Cheap way to isolate and charge gel cell- relay or diode ?

[hertfordnc]

We have a 19 foot Hybrid. We will not do a lot of boondocking. i have a 100 amp Gel cell and a gel cell charger that keeps it properly topped off.

Meanwhile, the campers 12V power supply would damage the gell.

So i want to isolate the gel from the campers 12 volt system when I have shore power.

One option would be a 110V relay that cut out the gel whenever 110VAC is present

A cheaper simpler option would be a diode to prevent the camper power supply from putting voltage to the battery.

But i wonder the battery would charge properly if it also had communication with the rest of the DC system?

Is there an existing product in the RV tool box?


thanks

[hertfordnc]

time2roll wrote:
Do we even know the battery, converter and charger specs yet?
How do we custom design something for something we don't have specifications?

Until then just lift a battery cable when using the converter.

The specs don't matter. I have a the right charger- a 10 amp unit designed for gel cells. The issue was just switching.

I found the right relay- I will probably go with that

[time2roll]

Do we even know the battery, converter and charger specs yet?
How do we custom design something for something we don't have specifications?

Until then just lift a battery cable when using the converter.

[MEXICOWANDERER]

OPTIMA WAS INTRODUCED AS

THE SPIRAL CELL BATTERY

No emphasis on Gel, AGM or plutonium. Been there did that...

[full_mosey]

wa8yxm wrote:
It appears I'm older than you I go back to 2005 when it comes to serious battery research and the 1960's when it comes to batteries in general.

Okay, fine. However you must agree that that is not relevant to today's topic. Surely(and, I know, don't call me Shirly 🙂 ) it was not your intention to diminish Optima's reputation.

what Optima called them in in 2009 was relevant to me in 2009 when I was choosing an AGM battery.

As it turns out, my FLA starting battery failed on that cold Jan morning. It was the factory FLA and 6 years old when it failed, which I considered good service. At that time I needed to make a battery decision and someone I trusted recommended the Optima. There was one at Sams Club about a mile from the house. I have not regretted taking that advice. In the meantime I have learned to choose a different brand of AGM. In fact, I have been 100% AGM since then.

The history on this forum clearly shows you used to say "Go ahead and waste your money" when giving advice to others considering AGMs. You are entitled to your own opinion.

I still buy green bananas! 🙂

You may be interested to know that I was having problems receiving channel 5 here in OKC on my DIY TV antenna. I found that 5 was broadcasting on RF 13, so I added two 17.4" elements for VHF. Now the reception is good.

HTH;
John

[wa8yxm]

full_mosey wrote:
Some people say that Optima said their AGMs were gels.

I don't recall ever seeing that on the Optima web site as far back as 2009.

It appears I'm older than you I go back to 2005 when it comes to serious battery research and the 1960's when it comes to batteries in general.

[full_mosey]

Some people say that Optima said their AGMs were gels.

I don't recall ever seeing that on the Optima web site as far back as 2009. I bought my first, and only, Optima Yellow-Top with light gray case in Jan 2010. Today, it is starting my 6.0L V8 gas engine in my 2004 GMC Savana. It has 750CCA in a 43.5lb package. It will still kick a 53lb FLA out the back door. 🙂

HTH;
John

[full_mosey]

hertfordnc wrote:

wa8yxm wrote:

Gel on the other hand is a very very very picky eater. Charge 'em too fast or too high a voltage and they won't make you happy.

I know the O/P said "Gel" but gel's in the sizes we use.. not popular.

Actually, AlphaCEll Premium. - 100 amps each, i have two. Definitely gels. I got them a couple years ago and used them in a popup. (overkill) Also used them in a hitch mounted camping box on an SUV. They would run a dorm fridge through an inverter for 24 hours.

THey are 7" X 16" and weight 95 lb each. I found a narrow, underused storage area aft of the axle I plan to put them it.

You will likely get a lot more use from them. A fellow camper just retired 4 6V gels that he put in his motorhome in 2006. They were bought from Batteries Plus and were labeled Werker. They were charged with whatever inverter/charger came with his 2004 motorhome.

Some people say they were finicky. My long past research revealed that there is some truth to that regarding charging Voltage. The gel medium that holds the electrolyte has difficulty releasing bubbles that can form due to high Volt charging. These bubbles are the result of electrolysis; some are Oxygen and some are Hydrogen. These bubbles stick to the plates and reduce the covered portion of the plate's ability to participate in charge and discharge. The mfgr's guidance was always towards lower charge volts.

I hope you have the mfgr's documentation on your batteries.

HTH;
John

[hertfordnc]

wa8yxm wrote:

Gel on the other hand is a very very very picky eater. Charge 'em too fast or too high a voltage and they won't make you happy.

I know the O/P said "Gel" but gel's in the sizes we use.. not popular.

Actually, AlphaCEll Premium. - 100 amps each, i have two. Definitely gels. I got them a couple years ago and used them in a popup. (overkill) Also used them in a hitch mounted camping box on an SUV. They would run a dorm fridge through an inverter for 24 hours.

THey are 7" X 16" and weight 95 lb each. I found a narrow, underused storage area aft of the axle I plan to put them it.

[wa8yxm]

wolfe10 wrote:
Perhaps I do NOT understand the question.

Gel batteries are OK at a HIGHER voltage than wet cells. So, unless you are really over-charging the other bank (wet-cell or AGM), I don't see the issue.

There is a whole lot of confusion over Gel Cells. a lot of it thanks to OPTIMA who advertises their AGM batteries as GEL

AGM's are very very forgiving and take a slightly higher charge voltage from what I understand. Some of 'em can take a seriously faster charger (oters not recommended)

Gel on the other hand is a very very very picky eater. Charge 'em too fast or too high a voltage and they won't make you happy.

I know the O/P said "Gel" but gel's in the sizes we use.. not popular.

[beemerphile1]

I used to have slightly used gel cell batteries because I got Deka group 24 gel cells for free. I always let the converter take care of them without trouble.

[MrWizard]

1972 Revcon
Old Magtek converter
A diode is not going to do what you want
Either get a different battery
Or
Install a different converter
Even then you have to deal with the alternator voltage ,
Unless you disconnect the house from the alternator/isolator/combiner
And have no charging to the gel battery while engine is running

Are you sure it says GEL on the battery
And not Sealed AGM ?
Many people come on here calling any sealed battery Gel

AGM does not require any special treatment, other than a slightly higher max charging voltage,
Much better suited to RV use than Gel

[hertfordnc]

boogie_4wheel wrote:
You'll need an interposing relay that has a 120VAC coil, and a normally closed (N.C.) contact. The relay needs to be rated for the max amperage that you plan on drawing from the battery. \

THank you. That word "interposing" was a game changer in finding the right gizmo.

[boogie_4wheel]

You'll need an interposing relay that has a 120VAC coil, and a normally closed (N.C.) contact. The relay needs to be rated for the max amperage that you plan on drawing from the battery.

Stick the relay inline between the battery connection on the converter and the battery itself. Wire the coil of the relay to any one of the circuit breakers on the converter.

When plugged in to shore power, the relay will be energized, opening the contact and isolating the battery. The converter's DC output will power the trailer. Your gel charger would now be charging the battery.

When unplugged from shore power, the de-energized relay contact would be closed and the battery would now be powering the lights/fridge/water...

[RLS7201]

Diodes will have at least 0.6 voltage drop. Not a good idea.
If you continue with you plan, use a isolator relay.

Richard