Balancer and BMS options

[Cowpoos]

Can members with Lithium battery systems list/link options for battery balancing they use. The plus's and minus's of your system.

And....if you did it again, would you use the same equipment?

[john61ct]

Pretty sure nearly everyone here top-balances, and uses their BMS for that.

aka passive balancing, bleeding / resistive method. Usually requiring a **very** high SoC start-balance setpoint near charge termination. And usually at a **very** slow balance current rate measured in mA.

There are alsi many other different kinds of dedicated balancers, aka "non-protective BMS", but it's very rare to see those even mentioned here.

Some don't have a readout of their cell (group) level voltages without getting out a voltmeter.

And many use drop-ins with the BMS sealed in, IOW have no access at all to the balance leads, and thus no way to tell if / when balancing's getting done.


Some use no BMS at all, or at least not for balancing, they just balance initially at commissioning time,

using a lab-style adjustable PSU and maybe an ammeter

that would include those who bottom balance, or even at the mid point.

Some never balance, at all, just leave the cells as they were received from the factory,

and often find they never or very rarely even need to worry about it, just keep voltage away from the shoulders.


As you can see, your philosophy of how you want to use your cells and what sort of approach you want to take toward balancing and otherwise caring for your bank

in reality comes before, and is fundamental to the question of "what gear" you use, if any.

Many just accept what the vendor sets up, without fully understanding how it works, and just assume all is well until they notice a problem.

So good on you, for being at least interested at that level.

[rvlandlubber]

I have been using the Zeva 8 cell battery monitor module and the Enerdrive ePro battery monitor for battery protection.
I prefer a simple, centralised BMS like the Zeva rather than a distributed type using cell boards.
For balancing I use the QNBBM-4S active balancer from Electric Car Parts Company.
For my fractional C usage pattern, I have found that I do not need to balance continuously, typically once a year when I do the discharge test.
I like this device because I can easily disconnect it when it has balanced the cells. In my view, the less electronics permanently wired to cells the better, in case of failure.
Very much agree with John’s comment regarding care and management philosophy. As they say, there are many ways to skin a cat.

[rvlandlubber]

Originally Posted by rvlandlubber

I have been using the Zeva 8 cell battery monitor module and the Enerdrive ePro battery monitor for battery protection.
I prefer a simple, centralised BMS like the Zeva rather than a distributed type using cell boards.
For balancing I use the QNBBM-4S active balancer from Electric Car Parts Company.
For my fractional C usage pattern, I have found that I do not need to balance continuously, typically once a year when I do the discharge test.
I like this device because I can easily disconnect it when it has balanced the cells. In my view, the less electronics permanently wired to cells the better, in case of failure.
Very much agree with John’s comment regarding care and management philosophy. As they say, there are many ways to skin a cat.

Oops, missed the last part of your question.

Yes, I would use the same equipment again.
If I needed to replace the Zeva and it was not available, I would consider the REC.

[john61ct]

Originally Posted by rvlandlubber

For balancing I use the QNBBM-4S active balancer from Electric Car Parts Company.
For my fractional C usage pattern, I have found that I do not need to balance continuously, typically once a year when I do the discharge test.
I like this device because I can easily disconnect it when it has balanced the cells. In my view, the less electronics permanently wired to cells the better, in case of failure.

Very important point that last.

By having the balance leads accessible, you can just monitor as needed, passive gear being less risky than active.

The QNBBM gear is available from many sources, and so far seems to have a good rep.

This type of setup allows you to have a BMS that does not have any balancing circuitry.

But if yours does, you don't want both active at the same time, so check if that function can be disabled.

If the start-balance setpoint is at say 3.55Vpc, then if you terminate charge before reaching that point (a good practice for longevity), then the BMS balancing is in effect disabled.

That is, assuming you even have "a BMS" installed, rather than implementing those functions with alternative gear/methods.

[warrior 90]

I recommend evaluating a complete pack like from EV-Power or similar with all from ONE SOURCE

https://www.ev-power.eu/Winston-12V-...1dm9alvfge2qm2


with a Blue Tooth SMART BMS 123

https://files.ev-power.eu/inc/_doc/a...S123-Smart.pdf

Very clean cut with all info OnLine to match components to Your desired configuration
and make decisions before You order.
Easy to adapt to space and add on later if required.

If You follow the basic rules with Lithium on board it´s a one time SET it and Forget it. Most critical and weakest part of the whole energy system with Lithium is charging with alternator.

Easy to service and trouble shoot and when failure just install a new cheap board and moments later You are back in business. The boards are so cheap I would not even bother to repair. Just include a few spare boards already in Your initial purchase and exchange.
They are good quality and till now I can not find complaints online.
Calculate Your initial power requirement with prevision to space for posible add on later.

&

KEEP IT SIMPLE

[nebster]

No re-balancing here. Cells are within 1% after two years of continuous use.

You can get away with this if you:

a) buy fresh cells and verify them before assembling
b) keep them between 40 and 100F
c) charge and discharge at <0.5C
d) keep SOC between 8 and 92%

You don't even need cell-level monitoring if you can guarantee the above.

[kcj]

But how do you know if you don't cell level monitor?[emoji4]

I'm going going into my fourth year of 600ah bank... In season usage is 240-275ah per day... System is rock solid... Until you get to those pesky knee walls... I like to know where they are...

Btw I NEVER leave a shore charger on unattended, and rarely more than a couple of hours... Primary charge is solar, genset when clouds and wind direction are not cooperating.

But I do monitor my cell voltages like a hawk...

Ymmv

[john61ct]

Yes even with top-notch well-matched brand-new cells

and these days almost impossible to find a vendor that delivers on the well-matched part

eventually every pack will wear and then imbalances emerge as explicit issues needing closer attention.

I'm not saying **live, in use** per-cell monitoring is always required in the first few thousand cycles

since staying well enough away from the shoulders prevents actual problems from emerging then,

but the "watch like a hawk" stance is the right one, even if done via periodic test cycling while the bank is offline, ideally on mains power.

Just trusting a monolithic BMS to handle everything for you without independent fallback / verification is IMO a much higher-risk proposition.

[warrior 90]

I don´t recommend it because it´s just too easy to get used to not care anymore

But if the bank has a good margin actually You never get to the limits with solar and on the low side with a small GEN getting a fast bulk charge does not cost too much time.

I would prefer a parallel charge to full with all cells once per year on the technical side
But of course that costs taking the whole pack apart

[nebster]

Originally Posted by kcj

But how do you know if you don't cell level monitor?[emoji4]

You still have to test.

In my case, I did that monthly for a while, and then every three months for a while. Now I take the pack offline and verify voltages every six months. As long as they keep not moving, I'll save my time for something more productive.

[nebster]

Originally Posted by warrior 90

I don´t recommend it because it´s just too easy to get used to not care anymore

It's really just one more item on the maintenance list.

I could also choose not to change the engine oil (and probably it would be "fine" for years), but I think most of us aren't wired that way. Know yourself, though.

[warrior 90]

Originally Posted by nebster

It's really just one more item on the maintenance list.

I could also choose not to change the engine oil (and probably it would be "fine" for years), but I think most of us aren't wired that way. Know yourself, though.

Sorry, maybe I did not explain myself clear
That was in regards to Johns´s commentary

*I'm not saying **live, in use** per-cell monitoring is always required in the first few thousand cycles

I know people that run their LFPs for years like that with just cheap visual individual monitors. They say... after years I don´t bother anymore.

In regards to YOUR wiring ?

Most critical in regards to imbalance is when batteries are cycling without never been charged to full and their seem to be some BMS out there that do a very lousy job at that.
On the battery monitor that will not show up. The BMS is in a black box and only interferes when 1 cell starts to reach the top. So You will not be aware of. Same happens if one cell is accepting less charge then the others and cycling closer to minimum state of charge where LFP batteries suffer most in regards to life cycle.

On the flip side the person that is only using individual cell monitoring at least knows the state of charge of his batteries all the time.... if he bothers looking ?

So actually this is much better. The problem is, one can not stare 24 hour at the monitors every day

[john61ct]

Well of course you need to schedule and follow your checklists, otherwise everything starts to fall apart.

I am not necessarily advocating one way or the other, but BMSs do fail, IMO much more likely than the cells themselves.

Even those costing hundreds, but definitely the cheap-chinese stuff built with counterfeit components.

Main points, somewhat in conflict are, KISS, and do not depend too much on just one layer of protection.

Either way to keep risks down you need to pay attention, not saying be obsessive but relaxed vigilance, staying aware of what's going on really is required no matter what, just as with all the other critical systems/ components of the boat.

[warrior 90]

Originally Posted by john61ct

I am not necessarily advocating one way or the other, but BMSs do fail, IMO much more likely than the cells themselves.

Even those costing hundreds, but definitely the cheap-chinese stuff built with counterfeit components.

Main points, somewhat in conflict are, KISS, and do not depend too much on just one layer of protection.

Either way to keep risks down you need to pay attention, not saying be obsessive but
*relaxed vigilance,
*staying aware of what's going on really is required no matter what,
*just as with all the other critical systems/ components of the boat.

Yeah, I think that is a healthy attitude

I trust the batteries more then all the BMS no matter where they come from.
If LFP don´t last it´s most likely because the same systems that are supposed to prevent that are failing