Charging a Battery Bank

BFL13 - Thanks for the info... I tried to PM you earlier but that wasn't allowed on your end...

I guess the word demanding is the issue. I do know on my 12V batteries if I am using 14.4VDC as charge voltage it will show 53AMPS DC current being drawn from my 60A source of power... If I had 200AMPS capacity in my battery charger it will still only show around 53AMPs which is determined by the batteries internal resistance I suspect. The only way for me to show more DC Current would be to raise the DC charge voltage... This is where I was coming from on using the word 'demanding'...

I will only have 14.4-13.6-13.2 DC voltages available using my 60AMPS PD9260C charger unit...

My fear was it would want to draw more than 60AMPS when I was using the 14.4VDC mode for the two groups of 6VDC GC2 batteries connected in series. I don't really want to purchase a larger current capacity Battery charger at this time. Stretching funds now living off retirement checks hehe...

The 4.6 hours will fit into my daily routine of charging the batteries when camping off grid at my normal camping spots. We have generator run time restriction big time around where I live here in Virginia. As soon as the batteries taper back to around 6-8AMPS for each battery then I will be able to switch to solar panels once I get those installed if I have good sun for the rest of the day. Hoping this will cut back on my generator use to just over an hour a day required.

The solar panel DC Current output looks like is going to be around 20AMPS total DC current for the three panels in high sun I will be installing on my POPUP roof...

Think I will be in good shape here doing this method of charging my batteries each day when camping off-grid...

Hopefully in a couple of months I can purchase the four T-105 batteries and will be able to see for myself what the DC Current status is going to be for my setup...

Thanks again for the rerun of answering my earlier question about this.

Roy Ken
King George, VA

Leave the batteries hooked together in their 12V series-parallel connection for charging.

For winter storage, there's generally little need to remove the batteries to your basement. The cold will not hurt the batteries in the least so long as they aren't discharged. If you charge them fully and disconnect them (so there are no parasitic loads), they will not self-discharge too much over a New York winter as self-dischrage rates are quite temperature dependent and much lower at cold temperatures. If you have solar or power available, so much the better to keep them charged up in the RV.

What charger or converter to use depends somewhat on how big a generator you have. For boondocking, the general goal would be to get as much charge into the batteries as quickly as possible, which boils down to having a charger or converter with a sufficiently high voltage output that maximizes the (apparent) power the generator can produce. Many converters have rather poor power factors, so the apparent power is somewhat higher than the actual power consumption.

(If you aren't familiar with apparent power vs. real power, here's a quick rundown. "Apparent power" is the product of the RMS current and RMS voltage of an AC load, the two measured independently. "Real power" is the actual rate of energy consumption, computed by integrating the instantaneous power over time. Apparent power will be higher than real power if the current waveform is not a sine wave in phase with the voltage waveform. The ratio of real power to apparent power is the power factor, which is always less than 1 and often expressed as a percentage.)

Leave them all wired up and just charge them with the rig's converter, using either shore power or generator power. No need to take them inside for the winter unless you have no shore power over the winter. the converter will look after them.

How many watts is the inverter-generator you bought after the previous thread of yours on that? That will be your limiter on how big in amps of a charger/converter you can run with it.

If you do take the batts inside for the winter, you will need a "maintenance charger"--usually about 2 amps that holds a steady voltage like 13.4v the whole time it is plugged in. (DO NOT get a "manual" "trickle charger" for that job! It will let the voltage climb way high, and overcharge the batteries.)

EDIT--Roy, to repeat myself here on your question, a 50-90 on 440AH with a 55 amp charger will take about 106 minutes for the bulk stage. At about 72% SOC, amps will taper for the absorption stage, that will take about 172 minutes. So total time will be about 4.6 hours.

If you want to do it in 3 hours you will need to do just 50-80s instead of 50-90s, or try 40-80s if you need the AHs. If you had more generator, you could go to higher amps charging to get a faster recharge.

The four batts will not "demand" a limited amount of amps in bulk. Forget that notion, please :( The 440AH bank will "accept" at least 160 amps at 50% no sweat, so don't worry about that.

1 battery or 10 is not that different. I recommend you verify that you have a good three stage converter and just leave the RV plugged in. Charge 48 hours and use a disconnect switch if you cannot stay plugged in. No need to remove any parallel connections.

I am currently working on the same battery bank layout with two groups of two 6VDC GC2 batteries wired in series.

It will look something similar to this layout...


Roy's image

I will be using the PD9260C Converter/charger unit to charge the whole battery bank using 12VDC with the capacity of around 60AMPS DC current.

I have never played with the 6VDC GC2 batteries in series before so I do not know how many AMPs DC current each of the two groups of two 6VDC batteries will be demanding when first hit with 14.4VDC Boost charge voltage.

I suspect they will demand around 20AMPS per group of the two 6VDC Batteries in series.

This will relate to around 40AMPS Total DC Current demand for the two groups of 6VDC batteries in series the first 15 minutes or so before they start tapering back.

I am looking to be able to return my 50% depleted battery bank from its 50% charge state up to its 90% charge in around three hours time using the PD9260C Converter/charger unit. I will be using my 2KW Generator to power up the PD9260C converter/charger unit during this time period.

My planned Trojan T-105 Batteries really want to see around 14.8VDC for the initial charge sequence but I will only be using 14.4VDC... I am hoping this will work just fine but perhaps taking alittle longer than the three hour charge routine...

I have been asking the battery bunch here for a month or so now how many DC Amps demand two groups of two 6VDC GC2 batteries will want to see when first hit with 14.4VDC charging voltage.. Not getting a good answer I am planning now to just measure this for myself when I finally get to purchase the 4EA 6VDC GC2 T-105 batteries... Hoping I won't have to purchase a 80A DC current PD9280 converter/charger unit...

My current three 12VDC batteries in parallel want to demand around 17AMPS for each of the three 12V batteries wired up in parallel for a total of around 53AMPS when first hit with 14.4VDC.

My game plan at any rate haha...

Roy Ken