Headaches with Daly BMS.

Seacap

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Feb 13, 2020
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Hi all,
I’ll try to make this short. Received 4 200a cells on the island of St Martin 1 1/2 years ago. Could not get a BMS to use so I rode bare back until just recently. The cells were all equal all the way up to 13.4v, never charged higher than that as I was being careful without BMS. Never went below 12.8v.
So everything was running fine until I installed a Daly BMS. Now all hell has broke loose 😡. When I started monitoring with Bluetooth everything looked good for a couple of weeks. One day I fired the engine up and stated charging with the alternator. Voltage started spiking up to 14.8v and back to 13.6v. I could hear the load coming and going on the engine. Checked Bluetooth and my #4 cell was up to 3.7 with a delta of .5 with the other cells. I’m on a boat and did not have equipment to top balance or anything. The Daly balance function didn’t seem to be doing much of anything. I noticed that my #1 cell was at the lowest voltage. So I switched them around. (Please note at this point my meter said all cells were equal). This switch worked wonders and everything was running smoothly with only a delta of around .03 to .05 while charging and .003 at rest.

Then it started again. $&)($&&!!

This time my batteries were down to 12.95 when I started charging. All cells were equal via meter. The spiking again was up to 14.8v. Blue tooth was showing my #4 was again spiking from 3.2 to 3.8 instantly for a delta of around .6. Same as before before I swapped 4 and 1.

I suspect the BMS. Has anybody else run into this problem?
 

rickst29

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Hi, Seacap. It sounds quite likely that Daly is acting a bit slow to cut off the charging circuit when the engine/alternator offers 14.8v. But other than that, the spiking behavior (and variable engine load) is likely an issue between the engine/alternator ECM and the Daly, alternating between "cut-out" and "enable" while the ECM alternates between "the battery is desperately low, recharge at 14.8V!" and "the battery is OK, run the alternator in 13.6V normal operating mode".

I will SWAG that ECM probably provided for momentary 14.8V alternator charging at each engine start, for an extremely short period of time, even before a new BMS started to provoke "cycling". 3.7 Volts per cell is pretty high for LFP, and has probably cost you some battery lifespan during the pre-BMS days (although the cells don't become totally killed until they reach a significantly higher voltage, close to 4.2 Volts per cell).

So you've got a bit of a mess on your hands. One way to stop the spiking behavior might be to raise of Daly maximum cell voltage to an excessive value, allowing the full 14.8v to be accepted, but to invoke balancing at 13.5 and above? With those settings, the engine/alternator ECM might calmly quiet down to 13.6v (after just a second or two) and then stay there, without having Daly shutdowns pushing it back up into 14.8V "emergency mode". over and over? This is SWAG, I have no experience with tuning a Daly for variable and often excessive charging voltage - but it might work. If you give it a try, please post back so that others might see this "solution" confirmed or denied.

Daly "smart" BMS balancing runs at extremely low current, requiring many hours of stable charge voltage to run effectively- but it should work, if the engine runs for long enough.
 
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Seacap

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Feb 13, 2020
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19
Thats
Hi, Seacap. It sounds quite likely that Daly is acting a bit slow to cut off the charging circuit when the engine/alternator offers 14.8v. But other than that, the spiking behavior (and variable engine load) is likely an issue between the engine/alternator ECM and the Daly, alternating between "cut-out" and "enable" while the ECM alternates between "the battery is desperately low, recharge at 14.8V!" and "the battery is OK, run the alternator in 13.6V normal operating mode".

I will SWAG that ECM probably provided for momentary 14.8V alternator charging at each engine start, for an extremely short period of time, even before a new BMS started to provoke "cycling". 3.7 Volts per cell is pretty high for LFP, and probably cost you some battery lifespan (although the cells don't become totally killed until they reach a significantly higher voltage, close to 4.2 Volts per cell). Daly "smart" BMS balancing runs at extremely low current, requiring many hours of stable charge voltage to run effectively.
part of the mystery. My smart controller on the alternator is set for bulk charging at only 14.4v and I monitor everything pretty closely and have never seen initial charging at over 13.7 going in.
 

Sharky722

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May 8, 2020
Messages
163
Most alt charge bms have a 3.9vpc cut off to prevent the sudden unloading of the alt.

I'd double check the connection of that #4 wire also make sure its sound.

You're going to have to do a top balance somehow and maybe install some active balancing.

Can you lower the charge voltage a little?
 

Abodyofscience

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Feb 21, 2022
Messages
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Your system is oscillating, an "undamped" oscillation. It whacks into the high limit voltage & then the low limit voltage, acting like a "bang-bang" control system.
https://en.wikipedia.org/wiki/Bang–bang_control

Better is a proportional control system.

Maybe the BMS needs a minimum battery capacity size to damp out these oscillations.

A larger flywheel on the engine may also work.
 
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Seacap

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Feb 13, 2020
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Your system is oscillating, an "undamped" oscillation. It whacks into the high limit voltage & then the low limit voltage, acting like a "bang-bang" control system.
https://en.wikipedia.org/wiki/Bang–bang_control

Better is a proportional control system.

Maybe the BMS needs a minimum battery capacity size to damp out these oscillations.

A larger flywheel on the engine may also work.
I just uninstalled the BMS and the bang bang stopped.
 

Seacap

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Feb 13, 2020
Messages
19
Hi all,
I’ll try to make this short. Received 4 200a cells on the island of St Martin 1 1/2 years ago. Could not get a BMS to use so I rode bare back until just recently. The cells were all equal all the way up to 13.4v, never charged higher than that as I was being careful without BMS. Never went below 12.8v.
So everything was running fine until I installed a Daly BMS. Now all hell has broke loose 😡. When I started monitoring with Bluetooth everything looked good for a couple of weeks. One day I fired the engine up and stated charging with the alternator. Voltage started spiking up to 14.8v and back to 13.6v. I could hear the load coming and going on the engine. Checked Bluetooth and my #4 cell was up to 3.7 with a delta of .5 with the other cells. I’m on a boat and did not have equipment to top balance or anything. The Daly balance function didn’t seem to be doing much of anything. I noticed that my #1 cell was at the lowest voltage. So I switched them around. (Please note at this point my meter said all cells were equal). This switch worked wonders and everything was running smoothly with only a delta of around .03 to .05 while charging and .003 at rest.

Then it started again. $&)($&&!!

This time my batteries were down to 12.95 when I started charging. All cells were equal via meter. The spiking again was up to 14.8v. Blue tooth was showing my #4 was again spiking from 3.2 to 3.8 instantly for a delta of around .6. Same as before before I swapped 4 and 1.

I suspect the BMS. Has anybody else run into this problem?
Another problem I’m seeing. My number 4 cell, my positive terminal keeps getting overcharged. When I first installed the BMS after about a week the #4 was way out of balance. A delta of about .5-.6. My #1 cell was the low cell. So when I started charging the #4 went right up very high. This is maybe why I was seeing 14.7 on my v meter. Since I had no way of balancing onboard and was anchored in a remote part of the Caribbean (I still am) I came up with an idea to swap the high cell with the low cell. It worked a treat. Everything got into balance. The high #4 quoted right down in the #1 position and the low #1 was happy at #4. Again everything was fine for about a week. Now #4 is spiking high and #1 is low. So I will do the switch again.

But why is this happening? I’m charging at around 50a with my alternator on a 200a pack. Mostly with solar but I top off with my engine alternator that runs a multi stage controller.
The solar just adds some amps but not enough to get ahead. I have a small boat and don’t have the real estate for more panels. Only have 300w and I get a lot of shading.
 

Seacap

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Feb 13, 2020
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Ok here is what I‘ve found. The Daly is crap. Or at least mine isn’t working properly.

Ok, we have finally isolated our charging problems to the BMS. When I installed the Daly my batteries were balanced (I had been bare backing up to this point for two years)I bought and installed the Daly for the protections it offers, not balancing. Although the advertising says it balances.



After a few days when I would start charging with my engine alternator I was getting huge spikes up to 14.8 or even higher. The BMS would indicate a fault and would shut down charging which was wrecking havoc with my alternator. This is even though my batteries were only showing 13.3v with a meter. (Yes I checked accuracy against a second meter). The BMS would also show a delta of up 1.300v when by meter all cells were 3.20v. So I would remove the BMS an all was good and I could charge once again.



Then I would reinstall the BMS. Everything would be working fine. Then a few charging cycles later the surging and shut downs would start all over again. So I would again uninstall the BMS and everything would show normal. So now I have uninstalled and it's staying that way for now.



Very disappointed after spending $160. I‘m starting to think Lifepo4 on a serious cruising boat is not a good idea. To many things can go wrong so a need to stay close to support like ordering new parts or obtaining specialized equipment or specialized knowledge. I am not an electrical engineer and my boat is only 28’. I just finished a wonderful 10 days anchored off an island here in the Caribbean. Most days we had the anchorage to ourselves. It was both peaceful and beautiful. Except for the days my BMS went batshit on me. That is not fun nor is it why I’m out here.
 
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The BMS would indicate a fault and would shut down charging which was wrecking havoc with my alternator.
What kind of havoc?
Is it this?
 
Last edited:
Joined
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It shuts down the charging and worries me about blowing the diodes.
Doesn't the bms shutdown charging to the bms protected battery only.
I mean the alternator will still supply current to every other consumer, no?
 

Seacap

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Correct, but I’m not an electrical engineer and it gives me pause when my engine start battery is full. Will that do damage then to the diodes? It’s just freaky to see your charging current spike up to 16.1v. What is happening to the engine start batt? So on and so forth.

but I have solved the problem and thrown the BMS in the circular file.
 
Joined
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Messages
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Correct, but I’m not an electrical engineer and it gives me pause when my engine start battery is full. Will that do damage then to the diodes? It’s just freaky to see your charging current spike up to 16.1v. What is happening to the engine start batt? So on and so forth.

but I have solved the problem and thrown the BMS in the circular file.
What BMS did you use for the replacement?
 

Seacap

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We have isolated the problem to the BMS. Alternator has nothing to do with it. I programmed the alternator to limit output to 14.2v, float at 13.3v
 

Mountainlion

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The BMS is a passive on/off switch. The spikes are coming from your alternator.

I would check terminal connections. Bad connections will not be obvious when charging with a low current.

Charging with a High output alternator can cause balance problems if you have bad connections.

I would lower the Bulk voltage on the regulator to 13.7-13.8V. That is enough for charging the bank to 95% SOC.
 

Seacap

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No, the spikes some how are caused by the BMS, maybe not created. But it all stops and runs fine when I remove the BMS. I put the BMS back on and it starts up again after a few cycles. It’s not rocket science. Maybe the alternator and BMS don’t play well together. But removing the BMS solves the problem.

I have been running the alternator at 14.2v but I never let it get higher than 13.9v and I manually shut it off. I don’t like to run things on automatic. I watch. I’m a gauge vs idiot light kinda guy. I even have a manual switch I can put the alternator into float mode at any point.

this is a new install and everything is nice and tight and heat shrieked. This is a 120a alternator that I get about 50-60a out of. I have a 3 stage smart controller that is programmable.

I am sitting here happily charging my batteries, almost full at this point (13.9). Not a BMS in sight 🙂. No spikes, nothing. My batteries are happy and I’m happy. All cells are balanced to 100’ths.
 
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Mountainlion

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No, the spikes some how are caused by the BMS, maybe not created. But it all stops and runs fine when I remove the BMS. I put the BMS back on and it starts up again after a few cycles. It’s not rocket science. Maybe the alternator and BMS don’t play well together. But removing the BMS solves the problem.

I have been running the alternator at 14.2v but I never let it get higher than 13.9v and I manually shut it off. I don’t like to run things on automatic. I watch. I’m a gauge vs idiot light kinda guy. I even have a manual switch I can put the alternator into float mode at any point.

this is a new install and everything is nice and tight and heat shrieked. This is a 120a alternator that I get about 50-60a out of. I have a 3 stage smart controller that is programmable.

I am sitting here happily charging my batteries, almost full at this point (13.9). Not a BMS in sight 🙂. No spikes, nothing. My batteries are happy and I’m happy. All cells are balanced to 100’ths.
How did you balance the
 

Mountainlion

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If you do not let the voltage go up more than (3.4V) cells will most probably be balanced. If you go higher you end up in the knee and your Delta V starts increasing very fast.
 
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