Steve

There is still one thing missing. What is the charge algorithm of your converter? Does it subscribe to the C/8 method of max current rate? If it does it is only going to put out that much current even if it has a no. 00 awg wire. Sunline set these things up with that 30 amp breaker in there a long time now. And my battery tray from Sunline will only accpet 2 grp 24's until I made it bigger. So there was fixed max ah capacity in the entire design. We are missing something. Sounds like some real good camp fire talk us “types” of curious minds.

Here is my latest typing to Mr. Battery. He is tied up and has not got back to me yet.

See if you can follow this thought process. I explain to him my quandary.

Dear Mr. Battery

Now to my battery charging. What I’m after is

What is the max allowed (recommended) charging rate in amps? I’m assuming the voltage is up at 14.4 in the high amp bulk mode. I have read about C/8 for lead acid wet cells as being the recommended limit. And if I under stand this right….please straighten me out if not, If I have a group 27, 115 AH battery rated on 20 hours, then this is 115/8 = 14.4 amps max current recommend. Did I get this right and is the C/8 right?

Here is a cut and paste. See mid page.

http://www.solarnavigator.net/battery_charging.htm
**Battery Charging Voltages and Currents:**

Most flooded batteries should be charged at no more than the "C/8" rate for any sustained period. "C/8" is the battery capacity at the 20-hour rate divided by 8. For a 220 AH battery, this would equal 26 Amps. Gelled cells should be charged at no more than the C/20 rate, or 5% of their amp-hour capacity. The Concorde AGM batteries are a special case - the can be charged at up the the Cx4 rate, or 400% of the capacity for the bulk charge cycle. However, since very few battery cables can take that much current, we don't recommend you try this at home. To avoid cable overheating, you should stick to C/4 or less.

Charging at 15.5 volts will give you a 100% charge on Lead-Acid batteries. Once the charging voltage reaches 2.583 volts per cell, charging should stop or be reduced to a trickle charge. Note that flooded batteries MUST bubble (gas) somewhat to insure a full charge, and to mix the electrolyte. Float voltage for Lead-Acid batteries should be about 2.15 to 2.23 volts per cell, or about 12.9-13.4 volts for a 12 volt battery. At higher temperatures (over 85 degrees F) this should be reduced to about 2.10 volts per cell.
I have found this in a few places. Is this correct? I’m assuming heat is the enemy here?

I’m trying to learn/understand what is going on in the battery to not want to go above that current as a constant practice.

And I’m trying to figure out if I discharge my batteries down to no less then 50% how long will it take running the genny to get then back to at least 90%? Then when it kicks down to 13.6volts how long until 95%? Can I just do something up to the 90 to 92% area?

Trying to find the math on how to recharge. If C/8 is the number the PD uses, then it is limiting the current, not the battery being able to take it? I guess that is the question. What is limiting the current, the battery being able to take it or the charger putting it out?

So let me see here…tell me where I go wrong. Charging at C/8, or 115ah/ 8 =14.375 amps into a 115 ah battery that is at 50% SoC to 90% (is 90% 103.5 ah?)

Does it go like this: 115*.50 = 57.5 ah at 50%. So 50 to 103.5% is 46 ah’s to charge back in. And if I’m putting in 14.375 amps/hour charge rate it this 46/14.375 = 3.2 hours? Is it this simple?

Now if I actually did that right, what I do not know is what the PD charging algorithm is. Does it detect my battery and only put out 14.375 amps or less or more? If so then up’ing the wire big time is not going to really help. But if I put 2 batteries on then that current would double would it not? Would try and pass 28.75 amps.

Which if I did that right then that 30 amp circuit breaker is getting real close.

See here for my original converter hook from American Enterprises and Sunline

This is the confusing part. Here at the power center, if nothing is running in the camper then the wire and the fuses here can pass 60amps. Yet the 30 amp breaker in the TT tongue will not let it.

Is the charger smart enough to sense the battery changing resistance and only put out 14.4amps to the bus if I was at 50% Soc?

And if I turn on 5 lights in the camper and some other things the draw say a full 30 amps, the converter boosts the current to 48.4 amps? 30 amps is being consumed in the TT, 14.4 going to the battery? And then If I shut down the 12 volt coffee pot say, ( I don’t have one but just talking) Then the converter regulates back the current automatically?

Tell me if I get this right:

Basically the converter is an amp regulator along with a volt regulator. It is smart enough to sense a battery resistance to DC common and regulate an amp and volt value to charge the battery. It sends that amps out into the DC buss and connects to the battery. On top of this it can sort out other loads on the DC buss and boost the current to compensate up and down. Some how it knows what a battery resistance is compared to a Maxx air fan or 12 volt light bulb. (how does it do that?)

And some how if a battery goes way down in Soc, it will not pass any more then C/8. It somehow knows the resistance of total ah capacity hooked to the buss? It can sort out 1 or 2 Grp 24 or 27’s on the line.

OK what did I say right or wrong?

See pics of charge setup on the PD tie in

More when I get a response. And we can point and talk on the weekend.

John

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