Mighty Max high-rate GEL Hybrid tests

Substrate

Solar Addict
As promised to another I picked up a so-called Gel/AGM hybrid with a clear top so I could check things out with testing. I'm used to higher-end types like Mk/Deka Gels for standby, so I was intrigued.

My whole interest was piqued by seeing AGM like CV voltages being used on these things, when that is a big NO-NO with a true classic GEL, where one should never exceed 14.1v. What's up with that? If I wanted an agm, I would have gotten one.

And of course seeing things like AGM / GEL / MF on the same cased vrla in my world meant three different types! WHAAAT?

I didn't want to spend a lot of money on something I'm going to destroy testing, and I wanted it small to make it easier and faster to detect problems. So I found this Mighty Max high-rate Gel hybrid. (It is a GEL battery, but built like an AGM which gives it a few interesting capabilities)

Here is what I picked up - remember this is a sacrificial motorcycle starter - not something bigger I might pick up later on. Just for the clear top.


It arrived with a relatively high 13.1v OCV. Gave it a standard charge with my Optimate just to be on the safe side. Passed all tests prior to charge, and finished the 12-hour after-charge test just fine. It's an Optimate charger thing.

Funny: So I removed the top flat clear plate to check it out. Bummer - what looks like sulfation is actually the whitish gel material all over the place. So I guess watching the natural sulfate-desulfate process during the charge procedure is out. Ok, no biggie. During the first discharge, 3 of the caps blew off with a huge pop! This was the result of the initial manufacturing filling procedure. An air bubble or two got released about an hour into my first discharge. I put those caps back on!

After a 30% discharge, this time instead of the Optimate charger, I put it on a more standard CC/CV charge of 14.4v with a different dedicated charger, which for most Gels in the past, is the kiss of death.

Well - at 14.4v CV, what I noticed is that the gel material that seems like a little extra on the top of the plates, started to slowly melt like candle wax and appeared as a more clear uniform liquid-like covering! However, I expected some complaints like the sound of rice-crispies and perhaps some squealing. None heard. I wish I had picked up a stethescope! I always forget to put this in my battery-doctor bag. Seriously.

So I let it rest for an hour and did another 30% discharge. But this time, I recharged at a much lower 14.1v CV, which of course meant that that absorb (tail current if you want to think of it that way) took much longer to complete. This time, the gel which had seemed to re-congeal back to white, didn't seem so um, melty - and stayed looking like the gel consistency I first received it with.

No complaints, but I am cycling it a little bit now just for fun. Not seriously, because after all this IS a starter, and most likely has a higher acidic content than what you'd get with the normal storage versions.

I'll need a lab or another lifetime to make an accurate prediction, but I'll cut to the chase:

  • The agm-like construction of the gel allows it to have a lower IR. Ok fine. Higher voltage under load.
  • Treat it like an AGM with high CV voltages above 14.1v, and you'll get agm-like cycle life, not the boasted typical 2X the cycle life of a gel! Limit inrush current to no more than 0.15 to perhaps 0.2C max.
  • But unlike in the past, treating the gel hybrid like an agm is not an immediate death-sentence. You're just cutting out some of the extended cycle life you got a gel for in the first place.
  • Temp-comp should always be used with a remote probe on a battery terminal, especially for classic Gel, and while not ideal, you may not be punished immediately for using only ambient from your SCC.

DRAWBACK: Like all vrla's like gels and agm's, engineering your system so that it doesn't sulfate by undercharge in a daily-cyclic routine is tough. Even tougher with the lower CV voltage of 14.1v of a gel! So - unless you live and die by your slide-rule and pocket-protector, for the Gel Hybrid, it is probably better to use it in a standby, or weekend-warrior, random type of application where there is plenty of spare time in the rest of the week for it to be fully charged to fight sulfation walk-down due to undercharge.

The most immediate benefit might be for the consumer's devices to have a wider range of CV's to operate in, and not result in immediate overcharge, or undercharge (like charging an agm at low CV's) due to poor consumer build devices, or things like wall-wart component aging, high-resistance contacts or the like.

So I'll hammer on this thing without being too outrageous, and report back. No, it's not an MK/Deka gel, but then again, it doesn't cost like one.
 
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Substrate

Solar Addict
But is it a case of too-little-too-late?

Let me be the first to derail the topic in comparison to hobbiest-level LFP with some oversimplified ballpark figures. And this is like-to-like (hobbiest level stuff), not any sort of comparison to a MK / Deka Gel out at sea where your life may depend upon it.

I also have a 24ah LFP Talentcell. I can use all of it. An equivalent Gel would be a 50ah unit, with the prevailing wisdom of not discharging more than 50% capacity from it each cycle. Even less discharge is better.

Roughly the same cost.

Mr. Peukert: With the Talentcell, Mr. Puekert has been evicted from the premesis. Full voltage during nearly the entire discharge cycle. And just as efficient on recharge. I am limited to 0.5C charge with the Talentcell, and if I wanted to get the most life out of the Gel, 0.1 to maybe 0.2C max. Take a look at the discharge-under-load time figures for lead-acid, and you'll see that Mr. Peukert will put the brakes on your fun if you are expecting a long discharge times at high levels of current.

Sulfation worries: NONE with the Talentcell LFP. I don't have to recharge to full ever. I don't worry what level they are sitting at, other than not being near fully discharged and ignoring it for a long time. The Gel - like all lead acids, they need to be kept near full charge as much as possible to avoid sulfation walk-down.

Solar: just these two comparisons alone are a major factor when using solar!

Problem - The Talentcell does have an internal BMS circuit, and that can be a possible point of failure, leaving you with good cells with nowhere to go. (unless you are a diy fixit type).

Up-front cost: At anything much less than 100ah for the Gel, where unit costs increase (like nobody would think of making some serial-parallel 48v house-bank out of 11ah starter batts!) from sheer cost alone! NO bang for your buck if you start banks out with small capacities.

Maintenance relationship: Unless you are retired or have the time to spare, having a maintenance relationship with lead-acid to keep them heathy may not be your thing. But if you are, then maybe you have the time, or in a twisted kind of way, it's like having a pet and wanting to nurture them. So it can be done, just depends on your nature. Then again, the LFP Talentcells are boring when seen in this light.

Weight: Sure enough - going big and humping around even a 55ah Gel is not something I look forward to at my age. :)

Still, I find working with batteries of all chemistries fun! I'm still on the fence about picking up a larger Gel since I've never used them in a daily cyclic application before. What will I learn? Maybe that's the whole point....
 

Substrate

Solar Addict
Initial run - seems normal.

After 5 cycles to make sure I built up just a little formatting capacity, did a 50% discharge (5.5A as measured on a dinky inline Powerwerx meter) at .05C rate. 79F. After 12 hours, the OCV was 12.34v (easy to remember) as measured on a Fluke.

While measuring battery voltage says nothing about a battery's state of health, this being brand new fell into the ballpark of what a Renogy 100ah gel has in it's documentation:


Ok. Tomorrow we'll just pop it outside with a 40watt panel (2.2A) and either my little Morningstar Sunguard 4.5a controller, or a 6A Sunsaver. The potted Sunguard defaults to 14.1v CV, and the jumper for "sealed" on the Sunsavers is also 14.1v. So easy match.
 

Substrate

Solar Addict
Hilarious!

Came out to check on solar charge, and found all the rubber caps popped off the cells. Note to self: Super-glue that flat clear cover down so this doesn't happen again. :)

That flat cover plate was originally held down with a little factory glue, but I pried it off to take a closer look. Heh, if you do that, better find some way of securing it back later.

This is the starter-type batt where this is possible. Pretty sure this is not possible with the larger ones.
 
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