The Offshore Voyaging Reference Site

Gel Batteries a Winner?

While researching for an upcoming article I noticed something interesting:

Victron rate their Long Life Gel batteries at 2500 50% cycles, as against their AGM Super Cycle Battery at 1000 cycles, and not a lot less than their much more expensive lithium batteries at 3000 cycles.

Could it be that the pivot away from gel cells toward AGM that occurred in the sailing community some 20 years ago was a giant mistake?

I do know that both members Dick and Ginger Stevenson, and Phyllis and I, had very good service from Prevailer Gel batteries back in the day.

Now before we get too excited it’s important to note that gels have one Achilles’ heel: they can’t be conditioned to get rid of sulphation from being left in a partial state of charge, as is common on cruising boats.

Hit ’em with any more than 14.2 volts and they are toast in very short order.

Whereas AGMs from both Victron (14.9V) and LifeLine (15.5V) can be charged at higher voltages to blow off that nasty battery wrecking stuff.

Still, these days, with cost effective and efficient solar, fully charging a lead-acid battery regularly without shore power is a lot less of a problem than it once was.

Should those who want to avoid the expense and complications of lithium be thinking of poor old neglected gels?

Don’t know, but it’s worth thinking about.

Anyone out there using gels?

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Matt Marsh

Not in the boat, but I’ve been using Schneider/APC gel cells in the server & network racks for 9 years, and am severely unimpressed. This is not a difficult life. They are trickle charged at float voltage for 60 days, then discharged to 50%-60% in 10-20 minutes, then charged back up over 6 hours and put back on float mode. And yet I don’t think I’ve ever had a pack survive more than 4 years; they average closer to 2-3.
That doesn’t mean I’m condemning gel cell technology out of hand, but I’d need a lot of convincing to give it a ranking position on the list for a cruising boat.

Matt Marsh

If I ever get the chance to rip out the APC stuff and start from scratch, then yes, I’d use AGMs.

My thinking here is more along the lines of “if a $4bn/year company, widely regarded as an industry leader, sells me a $10,000 complete integrated solution — charger, inverter, controls, batteries, the works — designed and warrantied for one specific purpose, and they still can’t get the gel cells to last through a full US presidential term, why would I trust myself to somehow do better with the same technology?”

Hans Boebs

Hi John,
do you remember my post about my Sonnenschein gels and the manufacturer’s recommendation of conditioning them ?
On my boat I always had and still have excellent service from my Sonnenscheins even without ever equalizing them. Achilles heel ? Really ? At least not all of them.

Hans Boebs

Hi John,
here’s a copy of part of our conversation from December 2020.
The link is still valid and they explicitly recommend equalizing their gels every 3 month at 15,3 volts

……Another thing I noticed when browsing through the datasheets of my gel battery: The Sonnenschein dryfit solar series can and apparently should be equalized ! Although I’ve never done that. Look at this link, scroll down to page 5ff and look at 2.6 and 2.11
Kindest regards

 December 19, 2020 9:03 am

Hi Hans,
That’s interesting about the Sonnenschein gells and completely changes my thinking on gells. Thanks for pointing out. I will dig deeper when I get a chance.

Hans Boebs

HI John,
but the complicated stuff that you correctly describe starts only if the system voltage is above 48 V ? At least that’s how I read the text. If system voltage is 12 V as in my case all it takes is charging with constant voltage of 14,4 V at unlimited amperage for max. 48 hrs. And see that temperature doesn’t exceed 45°C.

Although I can see a contradiction between the text in 2.6 and the description 3) of Fig.1 where equalizing starts with15,3 Volts, albeit at -20°C.

Be it as it may: I get easily 10 to 12 years of life out of my gel battery. Yes, it works for me.

Hans Boebs

That’s right of course, and I was slightly afraid that you would ask for number of cycles, let alone their depth. While at home my gel has a very easy life, given the solar paneI. Even with the fridge running the 200 Ah battery is hardly ever down more than 10% off the top and will always be fully charged by noon at the latest. I never connect to shore power at my home berth. I cruise for 3 month a year and while that’s different usage, depth of discharge is never more than 50% and that’s on rare occasions only. So I guess it’s in general a rather undemanding life for any battery.
Anyway, like Dick I like to stick with what works and not bother. I just felt it “unfair” to the gels to say they can’t be equalized.


I’m using the Victron gel battery as a UPS for my boat’s navigation systems. The main battery bank is a 7200wh 24v Lifepo4, and the 12v systems are powered by DC to DC chargers that are connected to the Victron Gel. This setup ensures that my boat won’t “black out” if there’s a problem with the BMS or if something is detected by the BMS.

I’ve had good experiences with discount brand gel batteries in the past. I used them almost daily for three years before switching to lithium, and there was no noticeable degradation in performance.

In my opinion, the Victron gel batteries are a great value for the price, and it’s worth it to spend a little extra on them instead of going with the cheaper brands. They provide a reliable backup for the 12v navigation systems on my 38′ boat.

Dick Stevenson

Hi John and all,
Interesting report: I look forward to learning more. (I like Victron, but the picture makes the terminal look wimpy and not up to accepting a couple of high amp wire cables: any info from actual use?)
Being an essentially lazy cruiser and not overly enamored of my technical skills, if I find something that works for me, I go out cruising.
And gels have worked for me for decades now.
Prevailer batteries were my first gels and then were hard to find. Then East Penn were/are my choice in the US while Sonnenschein was my choice in Europe for the years I was over there and could get them. All have given good service and survived the occasional abuses that I have inflicted on them. I get between 5 and 7 years before replacement.
Two winters of covid-related occasional neglect while Alchemy was on the hard in Newfoundland and I was restrained from visiting in the US led to me wanting a new set when settled finally in the Great Lakes. Alas, finding East Penn gels in northern Michigan proved difficult, but a call to East Penn indicated that NAPA gel cell batteries were re-branded East Penn gel cells: exactly the same. No spec changes.
We have 2 seasons with these NAPA batteries and have been happy with them. Another way of putting that is that, aside from keeping them charged, I have not needed to think about them.
My best, Dick Stevenson, s/v Alchemy


The terminals on my Victron gel are the flat bar type that allow for a through bolt. This gets you a very secure way to attach the primary leads. Arguably superior to the post and m8 flush terminals. Primarily because they are almost immune to over torquing.

Dick Stevenson

Hi John,
No, no solar. Valiants do not have a user-friendly real estate for solar, especially with no arch, so I just figured, rather than a whole additional system, I would run the genset a short while longer. I might make a different decision nowadays. And since living aboard, I did not have to worry about lay-ups and the need for some sort of trickle charge.
For years we were at anchor primarily charging with a DC genset from 50 to 80% SOC with occasional reaching fully charged when motoring for a longer distance. In Europe that changed as access to the things we were interested in pretty much necessitated being in marinas or going to town wharves. With shore power, we were fully charged regularly.
These judgements are very subjective and subject to many variables, but I did not have the sense that the battery bank performance or lifespan was different with the different charging styles.  
In the Great Lakes, with these new East Penn/NAPA gel batteries we are doing a combination: periods of anchoring and then visiting towns with facilities. We shall see– and happy to report.
My best, Dick
Ps. I have always wondered, and never felt completely comfortable with, the long periods (over-wintering) where we would be plugged-in.  I know the battery charger algorithm goes to float, but even so, it felt like the battery would be better off “working” and being discharged (to some extent) every now and again rather than just sitting at float for months on end. I know you have mentioned something along these lines, but other than that, I have not heard anything.