MLW sub $500 robot

The Artist Formerly Known as Kap'n Salty wrote:


You can choose the charger.

I can't find the specs on that battery. I would be curious as to its internal construction and plate materials, not to mention where it resides. A 5 year life of a SLA battery is certainly not impossible, but difficult to attain at room temperature, very difficult to attain in MA (where I live) unless it is in an air conditioned or temperature controled room. The North Eastern part of the country has very dramatic temperature swings both in shorts spans of time and year 'round. We have regular yearly lows of 0F (and lower) and regular yearly highs of 100F (and higher). We regularly (at least a few times a year) have days which have, sometimes greater than, 40F difference between the previous day.

Well, I assure you I am honerable to a fault.

A simple 28 day timer would work, run a relay that connects and disconnects the charger one a month. For the bet, I would absolutely implement such a device, that way it wouldn't be forgotten.
Anyway, we have really run with the topic of batteries, I think if we can conclude the original argument that I am, in fact, using a deep cycle battery in my robot. :-)
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mlw wrote:

The robot resides in my office, which is always room temperature. Presumably room temperature is more or less the same in MA as it is here (maybe a tad cooler -- South Louisiana winters aren't particularly brutal). Both batteries were purchased from Herbach and Radelman, and both look like they would be used in UPS and fire alarm applications. The point of my little rant was that charger design is critical to battery life. It's really common for folks to buy crappy chargers and ultimately screw themselves on battery cost. Note that my application really isn't the same as long term storage -- but this is a robotics group, after all.

I doubt you can know that without taking the battery apart -- but as I imply above, I don't think it matters (at least for gel-cells) when a good charger is used.
My guess is that a major factor in the poor performance of UPS batteries (when installed in the UPS) is lousy charge circuitry, not the battery itself. I've certainly abused the crap out of mine -- but it may be that a prompt, 3-stage recharge staves off permanent sulfation. I have never, ever, left these batteries for long in a discharged state, although I have on occasion discharged them to the point that they show 8 and 1/2 volts or so connected to a load.
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The Artist Formerly Known as Kap'n Salty wrote:

Sigh, this is where this whole sub-thread started. Have we not covered any ground? There are three clasifications of lead acid batteries, starting, marine, and deep cycle. Depending on the internal construction and materials used, deep cycle lead-acid (sealed or otherwise) have variable discharge depths, but they are classified as deep cycle.
We have discussed chargers, storage, internal construction, materials, etc. already let us not do it again.

I 100% agree, but don't discount temperature and voltage spikes.

Is that 8 1/2 volts under load? Why is it when the load is disconnected? Most of the battery volt measurements assume no load.
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mlw wrote:

Yes -- deep cyle lead acid batteries are indeed classified as deep cycle lead acid batteries. Did you mean all gell-cells or AGMs?

It's usenet, new guy -- get used to not being in charge of the discussion.

From memory, still a tad under 9, once around 9.2. Again, this is from memory -- lately I don't check. I'm note even sure the regulator still functions (much) at that point, but (again) I've never checked.
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The Artist Formerly Known as Kap'n Salty wrote:

If they are not classified as Marine or for starting applications they are "deep cycle," and of course, some are deeper than others.

I'm not a "new guy" on usenet.

That 9volts is under load correct? What is it when it is not under load?
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The Artist Formerly Known as Kap'n Salty wrote:

Nevermind --- I get it. But I believe the number of cycles comes into play as well as the depth. The term "deep-cycle" also appears to be somewhat malleable.

I should also note that the discussion has actually been useful for me -- as it turns out, I had another look at those batteries. The prefix part number is "LC", not "LG" as I wrote. The 5ah is no longer manufactured (but you can still find the specs in the discontinued section -- look for LC-R125P), but the 7ah is an LC-R127R2P.
As it turns out, both of these are AGM-based, not ordinary gell-cells as I had assumed (and as H&R sold them as). The panasonic VRLA line appears to be designed for both standby AND motive applications, and are probably true deep-cycle.
A 5 year or better lifetime for these batteries at room temperature is an entirely reasonable expectation according to the specs. The stated lifetime of the LC line is actually 6-10 years using the stated discharge assumptions.
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The Artist Formerly Known as Kap'n Salty wrote:

"deep cycle" as it is used is sort of a catch-all for non-marine and non-starting batteries. Starting and marine batteries as designed for very low internal resistance, starting more so, of course.

Got them.

What is "true" deep cycle? Some batteries will cycle deeper and more often than others, but that does not mean other batteries are not "deep cycle." There are many SUV vehicals, and some are better than others, but that does not mean the others are not SUVs.

According to the specs the life is 3~5 years on a trickle charger at 25C, and approx 5 years at 20C. I would take the 5 years life as a best case scenario.

I see no reason to make that assumption.

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mlw wrote:

Look again -- not for the LC part numbers. You're looking at the specs for the

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The Artist Formerly Known as Kap'n Salty wrote:

http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_VRLA_LC-R127R2P.pdf
"For main and standby power supplies Expected trickle life: 3~5 years at 25C, Approx 5 years at 20C"

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mlw wrote:

http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_VRLA_LC-R127R2P.pdf
You need to give me at least TWO tries for all of my postings. Up to FOUR if I've been drinking.
(I hit post instead of cancel after deciding it would be a good idea to actually check the datasheet for the part in question before posting. Thus the incomplete sentence. See followup about the specs for the entire LC product line. )
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The Artist Formerly Known as Kap'n Salty wrote:

http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_VRLA_LC-R127R2P.pdf
DOH!!
Don't you hate it when the product sheet says something different than what you expect. :-)

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mlw wrote:

http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_VRLA_LC-R127R2P.pdf
Not as much as I hate it when my hand acts independently of my brain. Depending on what my hand is doing, I mean.
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The Artist Formerly Known as Kap'n Salty wrote:

http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_VRLA_LC-R127R2P.pdf
And wether or not you get caught, I suspect. :-)

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mlw wrote:

As I said, the term is somewhat malleable -- but I have read that a "true" deep cycle battery is suitable for regular motive use (golf carts, fork lifts, wheel chairs), and stands up not only to depth of charge, but FREQUENT charging from a discharged state. 300-400 cycles as opposed to say 30 or 40.

You're right: The stated specs for the LC line as a whole indicate 6-10 years, but the spec for my particular part indicates 5 years at 20C. Interesting contradiction.

Not for robotics use -- but it does tend to explain why my batteries are just now showing signs of wear after nearly 5 years.
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The Artist Formerly Known as Kap'n Salty wrote:

A liquid acid with solid lead-antimony plates could last between 6-10 years and take deep deep cycling < 20%, plus there are probably a few newer plate materials that offer better strength and chemical stability.

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mlw wrote:

First, I'm not even sure I understand what you're comparing. A battery which is trickle charged is typically used in a standby application like a UPS. So the useful metric for this application is the number of years the battery can be maintained with the trickle charge and still be called upon to provide its rated discharge.
The useful life of a battery which is cyclically charged and discharged is measured in number of cycles - a metric which is inappropriate for a trickle charged battery.
Any data that you choose will show that deeper charge discharge cycles result in a smaller number of total cycles which the battery can provide. Trickle charging is close to zero depth of discharge. This is, at the least, suggestive.
Panasonic provides information about its lead acid batteries here: http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_VRLA_Overview.pdf Page 8 is particularly relevant.
Mitch
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