Mixing battery types

[Coach-man]

Question for the battery "Gurus", what is the downside of mixing a gel cell with a standard wet cell type? Will I risk overcharging one or the other? Feedback and comments would be appreciated.

[KD4UPL]

Much is getting confused here. An Optima is a good battery and is an AGM. However, they do not have as much capacity per their cost nor their physical size as other AGM batteries. If you want an AGM for all the right reasons then that's fine, but I would look at others besides Optima.

Optima are designed to stand up to lots of abuse in racing, off roading, and activities like that. An RV battery really doesn't need to be built to withstand serious shock, vibration, being turned upside down, etc. So, it's a bit of a waste of money to buy one that is designed for that.

2 6v GC batteries are your best bet. This doesn't mean you can't have AGM, there are AGM golf cart batteries. If you want the advantages of AGM and the most amp hours in the space you have then AGM golf cart batteries are probably the way to go.

I would completely avoid gell batteries for RV usage. They are expensive and require very exacting charging for best performance. They also have less capacity per volume.

[Veebyes]

Gel cells will tolerate a certain amount of abuse. The voltage regulator on my boat alternator went bad & was charging my gel cells at 18V. They got a total of at least 10hours charging at this voltage with no noticable degrading. They lasted another 5 years after the fault happened.

Yeah, yeah, we have heard it a thousand times, a couple of 6V golfcart batterys provide the best bang for amperage buck. What these drum thumpers don't say is that they have to replace those wet cell batterys every 3 or 4 years. Expect 8 to 10 years service life out of a gel or AGM battery.

[time2roll]

Alternator initially charges at about 14.5 volts and will do far better than most converters that are fixed at 13.6 volts.

Compare amp hour ratings if you want to keep the lights on. AGM is superior at starting and I recommend Sears Platinum for start AGM.

[pianotuna]

Hi Coachman,

First, let me say that Optima are a good battery.

You may be confusing cold cranking amps with amp-hours at the 20 hour rate. Apples and oranges.

If you want a great AGM battery for rv's look at lifeline which will have about 100 amp-hours for a group 29. I think they are quite cost competitive with the Optima. The Optima blue top is about 50 amp-hours.

It is important, with any battery chemistry, to follow the makers recommendations. That may mean (or may not mean) that there is a new converter in your future.

[Coach-man]

Yes you are correct Optima's are AGM, sorry. One post states I would need a 3 stage convertor if I used an Optima, but I can put it in my TV without any modifications? Another states that because of its spiral design it is 40% less efficient than an old fashion lead acid battery, but group the optima is about 40% the size of a conventional battery for the same amperage? Lead acid batteries require maintenance, adding distilled water, not to much but do not let it go dry, require venting because of gas discharge etc. No I will take my chances with the optima's. They are an excel ant battery, will last as long or longer than a lead acid, with out the maintenance, will not spill, does not require venting, and will provide the same AH in a smaller space! Yes there are batteries that will provide more AH, i.e. golf cart batteries, and if I were going to be dry camping I would consider adding them with a solar charging system, but I do not now plan on any dry camping. Thank you all for your opinions.

[pianotuna]

Hi,

Optima have about 40% wasted space because of the spiral design. That translates into much lower capacity.

I would add another interstate and a modest solar system.

Coach-man wrote:
My new Solitude came with a single 12 volt lead acid battery, (an Interstate)! I was seriously considering adding a second battery in parrale. My first thought was too get an Optima deep cycle battery, but I guess that would be a bad end for both batteries! I guess I will wait until the Interstate dies, then get two Optimas!

[Me_Again]

Golf Cart batteries create the most AH for the buck! Costco has a fairly decent one made by Johnson Controls. GC batteries have much heavier plates to withstand the dischange/change cycles.

Chris

[time2roll]

Optima is AGM not Gell. You will need 3 or 4 optima to match the capacity of 2x group 27 or 2x GC2 wet cell. Also need 3 stage converter to properly charge AGM.

[Coach-man]

My new Solitude came with a single 12 volt lead acid battery, (an Interstate)! I was seriously considering adding a second battery in parrale. My first thought was too get an Optima deep cycle battery, but I guess that would be a bad end for both batteries! I guess I will wait until the Interstate dies, then get two Optimas!

[time2roll]

Some you can mix with varied results. But mixing with gell will probably shorten the life enough that you should just trade it in on a wet cell and not go through the hassle.

[KD4UPL]

There are flooded, AGM, and gell batteries. Many people confuse the AGM with a gell. A true gell battery is rarely found in an RV and they are very expensive.
Either way, each chemistry requires different charging voltages and times so mixing them means none of your batteries are ever charged exactly the way they should be.

[pianotuna]

Hi,

Gel cells are among the least forgiving. If the charge rate is too high there will be permanent damage to the cells. It could be done with appropriate switches and adjustments of the charging rate to fit the gel cell.

If the Gel cell battery is free, go for it. If you have to pay, then don't mix.

[Me_Again]

Never fix battery types, as they charge differently. Also never add a new battery in parallel with an old battery, as you will soon have two old batteries. When I put six volt batteries in the boat I try to get ones out of the same batch. Have 6 now over 8 years old. Next time I am going to install 8. Chris

[ed6713]

Google "mixing battery types" and you will get lots of answers. All saying don't do it. Under some circumstances, you could cause a battery to explode.