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?

No point in checking voltage then. Still be lots of surface charge.

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.

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?

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.

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.

First Top Charge | Good Sam Community

75 Replies

sjturbo
Explorer
Nov 13, 2014
Thanks for the Freas web site MW! I called them and I need to buy two kits and pay for shipping. The ABS is a great idea. I do that with my fishing poles. NinerBikes, I appreciate the link! I thought I would post a couple of photo's to help everyone who has helped me with this project see what they may have been trying to visualize. , ,
jrnymn7
Explorer
Nov 12, 2014
Mex said,

"Use a hydrometer correctly! It is a valuable instrument!. Keep a chart. Dip all twelve cells! Note the date. Do it again in a month. If all cells remain at 1.280 you needn't do a thing. If the battery is on float and specific gravity in all cells, falls from say 1.280 to 1.275 while being floated, the batteries are most probably slowly stratifying the acid. Do a top charge to mix the acid and freshen the plates. Again, this is with the batteries being floated."

Mex, would this be an indication to raise the float voltage a little?

Thanks.
NinerBikes
Explorer
Nov 12, 2014
jrnymn7 wrote:
Niner,

If the batt was only at 12.3v, how come the mega watt didn't remain in cc? Or did it hold at 26.2 amps for a while?

Held 26.2 amps for a while. When it got down to 12 amps, I shut the generator off, and put my 150w 8.8 amp solar panels on it at 15.0V for 2 hours to top things off.
jrnymn7
Explorer
Nov 12, 2014
Niner,

If the batt was only at 12.3v, how come the mega watt didn't remain in cc? Or did it hold at 26.2 amps for a while?
NinerBikes
Explorer
Nov 12, 2014
sjturbo wrote:
Ok thanks! How about this one, Hydrometer or please recommend one. OOPS, Don't think it is actually a Freas. I will look again!

Linky
MEXICOWANDERER
Explorer
Nov 12, 2014
Francis Freas Web Page

Choose the No. 1 hydrometer set
I telephone their main number and ask for sales
Place order for Bo 1 set
A week later it arrives
At Home Depot I made up a plastic ABS cylinder to hold the hydrometer
Use a blank cap on one end
Threaded bushing on the other
And a threaded cap that has a square wrench flat
I have accidentally dropped it ten feet onto concrete and prayed
Prayer works!
sjturbo
Explorer
Nov 12, 2014
Ok thanks! How about this one, Hydrometer or please recommend one. OOPS, Don't think it is actually a Freas. I will look again!
MEXICOWANDERER
Explorer
Nov 12, 2014
Lessee, Rolls Royce Phantom Extended Chassis
BMW V-12 engine and drive train
Recap tires

A Freas hydrometer is not that expensive. And it won't lie to you. On top of it they are easier to read than a play hydrometer.
NinerBikes
Explorer
Nov 12, 2014
This is what I see when the voltage is 12.3V on my Trojan T-1275 and I turn on the Mega Watt S35-12 to start charging.

Clicky for Youtube Video Link
sjturbo
Explorer
Nov 12, 2014
Thanks for the explanation and the help with the install NinerBikes! I always wondered what the MexicanWanderer looked like;). I looked at the Trimetric but went with the Victron based on features and smaller footprint, it has a 500amp shunt but is not in the charge circuit. The hydrometer is el cheapo (no name bulb type). I assume that is not the most accurate but I hoped it would do.

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First Top Charge

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