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Old 06-03-2017, 03:54 PM   #1
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Batteries!

Can the frig run for 8 days on the batteries on our 35 ft Miramar? We leaving for a 8 day cruise and having the coach sit in RV park w/o elec.
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Old 06-03-2017, 04:01 PM   #2
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If you are using the 2 6V Harris batteries that came with it definitely no. You will be lucky to get 12 hours. You will have to run your generator every morning for about 3 hours to charge them back up. If I were you, I would look into upgrading to 4 6V batteries.
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Old 06-03-2017, 05:01 PM   #3
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Techno, just curious. Why 4-6v instead of 2-12v?
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Old 06-03-2017, 06:01 PM   #4
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Techno, just curious. Why 4-6v instead of 2-12v?
6Vs tend to be more forgiving with discharge meaning they have more cycles and in most cases more amp hours. There are many people that use 12Vs and it works for them. It all depends on what you expect from your batteries and how often you use them dry camping. Best of luck.
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Old 06-03-2017, 07:43 PM   #5
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1 battery is better than 2 and 2 is better than 4 etc... from a technical perspective think of minimizing series and parallel cells required to provide X capacity and voltage for an optimal storage design. The 6V golf cart batteries have historically been a great compromise based on cost. It was the cheapest way to get the best cell storage per $ and typical capacity/use time in RV like situations. Still possibly true for some uses or views today even if simply based on local availability. However the apples to apples battery cells for 12V cost difference gap has become much more competitive making the 6V GC battery argument/belief have less validity these days. Now days about the only remaining argument is that 6V batteries are half the weight of the same cells in 12V, so individually they are easier to handle.
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Old 06-03-2017, 07:52 PM   #6
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I don't know any 12v battery that is the standard dimensions and weight that has the same or more amp hours as 2 6vs in series. Battery compartment size and total weight are limitations that need to be considered.
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Old 06-03-2017, 08:43 PM   #7
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I don't know any 12v battery that is the standard dimensions and weight that has the same or more amp hours as 2 6vs in series. Battery compartment size and total weight are limitations that need to be considered.
Standard dimensions? Well that sort of depends and includes 6V choices 12V 8D would be just one of the examples for similar capacity and is also a standard RV and boat size for comparisons to 2 GC batteries. But certainly I know the space limitation thing all too well with my current rig because I can't fit 2 GC batteries or any 200+Ahr lead acid based true deep cycle capacity combination! I've resolved myself to the fact that I'll need more modern chemistry cells to fit the space when replacement time comes. My previous RV wouldn't fit an 8D but 2 GC batteries fit ok.
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Old 06-03-2017, 09:10 PM   #8
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If you have the absorption refrigerator, you should be able to run it for quite awhile on propane. That will seriously diminish the voltage requirement which you would only need to power the control valve.
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Old 06-03-2017, 10:34 PM   #9
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One thing about 6v golf cart batteries is they are more energy dense that 12v. If you can't fit 6v then consider deep cycle trolling motor batteries, they're made to handle frequent charge and discharge, and can take light loads for longer periods of time.
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Old 06-04-2017, 12:23 AM   #10
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OP: have a great trip but I think we'd be emptying the Refrig.

Quote:
Originally Posted by TyCreek
1 battery is better than 2 and 2 is better than 4 etc... from a technical perspective think of minimizing series and parallel cells required to provide X capacity and voltage for an optimal storage design. The 6V golf cart batteries have historically been a great compromise based on cost. It was the cheapest way to get the best cell storage per $ and typical capacity/use time in RV like situations. Still possibly true for some uses or views today even if simply based on local availability. However the apples to apples battery cells for 12V cost difference gap has become much more competitive making the 6V GC battery argument/belief have less validity these days. Now days about the only remaining argument is that 6V batteries are half the weight of the same cells in 12V, so individually they are easier to handle.

Then based on your own information, 3 cells would be better than 6 within the same battery, which are configured in series? Less cells less plastic cell dividers = more lead plates, electrolyte = more energy dense in same space.
BTW: flooded cells heavier is better, more lead longer lasting battery. The batteries in our RV, EZGo are about 60-65 Lbs. ea. far from half the weight of the 2ea. 12V in the diesel truck.

Parallel configuration always present equalization issues as well. The batteries in a bank get out of sync with each other and the bank takes on the characteristics of the lowest common denominator(s) in the group. Not a desirable trait for required frequent cycling. GCs, RVs perhaps most solar arrays will perform much better in series configurations.

Redundancy is the primary benefit of parallel being able to use the bank minus a member. As in the diesel truck. Or adopted by say a POTS back-up systems perhaps only called into use a couple times a yr. High on maintenance, with individual cell testing of SG etc. and equalization of individual cells to optimize overall bank efficiency.

Lithium type cells will be the future as production costs continue to fall if you want to compare size and weights.. What Id like to switch to. Ahh $$ but whats in my wallet ?
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Old 06-04-2017, 01:55 AM   #11
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Then based on your own information, 3 cells would be better than 6 within the same battery, which are configured in series? Less cells less plastic cell dividers = more lead plates, electrolyte = more energy dense in same space.
BTW: flooded cells heavier is better, more lead longer lasting battery. The batteries in our RV, EZGo are about 60-65 Lbs. ea. far from half the weight of the 2ea. 12V in the diesel truck.
How do you figure?
To get 12V regardless of how you look at it with lead acid chemistry type 2V cells you'll need 6 ... The "series" thing is that the resistance between those cells and the cells themselves must be "matched" for optimal performance and life. The argument for 1 battery vs 2 is that "as manufactured" will have more optimal matching than we'll ever achieve by jumpering 2 random stock GC batteries in a serial configuration to achieve our 12V. Certainly with a good low resistance connection the negative impact is typically outweighed by the low cost of main stream produced GC form factor batteries.

Yes, weight tells us things about lead acid batteries but really doesn't change the energy density. Plate thickness and alloys do differ between starting and deep cycle designs and the thinking "heavier is better", is a great simple way to look at deep cycle lead acid batteries. More lead, thicker plates etc... as a reference really means typical of the best deep cycle cell storage designs. There's reasons for each battery's design and understanding these actual reasons for the differences helps us make better choices.

In simplest form: If you need 400Ah of 12V storage it is most optimal to get matched 400Ah cells regardless of the cell chemistry choice. Get as many as you need to achieve the voltage you require e.g. 6 lead acid cells. To achieve voltage greater than a single cell you have no choice but to connect them in series.
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Old 06-04-2017, 02:11 AM   #12
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Lithium type cells will be the future as production costs continue to fall if you want to compare size and weights.. What Id like to switch to. Ahh $$ but whats in my wallet ?
I've been playing with many Lithium chemistry battery solutions for quite a few years and yes WAY overdue for the RV community. Nice to see it is finally starting to change.

I caution against mixing Lithium and Lead Acid storage solutions in an RV or anywhere for that matter.

I ran some bleeding edge LiPo cells 14S in electric bikes and it was simply amazing how much energy they provided in such a small and lightweight space. As a safety note... I charged these outside in a fireproof container. No fear there's safe Lithium alternatives
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Old 06-16-2017, 01:38 AM   #13
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Hope I'm on topic here....I am on a boondocking related FB page.

We are taking delivery of an 2018 Ace 29.3 in a few weeks...plan is for light boondocking.....one fellow, who seems credible, is indicating one Battleborn 100 lithium battery will do a better job than the two stock batteries, or for that matter two flodded 6v batteries....the cost for this lithium battery is about $900 (not a typo)....i get that the price is kind of crazy high...but there are a lot of benefits.

I understand the length is about 2.5" longer than standard....oh, the weight is estimated at less than 1/2 of lead acid.

My question is...will one of the lithiums work from technical standpoint?
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Old 06-16-2017, 01:52 AM   #14
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Hope I'm on topic here....I am on a boondocking related FB page.

We are taking delivery of an 2018 Ace 29.3 in a few weeks...plan is for light boondocking.....one fellow, who seems credible, is indicating one Battleborn 100 lithium battery will do a better job than the two stock batteries, or for that matter two flodded 6v batteries....the cost for this lithium battery is about $900 (not a typo)....i get that the price is kind of crazy high...but there are a lot of benefits.

I understand the length is about 2.5" longer than standard....oh, the weight is estimated at less than 1/2 of lead acid.

My question is...will one of the lithiums work from technical standpoint?
Not without a Lithium specific balance charger. And sit down when you price that as well.
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Old 06-16-2017, 02:09 AM   #15
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A proper lithium battery circuit also needs a low voltage cutoff that won't be present in your mh...
Lead acid cells can be damaged and lose some life if run too low.
Lithium won't recover from it - and at that price tag...

EV manufacturers have a ton of circuitry/logic to manage the pack. They don't fully charge (at least the manufacturers I am aware of) or discharge the batteries - taking the cautious conservative approach to extend battery life overall.

Our power would be far less than an EV - but the same principles still apply (as they do to laptops as well...)
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Old 06-16-2017, 05:43 AM   #16
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Quote:
Originally Posted by David1912 View Post
Hope I'm on topic here....I am on a boondocking related FB page.

We are taking delivery of an 2018 Ace 29.3 in a few weeks...plan is for light boondocking.....one fellow, who seems credible, is indicating one Battleborn 100 lithium battery will do a better job than the two stock batteries, or for that matter two flodded 6v batteries....the cost for this lithium battery is about $900 (not a typo)....i get that the price is kind of crazy high...but there are a lot of benefits.

I understand the length is about 2.5" longer than standard....oh, the weight is estimated at less than 1/2 of lead acid.

My question is...will one of the lithiums work from technical standpoint?
Yes and no ...

Yes, if the pack you're looking at has a compatible and good BMS. Some battery solutions have a BMS to handle and control the cell needs. Several replacement options are made with LiFePO4 cell configurations that plug right into a lead acid 12V system. Some can presumably even get along ok with a chassis battery but make very sure the BSM is truly capable/compatible.
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Old 06-16-2017, 12:19 PM   #17
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Quote:
Originally Posted by gmc
EV manufacturers have a ton of circuitry/logic to manage the pack. They don't fully charge (at least the manufacturers I am aware of) or discharge the batteries - taking the cautious conservative approach to extend battery life overall.

Our power would be far less than an EV - but the same principles still apply (as they do to laptops as well...)
Yeah a good rule of thumb for EVs is that they leave about 5-10% at the top and bottom. Some are more conservative than others (I believe the Volt leaves the most at the top and bottom--probably why so many Volt owners report the battery holding up well after many years).

My old Focus Electric also left quite a bit in the battery (of the 23kWh battery, only about 18kWh was usable).
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Old 06-16-2017, 01:05 PM   #18
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Only way I know for sure to run a fridge for 8 days unplugged is with solar.
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Old 06-16-2017, 01:33 PM   #19
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A usable capacity of "only" 18 kW-hour should run some residential fridges for 8 days, or run an A/C overnight with enough power left in morning to make coffee.

If cost ever gets down to $300 per kWh including battery management system, it will be a huge game changer in RV design. Most quality drop-in batteries I've seen are still in $1,000/kWh range at retail which makes them a little too pricey.
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Old 06-16-2017, 04:47 PM   #20
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