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mrusmc53 avatar image
mrusmc53 asked

MPPT Bulk LED failure states insufficient power to start charging. What is solution?

I started with 4 Battle Born 240 AH and a Victron Multiplus II 12V /3000. added 6 - 220Watt solar panels through a combiner box, then a MPPT 150/85 Solar charger. Use a shunt BVM 712 to monitor. I've ordered a Cerbo GX, it will be a week before it gets here. I get a slow blink on the
Bulk LED stating system is powered but there is insufficient power to start the charging. The 5V spread to turn the charger on is working, there is plenty of solar harvest, averaging over 300 Watts all day long. What does insufficient power mean? How do I correct for insufficient power? The second question is the inverter overheats. The positive cable servicing the output of the inverter to the bus bar gets very hot if I am just living off battery, running 1 AC unit, Starlink, laptop, led light, and misc minor electronics. The function of battery only works well, just overheats, I put a coolling fan on the iverter box, but that's not enough,

battery chargingMPPT SmartSolarsolar
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Alexandra avatar image Alexandra ♦ commented ·

Where are you getting the insufficient power message from?

How are the panels combined? 3s 2p or 2s 3p?

If things are getting hot they are either loose, badly crimped or undersized.

3k @12v is 250+ amps so 95mm² cable at least should be there.

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mrusmc53 avatar image mrusmc53 Alexandra ♦ commented ·

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mrusmc53 answered · 4 secs ago

The solar panel are individually wired to a 6 position combiner box. Originally I wired them 3s 2p and thought that was my problem, but that change made no difference. On the solar charger, the Bulk LED flashes once every 3 seconds, the manual on page 11, section 3.10 LED indication. and on hot wire, They are 000. were the ones that were installed originally. the hot set is only from the inverter to the switch, switch to fuse, fuse to buse bar. after the buse bar all cables are just warm as they should be. My batteries will support my RV for over 8 hours. The installation of the solar has made no difference, telling me I'm not charging, and I cannot figure out what is causing that. I will recheck my cable crimping, sizing, and connections......again!!! ugh Thank you for your help,

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1716911320840.png (789 B)
kevgermany avatar image kevgermany ♦♦ mrusmc53 commented ·
A screen print of the first screen of the charger from Victron Connect would help a lot.
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Alexandra avatar image Alexandra ♦ mrusmc53 commented ·
Are you sure the panels are wired ok? Checked each string separately with a meter?

The next thing is usually programming and firmware.

Sometimes the battery voltage on initial start up detects incorrectly then won't charge.

If you haven't programmed the solar and updated it then that may be the problem. As far as i am aware the rotary position 7 doesn't match the battle born requirements.

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mrusmc53 avatar image mrusmc53 Alexandra ♦ commented ·
clicked on the link to battle born, made adjustments to programing. Here's to hope tomorrow when the sun comes back, again thank you
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mrusmc53 avatar image mrusmc53 Alexandra ♦ commented ·
double checked fittings and connections today, found the master disconnect where all the heat was coming from had a loose post on the back side. I was following the heat per your suggestion.. solved the hot wire issue.

on the solar panels, yes I checked each panel ... each reads voltage with the sun. the combiner box, registers voltage, the MPPT registers solar voltage and power.

Solar voltage 14V up to 18V with 90 to 300 plus watts

IN programming settings, to battery 12V max charge 85A, charger enabled, battery preset to Smart Lithium (LiFePo4). Absorbtion 14.2, Float 13.5,

Firmware checked update was automatic

Rotary switch is set to 7. If that's right, what is? or where do I find answer?


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pwfarnell avatar image pwfarnell mrusmc53 commented ·
The panel voltage has to get 5V higher than the battery voltage before it will start charging. With lithium at say 13V, you need 18V to start charging but once started the panels need to stay 1V higher. With all your panels in parallel the voltage is low and barely enough to start charging so will take a long time before they start charging. Put 2 or 3 panels in series so the voltage is higher and start up will be much better.
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Michelle Konzack avatar image Michelle Konzack mrusmc53 commented ·

If you have 6 x 220Wp of solar panels, I suggest you to make two strings of 3 in series. and put both in parallel.


This will increase the power output from autumn to spring and also reduce the current on the wires, hence the losses


I assume, the solar panels have around 36Vmpp, mean roughly 6A each. this is 36A in total and depending on the cable lenght, you would need at least 6mm2 (or better 10mm2 or 16mm2).


And with a 3000VA invrerter on 12V, I would not install lesser then 2x50mm2 (better 2x70mm2) for the POSITIVE and NEGATIVE.


With a 12V System and this power, you have enormous losses

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mrusmc53 avatar image mrusmc53 Michelle Konzack commented ·
correctly wired a series parallel .... my electrical experience is with house electricity and a series circuit is almost non existent, so now I have 2 series circuits with 3 panels on each, huge difference!! My harvest is up to nearly 900 watts with voltage nearing 40 volts at 2:30 in the afternoon. with that said, if the system is resting, (5amps consumption, lights, chargers, gas refer) then I can see a 1% increase in capacity in 10 min. Not the plan.... I should be able to increase at a faster rate, plus the panels should handle my normal load of around 150A of consumption with an A/C unit on, minor lessers. or near that....

I have found lose connections.... a buse bar post at the bar, my main battery cut off post, on the back side was lose. I had a broken terminal in the combiner box. all new stuff with factory mistakes. SMH I have spent the day reviewilng and double checking every wire, every connection. All wire sizing is correct. new parts installed to replace broken, Now the question is how do I increase my harvest to overtake my consumption or get near it? What I have is not what I'm supposed to have


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delf67 avatar image delf67 mrusmc53 commented ·
150A @ 12V is 1800W consumption. 6x 220W = 1320W panels under perfect conditions (which you will almost never get). I don't see how you think generation is going to cover consumption?
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mrusmc53 avatar image mrusmc53 delf67 commented ·
How do I increase my harvest to overtake my consumption or get near it. was my question. What you are showing me is I need 1800 Watts of panels or add 2 more panels for 8 times 220 for 1760.... "near it". With my set up, it will take me all day of sitting, using nothing to recharge my batteries. 1% gain in 10 min equals 10% gain every 100 min ... 8 hours of great sun would only give me 480 min ... 48% recharge. with minimal usage. .... so 2 more panels? is my math right?
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delf67 avatar image delf67 mrusmc53 commented ·
More panels, yes. But your MPPT only has a maximum charge current of 85A (approx 1190W @14V), so if your load is 150A then you will need at least 1 more 85A MPPT and 6 panels. And that will still only be charging your batteries at a maximum of 20A.
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mrusmc53 avatar image mrusmc53 delf67 commented ·
I can put at least 3 more panels on my roof. If I understand you correctly, I would put the 3 new series wired panels on a new combiner box, wire to a new MPPT 150/85 VE. Can, daisy chain the MPPT's, then tap into the system bus bar like the first MPPT.

This would be better than just adding another 3 panels in series to the existing combiner box, ?


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delf67 avatar image delf67 mrusmc53 commented ·
Yes, that would definitely be better.

Can you post the specifications of your panels (voltages/ currents etc)?

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mrusmc53 avatar image mrusmc53 delf67 commented ·

Newpowa 220S-12J

  • Dimension: 56.69*30.12*1.38 inches
  • Weight: 26.62lbs
  • Max Power Output(W): 220W
  • Voltage MPP Vmp(V): 17.52V
  • Current MPP Imp(A): 12.60A
  • Voltage Open Circuit Voc(V): 20.52V
  • Short Circuit Current Isc(A): 13.41A
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Alexandra avatar image Alexandra ♦ mrusmc53 commented ·
@MrUSMC53

85Amps (mppt max amps) x 12v is 1020W. That is the max yield your charger will give you at 12v in good sun. (@13v 1105w and 14v 1190w)


6x 220W is 1320W. So you have maxed out the charger (unless you have poor light/irradiance conditions)

Change your panel config, check your polarity and see what the app is saying.

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Alexandra avatar image Alexandra ♦ Alexandra ♦ commented ·
You have 4 x 240AH of battery that is 960AH or 11kWh of battery. If you fully discharge that bank, it will take you nearly 2 days full sun with not loads running.

I do second the opinion that you need more solar, but get a second charge controller for it as well.


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mrusmc53 avatar image mrusmc53 Alexandra ♦ commented ·
currently have my panels in 2 series strings, (3 panels)+(3panels) should I change that to 1 string, then in the future, when I add more panels, put them on a second series string? I appreciate all the suggestions and help that Has come through this community.
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delf67 avatar image delf67 mrusmc53 commented ·

If you only have room for 9 panels, then the best arrangement to give the most power would be 2 MPPTs one with 5 panels in series and one with 4.

You will still struggle to supply a 150A load and keep the batteries charged too.

Personally, I would start with trying to work out your required consumption over 24hrs and work backwards from that. If your aircon is going to be running much when the sun isn't shining, you will need lots more panels than 9 to recharge once the sun's back out.

You have good battery capacity but need the means to get charge into it faster than you are taking it out!

I know it's probably too late now, but choosing to run a 12V system means you are limiting the power handling capacity of your MPPTs (the same unit could handle double the power at 24V or 4x @ 48V), you're also increasing losses in the system due to high currents/ volt drop etc.

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mrusmc53 avatar image mrusmc53 delf67 commented ·
It will be awhile before my wallet heals from this so I can add more panels and another MPPT, But that makes sense based on what I have and can do. The next RV we'll go 24V. hindsight is 20/20. I have found a way to lower my load requirements down to 100, but realistically 120 is more to what my needs are.

The Cerbo GX will be here in a few more days, I asked Alexandra and I'll ask you as well, would all 6 panels in series be better for now, and then in the future, split the panels into 2 series strings as you suggested?

you have been of great help and what I have is working well as can be expected do to all your recommendations as well as others in this community, Thank you for the help

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