How Low Do You Go (When To Recharge)

[Ronno6]

I am a tad confused over the safe level to discharge my Husky 105ah 48v.

The low voltage cutoff is listed as 43v
I have seen that the battery should not be used below 20% capacity, and
the charts indicate that this is about 52v.
My batt will show 53.8v or so immediately after charging. I never get anywhere near the max voltages published.It drops to 53v quickly when in use. Charts indicate that this is about a 75% capacity level.BB told me that the charge capacity will increase with discharge/charge cycles.

I have also seen that some of y'all charge every night.....

So, I turn my palms to the sky, shrug my shoulders and say.....Huh???

[DaveTM]

Interesting that your max charge is only 53.8V. My Nissian lithium pack, using my adjustable BMS, I have set to charge to a maximum of 57V.

So, your 53V would lead me to believe your leaving power "on the table" so to speak.

I do know that when my Voltage gets to 50.0 at a rest, it's time to charge or I'm not getting much farther as the LV relay will open up if I press for a lot of "juice" because any given cell will drop below the LV cutoff.

I know nothing about your unit....but is your max charge adjustable? What does the companies documentation say?

EDIT: when I look at the https://thebigbatterystore.com/produ...fhsky-24060-g1 Big Battery Store, they show a LifeP04 103AH will have an "operation range" between 43.v-58v.

I can only assume your setup is not being charged to the max. I dunno if that's a charger issue or a BMS issue, but I think you need to call either the place you bought it from, or the company...if they have a help line!

[Volt_Ampere]

What battery chemistry and how many series cells are in this Husky pack??? That makes a huge difference in determining state of charge (SOC) Leaf cells are 4.2V max per cell and most use 14 series with these giving 58.8V max. Most drop in's are LiFePO4 cells which have a lower cell voltage and a very flat discharge curve that makes it very difficult to predict SOC based on pack voltage. Most drop in's use 16 cells in series for a "48V" pack. You need to know all of these things to safely run a Lithium cart.
It is best to never run below 20% SOC and at that level, under load, the BMS may shut down the pack due to undervolt.

[Tom47]

Correct me if I'm wrong here. Your charger probably shuts off at or near 58.4 volts which is 100%. However, the settled charge is closer to 53.2 volts which is 90%. It drops from 100% to 90% in short order, just sitting.

My EB charger shuts off precisely at 57 volts. It is designed that way. Within 5 minutes, the voltage reads 53.2, which is 90% charge.

This is normal according to EB. This does not affect range or life expectancy. Charging every day if the charge is below 80% will not affect battery life.

[Volt_Ampere]

Sounds like those are LiFePO4 batteries. You can't tell SOC by voltage well enough to trust it so you need an SOC meter that measures delivered Amp Hours. The voltage will stay fairly constant all the way down to almost empty if those batteries are LiFePO4 chemistry.

[CP241]

Originally Posted by Volt_Ampere

Sounds like those are LiFePO4 batteries. You can't tell SOC by voltage well enough to trust it so you need an SOC meter that measures delivered Amp Hours. The voltage will stay fairly constant all the way down to almost empty if those batteries are LiFePO4 chemistry.

What he said

I’ve got allied 90aH and my charger maxes at about 58.2. Once unplugged the voltage drops pretty quickly. Next morning it’s at 53.8 or so. If I let it sit a few days and don’t drive it, it settles at ~53.2and stays there pretty much indefinitely.

That said, I can get in my cart and drive it 10-15 miles. Again if it sits for a few days it will find its way back to about 53.2v

This tells you that the discharge curve on the lifepo4 batteries is very very flat. It doesn’t hardly ever drop below 50v even full pedal accelerating, up a hill pulling 125-130 amps.

Get yourself a good shunt based meter. These count the electrons flowing through the shunt for an accurate state of charge. I have the renogy 500A meter and really like it. Probably overkill with a stock controller and motor that never exceeds 150A but that’s okay :). Think I paid 80 bucks for it on Amazon. but there’s others out there. Victron makes some nice ones as well that I’ve used in other applications.

[Ronno6]

I charged this morning.
The readout rose to a max of about 55.6, at which time the BMS stopped the charging, and the readout on the battery went up to 59.2. I believe that
is the output voltage of the charger.
I'm not sure how the charger and battery interact at that point.
Shutting off the charger saw the readout drop from 55.6 and settle at 54.8v.
A short rub dropped it to 53.4...........

As my Chevy Truck project has stalled while waiting for the body shop to take over, maybe I can get back to installing the Renogy 500........
I gotta buy some cable and connectors for the project..

[Volt_Ampere]

Renogy sounds like what you need for your type of battery.

[Pat911]

59.2v seems a bit high, I wouldn’t expect to see anything above 58.4v assuming 16S configuration. It seems that your BMS is terminating charge which means that your cells are not saturating, they are just being bulk charged. We can’t be certain if it’s terminating because it’s set to do so at 55.6v (3.475v/cell) or your pack is unbalanced and one cell is peaking.

The BMS should not terminate charge unless the pack needs protecting. The charger should be set to an appropriate voltage that will allow the cells to bulk charge at the full current then saturate down to a reduced current of about 1/10 or so of the bulk current. This will ensure a full pack while keeping maximum voltage down. With LiFePO4, over 99% SOC can be achieved at a charge voltage of 3.45v/cell, followed by adequate saturation. If your pack is balanced you can reduce your charger voltage down to 55.2v and still achieve close to 100% charge.

Just reiterating the main points mentioned by others above.

NMC and LiFePO4 cannot be compared in terms of voltage
The Husky is LiFePO4
LiFePO4 discharge curve is very flat and despite what manufacturers publish, cannot be used to determine SOC.
LiFePO4 full charge voltage will settle considerably after the charger has turned off, NMC not nearly as much.
Both will drop considerably during the top 10% of SOC
Once again, voltage cannot be used to determine the 20% recharge point.
Get yourself a Renogy 500A shunt SOC meter.

[Ronno6]

I HAVE a Renogy 500A, just have not installed it as yet..... Still working
on component layout.

I spoke with the BB Tech guy today.
He said I should recalibrate my charger to 58.8, even tho it was set to 61v from the factory. Time to get out the DVM........
He said that the resting voltage of 53.2 represents a 99% SOC, and that I should run the voltage down to 51.2v before recharging. He stated that 51.2 is 20% SOC.
So.............