pilotfish

Nope, the battery is a commercial unit with bms, inside a steel box with cells firmly secured, with a circuit breaker that is turned off so that the terminals on the front are dead - off course if you dragged it from JHB to Durbs behind your vehicle then there might be some problems.

...and apologies for the spelling mistake in the title

Hi all Durbanites, I have a client in JHB who is moving to Durban in the new year. I recently (before lockdown) installed an Axpert VP5 and Narada 48v 100Ah LiFePO4 battery as grid backup (no PV), last week I stripped the equipment out as he will be taking it with him down to Durb's. He has asked me if I can recommend anyone in Durban to re-install, which I cant so I am asking you! Anyone that has had a happy experience with a grid backup installation - preferably involving Axpert inverter - please send me a PM with the installer details that I can pass on to my client. Thanks for taking the time.

I think it is time for you to do that again and let us know!

MPPT#1 will be a WRND 48v/30amp and MPPT#2 will be a WRND 12v/40amp. I have used a couple of WRND units in the field for charge only applications (no inverter requirements) and have had no comeback issues - I was able to order with conformal coating and adjust voltages to suit my lithium charge profile which swayed my decision to go with these units (and they are pretty cost effective which didnt hurt either).

To simplify the above - ask your supplier what your 95% SOC voltage is (or check your battery literature), set bulk and float both to this voltage.

Try lowering your bulk and float voltages on the batteries (speak to your supplier!). So what is probably happening is the following; Your float bulk/float voltage is at max, triggering the BMS to block any further charge current, You have a high inverter load being carried by the PV panels, The load then drops (eg kettle shuts off), The MPPT takes a moment to respond to the lower load requirement and would normally dump this excess power into the battery bank - but cant P=VI, so with nowhere to send the amps, the voltage must climb Your inverter senses this dangerously high voltage and so shuts down rather than blowing up Then restarts because it is set to do so. If you lower Bulk to about 52V and float to about 51.5V (speak to your supplier!!) you will find that your batteries are still reaching 100% SOC, but are still able to accept the momentary excess power referred to above. Disclaimer - The above works with the batteries I use which is NOT the same as the batteries that you are using - so speak to your supplier!!!

...not without reason tho. The 48v is for the 48v windlass and water-maker, and because it makes a great main battery, The 72v alternator is needed to be able to charge the 48v main battery, The 12v is because all critical systems nav/comm/bilge/etc run on 12v and would cost R100'sK to change, The 24v starter battery is because grunt needed to start the 120hp Perkins, The 220v is for RSA/Europe shore power and charging when available, The 110v is for USA shore power and charging when available. As for "Radio Shack", there is VHF for short range comms, HF/SSB for long range comms and weather, AIS, GPS, Epirb, Radar, Sonar, FM radio and not to forget Wifi - so fair comment I guess

I like to keep my options open You left out 220v from MPPT/Inverter #1, and 110v from MPPT/Inverter #2!!!

Hi All, long time since I have been active on the forum So I have a question for the more electronically enabled minds out there - I need to upgrade the power on a decades old yacht that will be cruising oceans without regular access to shore power. Referring to the attached line diagram you will see that there is 1.15kWp of solar which will charge a 48v 4.8kWh Lithium bank via MPPT (there are 2 heavy loads - a windlass to raise/lower the anchor (1.2kW) and an RO water-maker (1.2kW) - these will both be 48v in order to limit high currents otherwise required). There is also a 72v 60amp alternator which will be connected to the MPPT PV input via a C/O disconnecting PV when the motor is running. Question 1 - any concerns having a 72v automotive alternator as PV input to an MPPT charge controller? Additionally there will be a 12v 2.4kWh lithium bank that is to be charged via a 2nd MPPT with the 48v bank as input source. The 12v bank is for critical loads (navigation, communication, bilge pumps etc), so it will be quite convenient to have the 48v bank as primary source keeping the 12v bank fully topped until the 48v bank fails - the 12v bank therefore acting as a "reserve tank". I see no problem using a the 48v bank as power source for the 2nd MPPT unless anyone is able to advise otherwise. To further complicate matters there is a 24v engine-start bank which can no longer be charged by the engine alternator as this is now 72v! so I would like to charge this bank using another charge controller with the 48v bank as source (only active when ignition switch is on). Question 2 - any issues with connecting the PV input of 2 separate MPPT to a single battery bank. If yes would a PWM charge controller for the 24v bank be an option? Early draft of Line Diagram attached - thanks for looking Bella Luna Power.pdf

Because you are feeding the inverter from an E/L circuit in your grid DB, and you have connected N-E on the outputs which is an earth fault. I hope the attached sketch is legible, my CAD skills are a touch lacking (I can do it but it will take the whole day!)

Take a look at Annex P.4 starting on page 361 of SANS 10412-1:2017 ed2 I sadly cant share this with you because my scanner has recently croaked and I haven't got around to sorting it out, but in summary you should bond your main E terminal (from earth bar in Main DB) to your inverter N terminal (at the inverter) which will prevent your floating voltage situation. The earth conductor should be a minimum of 50% size of the Live conductors. This should be done before the inverter output Earth Leakage which I am sure you have installed. So as an example if you run a 50amp 10mm L/N from the Main DB to your Inverter L/N(in), then you should run at least 6mm from your main E-bar to the inverter body and to the N(out) terminal (looped, not 2 separate wires).

I think something like the following is happening; the PV system is supplying loads and charging batteries, then a high AC load exceeds the inverter happy place causing the system to switch to grid (until the load drops again), the system then dumps the momentary excess PV capacity into the batteries, causing the battery voltage to spike while the MPPT adjusts to the lower requirement. I wouldn't be too concerned until you see smoke.

Replace and carry on - fuses will often blow at lower than rated currents as a result of heat build up from other sources. Make sure your terminals are tight, wire not too thin or annealed, fuse terminal gripping tightly.