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Old 10-17-2004, 01:31 PM   #1
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Cool Battery Charging with Univolt?

I need to have my '69 Ambassador plugged in full time. Has anyone figured out how to safely charge the battery while leaving the Univolt constantly plugged in? It seems like lots of batteries are overcharging and thus prematurely failing. Also lots of corrosion from boiling battery. Someone has to have figured out an external "smart charger" that you can hook between the Univolt and the battery. Does anyone have a link or a product that is available to make this work? Thanks!!
If there are other problems with leaving things plugged in full time that I am not aware off please chime in.
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Old 10-17-2004, 02:56 PM   #2
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common problem

This is a common problem with the Univolt. I use a battery disconect and from time to time allow the battery to charge as needed , others use a timer between the battery and Univolt do a search and you will find several solutions up to replacing the Univolt.

The disconnect I used is pictured, purchased at a marine store.

Garry
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Old 10-17-2004, 05:26 PM   #3
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Dump the univolt and upgrade to a intellicharger with charge wizard (or equivalent) see

http://www.airforums.com/forum...ead.php?t=7427

these go as a pair and run about $200 - $250
http://www.campingworld.com/browse/s...m?skunum=17298
http://www.campingworld.com/browse/s...21995&src=CROS

The key is that you want to cover two separate needs. The first is charging the battery. This is best done with a three phase battery charger. The second is battery maintenance. This needs something that can equalize the battery and keep the float at the right level.

also see
http://sierranevadaairstreams.org/ow.../charging.html
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Old 12-03-2004, 09:06 AM   #4
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If your concerned about corrsion from batteries get a Optima.......they are sealed at the posts.
Unlike all the other batteries out there.
Man......I sound like I work for them but i don't.
I just love their batteries.
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Old 12-03-2004, 09:22 AM   #5
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Blue Top Optima

Quote:
Originally Posted by Mike76251
If your concerned about corrsion from batteries get a Optima.......they are sealed at the posts.
Unlike all the other batteries out there.
Man......I sound like I work for them but i don't.
I just love their batteries.
I too have Optima blue tops and a red top in my Suburban. I love these batteries but have found out a few things of interest. These will die while being constantly charged by the old univolt even faster than the "wet" batteries. Very sensitive to charge rate! If you overcharge an Optima they will vent out their sealed vents and are usually ruined at that point. Change out your electronics and make sure to get a "gel cell" charge wizard. I went through all this a while ago and am happy with the results.
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Old 12-03-2004, 09:57 AM   #6
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For a given standard battery size, i.e. Length X Width X Height, the spiral-wrap, "six-pack" design of the Optima doesn't contant nearly as much battery (i.e. lead), and as a result, has considerably less capacity than a conventional AGM. You can see that in the weight. A yellow-top Group 31 Optima only has about the same capacity as a smaller Lifeline Group 24. Optima also does not offer a Group 27 size, and their Group 34 is just a shorter, and less capable Group 24 sized battery.

Code:
Lifeline AGM GPL-31T  105AH   195 min RC (81.3AH)   69 lbs
Optima AGM   D31       75AH   155 min RC (64.6AH)   60 lbs

Lifeline AGM GPL-24T   80AH   149 min RC (62.1AH)   56 lbs
Optima AGM   D34       55AH   120 min RC (50.0AH)   44 lbs

Lifeline AGM GPL-27T  100AH   186 min RC (77.5AH)   65 lbs

AH rating is at the 20-hour discharge rate (AH/20)
RC is Reserve capacity in minutes at a 25 amp rate.
Don't confuse AGMs with gel cells, which need a lower than traditional bulk charge voltage to prevent thermal runaway. An AGM, Optima, Lifeline, or other brand, should work with any good 3-stage charger designed for flooded cells, and that includes the Charge Wizard. Using a gel-cell Charge Wizard just results in slower charging.

I agree with Bryan. Whether you go AGM or not, pitch the Univolt and get an Intelipower with Charge Wizard.
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Old 12-03-2004, 10:39 PM   #7
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I'm at the point of replacing my deep cycle batteries, and am sold on the advantages of AGM's. I have the original '92 "Univolt" (which I think is actually Magnatek) convertor in my trailer. Should I pitch it and go for the Intellipower?
I did this in my '72 Land Yacht, and was very happy with the change (and the silence!). On the other hand, saving $250 toward purchase of the two new AGM batteries has attraction, if the '92 Univolt is a sufficient performer to justify it's staying aboard.
Thanks for your input!
Mark
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Old 12-04-2004, 03:22 AM   #8
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Factory Battery

My 2004 22' CCD has only one battery....a factory installed battery! I've heard on these forums they are whimpy Since I purchased a Honda 3000 EU generator, I didn't want to invest in a new battery immediately. I'm less concerned, now that I can recharge while boondocking (and hookup when available). I plan on traveling to some extent all year (boondocking less during the winter months). My concern is during the longer periods between trips (<30 days), do I need to keep the battery charged? Since my AS is in for service and warranty work now, I asked a dealer service tech if I would need a trickle charger. He said I could plug into shore power indefinitely and not hurt the battery....he replied that it was no problem, since the newer AS's use the automatic built in charge of the converter system for charging. The charging circuit automatically controls the current, reducing it as the battery increases in charge. Is this true?? If so, I will simply check the battery fluid levels monthly and keep it plugged into shore power indefinitely!
Another question...do I leave the battery switch in "use position" or "store position"
JIm
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Old 12-04-2004, 05:57 AM   #9
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Hi Jim,

You surely have a model 7355 switch mode charger in your 22' CCD, as I do in mine. I leave mine plugged in to shore power all the time, occasionally topping off the water level. http://www.parallaxpower.com/

As long as you're plugged in, your battery switch will stay in the "Use position".

Bob
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Old 12-04-2004, 08:58 AM   #10
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Quote:
Originally Posted by Mark Wiltrakis
I'm at the point of replacing my deep cycle batteries, and am sold on the advantages of AGM's. I have the original '92 "Univolt" (which I think is actually Magnatek) convertor in my trailer. Should I pitch it and go for the Intellipower?
I did this in my '72 Land Yacht, and was very happy with the change (and the silence!). On the other hand, saving $250 toward purchase of the two new AGM batteries has attraction, if the '92 Univolt is a sufficient performer to justify it's staying aboard.
Thanks for your input!
Mark
mark i can say this about the magnatek converter, they are rugged units.

mine was running into a battery with a shorted cell for about 2 months with no ill effect!

john
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Old 12-04-2004, 01:37 PM   #11
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Some items to note.

1) Lifeline says their AGM's charging values are the same as wet cell batteries. If you check the specs you will see this is so as the recommended ranges, while slightly different have significant overlap. Having different charging characteristics for AGM and wet cell is a nicety and not a necessity.

2) Equalization charging is not reccommended for AGM batteries. This makes me think the normal charge wizard should not be used on AGM's as it implements an equalization charging strategy (if I understand correctly). This 'non equilize' spec has implications for other battery maintainters as well.

3) The Optima batteries have very low internal resistance (Peukert coef 1.06 vs 1.2 for most other AGM and wet cell) This means that lower current draws will yield much better usable energy from an Optima that it will for most other batteries of equivalent weight. (i.e. it competes well with other deep cycles for normal RV use)

4) Gel Cells are a completely different animal and should not be confused with AGM or wet cell lead acid batteries.
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Old 12-04-2004, 01:45 PM   #12
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Quote:
Originally Posted by Leipper
Some items to note.

3) The Optima batteries have very low internal resistance (Peukert coef 1.06 vs 1.2 for most other AGM and wet cell) This means that lower current draws will yield much better usable energy from an Optima that it will for most other batteries of equivalent weight. (i.e. it competes well with other deep cycles for normal RV use)
Did you mean much better usable energy at higher current draws?

The Peukert coefficients for the Lifeline and Optimas (both AGMs) are very close.
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Old 12-04-2004, 03:18 PM   #13
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"Did you mean much better usable energy at higher current draws? "

no.

you get more energy out of a battery when you draw less current.

Look at the spec sheet for a battery that shows you the amp hour rating at differing rates. You will find that the longer rating (which means less current) has a higher amp hour rating than the higher current rating.

This is key to why putting batteries in parallel is as good as or better than serial for equivalent size, type, and weight in small battery banks.

see, for instance, http://www.absolutebattery.com/deepcycle.htm
A 225 ah (20 hour or 1200 minute rate, which is the one you usually see and hear as a measure of battery capacity) golf cart battery provides 75 amps for 115 minutes (142.5 AH) or 447 minutes at 25 amps (186.25 AH). Reducing the load by two thirds (75 to 25 amps) increases usable energy by 37% and reducing draw to last ten times the 75 amp rate brings the usable capacity up to 50% more or better.

75 amps for 115 minutes = 142.5 amp hours energy available
25 amps for 447 minutes = 186.26 ah
~11 amps for 1200 minutes = 225 ah

You can also see the calculation for a 2:1 current reduction at
http://sierranevadaairstreams.org/ow...ry-config.html

One way to visualize this is to realize that any battery has an internal resistance. This is why it gets hot if discharging (or charging) at high currents. The power loss (rate of energy use) for battery heating is related to the square of the current times the internal resistance of the battery. So reducing current reduces power by the square of the current change. This is probably why the Peukert law is an exponential.

do check my calcs! I try but sometimes I see numbers backwards or do other stupid things so I need a good proofreader ;-)

If you need help (or to add to an existing confusion) about power, energy, voltage, current, etc. see
http://sierranevadaairstreams.org/ow...ng/energy.html
and
http://sierranevadaairstreams.org/ow...ectricity.html

"The Peukert coefficients for the Lifeline and Optimas (both AGMs) are very close."
1.06 versus 1.2 makes a big difference when it is an exponent!
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Old 12-04-2004, 03:37 PM   #14
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boy, you guys are really getting into this subject!

with all those numbers my heads starting to spin, i hope i don't have to peukert!

john
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