Battery maintainer help

acowhite wrote:
Wow. Thanks for the great information. Very helpful.

Some of the information that you are getting here is overkill for the question that you asked.

What's the price of the charger that you posted ??

If it's over $50, it is overkill. Chances are good that you will never need 80% of the features present.

If, however, the charger is too small (some are only capable of 1/2 amp) it's possible that it would never bring two 6 volts in series up to a truly fully charged condition.

RoyB wrote:

They will hold their charge for very long periods of time even in the winter months.

The big rule of thumb for me was to never let my batteries drop below their 50% charge state which is pretty close to only 12.0VDC.

I don't think much of anybody would agree with your "hold their charge for a VERY long period of time". Of course, that depends on what you consider "holds their charge" and what "very long" means.
One or two esteemed members of this forum claim that a deep cycle battery can self-discharge up to 30% a month (I think that is a worst case number).

As for the voltage which indicates a 50% state of charge, you're a bit low. See the attached table. It's closer to 12.2.
(Sorry I don't think we can "attach" things here so my cut and paste job is a bit messy. It looks fine in the editor.)

"TEMPERATURE COMPENSATED BATTERY
STATE-OF-CHARGE (SoC) TABLES
(Revised February 5, 2014)"
Wet Low Maintenance (Sb/Ca) or Wet Standard (Sb/Sb) Battery
Temperature Specific Gravity Reading Open Circuit Voltage Reading
Degrees Fahrenheit 100% SoC75% SoC 50% SoC 25% SoC 0% SoC 100% SoC75% SoC 50% SoC 25% SoC 0% SoC
120 1.249 1.209 1.174 1.139 1.104 12.663 12.463 12.253 12.073 11.903
110 1.253 1.213 1.178 1.143 1.108 12.661 12.461 12.251 12.071 11.901
100 1.257 1.217 1.182 1.147 1.112 12.658 12.458 12.248 12.068 11.898
90 1.261 1.221 1.186 1.151 1.116 12.655 12.455 12.245 12.065 11.895
80 1.265 1.225 1.190 1.155 1.120 12.650 12.450 12.240 12.060 11.890
70 1.269 1.229 1.194 1.159 1.124 12.643 12.443 12.233 12.053 11.883
60 1.273 1.233 1.198 1.163 1.128 12.634 12.434 12.224 12.044 11.874
50 1.277 1.237 1.202 1.167 1.132 12.622 12.422 12.212 12.032 11.862
40 1.281 1.241 1.206 1.171 1.136 12.606 12.406 12.196 12.016 11.846
30 1.285 1.245 1.210 1.175 1.140 12.588 12.388 12.178 11.998 11.828

Since TECHMATE was unkind enough to provide zero details about their product I wrote to them. Their ad was full of buzzwords and hyperbole. I'll wait until their answer arrives.

"Not Adding Water" is very similar to a doctor discussing a patient...

"He ain't dead 'cause there's no flies"

Landy's answer is the correct one. Charge -just enough- to maintain to-the-bitter-end maximum electrolyte density. The float voltage of a maintainer for a car RV battery is not the optimum maintainer for a 5% antimony true cyclable battery.

Better N Nuthin is a hell of a long way from optimum.

Anyone have comments about the http://tecmate.com/products/optimate5v/
I like that I can use it on 6v and 12v batteries

Thanks for help everyone. My question was answered - plus I learned much more than expected. My trailer is typically stored at my home and used for one 2-3 week trip per year plus weekend trips. From May to September I will leave the batteries in the RV with the RV plugged in at home. From October to April I will remove the batteries and store them in my garage. I will make sure that they are charged prior to storing and will then hook them up to this unit for longer term winter storage:
http://tecmate.com/products/optimate5v/
Thanks again.

Note about stand alone (portable) smart chargers; If you are depending on them to keep your batteries up be aware that should the shore power go out the chargers probably won't restart automatically when the power comes on again.

If the rig is where you can check every day or two this might not be a problem but in storage facility. . .

If you start off with absolutely full batteries, connect the maintainer and find the voltage less than nameplate spec (but be sure to adjust for temperature compensation if the maintainer has that feature!), then the maintainer is not large enough. If a single 800 ma rate kept my group 29 battery up to spec, then why wouldn't 1600 ma, 1.6 amperes, keep 230 amperes hours worth of battery up to spec? I have never seen a flooded battery maintained at 13.2 volts overcharge in 100F weather nor have I seen the same battery floated at 0F overcharge at 14.4 volts float. Unless you live where a Chinook can happen, temp compensation is not nearly as big a deal floating a battery as it is charging a battery. I simply would not store a battery where it gets to -40F nor to 110F. I prefer glancing at things once a week or so.

I have many different maintainer chargers, but only 1 of them is very consistent, 4 stage, temp compensated, actually 3 amp, and is designed and perfectly capable of fully charging over 200 AHs.
But if I had the choice, I would maintain any 12v battery(s) w/ a PD 9200 series RV converter charger. I don't know exactly what it does, but whatever it does, it does it RIGHT, trust me. Just check water each 6 months,.....notice I said "check", you won't add water once a year.
http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR4.TRC1.A0.H0.Xbattery+tender+plus.TRS0&_nkw=battery+tender+plus&_sacat=0
On edit, for 200 AHs, make sure the Tender is the "plus"....not "jr"

The 'up to 120 AH' is revealing about the maximum output of the maintainer.

They can't really know how much amperage each and every battery is going to require to be held at 13.xx volts, so they say X amount of amps our maintainer can provide, should be good for upto 120AH of battery.

It is really upto the batteries.

Far too many people, not really those on this forum, but automotive forums, act like a maintainer is the best charging source ever invented as it falls into grandpa's 'trickle charger is always best' mindset.

Get the batteries to a true 100% state of charge, hook the maintainer to them, and 2 weeks later see if they are still at maximum specific gravity. Then you will know if 'upto 120AH' applies to your batteries or not.