up in a potentially dangerous situation.

The answers given in regard to LiFePO4 vs NMC and charging voltage are correct.

LiFePO4 = 3.65v max / cell (certainly not 4.2v as stated in the link above )
16 cells for a 48v battery
58.4v maximum charge voltage

NMC = 4.2v max / cell
14 cells for a 48v battery
58.8v maximum charge voltage

Lowering those maximum charge voltages by 0.05v to 0.1v per cell will extend the life of you battery without much loss in capacity/range (Less than 5%).

Cheers
Pat.

Thank you, Pat, for listing the correct procedure.

Is it also correct to charge after every use? I have heard not to, and to let the battery discharge 70 to 80% before charging.

I usually ride 5 miles a day with 18 to 20 mile runs twice a week. I'm not sure what the ECO will be able to do in that respect. It is 72ah and I'm hoping to get 20 miles easily. It is all flat land, seldom run at max 24 mph, and average 12 to 14 mph for the trip.

The ECO is coming tomorrow and I should have it ready to go by Saturday, if I can figure out where 2 wires disconnected when I wasn't looking!

[Ronno6]

Originally Posted by Pat911

NO! NO! NO!

The BMS should not be used as a charge controller. It is a Battery Management System. It is the last line of defence to protect your battery should your charger fail or you go into an over discharge condition.

Your charger should shut itself off, either via timer or once the current drops to 1/10 of the Constant Current value. Only if your charger shut off fails should the BMS intervene. If you rely only on the BMS to prevent overcharging and it fails, you can end up in a potentially dangerous situation.

Pat.

It is possible that I misunderstood what I was told, or that the info was incorrect.
I was told that the charger fan would never shut off....

I have to check the LED by the leads...
I know that, after charging for some time, the battery, when the charger is disconnected, has not risen above 54.4v, which I have been told is in the 100% charge range, and should rise a bit as I put some cycles on the battery.

Looks like I will lower the charger voltage to 58,4v.........

I have read that the lithium batteries should be run lower before recharging.
I'll revisit that when I get things going....