Different voltage readings

[monzer]

How well synced are Victrons MPPT and smart shunt.

I've new solar panels on and trying to make sense of readings. I think they seem to be working okay but I notice a difference between battery readings between the 2 devices.

Is that normal? I also noticed my SOC jumped up from 95% too 100% in the space of a few minutes. Is something needing tweeked?

 

[Lenny HB]

Looks like it may have changed from absorbtion to float while you were looking at the readings..
The percentage readings are never that accurate without a lot of tweaking, I tend to work from current used much more accurate.

Raul is the man.

 

[monzer]

Looks like it may have changed from absorbtion to float while you were looking at the readings..
The percentage readings are never that accurate without a lot of tweaking, I tend to work from current used much more accurate.

Raul is the man.

It's still saying it's in absorption mode but shunts saying SOC is 100%. Battery voltages still a bit out of sync too.

I'll keep an eye on it for a bit yet.

I remember you mentioned you tweeked your set up to get it more accurate. Is it something a newbie would manage? Or is it quite technical?

 

[Lenny HB]

I remember you mentioned you tweeked your set up to get it more accurate. Is it something a newbie would manage? Or is it quite technical?

Easy enough to do it just takes a few days of trial and error.
What batteries have you got?
Post a pic of the battery settings on the smart shunt.

 

[monzer]

2 X 90's Victron gel

Set up like this at the moment...

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[Raul]

The shunt went from 95% to 100% because it met it’s parameters to re sync, and it synced to 100% Soc prematurely. If the battery still absorbs, it’s not full but close. You need to find the shunt settings and adjust them in line with your charger settings, otherwise is pointless guesstimates.

 

[Raul]

2 X 90's Victron gel

Set up like this at the moment...

View attachment 637710

There’s your problems:
Charged voltage 13,2v way to low, when this voltage is reached, it tells shunt it’s full.
Tail current 4% to big, when curent drops below 7,2a it tells shunt it’s full. So shunt it gets told lies.
Adjust charged voltage to float voltage set on charger
Adjust tail current to the smallest you can get in there like 0,5%
Adjust detection time to 15mins. This gives 15 mins when all parameters are met to re sync. If it doesn’t even better, work on coulom count Ah amorphous in out, it’s dead accurate.

 

[Lenny HB]

I learn a bit more about my BMV every time Raul posts.

In addition to Raul's setting, try these settings:
Charged voltage 14.2
Discharge floor 25%
Charge efficiency factor 80%
If your batteries are new you could lower the Peukert Exponent to 1.1

 

[Raul]

I learn a bit more about my BMV every time Raul posts.

In addition to Raul's setting, try these settings:
Charged voltage 14.2
Discharge floor 25%
Charge efficiency factor 80%
If your batteries are new you could lower the Peukert Exponent to 1.1

With one mention: no lead can be so efficient in charging discharging without big voltage difference. Example when you absorb 14,4 and discharge from full 12,7 it’s a 1,7v difference for the same amps on same battery. The difference is resistance so on charging you pushing 14,4w to get the 12,7w back. That’s the efficiency and peukert calcs the shunt will do. The bigger the difference the bigger the peukert value has to be to calculate corect. So, for the 1.1 peukert it’s well suited for LiFePo4 not lead. The LiFePo4 voltage difference is much smaller 0,7-0,8v. Lead starts at about 1,25 and up. I actually have my peukert on lead at 1,4 worked it up from 1,3, and for few years stayed there. Round trip real efficiency is around 75%.

 

[monzer]

Thanks Raul and Lenny HB top stuff as always.

No idea about my charger I have no reason to believe it's not standard hymer 2002 but don't know its settings so will I just go for 14.2 for charged voltage?

Batteries must be about 5 months old regarding the peukert.

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[Lenny HB]

With one mention: no lead can be so efficient in charging discharging without big voltage difference. Example when you absorb 14,4 and discharge from full 12,7 it’s a 1,7v difference for the same amps on same battery. The difference is resistance so on charging you pushing 14,4w to get the 12,7w back. That’s the efficiency and peukert calcs the shunt will do. The bigger the difference the bigger the peukert value has to be to calculate corect. So, for the 1.1 peukert it’s well suited for LiFePo4 not lead. The LiFePo4 voltage difference is much smaller 0,7-0,8v. Lead starts at about 1,25 and up. I actually have my peukert on lead at 1,4 worked it up from 1,3, and for few years stayed there. Round trip real efficiency is around 75%.

I thought Gels when new were far better than wet lead and 1.1 was the correct setting, I have mine set to 1.25 but my batteries are a few years old so it looks like I should increase it a bit.

 

[Lenny HB]

No idea about my charger I have no reason to believe it's not standard hymer 2002 but don't know its settings so will I just go for 14.2 for charged voltage?

The older Elektroblocks were 14.3 but I would set it for the setting on your Solar as if you have plenty of solar that will be doing most of the charging.
Just checked the Victron solar is 14.3, so 14.3 would be ideal.

 

[monzer]

Done.

Now, any ideas for tidying up some pretty hefty 2-1 connectors with cabling on the roof?

 

[Lenny HB]

Done.

Now, any ideas for tidying up some pretty hefty 2-1 connectors with cabling on the roof?

I take it they are MC4 connectors, mine are ticked under the panels a hole drilled in the frame so they can be held out of the way with a cable tie.
All cables in mini trunking, don't use the self-adhesive use the standard fixed with PU adhesive.

 

[monzer]

I take it they are MC4 connectors, mine are ticked under the panels a hole drilled in the frame so they can be held out of the way with a cable tie.
All cables in mini trunking, don't use the self-adhesive use the standard fixed with PU adhesive.

I've probably not chosen the best way to connect my 2 panels but the way I've done it, they need to meet in the middle to have enough reach to go in to connectors so I can't tuck them underneath a panel. The panels are not next to each other.

I really needed the furthest away panel to have about 1.5m of cabling instead of the 400 odd it came with.

Might have to see about modifying it as it looks pretty messy up there.

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[monzer]

I take it they are MC4 connectors, mine are ticked under the panels a hole drilled in the frame so they can be held out of the way with a cable tie.
All cables in mini trunking, don't use the self-adhesive use the standard fixed with PU adhesive.

I've probably not chosen the best way to connect my 2 panels but the way I've done it, they need to meet in the middle to have enough reach to go in to connectors so I can't tuck them underneath a panel. The panels are not next to each other.

I really needed the furthest away panel to have about 1.5m of cabling instead of the 400 odd it came with.

Might have to see about modifying it as it looks pretty messy up there.

Any issues with having one panel with an extension on making the cable a couple meters longer than the other panel before going in to 2-1 connectors?

 

[Raul]

Any issues with having one panel with an extension on making the cable a couple meters longer than the other panel before going in to 2-1 connectors?

No issues, nothing to worry, crack on.

 

[monzer]

So I think I've still a bit of tweeking to do.

My shunt app will show the battery at 96 or 97% but even with solar going in, it doesn't seem to rise any further.

I also drove from Edinburgh to Aberdeen last night, a journey that usually charges the battery to full and it was still showing 96%.

So I presume the battery is full but something in the victron shunt settings is a bit off?

This is my settings...

 

[Lenny HB]

I would discharge them to about 80% then recharge them making sure they are fully charged best to do it on mains for 24 hours so you get a proper absorption phase, then do a manual sync. Do this a few times then see how it goes.

 

[monzer]

I would discharge them to about 80% then recharge them making sure they are fully charged best to do it on mains for 24 hours so you get a proper absorption phase, then do a manual sync. Do this a few times then see how it goes.

Took them down to 79% yesterday and plugged in after work. That's them been charging for 24 hours now so going to do the sync. What does the manual sync consist of? Will it be self explanatory on the Victron BT app?

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[Pausim]

Took them down to 79% yesterday and plugged in after work. That's them been charging for 24 hours now so going to do the sync. What does the manual sync consist of? Will it be self explanatory on the Victron BT app?

On my Victron App it is under battery settings.

 

[monzer]

On my Victron App it is under battery settings.View attachment 646015

Yeah just wanted to check it's just a case of pressing that button. I wasn't sure if there was anything else involved before I went playing about with it.

Vans in the garage for the day so I'll maybe get a look at it tonight.

 

[Raul]

So I think I've still a bit of tweeking to do.

My shunt app will show the battery at 96 or 97% but even with solar going in, it doesn't seem to rise any further.

I also drove from Edinburgh to Aberdeen last night, a journey that usually charges the battery to full and it was still showing 96%.

So I presume the battery is full but something in the victron shunt settings is a bit off?

This is my settings...

View attachment 643179

Just seen this, try bringing the charged voltage from 14,3 to 14,2v. Maybe your charger leads losing a 0,1v.

 

[Aucheorn]

Help please, I bought a Topsolar 100w solar panel kit, and ordered 3 more panels to make a 400w system. I fitted the kit and am pleased with it. It's connected to 2 x 110 amphour batteries and a 1500w inverter.
I received an email that the 3 panels would be delivered on the 24th July, fine.
BUT, on phoning to check the delivery, I found out the order was cancelled and my money refunded. On further digging I discovered that Topsolar (Senhosuneu) had cancelled the order, BTW they didn't tell me this at the time. Apparently they can't or won't deliver panels to the UK only kits.

At last my question, can I fit 3 Renogy 100w panels to this Topsolar kit to complete my installation. Or do I have replace the Topsolar kit completely?

 

[RogerIvy]

We sell loads of these things (and LifePO4 batteries) and TBH you'll drive yourself crazy trying to fully understand all the little differences.

As long as there are not massive differences just learn to live with it.

For example:
On a recent trip I was comparing the info provided by:

1. The BMS (Daly Smart 200A BMS)
2. Votronic 3-way charger
3. Viktron smartshunt
4. Juntek smartshunt

(I have the two shunts connected one after the other)
If I wanted them all to exactly agree I'd be in an OCD Loony bin by now.
Pretty much a case of choosing which version of the truth you want and to go with it.

Just FYI: the Viktron smartshunt counts up the AH in/out and usually gets to say you have 100% SOC when you're not quite there yet - that's not a problem as long as you understand the reasons why. The BMS tells a slightly better truth. The Juntek is not far off.

All in all there is usually a valid explanation for the differences.

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[Raul]

We sell loads of these things (and LifePO4 batteries) and TBH you'll drive yourself crazy trying to fully understand all the little differences.

As long as there are not massive differences just learn to live with it.

For example:
On a recent trip I was comparing the info provided by:

1. The BMS (Daly Smart 200A BMS)
2. Votronic 3-way charger
3. Viktron smartshunt
4. Juntek smartshunt

(I have the two shunts connected one after the other)
If I wanted them all to exactly agree I'd be in an OCD Loony bin by now.
Pretty much a case of choosing which version of the truth you want and to go with it.

Just FYI: the Viktron smartshunt counts up the AH in/out and usually gets to say you have 100% SOC when you're not quite there yet - that's not a problem as long as you understand the reasons why. The BMS tells a slightly better truth. The Juntek is not far off.

All in all there is usually a valid explanation for the differences.

The victron shunt stops the ah count and resets to 100% if the re sync it’s triggered by the set values. We try to adjust those settings, to prevent premature triggering of re sync. If you know what they mean, you can actually adjust those values to never trigger it. Just rely on true coulomb count and sod the percentage estimate. A bms does not take in consideration of peukert, and amps resolution it’s not that brilliant, making those miliamps draw undetectable. Victron shunt goes down to 50 miliamps and at 12v will register load of less than 1w. If bms can’t pick up 1w load, with time it will drift away from real SOC.

 

[monzer]

I think I'm right in saying that the different phases of charging kick in at set voltages.

Why is my solar just in float mode when my battery is at 90%?

Okay it's not dangerously low but Ive been out pretty much all afternoon in brilliant sun and SOC has hardly budged. To be honest I thought it would have topped it right up to 100%.

Why is it sticking in float mode?

 

[monzer]

This is my solar with battery SOC at 91% still....

 

[Lenny HB]

Your battery is probably at 20% and its your BMV settings that are giving a false reading.