48v 20ah 3.2v 16s Battery LiFePo4 - I'm New at This

Hi everybody, I am new to this whole world of batteries and chargers and need your help!

I have a 48v 20ah 3.2v 16S Battery that is LiFePo4, the Ebay store I got it from has these very scary and cheap chargers and the last one I got literally melted, a resistor got so hot the side of the charger MELTED! The seller is sending me a new one to which he assures me to brand-new but I want to buy a nice charger, under $100 for it.

I bought a Luna Cycle 48v charger, but after a little bit of my own investigation I soon realized It only charges to 54.6v which if I am correct would be A undercharge for my battery. The seller whom I bought my battery from gave me a list of specs which I will provide here:

* Voltage : 48V
* Capacity: 20Ah
* 1xparallel ,16 x series
* Size (L x W x H): 220*150*175mm / 8.66*5.9*6.9 in
* Weight: 9.7kg / 21.4 lbs
* Cut-off voltage: 40V
* Max. discharging current: 100Amp
* Max Continuous Discharging Amperage: 50 Amps
* Rated Discharging Amperage: 50 Amps
* Charging Current: <=10 Amps
* Charging Voltage: 58.4Volts
* Lifecycle: > 85% capacity after 1000 cycles.
* Lifecycle of single cell: >85% capacity after 1500 cycles, > 70%capacity after 3000 cycles. (<1C discharge rate and <1C charge rate)
* 48V 20Ah Lithium LiFePO4 Battery Pack is made of 16pcs of 20000mAh Lithium Cells
* One Special 16cells PCB with balance function is installed with battery pack to protect battery from over charging, over discharging and over drain


However, I found another Luna Cycle charger for a 52v battery, it says it will charge until the battery reaches 58.8v which is about .4v over what my seller said the charging current should be. Will this cause me issues if I use it? Is .4v a big deal? I assume it would be.

Here are the links to the Luna Cycle charger I want to get:

https://lunacycle.com/luna-charger-52v-advanced-300w-ebike-charger/

Here is the link to the one I got:

https://lunacycle.com/48v-3amp-luna-mini-charger/

Here is a link to my battery in-case you need it:

https://www.ebay.com/itm/192747045148?ul_noapp=true

I thank you in advance for any help you provide, I'm new to this and really need to be steered in the right direction, if you know of any charger manufacturers that are good but won't coast me more than $100 I'll gladly look into it.

G'day and welcome.

LiFePo4 cells have a maximum charge voltage of 3.65V per cell. So for your 16S pack, that would be an absolute maximum of 58.4V total (I see you have established that already). Do not charge to 58.8V, that will shorten the life of the pack.

The good news is that there are many, many options. You *may* be able to open that 48V Luna charger and adjust the top voltage. If you remove the outer case and look for an adjustable trim pot like this:

https://endless-sphere.com/forums/viewtopic.php?t=51407

you might be able to find one that will change the maximum output voltage. You would have to test the output voltage with a multimeter etc...

Another option:
Use an adjustable LED driver like this one:
https://www.mouser.com/ProductDetail/709-HLG185H-54A?r=709-HLG185H-54A
you will be able to dial it in to the exact voltage you need

I have a "48V" 25Ah LiFePo4 pouch (16S1P) battery pack with, what seems to be, the same 5A charger as in the link to your battery pack. It has been, and is, working great. The problem you might have had with the melting could be from the cooling fan not working. So a new charger from the seller might be fine.

The charging voltage of these chargers is 60V (I have measured and confirmed this with mine). As it is a switching power supply it will put out a constant current (5A) in the beginning of the charging cycle and the voltage will be slowly rising as the pack is charging. As the voltage reaches a certain level, the power supply will switch to low current and the BMS (PCB) of the battery will start balancing the cells. I have measured my BMS to balance the cells at 3.5V (x16=56V). If your BMS does the same, a charging voltage that is slightly higher is needed to get the cells balanced. The maximum advised cell voltage of these pouch cells is 3.65V (x16=58.4V) but lower is better for battery life.

As you already have a Luna charger (which one/how many amps?) I would open that up and post photo's of the board up here. There is a chance there is a trim pot you can adjust to tune the output voltage to 58.4V. That way you don't need to buy a new one. And can keep the replacement that the seller is sending you as a back up or at another location (work or on the bike) for charging. The best thing you can buy at this moment is a digital voltmeter to measure the voltages of the chargers and your battery pack.

Ping the king of lifepo4 sets his chargers to 59volts so not a big problem. Lifepo4 can take a slight over charge not like lipo or 18650. Different chemisty. I only charge my lifepo4 to 3.5v not bms.

Thanks for all your replies, I will go and open the Luna charger and post it's picture here.

55.2V would be my 100% stop point at a low (.2-.5C) current.

At higher rates say up to 1C with no CV maybe 56V.

Higher than that hurts longevity but say 57V.

pwd said:

G'day and welcome.

LiFePo4 cells have a maximum charge voltage of 3.65V per cell. So for your 16S pack, that would be an absolute maximum of 58.4V total (I see you have established that already). Do not charge to 58.8V, that will shorten the life of the pack.

The good news is that there are many, many options. You *may* be able to open that 48V Luna charger and adjust the top voltage. If you remove the outer case and look for an adjustable trim pot like this:

https://endless-sphere.com/forums/viewtopic.php?t=51407

you might be able to find one that will change the maximum output voltage. You would have to test the output voltage with a multimeter etc...

Another option:
Use an adjustable LED driver like this one:
https://www.mouser.com/ProductDetail/709-HLG185H-54A?r=709-HLG185H-54A
you will be able to dial it in to the exact voltage you need

Click to expand...

999zip999 said:

Ping the king of lifepo4 sets his chargers to 59volts so not a big problem. Lifepo4 can take a slight over charge not like lipo or 18650. Different chemisty. I only charge my lifepo4 to 3.5v not bms.

Click to expand...

Top of charger in-case you want to know it's specs:
View attachment 3

Top:
View attachment 2

Closer:


REALLY CLOSE:


What do you guys think? Send it back and deal with the overcharge of the new one? Or adjust this 48v one to charge just right?

Now we need to wait for the electronics experts (I'm not...) to determine which of the 3 blue trim pots (with white glue) is for the output voltage. Maybe even the current could be upgraded to 4 or 5A with one of them.

As mentioned before, the output voltage can be up to 60V but ONLY when there is a BMS to protect the cells. As the ad on Ebay for your battery pack says there is a: * One Special 16cells PCB with balance function is installed with battery pack to protect battery from over charging, over discharging and over drain you should be okay with the higher charge voltage. And the 60V charger that came with your battery pack was a 5A instead of the 3A you got from Luna. So charging time will be a lot less with the replacement that will be sent to you.

Electricbike.com has a tutorial on that exact charger I couldn't find it. Spinning magnets probably knows word is.

One of the blue pots will adjust the voltage but I don't know which one.
LiFePO4 can tolerate quite a bit of over voltage on charging. I normally charge to 3.65v/cell (58.4v for 16s). This is really close to the voltage for a 14s Li-ion pack. Most spec sheets for LiFePO4 state maximum cell voltage = 4.2v, which is way higher than you would want to go.

Thanks for all your suggestions, I contacted Luna Cycle and they just waived their 10% restocking fee, so I'll be sending it back and using the charger from my Ebay seller, I would adjust the pots on the Luna if it wasn't for the fact I'm brand-new at all this and it's beyond me to start messing with this crap.


However, if you know of any chargers that are good and cost less than $100 let me know, I just want to have a good charger as a backup!

Thanks!

Lifepo4 can be charge to 3.7v with a bms which will bleed it down to a little lower and does rest at 3.5? Volt and if rode 1/2 mile will be at 3.4 volt. I haven't use bms as I have 20ah so big enough to self monitor and use up to 16ah or so. 5yr 1,380 cycles 23,000 miles and going . Good luck.
Ping sells a 48v 5a charger with a adjustable voltage pot. I think kingpan.

999zip999 said:

Lifepo4 can be charge to 3.7v with a bms which will bleed it down to a little lower and does rest at 3.5? Volt and if rode 1/2 mile will be at 3.4 volt. I haven't use bms as I have 20ah so big enough to self monitor and use up to 16ah or so. 5yr 1,380 cycles 23,000 miles and going . Good luck.
Ping sells a 48v 5a charger with a adjustable voltage pot. I think kingpan.

Click to expand...

Alright, I'll buy them, thanks for your help!

Yes 7yr old and still working. I turned it up to 73v for two months and it pop a cap 63volt cap. So found a 100v cap and turned it up to 84volts. Don't know how many amps but it was the 5 amp model which is the better model the 2 amp model it just has a plastic box and I don't think it's adjustable. I only use it now as a backup but it seems to work I just don't have an amp gauge to measure deadz charging at 84 volts . Plus ping is a good man.