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Seeking Recommendations for Top-Balancing Charger for 1yo LiFePO4 Batteries (UK)

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bazzatron

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Hello,

I'm seeking recommendations for a charger that can top-balance my 1yo LiFePO4 batteries before integrating them back into my system.

Here are the details:
  • Battery Configuration: 4 x 3.2V LiFePO4 cells in series
  • Capacity: 280Ah (total for all cells)
  • Individual Cell Voltage Variance: 3.345V - 3.63V
I plan to put the cells in parallel for top balancing, but I need guidance on selecting the right charger I can't find a suitable charger for a 3.2V cell. Safety features are essential since I'm unsure about the maximum charging current (A) for my specific battery setup, can't find a datasheet on them.

Affordability is a factor, but not at the cost of compromising reliability. (able to set a charge cut-off would be a good plus)

Any help would be invaluable in helping me find the best charger for this task, looking for experience-based recommendations only please?.

Thank you for your assistance.

Barry
 
You might just put a good active balancer on the pack so you don’t have to disassemble them or use a resistor or auto headlight to pull some power out of the runner cells individually
 
What issues are you having that has resulted in requiring a top balance?
Do you have 4 cells each rated 280 Ah?
When used as a 12v battery what make and model BMS was used?
How was the battery charged and what chargers?

It's possible to get a good cell balance by leaving the cells connected in series , with a BMS connected, and manually bleeding down the high cell with a load across that cell. A vehicle filament headlamp bulb is a useful load. Have the battery under charge with a 12v battery charger, and monitor the cell volts, a BMS with a Bluetooth connection is useful here. Identify the high cell, apply the load whilst monitoring the cell volts. The aim is to lower the volts to match the lowest in the group. This will take several seconds to tens of seconds. Play 'whack the mole' , with the load across the high cell in the group.
After some practice you will be able to estimate the time needed. Stop the charge if things are happening too fast. Aim for about 50 mV difference with the cell volts in about the 3.50 V range. The BMS should be able to deal with the balance from that point.

Mike
 
Last edited:
mikefitz said:
What issues are you having that has resulted in requiring a top balance?
Do you have 4 cells each rated 280 Ah?
When used as a 12v battery what make and model BMS was used?
How was the battery charged and what chargers?

It's possible to get a good cell balance by leaving the cells connected in series , with a BMS connected, and manually bleeding down the high cell with a load across that cell. A vehicle filament headlamp bulb is a useful load. Have the battery under charge with a 12v battery charger, and monitor the cell volts, a BMS with a Bluetooth connection is useful here. Identify the high cell, apply the load whilst monitoring the cell volts. The aim is to lower the volts to match the lowest in the group. This will take several seconds to tens of seconds. Play 'whack the mole' , with the load across the high cell in the group.
After some practice you will be able to estimate the time needed. Stop the charge if things are happening too fast. Aim for about 50 mV difference with the cell volts in about the 3.50 V range. The BMS should be able to deal with the balance from that point.

Mike
Click to expand...
1. I am finding that I get a quick drawdown on the Bat. lasts a day on 90 %SOC before my Vic. BMV bleeps. running 2 fans@90Ah plus a few led lights with a minimal draw, and a Fridge at about 17Ah.

2. All cells are the same bought at the same time.

3. Daly 120A

4. 500W Solar, 60A Vic. MPPT. Plus a Sterling B2B while driving.

I have a cellmeter 8 I will use to monitor and try your recommendation for the headlamp.

Thank you!
 
The Victron BMV will beep depending on the level set for warning, it may be the BMV is not set up idealy.
However things seem to be not working as they should so getting the cells better balanced is useful.
You can pull lots of useful info from the solar controller and BMV to help the Investigation.
 
mikefitz said:
The Victron BMV will beep depending on the level set for warning, it may be the BMV is not set up idealy.
However things seem to be not working as they should so getting the cells better balanced is useful.
You can pull lots of useful info from the solar controller and BMV to help the Investigation.
Click to expand...
So I took your recommendation and used a headlamp to get all the cells down to the same V just happened to be 3.334v

I then used a smart trickle charger set to 5A it cut saying the bat. Was full. for some reason the 4th cell charge up to 3.9v?! The third went up to about 3.5v. Then lower on 2nd and no change on 1st. They are all In series. Any advice?
 
bazzatron said:
the 4th cell charge up to 3.9v?! The third went up to about 3.5v. Then lower on 2nd and no change on 1st. They are all In series. Any advice
Click to expand...
Don't charge without a BMS to limit cell volts. Why did you do this?
 
mikefitz said:
Don't charge without a BMS to limit cell volts. Why did you do this?
Click to expand...
Don't worry, the negative clamp is going through the BMS.

It sounds like you've got quite the runner there, and my first suspicion is that Daly BMS not doing its job right or at all. If your trickle charger doesn't have a specific LFP setting, it's probably using the default lead acid voltages and think the battery is full based on voltage.

Will uses a desktop variable power supply in his demonstrations and I have used it for all my battery builds. I made a wire harness out of some 14awg wire, large butt connectors, and ring terminals so I can easily connect to all the batteries at once with decent gauge wire. One thing I have learned though is when you set the voltage, go for 3.64v because it tends to walk up the voltage a hair at the very tail end due to low draw. It's gonna take a while but since your battery is pretty much full it should be done in a few hours.
 
To properly balance cells you need to either top or bottom balance. You can not balance at some number like 3.334 as the only way to know you have the exact same state is to fully charge to 3.65 (LFP). You get anywhere near that number and the cells are within a percent or two of full.
 
Cell volts at 3.9 implies charging without a BMS giving protection , or a BMS with incorrect protection values. These How did you connect the charger to the series cells?

When using a load a across the cells to balance it should be whilst the cells are under charge and the cell voltages are over 3.4 volts.
The aim is to get resionable balance at around 3.55 to 3.60 volts per cell.

Mike
 
bazzatron said:
Hello,

I'm seeking recommendations for a charger that can top-balance my 1yo LiFePO4 batteries before integrating them back into my system.

Here are the details:
  • Battery Configuration: 4 x 3.2V LiFePO4 cells in series
  • Capacity: 280Ah (total for all cells)
  • Individual Cell Voltage Variance: 3.345V - 3.63V
I plan to put the cells in parallel for top balancing, but I need guidance on selecting the right charger I can't find a suitable charger for a 3.2V cell. Safety features are essential since I'm unsure about the maximum charging current (A) for my specific battery setup, can't find a datasheet on them.

Affordability is a factor, but not at the cost of compromising reliability. (able to set a charge cut-off would be a good plus)

Any help would be invaluable in helping me find the best charger for this task, looking for experience-based recommendations only please?.

Thank you for your assistance.

Barry
Click to expand...

These are fairly cheap converted server power supplies. The only downside is they don't have a current cutoff. There are other telecom power supplies on Aliexpress that are quite powerful and have some features including current cutoff, capacity limit cutoff, etc in the 2000W to 3000W range for $120 to $250. You won't touch any "professional" product in that power range for that price. I like the look of the ZTE chargers but they are the priciest of the bunch at $250'ish or higher but for a 3kw charger itspretty impressive (running it on 110V is going to cut the current output in half....I typically look at the 0-60V 0-50A model but they have a 0-120V 0-25A model if run on 220V-240V)

Now as far as top balancing....if this is your standard top balancing new cells that were shipped at 30% SOC this kind of high amperage charger is great since it SHOULD be able to get down to 3.65V...might have some loss in power in terms of current when you use a low voltage, might want to ask the seller how it performs at 3.65V. I've seen a couple of them reviewed on YouTube for charging 4S 12V packs and people seem to love them. For a budget minded person living the van life this could be a lifesaver in terms of getting them something that can charge their 200-400Ah of 12V batteries in an afternoon to get them back going after a couple rainy days if they don't have DC to DC charging off their alternator. I don't know of any other option approaching 100A of 12V charging power this cheap.

For actual balancing you'll want an active balancer (most cost effective method at $10 for a 4S 5A balancer). Keep in mind the amperage number on the active balancers is only seen when the cells are 1V apart. The closer they get, the less current there is balancing the energy around.

For more expensive but still cheap options the ToolKitRC M8S is an 8S hobby style charger packed full of features. Bonus points is it can do 24V LiFePO4, a lot of hobby chargers only go up to 6S. The old M8 and early firmware versions for the M8S had issues but it has all been smoothed out. It is a little bit of a pain in the butt with calibration as it seems to lose voltage and current calibration any time you do a high current charge that gets the charger quite warm. The internal fans SUCK and heat dissipation slits in the charger shell suck. I use a PC fan to help compensate for that failure. At about $45 its an insanely feature stuffed charger/discharger (fairly low power if just using the "internal" setting, has an external setting that works great with power resistors and a regenerative setting capable of the full 400W/18A of power like an iCharger which is awesome). Tons of RC related features for servos and whatnot (shit I'm clueless about). Best of all it has a power supply feature. I believe 0-30V 0-18A. Charger is max 400W/18A, balance current is 800mA, voltage input 7-30V so it will boost a 12V input but two HP DPS 460W server power supplies in series at ~25V is a great $30 option to get its full potential and its only running those power supplies at 50% of their rating when max'ed out.

You can get $8 HP DPS 460MB's if you are patient on eBay. Might have to buy 2 at a time but I've never spent more than $10 shipped on an MB and $8 shipped on an EB. I've seen 4 packs of EB's go for $24 shipped. I got lucky and snagged a refurbished still in the packaging MB for $10 and a good condition used MB for $8. I think the only difference is efficiency.

www.ebay.com

(Lot of 2)Genuine HP Switching DPS-460MB A Power Supply 643954-101 HSTNS-PL28 | eBay

Find many great new & used options and get the best deals for (Lot of 2)Genuine HP Switching DPS-460MB A Power Supply 643954-101 HSTNS-PL28 at the best online prices at eBay! Free shipping for many products!
www.ebay.com

I think this is a two pack of earlier models for $14 shipped...not 100% sure but can't say if the mod is identical. Most likely is. I prefer working on the EB's or MB's
www.ebay.com

HP HSTNS-PL14 460W Switching Power Supply 100-240V AC - Lot of 2 714752147431 | eBay

Find many great new & used options and get the best deals for HP HSTNS-PL14 460W Switching Power Supply 100-240V AC - Lot of 2 at the best online prices at eBay! Free shipping for many products!
www.ebay.com
Y Cable (I found a cheaper one on Amazon but its 2x C13 to 1x C14 and I would much rather have this style):
www.cdw.com

Tripp Lite 6ft Power Cord Y Splitter Cable 5-15P to 2xC13 10A 18AWG 6' - power splitter - IEC 60320 C13 to NEMA 5-15 - 6 - P006-006-2 - Power Cables - CDW.com

Buy a Tripp Lite 6ft Power Cord Y Splitter Cable 5-15P to 2xC13 10A 18AWG 6' - power splitter - IEC 60320 C13 to NEMA 5-15 - 6 at CDW.com
www.cdw.com www.cdw.com

I bought this Nylon M3 kit because I converted more than one set of two PSU's into a 24V:
All you really need are enough pieces to isolate the DC board on the #2 PSU aka the Floating PSU. #1 stays untouched. You could do it with maybe 4 washers, two 12mm screws, and like 4 nuts. So if your local hardware store happens to sell this stuff individually or in small packs maybe go that route but this was much easier and has enough hardware to convert like 40+ PSU's into 20 24V PSU's.

I think I bought 110mm shrink for individually wrapping each PSU and then 220mm for wrapping them together? Pretty sure those measurements are correct for the 460W PSU's. I also added a layer of electrical tape (would have used barley paper if I had some at that time) on top of the bottom unit for another layer of safety.
Cost for 1m of each size on Aliexpress was like $3 each tops. Cheaper if you bought 5m or 10m....might as well if you make 18650/21700 battery packs.

I chose to use these 4mm banana plug/binding posts on the first one I made. They are kinda big though....so used something different for the second one I made

Second one I bought something like this off Aliexpress
www.ebay.com

10Pcs High Current M5 Type 4mm Female Banana Jack Socket Binding Post Connector | eBay

Find many great new & used options and get the best deals for 10Pcs High Current M5 Type 4mm Female Banana Jack Socket Binding Post Connector at the best online prices at eBay! Free shipping for many products!
www.ebay.com
Could these be higher quality? Maybe?
www.ebay.com

5 Pairs Binding Post M5 Thread Power Amplifier Connector Banana Plug Jack Socket 784958400944 | eBay

Find many great new & used options and get the best deals for 5 Pairs Binding Post M5 Thread Power Amplifier Connector Banana Plug Jack Socket at the best online prices at eBay! Free shipping for many products!
www.ebay.com

For the 4mm banana sockets I used a dremel and sanded flat one edge and then soldered that to the pad on the PSU. Lots of different ways to do it, ideas all over RCGroups and Thingiverse. Thingiverse also has cases for covering the terminals.
 
Last edited:
Then I used these Hirschmann style banana plugs (knockoffs but quality is good). I had to use a drill bit and carefully remove some of the rubber inside the banana plug insulation so I could fit 12 AWG silicone insulated wire (BNTechGo from Amazon is what I usually get. Not always the cheapest, but close and reliable quality)

BNTechGo 25ft Red 25ft Black 12 AWG Silicone Insulated Tinned Copper Fine Stranded Wire

I considered using ferrules but the 12AWG conductor fit nice and snug in the banana plug and didnt spread the strands out terribly when I put the little grub screw in.

And of course on the end of the main positive and negative cable is an XT60 female that plugs into the M8S charger input. Its main output is XT60 female as well. Balance port is standard 2.54 JST XH.

Technically 1 set of 12AWG silicone wire with those parts should handle nearly the entire current of the PSU (38A) but thats really pushing it and 10AWG would be better but wont work with standard 4mm banana stuff as far as I know. So you can double up on banana sockets for the outputs and still use 12 AWG and only have 19A running through each cable. Maybe have a project box with 2 red/2 black banana sockets wired to a panel mount style XT90 so you can use 10AWG or 8AWG for the entire 38A current if you want to power something else that needs 24V 38A or 900+ watts.

And that's the entire list for how to make a 24V power supply dirt cheap along with the connectors if you are a fan of 4mm banana. Some people drill through the pads and use copper bars bolted down with other types of connectors or just attach ring terminals or lugs. Some people just solder wire to the pads.

Some people add a simple 2 pole on/off switch to the traces on the side that need to be joined with either a resistor or (I think) you can totally get away just by bridging them. Cool idea if you need an on/off switch. I use IR remote controlled outlet thingymaboppers.


The iCharger S6 is like $120-$140 but a powerhouse of a 6 cell charger. The X6 and X8/X10/X12 are slightly less powerful but the X8 gives you 24V capability. I'd still probably stick with the S6 unless I had a 24V system. NOTHING comes close to the S6 in that form factor.
Honorable mentions: ISDT Q6 series and ISDT Q8 series. Starting at $35 with the Q8 max topping out around $90. Great options as well.
At $82 the Q8 max gets close enough to the S6 to not make sense though
S6 at $130 at Progressive RC
 
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