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diy solar

Help!!! Smoke during top balancing

Should the negative lead not be at the other end of the parallel string on the negative terminal?

I was always "taught" you have positive and negative at opposite ends so you don't "fill one glass first"
 
Did the charger smoke, or the crappy included wires?

First replace the wires. The ones who come with these cheap power supplies are total junk. You won't be the first one having very low amps and hot/melting cables.

Get some proper cables.
I also recommend connecting the wires 'cross wired', the positive to the left top terminal and the negative to the bottom right terminal (with the screw). This compensates for voltage drop between the busbars, otherwise the most right cell will have (very minimal) lower voltage compared to the left cell since the busbars and connections add some voltage drop, just as @jwelter99 mentioned.

As for the reversed polarity: This might have damaged the charger. You might have been lucky also, if it was only a diode on the output which now is toast, it doesn't mean the supply is toast. Just check with a multimeter and a car bulb to see if its still working.

Please note: 5A for topbalancing 4x280Ah is going to take forever.
Assuming the cells are at 50% SOC when arrived you need to top-up about 600Ah. With only 5A this will take at least 120 hours (5 days)
Not sure if those cheap chargers like to run at max load continously for so long, you might need to go down to 4A (adding even more time to finish)

I'd suggest getting a charger with some more amps, or serie-wire them with a BMS set to 3.65V HVD and charge with a regular charger till the first cell hits HVD, rewire to parallel and finish topbalance. In that case you only need to top-balance from 99% to 100% SOC or so, since all cells are full, or near full.
Charging with 20A in series, and 50% SOC upon arrival requires you to put 120Ah in, thus taking approx 6 hours. Add 2-3 hours (depending on the cell drift) to finish topbalancing and you're good to go.

I personally don't like topbalancing unattended. So 5 days of continously charging equals to a few weeks if you don't want to leave it charging overnight
 
Oh by the way ...
Even if you fried this power supply by connecting the battery backwards,
There is a possibility you will fry your new supply by connecting it correctly.
A power supply is intended to supply power, and when turned off might drain the capacitors of whatever is connected.
When you connect a battery to power supply that is either off or set for a low voltage, it may short out the battery. That has been know to fry supplies.
Some supplies have a recommendation to use a diode to prevent reverse current flow if charging batteries. That causes a variable voltage drop depending on current (nominally 0.7V to 1.1V) which with higher end supplies is addressed by remote current sense (something you don't have with a cheap supply).
Some people here got specialized battery tester/chargers.


This note from Keysight says to have diode protect remote sense terminal as well (see diagram). Which means battery sees 0.7V less than set voltage. I would do something like series resistor to limit current into remote sense so it could see battery voltage, maybe an additional diode pulling remote sense down to no more than 0.7V above positive terminal.

 
81213D6B-7DE0-45AC-BD78-BFC79976A833.jpegguys thanks for all the info , I got another power supply but Im having another issue. I can’t seem to verify the output of the new charger. I put the tips of my multimeter inside these holes and I’m getting nothing.
 
I used the same method to check the one I thought was broken yesterday and that also showed zero, if I’m testing the new one the same way and also getting zero then it’s possible the one from yesterday isn’t broken , or I’m doing something wrong which is even more likely


I’m assuming the output button is supposed to verify this for me?
 
View attachment 38822guys thanks for all the info , I got another power supply but Im having another issue. I can’t seem to verify the output of the new charger. I put the tips of my multimeter inside these holes and I’m getting nothing.
Hard to figure out from the picture, but you must touch the metal from your Voltmeter probe to the metal of the output terminal. Try unscrewing the plastic cover on the banana jack terminals of the power supply, then touch the uncovered metal with the metal part of your Voltmeter probes. I made 10 gauge wire with terminal rings and spade lugs to connect mine. I would have used ring connectors on both ends, but the insulator covers on my banana jacks don't come off.
 
Don't get me wrong, but for $10 more you could have gotten a 10 amp supply. Double the current during top balancing is worth it to me.

I may be able to plug the other one in on the other side but I am trying to verify output
 

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It appears there are LED indicators for "CV", "CC", "output"
In your picture, only "CV" has LED on.
In Amazon picture, both "CV" and "output" have LED on.
Try pressing the black button labeled "output" again.
 
Since you have no load connected, the Amp meter should show 0A, it shows 4.80A in your picture so that is not right.

Perhaps because the "output" light is off, display shows setting.
When "output" button is pressed, it might turn on the "output" light and display measurement.

However, I don't find that in the manual; it describes shorting output to set current.


It does have additional features such as locking adjustments; I think that will help prevent accidently changing them by bumping knobs.
 
Yes thank you. The one from yesterday works now I got them both attached , cells went up from 3.29 to 3.31
 

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! 3.75V as displayed on meter is probably higher than you want !

For now, voltage at battery is lower and the higher voltage forces more current through the skinny wires. But as battery charges up, that will over-charge cells.
Power supply CV setting should be something like 3.65V, whatever your target is.
Faster charging should be achieved with heavier wires, so less voltage drop across them.
 
! 3.75V as displayed on meter is probably higher than you want !

For now, voltage at battery is lower and the higher voltage forces more current through the skinny wires. But as battery charges up, that will over-charge cells.
Power supply CV setting should be something like 3.65V, whatever your target is.
Faster charging should be achieved with heavier wires, so less voltage drop across them.


Ok thanks, question is it normal that the two cells on the edges are already up to 3.44 but the ones in the middle are still 3.29-3.30
 
I also recommend connecting the wires 'cross wired', the positive to the left top terminal and the negative to the bottom right terminal (with the screw). This compensates for voltage drop between the busbars, otherwise the most right cell will have (very minimal) lower voltage compared to the left cell since the busbars and connections add some voltage drop, just as @jwelter99 mentioned.


I cross wired as you recommended and It turns out the one from yesterday works too. I have both set to 3.65 volts and crosswired both sides

So one charger is crosswired and the other charger is crosswired , is that ok?
 
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