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What brand of charger do you use to equalize batteries

Sep 26, 2008
Hunter 340 Wickford, RI
I have 3 Group 24 Interstate Wet Cell Batteries I would like to equalize. My basic run of the mill car charger does not have a setting or voltage for equalizing.
I do have a bench top Battery eliminator though which does have various ranges. Curious to see what others use, techniques and if you would use this battery eliminator.
Thank you for the information.



Jun 1, 2004
Catalina 27 Mission Bay, San Diego
Not to be judgmental, but with such a modern design boat it appears your battery charging system is from the pre digital era. A hard wired, dedicated on board "smart" charger is what you should be thinking. You might also want to upgrade to larger batteries. My 1977 27 footer, for instance, has 2 Costco wet cell, group 27 batteries that are maintained with a 20 amp Tru Charge 3 stage smart charger. It's literally plug and play. It is able to handle 2 separate banks, I have a house bank and a motor bank. I normally get 42 mos, or more from these basic batteries.
My system was installed by the previous owner, probably in the early 90's... I acquired the boat in 99, have never had a problem.
There's a lot of savvy electrical people on this forum that I'm sure can give you some awesome, specific advice.
But honestly, and I mean this in a very encouraging way, now is a good time to upgrade the whole system.. charger, larger batteries and a proper shore power system installation. Good luck.
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Sep 26, 2008
Hunter 340 Wickford, RI
I agree with you, your not being judgmental at all. This would be for batteries out of the boat, for the winter lay over. My wording wasn’t clear. My batteries are 2 years old and I’m just looking to maximize their life during the winter.
Oct 22, 2014
CAL 35 Cruiser moored EVERETT WA
With a resume like this:
Hunter 340 Boy on a Dolphin 2000 RI USWickford, RI 36' Silverton in 1976 Narragansett Bay - RI Sound Male Marine Consultant / Surveyor / Vessel Security
I find the question a little odd. As Joe identified, the images show a machine out of the 70’s. The management of batteries has come a long way since then.

Sterling, one of the advanced charging systems uses a 15.5 volt charge for 4 hours for equalization. The amperage is internally controlled yet limited to the unit output.

Is it possible to use the hardware you have sure if it is in good service? Do you have the basic electrical knowledge to operate the hardware for this task? If the answer is no to either of these questions it would be unwise to proceed, in my opinion.
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Sep 26, 2008
Hunter 340 Wickford, RI
I have a Pro-Tech 4 onboard system. It’s a 2000 340. During the sailing season I’m fine with charging and maintaining the batteries. This is for battery maintenance while in the garage over the winter. I thought it was a good idea since they‘ve never really been equalized.
Feb 14, 2014
Hunter 430 Waveland, MS
This is a good example of a boat battery charging curve.

The "Recondition" = Balancing on two parallel batteries of same age and type.
charging curve.jpg

Note the Current flow or Sustained Amps and time on "Balance"
Sep 26, 2008
Hunter 340 Wickford, RI
Jssailem, I thank you for the compliment. I have many “older” tools from my days of repairing cars in my Sunoco Gas Station, which is now a hair salon, that I still use for my 1952 MG. But not a new battery charger with the equalizing feature. I read where many are equalizing their batteries but no one says how or with what.
It may be an odd question but this information can be helpful to many who want to do this, who need an outline and name of a tool.
Oct 22, 2014
CAL 35 Cruiser moored EVERETT WA
Here is a practical review of "Equalization / Reconditioning".
It is by no means a trouble free experience.

You will be "boiling" the battery to expose the lead that has been covered by lead sulfate crystals. This is a chemical reaction that you trigger by the heavy electrical overcharge. There will be heat generated by the chemical reactions. You will be bubbling hydrogen and oxygen out of the battery tops. Do you remember High School Chemistry where the teacher exploded soap bubbles?

It is done in Auto shops. Usually in a space where if the battery explodes it is not a life threatening event.
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Nov 3, 2018
Cape Dory, Albin 300ms Motorsailer, Vega Baltimore
I can’t comment on your charging set up but you may want to check the data sheet or user manual on the need for equalization. Below is what Trojan recommends for their batteries.

5.3. Equalizing (flooded/wet batteries only)
When batteries are used in a battery bank, over time some of the batteries can drift to a lower state of charge than others. This charge imbalance can lead to sulfation and premature battery failure.
In order to ensure that these charge imbalances are corrected, a process called “equalization” is used. Equalizing is an overcharge performed after fully charging deep-cycle flooded/wet batteries. An equalizing charge prevents electrolyte stratification and reduces sulfation, which are leading causes of battery failure. Trojan recommends equalizing for 2-4 hours in the following situations:
î Periodically (every 30 days)
î When batteries have a low specific gravity after charging (<1.235), or
î When the range of specific gravities between cells is > 0.030 points
î Reference Section 9.3 for instructions on specific gravity measurement.
W A R N I N G! Deep-cycle AGM or gel batteries should NEVER be equalized.”

If you take them off the boat you may just need to trickle charge, or save your back and fully charge them on the boat, disconnect and wait for spring. The batteries won’t self-discharge as quickly in the cold.
Jan 1, 2006
Slickcraft 26 Greenport, NY
I don't know anything about battery equalization but I can't help noting the irony of attaching your batteries to a "Battery Eliminator." Wonder who did the marketing for that device?
Jun 21, 2004
Beneteau 343 Slidell, LA
If your batteries are only two years old, do they really need to be equalized?
If you simply want to maintain the charge over the winter, perhaps a new micro processor controlled charger could be used once a month at home to keep them from discharging. Smart chargers for home use can be had for $100 or so.
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Sep 25, 2008
Alden 50 Sarasota, Florida
I don't know anything about battery equalization but I can't help noting the irony of attaching your batteries to a "Battery Eliminator." Wonder who did the marketing for that device?
I do know a little about equalizing batteries and this isn’t it. I sometimes marvel at the ingenuity of people to do things to save a few bucks which invariably costs them a lot more later.
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Nov 13, 2013
Catalina 34 Tacoma
I bought an non-marine battery charger on Amazon with a desulfation cycle and equalize function. Cost about $80 I believe. Tried it on my two 8 year old group 27 wet Die Hards. Didn't seem to make any difference. I'm still using those batteries. I have a 32 y/o 15amp charger that I kick on periodically when voltage gets to ~12.4. I hear to many stories of smart charger failures and prefer the dumb charger but use my brain.
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Mar 23, 2017
Belliure 41 Now on the Chesapeake
I use a research grade Lambda power supply that is programmable for both current and voltage. That power supply will control voltage to the nearest 0.01 volts, and the current to something like 0.1 amps. You don't need that precision for the amps, but you should be able to control it to about 0.5 amps. There is an IEEE standard that talks about equalization, I'd have to go dig up the exact number, don't recall off the top on my head.

@sailcapt340 - for your flooded lead acid batteries, the equalization voltage should be between 15.6 (IIRC) and 16.2 volts. I don't remember if the the lower side is 15.6 or 15.8V. I just set my power supply to 16.0 volts. One thing that has never been clarified for me, is when is the "end of cycle" for the equalization phase. All chargers I'm aware of that claim to perform equalization use time as the end point.

As far as if the device you've got would work, I'd check to see if the voltage output is sufficiently stable and if it falls within the range stated. One concern is the current output, which seems a bit on the high side. When running it, be sure to check the temperature of the battery, it should not get hot. It it begins to get hot, turn your device off. I control heat by controlling current.


p.s. I just looked on ebay and there are numerous options - here's one that looks like it would work well.
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Jun 11, 2004
Oday 31 Redondo Beach
Maine Sail mentions using a DC power supply to equalize batteries in this article:



Jul 10, 2007
Seidelmann 34 Atlantic Highlands, NJ
I use a VOLTEQ HY3020EX DC Power supply, using a techniques that Mainesail outlined years ago.
May 24, 2004
CC 30 South Florida
Yep, that is a battery "eliminator", literally. What you have is a manual bulk charger that unless monitored very closely could very easily overcharge and damage the batteries. I could see one use for that charger, when a battery is so depleted that a modern smart charger would fail to respond the old work horse could surely put some charge in it.
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