Good day all.
Ex Electronic tech (Dip. Cape Tech) here. Is it possible to install an external MPPT on an Axpert Hybrid rebrand. The Internal MPPT went south. The 2nd question is if the AC input will remain connected where it currently is connected? I need to try this out for a friend in need that was retrenceched.
Yes it is and I have done it before. A victron would work as you just set the MPPT charge settings to match those that were on the Axpert MPPT. You can actually use an external and the internal at the same time (I did this) to increase the PV array size. I just set the settings on the external lower than the Axpert to stop them conflicting when the battery got close to full.
Hi Mnr Maritz. Where would I wire the external Victron MPPT in on the 5KW Mercer? The internal Mercer MPPT is apparently Faulty and as of now, I haven’t opened the inverter.
You should connect the battery terminals of the Victron MPPT to the battery through a battery disconnect. The appropriate range of fuse sizes for the disconnect will be specified in the MPPT manual. Ensure that the cables are rated to carry at least the current at which the fuses will blow.
The PV input from the combiner box that is currently connected to the Axpert inverter must be moved over to the PV input of the Victron MPPT.
Important: You need to know upfront what the PV open circuit voltage is, because the maximum PV input voltage of the MPPT that you intend to buy must be greater than this.
Good morning Pierre. Thank you so much for this info. This is a tremendous help. Basically helping a friend in need. It is an existing installation with all electrics in place including EL and OV protection inside the DB. The DC V+ from the PV goes directly to a 30A fuse and then onto the the Mercer PV input at the bottom. But the built-in MPPT is faulty and I would like to wire the Victron into the Output of the Mercer MPPT to the 48V to 220V Ac of the Mercer Inverter. The most +V I could see is Max 150V from the 6X 330W panels.I understand that the installer set the input charge to 20A and the same for the AC output. Thanks once again. You guys are Scholars and Gentlemen.
OK, I will assume it is two strings of 3 panels in series (otherwise the voltage will be way over 200V 
), which then also explains the 30A fuse. It would be better for the two strings to be fused individually… but knowing how people normally install cheaper inverters (cheaply…), it is probably paralleled on the roof.
Basically, all you do is connect the MPPT directly to the battery (through a fuse, ideally, but if there is already a fuse in the system, then to the same point where the inverter connects to the fuse, and if there isn’t a fuse… get a fuse… then connect it like that).
Then the PV that is currently plugged/connected into the Axpert, is simply moved over to the PV terminals of the Victron MPPT. Keep the 30A fuse. Although, ideally, I would still have preferred individual 16A fuses on each string
The Axpert is now essentially just used as an inverter.
Did you measure this with the PV wires still connected to the Mecer inverter? If so, I would recommend you remove the fuse sometime after dark and then re-measure the PV voltage around noon the next day. It’s important to know if the PV open circuit voltage is above or below 150V - if the panels are still connected to the inverter’s (broken) MPPT then it could be interfering with your measurement.
If the open circuit voltage is above 150V then you’re either going to have to get a 250V MPPT (which is significantly more expensive), or you’re going to have to parallel the panels into two groups of three to get under 150V.
Looking at current pricing online, a 150V 35A Victron MPPT is just over R2500 (new). The smallest 250V model is double that. Victron equipment has a reputation for great reliability, so you could try to source a second hand one.
Hi Pierre.
Thank you so much for your time and attention to detail. I am in Windhoek and the installation is on a farm 80km Southwest of Windhoek. The owner is unable to pay R6.60 per Km so I am helping out of kindness. Ideally, when I go there I want to have all my ducks in a row and have all my collateral with me. The MPPT V+ was taken about noon with the fuse removed physically and left in open position. V+ was measured at the top of holder incoming from PV.
I have settled on the 150-35 MPPT as suggested by the supplier and another Installer. Yes that is about what is cost here in WIndhoek at a reputable dealer. Thanks again for your feedback and time.
How close was it to 150V?
In a Namibian summer (I grew up there, mostly in Windhoek itself) the panels will be hot and you’d expect around 135V for three panels in series at noon, but on a cold winter’s day (which I also remember, up at Seeis it gets to -12C at times, and I remember freezing my buttocks off at Koës one day during an Afrikaner cattle auction), that voltage could be significantly higher.
We often have this debate here, but for this area, I would really ask myself seriously if I should be 3 panels series on a 150V controller. To me that sounds like Khomas hoogland area. It gets cold there if I remember correctly (sorry, it’s been 27 years ).
This could even be the reason for the failure of the Axpert MPPT. I recall that the earlier units were limited to 150V.
Just something to check.
If money is tight, that is the one I would go for as well. However, before you put money down I would also check the pricing on the 150/45 in case it is on special. The 150/45 is a newer hardware design, so if the price difference is very small then it would be the better buy.
In either case I would buy the SmartSolar variant (as opposed to BlueSolar). The SmartSolar has bluetooth, so you can configure and monitor it from a cellphone using the VictronConnect app. Configuring the BlueSolar will require a special cable.
When you install the MPPT, connect it to the battery first and configure the battery charge parameters before hooking up the PV. You do not want to accidentally overcharge the battery.
Baie dankie vir die reply. Og my mistake. V+ DC was taken before the Fuse where the feed comes in from the PV’s. fuse removed and pulled open. At the time around noon it was 122V DC. I will recheck when I go there on Saturday to do the retrofit. Komas Hochland gets very very cold and so does Aus, close to Seeis in winter. The farm is located 25Km from the Airport turnoff towards Dordabis (40Km further)
I will physically check if parallel or series. The installer moved away and no longer available to confirm. I moved from CA to SW in 1994. Only went back to CFM for holidays. Am a true Southwester now.
Thanks for your time and suggestions. I truly appreciate it.
Oh… that’s South East. That’s my valley (Nina, a bit further on). Although to get there, the MR51 is a better road. I digress
122V is about what I would expect for three panels series. It should be okay to put that on a 150V controller, especially in that area. It is not quite as cold as the West or the South.
Also still waiting on rain, that area. Some farmers have had rain, others still waiting. Boreholes drying up to the west. One can understand that they don’t have money to throw around.
I was in in Aus in 1989, when I was still a young boy. It gets very very cold. I also saw some strange things there, to this day I am convinced there are old German ghosts walking the desert plains