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

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wolfe10

Texas

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Posted: 04/21/20 03:48pm Link  |  Quote  |  Print  |  Notify Moderator

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.

Yes, this is from an old Xantrex inverter/charger manual, so recommendations may have changed.

SO, best advice is to post ideal bulk/acceptance and float voltage for both our battery banks from the battery manufacturer. Also, the voltage output of your "not smart" converter.

That way we are all dealing with FACTS.


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hertfordnc

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Posted: 04/21/20 04:10pm Link  |  Quote  |  Print  |  Notify Moderator

Actually a relay is about $20 and a diode might be 10 or $12.
Wiring it up is easy.
And somewhere in there is the answer to my question I was just hoping somebody with electrical knowledge would connect the dots.

My recollection when I joined this Forum 16 years ago was it there was a great deal of discussion about ways to improve on a manufactured product, cams, headers, axle swaps, I could barely keep up.

I think the culture here has been influenced by social media.
But when I do work this out I'll let you know how it went


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Lwiddis

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Posted: 04/21/20 04:35pm Link  |  Quote  |  Print  |  Notify Moderator

If you want a project, proceed! If you want to go camping, dump the gel, replace with a wet cell and go camping.


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wolfe10

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Posted: 04/21/20 05:09pm Link  |  Quote  |  Print  |  Notify Moderator

Dave,

Can you give us the FACTS I asked for just above your last post. That will take the BS out of answers.

Hopefully, you want to base your decisions on FACTS, not options.

hertfordnc

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Posted: 04/21/20 05:24pm Link  |  Quote  |  Print  |  Notify Moderator

wolfe10 wrote:


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.


Perhaps i'm missing something, it is my understanding that gels need to be smart-charged with a higher initial voltage of 14.5 or so falling to something lower at 80%

My power supply is a 40 amp WFCO converter which i believe will not be appropriate for the gels.

Meanwhile, i have a small smart charger that automatically switches to float after a certain charge lever.

Also, because i happen to have the gels i plan to put one of both in a void inside where they can be unvented. That takes 100 lb off the tongue and leaves the front battery box handy for tools or rags or beer.

RLS7201

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Posted: 04/21/20 05:36pm Link  |  Quote  |  Print  |  Notify Moderator

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

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boogie_4wheel

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Posted: 04/22/20 11:18am Link  |  Quote  |  Print  |  Notify Moderator

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...


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hertfordnc

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Posted: 04/22/20 12:56pm Link  |  Quote  |  Print  |  Notify Moderator

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.

MrWizard

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Posted: 04/22/20 01:52pm Link  |  Quote  |  Print  |  Notify Moderator

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


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beemerphile1

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Posted: 04/22/20 03:20pm Link  |  Quote  |  Print  |  Notify Moderator

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.


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