The Offshore Voyaging Reference Site

Equalizing Batteries, The Reality

JHH5-12590 Fully charging your batteries after each discharge on a live-aboard cruising sailboat is simply not practical. Instead, most of us will cycle our batteries between 50 and 80% of their capacity. The bad news is that this will ruin your lead-acid batteries (regardless of type) in a distressingly short time due to sulphation.

The Solution

But there is an answer to this problem: regular equalization, a process where you deliberately overcharge your batteries for a specified time and voltage to remove the sulphation.


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More Articles From Online Book: Electrical Systems For Cruising Boats:

  1. Why Most New-To-Us Boat Electrical Systems Must Be Rebuilt
  2. One Simple Law That Makes Electrical Systems Easy to Understand
  3. How Batteries Charge (Multiple Charging Sources Too)
  4. 5 Safety Tips For Working on Boat DC Electrical Systems
  5. 7 Checks To Stop Our DC Electrical System From Burning Our Boat
  6. Cruising Boat Electrical System Design, Part 1—Loads and Conservation
  7. Cruising Boat Electrical System Design, Part 2—Thinking About Systems
  8. Cruising Boat Electrical System Design, Part 3—Specifying Optimal Battery Bank Size
  9. Balancing Battery Bank and Solar Array Size
  10. The Danger of Voltage Drops From High Current (Amp) Loads
  11. Should Your Boat’s DC Electrical System Be 12 or 24 Volt?—Part 1
  12. Should Your Boat’s DC Electrical System Be 12 or 24 Volt?—Part 2
  13. Battery Bank Separation and Cross-Charging Best Practices
  14. Choosing & Installing Battery Switches
  15. Cross-Bank Battery Charging—Splitters and Relays
  16. Cross-Bank Battery Charging—DC/DC Chargers
  17. 10 Tips To Install An Alternator
  18. Stupid Alternator Regulators Get Smarter…Finally
  19. WakeSpeed WS500—Best Alternator Regulator for Lead Acid¹ and Lithium Batteries
  20. Smart Chargers Are Not That Smart
  21. Replacing Diesel-Generated Electricity With Renewables, Part 1—Loads and Options
  22. Replacing Diesel-Generated Electricity With Renewables, Part 2—Case Studies
  23. Efficient Generator-Based Electrical Systems For Yachts
  24. Battery Bank Size and Generator Run Time, A Case Study
  25. A Simple Way to Decide Between Lithium or Lead-Acid Batteries for a Cruising Boat
  26. Eight Steps to Get Ready For Lithium Batteries
  27. Why Lithium Battery Load Dumps Matter
  28. 8 Tips To Prevent Lithium Battery Black Outs
  29. Building a Seamanlike Lithium Battery System
  30. Lithium Batteries Buyer’s Guide—Part 1, BMS Requirements
  31. Lithium Batteries Buyer’s Guide—Part 2, Balancing and Monitoring
  32. Lithium Batteries Buyer’s Guide—Part 3, Current (Amps) Requirements and Optimal Voltage
  33. 11 Steps To Better Lead Acid Battery Life
  34. How Hard Can We Charge Our Lead-Acid Batteries?
  35. How Lead Acid Batteries Get Wrecked and What To Do About It
  36. Equalizing Batteries, The Reality
  37. Renewable Power
  38. Wind Generators
  39. Solar Power
  40. Watt & Sea Hydrogenerator Buyer’s Guide—Cost Performance
  41. Battery Monitors, Part 1—Which Type Is Right For You?
  42. Battery Monitors, Part 2—Recommended Unit
  43. Battery Monitors, Part 3—Calibration and Use
  44. Battery Containment—Part 1
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Nick Kats

John

I’m truly dumb when it comes to electricity, but I’m going to ask this – What about solar panels & windvanes? Won’t these top up the batteries? Solar panels & windvanes can be used at a marina – no need for shore power. My windvane is connected to a regulator to prevent overcharging of the batteries. My hard solar panel is small & is put out on deck when I’m away.

What am I missing here ? (!!!)

Thanks,

Nick

PS – The solar panel & the windvane terminate in clips (as in alligator clips, or jumper cables) which I can move from one bank of batteries to the other as needed. A brilliant idea suggested by an electrician friend.

Jay

Isn’t equalizing the batteries a completely separate issue from the regular charge/discharge cycle that we all put the batteries through regardless of the number and kinds of charging capabilities we may have?

Now I feel like I’m missing something in this ‘conversation’.

On the topic of equalization; what happens when the batteries have to be left aboard for the winter while the boat is laid up? We have a couple of solar panels that will keep them topped up but there is no way to equalize them every month. Will we just suffer the loss of life at some point?

Chris Witzgall

Hi;

I have built one 24v 40ah LIFEpo4 lithium battery, and just bought a pre-made (DIY CLASS) 200ah 12v battery, which arrived today. I think these will be the standard batteries for many cruisers not too many years from now. Some highlights:

-little to no Pekert effect. 1c+ charging and 3c discharging allowed.
-1/2 of the weight
-5x the cycling ability
-no gassing, and no equalization
-works with most charging sources. Since they are designed to be charged up higher than most marine charging sources, current stops flowing before they reach full charge, but the % lost not charging fully is minuscule.
-Bulk charging extends up to 90%, and you can safely discharge 80% without grossly effecting the # of cycles. The cells I have in the Torqueedo pack are rated to 2000 cycles at 80% discharge, the Hipower brand cells in the 200ah 12v pack are rated to 1000 cycles at 100% discharge, I have not found their rating at 80% online yet. Thundersky brand cells are rated even higher.

Cost? You can put together what I bought, a 200ah 12v pack with a Battery management system to protect both the cells and your alternator, for about $1200 cell cost and $450 BMS cost. This one weighs about 80lbs in a 4d battery box, and is set to replace 4, t-105 wet cells at 445ah capacity.

Chris

Matt Marsh

Re. equalizing on solar/wind: With typical setups, I’d agree that equalizing from solar or wind power wouldn’t work. But I can’t think of any reason why a good buck/boost MPPT controller couldn’t be programmed to provide an equalization voltage from a solar or wind source. It should be just a matter of programming the unit’s microcontroller to allow a few different operating modes.

Re. LiFePO4: It’s interesting to see those costs, Chris- they seem to be coming down dramatically. The current interest in electric cars is causing a lot of money to be poured into battery development, and I would consider it quite reasonable to expect the option of choosing between a wide range of traction batteries using half a dozen different chemistries within six or eight years’ time.

Justin Godber

Justin again from Lifeline Batteries. Interesting posts. John, your article is right on about equalizing.
Re: Equalizing using solar and Wind. This can be done but it just needs to remain constant for the full 6-8 hours. This is usually the down fall to equalizing this way. If you can find a way to have it remain constant and still push good amperage then by all means use that source.

Re: LIFEpo4 or and Lithium Batteries for that matter. We have built and have been testing Lithium batteries for quite some time. You can see this link here where we have built one for the US Navy and got the contract for it:
http://www.concordebattery.com/lion2.php
You can also find a full sheet of the advantages and disadvantages here:
http://www.concordebattery.com/lion.php
In summary here is the limitations to the technology that we have found.
•Requires protection circuit to maintain voltage and current within safe limits. Protection circuitry involves both additional hardware and software.
•On aircraft battery monitoring and alarms will be required for safe operation.
•Subject to aging, even if not in use – storage in a cool place at 40% charge reduces the aging effect.
•Transportation restrictions – shipment of larger batteries may be subject to regulatory control.
•Expensive to manufacture – about 40 percent higher in cost than nickel-cadmium.
•Not a fully mature chemistry – metals and chemicals are changing on a continuing basis.
•Extremely flammable electrolyte.

Although we are working very hard to provide top quality products we are also very concerned about safety. Right now the lithium cells are very dangerous and very volitale. If they get the wrong scenario you don’t want to be anywhere around that battery. Lithium Ion cells if ignited can and will burn at 1,100 degrees F. Not only do they burn at that temperature they also create their own oxygen at the battery plates, which means you cannot put out the fire. The cargo plane that just crashed in Dubai caught on fire because of the Lithium batteries aboard. Lithium batteries can spontaneously ignite if the air gets hot enough. That’s what they think happened. They think when it was sitting on the runway the cargo hold got up to 135 – 140 degrees and they self ignited.
We have come up with a non oxygen producing Lithium Ion but the electrolyte is still very, very flammable.
There are new shipping regulations going into effect January 2011 for Lithium Batteries and they are expected to cost the Lithium industry 1 billion dollars more annually. This means the price of Lithium is going up next year, not down. Not to mention they are now considered Hazardous Cargo even when shipping ground.
That still gives AGM batteries the best advantage.

David

Justin,
The info on the current issues around Lithium batteries is very helpful. I wonder if you have also been testing the new TPPL (Thin Plate Pure Lead) chemistry/constructions, like the Odyssey batteries. In their own product literature they are described as AGMs, but they are actually quite different. TPPL batteries are said to have very high charge acceptance rates and handle very deep discharges. The chemistry is still lead acid, so it would seem like equalization would still be required, but maybe less frequently? Please comment if you’ve been exposed to those.

John,
Were TPPL batteries an option you considered, and if so what put you off of them?

Thanks for this very helpful series of posts.