Off Grid Solar Power need to keep Generac Standby Generator Battery Charged so it will start

You are correct, you do need to float charge the generator battery bank for off grid usage if you do not have a "permanent" AC power connection (utilty, or possibly your AC solar system).

The simplest is to just get a small solar panel and charge controller to float the battery bank. If you know the current required by the generator control system--That would be helpful... Otherwise, running a minimum of 1% to 2% rate of charge to the generator battery should be enough. For example, if you have a smaller 50 AH 12 volt battery:

• 50 AH battery * 0.02 rate of charge * 17.5 volts solar Panel Vmp * 1/0.77 panel and controller derating = ~23 Watt panel nominal

And a 2 amp minimum rated solar charge controller should be good enough (unless the control panel is taking more than a minimal amount of current--Which would require a larger solar panel+charge controller--And you would need to calculate the daily discharge/load).

If you have lightning in the area--Then you would need to be very careful about ground bonding your solar panel frame/racking to a ground rod with 6 AWG cable, and add (not cheap) good quality surge suppressors too--You don't want to bring lightning into your backup genset.

-Bill

From my understanding, when you have distribute power (and loads) such as a genset in another building, a well pump 50 feet away from the house, etc., for lightning control, you should put a ground rod next to each installation with a minimum of 6 AWG cable (or you can use the "real" lightning braided cables") to direct lightning to the ground and not let it find its own way else where.

And for electrical safety, I highly suggest that each distributed ground rod all be connected together with 6 AWG minimum cable--This is to to provide a better green wire safety ground (i.e., 120/240 VAC safety grounds all connected together--Just driving random ground rods do not conduct enough 120/240 VAC current to trip your 15+ Amp breakers in your AC panels).

Lightning will only follow 6 AWG cables for 10-20 feet or so, before they find a different path. And things like right angle bends (vs large diameter bends) also can cause lightning to leap to a different path.

Do not put your ground rod in the middle of the building (for example). Lightning wants to go "outwards" towards the walls and wiring/plumbing in walls naturally (lightning is not DC or 60 Hz power, it is a radio frequency event and follows a more complex set of rules for impedance vs pure DC resistance rules.

Providing ground rods next to the "remote" devices shunts the lightning directly into the earth. Surge Suppressors at the major sources (genset output, main AC panel, and DC suppressors on solar power into the building, etc.) all help. 

https://www.solar-electric.com/search/?q=midnite+surge

For float charging the genset battery bank--Keeping the system small and simple vs going large with 200 Watts is not useful for a small genset battery float charger. And if you have lightning damage--A small system is easier/cheaper to repair or replace.

With AC safety grounding (such as green wire/white wire bonding in the main breaker panel, or other location)--You want a single point of bonding. With lightning ground bonding, you want multiple points shunted to ground (especially if power usage/generation is spread out around the property).

No protection will withstand a direct lightning strike. You will have repairs. But keeping people safe, and mitigating damage from nearby strikes all helps.

Here are some links to lightning discussions:

https://forum.solar-electric.com/discussion/comment/84242#Comment_84242

-Bill

BobbyD,

Yes, as Dave asked, start your own thread/discussion. It will make it a lot easier to discuss your questions/hardware/etc. and not confuse it with the original poster's discussion.

-Bill "moderator" B.