First time build - 280Ah “it’s alive!”

[Deleted member 23531]

Am I on the right track here?

Yes, you are on the right track. Basically it is still charging: your batteries are "holding" the voltage down from 3.55V to 3.3V because the battery is still charging. It will eventually reach 3.55V and the current will drop to close to zero. Just wait and monitor voltages with your voltmeter.

 

[DerpsyDoodler]

https://www.amazon.com/Variable-Adjustable-Regulated-Switching-Alligator/dp/B082FV1PGP/ref=sr_1_15?dchild=1&keywords=Roll%2Bover%2Bimage%2Bto%2Bzoom%2Bin%2BNice-Power%2BBench%2BPower%2BSupply%2B(0-30V%2C%2B0-10A)%2BAdjustable%2BDC%2BPower%2BSupply%2BKit%2B4-Digital%2BLCD%2Bfor%2BLab%2BPower%2BSupplies%2C%2BProduction%2BLine%2BTest%26Maintenance%2C%2Betc.%2Bwith%2BBanana%2BPlug%2BTest%2BLeads%2FWhite&qid=1614885084&sr=8-15&th=1

i got the 30v/10A version.

That’s probably as good a choice of any of the cheapys. Mine’s a cheapy as well. It gets a lot of air flow and has good cooling. I posted pics in my thread here.

 

[Corbury]

That’s probably as good a choice of any of the cheapys. Mine’s a cheapy as well. It gets a lot of air flow and has good cooling. I posted pics in my thread here.

My current PS doesn’t have a fan!

 

[DerpsyDoodler]

My current PS doesn’t have a fan!

Looks like it’s got a fan to me... ?

 

[Corbury]

Looks like it’s got a fan to me... ?

Now it does!

 

[Corbury]

ok new PS - MUCH better! the old one was not pushing many watts and taking forever. this one is working!

NOTE the CV display and it's set to 3.6v right now. Set it - then connect it - then don't change the settings. I think I got it. hopefully no blown-up batteries.

C

 

[Corbury]

ok - so maybe I have a problem?

I have been trying to top balance for the last couple of days. Pausing when away from the house or asleep - since I wanted to monitor this closely. But I am not seeing these cells budge from 3.374V. I know this could take approx. 17 hours - but I have had them going for at least 5-7 cumulative hours and it's not really moving.

I cleaned the cell connections - sanded with 220 and wiped everything down with rubbing alcohol. Are my aluminum bus bars a problem?

any thoughts here? BTW - thanks for all the help.

clyde

 

[DerpsyDoodler]

ok - so maybe I have a problem?

I have been trying to top balance for the last couple of days. Pausing when away from the house or asleep - since I wanted to monitor this closely. But I am not seeing these cells budge from 3.374V. I know this could take approx. 17 hours - but I have had them going for at least 5-7 cumulative hours and it's not really moving.

I cleaned the cell connections - sanded with 220 and wiped everything down with rubbing alcohol. Are my aluminum bus bars a problem?

any thoughts here? BTW - thanks for all the help.

clyde

Are they warm to the touch? Charging in parallel is going to take double, triple, quadruple...n the time coinciding with however many cells u have in parallel.

 

[Hedges]

Is that a 10A supply?
Showing 9.366A, can't run much faster than that, so it is charging as fast as it can.
About 2.35A/cell or < 0.01C; starting from completely empty we would expect 100 hours, 4 days without stopping for nights.
Where did your 17 hours figure come from? Starting at 82% SoC?

You show 3.374V (after resting some unspecified period of time).
I think that is a relatively low state of charge (from a random charge curve image), but I don't have the exact curve for your cells.

I thought you already did an initial charge of the batteries in series with a BMS. That would have been 4x faster since each cell gets full current of supply. But maybe that was a different supply?

What voltage is at the supply terminals (while it shows 3.6V)? What voltage at each cell?
You have good wires already, so probably not too much drop.
Since supply is already at CV operation and current is tapering off, I figure you may get more impatient later.

 

[Corbury]

Are they warm to the touch? Charging in parallel is going to take double, triple, quadruple...n the time coinciding with however many cells u have in parallel.

no - they seem fine - not warm. Maybe they did not get as charged in series as I thought they did. Nonetheless - they seem to be charging now. I'm going to leave them charging all day and report back.

 

[Corbury]

Is that a 10A supply?
Showing 9.366A, can't run much faster than that, so it is charging as fast as it can.
About 2.35A/cell or < 0.01C; starting from completely empty we would expect 100 hours, 4 days without stopping for nights.
Where did your 17 hours figure come from? Starting at 82% SoC?

You show 3.374V (after resting some unspecified period of time).
I think that is a relatively low state of charge (from a random charge curve image), but I don't have the exact curve for your cells.

I thought you already did an initial charge of the batteries in series with a BMS. That would have been 4x faster since each cell gets full current of supply. But maybe that was a different supply?

What voltage is at the supply terminals (while it shows 3.6V)? What voltage at each cell?
You have good wires already, so probably not too much drop.
Since supply is already at CV operation and current is tapering off, I figure you may get more impatient later.

ok - so they seem to be charging now - one measurement at the terminals is showing 3.4V now - which is up from 3.37 just about 2 hours ago. I realize that the trend is going to slow as it approaches 3.6v. I will just keep at it. Thanks! C

 

[DerpsyDoodler]

no - they seem fine - not warm. Maybe they did not get as charged in series as I thought they did. Nonetheless - they seem to be charging now. I'm going to leave them charging all day and report back.

I meant the bus bars.

 

[DerpsyDoodler]

ok - so they seem to be charging now - one measurement at the terminals is showing 3.4V now - which is up from 3.37 just about 2 hours ago. I realize that the trend is going to slow as it approaches 3.6v. I will just keep at it. Thanks! C

The amps will start tapering off but the speed at which the voltage climbs increases rapidly to completion, after 3.4v.

 

[Deleted member 23531]

But I am not seeing these cells budge from 3.374V

Doesn't your power supply show 3.60V in your photo? Are you saying the cells themselves measure 3.374V? The W = V*I calculation on your power supply suggests the voltage and current it shows are the actual voltage and current (and not some setpoint), since they multiply correctly to give the instantaneous watts, 33.71W.

If your cells do in fact measure 3.374V and your power supply measures 3.60V (as measured with the same voltmeter) then that indicates there is (3.600V - 3.374V)/9.366A = 24mOhm of resistance getting to your batteries. This is plausible; it would be hard to measure such a low resistance with a cheap multimeter though.

The fact that you're still dumping ~34W into your batteries shows that they haven't finished charging yet. Otherwise, where would the energy be going?! Please be patient.

 

[Triumphrider74]

Patience is key for sure, but you are getting to 3.4V barrier! The charge curve is nearly flat until you hit 3.4 then things will progress quickly from there. The finish line is in view! ?

 

[Deleted member 23531]

Also, your power supply shows it is now in "CV" or constant-voltage mode. This is further evidence you are nearly done! Basically it means that the cell voltage plus the IR drop on the wires has exceeded your 3.60V voltage compliance setpoint, so rather than the power supply limiting the current it is now limiting the voltage. Up until now you were probably in "CC" or constant-current mode.

 

[trevor.the.van]

Trust the process! It takes time. I just top balanced a new set of 100Ah, after charging up a good deal. Still took 12 hours of patience.

On a separate note, after finishing my top balance, I capacity tested and got a nice 1320Wh out of my 100Ah rated cells. Always good to get what you pay for

 

[Corbury]

Thank you everyone!!! It worked!!!! I got to 3.61v - (was a little worried about going to 3.65v). The voltage really does move superfast once you get to 3.4v. Wow. working on the second set of batteries now. Just completing the initial charge.

 

[Corbury]

Update!

I top balanced both banks. Then waited a few weeks for build. Here is the test assembly. Went with 1/2” baltic birch and dominos. (For final - i will glue 3 sides and screw 4th side with small grk’s). Bolt the whole thing down with 1/8 aluminum angle to 80/20 - which is bolted to van.

I put 1/8” high durometer rubber strips all sides + bottom and in-between each cell.

Using 120a overkill solar bms.

Tested with one battery and samlex 2212 evo:
1. Heat gun - 1300w totally fine
2. Nespresso - 1450w - intermittent - fine
3. Electric space heater - low - 750w - no problem - 3 hrs? Lost track.
4. Electric space heater - high - 1570w and 150a +/- ... ran around 10 seconds - BMS shut over current shutdown - makes sense - it’s a 120a BMS.

So question is:
1. when i hook up second battery in parallel - can i run the heater at 1500w + ... because each BMS is splitting the load?
2. Does anyone know what is correct charge profile for samlex evo? I provisionally chose option 3 - 2 stage - no float.

we will see.

thoughts?

 

[time2roll]

Yes the two BMS/batteries in parallel will share the load.
I would tend to let the charging go to float so that if unattended you will not be holding the battery at max voltage for an extended period.

Great news on that 150 amps for 10 seconds. I need about 3 seconds to start a half HP pump.