Very Inexpensive Battery Maintenance Charger

[MEXICOWANDERER]

1.0 ampere output. 13.8 volts regulated charge limit. This unit is good for 100 amp hours worth of batteries. IMO the voltage is a tad high for a high antimony RV battery with temps 60F or higher but an inline 3 amp shottky diode will fix that in a rush (13.5 volts).

This is a good, reliable far east company I've dealt with many times. No chicanery. They send items via China Post, no shipping charges.

This is a reliable completely inexpensive way to maintain a number of batteries stored for the winter. I would recommend substituting cheap auto parts store battery charger clips for the alligator clips.

Sorry. I just cannot afford half a dozen fifty dollar battery maintainers.

http://www.buyincoins.com/item/25902.html

[jrnymn7]

Understood. thanks!

[MEXICOWANDERER]

You can drop output voltage .7 volt with a silicon rectifier. Do you only wish a drop of .4 volts? use a Schottky rectifier. Using parade voltage drops with multiple rectifiers inhibits total current potential so keep this in mind if you are thinking of a three, four or five rectifier voltage dropping system.

[jrnymn7]

But I'm asking if I can easily change the entire output voltage range (both high and low limits) of a psu, regardless of what stage of charging it will be used for. So, essentially, I'm asking if this shottky diode 'fix' would work as a buck converter, of sorts, capable of handling high currents of say 45 to 60 amps.

[MEXICOWANDERER]

My snotty design parameters call for a RV battery maintenance device to remain in float voltage up to an including the full potential of the device. Thus once float has been gained, 30-40-50 amperes load will still maintain float voltage.

Then when top charging is appropriate (scheduled), the batteries start out at float voltage and work their way upward to top charge limit of 15.0 volts at a charge amperage rated 5% of total amp hour capacity.

Similarly, AGM batteries can see a less frequent conditioning charge, using different parameters.

But the FLOAT event is for the benefit of the batteries not for the load. There is not a reason in the world to force bulk charge voltage limit *cycling* on a battery just because an RV's converter float voltage amperage potential has been exceeded. Some converters have absurdly low float threshold amperage limitations.

So yes, a properly set voltage float charging device with a 30 ampere capacity would be good for your batteries - but it in itself is only part of the recipe for ideal battery management.

[jrnymn7]

MEXICOWANDERER wrote:
Those little chargers IMHO are garbage. The ones with separate TRANSFORMER and regulator circuit. Too many regulator failures. But with the regulator cut out of the circuit stick a 3 amp axial diode inline with the positive charge lead and the transformer gets tamed. Recheck voltage. If need suggests it add a second diode this time a shottky to further reduce voltage by .4 volt. Ideal is 13.3 to 13.6.

Mex, would this work the same if trying to lower/change the voltage output range of a power supply unit such as the meanwells, megawatts, or even my turnigy? For example, my turnigy has an a adjustable range of 13.6 - 18 volts. Could I change that to say 11.6 - 16 volts, or would it only limit the upper end of its output range? so, 13.6-16v?

Thanks!

[jrnymn7]

Thanks Mex and Mena! I was hoping I didn't have to get into some fancy (and expensive) monitoring system.

And yes, an IR gun is still on my list of 'must haves'.

[mena661]

pnichols wrote:
I'd like to replace them with a couple of Rolls Surrette S12-160AGM batteries for a total of 290 AGM amp hours under the RV step where the current Group 29 C&Ds are, but sure hate to spend that kind of money for part time RV'ing batteries ... especially considering the shipping costs from who knows where I'd have to buy them (Canada?).

You might be able to get them from batteriesinaflash.com out of Las Vegas. They used to have them on their website but maybe send them an email and see if they can still get them. That's where I got my L16's. Had them dropped shipped to a local battery shop, didn't have to pay tax or shipping that way.

jrnymn7, just get an IR thermometer. I have one and I point it at the battery post and sometimes inside the cells. I find in my experience the battery post and the case are the same temp as the electrolyte.

[MEXICOWANDERER]

The last I heard Rolls had a full-line warehouse in Sacramento.

BEGIN EDIT
Trojan, Rolls Surette, Fullriver and OutBack Deep Cycle Solar Batteries. ... trojan Note: Battery Shipment Within the Continental US Only (48 States) ..... 888.898.5849; 777 Campus Commons Road Suite 200, Sacramento, California, 95825.
END EDIT

Batteries have to see considerable activity to effect increases in temperature. Simply tape the probe to the side of the battery, then re-tape it to envelop it in a cocoon.

[jrnymn7]

I am one of those whose batteries see widely ranging temperatures. So I'm about to install a digital temperature meter to my bank. But it's just one of those basic wire-with-a-probe-on-the-end thingys that gets attached to a battery post. And I can't help but fret over how (in)accurate it may be at displaying the actual temp of the batteries. The way I see it, on a cold windy day, the open-to-the-outdoors cabinet will cause the probe to read the ambient temperature of the cabinet, more than it will the batteries themselves. Likewise for very warm, calm days.

To at least help control the cabinet temps, I've considered partially blocking the large vent, adding a small piece of insulation over the post where the meter is attached, and perhaps even adding some hot water radiant heat to the cabinet, for cold weather conditions. Likewise, I plan on installing fans to help power vent the cabinet in hot weather. But I can't help but wonder if any of that is going to give me a realistic reading of the batteries themselves?

[pnichols]

Thanks for the detail, David.

I'm sure my ~8 year old C&D Technology AGM batteries are not capable of full capacity anymore - or at the least would be very surprised if I had them tested and they turned out to be. They've been on OEM recommended float voltage year after year while the RV is stored out in the back yard. (We're a long ways from being full-timers.)

I SOMETIMES - but often ignore/forget to - turn the float voltage off of them during hot summer days. Maybe they're in "pretty good shape" from the constant floating, but most likely far from full capacity if for no other reason than their age. I'd like to replace them with a couple of Rolls Surrette S12-160AGM batteries for a total of 290 AGM amp hours under the RV step where the current Group 29 C&Ds are, but sure hate to spend that kind of money for part time RV'ing batteries ... especially considering the shipping costs from who knows where I'd have to buy them (Canada?).

[MEXICOWANDERER]

pnichols, you have proven yourself to have never been in the least sarcastic with your questions never mind have been insulting. It is a pleasure to answer your questions...

Evaporation loss in a flooded battery is addressed by surface area of the electrolyte being minimized first by the small area of the filler hole then secondly by the miniscule area of the filler cap breather.

We all know the warmer water or water solution gets the higher the evaporation loss. But few RV batteries are exposed to 50C temperatures for prolonged periods of time. Therefore in a sense of priority evaporative loss is considered minor in the scheme of things.

Electrolytic water loss due to evolvement of hydrogen and oxygen is a horse of a different color. Even the larger of the two, oxygen, migrates through the cell cap with the greatest of ease. It is order of magnitudes smaller than water vapor. And along with hydrogen atoms it is accumulated under pressure which water vapor does not have by itself.

Chemical action and reaction increases with temperature. What may be a minor event at say 10C may become uncontrollable at say 50C

Plastic is a less than ideal conductor of heat. Heat radiation is such a concern of some auto manufacturers that they install a plastic shell over an underhood battery at an attempt to mitigate radiation effects.

Using a sensitive IR instrument with temperature resolution to one-tenth degree is yet another tool an individual can use to find and diagnose battery problems. When I am trouble-shooting a large off grid system or cruising sailboat battery bank issue it is the first instrument I use. Temperature variation is an alarm to delve deeper into the cell to find out what's up. The bank of course should be biased with a high amount of regulated charging amperage for this to be valid.

RV'ers who live in environments of extreme summer-winter temperature variation need to adjust bulk charging and float voltage limits appropriate for their ambient temperature. I manually adjust for 5C variations. Each 5C lost or gained warrants temperature compensation.

I do it manually, some thermistor systems do it automatically, the best kind of course measures interior battery temperature (or tries to).

The used WFCO I have, has a "working" voltage setpoint of 13.75. When temperatures climb above 30C, the output voltage is going to get routed through a 300 amp rated Schottky rectifier. This will render output voltage .4 volt less or a finish voltage of 13.35 If temperature climbs above 40C I'll move (it would be an all-time record). After have used the unit for almost a month, the factory 13.2 volts float event seems to be unobtainable. I attribute this to unavoidable frequent shore power glitches.

With a VRB example an AGM, an amp hour (better yet a kWh) meter is invaluable. In float mode the amount of energy gained in an indispensable tool for determining whether a voltage set point is valid. I do not have one here and I grumble about it. A kWh meter is high on the list of "must get".

[96Bounder30E]

Let's keep the personal attacks out of this discussion.......any further flaming in this thread will result in immediate closure without further discussion.....

[bigfootford]

Thought I would add a bit to some of this which I believe is pertinent.

I monitor battery temperature with a probe on the battery post when on the road/boondocking/camping.

I have had FWC's for years and for the past 5+ lifeline AGM's.

My 9 year old converter is a 9260 Progressive Dynamics with the remote to select the mode to charge when needed.

Prior to Solar and a good controller that has temp compensation I always did the following if my batteries needed charging:

If my battery post temperature was 90deg+ I would switch my converter out of boost mode 14.4 and drop it to Absorb 13.6... Did this for both my FWC's and Lifelines.
According to all the tech documents for batteries I always felt that I was not stressing my batteries. And likewise, when my batteries were cold 60deg or less and the PD would not go into boost mode 14.4 I would use the remote to switch to boost.


During storage I let my PD do the work.... Both my FWC's and Lifeline

13.2 float and the 14.4 every 23hrs for 15 min....

My lifelines are now 5+ years old... I test them for capacity quite often... They still have the original capacity.... Resting voltage v/s ah removed... (all one can do with AGM's)
Periodic load checking 20/c discharge to 60% SOC (40%)

When off grid my solar takes care of my batteries now...

I sometimes see 14.9vdc when the batteries are cold and charging....
And barely 14 when hot. Temp compensated...

I have many friends that have had the same continuing results with Lifelines.... One had 7 + years on his lifelines....

Jim

[pnichols]

Mex,

Is it possible that two kinds of "bubbling" are being talked about here?

Is it possible that outgassing due to a chemical reaction in the electrolyte from too-high a voltage being externally applied at the time will manifest itself as "bubbles". If so, might this be possible at temperatures way different from those normally associated with "boiling off" water vapor? And further, might the charging voltage being compensated for temperature (as recommended by battery OEMs) be referring to the controlling of this chemical outgassing ... as oppposed to controlling just water loss through high temperatures?

P.S. Not being sarcastic here .... just scratching my head on what the heart of this dicussion might really be about.

By the way, I still hold with: The temperature that us battery users are supposed to be worrying about with regards to what voltages we apply to a battery is the one easy for us to control ... the air temperature around the battery. The battery manufacturer's design, of course, controls the degree of transfer of this outside temperature into the interior of the battery.