A battery with 475 minutes @ 25 amps reserve?!?!

[fkloster]

PC1800 Odyssey Battery - Odyssey Drycell Batteries

I guess if batteries for your big RV is the question.... the question is answered here!

I checked on pricing.... : Monster PC-1800 = $575.73 a piece.... (1,300 CCA with 475 minutes reserve @ 25 amps?! wow!

PC-2150 group 31's = $341.24
PC-2250 8D's = $448.74

[Gary RVRoamer]

That's similar to the L16 case style which is often used in off-grid solar systems, but a bit taller, with capacity to match. Capacity spec is about the same as an 8D, which Trojan makes in an AGM as well. The 8D is good if you have plenty of width but little height, whereas this one is good if you have height by a narrow space.

[BryanL]

interesting that the energy density is a bit low - 2568 watt hours for 132 pounds is a bit under 20 watt hours per pound. That figure gets closer to 22 - 25 for most RV batteries.

This also gets interesting because it hits the 'thick plates' deep cycle myth - "Odyssey is the only manufacturer that utilizes pure lead, flat plate technology in the construction process. This allows for more lead plates in a smaller area, exposing more lead to acid and creating a greater power density than any other brand." -- that particular bit of hype has some interesting contradictions and implications to think about.

The 6-10 year service design life is about on a par with other AGM type batteries. They claim superior deep discharge performance but I note that their 'technical guide' does not offer any data on that.

The web site could be a good resource for those interested in studying advertising hype. One should be very very careful in qualifying what is being said by looking for actual specification and measure to support the claims.

[fkloster]

Quote:

Originally Posted by BryanL interesting that the energy density is a bit low - 2568 watt hours for 132 pounds is a bit under 20 watt hours per pound. That figure gets closer to 22 - 25 for most RV batteries. This also gets interesting because it hits the 'thick plates' deep cycle myth - "Odyssey is the only manufacturer that utilizes pure lead, flat plate technology in the construction process. This allows for more lead plates in a smaller area, exposing more lead to acid and creating a greater power density than any other brand." -- that particular bit of hype has some interesting contradictions and implications to think about. The 6-10 year service design life is about on a par with other AGM type batteries. They claim superior deep discharge performance but I note that their 'technical guide' does not offer any data on that. The web site could be a good resource for those interested in studying advertising hype. One should be very very careful in qualifying what is being said by looking for actual specification and measure to support the claims.

Heavier batts because the plates are constructed of pure lead?

[BryanL]

re: "Heavier batts because the plates are constructed of pure lead?" -- higher weight density, to be precise. Lead that is inside a solid plate is not available for reaction with the electrolyte so it just adds weight without contributing to energy storage capacity. The website claims thin plates (high surface to volume the thinner the plate) to circumvent this which is rather funny because some of the 'true deep cycle' advocates insist you need thick plates for deep cycle batteries to make them strong and handle many cycles.

For the careful reader considering the claims and implications, a high degree of skepticism is warranted about the claims made. The idea of using pure lead in foil or plate form has many problems.

One of the improvements in modern batteries is how to construct plates such that a higher percentage of the lead in the plates can interact with the electrolyte. That is related to methods to increase the reaction surface area for large short term current capabilities.

Note that no lead acid battery does well with deep discharges (down to 80% SoC). Running your battery down that far as a regular thing is a sure path to a short battery life.

[fkloster]

Quote:

Originally Posted by BryanL re: "Heavier batts because the plates are constructed of pure lead?" -- higher weight density, to be precise. Lead that is inside a solid plate is not available for reaction with the electrolyte so it just adds weight without contributing to energy storage capacity. The website claims thin plates (high surface to volume the thinner the plate) to circumvent this which is rather funny because some of the 'true deep cycle' advocates insist you need thick plates for deep cycle batteries to make them strong and handle many cycles. For the careful reader considering the claims and implications, a high degree of skepticism is warranted about the claims made. The idea of using pure lead in foil or plate form has many problems. One of the improvements in modern batteries is how to construct plates such that a higher percentage of the lead in the plates can interact with the electrolyte. That is related to methods to increase the reaction surface area for large short term current capabilities. Note that no lead acid battery does well with deep discharges (down to 80% SoC). Running your battery down that far as a regular thing is a sure path to a short battery life.

These appear to be "AGM" batts though... does that matter?

[BryanL]

re: "These appear to be "AGM" batts though... does that matter?" -- I don't think so but then I haven't taken apart one of the batteries and aren't that far into the picayune details of manufacturing and design. (it might be fun but isn't really relevant to buying RV batteries, IMHO)

The basic concept of volume to surface area ratio is still something to consider. There is also the fact that it takes a few cycles to realize a battery's full capacity because its plates need to etch to provide more exposure and the implications of that on various plate structures.

The key issues are to look at the actual measures such as expected life (usually, warranty is the only reliable indicator for this), capacity, size, and cost. Then you don't want to get lost in detail that doesn't contribute to your goals.

[Cruzer]

Flooded batteries don't fare well when discharged below 40-50% of capacity. It really cuts into their lifetime. So, when using a typical 220 amp-hr battery you should only plan on using about 110 A-H of capacity before recharging.

But, that's not based upon percentage. What it is based on is voltage drop. It just happens that that voltage level arrives at just under 50% on a flooded battery.

AGM batteries are different than flooded. The do not have flooded electrolyte cells. The electrolyte is wrapped in glass mats around the plates therefore they do not outgas any hydrogen like flooded cells do. They also have less internal resistanace so they take a charge faster. That same cell design allows the batteries to run longer than flooded batteries before they get to that critical voltage dropoff point. If you plot the voltage drop over time on a graph you would see a flooded battery curve down fairly quick while an AGM extends out farther and flatter. The end result is that you will get about 30% more runtime from an AGM battery than a flooded battery of the exact same rating. I've found that converting to AGM batteries is just like getting 30% more batteries for free. Well, not exactly "free" because they do cost more. But they take up the samespace as flooded so in that regard you gain capacity. They also last longer than flooded so some of that initial cost is recovered over time.

[BryanL]

An AGM battery is a lead acid battery with the electrolyte contained in a glass mat. It will outgas like other lead acid batteries if overcharged. Being sealed, it is sensitive to overcharging because of this.

The life of an AGM battery is reduced when you deep cycle it just like any other lead acid battery. The curve for number of cycles versus depth of discharge is similar to other lead acid batteries.

While an AGM does have a lower internal resistance than other lead acid battery types and also a lower self discharge rate, it won't provide you more energy for "free." The energy density by weight (or volume) is about the same as is the Peukert coefficient.

From the NAWS FAQ, the indications are that you can expect up to a 50% longer life from an AGM but this depends a lot on use profile, maintenance management, and other factors.

AGM's are lead acid batteries. They are just constructed a bit different from your usual wet cell batteries or other sealed lead acid types. The differences are minor in the context of other things that influence batteries of this chemistry.

AGM's are nice batteries, but, please, let's use actual reliable measure and avoid anecdotal hype.

[Cruzer]

Sorry, I guess my 30% longer runtime was based on my actual experience rather than an engineering paper.

Yes, it is a lead-acid battery. Never said it wasn't. It's not a flooded battery, as I stated. For all practical purposes AGMs do not outgas. Yeah, if you want to get technical they can under extreme conditions, such as over-volting, but for practical purposes you can place them anywhere you need to in an RV without fear of hydrogen gas expoding.

[BryanL]

re: "based on my actual experience rather than an engineering paper." -- no need for this IMHO. You have a valid experience but it is only one sample with many unknown variables. The NAWS FAQ is based on very many samples and reflects a variance that acknowledges the influence of the variables involved. (it isn't an "engineering paper" either but rather a vendor's experience.) Warranties are a manufacturer's promise and that can be a good guide as well for longevity.

Code does not distinguish AGM's from other batteries as far as battery boxes and proper ventilation. There are reasons for this.

AGM manufacturers warn about charging voltages and such things as equalization. There are reasons for this as well.

The lesson is that we need to be careful in extrapolating one or two experiences (including our own) by realizing that they are only a very small part of the entire picture.

[Gary - K7GLD]

WELL, nice thing about the battery in the lead post, is that with proper leads, you also have a nifty on-board welding setup at your disposal...