can't increase current when charging (boost inverter)

Thach2264

1 µW
Joined
Jan 27, 2020
Messages
4
Hello all-

I have a HP 1200W Power Supply Server that modded to have an output of 12.5V @ 900w max. Connected to my 1800w Boost converter with an input 40A max / output of 20A max. Then through a voltage /current 100A monitor to monitor it.

My current setup is using it to charge a 4S 120A lipo @ 16.8V, but max output current can only go to 8.5A max. Not sure if it's the PS or the boost converter. Max output is around 140W max, I tested with 3S and get around 140W as well.

thanks,

HP PS
https://www.ebay.com/itm/498152-001-HP-1200W-POWER-SUPPLY/283753055475?hash=item42110004f3:g:kpsAAOSwy2Bd8~0e

boost inverter
https://www.amazon.com/KNACRO-Converter-Step-up-In10-60V-Electric/dp/B077Q852DJ/ref=asc_df_B077Q852DJ/?tag=hyprod-20&linkCode=df0&hvadid=242045434535&hvpos=1o4&hvnetw=g&hvrand=16237320597620802880&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9031337&hvtargid=aud-799727667774:pla-417336700268&psc=1

Current Monitor
https://www.amazon.com/ILS-Voltage-Current-Battery-Monitor/dp/B07ZNYLZDD/ref=sr_1_15?keywords=100a+current+monitor&qid=1580154377&s=electronics&sr=1-15
 
Pc power supplies don't like it if the 5V and 3V3 rails aren't loaded.
They also usually deliver more current on that 5V and 3V3 volt rail.
Some ATX supplies don't even start up if they aren't properly loaded. Maybe those server supplies are different?
 
Cheap Chinese ratings are "optimistic" ?

Getting any heat ?

Try a fan or bigger heat sink?

A proper charger would be better
 
I can think of a couple possible things. Some may be teaching you to suck eggs, but you haven't ruled them out, so they are worth mentioning:

1. The "Constant Current" screw on the boost converter is set too low.

2. The PSU has multiple 12v rails and you're only using one.

3. Your battery internal resistance is high, or your connectors are also high resistance.

4. Your current meter is calibrated for the wrong shunt type. If it defaulted to a 50A shunt when you had a 100A shunt installed, it would be reporting half the actual current.
 
1. I did turn the current pot all the way
2. I'm using the two fattest ones about 1" long each
3. all batteries are around 0.9m Ohm and using 12/10awg cables
4. Could be....hmmmm

boost converter coil is a little more than warm and fan cooling the FET auto turn on/off when needed, charging cable is barely warm.


**************
THANKS Sunder!!!
Just check my current monitor****IT WAS SET TO 50A!!!**** changed to 100A
 
Thach2264 said:
THANKS Sunder!!!
Just check my current monitor****IT WAS SET TO 50A!!!**** changed to 100A

It's always the simple things, isn't it? ;)

Glad I could help.
 
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