Victron Shunt issues

[sunshine_eggo]

Depends on battery type and manufacturer. 0.1C (10% of Ah in amps) is always safe. Some AGM may be happy at 0.2C and some even at 0.3C.

0.1C of 390Ah = 39A; 39A * 14.4V = 562W
0.2C of 390Ah = 78A; 78A * 14.4V = 1124W

15A max out of a single 360W (and you say MULTIPLE) panel(s) suggests you may be using 24V panels on a cheap PWM controller. PWM controllers work by shorting the panels to the battery. This forces the panel voltage to battery votage and likely cuts the POSSIBLE power output to 50%.

I'm not at all convinced new panels and new MPPT will fix your problem until we find out why you're not getting more than 15A out of your existing setup.

 

[slowbutsure]

I’m having an issue I cannot fathom where it’s going wrong. 6 x 130ah lead acid batteries in paralell to a 1000w inverter. (2.5kw of panels). I am running a small freezer and a fridge. The Victron shunt shows that there are periods where the draw goes from 20 amps to 25, and sometimes to 65 amps. At 65 amps the battery voltage drops to below 12v and the automatic transfer switch is triggered and it switches over to the grid. The batteries then jump back up to over 12.5v immediately. I cannot tell:

1. Are the batteries rubbish and can’t handle short legitimate draws of 64 amps. Short bring less than a minute.

2. Is 65 amps mean there is something going wrong in the system and a very small freezer and fridge couldn’t be drawing that much?

3. Is the inverter too small and malfunctioning some how?

Any thoughts / ideas appreciated.

Thanks,

 

[sunshine_eggo]

I’m having an issue I cannot fathom where it’s going wrong. 6 x 130ah lead acid batteries in paralell to a 1000w inverter. (2.5kw of panels). I am running a small freezer and a fridge. The Victron shunt shows that there are periods where the draw goes from 20 amps to 25, and sometimes to 65 amps. At 65 amps the battery voltage drops to below 12v and the automatic transfer switch is triggered and it switches over to the grid. The batteries then jump back up to over 12.5v immediately. I cannot tell:

1. Are the batteries rubbish and can’t handle short legitimate draws of 64 amps. Short bring less than a minute.

2. Is 65 amps mean there is something going wrong in the system and a very small freezer and fridge couldn’t be drawing that much?

3. Is the inverter too small and malfunctioning some how?

Any thoughts / ideas appreciated.

Thanks,

1. Maybe.

Please provide your absorption and charge voltages.
Please provide pictures of your setup. Most important is the cabling between batteries and the main cables to the inverter.
Using a separate meter, when you see 65A, measure voltage at the battery terminals and at the inverter terminals. Report values.

 

[Jbbonnette]

Hey everyone. I'm using my first Smartshunt on one of my builds. I have Batrium for my big boys that power the house, but now I'm experimenting with smaller batteries for a couple products.

Smartshunt is on a 420AH 12v. I did 4P2S (105AH cells). Everything was working well with capicity tests until I tried some larger loads. ...Not even that large- heat gun with lights, fans. About 1900 watts on my 35 watt inverter. After attempting (and then repeating) the Shunt shuts it down. It appears to be the shunt as it abosoluty crashes- restarting to 0 AH used and 100% SOC.

Thanks,

JB

 

[Jbbonnette]

Disregard. Nailed it. Setting in the BMS. Rookie mistake. Argg...

 

[slowbutsure]

1. Maybe.

Please provide your absorption and charge voltages.
Please provide pictures of your setup. Most important is the cabling between batteries and the main cables to the inverter.
Using a separate meter, when you see 65A, measure voltage at the battery terminals and at the inverter terminals. Report values.

Hi

These are the cables. I have a positive and negative bus bar that each battery is wired to. Then larger cables go to the inverter via the Victron shunt. It’s The shunt as well as the transfer switch that show the batteries going very low (11.4v actually) when the inverter draws 65amps. I’ll do a picture in the morning, I’m in the U.K., currently 4am.

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[sunshine_eggo]

Good morning!

So the 5awg, 50cm cables connecting each battery to the bus bar and then bigger wires to the inverter?

Do you have any fuses/breakers in the line?
Have you quadruple checked that all connections are of high quality and properly torqued?
What are your charger settings?
What are the size of the larger cables?

When a load is applied to a battery, the voltage drops in accordance with the circuit and battery resistance. I'm trying to establish if you have any excessive circuit resistance, and if you're actually fully charging your batteries.

65A seems a little high even if both devices are running. Do you have a kill-a-watt or similar smart plug that can show you power consumption of each device?

Assuming your battery internal resistance is 10mΩ, you would see a 0.65V drop in voltage @ 65A. Given that the resting voltage of lead-acid is around 12.6-12.7V, you don't have a lot of margin for 12V switchover anyway.

12V may be too high for the transfer switch. Can it be lowered? Even with a small 2A load, my system can drop to 12V overnight, but it still at about 70-80% SoC

 

[slowbutsure]

Good morning!

So the 5awg, 50cm cables connecting each battery to the bus bar and then bigger wires to the inverter?

Do you have any fuses/breakers in the line?
Have you quadruple checked that all connections are of high quality and properly torqued?
What are your charger settings?
What are the size of the larger cables?

When a load is applied to a battery, the voltage drops in accordance with the circuit and battery resistance. I'm trying to establish if you have any excessive circuit resistance, and if you're actually fully charging your batteries.

65A seems a little high even if both devices are running. Do you have a kill-a-watt or similar smart plug that can show you power consumption of each device?

Assuming your battery internal resistance is 10mΩ, you would see a 0.65V drop in voltage @ 65A. Given that the resting voltage of lead-acid is around 12.6-12.7V, you don't have a lot of margin for 12V switchover anyway.

12V may be too high for the transfer switch. Can it be lowered? Even with a small 2A load, my system can drop to 12V overnight, but it still at about 70-80% SoC

That’s interesting that your batteries can drop to 12v over night while being 80% soc. mine still say 90% soc. I set the switch to 11.6v but still switched over at that.

I have 100amp fuses between the bus bar and each battery and a 100amp fuse going to the inverter. I’m not sure what size the two cables to the inverter are but probably twice as thick as the ones on the batteries. All the connections are tight and have washers but they are steel not brass. The batteries are new but they were quite cheap, £75 each. Though it’s currently only drawing 3.4 amps and sitting at 12.5v. the 60+ amps must just be when a motor firing up to do some cooling but it doesn’t last long.

One other thing, the set up is in my shed and I have an extension lead going to the appliances which is about 20m long in total.

Thanks for your help.

 

[sunshine_eggo]

That’s interesting that your batteries can drop to 12v over night while being 80% soc. mine still say 90% soc.

Mine is a long slow draw. You're is a hammer-hit. Different situations.

I set the switch to 11.6v but still switched over at that.

Still probably too high. I would set it 1.2 - 1.4V below the the rebound voltage. Yes, that's too low for safe discharge cut-off, but this is a different situation.

I have 100amp fuses between the bus bar and each battery and a 100amp fuse going to the inverter.

That's LOTS of fuses. Fuses work in part like resistors. See if any of them are getting warm at 65A.

I’m not sure what size the two cables to the inverter are but probably twice as thick as the ones on the batteries. All the connections are tight and have washers but they are steel not brass.

Steel washer is fine as long as it's not in the current path:

The batteries are new but they were quite cheap, £75 each.

"inexpensive" might be a factor.

One other thing, the set up is in my shed and I have an extension lead going to the appliances which is about 20m long in total.

230VAC, 20m, 6.5A, 14awg will have less than 1% voltage drop, so unless the plugs themselves are corroded, I wouldn't expect that to be an issue.

 

[slowbutsure]

This is what it looks like. Absorption = 14.3, float = 13.38.

 

[sunshine_eggo]

Do you have another MPPT? 2.5kW of panels is going to need, 2500/14.3 = 175A of charging. I only see 70A of MPPT meaning you're unable to utilize more than 1/3 of your array. If you've over-paneled due to a reluctant sun, that's fine.

Fuses go on (+). I'd remove the fuses at the bus bar completely and see if it makes a difference.

I'm seeing lug to post adapters... you're sure that absolutely every single nut and terminal is fully secure?

Your leisure batteries are also 130Ah at C100. C20 is a more common rating. Actual C20 capacity is closer to 117Ah. Your batteries are likely limited to about 72A depending on rating.

 

[slowbutsure]

Do you have another MPPT? 2.5kW of panels is going to need, 2500/14.3 = 175A of charging. I only see 70A of MPPT meaning you're unable to utilize more than 1/3 of your array. If you've over-paneled due to a reluctant sun, that's fine.

Fuses go on (+). I'd remove the fuses at the bus bar completely and see if it makes a difference.

I'm seeing lug to post adapters... you're sure that absolutely every single nut and terminal is fully secure?

Your leisure batteries are also 130Ah at C100. C20 is a more common rating. Actual C20 capacity is closer to 117Ah. Your batteries are likely limited to about 72A depending on rating.

Thanks. Yeah I have an input capacity for the charge controllers of 70 amps (2 controllers) I have over panelled as you say, due to British weather. In the winter I’m still not sure it will be enough!

On the fuses, I’ve read that when in paralell it’s best to fuse each battery. I’ll take them out and see if it improves at all. Interesting about the batteries. Frustrating for a newbie thinking you are buying 130ah batteries when they are probably half that. Being lead acid and only 50% of the charge being usable it brings overall usable capacity to about 250ah. Not much for 6 batteries.

The connections are tight but I do need to check about the placement of washers etc. I’ll take it all apart today and remake them.

 

[slowbutsure]

I think the issue is the batteries. The eBay seller I bought them from said I could return them and pay the difference to get Gel ‘Solar’ batteries. Can anyone tell me if Gel leisure batteries are better than normal sealed led acid leisure batteries? Is it still the case you can only use 50% of the charge? Is there any benefit for drawing higher currents? These are the batteries I’m being offered:

12V 130AH AGM/GEL Deep Cycle Leisure Battery, MOTORHOME, BOAT, SOLAR | eBay

Dual Purpose Deep Cycle Battery. Maintenance-free GEL battery. Leisure & Marine Battery. Part Number: SLG130. General Information Length: 353 mm.

www.ebay.co.uk