Long winded battery question

[tropical36]

Originally Posted by Rr1985

In case anyone is interested in those batteries, it seems the only place that sells them is battery systems inc. Which has various locations, fortunately one wasnt too far from me. After all my searching, I could not find another brand that made sealed maintenance free lead acid deep cycle batteries in the group 31 size with the 105ah capacity. Only flooded and agm, and lithium of course. Weird...

Again, keep in mind that these are not pure deep cycle in nature and will not withstand the punishment of discharging and recharging. Not one RV manufacture that I know of, uses these for their OEM's and there's a reason for that. These are best suited on boats and especially if they have a trolling motor.
Best you can do is for trying to keep them up as much as possible.

[tropical36]

Originally Posted by Jchemie

I know your question was about what battery set to use, but I noticed many replies stated going to the big big box store for batteries. Has anyone ever tried getting golf cart & automotive batteries from Batteries Plus? They give a military & first responder discount, test your battery, free advice, carry the battery to & from your vehicle. Didn’t find that kind of service at the big box store. Oh, did I mention they were much faster because they were not so busy? You can also buy your LED bulbs for the interior & exterior lamps there and the AA & AAA batteries are less expensive thru them.

Their prices were good, yes a bit more than the big box but better than auto parts stores. Never had a bad experience or slow service at any of their stores I visited. They have stores across the USA.

Yep, and it only took me six months for getting them to honor a free replacement warranty that I had in writing. This only after constant pressure from the franchiser's main office, the Wisconsin consumer protection agency, where their main offices are located, the FL Attorney General and a couple of other agencies.. Also for knowing that I was about to take them to court and where they knew they had no chance. All's well that ends well however and with 4 of these blue top AGM's costing just shy of $1500 these days.
I still had to install them originally, remove them for their testing and for reinstalling them, but really wouldn't want anyone else fooling with them anyway. I mean anyone can install a car battery without mucking it up, but not so with a big coach.

[geordi]

Costco battery warranty is 36 months for everything OTHER than golf cart or marine deep cycle - those get only a 12 month warranty.

That warranty though is completely 100% refund and no questions asked.

Now about the difference in the warranty length and the "capability" of the batteries.... I had 8 GC2 batteries for a total of 880 amp hours at 12v. They NEVER seemed like they had that kind of capacity, and even with my solar setup maintaining them, they used a ton of water. That's one reason to get flooded batteries though, you can't add water to sealed batteries. If they lose it, it's gone.

Now supposedly they could be "deep" cycled without harming them, where "starting" batteries will be hurt by similar drawdown. But I have a very advanced setup and monitor the power use closely - My RV uses a fairly consistent 200 watts while I'm inverting - for my fridge and TV. Over 8-10 hours asleep it's only the fridge which shouldn't be 200 watts the whole time, it idles at either zero or 40 watts.... I should be above 50% capacity, having only pulled about 2500 watts from the nearly 10k that the battery array should have contained. But was instead reading around 12.1v under load, nearly depleted!

So I don't think these Interstate GC2 batteries were very good. I've since swapped them out for "unsuitable" group 25 starting batteries, and with the SAME USAGE they haven't used ANY water in months, and reading (under load now) around 12.5v. Yes the total capacity is less (on paper only 300 amps instead of 880) BUT I haven't seen where these are suffering anywhere near what the golf cart batteries were.

If there's any issues, then they go back and I'll think about doing something different, but I look at it as the warranty length is worth it. I should have dumped those GC2 at the first sign of trouble.

[Mark_K5LXP]

Originally Posted by geordi

I had 8 GC2 batteries for a total of 880 amp hours at 12v. ... they used a ton of water.

Then your setup was overcharging them. The only time electrolyte is dissolved is at voltages north of 14V, during absorb phase. You can't avoid a bit of water loss to reach 100% charge, but with a properly set and temperature compensated setup the net water use should be minimal.

I should be above 50% capacity, having only pulled about 2500 watts ... was instead reading around 12.1v under load, nearly depleted!

You're interpreting that wrong. 12.1V *under load* is about 75% capacity, not "nearly depleted". The terminal voltage for SOC *under load* is very different than for when the battery is static, not under load. Even for static SOC, 12.1V is still around 50% SOC, not even close to "nearly depleted". The full voltage range for 100% of the battery's capacity is 12.78V down to 10.5V. Many recoil in horror of the idea to run your batteries down to 10.5V but that's what they're made to do.

Mark B.
Albuquerque, NM

[Persistent]

Rr,

Thank you for posting your solution. I think you made an excellent choice for your situation!

Many posters don't seem to get the years of experience you have behind your selection.

I think you should avoid drawing the sealed flooded cell batteries down flat, but for your intended use, that is unlikely.

Just fully charge before storage and disconnect. Monitor terminal voltage periodically until you know how long they will stay above 12.4 volts during storage.

I wish you good luck and happy trails ahead!

[diesel-dan]

OP: those are not sealed batteries. They are Flooded wet cell lead acid Maintenance Free batteries. They have a vent and a cap (from the picture), so are nothing like an AGM, and should be installed in a vented to the outside enclosure.

I wouldn't have those installed in one of my rigs without being in vented enclosures... Oh and from your pic, the inverter is 3000 watts (from the label).

But hey, a lot of things work, until they don't...

[geordi]

Originally Posted by Mark_K5LXP

Then your setup was overcharging them. The only time electrolyte is dissolved is at voltages north of 14V, during absorb phase. You can't avoid a bit of water loss to reach 100% charge, but with a properly set and temperature compensated setup the net water use should be minimal.

You're interpreting that wrong. 12.1V *under load* is about 75% capacity, not "nearly depleted". The terminal voltage for SOC *under load* is very different than for when the battery is static, not under load. Even for static SOC, 12.1V is still around 50% SOC, not even close to "nearly depleted". The full voltage range for 100% of the battery's capacity is 12.78V down to 10.5V. Many recoil in horror of the idea to run your batteries down to 10.5V but that's what they're made to do.

Mark B.
Albuquerque, NM

My setup is using all Victron equipment, and I had programmed the charge voltages from Interstate's own charts. As it happens, I haven't changed the voltages since changing to these group 25a batteries, and they don't seem to have suffered anywhere close to the same water loss. The last (first) time I topped them up was in early February, and just checked them a few days ago, still full.

With the GC2 batteries, the starting performance even of my generator was not impressive (the main engine definitely struggled even when they were full) so I'm willing to believe that maybe one or more had a bad cell. But

Is there a voltage-under-load chart that you know about that you can share? I'd HAPPILY use that to know what I'm actually looking at, b/c I've always wondered about that, and it's impossible to be truly off-load with them powering the entire coach.

Suffice to say - I'm much happier with the performance of these Group 25a, and comparing the ratings between these, a group 25 with more CCA but less RC next to them, and a Group 25 Marine that had way less CA but only slightly more RC.... These might not be true "deep cycle" but they are working well and I have not yet found the bottom on them so I don't know how long I could feasibly drycamp with only my solar to bring them back.