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Old 07-15-2009, 06:09 PM   #1
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Best all-purpose batteries?

I need to buy new batteries. Current ones barely hold a charge (might have left some 12v accessories on overnight on multiple occasions, oops!). I need to take measurements, but I have two large batteries that are leaking acid from the top (tossed baking soda everywhere as a stop-gap measure). The largest battery I found at a Fred Meyer's was marketed as an RV type, 730 CCA, and was still a decent bit smaller than one of the batteries I have now.

Two problems. The biggest one, is this vehicle was designed to just have one set of batteries. The same ones that start the engine/generator also powers the inverter. Second, is it's wired up to have two 12v batteries, so going to two 6v would be a pain (I know I know, just wire in series vs parallel, but I'd still have to rewire things I'd rather not fool with).

So, is there a battery that's good at deep cycling, and can still start an engine if needed? Would this be one of the few cases where an Optima is worth the HUGE price difference? Side-note, anything that can take lots of vibration is a plus, since I still need to get back to Tennessee from where we're at in Alaska, and the roads are really bumpy in places.

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Old 07-15-2009, 08:42 PM   #2
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Re: Best all-purpose batteries?

Optimas are a good multi purpose and will handle vibration better than a regular flooded battery.
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Old 07-15-2009, 09:11 PM   #3
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Re: Best all-purpose batteries?

Optimas have a substantially LOWER reserve capacity in a given footprint versus a conventional wet acid battery (like 75 amp hours versus 105+ amp hours). My vote would be for the whole rewiring affair and building a separate house battery bank, but the doesn't appear to be the best option for you at this point. Can you give me a little more information about the vehicle, footprint you have to work with, and power demands?
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Old 07-15-2009, 11:07 PM   #4
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Re: Best all-purpose batteries?

Quote:
Originally Posted by Smitty
I may have misunderstood your post, but you need to seperate your starting battery(s) from your house batteries. If I read that wrong.....nevermind

Smitty
Yep, now we just need to convince him that it's worth the work to do.
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Old 07-16-2009, 12:47 AM   #5
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Re: Best all-purpose batteries?

Finally found the correct replacment batteries. Was checking out the Optimas at Sam's Club, and they had two huge commercial batteries (not Optima brand, forgot which brand to tell the truth). After taking measurements, mine is the 8D size. Can't find them online yet to get full specs, but I did write down 1400CCA/400RC, model PF8D, $124.62 each.

At least I have a size to go by! Now to make sure I get ones that are deep cycle, but can handle starting an engine.
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Old 07-16-2009, 11:37 AM   #6
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Re: Best all-purpose batteries?

It used to be a bookmobile. Already had generator and two huge 8D batteries. Need to boondock overnight occasionally (Whenever I'm on the road, I like to just pull off somewhere for the night). The batteries should be able to power the fridge overnight, and ideally occasional use of lights, laptop, tv, etc. At the least I'd like to shut the generator off at night if we're not needing to use a/c or heat (no propane, so even heat would use electric).

At this point I'm not too worried about whether it'd last a few years vs ten. This RV has a short lifespan for full-timing purposes, I figure about another 2yrs 3mos, maybe add a few months. Basically due to size constraints, it'll comfortably handle a family with two adults and two kids. A third kid could use the co-sleeper bed next to the main bed for about a year. Figure another six months to try for the third kid, nine months to be born, then another year to outgrow the co-sleeper...and that's about it. Maybe things will change and we'll only need this for occasional trips to state parks, visiting family, and Disney World. If so, it'd handle the job fine (couch pulls out into a bed).

I "think" that even a non deep-cycle battery would be ok, though I haven't measured my power needs (I know I know, I need a kill-a-watt). Two honkin' huge batteries, only needing to power a fridge and some misc items overnight, shouldn't be a problem. I hear Cat makes great 8D batteries, but not sure if I can find them here. Also hear that there's no true deep-cycle 8D battery. I'll keep looking, but gotta get something soon before our next side-trip (running the gen all night is a bit expensive, though still much cheaper than a motel room).
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Old 07-16-2009, 01:31 PM   #7
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Re: Best all-purpose batteries?

Got a quote for what are supposedly 8D deep-cycle batteries by Interstate. $339.95 per battery. Might just go with the $125 battery and hope for the best.
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Old 07-16-2009, 08:32 PM   #8
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Re: Best all-purpose batteries?

NOW we have the information required to assess your needs. I was thinking you were stuck with a pair of Group 27 or Group 31 batteries.

8D's are awesome batteries. They're just plain beef. Most companies make both a deep cycle and a starting version of 8D's, but if you look at the reserve capacity ratings you will find that they are very close. Cranking amperage comes from surface area of the plates while reserve capacity comes from the shear amount of material in the plates and is a fundamental difference in the construction of the batteries. After all, to maximize surface area in a given volume (group size) you must have many thin plates. To maximize the amount of lead you have such as for deep cycles you must make them thicker which results in fewer plates which means less surface area and less cranking amps.

So what makes 8D's so great? They have both a lot of surface area and a lot of lead in them! Like I stated before, there is room for a little change in either direction, but deep cycle and starting versions are very similar. Over the road trucks have used 8D's forever and they are often deep cycled overnight. You should see lots of service out of either choice.

There is a lot of information that goes into battery selection, but the biggest bit of advice I can give you is to shop by weight. The heavier the battery the better. It's not uncommon for manufacturers to use "filler" in batteries. Take your 6 volt latern batteries for example. Expensive ones will have four F-cell batteries in them while cheaper ones will have four D-cell batteries and a cardboard spacer in them. Seriously. Take an expensive one and balance it half off a table with the terminals facing out and again with them facing in and it will stay put. Take a less expensive one and do the same thing and it will fall off because one side is lighter due to the cardboard spacer.

Any idea who manufactures the cheaper ones you were looking at? There are only a few battery manufacturers in the country, but a lot of different labels that get slapped on their products. I happen to be a fan of East Penn-Deka, but that's just a personal preference.
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Old 07-17-2009, 12:10 AM   #9
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Re: Best all-purpose batteries?

Quote:
Originally Posted by the_experience03
Any idea who manufactures the cheaper ones you were looking at? There are only a few battery manufacturers in the country, but a lot of different labels that get slapped on their products. I happen to be a fan of East Penn-Deka, but that's just a personal preference.
Don't know the exact manufacturer, just remember right off that they're "Marketed by Interstate" or something like that. Went ahead and bought two, might try to get them installed tonight.
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Old 07-17-2009, 04:38 AM   #10
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Re: Best all-purpose batteries?

Ok, so I was trying to figure out just how much capacity I had, and see just how long I might be able to run the fridge without over-discharging these non-deep cycle batteries.

I go to Interstate's website and try to see what the closest battery they offer is. They only offer one 8D battery with 1400CCA, so I figure that's what I've got. It lists the amps as 1750. Specs here.

Edit: Removed my calculations, as I need to know what the amp hour rating of these batteries are. That's proving difficult to find. According to one equation just taking the RC into account, it should be about 216 per battery. Will research it some more.
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Old 07-17-2009, 08:57 AM   #11
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Re: Best all-purpose batteries?

According to this FAQ, 8Ds have 225-255 amp-hours.
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Old 07-17-2009, 09:57 PM   #12
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Re: Best all-purpose batteries?

A single 8D battery has roughly the same or slightly higher reserve capacity as a pair of 6v golf cart batteries. It would be fair for you to count on having 200 amp hours of reserve. The killer is that reserve capacity is rated at a certain temperature and a certain current draw and those specifications vary my manufacturer even, but I think you would be very safe using that 200 amp hour number.
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Old 07-18-2009, 10:52 AM   #13
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Re: Best all-purpose batteries?

it's important to realize too that if you have a 200 ah battery, you proably can draw 20 amps for 10 hours, but you cannot draw 200 amps for 1 hour.
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Old 07-18-2009, 08:52 PM   #14
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Re: Best all-purpose batteries?

Damn that Peukert guy!
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