How to force max amps from the power supply?

[mrmoon]

Hello. I have this power supply 0-30v, 0-10A:



Say I wanna charge my 8 100Ah cells in parralel at 3.65V. I put 3.65v on PSU, crank amperage to max and start charging.

1. Voltage on PSU display stays the same, as configured 3.65V. PSU remains in a CV mode.
2. The actual voltage output from PSU is lower, say approx. 3.45V. (measured with multimeter at PSU output connectors)
3. The voltage at cell pins is 3.3V.
4. The charging current is about 3A.

How do I charge at 3.65v max but 10A current? Should I increase the voltage on PSU while keeping the actual voltage output under loads under 3.65v?

Thank you

 

[Tulex]

I had the same issue. A member on here said to make heavy leads (they suggested 10 awg, I had 12 available) with eye connectors. I did that and it then charged at CC. At this point, Amps will stay at setting, volts will be below until it gets to setting, at which time volts will stay at setting and amps will drop.

 

[Robbert]

That indeed is the only way to do it.
Even with thicker leads and good ring lugs the amperage will temper a bit as the voltage of the cells rises.

 

[mrmoon]

I have just disassembled PSU and attached 10 awg cables to the outlets. It went to 7A. However, how can I get 10A?

 

[mrmoon]

Or it's all about resistance? Even if I use 4AWG cables it won't do much right? How do the smart chargers output constant current then?

 

[Robbert]

I have just disassembled PSU and attached 10 awg cables to the outlets. It went to 7A. However, how can I get 10A?

It has to do with resistance and the voltage difference. You will get an higher amperage if the voltage of the cells is a bit lower, or the settings in the power supply slightly higher. The latter, you should be very carfull with in order to avoid an overvoltage of your cells (i would not do that). 7 amps is not a lot, but you will get there.

 

[hicke]

Connect the plus and minus wires when the power supply is turned off. Then turn it on and increase the Amps using the knob. Then turn it off and disconnect the wires.

 

[RCinFLA]

Cheap CV/CC power supplies start to taper current a little before they hit CV limit. There is also internal wire connections and banana jacks that have a little voltage drop under heavy current load.

Most common user issue is insufficient cable gauge to battery creating voltage drop across cabling to battery. For 10 amps you need at least 8 gauge cables and keep them as short as possible to avoid too much voltage drop.

Throw out the cheap 16-18 gauge cables that came with the power supply.

With separate DVM check the voltage drop across the cable length under load current.

Do not crank up the 3.65v CV voltage limit to make up cable loss. As cell becomes fully charged, the voltage will rise to the higher CV setting. Don't think you can get away with doing this by watching cell voltage and lowering CV setting as battery gets fully charged. Cell voltage rises quickly when it gets near full charge. Good way to create bloated cells.

 

[Skypower]

Some bench top power supplies simply aren’t up to it. They fold back on current way too soon regardless of cable. How do you know? Experience or having a good one to compare it to. If I remember correctly they should still be charging hard until they are 200mv from set voltage.(someone correct me). I’ve returned a few back to Amazon. But like RC said don’t crank up the voltage past the pre set just to make the current. When it happens, it happens fast. The moment you walk away, you have a set of expensive bloated door stops.

 

[efficientPV]

In high current lab pls thy have separate sense wires at th lod s voltage drop of wires doesn't matter. If you went to the effort of soldering wies directly, might as well find the sense resistor and bring that to the end of the positive lead and eliminate half the voltage drop. Be sure to add a 100 ohm resistor back to the original sense point so the supply doesn't go crazy if the sense wire gets connected.

Now you know why Xantrex gets several thousand for a supply and Amazon gets $60.