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How long is this Top Balance going to take!

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bass-o-matic

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Oct 26, 2023
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Austin, Texas
I'm in no rush and I hear the slow method is the best for longevity of the cells but since I've only gone down an amp in 4 days.... new 280AH EVE cells...

1. Am I really looking at 4 weeks for this to finish? See pic.

2. Another question. In one vid someone mentioned putting a blocking diode on the + Terminal. Is this what we're talking about? https://a.co/d/1lVR6Kn
I've actually never seen anyone actually use on the YouTub.

Cheers

ddd.png
 
Do you have a BMS? You can connect it, and crank the voltage up to 14V to get the bank close, then when the BMS disconnects put the cells back in parallel and final top balance it.
 
I like it. Yes sir. I have an Overkill 120A 4S BMS. Although, I'm still waiting for my EG4 30A charger to ship... I guess I can leave it on till I get the charger. Then do was you suggest. Thanks!
 
As mentioned, throwing the BMS on there and just using a regular battery charger will do a LOT of the initial charging. Otherwise you're looking at 280a * 4 cells = 1120a /5a charging = 224 hours or about 10 days via the slow method. Off the shelf car battery chargers are often 10a or more. Mine can do 25a and it cuts the initial charge time down to about 8 hours for a new pack. After it's done it's only about 8 or 10 hours to top balance via the bench charger from there.
 
Something is off with that picture.

Why are you charging 4 cells in series at 3.65v? Or did I read the charge display wrong?

Edit I see they are in parallel.
 
Your supply maxes out at what, 10a? Anything over 16awg is way overkill. The alligator clips are probably your biggest slowdown, other than you're only feeding 20 watts into a 3000w battery. BMS and a car charger, big improvement!
 
Rednecktek said:
Your supply maxes out at what, 10a? Anything over 16awg is way overkill. The alligator clips are probably your biggest slowdown, other than you're only feeding 20 watts into a 3000w battery. BMS and a car charger, big improvement!
Click to expand...
Oops. Yea, that makes sense. Oh well, I made some 8 Guage leads. Now it's cranking BUT.... no matter how I adjust the Voltage on the power supply it wants to go to 3.66 not 3.65. What am I missing?
dd.png
 
Ok, I may have overdone it. The Power supply manual says something about Resistance Decreasing... go into Constant Current mode vs Constant Voltage... maybe I'll just put ring terminals on those leads... and not use the crazy 8 gauge leads.
 
Ok, I'm back to normal but better than I was before. EG, more amps going in. I don't fully understand it but I feel like CV is what I want not CC. So, I actually read and consumed what you guys are saying and put ring terminals on my 16g leads. Now she seems happy. I can live with this input I think.

ddff.png
 
If your power supply is anything like mine it'll drift a little as it gets to the top, might want to get the voltage down to 3.64 so you don't blow past 3.65. If it's capable of 10a and it's only soaking in 6.6 then it's getting pretty close to full. Almost there, be patient!
 
bass-o-matic said:
Ok, I'm back to normal but better than I was before. EG, more amps going in. I don't fully understand it but I feel like CV is what I want not CC. So, I actually read and consumed what you guys are saying and put ring terminals on my 16g leads. Now she seems happy. I can live with this input I think.

View attachment 176462
Click to expand...
Make sure you are setting the voltage before connecting it to the battery bank!
Use a trusted meter to verify the voltage on the display is accurate. Set the voltage with 0 load then turn it off and connect it to the pack. Do no adjust the voltage with the power supply connected to the pack!
There is an excellent top balancing guide in the resources section.

Welcome to the forum.
 
We jumped through all the same hoops as the OP when we assembled and parallel top-balanced our first 200ah 4s pack.

Don't do it anymore--just too much hassle. Nowadays, we install the BMS along with a $25-$30 switch-activated Heltec 5a 4s active balancer, charge normally, wait 1-2 hours for the cells to balance then switch off the Heltec, then call it a day. If the cells need rebalancing, simply switch on the Heltec again. No monitoring or hoops required.
 
Last edited:
Supervstech said:
NEVER ADJUST VOLTAGE WITH BATTERY CONNECTED!!
Click to expand...
Got it. Just checked again by:
  • Turning off the power supply.
  • Disconnecting the ground lead at the power supply.
  • Turn on the power supply.
  • Adjusting the Voltage on the power supply.
  • Reconnecting the ground at the power supply.
All seems well. Thanks for the tips!

I'm enjoying this learning process but this might be my only build? Depends on if the friends start asking for them. It's possible. I have lot's of Electric Boat and RV buddies. If so, I might get the Active Balancer method.
 
Maybe your power supply works differently than mine. But it shows the cells are already at 3.65 volts. Seems like it's already turn to stop.
 
400bird said:
Maybe your power supply works differently than mine. But it shows the cells are already at 3.65 volts. Seems like it's already turn to stop.
Click to expand...
Usually, power supplies are set to a specific voltage, and they output that voltage constant.
The bank is charged when the amperage drops to under 1 amp.
 
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