How many amps do you recharge with?

[Devin & Amy]

I have an SW4024MC2 Xantrex.
I have never really adjusted much from where the default settings are.
What I am currently putting into the batteries is 15 amps, as available.
When I charge from the genset how many amps can I push , to speed things up a bit?
Batteries: 6@ 12v x 175Ahr Deka AGM wired 24v
Wrico 13.5kw  3-cyl turbo Kubota
Thanks,
Devin

[Frank @ TX]

Hi Devin,
I vary the amps to the power supply.
If I'm pluged into 15 amps , I set the max charge to about 8.
That saves a few amps to be used by other systems.
When plugged into 50 or the gen is running , let it fly , as much as the inverter can put in.
With mine not everything is run from the inverter.
Only one of the three AC's is run from the inverter.
There are other systems that operate too , strick a balance.
Hope this helps.
Frank

[Tony LEE]

You have a 24V 525Ah battery. Conventional wisdom says C/10 as a charging rate is OK for flooded cell batteries assuming you have a three-stage charger so 50 amps bulk charge would not be excessive.

The battery manufacturer may have different ideas though.

I have 265Ah AGMs and the manufacturer specifies a maximum of 55 amps so having a double string gives me 110 amps. When charging from the engine alternator - which I do occasionally when not likely to be on shore power and am moving between camps -- it puts in about 170 amps tapering fairly fast over the first hours driving. This takes place at well below the gassing voltage so there is little effect on the battery. After a couple of hours the alternator has maxed out and the current is around 50 amps so I switch it off and let the solar system finish off.

[gumpy]

Devin,

Check your Trace (Xantrex) manual. There's a section on Recommended Battery Charger Settings, which says basically, set a maximum charge amps that is less than 1/5 of the battery capacity.

In your case, you have 525 Ah @ 24V, so you would set your maxumum charge rate at 105 amps DC. Now, since the setting is actually in AC, you need to divide that by 5 to get the AC equivalent, or 21 amps. Actually, the manual says to divide by 4 for 24 volt systems to account for charger inefficiencies. So you can set it to 26 amps max AC charger setting. Anything in between 21 and 26 should suffice.  I recommend you buy the battery temp sensor and attach it to your batteries and inverter if you're going to use the max settings.

If you have a battery monitor, you should see no more than about 100 amps going into the batteries on bulk charging with these settings.

craig

[Sean]

Devin,

Go ahead and set your charger to the max.  That's 33 amps (@120vac) on newer SW4024's, 35 amps on older models.

That will kick the DC charge up to 150 amps max, which is fine with your 525 AH bank.  Most AGM batteries can absorb up to 100% rated capacity in an hour, and 150 amps will be only 28%.  In fact, even flooded cells can take up to 20-25%.

HTH,

-Sean
http://ourodyssey.blogspot.com

[Sean]

I vary the amps to the power supply.
If I'm pluged into 15 amps , I set the max charge to about 8.
That saves a few amps to be used by other systems.

Frank,

If you have an SW inverter, this is entirely unnecessary.  The inverter will automatically reduce the amount going to the charger when other loads need the current.  You should set your "max charge amps" (on menu 10) to the maximum your battery bank can safely accept, and leave it there.

The only amperage setting that you should need to change in normal usage is AC1 Max Amps or Shore Cord Amps, if your shore is connected to AC1.  On many RV installations, both shore and genny are connected to AC2 (via an external transfer switch), in which case you'd need to change AC2 max amps.  Found on menu 11.  In this type of configuration, you need to change the AC2 amps every time you unplug, too, unless your genny output and shore power happen to be the same rating.

-Sean
http://ourodyssey.blogspot.com

[Frank @ TX]

Hi Sean,
I'll tell you why I do the changing of the AMPS routine.
If pluged into 15 amps and let the inverter charge what it whats, I would pop the breaker of the campground.
Because the one input ( 15 AMPS ) is going to the inverter for powering some outlet and charging AND other 110 vac loads not thru the inverter.
We have some outlets not powered by the inverter ( 2-AC's , 110 heater in the Aquahot, various other outlets in the bus so marked).
So when we run the vacuum cleaner or other items and the inverter, we may pull more than 15 amps.
I watch the amp meters then shead loads as needed to not pop the breaker.
This helps with small campgroungs and visiting some folks with 15 amp plug.
Hope this helps
Frank

[Sean]

If pluged into 15 amps and let the inverter charge what it whats, I would pop the breaker of the campground.
Because the one input ( 15 AMPS ) is going to the inverter for powering some outlet and charging AND other 110 vac loads not thru the inverter.
We have some outlets not powered by the inverter ( 2-AC's , 110 heater in the Aquahot, various other outlets in the bus so marked).
So when we run the vacuum cleaner or other items and the inverter, we may pull more than 15 amps.

OK, I understand why you'd want, in this case, the entire inverter system (charger + loads) to draw less than the total, to leave room for stuff not going through the inverter (although, to me, it makes more sense to wire so that everything can be managed by the expensive and sophisticated inverter system, so you won't have to do this).

But, in that case, why change the charger setting, rather than simply dial down the total input amps setting?  That way, when there is less load on the inverter, it can make use of more current for charging.

Also, for everyone's benefit, you should be aware that typical circuit breakers will only carry their "handle rating" for short periods of time.  In continuous use, they are designed to trip thermally at about 80% of their handle ratings.  So when you plug in to a 30-amp campground circuit, you should set your Max Amps AC1 (or AC2, as appropriate) to 24 amps to avoid this type of tripping.  Likewise use 16 amps on a 20-amp circuit, and 12 amps on a 15-amp circuit.  Otherwise, during the bulk phase, the charger will ramp up all the way to the limit you've set and your pedestal breaker will pop after perhaps half an hour or 45 minutes.

-Sean
http://ourodyssey.blogspot.com

[H3Jim]

Frank,
I think you should still set the charge at max.  The inverter has a setting that you can specify the max amps the inverter will take from the source, just for that reason. Or  to limit current on a wimpy cable etc.  If you use this setting, you will be better protected, and your charger will charge faster - or as fast as you have current allowed to it.  It will then automatically reduce the charge amount based on other current draws.

[Devin & Amy]

Thanks guys!

We also use the AC2 input amps as a fine tune for our shore cord. The charger has been set at 15 amps. That is just a bit too slow when we're on genset.
I will now go and rectify my situation.
Devin

P.S.
Where in the heck did all this damn snow come from???(Bemidji, MN)

[H3Jim]

I could use a little snow, it was 100 degrees here today.