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Solar Question :::

Surviver76
Explorer
Explorer
I'm in Oregon and stretching out my time here but my 90ah agm batt is not getting enough sun and starting to get lower and lower. Considering a generator but my question is this. If I just add another similar house batt, that would make it so I could go longer between sunny days. Am I thinking correctly on this? Thanks in advance..
13 REPLIES 13

Surviver76
Explorer
Explorer
Thanks guys, that clears this issue up for me...

valhalla360
Nomad
Nomad
First issue: What do you use per day and how many days do you go between being hooked up to shore power?

If you have a 90a-h battery, that gives you about 45a-h usable assuming 100% charge on a good battery to start.

If you use 20a-h per day, that gives you a little over 2 days.

A second battery of the same size will give you a total of 90a-h of usable power or about 4.5 day but at the end of 4.5 days, you need a way to supply 90a-h. (ideally batteries should be replaced as a unit but if the current one is in good shape, you can probably get away with it)

If your trips are normally 3-4 days and you can plug in when you get home, it's completely viable given the numbers above but you need to get your own numbers.

If you are actually using 40a-h per day on 4 day trips with minimal solar input, you will need another way to charge.

If it's only rarely, consider just up-sizing the truck charging wires and running the truck motor. Not a good option if you need to run the truck 50days/year but if it's 2-3 times per year for a couple hours, it's not going to do any great harm and the extra fuel used is insignificant.

Really best to approach off grid energy systematically:
- How much do I use?
- How much generation do I need?
- If not practical to 100% generate every day, how many days between generation do I expect the battery to carry over?

From there the calculations are fairly simple but it can be iterative if the expectations are not realistic.
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jplante4
Explorer
Explorer
Rigging the panels so you can tilt them towards the available sun will help. I saw a YouTube video of a rig that used jack screws connected to motors.
Jerry & Jeanne
1996 Safari Sahara 3530 - 'White Tiger'
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time2roll
Explorer II
Explorer II
Two batteries will give more time between sun but will also take more time to catch up.

Two+ batteries and 300+ watts solar is what I recommend.

Sandia_Man
Explorer II
Explorer II
Although ideally batteries should be of the same age, type, and size category, adding a second battery will certainly give you more 12 volt DC reserves to depend on. Biggest issue is they will charge and discharge at different rates, if all you are looking to achieve is getting extended service between adequate solar recharging, you could expect an extra day or two of service.

To achieve the 100 percent success rate desire we use a multi-pronged solution when using our rig off the power grid. Since it is our preferred method of RVing our 120Vac and 12Vdc power requirements must be stable and reliable for indefinite periods of time. Of paramount importance when restoring consumed amphours via generator is the converter's ability to smart charge battery bank

BFL13
Explorer II
Explorer II
What's the plan? Oregon is not Arizona as you may have noticed when it comes to cloudy skies. ๐Ÿ™‚ How long do you need to go off-grid before being able to plug in somewhere?

Will an extra battery get you to the next plug in time or not?

Generally, you should always have a gen ready to go to cover for cloudy days with solar. An extra battery would be good too, so you can go longer without having to drag out the gen.

At some point with little solar coming in (ie for the next six months) you will need the gen, no matter how many solar panels you have, if you intend to keep camping off- grid in the "darker months."
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mike-s
Explorer
Explorer
It's a leaky bucket. To keep water in the bucket you either have to add water faster (more panels, hope for better weather, a generator, or use your vehicle to charge), or have a bigger bucket (more battery capacity).

Lwiddis
Explorer
Explorer
"The convenience and safety margin is better this way."

Not the convenience, Darsben. The "convenience" of solar panels is me doing nothing. Sun shining and panels working on my roof....without noise or gasoline.
Winnebago 2101DS TT & 2022 Chevy Silverado 1500 LTZ Z71, WindyNation 300 watt solar-Lossigy 200 AH Lithium battery. Prefer boondocking, USFS, COE, BLM, NPS, TVA, state camps. Bicyclist. 14 yr. Army -11B40 then 11A - (MOS 1542 & 1560) IOBC & IOAC grad

darsben1
Explorer
Explorer
I would go with a small genny for backup. The convenience and safety margin is better this way. Should your batteries die in the boonies a little genny with a battery charger will get you on the road again.
Even a harbor freight 2 cycle with a harbor freight battery charger would fill the bill Some will say the genny is to loud but as it only a just in case and not a normal 4-6 hour a day thing it would be fine. If you are truly boon docking it is just another layer of safety
Traveling with my best friend, my wife in a 1990 Southwind

2oldman
Explorer
Explorer
If you do much boondocking you'll need more battery and solar to boot. 90ah is pretty tiny.
"If I'm wearing long pants, I'm too far north" - 2oldman

Lwiddis
Explorer
Explorer
Well....batteries can be added when of the same make, age and AH rating. Yes, if you double your stored AHs and if you draw the same amount of energy as when you had one, your two batteries will be less discharged and last longer...but they will require the same amount of energy to recharge as one did. The best answer is more panels. SoCal is one thing, Oregon is another regarding sunlight.
Winnebago 2101DS TT & 2022 Chevy Silverado 1500 LTZ Z71, WindyNation 300 watt solar-Lossigy 200 AH Lithium battery. Prefer boondocking, USFS, COE, BLM, NPS, TVA, state camps. Bicyclist. 14 yr. Army -11B40 then 11A - (MOS 1542 & 1560) IOBC & IOAC grad

MrWizard
Moderator
Moderator
Another battery will extend your time to the same discharge level
Of both batteries
While then requires a longer generator runtime to recharge

Or
have the batteries at a higher level, for the same amount of use

If your not getting enough solar, to recharge one battery, you still need the generator to keep both batteries charged

Another battery will not change the amount of solar you get oto replace the amount you use

More battery capacity will make it better/easier on the batteries and they will have a longer life for the same amount of use

For more charging your need more solar and generator
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fpoole
Explorer
Explorer
Yes.... but...
I have 3 sets of 6v and 480w solar panels...

Right now, in Bend, OR yesterday and today I've had to run the Gen due to clouds/rain etc.

I'm sure others will chime in here, but adding another battery will basically just delay it a little bit...

I would recommend getting a Gen as a backup. Solar won't help much if in trees/snow/clouds etc.. and the extra battery might last another day or two, depending upon your use...

Hope that helps a little..

... and there are some who can probably use a flashlight battery and live off that for a week...
Depends on your usage...

good luck.
Frank Poole
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