Forum Discussion

sjturbo's avatar
sjturbo
Explorer
Nov 10, 2014

First Top Charge

I finally got my volt/amp meter wired in to my Mega Watt and started my first Top Charge. Initial battery voltage was 13.2v. Mega Watt was set to 15v. Turn-on voltage was 14.8v @ 33a. It quickly went to 15v @ 4.8a. Within 15 minutes it had dropped to 3.5a. I thought I would check readings in about an hour? I will also check for modest bubbling. Can I shut off the MW at that time to measure the battery voltage?

75 Replies

  • sjturbo wrote:
    Ok Did not see posts til one hour. Am I shutting down every 15min to check voltage and restarting until I reach 15v on the battery? And when I shut down, how long do I need wait to measure the battery?


    Keep the Mega Watt on until you see 15.0V. After the V goes to 15.0V, set a timer and run the MegaWatt for 15 more minutes at 15.0V... that last 15 minutes is the top charging portion that does the dirty work cleaning up most of the sulfation on the plates, if there is some there.

    Note I said "most of the sulfation"... not all. To get it really, all clean, requires an equalization charge. You disconnect the batteries from your rig to do an equalization charge, because it's done with 15.7 to 16.0V , requires you to baby sit the first few times you do it to see what is normal, time wise, and is done much less frequently, and you really should check the SG when you are done with doing an equalization, to see if your cells specific gravity truly are closely equalized.


    As for your situation, I would top charge your batteries daily, if you can, Monday thru Friday, with this 15V then 15 minute timing routine, and then lets see what the SG is on your batteries, per cell, on Saturday Morning, after it's 6th daily top charge. Ask Mex to suggest what your SG readings should be. You do have or own a good hydrometer, don't you?

    Also, maybe post up some pics of your Mega Watt rig in action, or maybe a short video.
  • Tell us more about your batteries, model, and amp hours. If that is your pair of GC-2's, take a specific gravity reading per cell on each cell on each battery.

    Write down the date and each cell reading and post them up here.
    Also describe the size, in mm, of the bubbles coming to the surface of the batteries. They should be 1mm in diameter, not roily boiling hot water action type bubbles, but little tiny bubbles coming up. Size of bubbles should increase slightly the higher you are charged, and or the higher or more topped out your specific gravity is. Tiny bubbles are good, they are stirring the electrolyte up, and making it homogenized for proper measuring with a hydrometer.
  • Ok Did not see posts til one hour. Am I shutting down every 15min to check voltage and restarting until I reach 15v on the battery? And when I shut down, how long do I need wait to measure the battery?
  • You are seeking a formula. Keep the battery at 15.0 volts for 15 minutes then shut down the converter 15+15 should be easy enough to remember. My original formula calls for the power to be shut down when voltage reaches 15. But my original formula also calls for 5 ampere charge rate to be used. Bubbling is an excellent way to tell that the electrolyte is being stirred.
  • No point in checking voltage then. Still be lots of surface charge.

About Technical Issues

Having RV issues? Connect with others who have been in your shoes.24,288 PostsLatest Activity: Jan 09, 2022