Charging mystery, BMS defective?

[JeffKim]

I sing the praises of the Victron Phoenix 50A charger, but now I'm wondering if it's overkill for our batteries and have a bit of a mystery. (Longer than necessary anecdote follows...)

When we got our GT last year I installed 4x100Ah HQST bargain-basement batteries and ditched the WFCO AD charger for the Victron. So far there haven't been any issues. Two days ago, we picked up our trailer from the AS Factory Service Center after a month getting some panel work and warranty items fixed. The batteries were at 33% according to the Victron shunt. Stopping at RV park on the way home we plugged in and noticed the indoor lights were flickering periodically. I thought maybe it was bad power, but the EMS didn't detect anything. I checked the charger in the Victron app and it was cycling between charging at 45A or so for a minute then dropping to zero amps for 10 seconds or so coinciding with the lights flickering. I thought maybe the charger was overheating, but it wasn't hot to the touch.

However, I heard a clicking under the bed where the batteries are located but there aren't any switches or relays there so it occurred to me maybe it was a BMS. So, I looked up the specs on the HQST batteries and they state they can be charged at 50A short term but the recommendation is 20A. With this information I dummied down the charger to 30A and that fixed the problem. No more flickering, the charger was putting out a constant 28A or so and by morning the batteries were fully charged.

So now I'm wondering:

1. With my elementary electrical knowledge, 50A charging is distributed over the four batteries in parallel so each is getting 50/4 = 12.5A, so any of the four BMSs shouldn't overheat and switch off? I have them mostly balanced with the positive hooked to the first battery and negative hooked to the last battery.
2. Even if one BMS switched off charging, shouldn't the remaining batteries keep charging? Why did the whole the bank switch off?
3. So, now I'm wondering if a the 30A charger would have been sufficient for these batteries? Or is something with the batteries/BMS not right?

[AstroBruce]

Try putting a constant load of 50 amps or so on the system, using the inverter. Then see if the charger can supply its rated 50 amps. If not, the charger is the problem.

Bruce

[richard5933]

Couple of thoughts...

Bargain basement batteries - something doesn't seem right that the batteries can't withstand a 50a charge for more than a short time. That's the recommended charging rate for Battleborn batteries, so perhaps you've found why they were such bargains.

Regarding the BMS - do the batteries talk to each other?

I agree with confirming where the problem is. By doing as recommended above and applying a load large enough you can test to confirm that the charger can supply a steady 50a charge. Might be difficult to actually get a 50a load though unless you've got an inverter and can plug in a high-draw item to it.

Once you know that the charger can maintain a 50a supply over time, then you can do some more research on the batteries and their settings.

[sfranklin]

Originally Posted by richard5933

Couple of thoughts...

Bargain basement batteries - something doesn't seem right that the batteries can't withstand a 50a charge for more than a short time. That's the recommended charging rate for Battleborn batteries, so perhaps you've found why they were such bargains.

I hate to agree here, but almost any of the batteries I've scouted out can handle 50a charging or even 100a for a short period of time.

[JeffKim]

The batteries don't communicate, so I'm still wondering why if one cuts out then the current should continue charging the other batteries. I don't think they all cut out simultaneously. So maybe it's the charger? I'll try the 50A load on the charger as well, good suggestion. However, it occurs to me that the inverter transfer switch will be activated when on shore power, so no inverter. Edit: I can unplug the inverter from AC it occurs also.

And confirming that in parallel four batteries should be charging individually at 12.5A? Which is way below the 50A threshold.

I readily admit getting less than BB batteries creates doubts. But the specs say they should handle 50A charging. I'll check with the manufacturer as well.

[JeffKim]

I have another hypothesis. The batteries go through the bus bar and a 50A breaker. Maybe this is tripping? The clicking I'm hearing is the breaker not the BMS. (I forgot about these breakers.) If so, the type 2 would reset when the current goes to zero because the batteries are no longer drawing any current. It's less than 50A, but maybe 45A or so is within its tolerance. This should be pretty easy to check.

[JeffKim]

I'm back to working on this problem (if anyone is still out there). I did isolate the clicking to what appears to be one of the breakers at the positive bus bar.

And the problem is getting progressively worse which is weird. After I set the charging to 40A that worked for a while, then same problem (spiking charge current), so I reset to 30A (we were leaving on a trip so I didn't have time to work on it). We returned from our trip and it was unplugged for a few weeks then yesterday I plugged it back in and now it's spiking at 30A. I set charging to 20A and it charged without any spiking.

I have some time to look at it. I'm going to try and figure out if it's a breaker for sure by taking it out of the loop and connecting directly to the battery wire as a start. I don't know anything about the resetting Type 2 breakers or how easy they are to replace if that's the problem. Anyways, I like a good mystery but it's also a misery.

[uncle_bob]

Hi

Breaker wise, I'd pull the breaker and see if it's a 50A unit. I'd bet that it is. Once it heats up, who knows what the trip point might be. If it's "been there forever", 50A is a pretty good bet.

Off to BMS land ....

If the batteries have a max charge current of 50A, they also may have a max *discharge* current of 50A. Typically both these numbers match up. One of the ways to save money when making a battery is to use a cheaper BMS. The lower the current, the less the BMS costs.

What does the BMS *do* when there's an over current?

Pretty much all of them disconnect the battery entirely. It "goes to sleep" for some amount of time (seconds .... minutes ....). It then tries to hook back up.

If you have 4 batteries and are counting on getting 4x50A ( or 4x 20A long term) this can be a problem. A spike comes along and one battery drops out. You now have the three others sharing the load. Can they keep up? Maybe they can.

If your inverter is pulling 150A (as many do) 20A or 50A BMS's are not a really good idea. A 100A (steady state) and 250A max sort of BMS would be a *much* better choice.

Charge wise, you really do want to get the batteries back to full fairly quickly. Charging 400AH of battery with a 20A charger would be utter nonsense. Ideally something up around 80 to 100A is what you might want to use.

Fun !!!

Bob

[G8trwood]

After sitting, you could have one battery out of balance and the bms is shutting down while it tries to balance. This would send more current to other batteries and maybe cause a ripple effect? Maybe a low charge for a few days to top balance without triggering bms. You could also look at your voltage settings. Try charging at 13.4,5,6 and see if it takes it without a problem. Then go up a 1/10th at a time to 13.8-14

I would replace any noisy breaker and double check all connections.

That said. 50amps divided by 4 batteries is well under the current.

[uncle_bob]

Originally Posted by G8trwood

After sitting, you could have one battery out of balance and the bms is shutting down while it tries to balance. This would send more current to other batteries and maybe cause a ripple effect? Maybe a low charge for a few days to top balance without triggering bms. You could also look at your voltage settings. Try charging at 13.4,5,6 and see if it takes it without a problem. Then go up a 1/10th at a time to 13.8-14

I would replace any noisy breaker and double check all connections.

That said. 50amps divided by 4 batteries is well under the current.

Hi

Until you get the batteries up to 14.4V or something like that, you aren't going to trigger the equalization part of the BMS. Without that, any battery imbalance is likely to persist.

Bob

[JeffKim]

Another point of intrigue, this started after we had repairs done in JC. They replaced an outside panel but had to remove the furniture on that side. I checked the connections and they seem ok. Anyways... back to it.

Thanks, I'm still betting on fuses rather than anything to do with the BMS. The shutdown clicking isn't in the area of the batteries.

[G8trwood]

A number of the batteries start balancing if one cell is over 3.4 and there is a cell variance of 25mv or greater. One reason that the some companies recommend initial top balancing at a low current, otherwise the charger kicks on and the bms immediately trips. But they are all different. SOK, Epoch and LiTime use similar programming.

If you had a low cell, it is pretty easy to get a runner with a higher amp charge that triggers a bms shut down. But in general, the bms repeatedly shutting down to balance it can cause issues with some system’s (alternators). I do not have your expertise, so mmmv .

[JeffKim]

I did some testing and putting a 50A current across one of the 50A type II breakers kept tripping it. The other 50A breaker was ok. So, I ordered a new one and I'll see if that fixes the problem.

The BMS was likely a red herring, I will have more confidence in my batteries going forward. JC was another one, but I'm pretty angry with them with our stovetop saga.

[Wazbro]

Originally Posted by JeffKim

I'm back to working on this problem (if anyone is still out there). I did isolate the clicking to what appears to be one of the breakers at the positive bus bar.

And the problem is getting progressively worse which is weird. After I set the charging to 40A that worked for a while, then same problem (spiking charge current), so I reset to 30A (we were leaving on a trip so I didn't have time to work on it). We returned from our trip and it was unplugged for a few weeks then yesterday I plugged it back in and now it's spiking at 30A. I set charging to 20A and it charged without any spiking.

I have some time to look at it. I'm going to try and figure out if it's a breaker for sure by taking it out of the loop and connecting directly to the battery wire as a start. I don't know anything about the resetting Type 2 breakers or how easy they are to replace if that's the problem. Anyways, I like a good mystery but it's also a misery.

Very normal for a failing breaker to fail at progressively lower amps the more times it trips. As in it doesn't get better when it is dying, it keeps getting worse till it doesn't work at all or you replace it.

[rowiebowie]

Originally Posted by JeffKim

I did some testing and putting a 50A current across one of the 50A type II breakers kept tripping it. The other 50A breaker was ok. So, I ordered a new one and I'll see if that fixes the problem.

The BMS was likely a red herring, I will have more confidence in my batteries going forward. JC was another one, but I'm pretty angry with them with our stovetop saga.

Have you checked for software updates to your Victron charger just in case something is glitching there?

[uncle_bob]

Originally Posted by JeffKim

I did some testing and putting a 50A current across one of the 50A type II breakers kept tripping it. The other 50A breaker was ok. So, I ordered a new one and I'll see if that fixes the problem.

The BMS was likely a red herring, I will have more confidence in my batteries going forward. JC was another one, but I'm pretty angry with them with our stovetop saga.

Hi

A 50A breaker on a 50A charger is *not* a good combination. The 80% rule very much applies there. If you are running 50A on a regular basis, the breaker should be rated at 20% more than that.

50A x 1.2 = 60A.

Indeed the wires are the thing that limits things. A 60 amp breaker on a 50 amp wire is *not* a good idea !!!

Bob

[JeffKim]

Originally Posted by uncle_bob

Hi

A 50A breaker on a 50A charger is *not* a good combination. The 80% rule very much applies there. If you are running 50A on a regular basis, the breaker should be rated at 20% more than that.

50A x 1.2 = 60A.

Indeed the wires are the thing that limits things. A 60 amp breaker on a 50 amp wire is *not* a good idea !!!

Bob

Yes, good point. However, I'm using the same fusing and wire from the factory so Airstream thinks it's good enough (ha, ha). What mystifies me is that I replaced the original WFCO 55A charger with the Victron 50A. So they have a 50A breaker with a 55A charger. With most of their wiring they seem to be right on the edge, but I guess they know what they're doing.

I did notice the terminal going to the bus bar from the charger got very hot to the touch.

[uncle_bob]

Originally Posted by JeffKim

Yes, good point. However, I'm using the same fusing and wire from the factory so Airstream thinks it's good enough (ha, ha). What mystifies me is that I replaced the original WFCO 55A charger with the Victron 50A. So they have a 50A breaker with a 55A charger. With most of their wiring they seem to be right on the edge, but I guess they know what they're doing.

I did notice the terminal going to the bus bar from the charger got very hot to the touch.

Hi

Ok ..... but .... The WFCO charger pretty much never ever puts out more than 35A no matter what the label says. There are lots and lots of threads here documenting this "interesting tidbit". It's not the only similar converter to have pretty much the same issue. ( = the cheap ones you would replace it with do th same thing).

Why does it do this? I'd bet it's power limited. Maybe it'll put out 55A at 6V into a near dead lead acid. Get up to 12V and you have cut back to <40A.

Your Victron charger happily puts out its rated current at any voltage you set it to (at least mine do ....). If it says 50A, you get 50A (or maybe just a little bit more .... ).

Check the wire to make sure it's "ok" for a higher current. Then go to a bigger fuse / breaker. Yes, you *could* cut back the current on the charger. Since you are in there replacing things anyway ... fix the problem .

These self reset breakers are typically heat driven. The more current you have, the more the element heats up. When it gets too hot, it goes "click". When it cools back down it resets (clicks again). It is not unusual for them go get a bit warm at full load.

Bob

[JeffKim]

Originally Posted by uncle_bob

Hi

Ok ..... but .... The WFCO charger pretty much never ever puts out more than 35A no matter what the label says. There are lots and lots of threads here documenting this "interesting tidbit". It's not the only similar converter to have pretty much the same issue. ( = the cheap ones you would replace it with do th same thing).

Why does it do this? I'd bet it's power limited. Maybe it'll put out 55A at 6V into a near dead lead acid. Get up to 12V and you have cut back to <40A.

Your Victron charger happily puts out its rated current at any voltage you set it to (at least mine do ....). If it says 50A, you get 50A (or maybe just a little bit more .... ).

Check the wire to make sure it's "ok" for a higher current. Then go to a bigger fuse / breaker. Yes, you *could* cut back the current on the charger. Since you are in there replacing things anyway ... fix the problem .

These self reset breakers are typically heat driven. The more current you have, the more the element heats up. When it gets too hot, it goes "click". When it cools back down it resets (clicks again). It is not unusual for them go get a bit warm at full load.

Bob

It seems a little strange AS would count on the charger providing less than its stated output, but then that was my observation with the WFCO. Once I got the stupid AD to recognize my lithium batteries it put out 40A for a bit then went to 18A and settled down at 9A. The batteries were at 70% or so.

Good point, fix it. The wire is 6AWG going to the charger and the batteries. The charger wire is about 10' and according to the Explorist wire calculator 6AWG is adequate at 50A or even 60A. They only make up to 50A type II breakers, so not much I can do with those. And there's two of them one coming from the charger/load side and the other to the batteries which I have routed through the Lynx.

I currently have a 100A MRBF fuse on this attached to the Lynx, before I knew about the breakers, so it doesn't do anything except maybe if something went really wrong. I could replace it with a 60A or so and remove the breakers, but that doesn't feel like a good idea. So, not sure how to improve things.

[uncle_bob]

Originally Posted by JeffKim

It seems a little strange AS would count on the charger providing less than its stated output, but then that was my observation with the WFCO. Once I got the stupid AD to recognize my lithium batteries it put out 40A for a bit then went to 18A and settled down at 9A. The batteries were at 70% or so.

Good point, fix it. The wire is 6AWG going to the charger and the batteries. The charger wire is about 10' and according to the Explorist wire calculator 6AWG is adequate at 50A or even 60A. They only make up to 50A type II breakers, so not much I can do with those. And there's two of them one coming from the charger/load side and the other to the batteries which I have routed through the Lynx.

I currently have a 100A MRBF fuse on this attached to the Lynx, before I knew about the breakers, so it doesn't do anything except maybe if something went really wrong. I could replace it with a 60A or so and remove the breakers, but that doesn't feel like a good idea. So, not sure how to improve things.

Hi

If you want to "do it right" and the wire runs are more than a few feet each:

You have a protection device at each and every power source. The batteries are a power source. The charger is a power source. The 7 pin is a power source, and the solar is a power source.

All of those protection devices are rated to protect the wire you use. How much current that is depends on the wire gauge and the insulation type on the wire. It also depends on the temperature rating of the material that the wire goes up against in its travels.

You rate the wires to carry the amount of power that the sources are expected to put out. You also (in a DC circuit) rate them to have acceptable voltage drop at the expended load currents. Typically voltage drop wins that fight ( = you use a fatter wire than the one that barely carries the current without catching fire).

Them's the rules if you want to do it all and have each and every regulation you can find agree with what you did. (yes, there are more fiddly details than noted above ...).

Typically in an RV, most folks don't go with the "double fuse on every wire" stuff. If you are wiring a super yacht and want it to be insured, you most certainly do go with the double fuse stuff.

Simple answers in your case (simple because it's not my money, time or frustration doing it ...):

1) Go up to a piece of number 2 wire (from the number 6) and keep your 100A fuse. Both the ground and hot need to be same size ...

2) Scale back the converter output to 40A via the programming interface.

3) Keep the number 6 and *maybe* go with a 60A fuse. Scale back the converter output to 48A to be at 80% of the 60A number.

Those are just the most likely choices.

Bob