October 24, 20205 yr Voltage reading should about 57.98v so something is a miss with a reading of 52.5v. If you take a voltage reading directly off the battery one should see an appropriate reading of 57.9v or so, if so the BMS must be faulty not to give a full reading on the discharge side. Edited October 24, 20205 yr by Nealh
October 24, 20205 yr You're missing 5.5v! You need to find out where it is. Measure the cell-pack voltage directly between where the thick red and thick black wires are attached, then from where the thick black attaches to the cell-pack to the positive output terminal, then keeping your red probe on the positive output terminal, move your black probe to where the thick black wire from the cell pack attaches to the BMS, then where it leaves the bms, then the output terminal. One of those five measurements will tell you where the voltgae has gone.
October 24, 20205 yr Author Voltage reading should about 57.98v so something is a miss with a reading of 52.5v. If you take a voltage reading directly of the battery one should see an appropriate reading of 57.9v or so, if so the BMS must be faulty not to give a full reading on the discharge side. You're missing 5.5v! You need to find out where it is. Measure the cell-pack voltage directly between where the thick red and thick black wires are attached, then from where the thick black attaches to the cell-pack to the positive output terminal, then keeping your red probe on the positive output terminal, move your black probe to where the thick black wire from the cell pack attaches to the BMS, then where it leaves the bms, then the output terminal. One of those five measurements will tell you where the voltgae has gone. Thanks so much guys it must be a faulty BMS. I'm getting 58.3 volts when bypassing the BMS. I'll order a new one and I appreciate all the help from you all.
October 24, 20205 yr Thanks so much guys it must be a faulty BMS. I'm getting 58.3 volts when bypassing the BMS. I'll order a new one and I appreciate all the help from you all. Don't buy anything until you find where the voltage drops. Do the tests I said. There's no fault in a BMS that can cause a voltage drop. It's a bank of four switches that work in parallel, plus one for the charge control. The switches can only be on or off. Even if one was faulty, the volts would still go through the others. The only thing the complicated electronics does is turn the switches on or off, depending on the charge state of the cells and the amount of current flowing. Edited October 24, 20205 yr by vfr400
October 24, 20205 yr Author I have removed the BMS. Is there a specific BMS I need does it have to be 52v 26ah like my battery.
October 24, 20205 yr Author Don't buy anything until you find where the voltage drops. Do the tests I said. Oops I already removed the BMS
October 24, 20205 yr Author Read my post above again. I added to it. I see, do I need to solder BMS back on to carry out the tests? I had trouble following your instructions sorry. EDIT: i keep reading your instructions and i think i get it now. i dont have any thick black wires from the cell pack i have 2 thick black wires that attach straight to the bms from my output connectors. i have a thin black wire that comes from that white connecting block that also goes to the cell pack. Is that what im after? Thanks Edited October 24, 20205 yr by Paulpmpmpm
October 24, 20205 yr The wire that was attached to the pad marked B- is the negative wire that's attached to the cell-pack at the other end.
October 24, 20205 yr I've had weird values out of a BMS before when there was a poor connection between one of the sense wires and the BMS. When the pack was squeezed, the output voltage from the BMS read anything from 4V or so to the full battery voltage. Make sure your sense wire connections to the BMS are good.
October 25, 20205 yr Author The wire that was attached to the pad marked B- is the negative wire that's attached to the cell-pack at the other end. 7 tests to do. this shows the probe positions: [ATTACH type=full" alt="38942]38942[/ATTACH] Thanks for replying. I test from the thick black wire that attaches to the cell pack to the positive output and only get 52v its losing the volts through the bms somewhere im sure im just going to order a new one and replace it then check it again.
October 25, 20205 yr Thanks for replying. I test from the thick black wire that attaches to the cell pack to the positive output and only get 52v its losing the volts through the bms somewhere im sure im just going to order a new one and replace it then check it again. Do all 7 tests.
November 19, 20205 yr Author 7 tests to do. this shows the probe positions: [ATTACH type=full" alt="38942]38942[/ATTACH] Hey I fitted a new BMS and still have same problem so I will do the 7 tests as you originally told me to. I was reluctant at first because I really don't understand what I'm looking at with that diagram. I really don't want to bother you but is there any simpler way I can understand? Am I supposed to hold 1 prong at 1a and the other at the other 1a, then 2a and 2a ogether ? Etc.
November 23, 20205 yr Author Here are some pictures. Positive end : Negative end : Output : Output 2 : https://i.ibb.co/FbQH71Q/IMG-20201123-162215.jpg
November 23, 20205 yr Am I supposed to hold 1 prong at 1a and the other at the other 1a, then 2a and 2a ogether ? Etc. Yes.
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