Charging Batteries with a Small Generator

[SCHawk]

We seem to always have issues with keeping our batteries charged in our 2015 Hawk. Sometimes we've ended up spending the night in an unwholesome RV park just to be able to plug into shore power. The truck's contribution seems to be quite slight so we're relying primarily on the solar panels (160 w on the roof and an 80 w portable). The portable unit doesn't get used often because we are usually hiking during the day and won't leave it out. I am planning to mount it permanently on the roof before our next trip, which should help. I am considering buying a small generator to keep the batteries in shape so that we can avoid the necessity of occasional shore power altogether. I'm wondering if anyone here has any experience doing this with one of the smallest generators like the Honda EU1000i. I'd rather not carry anything larger than that (I'm not even sure where I'd keep it since we seem to have already filled every available space both in the camper and the truck). Any alternate suggestions would also be welcome.

 

[Wandering Sagebrush]

The Honda/Yamaha 1000s will work, but something sounds off. Assuming you’re getting decent sun, your 160 watt panel (plus the 80 watt portable) should be able to keep up unless you’re using a lot of power, or your batteries are compromised. If you have a compressor refrigerator, does it run a lot? Furnace?

 

[rando]

Plenty (most?) folks here seem to do well charging their batteries with solar and/or the truck. I am one of those folks and do just fine with a 160W roof panel and very occasionally a 120w folding portable panel. I am wondering if you either have particularly high energy usage, or there is something amiss with your solar system?

Either way, a generator for charging batteries (lead acid in particular) will be an exercise in frustration, both for you and your neighbors. Because the amount of current your battery accepts decreases as it closer to full, it will take a minimum of a few hours to get your bank full with a generator, even though it can provide a lot of amps. Do you really want to listen to a generator for hours?

First I would figure out what is going on with your current system and fix any issues. Do you have a battery monitor? Second I would consider adding more solar. Third, if you drive for a few hours per day, you could consider a DC-DC charger from your trucks alternator. This could give you 30-40A of charge current and get your battery full in a few hours.

 

[SCHawk]

Thanks for the replies. The batteries are the second set of AGMs, installed by FWC in Woodland who assured me the charging system was working just fine. They also said that I should plug into shore power every week or ten days to keep the batteries in shape.This was less than two years ago. I don't believe our power usage is anything extraordinary--the compressor refrigerator uses the most by far. As I mentioned we rarely get to use the portable solar panel due to hiking a lot. I perhaps should add that our trips are two to three months at a time. This past spring we were out of two months, six weeks of which were in Death Valley. It rained and was overcast quite a bit so the solar wasn't doing all it could. I have no desire for a generator but I really don't like worrying all the time about getting the gauge to 12.6. I'm not familiar with the DC-DC charger rando mentioned; I'll have to look into that. If there's a flaw in the system that FWC didn't find I guess I need to educate myself a lot to see if I can track it down. I spent 50 years in the trades but electrical was not one of them. I am familiar with the magic smoke however.

 

[JaSAn]

To answer your question: Yes, a 1000W inverter/generator will charge your batteries. I camp under heavy forest canopy a lot so my solar is not always able to keep my batteries full. In less than an hour in the morning I can get my batteries to 80% with a 35 amp, 3 stage charger. Even in shade or overcast (but not both) my solar (200W) will usually finish the job.

For low light conditions you need to supplement, either with alternator charging if you drive a lot or a generator/battery charger if you park for a while.

I would highly recommend a amp counting battery monitor (I have a Trimetric). You can learn a lot about your system by watching amps in - amps out.

 

[rando]

Two things to consider before the generator:

1. A good battery monitor: https://shop.pkys.com/Victron-Energy-BMV-712-Smart-Precision-Battery-Monitor.html
This will tell you what the state of your battery really is - judging by voltage alone is fairly hit and miss.

2. A DC-DC charger - this will give you 30A of charge from your alternator: https://shop.pkys.com/orion-tr-smart-non-isolated-12-12-30

Start with number 1 to see what the situation really is and this will help you identify any possible issues. Number 2 will only help if you drive regularly. If you spend a lot of time in one spot then a second solar panel may be a better option particularly if you have the roof lifter struts. Two solar panels get a bit heavy.

 

[ntsqd]

A link to the TriMetric battery monitor that JaSAn mentioned: http://www.bogartengineering.com/products/battery-monitor.html

We too have 160W of solar and have yet to have a problem with the new to us camper. Our previous camper had only 100W of solar and that kept the batteries up w/o much effort. So my first reaction was that same as Sage and Rando's, there's something not performing up to snuff in the system.

 

[JHanson]

I agree with the above comments—something seems off. We had 200 watts worth of PV panels on our FWC, and that kept up effortlessly with the fridge, lighting, and running/charging two laptops and camera equipment. You need to determine how much amperage you are getting from your panels, and whether or not it is getting to your batteries in full measure.

 

[Vic Harder]

rando mentioned a DC-DC charger. Renogy makes one, Redarc and others too. They address the issue that (just like your solar panel) the voltage/current of your alternator may not be what your batteries want. They also address the low voltage that most modern fuel saving trucks put out, and the skimpy/skinny wiring that the campers come with, AND the usually lousy battery separator they are equipped with.

NONE of the above solutions will be "enough" if you don't have a good battery monitor. A voltage gauge is not a battery monitor. A good one comes with a "shunt" and measures all the dis/charging that happens to your battery, regardless of the source. It's really the only way to know the SOC of your battery.

 

[JHanson]

SCHawk, I forgot to mention: Getting the batteries to "12.6" volts, as you mentioned, is not nearly enough. Twelve-volt batteries should really be brought to a float voltage of 13.5 every day to ensure long life.

 

[SCHawk]

Again, thanks for the all the information. I see the path ahead now and for the moment it doesn't include a generator. What it does include is mounting the 80w portable panel on the roof (I've emailed FWC to see if they'll sell me the extrusion they used on the panel already there) and installing one of the battery monitors that have been mentioned. I should then be able to tell if what I've got is a. adequate b. working properly.
We are trying to figure out how to make our next trip without exposing ourselves to the coronavirus. Or I should say minimizing the chances of exposure. But that's another topic; I hope to see it addressed here.

 

[Wandering Sagebrush]

Before you do that, check your solar system connections for corrosion. In particular, the roof connector(s).

 

[Jack]

Defiantly check your connections. FWC sells a replacement roof connector and it is an easy install once you get to it (under the panel?). Caulk it with Siliprene or one of the other recommended caulks.

Your Charge Controller (Zamp, for example) should show you how much current is coming in from the solar panel. If you don't have current, or very little, you have a wiring or panel problem. Unlikely, but if the wiring from the Charge Controller to the battery is open or faulty, you would also see no current.

In good sunlight, you should see somewhere around 100 W or better from the panels. Multiply voltage and current to compare. If your Charge Controller does not display current and voltage but you can get to one of the wires coming into it from the panels (under the sink or under the bench?), you can use a DMM with a DC current clamp to measure current.