Charging rate

[malk415]

Gents.

I have a 05 Journey 36G, when charging the batteries on shore or generator you can set the amp draw on the charger from 0-25 which effects the amps the batteries are being charged at.

Currently we are dry camping charging with the generator and have the amps set at 10 which charges the batteries on bulk mode at 35 amps.

What is a safe amperage to have the batteries charging without "cooking" them because you are charging them at too high of rate?

Mark

[krivanj]

How many batteries do you have?
I have six batteries. My charger starts in bulk mode at up to 90 amps, but if you divide that by 6 you only get 15 amps per battery. Not too much as long as the wires support the current.

[NeilV]

It is nice that Winnebago now has the owners manual for your coach online however it dosn't cover the amperage setting on the charger:

http://www.winnebagoind.com/resource.../05Journey.pdf

What make and model converter/charger is it?

[jerichorick]

When you set the amps for the inverter you are setting the AC input limit only because you are sharing the shore power available. The inverter determines the amount of current the batteries will get per the manufacturer's parameters. Don't fret about putting too much current through your batteries. Only when you run the equalize setting on the inverter do you chance damage. You really need to know the condition of your battery bank before implementing this program.

[dengraham]

Hmmm, help me understand this a little better. If you are charging your batteries with the generator, why wouldn't you want the maximum amount of charge going to the batteries?? Why not set it at the maximum of 25? to get the batteries topped off as quickly as possible? Am I missing something here?

[camaraderie]

dengraham...if you have 30amps AC 120V coming into the coach from the generator...you may have other things you want to run BESIDES the battery charger with the total of 3600 watts. Your battery will charge at DC 14.5 volts and about 20% of your batteries capacity in amps.

Like an air conditioner or a TV etc. ... and to the extent that you max our your charging system...you may not have enough left to run the other stuff you want to.
In general...you don't want to charge wet cell batteries at more than about 20% of their rated amp hours...i.e. 100 amp hour battery should charge at 20amps in bulk mode. If you have AGM's you can charge at at least double that rate and sometimes much more...cutting down charging time and expense.

[malk415]

camaraderie.....My explanation was lacking a bit but your info is exactly what I was looking for and can understand...20% or rated capacity.

thanks for the info.

Mark

[dengraham]

Thanks Cam. Got it.

[camaraderie]

You're welcome guys...just to be sure...it is 20% of your Total amp hours Five 100 amp hour batteries would be 500 amp hours and could take up to about 100 amps in charging. As a lower limit...you should shoot for not less than 10% capacity.

[Stan.Birch]

Originally Posted by camaraderie

dengraham...if you have 30amps AC 120V coming into the coach from the generator...you may have other things you want to run BESIDES the battery charger with the total of 3600 watts. Your battery will charge at DC 14.5 volts and about 20% of your batteries capacity in amps.

Like an air conditioner or a TV etc. ... and to the extent that you max our your charging system...you may not have enough left to run the other stuff you want to.

I fail to understand the dilemna. If you are connected to a 30 amp 3600 watt power source, and your battery charger requires 20 amps @ 12 VDC, 3 amps at 120VAC, that's only a mere 250 watts, leaving over 3000 watts left for running everything else in the rig.

Originally Posted by camaraderie

In general...you don't want to charge wet cell batteries at more than about 20% of their rated amp hours...i.e. 100 amp hour battery should charge at 20amps in bulk mode. If you have AGM's you can charge at at least double that rate and sometimes much more...cutting down charging time and expense.

Wet cells do just fine with a 40% charge rate in the bulk phase. Offering 13.8 volts for the 25% resolution phase, or even forever, will leave your batteries serving you for many years (10) to come.

If you have AGM batteries, don't ever attempt to administer the kind of charge rates a well cell can handle with ease. If you overcharge a wet cell, it will cost you a glass of water. Overcharge an AGM battery, it will cost you $200 per battery.

During the initial charge phase of a wet cell battery, the battery can easily handle a 14.5 volt potential; and in the resolution phase 13.8 volts forever; and for those further south in more torid climes, 13.5 volts forever.

[jerichorick]

Good morning Mark. I hope you understand what Stan is saying. He has hit the nail on the head. Bottom line? Your 0-25A setting is so that you can be certain you don't draw too much current from your shore or genset when trying to make coffee. But what I have see is that most of the better designed inverters ramp down if the input current rises outside of what the inverter is drawing. It will not draw any MORE than 25A, 20A, 10A... You are in control of the MAXIMUM input current sharing.

If you are on a 20A shore power this becomes critical. 16A is the safe sustained draw for this size 120V circuit. You must set the charger input current rate to no more than 15A in this case. Again, the inverter will provide the correct charging current to the battery bank because it is programed to know this information by the installer or you if you switch out the batteries to a different size or type.

I love questions like this. Gets the old gray matter revved up.

Happy trails,
Rick

[wa8yxm]

This varies a bit with type and brand of battery but....
Xantrex, in the manual for the prosine 2.0 inverter/converter, suggests a maximum charge rate equal in amps to 30% of the 20 hour amp-hour rate of the batteries being charged (this is for flooded wet cells, Maintenance free and AGM)

So a Group 29 battery (roughly 105 amp hours) 31.5 amps (round to 30).

A pair of GC2 golf car batteries in series, 230 amp hours. 69 amps (round to 70)

LIFELINE, last time I checked recommended 30 percent as the MINIMUM initial charge (up to 300 percent) but that was ONLY lifeline, not other AGM brands.

GEL CELLS (not easy to find in the sizes we use, and for good reaons, AGM's are way better) charge slower. (20 or 25 percent forget which) .

So, take a look at what you have and add per the following chart.

GC2 (Six volt) pairs 220 (use 220 to be safe)
Group 24, 75
Group 27, 95
Group 29 105
Group 31 130

Add up your capacities, multiply by 30% (0.30) and that's your answer.

[camaraderie]

Originally Posted by Stan.Birch

I fail to understand the dilemna. If you are connected to a 30 amp 3600 watt power source, and your battery charger requires 20 amps @ 12 VDC, 3 amps at 120VAC, that's only a mere 250 watts, leaving over 3000 watts left for running everything else in the rig.

Agree if all you have is a 100amp battery. My 1200amp bank took a "bit" more but your general point is valid..



Wet cells do just fine with a 40% charge rate in the bulk phase. Offering 13.8 volts for the 25% resolution phase, or even forever, will leave your batteries serving you for many years (10) to come.

Disagree. I think it depends on brand...and temp...batteryfaq.org says:
"9.1.1. The BULK stage is where the charger current is constant and the battery voltage increases, which is normally during the first 80% of the recharge. Give the battery whatever current it will accept as long as it does not exceed 25% of the 20 hour (expressed "C/20") ampere hour (AH) capacity rating, 10% of the Reserve Capacity (RC) rating, wet batteries do not exceed 125° F (51.5° C), and VRLA batteries do not exceed 100° F (37.8° C). " Maybe we cab agree on 30%.
I do agree that float voltage of MAX 13.8 can be kept forever provided the amps are less than 1% of C.

If you have AGM batteries, don't ever attempt to administer the kind of charge rates a well cell can handle with ease. If you overcharge a wet cell, it will cost you a glass of water. Overcharge an AGM battery, it will cost you $200 per battery.

Dead wrong. Most AGM's can handle vastly more currrent charging than wet cells.
"Linden also discusses quick-charging in which he sets a constant voltage and lets the battery accept what charge it will. His conclusion is "These data show that the thin-plate VRLA battery can be fast-charged to 100% of the rated capacity in less than 1 hour."

So the bottom line is that it is OK to charge a sealed lead acid battery fast as long as you don't overcharge it. Modern CC-CV (constant current-constant-voltage) and multi-stage chargers can perform this function very well. They ensure that when the battery is full the applied voltage is less than the gassing voltage, and no damage can occur. Fast charging is important to the electric vehicle industry, and long battery life is essential, so a lot of the quick-charging research has been done for this application. Here is a link to a fast-charge algorithm that achieves both http://www.sciencedirect.com . Using this algorithm for sealed lead acid batteries they showed that they can safely restore 50% of the charge in 20 minutes, or an average rate at 1.5C, or at a 4.5x rate over the rate that the battery companies suggest.

In the book Electric Vehicle Battery Systems By Sandeep Dhameja he states that "Fast charging does not exhibit detrimental effects on battery cycle life." He is talking about a charge rate of 8C to 9C, though he does not charge at this rate beyond 80% state of charge.

In the book Valve-regulated Lead-acid Batteries by David Anthony James Rand, P. T. Moseley, J. Garche, C. D. Park it says:

" . . . it is now abundantly clear that thin-plate VRLA batteries can be fast charged with excellent results. Contrary to previous beliefs, for a given VRLA product, the imposition of aggressive charging algorithms that minimize the effects of the oxygen cycle and finish the charge relatively quickly can result in superior cycle lives.In other words, fast charging will give you more cycles than staying below C/3!"
Fast charging of sealed lead acid batteries.
*************
I note that Lifeline says their AGM's can be FULLY charged in 2 hours from zero if high inrush current is available. Odyssey specifies that up to 3.1xC may be used to fast charge their AGM's if Voltage is controlled at 14.7.(http://www.odysseybattery.com/docume...1_0411_000.pdf page 17 table.)

During the initial charge phase of a wet cell battery, the battery can easily handle a 14.5 volt potential; and in the resolution phase 13.8 volts forever; and for those further south in more torid climes, 13.5 volts forever.

Agree with the last paragraph. See comments on others above in color.

[Duner]

Originally Posted by malk415

Gents.

I have a 05 Journey 36G, when charging the batteries on shore or generator you can set the amp draw on the charger from 0-25 which effects the amps the batteries are being charged at.

Currently we are dry camping charging with the generator and have the amps set at 10 which charges the batteries on bulk mode at 35 amps.

What is a safe amperage to have the batteries charging without "cooking" them because you are charging them at too high of rate?

Mark

Mark,

To give you specific recommendations, we need these questions answered:

How many and what type of batteries do you have?
What inverter/charger do you have?
What size is your generator?

Your '05 Journey and my '04 Chieftain were shipped with a Dimensions 2K inverter charger and I have a lot of experience dry camping with that unit. But we need to know if there have been battery and charger upgrades.

Bill

[Ray,IN]

As previously mentioned, batteries should be charged at 20% of AH rating for longevity. Very few batteries display the AH rating, usually RC(reserve capacity) is listed. Those terms are not the same thing! To quickly/roughly convert RC to AH (there is controversy on this) divide RC by 2 then add 16 = AH. Using the RC number will cause you to deplete your battery bank in half the time you think. This means, say your battery bank has a total of 300AH capacity, the maximum charge rate should be 60 amps for the bank, IF you desire maximum longevity from your batteries, and then only draw them down to 50% AH capacity. I have 440AH capacity, and have my charger set at 100 amps max.for bulk charge.

[malk415]

Duner..

I have the following:
Onan 6500 watt generator
Dimension 12x20B3RT 2.0KW inverter
4 Costco 6V golf cart batteries.. 220AH

Thanks,

Mark

[Duner]

Originally Posted by malk415

Duner..

I have the following:
Onan 6500 watt generator
Dimension 12x20B3RT 2.0KW inverter
4 Costco 6V golf cart batteries.. 220AH

Thanks,

Mark

Alright Mark, almost exactly the same as me.

When dry camping for a few days in a row, you don't want to get your bat's too far discharged; especially below 50% (bat volt <12v with some load) ..... that will take the life expectancy and capacity out of the bat's faster. So each day let the Onan and the Dimensions charge the bat's as fast as possible and that means leaving the Dimensions input amps at 25A (ac). It will put out 100 amp for a few mins and then start tapering down as the volts come up to 14.5 or so. i usually run the Onan for 1 hr or so in the morning and 2 hrs in the evening and that's enough for me. Your Onan has enough power to run essencially everything at once and no need to limit the charger. I have a dual dvr sat receiver that eats a lot of power so I shut it down when I go to bed and turn on in thye morning and leave on all day.

One other issue not related to dry camping.....
The early Dimensions 2K were designed to do an equalize charge every 5 times the unit is plugged into shore power to "condition" the batteries. On wet cells like ours, that means 15+ volts for 8 hrs. In my opinion this is way to often and 5 cycles may result in two equalizing in less than one month and I think all they need is twice per year. In later years Dimensions changed the design to 10 or 20 power cycles before equalizing again. I called them to see if I could get the more updated design, but no mod is available. So to minimize the stress on the batteries, I keep the Dimensions limited to 5 amps which limits the amps in equalize mode to around 15 amps. This will reduce the amount of water boiling out and acid seepage around the vents.

So when your dry camping, just set the Dimensions back to 25 amps.

Happy trails,
Bill

[malk415]

Duner..

Thank you for the info. It is a great helpl

Mark

[def]

Originally Posted by Duner

Mark,

To give you specific recommendations, we need these questions answered:

How many and what type of batteries do you have?
What inverter/charger do you have?
What size is your generator?

Your '05 Journey and my '04 Chieftain were shipped with a Dimensions 2K inverter charger and I have a lot of experience dry camping with that unit. But we need to know if there have been battery and charger upgrades.

Bill

Bill's is the best and only answer you should consider at this point.

The battery type and capacity will determine the correct charge profile. Your current charger may or may not satisfy the battery charging requirements. While the generator is a variable in your power system, it is not going to change and so is likely of little consequence.

I just installed a AIMS power inverter in my coach which has user selectable battery charging profiles allowing most any battery type to be charged without damage (LiFePo battery type is the exception).