Really this long to top balance?

[PowerMan]

I have my (4) 304Ah cells connected in parallel and connected to a 10A bench power supply. BMS is not connected at this time. Initial voltage was 3.29 on all 4.

I set to the power supply to 3.65V and 9A. I didn't want to max out the supply.

It's been on the charger for over a week now and the current is at 1.56A. I've read that it does take a while doing it this way, but 8 or 9 days and still not there. I'm not in a hurry, just want to make sure I'm not doing something wrong or if there is something different I should be doing.

 

[sunshine_eggo]

4 * 304Ah = 1216Ah.

Assume AT LEAST 50% of that needs to be input.

604Ah

BMS CAN'T be connected when cells are in parallel. Do not attempt to do so.

604Ah/1.56A = 387 hours = 16 days.

Did you follow the guide and fabricate new leads, or are you using the junk leads that came with the supply?

 

[PowerMan]

I have a question on your math. You state: 604Ah/1.56A = 387 hours = 16 days.
But I initially set the power supply to 9A so shouldn't that be 604Ah/9A = 67 hours = about 3 days

For clarity, with the battery connected, the power supply has been counting down the amps and is currently at 1.56.

I didn't make my own cables but did purchase different ones.

 

[chrisski]

My Math shows 3 days if the current was at 9 amps for nearly all those. If yours was at 9 amps and is now at 1.56 amps, you’re nearly done. Of course it is possible the cells were at a much lower State of Charge than 50%.

If the current was at 1.56 amps the whole time, that’s a problem.

I used 10 AWG wire for my charging leads. That helped tremendously And allowed full rated amperage with no heat. I can’t remember what the original leads were. I think less than 6 amps.

 

[time2roll]

Did the amps start at nine? or 1.56?

What is the voltage now?

 

[brb58]

If your current is only at 1.56A, your leads have voltage drop. You will need 10awg leads. Make sure you set the voltage of your supply with the leads disconnected from the battery bank and then connect them. Measure the voltage at the ooutput of the supply and then at the battery...you should have VERY LITTLE difference.

 

[Zwy]

I have a question on your math. You state: 604Ah/1.56A = 387 hours = 16 days.
But I initially set the power supply to 9A so shouldn't that be 604Ah/9A = 67 hours = about 3 days

For clarity, with the battery connected, the power supply has been counting down the amps and is currently at 1.56.

I didn't make my own cables but did purchase different ones.

10 ga minimum, I'll even run a pair of 10 ga. Use ring terminals on the battery, the clips cause resistance as only a tiny portion contacts the stud/busbar.

 

[PowerMan]

10 ga minimum, I'll even run a pair of 10 ga. Use ring terminals on the battery, the clips cause resistance as only a tiny portion contacts the stud/busbar.

Thanks for that suggestion. I think I'll put together some cables with rings and see how it goes.

 

[sunshine_eggo]

I have a question on your math. You state: 604Ah/1.56A = 387 hours = 16 days.
But I initially set the power supply to 9A so shouldn't that be 604Ah/9A = 67 hours = about 3 days

For clarity, with the battery connected, the power supply has been counting down the amps and is currently at 1.56.

I didn't make my own cables but did purchase different ones.

I used the data given and the assumption that many people use poor quality leads with excessive voltage drop resulting in the low currents you describe.

You indicated the PS was set to 9A, but that you're only getting 1.56A.

 

[sunshine_eggo]

Thanks for that suggestion. I think I'll put together some cables with rings and see how it goes.

The guide details fabricating your own leads.

If you're not following the guide, you should.

You need to monitor voltage AT the cell, not the power supply.

 

[S Davis]

I have done 4-280ah packs and they all took between 72 and 78 hours each with new 6ga wire leads. I figured they arrived at about 40%soc. Sounds like a problem with your leads like stated above.

I would redo the leads and verify the voltage with the power supply disconnected, reconnect and finish charging. It sound like you are almost there. Are you checking the voltage with a separate meter or going by the power supply read out?

 

[bryn]

I just did a new set of 8 x 304 cells last month, it does take a long time.

I made up larger cabling before i started, its is worth doing, you still might not see a full 9amps going into the batteries, i now i didn't but i had my on CV as the other charger i had could only do CV

 

[brb58]

I did some 280AH EVEs recently. I went out on eBay and bought a 30A HP used bench charger to make them charge faster. With it, as well as my 10A charger, I had no problem having them output full current during CC moode.

 

[PowerMan]

I have done 4-280ah packs and they all took between 72 and 78 hours each with new 6ga wire leads. I figured they arrived at about 40%soc. Sounds like a problem with your leads like stated above.

I would redo the leads and verify the voltage with the power supply disconnected, reconnect and finish charging. It sound like you are almost there. Are you checking the voltage with a separate meter or going by the power supply read out?

I am checking the battery voltage with my multimeter and have new 10 AWG cable arriving tomorrow to make new leads. This morning the battery was at 3.35V.

 

[sunshine_eggo]

If your cells measure 3.35V, the power supply reads 3.65V and you're only flowing 1.56A, your connections are bad, or the leads are junk.

 

[Bud Martin]

Can we see the pictures of your setup?
Are you connecting the power supply leads to the batteries in the cross fashion?

 

[Owls Nest]

Yes it takes awhile, I am doing it also and just get the new leads and be patience. Just finished my first bank 12.8v 3days. 304amphour. working on the second bank now.

 

[PowerMan]

I was out of town for a couple days and just connected the power supply to the battery with my newly made 10 AWG cables. We'll see how it goes.

One thing I found odd-- I dial in the voltage to 3.65 with the output switched off on the power supply and when I turn on the output the display switches to 3.5. This is with the battery connected.
My power supply is Hanmatek HM310.

Battery voltage reads 3.35 on my multimeter so even if it gets to 3.5 it will be progress.

 

[sunshine_eggo]

I was out of town for a couple days and just connected the power supply to the battery with my newly made 10 AWG cables. We'll see how it goes.

One thing I found odd-- I dial in the voltage to 3.65 with the output switched off on the power supply and when I turn on the output the display switches to 3.5. This is with the battery connected.
My power supply is Hanmatek HM310.

Battery voltage reads 3.35 on my multimeter so even if it gets to 3.5 it will be progress.

3.65 is the MAX SET voltage. 3.50V is the actual voltage the power supply is delivering because you can't force the battery to be at a higher voltage than the state of charge and flow of current permit.

Unfortunately, you still have 0.15V drop, which isn't great. The good news is that the drop will stay about constant for the current, so when the PS reads 3.65V, the cells will be at 3.5V, and they should fill quickly at that point.

 

[time2roll]

How many amps are moving?