I am planning on upgrading my batteries to 4 6v batteries wired in series and parallel to have a 12v system with plenty of Amp Hours. There is a ton of information on how to wire things up but nothing on how to charge them both to top them off while boondocking and long term during the winter month's. Do I have to disconnect the parallel connection and charge them as 2 separate 12v banks (2 banks of 2 6v in series) or unhook everything and charge as 4 independent batteries or is there a charger that can charge all 4 batteries without disconnecting any of the battery connections? Also, what would be a good battery charger to get to accomplish the charging? I have an inverter generator and I'm looking at portable solar panels in the future to use while camping and will be storing the batteries in my basement during the winter month's. Thanks for your input.

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 imageI 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

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.

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.

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.)

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 KenKing George, VA

Charging a Battery Bank | Good Sam Community

275 Replies

full_mosey
Explorer
Jan 20, 2017
time2roll wrote:
There you go, I do forget about the ParaMode TempAssure.
This one seems it would meet the specs of that AGM even better.

Yes it would on paper. Plus the power factor corrected model 5465TC would be more efficient in the use of fuel when charging by genny.

What we don't have is any experience reported here. The documentation on the brand is lousy as well. Before I decided to switch from converter/charger to inverter/charger, I was looking very hard at the 5465TC.

IMHO, an inverter/charger is a step above the converter/charger. E.g, It is not unusual to find temperature compensation in an inverter/charger.

RobWNY;

I believe you will find the Deka/Duracell battery to be faithful and forgiving.

I used an 8A24 Deka for five+ years. It was my first AGM and it suffered badly due to my ignorance. I discharged it often at its C1 of 79AH, or around 79A and recharged it often between 25 and 50A. Only near the end did I learn about the 30% limit which is was 23.7A. The battery was exposed to parking lot temperatures as it was installed in my van in summer conditions of 130F ambient. Very few RVers have any clue about their battery's temperature. I do now.

My charging advice is to leave the WFCO connected. The WFCO can be relied on for only 13.6V which will be safe at least at any temperature. As a supplement, you need a, possibly portable, charger that defaults to 14.4V when initially powered up as would happen when starting a genny. In summer heat you can charge early in the day.

I rely on a solar system with temperature compensation to supply the 14.4V each day. Temperature compensation manages battery temperature by reducing Volts if needed.

Get the batteries. You will be fine.

HTH;
John
BFL13
Explorer II
Jan 20, 2017
What exactly is the problem with your WFCO? Does it do the 13.6 and 13.2, but not the 14.4 or is it something else?--to see if it can be your Float charger ok

How long do you want (or are allowed) to run the generator to do a 50-90?--Eg, my time target is two hours, but maybe you are good with three. Makes a big difference in what your recharging system has to be.

What is your estimated daily AH draw?

I think you should decide how to spend your money though. :)
RobWNY
Explorer
Jan 20, 2017
OK. SoundGuy and BFL13, you are both very knowledgeable with this stuff so before I get so confused that I end up buying 4 AA batteries and try to charge my camper using a cell phone charger, here's a challenge for you. Knowing that I currently have the WFCO 8955 with charging problems and that I want 2 6v batteries, tell me what you would do if in my situation. Pretty much your ideal setup without breaking the bank. Assume you have $1,000 give or take to work with. Give me which models of what equipment, which batteries etc. and then I will go shopping.
BFL13
Explorer II
Jan 20, 2017
RobWNY wrote:
So is everyone in agreement that I should consider Lifeline 6v AGM's as they are better batteries? I found a site that is selling them for $299 each with free ground shipping.

Heck no. :) You expect agreement here? Note there is no advantage 6s vs 12s with these AGMs like there is with Flooded.

I have this AGM (only rebranded) which works for me. Same price as those Sam's Dekas and have free shipping. You would need the 14.8 PD for recharging this one. Float voltage still an issue maybe.

https://www.amazon.com/100Ah-Replacement-Battery-Power-PS-121000/dp/B00S1RQX8C/ref=sr_1_3?ie=UTF8&qid=1484942659&sr=8-3&keywords=AGM-121000

Here are the specs--same as the UB121 above.

http://www.hespv.ca/hesproductspecs/HES/Stark_Battery_TD_ENG.pdf
SoundGuy
Explorer
Jan 20, 2017
RobWNY wrote:
So is everyone in agreement that I should consider Lifeline 6v AGM's as they are better batteries? I found a site that is selling them for $299 each with free ground shipping.

There's little doubt that the Lifeline 6 volt AGM battery is "better" but the larger question is whether you need "better" for your application and secondly, what charger are you going to use to care for these batteries? Recent posts seem to have solved that last issue nicely for you if you choose to go with those more cost effective 6 volt Duracells - a Parallax ParaMode that not only offers the correct charge voltage profiles but unlike most converters also offers temp compensation. Seems a pretty good match to me. :B
RobWNY
Explorer
Jan 20, 2017
So is everyone in agreement that I should consider Lifeline 6v AGM's as they are better batteries? I found a site that is selling them for $299 each with free ground shipping.
time2roll
Nomad
Jan 20, 2017
There you go, I do forget about the ParaMode TempAssure.
This one seems it would meet the specs of that AGM even better.
BFL13
Explorer II
Jan 20, 2017
time2roll wrote:
BFL13 wrote:
I pity the poor guy who wants AGMs with just a converter that does whatever it does, and he is stuck with that.
The right converter is available for any battery.
At 14.1 to 14.4 an IOTA or PD-14.4 would be fine.
Float on the PD is a bit below specs so my choice on this battery would be IOTA.

This one would fit. Also has temp comp. ISTR that Parallax has a newer line with similar specs.

http://www.bestconverter.com/4400-Series_c_101.html

My AGM wants 13.7ish Float so I just use the single voltage 13.8 converter for that like Phil does. That AGM wants 14.8ish for recharge, so I need another charger to do that part.

Really, since you usually have the converter first and then choose the battery, you should match the AGM specs to your charger's specs. There is a good range of specs among AGMs to choose from.
SoundGuy
Explorer
Jan 20, 2017
time2roll wrote:
Yea I would not press AGM too hard.

BFL13 wrote:
This AGM thing is difficult! We have Lifelines that want oodles of amps, but only 14.4v, while many others want 14.8v but only 30% amps.

Now we have this Sam's Deka that only wants 30% amps AND only 14.1-14.4 volts.

AND temperature compensation which the PD9260 the OP is considering doesn't offer. What to do? ... ignore this requirement? :h

In my own case I now use a small CTEK 7 amp charger instead of my WFCO 8955 and for maintaining my aging G27 flooded Interstate it does quite well as it does properly bulk charge at 14.4 volts which the WFCO has never done. However, if I do upgrade to a pair of AGMs, or even just one G31 AGM, I'd also seriously consider upgrading from the 7 amp CTEK which does not offer temp compensation to either a CTEK Multi US 25000 or NOCO G26000 - 25 / 26 amp chargers that do have temp compensation. Better choice than a PD9260 that doesn't? ... maybe. ;)
SoundGuy
Explorer
Jan 20, 2017
BFL13 wrote:
I pity the poor guy who wants AGMs with just a converter that does whatever it does, and he is stuck with that.

time2roll wrote:
The right converter is available for any battery.
At 14.1 to 14.4 an IOTA or PD-14.4 would be fine.
Float on the PD is a bit below specs so my choice on this battery would be IOTA.

This would describe the OP (and many of the rest of us) who own a trailer equipped by the manufacturer with the ubiquitous WFCO 8955 converter, often which is mounted miles away from the battery area and is wired with inadequate gauge cable. :( For those of us who only rely on battery reserve occasionally and have but one, maybe two garden variety flooded batteries, this may work "well enough". However, my entire point to the OP throughout this thread has been that if he's going to go beyond that (and he already has by investing in a 3000 watt genset) by investing in more expensive AGMs (even though they may be lower grade, not comparable to Lifelines) he absolutely must also consider how he's going to effectively charge these batteries, which will be even more important if he plans in the future to expand to four 6 volts and a solar system, as he has earlier suggested. By now I'm sure the OP understands this isn't just about batteries, it's about a battery system, a concept I'm convinced many RV owners just don't appreciate, as evidenced by those who decide to "upgrade" from a single flooded battery supplied with the trailer by the dealer to a pair of 6 volt AGMs and call it good without giving a moment's thought to how they're going to best maintain those batteries. My bet is this happens a lot more often than we would think. :R

As an aside, even though I'm a "limited" battery user myself I've bookmarked this excellent discussion for future reference as IMO it's one of the best we've had on the subject recently here on the forums. :B

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Charging a Battery Bank

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