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From: Randolph Stroschein (no email)
Date: Fri Aug 20 1999 - 12:38:36 EDT
I beg to differ. There are several advantages to gel over flooded (wet).
1) They hold their voltage longer through the discharge cycle than wets. This translates into a lower rate of discharge as you approach the 50% level, because to supply, say 60w, takes only 5A at 12v, but takes 5.22A at 11.5v.
2) They tolerate a much greater level of discharge. Wets should not be discharged below 50% (on a regular basis, once or twice probably is no big problem). Gels can regularly discharge to 75%.
3) Gels have a much greater USABLE capacity (largely due to 1 & 2 above). A local chandlery, known for their technical expertise, did some testing of their own to satisfy their curiosity. They took 2 different manufacturer's wet cells and a Pow-R-Surge (Prevailer in the USA) 8D's and ran several iterations of the 20 hour discharge test on them. The wets were rated at approx 225AH and the gel at 200AH. After several discharges, they discovered the wets only provided approx 175-185AH and the gel 220AH !!
This leads to the proper capacity comparison of 50% x 185AH vs 75% of 220AH. In other words, the wet cells yielded 92AH USABLE capacity and the gel 169AH. If you apply that relationship to physical size and sticker price, you get a whole different appreciation of value.
4) They are MORE resilient to abuse. You flatten a wet cell a few times and it is NOT coming back. A gel doesn't like this either, but they can be crowbarred multiple times and returned to full life. In fact, this is the recommended way to rejuvenate one if it has been severely abused by many, many, many very shallow discharge cycles (hysterisis (sp?) developed).
If you take all this in addition to the mounting flexibility (don't have to worry about charging gasses), minimal/no maintenance (a big thing in my mind), safety (no acid spills, like during a knockdown), and ability to accept a MUCH higher charge rate (meaning with a high cap alternator, reduced run time to recharge), the gel represents a far superior solution.
The only potential concern IMO is that gels are more sensitive to correct charging regimen. High/incorrect charge voltage can wreck them faster then wet cells. However, in this day and age of sophisticated chargers and regs, that should not be a problem.
I have no comment on AGM's as I have no direct experience with them, but from what I've read and heard, everything said above about gels applies to AGMs, but better/more. When I have to replace batteries, I will likely go AGM.
Disclaimer: all battery manufacturers are NOT alike. The above is not intended to include extraordinary wets like Surrette. Gel quality varies significantly and I have been referring to East Penn batteries, the best AFAIK. I am not affiliated with any etc etc etc.
All the above is based on my own research and experience. I have 3 x 8D East Penn gels, with a 147A Ample alternator, Smart regulator, EMON II, and Heart Freedom 10. Fantastic system, I am most pleased. It has been installed and running for approx 6 years.
Regards.....Randy
mv Island Time
----- Original Message -----
From: Pierre Mitham <>
> Sandra,
>
> Unfortunately your comparison of gel vs. Flooded batteries is incorrect!
> The primary advantages of Gels over flooded are mounting options, and charge
> acceptance. They certainly don't last as long as a comparably priced
> flooded, they can't be brought back to life as reliably. Gel's can however
> survive user abuse more often. Flooded batteries are far supperior in most
> cases,IF you learn how to take care of them (water them, measure specific
> gravity each month, and equalize them occasionally) dollar for dollar, you
> get more Ah's per $ with a flooded battery, a little common sense and flood
> batteries will last many years. People who replace marine batteries every
> season on 2 are usually murdering there batteries. draining them too far,
> and using an automotive charger to charge (really bad!)
>
> Pierre.
>
> ----- Original Message -----
> From: Flying_Cloud <>
> To: <>
> Sent: Thursday, August 19, 1999 10:48 PM
> Subject: RE: lv-ab: Battery Charging: How Charge Large House Bank?
>
>
> > I have a similiar setup; and my responses reflect on how I'm doing it. I
> > have a Lehman as well (135hp); Heart 2500 (just upgraded to the new 3000);
> > Link2000r (Cruising Equip upgraded it for me free of charge); Balmar 200
> > amp; Had 4 gel cells 8Ds (banks 7 and 8 years old so upgraded to AGMs).
> > Here are my thoughts.
> >
> > Why are you going with golf cart batteries? Regular lead acids can only
> > absorb 25% the rated amp hour capacity; gel cells 75%; and AGMs 100% of
> > capacity (AGMs can take twice as many deep cycles as gels which is way
> more
> > than reg lead acids). Also AGMs are 155 amp/hr per 8D which is 55 more
> > amp/hr than a gel 8D. (I paid $134 per 8D) Going with regular lead acid
> > rather defeats the purpose of going with a high output alternator because
> > they cannot absorb the amp the high-output the alternator puts out. If
> you
> > are insistent on going with the golf cart batteries - save yourself a lot
> of
> > money - and put a smaller capacity alternator on it.
> >
> > I have a Lehman 135 (almost the same as the 120) and I had (because the
> > engine is out of the boat right now) mounted the Balmar 200 amp
> alternator -
> > only I use only one belt. I checked with my mechanic at the time of
> > purchase and he seemed to think this would be okay - just that I will go
> > through the belt a bit faster (since I never gone through one - seemed
> > reasonable to me). I have only done an overnight passage since then so I
> > have no real data to support the mechanics advise. You know how it goes -
> > there are more opinions that you know what.
> >
> > Delco make a 140 amp which is single belt driven as well, as I'm sure
> other
> > manufacturers do too. I had one of those too. Actually in practicality,
> the
> > 140 amp alternator was sufficient for my draw on a 54 footer - even with
> the
> > 3/4 hp ac refrigeration running on top of the stereo and all the cruising
> > load etc. (the partial flooding is the reason for its demise).
> >
> > Question re the alternator on the genset: I presume you were only talking
> > about doing this if you could not put the high output alternator on the
> > engine. I I see no reason why you have to buy another charger - go with
> the
> > alternator on your engine even it's a bit smaller than you'd like - for be
> > my advise. As for an alternator on the genset - why have one? - when the
> > engine is not running why not use the generator to run the Heart 175 amp
> > battery charger on the inverter to do the work? This is what I've been
> > doing.
> >
> > Anyway you can add this to your list of opinions.
> >
> > Sandra
> >
> >
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