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Old 08-27-2024, 12:14 PM   #1
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best way to recharge house battery while camping

What's the best way to recharge your house batteries while dry camping for several days?

Really just need batteries topped off for the Isotherm 85 Refrigerator 3 cu ft. Either the solar panel or the batteries aren't cutting it and we drop down below 12 volts after 1 night.

I have a pair of DieHard Marine Battery: 31M Group Size ran in parallel, separated from the start batteries by a Blue Sea 7622.

Recharging options:
1) Honda 2000 Generator -> SMB installed breaker panel -> Blue sea 7622 ML-ACR Automatic Charging Relay
2) 100 watt solar panel -> blue sky engery solar boost 3000i
3) Jackery solar briefcase -> Jackery 1000 power bank -> NOCO Genius G7200 UltraSafe Battery Charger
4) idle the 6.0 powerstroke

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Old 08-27-2024, 01:05 PM   #2
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Jacko, are you thinking you are just trying to pull too much, and need more battery reserves? Do the batteries have caps to maintain the water or are they sealed AGM type?



Before going wild, you might want to load test the batteries and make sure all the connections are good. If you have wet cell marine type batteries that are going south, the charge current using a automotive charger often won't lower to an amp or so after charging for a long period. Sometimes the battery will get unusually warm during the charge. They usually require monitoring the cell water, but I've seen a few AGM marine batteries



Charge currents with AGM type batteries often make it to an amp or so, and a bad battery might appear fully charged, but just doesn't last as long as when new.



If your batteries are good and you have a generator, a 10 amp marine charger would be a good choice, but a 100 watt panel is more of a maintenance supply to keep a full battery full when the load is minimal. A small panel will help offset what is drained out but generally would struggle to supply enough to keep the battery full depending on your daily loads.


Personally I'd avoid using a briefcase charger to charge your house batteries...I'd install the correct size house batteries.
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Old 08-27-2024, 01:16 PM   #3
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I would add solar or use the 2k Genny. We have 200W of solar but add a cloudy day or heavy use and we go below my preferred 50% discharge. I'll then hookup my Honda 2K and top off.
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Old 08-27-2024, 10:07 PM   #4
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This is our exact situation for our current build. A 12v refrigerator draws enough to need a big system for boondocking. We are planning 460 A-Hrs of lithium battery to get us through 3 to 5 days offgrid. Then 50 to 100 amps of alternator charger. Idle if needed but we have a gasser.
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Old 08-27-2024, 10:30 PM   #5
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How do you figure how much battery you need?
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Old 08-28-2024, 10:29 AM   #6
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Quote:
Originally Posted by Ocsmb View Post
How do you figure how much battery you need?
You need to determine the current draw for all your loads, how long they will run each day, add them together and you get amp hours needed per day. Try not to discharge more than 50% of your battery's capacity for the longest battery life. Solar panel output is effective only when you have sunshine, so if you live in Arizona, you can get by with a smaller solar array, but if you live where there are lots more cloudy days, you need more. I have 300 watts of solar that will run all my loads (the refer, lights, chargers etc) 24 /7 when there is enough sun, but when it's cloudy a lot, they won't keep up. If parked for several days, I have a Honda generator Try this calculator:

https://remispowersystems.com/2023/1...our-equipment/
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Old 08-28-2024, 11:15 AM   #7
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I get 2-3 days out of a 100Ah Renogy Lithium running primarily a fridge and a maxxair fan.

Best course of action may be to load check your batteries and make sure your fridge has adequate airflow so it will cool down properly, Two batteries should give you 3-4 days easily if thats all your primary loads are.

For charging I really like the Renogy DC-DC charger, high amp alternator and lithium batteries. The advantage is that it can charge at 50 amps, so if you have 200Ah worth of battiers you can charge them from completely flat in 4 hours and top them up in 20-30 mins of runtime max.

If you have good solar potential, 100 watts of solar is enough to barely keep up with a fridge, 200 watts of solar is enough to run a fridge indefinitely as long as you get some decent solar potential every other day or so.
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Old 08-28-2024, 02:28 PM   #8
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we run 220w of solar but we live in SoCal so charge levels are not a problem. we try to limit the draw to the fridge only, so little charging of devices at night, very limited running of the inverter and for lighting we use solar charging Goal Zero lanterns that hang from the ceiling. its way cheaper to conserve draw than shell out $2k for batteries, $2k for 2nd alternators. We are going to put in a Redarc Manager 30 when we flip over to our 2025 spending budget. DC/DC is a big winner
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Old 08-28-2024, 02:31 PM   #9
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we also have a Moose Jaw cooler between the front seats, replenished every couple days with party ice, for Tecates, vino and packaged foods
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Old 08-28-2024, 03:32 PM   #10
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We are going to put in a Redarc Manager 30
"The Manager30 is a state-of-the-art battery management system designed to charge and maintain auxiliary batteries by incorporating AC, DC and solar inputs."

I've asked about this a few times before. In this day and age it seems fundamental - get rid of all the eclectic, over-engineered battery management stuff and have one "elegant" box do it all. They should all work like this, at 1/10th the price. I'm not an electrical engineer, but I don't understand what is so difficult about this.
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