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

NinerBikes
Explorer
Nov 16, 2014
OK, some observations by me.

I will pretty much see champagne sized bubbles, albeit, very very small volume of them, coming to the surface on my T-1275 by the time it will only a 7 or 8 amp charge rate from the Mega Watt S35-12, when set at 15.0v. I have never seen the T-1275 have much of anything resembling a roily boil.

I have seen a much higher volume of champagne bubbles on my old manual Sear 12V 6 amp charger when doing an equalization charge, mainly because it will put out 16.0V, and the battery will take it, but only for a short while before the voltage starts dropping off back to 15.7 or 15.6V.

Someone should do a video of batteries, and bubbling observations based on state of charge. A picture or a video from an expert is worth a thousand words.

I know Mex Wanderer now has a video camera feature on his smart phone. All he'd need to do is host it somewhere like YouTube after setting up a free account, or on PhotoBucket.
MEXICOWANDERER
Explorer
Nov 15, 2014
Then Again...

Ho Ho Ho
mena661
Explorer
Nov 15, 2014
BFL13 wrote:
I get to use this again! :)

https://www.youtube.com/watch?v=mlCiDEXuxxA
Oh God! LOL!
sjturbo
Explorer
Nov 15, 2014
Hola MW, rolling boil no bueno! Pero dos bubbles per/sec si bueno? What size? I do remember you talking about it but the size escapes me. I have a Victron meter but not real familiar with it yet. Grasias!
MEXICOWANDERER
Explorer
Nov 15, 2014
No roiling boil por favor. Two bubbles per second is fine. I thought I had covered this a few times ???

A positive reading on an amp hour or kWh meter would really ease the job. Example: +34 amp hours the cells should be bubbling at 15.0 volts. Amperage, time, voltage, hydrometer, they all fit and make things predictable and precise. Then you get to summarize, walk by the amp hour meter, note it, then twist the dial on the Intermatic timer then go pop a brewskie.
sjturbo
Explorer
Nov 15, 2014
Sorry jrnymn7 I do not recall the voltage. Great video BFL13, was he in float or top charge:)?
Salvo
Explorer
Nov 15, 2014
That brings back memories from the 60's when living in Hawaii. That's what the tourists came to see.
BFL13
Explorer II
Nov 15, 2014
I get to use this again! :)

https://www.youtube.com/watch?v=mlCiDEXuxxA
jrnymn7
Explorer
Nov 14, 2014
sjturbo,

Do you recall what the battery voltage was at before putting them on the 13.2v float for 24 hrs ? I'm wondering whether or not the batts were very near full before you started the top charge?
sjturbo
Explorer
Nov 14, 2014
MEXICOWANDERER wrote:
The Mega is plenty big enough. I mused this for a bit and came up with an idea. Apply the Mega. 15.0 volts. This time disregard the amperage. Instead monitor the acid in all cells. When all cells are bubbling slightly note the time elapsed between start to finish. This can easily eat a couple of hours, so don't worry. Just ensure you are starting from a level of battery charge that is easily repeatable. That way you can top charge with a timer. I'm soooooo lazy I use an interval timer, but one with a battery backup (I further cheat and use a cheap 12 volt voltage regulator and timer and suck power off the 24 volt bank - not likely to run out of memory). A weatherproof timer is inexpensive and you will look for a lawn sprinkler TYPE timer, which is called an INTERVAL TIMER. While I'm doing important things like reading, snoring, or staring out across the sea the timer and charger is doing it's thing. Not important whether your timer is AC or DC, but it is important that it not lose it's mind (timing cycle) because of a power outage.

Let those batteries bubble a little. If one cell is reluctant, find out why. Usually it is a sign of sulfation. Do an equalization. Then try it again down the road. Bubbling the start of which is an incredibly underused tool in battery management. Use it to VERIFY your perception of state of charge.

APART: I would love to see - it would be my reward to see declarations here "Gee I followed this stuff, it was simple, and it apparently doubled the lifespan of my batteries". Then I will have accomplished my goal. Vamos A Ver.

The increase of sophistication of these threads puts a smile on my face - thanks guys, for the time being, that is reward enough :)

Ok Let's talk bubbles! Are we talking champagne, (tiny bubbles) or Lawrence Welk (maybe not quite that big, bubbles). When I was top charging I was getting a good flow of tiny bubbles mixed with occasional larger bubbles. Never got to a rolling boil but the tiny bubbles were significant in number. So, once I get to this bubbling on all cells should I continue to charge until? Remember my TC took ~11hrs to reach 14.7V.