BMS dropping Volt?

[Techaplayer]

Hi all, I’m struggling with something I’m hoping someone else has also had and resolved??

My BMS is not showing the full voltage of 26.4, and only 13.7?

Multimeter A (negative) and B (positive) directly on the batteries shows 26.4V so the series connection is good.

The white plug at C, if I unplug and use the multimeter and check the black and then each red wire in sequence I get 3.3, 6.6, 9.9 etc. right up to 26.4V on the last red wire so battery connections are good.

Once connected D (negative), and B (positive), these go to the charge controller, I only get 13.7V. I tried another identical BMS, both band new, and get the same result so I don’t think there is an issue with the BMS? My charge controller is also showing battery at 13.7V as its running through the BMS, and LED is on float which if not mistaken is trickle charge meaning the bank is fully charged.

Has anyone else had this issue? Any advice is seriously appreciated! I’m doing my head in. Thanks.

 

[sunshine_eggo]

Hi all, I’m struggling with something I’m hoping someone else has also had and resolved??

My BMS is not showing the full voltage of 26.4, and only 13.7?

Multimeter A (negative) and B (positive) directly on the batteries shows 26.4V so the series connection is good.

The white plug at C, if I unplug and use the multimeter and check the black and then each red wire in sequence I get 3.3, 6.6, 9.9 etc. right up to 26.4V on the last red wire so battery connections are good.

Once connected D (negative), and B (positive), these go to the charge controller, I only get 13.7V. I tried another identical BMS, both band new, and get the same result so I don’t think there is an issue with the BMS? My charge controller is also showing battery at 13.7V as its running through the BMS, and LED is on float which if not mistaken is trickle charge meaning the bank is fully charged.

Has anyone else had this issue? Any advice is seriously appreciated! I’m doing my head in. Thanks.

Is there an inverter in the circuit? If so, the surge to charge the capacitors may cause the BMS to engage short circuit protection.

 

[MisterSandals]

these go to the charge controller, I only get 13.7V.

What charge controller?

My charge controller is also showing battery at 13.7V

Have you measure the voltage from B to D with a meter?

Is your charge controller set to 12V battery?
Is it a solar charge controller and was the battery connected BEFORE the array?

 

[Techaplayer]

Is there an inverter in the circuit? If so, the surge to charge the capacitors may cause the BMS to engage short circuit protection.

Nope. Figured I'd connect the inverter when I know charging is sorted.

 

[Techaplayer]

What charge controller?

Have you measure the voltage from B to D with a meter?

Is your charge controller set to 12V battery?
Is it a solar charge controller and was the battery connected BEFORE the array?

It’s a Victron Bluesolar MPPT 150/35, and set to 24V.

B to D yes, is 13.7V

The weird thing is if I ignore the solar charger so I’m just measuring the positive on the battery bank, and the black negative cable coming out of the BMS I should get a reading of 26.4V. It’s reading 13.7. If I unplug the balancing cables from the BMS so the only thing connected to the bank is the blue cable to the negative and check again the positive on the bank and the black negative BMS cable I still get a reading of 13.7V? So the balancing cables are not having any effect at all plugged in. I’ll have to try another harness, if that doesn’t fix this then both BMS units are defunct?

Not sure what you mean by battery connected before the array? Thanks for you help!

 

[400bird]

Does that BMS have communication? Bluetooth?
It sounds like the BMS is in a fault state that needs to be corrected. Or maybe the BMS needs to be woken up. I'd recommend checking for alarms on the BMS and then search here how to wake up that BMS.

Not sure what you mean by battery connected before the array?

When making electrical connections, most charge controllers recommend connecting battery voltage before PV/solar power.

 

[sunshine_eggo]

Have you shorted B- to P-?

IIRC, the DALY needs to be "woken up" via that method.

 

[Techaplayer]

Have you shorted B- to P-?

IIRC, the DALY needs to be "woken up" via that method.

Heya, so I finally got a bluetooth module. I undid everything and rewired again in case I did something wrong. I get the same result. Here is the Bluetooth app results. I've just messaged the Chinese seller hoping they can shed some light but once the sale is done, and this was a while ago, they tend to not get back to you. Nothing has frustrated me this much.

 

[Techaplayer]

Heya, so I finally got a bluetooth module. I undid everything and rewired again in case I did something wrong. I get the same result. Here is the Bluetooth app results. I've just messaged the Chinese seller hoping they can shed some light but once the sale is done, and this was a while ago, they tend to not get back to you. Nothing has frustrated me this much.

Have you shorted B- to P-?

IIRC, the DALY needs to be "woken up" via that method.

O'wait, you saying short B to P? Is that not dangerous?

 

[Solar Guppy]

Your image shows the discharge MOS is off, which I assume means it won't allow discharge of the battery, try turning that on.

Also it seems balancing is turn off as well.

 

[mikefitz]

Just to add to your problems, cell 3 indicates a much lower voltage than the others.

 

[Techaplayer]

Your image shows the discharge MOS is off, which I assume means it won't allow discharge of the battery, try turning that on.

Also it seems balancing is turn off as well.

Thanks! Daly in China said the same thing switching on discharge MOS. I'm all over the place trying to solve this. I can't tap that, nothing happens with any of those little icons at the top tapping them so must be somewhere else in the app to activate this? When I go to the active balance tab the button to switch the balance on is greyed out? There is no power coming in from the solar panels via the charge controller, or power going out via the inverter as I have not switched them on until I can get the correct readings from the BMS. Thanks again for your time replying here, appreciated!

 

[Techaplayer]

Just to add to your problems, cell 3 indicates a much lower voltage than the others.

Tell me about it. I originally got 16 batteries, plan was 2x 8 sets in parallel. One of the batteries was damaged in transit so that messed up one 24V bank so broke that down to a 12V with a couple spares and used it elsewhere. I charged this full bank with a smart battery charger until all 8 were full, then connected them up. When first checking BMS battery 3 was 3.7V! WAY too high so figured it might also be damaged so swapped it out with one of the spares which wasn't charged in the originally set so could be why. But yeah will keep my eye on that one. Thanks!