GEL versus AGM

[BlunderLust]

I watched a video were it was suggested the max DOD of Gel Cell is 80 percent versus 50 percent of AGM and the charge time for both is around 2-3 hours. A max DOD of 80 percent would put the Gel Cell in the league of the LITHIUM batteries.

If anyone has used the GEL Cell batteries does an 80 percent max DOD seem correct? Also, does a charge time of 2-3 hours sound right?

I am thinking I might be using a HONDA or YAMAHA 2000 WATT generator to charge the batteries while boondocking.

[pianotuna]

C = capacity.

c/2 = 1/2 of the capacity in amp-hours. A rule of thumb for a continuous load.

The shop guy was not too knowledgeable.

[Naio]

Pnichols, my ex650 bro :). That's good to know that the 650 dc output is not too much! How many amps is it, do u know off the top?

Don, I am sure you are right. I went from 2x33 to 2x90. The switch from agm to gel was just because that was what I came across, used :).

What is c2? The machine sometimes pulls over 100amps, briefly. Battery shop guy insisted that was ok for the 33s, but I have had no more problems since the move up to the 90s.

[pianotuna]

Hi Naio,

I'm going to assume that the gels were 12 volt. So you went from 33 amp-hours up to 180 amp-hours.

A 33 amp-hour battery at c2 would only be a 16.5 amp draw. The shaved ice was exceeding that. So if you had moved to 90 amp-hour AGM they would have worked just as well (or perhaps even better) than the gels.

Naio wrote:
I have a pair of 90aH MK gels that are 10 years old, still doing great, in my shave ice machine.

I killed a lot of 33aH AGMs in the same machine, before I figured out that its occasional high-amp draws were the problem. High amp definitely can destroy AGMs.

[pnichols]

Naio wrote:
I guess I gotta go alternator -> AGM -> inverter -> charger -> gel, yeah?

Naio, or .... you could go:

A) Honda EX650 120V AC outlet -> 3-stage charger -> gel,

OR

B) Honda EX650 12V DC outlet -> gel.

Either A) or B) would not supply enough current to cause TRA of your gel .... unless it's a REAL SMALL gel battery. 🙂

[Naio]

Thanks for the warning, Mex. I have set up to charge my ice machine (gel batteries) from my van alternator, but now I know not to.

I guess I gotta go alternator -> AGM -> inverter -> charger -> gel, yeah?

[MEXICOWANDERER]

It is incredibly easier to initiate TRA in gelled electrolyte batteries. No battery should be subjected to arbitrary voltage high amperage charging. Bulk charging maximum voltages are stated for a reason.

Grab your IR thermometer, and employ very high amperage across an AGM then a Gelled electrolyte battery. Scan the cells for temperature variance...

Ohmygod...

[Naio]

I have a pair of 90aH MK gels that are 10 years old, still doing great, in my shave ice machine.

I killed a lot of 33aH AGMs in the same machine, before I figured out that its occasional high-amp draws were the problem. High amp definitely can destroy AGMs.

[beemerphile1]

MEXICOWANDERER wrote:
GEL
Look up the definition of THERMAL RUNAWAY

Thermal runaway can occur in any VRLA battery, either gel or AGM.

[pnichols]

MEXICOWANDERER wrote:
GEL
Look up the definition of THERMAL RUNAWAY

Hmmmm ... I've done a lot of research on the dangers of thermal runaway with respect to the charging of AGM batteries.

I wonder if GEL battery thermal runaway is less or more dangerous?

[MEXICOWANDERER]

GEL
Look up the definition of THERMAL RUNAWAY

[wa8yxm]

christopherglenn wrote:
Almost all UPS's use gel cells not because they are the best, but because they don't spill.

In a UPS you can take days to recharge so you can baby that.

But most of the UPS units I've seen have gone to AGM.. Better and about the same cost. Have not actually seen Gel in anything I use in a long time.

[beemerphile1]

I use MK Battery group 24 gel cells because I get them free. They are cycled out of mobility scooters when 18 months old. For my use they still have years of life remaining.

The ones I get are 73.6a @ 20hr rate and weigh 51.5# each. They definitely are deep cycle batteries.

I don't really concern myself with any special treatment. I treat them just like flooded batteries and recharge at 50%.

There is a risk of charging a gel too fast/hot and creating permanent pockets like stated previously.

[landyacht318]

The Sailor's peeling those green banannas are hardly dimwits, and are dang impressed with the taste.

http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-...

One guy who has all the special tools for precise capacity measurements says that at cycle 765, his 400AH lifepo4 bank is still delivering over 400AH

Post 5136 on that linked page thread, page 343.

[MEXICOWANDERER]

Most RV stuff I buy now has a lifetime guarantee. Come to think of it I starting shying away from buying green bananas.

[time2roll]

landyacht318 wrote:
This is likely my last lead acid battery for deep cycling. I got my eyes on 4 100AH Lifepo4 cells.

Only trouble with Lithium is no brown out warning. Controller will just cut power instantly at some point.

I keep thinking a backup AGM to be used in conjunction.