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midpoint panic


Gabriël

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ok, panic might be a bit over the top, but we are talking some serious money when it comes to batteries...

after a period of getting midpoint deviations of <0.4%, this morning it all of a sudden was 4%.
the situation occurred whilst the system was on batteries with a low load of about 400w at about 82% soc.
i switched to utility and the batteries started charging. the midpoint fell to 0.1% with soc at 83% [and rising] but started to increase to 0.6% when soc reached 95%. the batteries were at 13.4v, 13.5v, 13.5v, 13.5v just after switching to utility [82% soc]. these measurements were taken with all cables attached.
at 96%soc and charging, the batteries, with all cables attached, were at 13.9v, 14v, 14v and 14.3v and midpoint had increased to .7%. the image represents this stage.
i expect midpoint to increase even further. anticipating which i am going to disconnect the system in order to switch to utility and power off the inverter.
one of the thoughts running around in my head is should the ha-02 battery balancer not have prevented this midpoint deviation?
any suggestions are more than welcome!
God bless
g

midpoint.thumb.JPG.4dfc2fa54f434a61e34c82f27fc99712.JPG

 

 

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EDIT

at 100%soc the midpoint has come down to 0.4%, batteries now at 13.9v, 13.9v, 14v and 14.3v - image refers

 

midpoint01.JPG.c175a2d74a4c84c2a89a839e19e40197.JPG

Edited by gabriel
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2 hours ago, gabriel said:

one of the thoughts running around in my head is should the ha-02 battery balancer not have prevented this midpoint deviation?

There are some possibilities.

1. The balancer is incorrectly connected.
2. The balancer has failed partially (hence three of the batteries being fairly close and the 4th one out).
3. The balancer has failed completely
4. The balancer has not failed, but is working at full capacity and still can't solve it.

Simplest test, take a 12V lamp (car tail lamps work well, they are between 20W and 60W, and often provide two filaments for different power levels) and while charging, connect it across the high battery. If this drags the voltage down... then your balancer might not be working. Perhaps repeat the test with the balancer disconnected. If the lamp (which essentially passes current around the cell) can pull the voltage down using a few amps (the smaller filament is usually around 5W or so), but the balancer cannot, then you know what to blame.

That's actually an open question that's never come up: Quis custodiet ipsos custodes? Well, it is partially answered, the BMV watches the balancer... but visually the HA02 gives you no indication as to what it is doing. The other one has orange LEDs that tell you when it is working... :-)

That is to say, @PJJ, perhaps I gave you bad advice the other day, there might be something to the old-school way of doing it.

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Morning Gabriel

I'll give a potted history of my battery balancing experience.

My system I installed in July of 2015 and got a BMV towards the end of July and immediately noticed an imbalance of my battery voltage. I cast around for solutions and immediately built Zener regulators which I double up (2 of them in parallel for each battery). The Zeners worked but did not bleed off enough current. In my search for  a solution I discovered Victron battery balancers. Having just spent more than my budget on my solar install I gagged. Later I discovered HA01s which I could import from Lithuania of all places and the landed cost for the 3 units was equivalent to the cost of 1 Victron battery balancer. The HA 01s  arrived on the 11 of September 2017 and I immediately installed them  and even though there was a huge improvement I was still getting midpoint alarms of over 2.5%. Slowly the HA01s knocked my batteries into shape  and by Nov 2015 I stopped getting mid point alarms. I had not a peep out my BMV until Jan 2017, when I started getting alarms again. By this time I had bought an HA02 from @Chris-R and since the HA01 can shift 5A and the HA02 can shift 10A my problems were resolved . The  BMV started sounding an alarm in July 2017 and continued to do so until I replaced my AGMs with Pylontechs in Dec 2017.

What one must remember although the HA02 can shift 10A the voltage is not 12V but rather the voltage between the two batteries (really very little energy 10-20W). Thus if the imbalance is too great it cannot correct it quickly enough and the imbalance goes further. As one swallow does not a summer make so one alarm is not a reason to panic but is reason to be very concerned (perhaps years of farming have taken its toll and I have lost the propensity to panic). The 4% is high and definitely something to watch like a hawk. If I remember correctly you have one battery that is younger than the others and if I look at you data you have one battery that is lower than the others. A failing battery usually goes high. They sometime go low when they get plate sediment at the bottom of the electrolyte and start short out the plates (this is the ultimate method of failure of a lead-acid battery) but we usually sling them out before then..

Batteries are inclined to show their mid-point deviations during late absorb and so your deviation under load is troubling as to my mind it shows one battery that is not able to deliver

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hi plonkster and chris, thank you for getting back so soon.

46 minutes ago, plonkster said:

Quis custodiet ipsos custodes?

indeed! i believe that is one of the reasons this forum exists.

 

48 minutes ago, plonkster said:

Simplest test, take a 12V lamp

is there a way of doing this with a multi tester?

 

54 minutes ago, plonkster said:

1. The balancer is incorrectly connected.
2. The balancer has failed partially (hence three of the batteries being fairly close and the 4th one out).
3. The balancer has failed completely
4. The balancer has not failed, but is working at full capacity and still can't solve it.

1 can be ruled out, it has been working well too

2 might become obvious as we test the batteries as all connections have been taken off

3 ditto in conjunction with the 'lamp test'

4 could be if the batteries are tested separately

 

26 minutes ago, Chris Hobson said:

A failing battery usually goes high.

in this case it would be my no 4;  maybe this is the time for at least swapping no1 [the new battery] with no4 [to which the bmv shunt is fixed at present]

well we are blessed with rain [12mm between 0800 and 0900] and solar production will not be an issue today so i can concentrate on this issue

:)

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36 minutes ago, Chris Hobson said:

the HA01 can shift 5A

If you cannot resolve an imbalance by shifting 5A... that's not a good sign. I mean maybe if you're starting with a known imbalance and it has to work at it for some days, that I understand. I even told @Chris Hobson the other day how my two new LFP batteries spent the first week with one of them running warmer than the other one (each 12.8V battery on its own was balanced, but not as a bank, so the balancers were bleeding off energy). But if a battery suddenly develops a new imbalance and you cannot solve it with 5 amps... that would make me worried.

39 minutes ago, Chris Hobson said:

Victron battery balancers

Price has come down somewhat. It's around 1.1k a piece now, though I'm not sure what the exchange rate will do to us again. R15.63 this morning...

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1 minute ago, gabriel said:

In this case it would be my no 4;  maybe this is the time for at least swapping no1 [the new battery] with no4 [to which the bmv shunt is fixed at present]

well we are blessed with rain [12mm between 0800 and 0900] and solar production will not be an issue today so i can concentrate on this issue

:)

@plonkster tongue in cheek had a long explanation for why batteries at the one end of a string fail. I believe there is some merit in swapping batteries around (something I never did) as it seems always one of the batteries on the end fails first (usually No1).

Let us know the results of your tinkering.

 

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1 hour ago, plonkster said:

That is to say, @PJJ, perhaps I gave you bad advice the other day, there might be something to the old-school way of doing it.

Yeah I think I am rather going to go the standard Victron route then, I really want a almost "set and forget" setup, how could you comfortably go on holiday (especially if its for a few weeks) if you can't be sure your batteries won't go out of wack..

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1 minute ago, PJJ said:

rather going to go the standard Victron route then

If you can, hang for a bit until gabriel has a verdict. As I said, I believe this is a good value for money product, and as it transfers charge (I believe through a DC/DC converter mechanism) it is much more efficient, but they really can make it a little better by adding some LEDs that shows when a leg is active.

12 minutes ago, Chris Hobson said:

tongue in cheek had a long explanation for why batteries at the one end of a string fail

Actually I was being horrible sarcastic when I said that, if we're thinking about the same thing. Electrically speaking there is no reason at all for the battery to fail earlier. It's not as if there is some kind of higher electron concentration going on at the lower end of the bank, the fact that electrons flow from negative to positive has absolutely nothing to do with this observed phenomenon, as is sometimes alleged. I still think the main reason the battery (or cell) at the end tends to degrade faster is temperature. In cars it is usually the side closest to the engine for example...

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10 minutes ago, plonkster said:

....... but they really can make it a little better by adding some LEDs that shows when a leg is active.

The HA01s have LEDs. Perhaps it has something to do with the 2.4V to 12V topology  that the LEDs are removed on the HA02s.

Addition: Of the hundreds of HA02s that @Chris-R has imported he has not had a comeback yet.

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55 minutes ago, plonkster said:

Price has come down somewhat.

R 923 + VAT. I had one just because I got one 2nd hand, sold it after a while, as all was perfectly in balance.

 

53 minutes ago, Chris Hobson said:

... some merit in swapping batteries around ...

 

37 minutes ago, plonkster said:

... , as is sometimes alleged

Yonks ago I accidentally found a very interesting titbit when I was checking the cell water levels.

On fairly new batteries I saw a huge colour difference in the water of battery 1 versus the rest, as if it had more sediment stirred up.

That made me think that if there is a difference in the colour of the water, why not swap them around to give all a chance at being No 1.

Now if this is alleged mojo, or has real substance, for to date I could not find anyone substantiating the "science" bar my alleged mojo.

Touch wood, but to date I have not had a No 1 fail me yet, as we have experienced in SA.

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15 minutes ago, PJJ said:

how could you comfortably go on holiday

mine was 5 days and on arrival back home i got a 4% midpoint deviation as 'coming home present' - :( - the almost "set and forget option" [safo] will not only suit me, but especially my wife, but the, at what cost? who can come up with a decent safo for 5kw hybrid???

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1 minute ago, gabriel said:

mine was 5 days and on arrival back home i got a 4% midpoint deviation as 'coming home present' - :( - the almost "set and forget option" [safo] will not only suit me, but especially my wife, but the, at what cost? who can come up with a decent safo for 5kw hybrid???

You watch Gumtree like a hawk, ask the brand you want installers / suppliers to keep a lookout for 2nd hand parts, with more than 1 year warranty, so that you can purchase, over time, a "plug and forget" option.

But, be warned. It is a rather huge effort that can lead to excessive "spending" towards the end ... to get the damn project finished. :D

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1 minute ago, gabriel said:

i think there is confusion, my no 4 battery is as indicated

Whether the chicken crossed the road or the road crossed the chicken depends on your frame of reference.

Batteries at the end for some odd reason tend to degrade faster. I think it is simply because they have a an extra cold face on one side, while the others are often blanketed in on both sides.

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2 minutes ago, plonkster said:

Whether the chicken crossed the road or the road crossed the chicken depends on your frame of reference.

as you say, its neither here nor there; but how can i do the above lamp test with my multimeter?

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1 minute ago, gabriel said:

lamp test with my multimeter?

You can combine the DMM with a lamp, but you can't do it without a lamp or some kind of 12V appliance. The idea is to suck some energy off the high battery, or if you think in terms of current flow, to make the electrons go through the lamp instead of through the battery.

So for example, if you had 20A going through there and you put a 60W lamp on one battery (or about 5A at 12V), then the other 3 batteries get 20A passing through them, but this one only gets 15A (because the lamp bypasses 5). If that lowers the battery voltage, but the balancer could not, then it probably means the balancer is not working, for presumably it is also capable of passing 5A.

The idea is to rule out the possibility that the balancer is working flat-out and still not managing.

You can put your DMM on the higest current range (10A or 20A for most of them, plug the probes into the right sockets too as it is often different) and put this in series with the lamp so you can see how much current is being bypassed by the lamp.

Most passive balancers use a big resistor. Using an automative lamp is just a cheap way of obtaining such a "resistor" :-)

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On 2018/06/15 at 3:38 PM, gabriel said:

everything seems to be under control,

'seems' being the main concept here... things are still more or less as reported at the top of the thread. at around 82% soc and under moderate load midpoint goes to 4.5%. as soon as i change to utility it drops to below 0.4%. i will get the stuff i need to implement @plonkster's test this morning. in the meantime three images i took as the alarm was still shrieking <_<

 

sss.JPG

aaa.JPG

zzz.JPG

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2 hours ago, gabriel said:

seems' being the main concept here

When your earlier post came up on the weekend, I thought to myself... this isn't going to last, there is no reason to expect the deviation to go away. But I figured I'll let you enjoy the weekend.

I had a deviation quite similar to that on a set of lead acids that is now on the neighbouring farm to @Chris Hobson (I assume they are still going in some shape or form). I managed to fix them. All it took was giving them a full charge every day... and I mean FULL the way only a Multi does it, held at absorption for as long as it takes for the deviation to go away.

It was very interesting how they behaved. The one battery would be high... and if you just held it there it would slowly drift to the middle, and then swing the other way, with the other battery being high. Eventually it settled in the middle and my midpoint issue was fixed. Shortly afterwards I sold those batteries. I only asked for scrap value, so I certainly didn't do anyone in... :-)

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5 minutes ago, plonkster said:

But I figured I'll let you enjoy the weekend.

thanks @plonkster, very considerate of you <_<

now i don't have much equipment for that kind of an operation, i.e. giving the batteries a good charge, so what would i need, or could i use the axpert and just change settings for a while, and then which ones...

as for giving the batteries a good charge, that makes sense to me, at least they will then all get a 'hiding' and that might have a good influence discipline wise :)

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1 minute ago, gabriel said:

change settings for a while

Move the float voltage up, if possible set it to the same as absorption level, or just 0.2V down if you want. Charge the batteries and watch the tail current, I think you said you had 150Ah AGMs? I did this with 200Ah AGMs and I charged them until the tail current came down to about 0.5%.

Essentially it's an equalisation charge, but without the high voltage, just spread out over more time.

You also really need to figure out why the balancer isn't preventing this, you need to do the lamp test. An automotive lamp with two clamps so you can move it between batteries, that is all you need. And a volt meter.

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