Amps and charging with a generator

In this linked test, a 20A car charger was faster than a 35A converter charger since the smart charger charges at 14+v. I believe the math is the 20A charger returned 30 ah in 2.5hrs while the 35A converter charger did 20 ah. I'm guessing a 10A smart charger would of done ~25 ah in 2.5 hrs.
http://forums.woodalls.com/Index.cfm/fuseaction/thread/tid/22696014/print/true.cfm

I hope not that is too fast for charging a single 80 amp battery.

3 State chargingk, no matter if using generator or shore power starts with BULK mode.

Very few 3-stage converters maintain peak output during the entire bulk (they taper off) so if you have an 80 amp hour G-27 (Should be 90-95) Bat half full it should bulk in about 1 hour. perhaps a bit more depending on the taper


Stage 2 is absorption, this is the last,, about,,10% of the charge.. Takes at least 2 hours.


Stage 3 is float.. All done charging at this point.

It might depend also on if you have an AGM Deep Cycle battery, vs a flooded lead acid battery. Certain brands of high end AGM batteries would have no problem taking 55 Amps, their design makes the internal resistance on the battery very, very low.

So the answer is, it depends.

Ductape wrote:
Look at the chart at the bottom of this page: http://www.progressivedyn.com/charge_wizard.html

Bottom line no, to answer your question. It takes much longer because:
1. The battery is limited in how much current it can accept.
2. The current acceptance tapers off as the battery approaches full. So the first 20% you charge back in will go a lot faster than the last 20%.

Correct.

Look at the chart at the bottom of this page: http://www.progressivedyn.com/charge_wizard.html

Bottom line no, to answer your question. It takes much longer because:
1. The battery is limited in how much current it can accept.
2. The current acceptance tapers off as the battery approaches full. So the first 20% you charge back in will go a lot faster than the last 20%.

aruba wrote:
If my 3 stage converter is rated at 55 amps, does this mean when it is hooked up to shore power, it can replenish an 80 amp hour (group 27 battery) in about 1.5 hours? ie. 80 / 55 = 1.45.

Does 55 amps imply 55 amp per hour?


Thanks.

Simple answer: No

Longer answer: The 55 amp rating is how big of a load the converter can carry without burning out. You can run 660 watts of DC load assuming 12v nominal voltage. Some of that will go to charging your battery, some will go to your lights, fridge, vampires, most will likely sit unused.

The state of the battery determines how much amps it's willing to accept regardless of the capabilities of the charger involved. The wiring to battery must be sufficient enough to deliver rated amperage of converter which is not always the case from the factory.

Secondly, most multi-stage converter chargers start out in bulk mode to quickly replenish your battery. Depending on the charging characteristics of your converter, this mode drops out before battery is fully charged, somewhere in the 80% to 90% range.

Absorption mode kicks in and finishes the process for the most part. Once converter shifts to float mode battery should be at or very near fully charged. Monitoring DC voltages on your rig can help determine which charging phase you converter is currently utilizing.

Along with solar, we use our generator to charge our pair of 6 volt GC2 batteries via our Iota IQ4 converter. Depending on battery SOC, we can get batteries up to the 85% to 90% range within a couple of hours of runtime. With good sun solar can do the job on it's own.

Yes and no. Yes the converter is capable of 55 amps. No a group 24 battery is not capable of accepting 55 amps for a full hour. Especially not at the top 20% of charge.

Any chance this is a WFCO converter? Measure the voltage to verify if you are getting boost mode 14.4 volts. If you only get 13.6 volts then amps will taper quickly and charging from low to 100% will take 12 to 24+ hours.

I know it seems like picking nits, but amps is amps, not amps/minute or amps/hour or any other 'per' designation. The correct term is ah, or amp-hours. 55 amps running for one hour is 55ah. Your battery is rated in ah.

Your calcs are close -if that 80ah battery is fully discharged, which is highly unlikely. In reality, the Bulk charge would be followed by Absorb and Float, which will normally take a few more hours.

There are other factors like, will that battery actually accept 55amps? I really don't know, it seems like a very high charge rate. Someone else knows more about this. And using a generator of at least 1000w would be good.