Profiling Lester Summit II charger for LiFePO4 battery

[Pat911]

Sorry for assuming you’re in the US.

I don’t understand the point you’re making or the question you’re asking but 58.8v is the charger voltage, 55.8v is the battery voltage after it has settled. Remember that the BMS would have disconnected the charger some time prior to you turning the charger off because one or more cells rose above 3.65v.

Whilst the charger is connected you’ll read the charger voltage as it’s higher than the battery voltage. The instant you turn the charger off you’ll read the battery voltage. When using a charger of the correct voltage the BMS will keep the charger connected to the battery and the battery will continue to saturate once it reached the charger voltage. It will stay at the charge voltage whilst the charger is connected. Once the charger is disconnected the battery voltage will quickly begin settle.

Cheers
Pat.

[simicrintz]

Originally Posted by Pat911

There is no special customisation required for lithium battery chargers except for the Constant Voltage point. Getting one with an adjustable CV point gives you all the customisation you require. They are readily available from AliExpress, eBay, Amazon etc.

I wanted a charger that limited the voltage and amperage, kind of as a back up fail safe for my BMS (if that makes sense!). My feeling was/is that if I limit my voltage/amperage initially I am off to a safe start. Here is a pic of my charger with the info.

[Volt_Ampere]

Originally Posted by simicrintz

I wanted a charger that limited the voltage and amperage, kind of as a back up fail safe for my BMS (if that makes sense!). My feeling was/is that if I limit my voltage/amperage initially I am off to a safe start. Here is a pic of my charger with the info.

This is certainly what you want! The BMS is there as a BACKUP to prevent battery damage from overcharge / undercharge. It should not be doing that under normal usage. The only thing the BMS should actively do is balance the pack during charging. Your charger should control charge current / voltage correctly for your battery chemistry and size.

[Pat911]

Originally Posted by simicrintz

I wanted a charger that limited the voltage and amperage, kind of as a back up fail safe for my BMS (if that makes sense!). My feeling was/is that if I limit my voltage/amperage initially I am off to a safe start. Here is a pic of my charger with the info.

Hi Simicrintz,

That is exactly what a lithium charger is. It a Constant Voltage (CV) and Constant Current (CC) power supply. It will first limit the current to the CC setting and as the battery voltage rises, it will limit the voltage to the CV setting. At this point the current will taper off to zero. But the charger you posted has a sticker saying it’s for Lead Acid batteries, which is what you DON’T want, unless it’s been internally modified as per the second sticker, in which case it’s just a run of the mill lithium charger, nothing special. What’s your cell configuration as per your second sticker, 50v seems quite low and 2.9A is also awfully slow.

And, elaborating on what Volt_Ampare said, the BMS is the fail safe for the charger, not the other way around.

Cheers
Pat.

[simicrintz]

Hey Pat-

We had quite a few conversations with Schauer to make their charger work when the Lester that claimed lithium was figured out that it could not safely do the job (as I was initially told). This charger was modified by Schauer to specifically do my Chevy Volt batteries (which apparently are a little different than "normal" lithium). I will have to go back and look at what the configuration is (it has been a while and I have forgotten!).

I've been happy with the charger and setup (only have 1.17 hours on everything though!) and it has performed to my expectations!

[Pat911]

Hi Simicrintz,

All lithium batteries should be charged with the same CC/CV profile I described above, regardless of chemical composition. The only difference would be the CV point which needs to be calculated by using the maximum cell voltage, (or the maximum you want your cell voltage to get to) multiplied by the number of series connected cells.

The fact that your charger only charges to 50v would tell me that your battery pack is 12S. 4.167v (4.2v maximum Lithium Ion cell) x 12 = 50v

Cheers
Pat.

[simicrintz]

You are most likely correct on the configuration-I looked in my files and cannot find anything and it has been so long now that I cannot remember!

Your math seems to be correct and sounds like what we worked with back when. You are much smarter than me on this stuff (and I enjoy reading your posts) and I appreciate your input!

[Rockten]

Originally Posted by Pat911

This is the charger I use

https://www.ebay.com.au/itm/18464504...3ABFBMisbI4Odg

It’s not waterproof but I don’t need it to be. It has adjustable voltage and current and can fully charge a 100Ah battery in around 3 hours. It will operate from 110v but be aware that it will draw 2000W at full power, that’s over 18A from your mains supply. I don’t believe your standard receptacle can be used with that charger in the US.

Cheers
Pat.

Hello Pat. I am planning to buy the charger you suggested on ebay for my my LiFePO4 - 48v/80ah battery. However I see that it does not have cables for my 220v inlet nor does it have cables to clamp on the battery poles. Should I buy these separately? Do you have any suggestions what format they should be to fit this specific charger?

[Pat911]

Hi,

Unless you have experience with 220v mains wiring I would suggest a pre-wired solution, of which there are many, but not at that power level.

If you are going to purchase that one, my suggestion would be to purchase a 10A extension lead with the mains plug already attached and then cut it to the length you want. You can then terminate the bare wires to the power supply. The mains connections should be very well protected from ingress by foreign objects, especially fingers.

The output wiring should be at least 8g to minimise voltage drop. Keep it as short as practical. There are also multiple output terminals, 3 positive and 3 negative from memory. If you have problems with terminating larger cable, you can split it across 2 or more terminals, being sure to heatshrink any bare wire.

Use terminals, don’t just screw down bare wire. That goes for both the input and output.

Cheers
Pat.

[Rockten]

Originally Posted by Pat911

Hi,

Unless you have experience with 220v mains wiring I would suggest a pre-wired solution, of which there are many, but not at that power level.

If you are going to purchase that one, my suggestion would be to purchase a 10A extension lead with the mains plug already attached and then cut it to the length you want. You can then terminate the bare wires to the power supply. The mains connections should be very well protected from ingress by foreign objects, especially fingers.

The output wiring should be at least 8g to minimise voltage drop. Keep it as short as practical. There are also multiple output terminals, 3 positive and 3 negative from memory. If you have problems with terminating larger cable, you can split it across 2 or more terminals, being sure to heatshrink any bare wire.

Use terminals, don’t just screw down bare wire. That goes for both the input and output.

Cheers
Pat.

Many thanks Pat!