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Old 11-12-2022, 01:14 PM   #1
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Done with Daly - Recommendations on a BMS please...

Resurrecting this thread https://www.skoolie.net/forums/f49/n...ast-36214.html under a new name.

I've had my Daly 250A 4S BMS in operation for about a year. Figured out how to install and program it, and after some fooling around, got the parameters set.

I have a Victron SmartShunt on the 280Ah LifePo battery (built from four cells), then the Daly on the ground/return path.

On the charging side I have 475 watts of solar pumped through a Renogy 40A MPPT charge controller. I also have a household current Noco 20A charger, used rarely, and a Renogy 20A DCDC charge controller, not yet connected.

The Daly worked beautifully for about six months, until one day I was walking past the bus and hear the alarm beep. Low voltage, like 1.5 volts, on one cell! High voltage on another. I unplugged the control line to the Daly, put the multimeter on each cell, and saw they were each within a millivolt of 3.27.

Panic over, I fooled around with the Daly, it still recorded the low/high alarm. Checked voltage at the pin on each lead from the battery, perfect reading. Clearly something was wrong in the Daly itself.

I left it unplugged overnight, and the next day it fired up fine and worked as if nothing was wrong.

Four months later, the same thing. I didn't panic, just unplugged it, left it for a day, and all was right again. but I was irritated enough to go out and buy a RadioB BMS, and said to myself the next time that frikkin' BMS went wacky I'm ripping it out and putting in the replacement.

The Daly must've heard me swearing, because it ran fine all summer, until early this past week. Same thing: a screaming alarm, voltages (each time different cells) showing all over the map. I said no biggie, unplugged it, waited a day, plugged it back in, no luck-same alarm, different cells (not all, some). Fiddled with the BMS, reset it, etc., but no luck. Now five days later it seems to report all is fine, proper voltage readings, but it appears to be turned off or something, multimeter readings somewhere between 2.9 to 6.9 volts on the bus bar. I'm going to rip it out because I can't have flaky equipment.

First nail in the coffin: Daly literature is comically crappy, translation, instructions, programming tips. Daly online advice is either missing or poor. Where Renogy resources for programming are like a B-, I give Daly an F+, the plus because you think you can sort out how to program it but in reality the documentation is just screwing with you and you're completely on your own. Now, in addition, I'm experiencing this weird, intermittent, unexplainable failure. Yeah, maybe it's just a bogus unit I got, but I do not want to buy another Daly.

I've stated my opinion elsewhere here that the DIY community for LiFePo batteries is enthusiastic but the components are generally very poor and not yet adapted to the serious enthusiast. This is (I think) particularly true in the BMS space--I don't see another one that strikes me as any more solid.

For that reason I want to be able to quickly swap in the RadioB unit I got as a temp spare to use if the BMS fails on the road. You can't do squat if your BMS has failed, unless you simply bypass it, which I won't do.

I'm in search of a solid 250A BMS. Any suggestions?

Like I said, I'm done with Daly, but if you have different experience, or any insight into why the thing is failing, I'd love to hear. Tell me I got a bum unit so I don't have to learn a new BMS system.

Cell Balancing note: after more than a year of use my LiFePo battery has never needed cell balancing. When I installed the Daly originally I turned off the cell balancing function. Online research indicated that it either doesn't work or only kicks in under corner case scenarios, and I wanted to understand my cell drift. Along the way I did some research on cell balancers and bought a twenty dollar active balancer and wired it in. Worked like a champ under test conditions, but as mentioned I leave it unplugged and so far despite the Daly screaming otherwise haven't had to use it.

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Old 11-15-2022, 10:51 AM   #2
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Update: I disconnected the charge controller and all loads, just letting the BMS run with alarms. Battery is at 13.1, output from the Daly is 2.9V.

3 days later, the Daly is working per spec without any changes from me, so whatever transient condition was causing the problem in the Daly, it's gone. Battery still sits at 3.27 per cell using the multimeter.

I've found few BMS alternatives to Daly in the 200+ Amp range, but I'm still looking for 'anything but Daly'. Digging into Victron products to see what they sell for plain old BMS.
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Old 11-15-2022, 11:13 PM   #3
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Yet another update: I'm seriously considering eliminating the BMS. After a bunch of research I'm inclined to think the market has moved on from DIY LiFePo to integrated batteries, because a lot of the on-line resources are looking a bit dated. Meaning people just aren't taking the plunge into building their own batteries, so there isn't a healthy market for quality key components-like BMSs.

Maybe it's just too much trouble for most people. Just go buy a Battleborn or two...

But regarding battery management, I don't need something that balances automatically-my cells don't drift (yet, I guess). Not even a tiny bit. And as I said before, I have that handy active balancer I can plug in if needed.

And the charge controller handles low temp and overcharging, so theoretically no need for those controls.

I just need low voltage control, and I can do that with about fifty bucks of components, readily available and cheap to replace. I'm feeling pretty confident about this, actually.

Anyone have an opinion on this?
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Old 11-16-2022, 05:07 AM   #4
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I have concerns about the non commercial bms systems. The MOSFETs that if fail in conducting mode Can discharge or overcharge your battery and cause a fire seems to be bad practice.
Software that has no description how it operates under worst case situation is dubious as well.

So far I have my upper voltage limit set with my charge controllers. For balancing we use an inductive board that contains only hardware and no software.

I am planning to add a hardware controlled overvoltage diversion load in the form of heating water, making ice and or dumping energy into preheating the engine block.

I do not mind resetting my labtop or phone ones in a while in case it hangs up but for a safety device like a bms that is inconceivable.

There are some nice Motorhome bistable relays that would be good as power components for these tasks and also shunt trip coil breakers. Both seem to be good choices for this application.

Johan
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Old 11-16-2022, 09:30 AM   #5
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Thanks-good to hear a similar position.

I'm not convinced spending a couple hundred bucks on a BMS again makes sense.

On to documenting the requirements for 'battery management' so I can see if off the shelf components can do it, and possibly do it better than what's on offer at Amazon and Alibaba.
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Old 11-16-2022, 10:21 AM   #6
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The below is a copy of my post at diy solar


Sep 5, 2022
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#1
I was curious about this 4 cell active balancer board. It has 4 transformers so it seems to be a stack balancer transforming the cell voltage back to the overall assembly voltage.
Tested a slightly unbalanced 280 ah 4 cell pack and it seems to work, some voltage came down and others went up.
So the question is how does it work under the coating.
Decided to sacrifice a unit for knowledge and scraped the coating.
See pic..
The transformer has three windings.

Below the transformer are two MOSFETs A07T. Then the circuits in front are same components.

The large component is an option coupler El3H7.

Above that a KL3 3 pin.

Above that and directly below the inducter is diode K14.

Then on the left next to the white connector.
A mystery chip C3J0.

Above the silver selector switch are two
7002 MOSFETs.

It looks like the pattern of the black coating is all the same..
That would mean that the control is in the mystery chip.

Any suggestions / interest.

johan




End of copy paste.

There are some more posts and measurement analyzing this board and it seems it is hardware only.

The second picture I uploaded is a MOSFET based bms with passive balancing and a custom hardware chip.. the chip comes in version for lithium phosphate or lion.
Documentationnof the chip is available from the manufacturer.. I liked this board because it has little led that illuminate when the corresponding cell is balancing.
It also has separate charge and discharge MOSFETs.
Not good for large currents but ok for a DeWalt battery pack.

Johan
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IMG_20220905_115358757.jpg   IMG_20220831_143402811.jpg  
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Old 11-16-2022, 04:26 PM   #7
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Yeah, probably not a completely custom chip but some kind of programmable SOC for this sort of operation.

I know there's a lot of interest in the cell balancing function but here's an active balancer for under fifty bucks that works like a champ:
https://www.amazon.com/Equalizer-Bal...49&sr=8-1&th=1

I've turned off the active balancing in my Daly. Couldn't find enough theory of operation to feel comfortable trusting it, especially given the YouTube videos around Daly's balancing functionality.
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Old 11-23-2022, 06:36 PM   #8
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I've ditched my Daly's for ones from Overkill Solar. I've been quite happy with them, although I don't think they go to 200A. I have the 100A, 24v version.

- Jeremy
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Old 11-23-2022, 11:32 PM   #9
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I have a friend who built his own battery bank and added a bms to the package and started to have funky problems with the setup. Turned out to be some problems with the temp sensors that came with the bms. Just saying.
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Old 11-27-2022, 03:11 PM   #10
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Quote:
Originally Posted by Dragonpop View Post
I have a friend who built his own battery bank and added a bms to the package and started to have funky problems with the setup. Turned out to be some problems with the temp sensors that came with the bms. Just saying.
Thanks-I was getting cell voltage alarms, not thermal, but appreciated.

I disconnected the Daly and took it apart. It's a sealed unit--the only thing you can remove are the two heat dissipation plates, otherwise it is completed contained within a molded plastic case. I put it all back together and it now reads EEPROM error.

It seems the market has moved to smaller LiFePo sizes with built-in BMSs, and there's no competitor to Daly in the plus 200 range.

Well, maybe Victron, but I had tweety birds around my head trying to make sense of their offerings--many components, none that provided just a straight-up BMS for a DIY 280 amp setup.

Against my better judgement, I bought a replacement from Daly-this time with the two year warranty.

However I'm sourcing the components that provide BMS functionality-low/high voltage and individual cell voltage monitoring, so I have a decent electromechanical backup to a vital but problematic device, the BMS.

I guess the lesson I'm learning is every part of the electrical system should have redundancy of some kind--a replacement part, or alternative. Otherwise your entire system can be shut down without any way to limp along...
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