A really basic electric question.

DougWW · June 2022

Okay, I'm working with a 2020 T@B 320S Boondock with a solar panel from the factory. I'm still using the original 70ah wet battery.

I'm finding that the solar from factory is enough to support the fridge on a low setting in Spring and early summer. Later in the year, or in shaded locations the fridge will pull that battery down below 12v over night. This should surprise no one here, I'm sure.

I'm considering buying an inverter generator to supplement the electricity and allow the occasional microwave use while boon docking. The models I've been looking at are: Energizer EZV2200P or the Champion 1600W / 2000W Inverter Generator.

This is all well and good BUT...

1. If my battery is down 50% (or to 12v) and I plug in the inverter generator to the trailer, how long will it take to charge the battery back up? An hour? Two hours? 10?

2. Is there a better way? Should I be plugging a battery charger into the inverter generator and boosting the battery directly?

Any thoughts on this are appreciated. We are just looking at keeping the fridge running and enough power to run the tap now and again. When day length is limited we aren''t at that level right now. I know a change of battery is probably warranted, but one small step at a time.

Thanks for your help.

...Doug

Tabnero · June 2022

buy a bigger better battery. Lithium from Battleborn is in my 2021 rig. It keeps up with the refrigerator usage. when I need to replenish it faster, I plug in additonal 100 watt portable solar panel.

Grumpy_G · June 2022

Addressing the questions:

1. I did some testing with an amp clamp and after the first couple of minutes the charge current into the battery drops to 10 amps at best. So you're looking at 2 hours+ to get maybe 20 Ah into the battery.

2. Using a battery charger directly would only be better if it is a high end shop/commercial charger that can charge at 20 A or 40 A. The ubiquitous auto store charger is not any better than the converter.

MuttonChops · June 2022

A}    I like the comments from @Grumpy_G

B}    If my rig, would not run-off to purchase Lithium Batteries but would consider going to a
       larger AHr AGM battery.

C}    I'd also look at adding a portable solar panel to increase your solar input . .

D}    Also, consider turning Fridge off after midnight and save a few cooling cycles and AHrs

Of course all the above is 100% WAG - - - with zero data to support it.

manyman297 · June 2022

I agree with what has been said. Unless you’re really using your camper A LOT lithium requires a lot of investment for not much gain for weekend warriors. Now if you’re on the road for weeks then that’s a different story.

You could upgrade to a higher amp hour AGM for not much money and then supplement that with a portable solar panel. That would also give you some flexibility (if you’re under a tree, etc).

I’m not sure how big of a battery you can fit in your 320 but if you could get 200AH somehow you’d be more than set.

WayneW · June 2022

Your decision depends on your electrical needs. If, into the future, you want 110 power to run the microwave while boondocking, the generator is the way to go. And plugging directly into the trailer would work just fine.

A 20a charger would speed things up. Based on @Grumpy_G’s numbers, it would take about 3.5 hours to fully recover a 50% depleted 70ah battery with the trailer charger. A 20a charger would cut that in half - but you don’t have 110 power to the trailer to run the microwave if you’re hooked directly to the battery

You could go this route and see how it works for you. As far as eventually upgrading the battery, I’d go to lithium because of the ability to use more of the rated capacity. And the weight savings is significant as is the expected battery life.

We upgraded to a 100ah lithium battery and have the rooftop solar and a 100w solar suitcase. We mostly boondock. That meets our needs and we’re very happy with the setup.

manyman297 · June 2022

I’d also add that nowadays with lithium and AGM batteries giving more AHs and solar being relatively cheap, there’s really no need to rely on an inverter generator solely to top off batteries unless you find yourself in extremely cloud conditions for a few days. We carry the generator only when we know we want to run the air conditioning. But the longest we’ve been boondocked is only 3 days and then we’re hitched up and the TV is charging the camper.

rfuss928 · June 2022

Off grid battery based electrical systems are generally designed around batteries being cycled between about 50 and 80 percent capacity (lead acid chemistry). This is because the bulk charging rates allow fast recovery of capacity during times of power availability (generator, solar, wind...). The low charging rates during absorption or saturation charging take prohibitive amounts of time and make it impractical to "top off" battery storage with time limited sources. The multistage charging protocols that achieve 100% SOC are a luxury of grid connected systems. Lithium based chemistry allows a wider percent working capacity but still requires a low-slow final charging stage to reach 100% SOC.
Design your system and set your expectations accordingly when camping off grid.
Have fun...
Bob

SLJ · June 2022

I switched to a larger 100 AH AGM (faster charging) and added a portable 200 watt solar panel to go along with my existing 105 watt roof panel. Better and more cost effective to upgrade your current system than adding a costly inverter/generator made for tailgating.

Denny16 · June 2022

Manyman said, I’m not sure how big of a battery you can fit in your 320 but if you could get 200AH somehow you’d be more than set.

I do not think a 200AH AGM batrery is going to fit in the front tub, and even if it did, this size AGM weighs 200lbs and would increase your tongue weight past the 10-15 percent, of the trailers gross weight, recommended for the tongue weight. A 100AH battery on the TaB320 will be more than enough for 3-4 days of camping, and with solar, you shouldn’t even drop below 50% of charge level.
Cheers

DougWW · June 2022

Tabnero said:

buy a bigger better battery. Lithium from Battleborn is in my 2021 rig. It keeps up with the refrigerator usage. when I need to replenish it faster, I plug in additonal 100 watt portable solar panel.

Thanks for the thoughts. Plugging in an additional 100 watt solar panel that doesn't supply enough power is exactly what I'm trying to avoid. Maybe if we lived in AZ?

DougWW · June 2022

@Denny16 said "I do not think a 200AH AGM batrery is going to fit in the front tub, and even if it did, this size AGM weighs 200lbs and would increase your tongue weight past the 10-15 percent, of the trailers gross weight, recommended for the tongue weight. A 100AH battery on the TaB320 will be more than enough for 3-4 days of camping, and with solar, you shouldn’t even drop below 50% of charge level."

Some excellent points. I'm going to look into the larger battery. Thanks

DougWW · June 2022

Thanks to @Grumpy_G for a very detailed and specific answer. @WayneW added some clarity as well. Much appreciated.

We're going to do some early season camping and contemplate the power issue before we buy new hardware.

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A really basic electric question.

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