Has my BMS died?

Wooly

New Member
My system has been working fine for months then all of a sudden I'm only getting 10.5v output from my lifepo4 4s 310ah battery.

As you can see from the pics the battery is outputting 13.4v before the BMS but only 10.5ish after.

Is my Daly BMS dead or have I over looked something?

System is:
4s 310ah Lifepo4
Daly 300a BMS
ASBO 50a B2B & MPPT
480w bifacial mono PV

Running a motorhome with:
12v compressor fridge
Diesel stove and heater
12 led lighting
12v sockets
3000w pure sine inverter (rarely used)
 

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FilterGuy

What, me worry?
Try disconnecting the balance harness and the connection to the battery and then reconnect. This will reboot the BMS. If it is still not working then the BMS probably died.
 

FilterGuy

What, me worry?
Try disconnecting the balance harness and the connection to the battery and then reconnect. This will reboot the BMS. If it is still not working then the BMS probably died.
BTW: Is it a 'smart' BMS? If so, what is the app saying the status is?
 

FilterGuy

What, me worry?
Unfortunately its not "smart"
I do not know about the newer Daly 'not smart' BMSs, but some of the older ones required a reset if they hit an error condition. Did your system see something unusual before it started acting up?
* A short circuit?
* A particularly low discharge or high charge on the battery?
* Do the cells all have similar voltages? (Sometimes they can look similar till they get near full charge, so similar voltages might not mean much, but dissimilar voltages are certainly a red flag)
 

Wooly

New Member
Try disconnecting the balance harness and the connection to the battery and then reconnect. This will reboot the BMS. If it is still not working then the BMS probably died.
So I disconnected the BMS and no change however when I test the voltage with the system negative disconnected the voltage jumps to 12.4v (which is still too low as the batt is at 13.4v) and drops back to 10.5v when I connect it again. (see pictures)

I've checked all the negative connections and all seem fine.

Im scratching my head at this one. 🤷‍♂️
 

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FilterGuy

What, me worry?
So I disconnected the BMS and no change however when I test the voltage with the system negative disconnected the voltage jumps to 12.4v (which is still too low as the batt is at 13.4v) and drops back to 10.5v when I connect it again. (see pictures)

I've checked all the negative connections and all seem fine.

Im scratching my head at this one. 🤷‍♂️
When you hook it all back up, does the BMS still not work?
 

Wooly

New Member
With it all back together still getting around 10.5v.

All cells are within 0.01v of each other (3.34v).

Im not aware of anything odd happening. I'm in the middle of a road trip across Europe. Just got off a ferry this morning a drove for 4hrs so the Abso should have been charging away from the vehicle battery and a little solar (late afternoon, overcast and raining). Was all working fine this morning prior to getting on the ferry.
 

FilterGuy

What, me worry?
Hmmmm..... it sure does not sound promising. My guess is the BMS was given up the ghost.

Since you already had the BMS, I did not want to bad-mouth it. However, since it looks like it died I will speak up.

A few years ago Daly was the go-to BMS for @Will Prowse and many other DIYers. However, a couple of years ago they re-did the product line and the forum has seen a lot of complaints on Daly BMSs since then. I would not recommend replacing it with another Daly.....but that is just one person's opinion. Right now, the JBD line of BMSs seems to be the favorite on the forum.

Sorry this happened on your road trip. That is a real bummer.
 

Wooly

New Member
Thanks for your help Filter guy.

Yeah really bad timing but at least the charge from the Abso is able to run everything while the engine is running or if I'm lucky and get a sunny enough day.

Yeah I'm getting that impression of the daly bms now. When I bought it just under a year ago they were still getting decent reviews and due to the high draw from the 3000w inverter (need to run power tools sometimes) I struggled to find a 4s 300a capable bms.

Daly will definitely be getting a complaint, not that I expect I'll get much back from them.

I'll have to have a look at the JBD ones and see if they do a 4s around 300a...
 

Pim57

Solar Enthusiast
If the temperature sensor is faulty, shorted or disconnected, it will shut down the bms.

With my smart Daly bms I need to disconnect the P- in order to reset a fault condition.
 

Mudd

Solar Enthusiast
Thanks for your help Filter guy.

Yeah really bad timing but at least the charge from the Abso is able to run everything while the engine is running or if I'm lucky and get a sunny enough day.

Yeah I'm getting that impression of the daly bms now. When I bought it just under a year ago they were still getting decent reviews and due to the high draw from the 3000w inverter (need to run power tools sometimes) I struggled to find a 4s 300a capable bms.

Daly will definitely be getting a complaint, not that I expect I'll get much back from them.

I'll have to have a look at the JBD ones and see if they do a 4s around 300a...
I'm curious to why you think you need such a high amperage BMS. I'm running just a 100 a BMS on a 8 cell 280ah set up. I realize my BMS may be a little under size but I can run my rooftop AC with no issues on a 3k inverter.
 

mikefitz

Solar Addict
I assume you have checked all connections to the cells and that the buss bars are secure.
If you turn down the charge voltages to 13.8 you can run the battery without a BMS, just keep a watch on the voltage and don't let it get below 12v. The Kisae controller you have allows user settings.

You may be able to get something from eBay de or Amazon de,

example,

Mike
 

Wooly

New Member
I'm curious to why you think you need such a high amperage BMS. I'm running just a 100 a BMS on a 8 cell 280ah set up. I realize my BMS may be a little under size but I can run my rooftop AC with no issues on a 3k inverter.
I run power tools off my inverter. I'll pull 250a with my table saw and shop vac extraction running off it.
 

FilterGuy

What, me worry?
I assume you have checked all connections to the cells and that the buss bars are secure.
This is a very good point. (I don't know why I didn't think of this sooner.... sorry) Since this is a mobile install, we have to consider the possibility of vibrations causing something to disconnect. If the BMS can't read one of the cells. It might think the cell is 0V and shut down.

Try unplugging the BMS harness and reading the voltages at each pin of the harness. Read the voltage between the most negative pin and each of the subsequent pins. Each one should read ~ 3.3V higher than the previous. ( You may need small nails or pins to stick into the connector to make the readings. Be very careful... If it shorts out it will probably fry the harness wire.)
 

Wooly

New Member
This is a very good point. (I don't know why I didn't think of this sooner.... sorry) Since this is a mobile install, we have to consider the possibility of vibrations causing something to disconnect. If the BMS can't read one of the cells. It might think the cell is 0V and shut down.

Try unplugging the BMS harness and reading the voltages at each pin of the harness. Read the voltage between the most negative pin and each of the subsequent pins. Each one should read ~ 3.3V higher than the previous. ( You may need small nails or pins to stick into the connector to make the readings. Be very careful... If it shorts out it will probably fry the harness wire.)
Good shout guys, not sure why I didn't think of checking that either though I did check all the busbars and connections yesterday.

Just tested the balance wires and voltages are all reading correct.

The BMS is also warm to touch. I've never noticed it to get warm before even when pulling 200a+ out of it and the fan has never come on (not on now either).

Think this BMS is definitely not well.
I assume you have checked all connections to the cells and that the buss bars are secure.
If you turn down the charge voltages to 13.8 you can run the battery without a BMS, just keep a watch on the voltage and don't let it get below 12v. The Kisae controller you have allows user settings.

You may be able to get something from eBay de or Amazon de,

example,

Mike
Good find there 👍

I'm staying with family in Denmark from tomorrow so reckon I'll have a look and see what I can find on German or Danish ebay.
 

Kerry downunder

Solar Enthusiast
So I disconnected the BMS and no change however when I test the voltage with the system negative disconnected the voltage jumps to 12.4v (which is still too low as the batt is at 13.4v) and drops back to 10.5v when I connect it again. (see pictures)

I've checked all the negative connections and all seem fine.

Im scratching my head at this one. 🤷‍♂️
I was told by Daly to put it on charge to activate the BMS.
 
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