New to 12v fridge

[dcb17b]

I'm looking for some real world experience and advise. I just purchased a 2023 Jayco 25rb and it has a 12v fridge and no solar onboard. The battery they gave me was a 63 amp hour flooded battery. We do a fair amount of boondocking at NYS parks where there is a lot of tree cover so I'm not sure solar is my answer.I do have a generator to recharge the battery(ies) with. I'm thinking 2 100 amp hour flooded  batteries should be enough to get me by when not plugged in somewhere. Lithium is probably the best battery solution but  is too spendy for me at this time. How much battery does a 12v fridge use and will 100 amps be enough? 

[StirCrazy]

it totaly depends what kind of flooded batteries you go with, if they are the "hybread starting/deep cycle" that the rv dealerships sell then you don't ever want to go below 50% and if you can stay fairly shallow like 75% or higher for a deicent life span.  so realy you have 25 to 50AH to use depending how long you want the battery to last.  if you go true deep cycle then you can constantly use 50% of the capacity and get ok life out of it, so two 6V deep cycle batteries would give you 100 Usable AH.  if you go LiFePO4 then you can use the full 100% so two 100AH LiFePO4 batteries would  give you 100AH and last 4 to 6X longer than the previous options.  so you have to factor that in, when you look at price.  as was mentioned the LiFePO4 will charge faster also, this is due to less internal resistance so they accept a little more of the charge and less of the voltage is converted to heat.  pluss they only have a short adsorbtion phase.  I am a firm believer of solar panels and I would probably still add a deicent panel if I was in your situation, unless your in a barn your going to get some charge.  even if they don't fully charge the battery every day they will add to the battery and allow you to go longer between charges and for gennys that is the whole idea, use it as little as possible.  

Steve

[JDsdogs]

I’m just getting a handle on this 12v refer thing too. My previous was a 115v/ propane and the one before that was a 3 way 12/115/ propane. Both Dometic.   2way ran without issue for 22 yrs. The 3 way 14 yrs, again no issue. If the Norcold holds up 1/2 as long as my last Domestic, it may well live longer than me. Current 12v is Norcold 10 cu/ft. 
it draws 8.3 amps in day mode and 6.2 amps in night mode. Your owners manual should tell you what yours draws.  
Of course how many amp/hrs yours draws is rife with variables like ambient temperature, how often the refer door is open and closed , etc. 

safe travels. 

[valhalla360]

You have to check your specific fridge but ours pulls about 50w (4amp@12v) when running and run maybe 50% of the time (depends on outside temps). So typically, we use around 50amp-hr in a day.

Of course, you will also have lights, water pump and other draws but the fridge would typically be he heaviest draw. Doing an energy audit estimating what you will run while boondocking and how long each item is running is a good first step. 

You shouldn't take a lead-acid battery below 50%. Also, when charging with generator, it doesn't take long to get up to 80% but above that, battery acceptance tails off quickly. The result is, you would need to run the generator many hours to get to 100%...result is you have around 30-50% of the rated amp-hr as usable (50% if starting from full or if boondocking multiple days, 30%)...so your 63amp-hr has about 20amp-hr usable. 

If we assume you did an energy audit and came up with 75amp-hr per day used, you will need a lead acid battery bank of around 250amp-hr.

In contrast, lithium batteries can be drawn down to around 10% without harm and can charge fast right up to 100%. The result is you need 85-amp-hr of battery. 

So long as your battery charger (converter) can do lithium, a 100amp-hr battery with built in BMS are running under $200 on amazon. I've seen some down near $100 but I can't vouch for the quality. 250amp-hr of lead acid will be at least $200. Another benefit is weight (always a consideration with RVs). 100amp-hr lithium will be around 25lb. 250amp-hr of lead acid will be maybe 150-200lb.

Your current battery system is inadequate so an upgrade is needed. I would seriously consider lithium.

[StirCrazy]

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@valhalla360 wrote:

In contrast, lithium batteries can be drawn down to around 10% without harm and can charge fast right up to 100%. The result is you need 85-amp-hr of battery. 

that is kinda misleading it, you are not hurting it by tanking it to 0%, and there is no reason to be afrade of doing so.  the rated life span of a LiFePO4 is based on cycling from 100% to 0% many many times.  I think the older batteries I was working with that had a 3500cycle life, if you cycled then twice a weekend for 33 year they would at that point only have 80% of the capacity left.  ther new ones coming out are being listed as 8 to 10K cycle life.  all staying above 10% does is give you a bit more cycle life than they are rated for, so ya it is good practice to stay above 10% but your not doing damage by going below.

[valhalla360]

The point is still the same, you can use most of the rated amp-hr in a lithium which means you can use a much smaller battery bank and still have the same amount of USABLE amp-hr. Heck, when you buy them, they automatically jump you up to 100amp-hr anyway.