# Continuous battery charger for off-grid Generac generator?



## AuroraMike (Dec 7, 2021)

Hello all!

I have a unique issue. I am using a Generac Guardian 22kw stand-by generator, fueled by propane, as the sole power unit for a mobile office. The generator comes with an internal battery charger but it needs to be tied into grid power to activate. We don't have grid power available so the battery keeps dying and the generator goes with it. I have a trickle charger plugged into an outlet on the mobile office and have it tied into the battery, but it doesn't charge fast enough to keep the battery alive.

Is there some kind of charging unit that I can tie into the generator itself to keep the battery charged?


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## tabora (Sep 6, 2018)

I have a regulated solar panel on the rear platform on my pontoon boat to keep the battery charged. It works to perfection.








I have also been considering one of these Jackery panels for my off-grid cottage:








Jackery SolarSaga 100W Portable Solar Panel for Explorer 240/300/500/1000/1500 | eBay


$Click here to see description.



www.ebay.com


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## Dutchy491 (Sep 18, 2019)

I have a buddy who has a similar issue, albeit a hunt camp. Their solution is to use a lithium booster pack if the generator battery is too low. They’ve also switched the generators battery to a deep cycle which can handle being routinely run down. They always make sure to keep the booster pack charged up, or bring it with them from home ready to use if needed.


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## FlyFisher (Jun 30, 2018)

A couple thoughts:
- If this is an intermittent use set up the only "off grid" method to keep a battery charged, that I know of, is some other form of energy - solar has already been mentioned. This would be the easiest, however it won't work if this is a set up that is exposed to much snow in the winter (solar panels don't work well when covered with snow/ice). You could supplement with a wind turbine also - but that would be more maintenance heavy than solar. 

- You could use a small generator with a booster charger to fire up and give the big gen's battery a boost then charge it. This is my back-up for my truck. I have a Honda EU2200i gen that is my main gen. If the truck batteries quit I have a charger with a 100a starter mode to get some juice back in to the batteries to start. 

I am really curious, though - what does said "mobile office" run that needs such a large generator? We have a 15kw (portable, not built in/standby) for whole house power and even with the whole house AC running we don't use it to its capacity. 

The above brings me to another consideration - if you don't need that much wattage all the time that is a big engine to supply fuel to. If you drop the gen size to a reasonable size you can drop your fuel consumption. Just a thought.


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## OrlyP (Oct 19, 2021)

There’s something inconsistent about the setup. You say that a trickle charger is being used to maintain the battery when the generator isn’t running. Then you also said that the facility isn’t on grid power. So where does the trickle charger get power?

Assuming it’s just a misunderstanding and the trickle charger only works while the generator is running, you probably need a bigger/faster charger. The Generac standby has electronics that are presumably running off of battery to a certain extent which drains it after a while, as you have observed.

I think we need to see a more detailed picture of the whole setup.


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## iowagold (Jan 22, 2020)

AuroraMike said:


> Hello all!
> 
> I have a unique issue. I am using a Generac Guardian 22kw stand-by generator, fueled by propane, as the sole power unit for a mobile office. The generator comes with an internal battery charger but it needs to be tied into grid power to activate. We don't have grid power available so the battery keeps dying and the generator goes with it. I have a trickle charger plugged into an outlet on the mobile office and have it tied into the battery, but it doesn't charge fast enough to keep the battery alive.
> 
> Is there some kind of charging unit that I can tie into the generator itself to keep the battery charged?


what is the exact battery group number off the battery?
also post a pix of the generator tag with model number and serial number.

yes you can add in an relay to charge the battery with the built in battery factory charger.
pm for details.


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## VelvetFoot (Nov 11, 2019)

I think the T1 connection on the generator has to be supplied with 120v to power the charger that is built into the control panel. It's not really meant to bring up a battery that's flat, so I don't know what kind of stress that can put on it.

I think the built in charger is at least 2.5 amps.

I think if you hooked up T1 to the generator output you'd be okay for overnight, but I'm not so sure about over the weekend. Maybe.

For the weekend, the controller consumes power. Maybe removing the 7.5 amp fuse on top would reduce that (I'm thinking about the new model 22 air cooled model I got recently). Or, if that doesn't do it, maybe add an RV battery switch and turn off the battery on the weekend.


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## exmar (Jun 29, 2015)

Definitely need clarification on "mobile office" and being off grid. Around here there are a lot of the whole house generacs and the battery charger is a major issue with them. Usually a separate battery charger/maintainer is left connected allowing the onboard charger to be weak and or fail but still allows unit to start. Also the small battery is often replaced with a larger one even if it means a separate marine battery box to enclose it. The onboard charger operates from utility power and doesn't charge when the unit is running and the small battery only allows the initial start and maybe another couple. In an extended outage, stopping the unit to check oil, etc. and restarting leads to an exhausted battery. The charger/maintainer is connected to a circuit that is powered when the generator is running and from utility power in normal state. Perhaps your answer could be as simple as a larger 12V battery and a NOT trickle charger but something heavy enough to bring the battery up and has "smarts" to act as a maintainer as well. Many posts here on preferred units. I've heard neighbors comment that when their generac battery was dead jumping it from a riding mower or four wheeler. .


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## speedy2019 (Jan 29, 2019)

Im amazed that the generator doesn't automatically charge the battery when its running?


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## 50ShadesOfDirt (Oct 23, 2021)

This is but one of the reasons we abandoned the use of Generac's (used to have an EcoGen, then a Guardian 22kw), and just went with open-frame 12kw gennys (currently Duromax, possibly Westinghouse).

Generacs work great when in a city, installed permanently by an auth'd dealer, and remaining near an auth'd dealer who does the service; you'll need to pony up for the Generac of your choice, and then lots of service calls thereafter (pay now, pay later service model). On top of that, installation is key (has to be done right, or Generac disallows many types of service/repairs), and if installed off-grid (as yours is), the warranty is automatically voided for you.

And of course, it has this requirement to bring a 120v circuit back out to the Generac unit, whereas most other open-frame genny's have a self-charging function. This is an oddity of Generac units, discussed on forums like Ziller (a Generac vendor), at:

Generac Air Cooled Generators - Ziller Forum

All of these are why we no longer utilize Generac's out in the country; it isn't sustainable. If you are going to do them, make sure of installation, warranty, and service models, else you'll be in the self-support business. Generac's last about two years of heavy use in this model, and then you are into serious maintenance/troubleshooting, without access to the field service manual that auth techs carry.

Your "mobile office" scenario is possibly a warranty-buster, but not enough details to know for sure (but if Generac can hang you with it, they will). Not having the 120v circuit sent back to the unit (in an on-grid capacity), is probably a warranty-buster, under the "not installed properly" mantra. If you _are_ capable of self-support, then perhaps no problem ...

To answer the original question, on our guardian 22kw, we just disabled internal battery charging (forum will help with this), and teed off a 120v circuit to drive a smart 10-amp battery charger (NOCO, model Genius 10). After being started by the battery, and genny now running, the charger immediately began topping off the battery; charger remembers its settings, and picks up right where it left off. Rarely did we get sideways with a too-run down battery, using this method. Others have mentioned solar, so any way that you can get power to the circuit for the NOCO unit, your battery will stay topped off.

The forum mentioned above was a great resource to me when we had Generac's running, but there's no getting around the fact that Generac's need a Generac service model.

Hope this helps ...


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## iowagold (Jan 22, 2020)

the other thing to keep in mind is if you start and stop a gen set several times in a day.
that start current has to have time to recharge in the battery....
so plan the charger well for the system.
this is why they use a 120 amp alt on a car system...
some current to run the electronics as well as recharge the battery when in the city on short runs.

we use battery chargers on all of the cars and trucks year round here to make sure they are at top charge when we leave for our runs.
and we get 10 years out of a standard SLA battery with this plan! no kidding!


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