Replacing Coach Batteries with GEL

WebbWebs · 05-14-2022, 12:06 PM

I have a 2000 Minnie (WF322E) with ~75k miles. I just replaced my coach batteries (again), this time with a single 8D 225Ah GEL battery by Crown. (I have a 2nd battery of the same that I may add in, should I need it.) While these are not new batteries, they are in excellent health and hold a good charge.

I have not been able to obtain much info on the converter/charger specs, but it would appear that the charging output to the bank is a bit high for GEL batteries. The quoted figures change from one reference to another, but the general consensus for peak charging voltage is 13.8-14.2 volts (for a 12V GEL battery), which is lower than a wet or AGM type battery needs for a full charge. The current charge rate seems to be at least 14.4 volts, which will eventually destroy them. Also, I would assume that the charger goes into an "equalization phase", which is also a no-no for GELs.

On my Minnie, the Converter shares a breaker with the Refrigerator. For now (just to be safe), I'm turning off that breaker once the battery has a good charge. Since the breaker is shared with the refrigerator, that also switches the fridge over to propane. (Not a big deal, but not "ideal" either.)

Is there a setting on the converter/charger that handles GEL batteries? And, if so, where the heck is is located?

I appreciate any help you can provide.

Jack

**creativepart** · 05-14-2022, 03:40 PM

Even when your RV fridge is running on propane it still requires 12v power for its controller etc. So I doubt your plan to turn off 12v power to it will work out as you hope.

The converter is located immediately behind or below your master fuse panel. Many times this is under your fridge.

I can’t find the source of information right now but have read that GEL batteries make very poor deep cycle/house batteries.

WebbWebs · 05-14-2022, 04:16 PM

Quote:

Originally Posted by creativepart

Even when your RV fridge is running on propane it still requires 12v power for its controller etc. So I doubt your plan to turn off 12v power to it will work out as you hope.

Than you, creativepart. I am aware that the fridge requires 12v for its controls, regardless of its mode of operation. But, since the breakers are for 120v circuits only, and the 12v power gets to the panel by way of the fuses, this was not an issue. That actually makes sense, because if you unplug from 120v "shore power" (habit... I'm a boater), the fridge automatically switches to propane.

It's really difficult to read the hand printed labels on the breakers, but they appear to be...

30A - MAIN
15A - Outlet / ?F?
15A - Outlet
15A - Micro
15A - Refrig / Conv
15A - Roof / Air

To test it out, I turned off the "Refrig / Conv" breaker, which did indeed turn off the Converter. And it did NOT turn off the Refrigerator, but only switched it from running under 120 VAC to Propane. The 12V power to the controls was not affected and the fridge continues to run properly under propane.

Maybe you can figure out what the first 15A breaker says. I could be "Outlet GFI", but not sure why the GFIs should have a unique breaker.

Thanks for your reply.

WebbWebs · 05-14-2022, 04:43 PM

Not sure why my previous reply is "waiting for approval", but I meant to answer the rest of your comment as well.

Since it still has not posted, I'll address it briefly...

While the fridge controls DO run on 12v, turning off the 120v breaker only causes the fridge to switch from 120v to propane. The controls continue to work as they should, even though the fridge switches to propane.

Batteries are always a topic of many conflicting opinions. I've used a variety of battery types in my bluewater sailboat. I also have over a dozen friends who have circumnavigated. Each would likely have posted a similar view of GEL batteries at one time or another. But ask most of them today and they would tell you that their GEL batteries far outlasted their AGMs. They would probably all concur that Lithium is their choice today, but would also say that GEL batteries make very good deep cycle/house batteries and would be their choice if Lithium was not an option.

Nonetheless, I HAVE the GELs. They are in good condition. And they are certainly a better choice for me (today), rather than investing a few thousand dollars in a LifePo4 bank for a 22 yr old Minnie that sits for 9 months, while I'm out of the Bahamas and off my sailboat. If I ever give up cruising by sail, I'll buy a new(er) RV and invest in a LifePo4 bank.

I thank you again for your response.

**creativepart** · 05-14-2022, 05:14 PM

Your previous reply was waiting for approval because you are a new member with 2 posts and you included a photo in your post. New members that post photos or links have their posts queued for approval. When you posted there should have been a notice about this but you may have simply not seen it. I’ll approve that post now.

I wasn’t suggesting you dump those batteries or buy expensive Lithium batteries. I was thinking there may not be an RV converter set up for GELs due to their seldom use in RV house battery banks.

**creativepart** · 05-14-2022, 05:17 PM

The first breaker says GFI Outlets.

I should have realized that the “breaker” you were referring to was a 110v breaker.

WebbWebs · 05-14-2022, 05:40 PM

I thought that might be the case. I've actually been a member for almost a year. But this may well have been my first post. Thank you for the explanation nonetheless.

Apparently, the charger is an integral part of the converter. I was trying to local a separate unit. I'm used to marine chargers which typically have unique settings for different battery types. Apparently that isn't the case. i'll see if it's possible to separate the refrigerator and converter lines into two breakers. May not be possible, but worth a look. Alternately, I could combine the refrigerator hot wire with the outlet hot wire. I don't typically use the outlets for much of anything anyway.

As a side note...
My sailboat still has a bank of 4 Trojan T-105 6v batteries... seventh year, I believe, and still going strong. I monitor them well and I use solar panels to keep them topped off, if I'm not running the engine. But I never hook up to shore power in a typical 6 month stay in the Bahamas Out Islands. I'm sure they are due for replacement soon.

Thank you for your experience and advise.

Jack

WebbWebs · 05-14-2022, 05:54 PM

Perfect... very helpful! In that case, I can check each outlet one at a time and see what breaker each is tied to. I can than move the refrigerator line to the breaker for the outlets that are seldom (or never) used (avoid an overload)!

At that point, the converter will be on a dedicated breaker, allowing me to cycle off the converter (and charger) when the charge on the GEL battery is getting too high.

Does that sound resonable?

MadMaxWinny · 05-18-2022, 04:49 PM

Gel Cells used to be the best game on the block for deep cycle applications. The only real weakness is that they MUST be charged on a Gel setting. The float charge cycle (where they live most of their lives) is a considerably lower voltage compared with Flooded and AGM. Float them too high, and they will fail in very short order.

Once you find your charger/converter, I'm guessing it will be the factory offering which likely will NOT be adjustable for Gels. No worries, those were pretty much garbage with a great deal of voltage swing. If this is the case, you can go with a modern multi-stage charger and swap it out right in place.

WebbWebs · 05-18-2022, 05:29 PM

Thank you MadMaxWinny. I found the charger... right in front of my eyes. I was expecting it to be a separate unit, but it was simply an integral part of the power system. Duh!

I rewired the breaker panel slightly. The converter/charger WAS tied in with the refrigerator on a 15A breaker. And there were TWO 15A breakers for outlets... one for GFI and one for non-GFI. As I test each outlet, I discovered that they weren't actually split between GFI and non-GFI, but mixed. Since I almost never use the outlets, and then for nothing consuming any substantial power, I combined all onto the same breaker for GFI. This allowed me to use the free 15A breaker for the refrigerator and leave the converter/charger by itself, and giving me the ability to turn off the charger should the voltage get too high for GELs.

So far, the voltage has not exceeded the peak of 14.4V, but I still disconnect the charger when the voltage gets to 14.1 or 14.2V. While driving, the alternator never gets near 14V, so that should be OK. The only downside to this is that switching the converter/charger off also switches the refrigerator to propane. (I'm no so sure that isn't more efficient anyway.)

Tomorrow, I'll install a Victron BMV 712 Smart monitor with Bluetooth, which was a spare for my sailboat. This will assist in knowing what's going on and if the GEL is at risk.

MadMaxWinny · 05-18-2022, 05:59 PM

What you propose, Jack would work, until you forget to turn it off a few times and leave it simmering overnight. Your alternator is doing enough damage, but few people do "smart" regulation to fix it. The combination might just do you in. 14.4+ volts is much too high.

What really makes batteries happy is a constant float voltage when not in use. Think of it like the Fountain of Youth for batteries. Letting them sit without a full charge is also a bad thing. If you are a sailor, you might remember my technical articles and column from years ago (Sail Magazine), on this very subject.