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MPPT 75/15 charging 2 batteries

i have a mppt 75/15 smart solar charge controller.

can i use it for charging two batteries at the same time or it works only for one?

how should i connect them to do so?

what are pros and cons?

in case i can't i have to buy another mppt and connect it to the battery, but then how can i switch the PV energy for the two mppt controller?


pietro-ceciarini asked
kevgermany answered ·

1 Answer

Multiplus II 5kVA 48V random output voltage dips

I fairly recently installed a Multiplus II 5kVa 48 system (including Venus GX), connected to 2 x Hubble AM-2 5.5kHw lithium batteries. System runs as purely backup system for load shedding purposes.

This issue that has arisen is that the inverter randomly cuts the output voltage to the loads for a couple of second.

The latest instance happened after a blackout (load shedding). The system took

over and returned seamlessly, and roughly a hour after, the output voltage dipped for a couple of seconds.

-Inverter and GX has latest firmware installed

-System is not overloaded

-AES is not enabled

-Battery bank is CAN bus connected to the GX, via its own logging device (Cloudlink\Riot)

I have checked settings multiple times, and compared to other installations.

Has anybody had similar problem, or have advice as to remedy?



botessj asked
nickdb commented ·

5 Answers

Dyness batteries: be very careful!!!

Last February 2022 we bought three Dyness B3 battery modules to make up a solar system with two Victron Multiplus working in parallel. We managed to set up the system correctly with the info received from Dyness and it was working OK. After some weeks of use, we realised that the battery bank was too little for the inverting power capability of the multipluses, and we decided to buy two extra B3 battery modules.

The new modules were bought June'22 and tested. There started the problems: when connected together with the original modules it was obvious that something was not working well, we started to receive communication alarms from the batteries. We had the impression the modules were not communicating properly through the CAN bus. We asked Dyness technical staff and for our big surprise they told us, after asking for the S/N of each module, that the three first modules and the two second modules WERE NOT COMPATIBLE!!! They updated the product (new current specs, new BMS...) and did not even change the name of the model. Incredible.

From the outside the modules looked slightly different, we noticed it upon reception. Not big differences, the only obvious is that new model has an RJ "COM" connector in the frontal panel, to the left of the two CAN bus connectors. All the rest is basically the same.

I have been working in the electronics & telecom industry for more than twenty years and I never saw such a compatibility break from any label. Even more having in mind that battery modules are designed to work together.... The Dyness staff did not accept to give us a solution, just told us we had to go back to the dealer. Well, I have done so but our dealer says they can not change my modules by the compatible model without Dyness approval, and Dyness is not responding their messages. So now we ended up with two modules for a value around 2300€ that we can not use... Maybe we will get some solution from our seller but this is still very uncertain. What is crystal clear is that Dyness is not properly responding to the problems they cause to customers because of their poor development policy, to say it in a polite way.

So a word of warning for all seafarers: be very careful buying Dyness B3 modules from different sellers or at different times: it is not said that they will be compatible!!!
Regarding our company, for sure we will avoid putting ourselves again in the hands of this label.

rrofes asked

0 Answers

Is my solar panel sufficient for my power consumption?



Would you be able to tell me if my solar panel yield is suitable based on the consumption readings? Am I correct to assume today I consumed the exact amount of power my solar panel yielded? It is summer here in Australia I am just worried about winter.

My battery is 9Ah LifePo4 and my solar panel is 50W.

Kind regards!

samuil asked
albert commented ·

2 Answers

Incorrect battery temperature displayed on VRM


Pylontech batteries sitting at 15c degrees on ccgx,however the VRM is indicating -273 c degrees!


Mark asked
hominidae answered ·

3 Answers

12v UPS battery display only unit with phoenix and multiplus range

Hi All,

I'm looking for a solution where one can add a basic display only unit on a 12v battery connected to a phoenix or multiplus inverter/charger

hdp asked

0 Answers

Suitable Circuit breaker between multiplus-ii and battery

Hello everyone,

I want to put a double pole MCB between a MultiPlus-II 48/3000/35-32 and 3 48V Pylontech batteries.

Pylontech recommends 25A for each Package and it supports up to 100A of discharge for each Package.

Victron states in manual:

-You must have the minimum number of battery modules to supply the inverters startup inrush surge currents that charge the capacitors when the inverter is first connected, this occurs prior to any loads being connected. For this Inverter, 2 Batteries are minimum.

-Victron recommends a 125A MCB between battery and Inverter, since its Peak power is 5500Watt (3000 AC Load + 1500 feeding in shore power)

We dont want to feed in the shore power, so only ac loads left. 3000 W / 48 V = 62,5 A. So an 80A MCB should be fine, but maybe the Inverter wants to pull more current? Maybe the stated 125A due to the startup inrush current?

I found 3 MCBs (80A, 100A, 125A) from the same series from ABB

I really would like to use an 80Amp MCB, so that the Inverter does not pull much more than the calculated 62,5 Amps.

My Questions:

Do you think the 80Amp MCB will "handle" the startup inrush current?

Does the MCB could have a minimum operating Voltage(Datasheet not found)? Is 48V fine?

Is the rated Ultimate Short-Circuit Breaking Capacity (Icu):(800 V DC) 5 kA enough for a 7,2kWh battery system?

If you have remommendations for other MCBs, please share.

Cansin Sari asked
londonflatthing commented ·

5 Answers

Battery Alarms

I had installed three months ago solar panels together with VICTRON multiplus 48/5000/70 inverter, MPPT 250 70 TR, Lynx Distibutor, and 2 Leoch LFeli 48100 batteries.
I receive usual during the night but also during the day 2 or 3 battery alarms advising me of low battery levels which would appear to rectify itself quite quickly. The SOC is set at 30%

The installer advises me that this is quite normal! But I remain sceptical as if alarm is triggered it must be for some reason and must be a possibility of rectifying. Any help or guidance I can be given would be gratefully received.

cmh asked
kevgermany edited ·

1 Answer

Using a 100/50 SmartSolar controller with no battery

I have a greenhouse. I'd like to use solar panels, a 100/50 SmartSolar controller and batteries to run fans in the summer and circulate air. In the winter, I do not use the fans, but I'd like to run 12v from the panels to simple 12v heaters (200w) in water tanks in the greenhouse. I do not care about running the heaters at night, or on cloudy days. Would it damage the SmartSolar controller if I ran it in the winter with batteries disconnected? Power would go directly from the SmartSolar controller to the 12v heating coils in the water tanks when the sun is shining and be inactive when it is not. I have three 200w panels that are 12v.

portsample asked
portsample edited ·

1 Answer

Energy Smart Battery Sense with Cerbo GX ?
good morning

i have two Energy Smart Battery Sense, and now i have installed a cerbo gx, but it can't see them? is there a way to make the two smart monitors talk to the cerbo gx? the two smart ones create the network and send the data to the bmv 712 smart and to the smartsolar controller so they talk to the network ..... thanks

sciallinoemilio asked
klim8skeptic answered ·

1 Answer

Enabling nighttime export from DC-coupled battery inverter to grid (in addition to daytime export from AC-coupled PV inverter)

I have had a simple grid-tied 5kW PV system for some years.

I have recently added 3 x RedFlow ZBM2 batteries, which means a total of 30kWh, but an available usable 20kWh at any instant (allowing for maintenance strip cycle of these batteries).

I want to reserve 4kWh for my own grid-failure backup use, and export the additional 16kWh to the grid each night. I have rooftop capacity for charging the batteries.

Once the system is configured to export this additional 16kWh to the grid each night, I will know how many more batteries to install, with the ultimate goal of exporting 5kW (1Ø household limit) to the grid constantly, day and night.

As far as I can tell, I have had all the necessary hardware installed, including:

  • MultiPlus-II GX 48|5000|70 battery inverter;
  • SmartSolar MPPT 250|100 MC4 VE.Can charge controller (for the DC-coupled PV array I added); and
  • The associated accessory hardware.

So far, the system is working correctly, charging the batteries, and providing backup power for the house, but the additional grid export is not happening yet, and I'll make the system available to the utility for FCAS once I've sorted the export out. I have not yet seen any additional grid export at all - my usual daily averages of 35kWh production / 21kWh consumption have continued unchanged.

Any suggestions for getting the additional export from the batteries happening?

el-gallo-azul asked
jameshoare1964 commented ·

2 Answers

Victron Lead Acid Batteries - Failure ?

All Victron batteries must have a manufacturing error after a lot of test and research on around 300 batteries from Victron mainly super cycle 25AH over 250 and 18 batteries Gel Deep Cycle 220Ah.

Most of the super cycle they fail within 6 months to 1 year even if you have them on float voltage and not cycling them, if cycling them on a solar system best you can get is 6 months. 30% got a catastrophic effect of swelling. Other manufacture of batteries with 4 year floating still there and running without a problem the only difference is that is 18Ah instead of 25Ah.

After 1year of using them new ones with serial numbers came out thinking they fixed the problem but at the end they all failed from 25Ah day one measured with a proper load tester they all end up at 3Ah the ones that are always on float voltage , the ones doing cycles are 100% dead. It was a big loss for us and there is no support or guaranty from our local dealer since they are not replying to our calls. They tried at the beginning to help but that didn't help since there is no response.

The 220Ah at a controlled environment at 25-30 degrees Celsius 70% state of charge as a discharge they get a half capacity if not less on some of them after 1 year.

After 1 year and 2 months it was failing cause of some of the cells in series of the 4 was actually close to 50Ah and some on 119Ah on 2 strings parallel of 4 in series.

All batteries show a good voltage like a new graph but with the difference of the capacity instead of 220Ah there new capacity 120Ah or 50Ah, on the small ones 25Ah when new but after 6 months to 1 year 3Ah if not swelling.

Note that internal resistance was measured but it can’t be trusted since it was showing good on a lot of cases but the capacity was not there, most test where done with C20 and C10 when new even C2 was good.

Hope this 2 year test and research on Victron batteries will help.

What is your experience with the Victron Lead Acid Batteries?

Alexandros asked
Alexandros edited ·

0 Answers

Victron + Pylontech setting - understanding


a company is designed a whole system for me and I would like to check/understand whether it is ok or not.

The setting they are going to install in my house:

  • 3x Multiplus II 48V/3000
  • 1x MPPT 150/100
  • 12x Sunpro 450Wp
  • GX monitoring (I expect Cerbo GX)
  • 3x Pylontech US3000C

I've read many articles on the internet, countless topics in this forum and facebook community and I'm still not sure how to understand some things (I'm not an electrician :) ), so I'd like to ask you for a help/explanation or just confirming that I understand it correctly or not.

From the Victron calculator I know that the MPPT with those panels will provide max 100 A.

1. Baterry + MPPT

Each US3000C can be charged by 37A - 3x US300A in parallel can be charge by 111 A total. 100 A < 110 A - so it is OK. And even if I add another MPPT (when I add another panels in future) and the current will be higher then 111 A, the inside BMS connected to GX will manage the current and it still wont be a problem. Is that correct?

2. Battery + Multiplus

This is where I get a bit confused. I've read (for example) this thread

and this article

and I'm not sure, whether the 3x US300C is enough or not. According to datasheet, the bartery can provide 48V*37A = 1776 W (3 batteries 5328 W). So if I have 3x multiplus, where each has 2400 W, the batteries cannot provide sufficient power if there is a 100% load. So I would need at least 4 (better 5) batteries for 100% power. Is that correct? Or am I missing something?

Thanks a lot for any explanation.


jakudo asked
jakudo commented ·

3 Answers

Is it possible to turn off battery function on Multiplus-II?

I have installed Multiplus-II 48/5000/70 in a three phase setup while I’m awaiting the delivery of the batteries. Now the AC out turns off and on periodically and I believe it’s because there’s no battery connected.

andreas-ziegenfeldt asked
Alexandra commented ·

1 Answer

Ideas for alerting on voltage difference between parallel batteries?

I have a setup with two 12V batteries. They are normally paralleled, but each has its own breaker and battery fuse. They are LiFePO4 with internal BMS.

What I am looking to do is monitor the terminal voltage of both, and generate an alert if there's a significant difference. That could happen if there is significant current flow and either battery's breaker has tripped, fuse has blown, or BMS has disconnected it.

It seems the midpoint voltage monitoring of things like the BMV-712 is almost what I want, except that it expects the midpoint voltage to be 6V for a 12V system. It doesn't appear that there's any way to configure it to expect two 12V voltages instead of 6 and 12.

Is there any product in the Victron ecosystem that does what I'm looking for?

tk-421 asked
kevgermany answered ·

2 Answers

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