best way to recharge house battery while camping

[Ocsmb]

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

 

[daveb-SMB]

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.

 

[Oogs]

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.

 

[dhally]

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.

 

[Ocsmb]

How do you figure how much battery you need?

 

[arctictraveller]

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/...he-right-battery-capacity-for-your-equipment/

 

[Big_ern_101]

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.

 

[Beaky]

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

 

[Beaky]

we also have a Moose Jaw cooler between the front seats, replenished every couple days with party ice, for Tecates, vino and packaged foods

 

[N147JK]

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.

 

[Big_ern_101]

The Redarc is really awesome. By the time you piece out a Victron or Renogy kit, it almost comes to even money.

The only and I mean O N L Y thing that stinks about the Manager 30 is its a bit of a weak tit. If they made a manager 50, I would be there in a second.

 

[Scalf77]

My first question is on your option one, “Honda 2000 Generator -> SMB installed breaker panel -> Blue sea 7622 ML-ACR Automatic Charging Relay”. What SMB installed breaker panel are you referring to? The AC Breaker panel? 12 Volt? Do you have a AC charger built in? I guess the question is are you using AC-out of the generator or the 12-volt charging port.

The Blue Sea 7622 ACR is not a charging device is just allows you to connect the two battery systems together. When the van is running it will let the alternator charge the additional capacity of your house battery system.

One could make a case to disable the 7622 when charging the house battery system. Especially if you are limited with your house charging (solar). It is possible that a bad (old) starter bat could be stealing some of your limited power.

It would be nice to install a proper battery monitor, this would give you better status on the SOC of your battery, allow you to get better measurements of your daily usage and track your solar output. You should be able to get some data from your existing solar controller.

After that come up with a plan for charging your house battery. Unfortunately, alternators are not designed to fully charge wet cell or AGM batteries. If you have been counting on that as your primary charging method, your house bank has most likely been undercharged and has lost capacity.

Solar can help with that, but that general charging algorithm takes time, once you hit the absorption stage, the charger turns into constant voltage controlled current mode. The phase takes time (default 2 hours) and sometimes we never get the battery to 100% SOC. While solar is great and can help extend your trip, it may not have enough time to fully charge your battery.

Being that AGM likes to be fully charged as soon as possible, it behooves us to have a plan in pace that can fully charge the House battery bank. While that may be impossible while out on your trip, it should be completed once you are back.

You didn’t say the size of your existing solar panel, So I will assume that it is a 100-watt panel. The SB3000i that you have can support about 400 watts of solar panel input. You will need to gather the pertinent information for Voc. Vmp, Imp and Isc information to try and match up a new panel. One option would be to run a parallel portable panel. A couple different sizes can be found at Lensun Solar.

It is tough to say what your expected power usage will be with the fridge. The answer will be drastically different based on temperature. I can see a 2X power increase on very hot days.

Solar output will also very with location and time of year. The good news is that increased solar output generally comes on the days of 2X fridge power usage. You can increase solar output if you allow the ability to tilt your panels. I know the reality is that I wouldn’t want to climb up on the van to tilt the panels. The good news is that would not be a big issue with some portable panels deployed.

Depending on the age of your house battery bank, and how well maintained would determine how much capacity it still has. Very possible it is more like a 175 Ahr bank now or less.

 

[kbeefy]

2 group 31 should get you 100Ah of useable (200Ah/2) before dropping to 12v.
That should run your 3c/f isotherm fridge for 3-4 days no problem as long as it isn't 100 degrees outside.


Solar is cool and fun and all, but only works when the sun is out.
I usually have 300-500w of panels and it's cool when it's working and I'm getting free energy, but I don't rely on it.


For me, generators are overkill and annoying unless you need to run Air Conditioning.


I'm biased as it's the path I already took, but I'd get your house batteries checked and if they need replaced I'd bite the bullet and upgrade to 100Ah or more of lithium.


As Greg mentions, it's impossible to gauge needs without an energy audit, and every day/location is different, but I regularly ran my ARB chest fridge for 3-4 days on less than that.

 

[Ocsmb]

"My first question is on your option one, “Honda 2000 Generator -> SMB installed breaker panel -> Blue sea 7622 ML-ACR Automatic Charging Relay”. What SMB installed breaker panel are you referring to? The AC Breaker panel? 12 Volt? Do you have a AC charger built in? I guess the question is are you using AC-out of the generator or the 12-volt charging port. "

Sorry forgot to add that theres a Inteli-Power Converter with Charge Wizard installed there from SMB. I Am using the Honda 2000 as shore power plugging from the SMB port on the driver side of the rear of the van with a RV Power Adapter 15A Male to 30A Female then into the Honda 2000 AC Out 120V.

 

[Ocsmb]

When the batteries aren't charging is it possible the start batteries are drawing power from the house batteries while we are dry camping?

 

[Ocsmb]

My first question is on your option one, “Honda 2000 Generator -> SMB installed breaker panel -> Blue sea 7622 ML-ACR Automatic Charging Relay”. What SMB installed breaker panel are you referring to? The AC Breaker panel? 12 Volt? Do you have a AC charger built in? I guess the question is are you using AC-out of the generator or the 12-volt charging port.

The Blue Sea 7622 ACR is not a charging device is just allows you to connect the two battery systems together. When the van is running it will let the alternator charge the additional capacity of your house battery system.

One could make a case to disable the 7622 when charging the house battery system. Especially if you are limited with your house charging (solar). It is possible that a bad (old) starter bat could be stealing some of your limited power.

It would be nice to install a proper battery monitor, this would give you better status on the SOC of your battery, allow you to get better measurements of your daily usage and track your solar output. You should be able to get some data from your existing solar controller.

After that come up with a plan for charging your house battery. Unfortunately, alternators are not designed to fully charge wet cell or AGM batteries. If you have been counting on that as your primary charging method, your house bank has most likely been undercharged and has lost capacity.

Solar can help with that, but that general charging algorithm takes time, once you hit the absorption stage, the charger turns into constant voltage controlled current mode. The phase takes time (default 2 hours) and sometimes we never get the battery to 100% SOC. While solar is great and can help extend your trip, it may not have enough time to fully charge your battery.

Being that AGM likes to be fully charged as soon as possible, it behooves us to have a plan in pace that can fully charge the House battery bank. While that may be impossible while out on your trip, it should be completed once you are back.

You didn’t say the size of your existing solar panel, So I will assume that it is a 100-watt panel. The SB3000i that you have can support about 400 watts of solar panel input. You will need to gather the pertinent information for Voc. Vmp, Imp and Isc information to try and match up a new panel. One option would be to run a parallel portable panel. A couple different sizes can be found at Lensun Solar.

It is tough to say what your expected power usage will be with the fridge. The answer will be drastically different based on temperature. I can see a 2X power increase on very hot days.

Solar output will also very with location and time of year. The good news is that increased solar output generally comes on the days of 2X fridge power usage. You can increase solar output if you allow the ability to tilt your panels. I know the reality is that I wouldn’t want to climb up on the van to tilt the panels. The good news is that would not be a big issue with some portable panels deployed.

Depending on the age of your house battery bank, and how well maintained would determine how much capacity it still has. Very possible it is more like a 175 Ahr bank now or less.

Do you have a recommended battery monitor?

What's your recommended method of charging the house battery while at home?

Do you leave your fridge on when parked at home?

I typically, leave the fridge on and have shore power from the house to the van through the exterior smb installed port using the 30am to 15am adapter dongle.

 

[kbeefy]

It shouldn't, but if it does for whatever reason they would all 'equalize'. When your house batteries are down to 12v, what is your starting battery?

 

[Ocsmb]

It shouldn't, but if it does for whatever reason they would all 'equalize'. When your house batteries are down to 12v, what is your starting battery?

Sorry, I don't know. Dont have a monitor for the start batteries. Is there a way to monitor the house batteries and start batteries separately? Right now I only use the Blue Sky to monitor the house batteries.

 

[kbeefy]

As simple as a handheld voltmeter before you crank the engine.
One of those voltmeters you plug into the cigarette lighter would probably do the trick as well.

 

[Ocsmb]

As simple as a handheld voltmeter before you crank the engine.
One of those voltmeters you plug into the cigarette lighter would probably do the trick as well.

I have the cig ligther one. next time I camp I will take note.