Adding A Generator to a PV System

Re: Adding A Generator to a PV System

Welcome to the forum Tombsl!

And yes, you can have multiple charging sources with a battery bank. However, there are a few things to watch out for.

First, you should run each set of charging cables back directly to the battery bank/bus bar connections. If you run the AC charger to the output of the solar charge controller, then to the battery bank (daisy chain wiring), the electrical "noise" from the AC charger could confuse the solar charger.

Next, while it is handy to use the battery charger clips to charge the battery bank--You really should hard wire them. The clips generally do not make good long term high current electrical connections. Also, you don't want to be connecting/disconnecting the clips on a high current battery bank (short circuits can be "exciting" to say the least with a large lead acid battery bank).

And, if you permanently attach the charger, you should have a fuse/breaker at the battery bank to protect the charger's wiring (ideally, you should have a fuse/breaker on each positive wire that leaves the battery bank). Fuses/breakers are there to protect the wiring, not protect the loads (in general).

Lastly, picking the size/brand/model of battery charger to connect with the generator.

First, Amp rating. A typical lead acid battery needs around 5% to 13% rate of charge. You can charge upwards of 25% rate of charge--But you need to monitor the battery temperature to prevent over heating/thermal runaway (hot batteries use lower charging voltages--which can confuse a battery charger that does not use a remote battery temperature sensor to reduce charging voltage on a hot battery bank). The "over 13% caution" can be an issue if you charge with the AC charger and Solar Panels at the same time (and no loads on the battery bank). In general, the thermal issue is probably more of an issue if the batteries are "deeply" discharged (less than 75% state of charge to 20% state of charge) when the batteries are subject to hours of >>13% rate of charge. Above 80-90% SOC, the batteries will naturally limit current (if chargers are programmed to the correct voltage).

Lastly, there is the loading on the generator. Ideally, you want the generator loaded to round 50% to 80% of rated load. If too high, your genset may have problems with overheating the alternator. If loads are too low, then you waste fuel (gasoline generators tends to use around 50% fuel flow for 0-50% of rated loads, inverter-generators tend to be a bit more fuel efficient down to the 25% rated load range). Diesels tend to have issues with "wet stack" and cylinder glazing if operated below ~40-60% of rated load (commercial installations will have resistor load banks to properly load diesel gensets).

And, while we usually work with "Watts" to plan loads... With AC loads, you also have to work with Volt*Amps (VA). Watts are:

Watts (power) = Volts * Amps * Power Factor

"Good" AC loads have Power Factor >0.95 or so... "Bad" Power Factor loads can be in the 0.50 to 0.67 range pretty easily (CFL lighting, computer power supplies, AC induction motors, AC battery chargers). While we see generators and inverters generally rated in "Watts"--In reality, most are rated as Watts=VA maximum. So many loads you will connect can "pop the breaker" on your genset even though the watt rating is not exceeded.

So, in the end, yes, you can put a nominal to relatively large AC battery charger on your genset to help recharge the battery bank during poor weather/heavy loads (or if you nave a relatively small solar array).

Question about battery charger selection with EU2000 generator.

Regarding the "optimum" generator to AC battery charger selection--This thread has lots of information (if you are interested in the details and the search)... If not, we don't have to go down that level of detail to answer your questions.

The reasons we ask so many questions about your overall system and usage is that a "balanced" system will usually give you the best results for the minimum amount of money (and money spent on fuel usage).

-Bill