Charging a Battery Bank

Thanks, BFL13. I'll keep using the trickle charger. Time to add an outside connector to the battery for convenient charging I guess.

I would advise the OP to start w/ just 2 batteries.
4 batteries are not ALWAYS better than 2.
Batteries eat hay, meaning every battery you have is costing you money(bad)
Batteries are heavy, dead weight (bad)
4 batteries will most likely not get as close to fully charged as will 2 (bad)
If 2 batteries are enuff, then yes, 4 batteries are too many.

And last of all, in a failure situation, the only thing worse than 2 dead batteries, is 4 dead batteries !!

Harvey51 wrote:

BFL13 wrote:
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.

I am confused about this. I think it might indicate there is a solution to my problem with a 25 year old 3/4 ton GM van which is rarely driven more than 4 blocks between starts. The battery doesn't fully recharge and gradually sinks to the dreaded 12.0 volts in winter here in northern Alberta. The new alternator is supposed to be good for 90 amps. It does apply 14.4 volts to the battery. It seems to me the battery should recharge fully at 90 amps for 15 minutes after a start. If the battery does not have an internal resistance limiting its acceptance of current, what is the limitation? Is it the cable from alternator to battery? If so, I can get a second cable and double the rate of charging! Maybe the cable connectors are corroded and a simple replacement will solve the problem. Or does the 14.4 volts on the battery mean all is well with the cable?

Not up on starting battery recharging, but the 14.4 volts is good. The 15 minutes is not enough time, that's all. The van needs to be kept on one of those engine battery maintenance chargers between trips like they have for motor homes.

I use one of these (wait till they come on sale again for half price or whatever) It sits at 13.4 volts forever after starting off at 14.2 for a short time.

http://www.canadiantire.ca/en/pdp/0111506P.html

I was referring above to deep cycle batteries which will accept the high amps until they get up in voltage at say 75% SOC when amps will then taper for some hours before the batteries are full.

I don't know how long it takes for a starting battery to get to true full after it reaches near that 14.4 volts, but it will take a while. Also the alternator voltage drops from that 14.4 soon after starting, which slows down the recharge.

The main point is that the battery does not accept the 90 amps until it is full. It only accepts high amps till it is part full, then amps taper for the Absorption stage which takes some time.

BFL13 wrote:
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.

I am confused about this. I think it might indicate there is a solution to my problem with a 25 year old 3/4 ton GM van which is rarely driven more than 4 blocks between starts. The battery doesn't fully recharge and gradually sinks to the dreaded 12.0 volts in winter here in northern Alberta. The new alternator is supposed to be good for 90 amps. It does apply 14.4 volts to the battery. It seems to me the battery should recharge fully at 90 amps for 15 minutes after a start. If the battery does not have an internal resistance limiting its acceptance of current, what is the limitation? Is it the cable from alternator to battery? If so, I can get a second cable and double the rate of charging! Maybe the cable connectors are corroded and a simple replacement will solve the problem. Or does the 14.4 volts on the battery mean all is well with the cable?

RobWNY ... I recommend going with four(4) batteries if you have the budget and room in your RV.

The reasons for this are subtle, such as:

- If want to RV with a Boy Scout attitude then you need to be ready for a variety of situations, which in general includes having a large as possible amount of energy storage.

- The more batteries you have the longer they last with light average usage when camped, because batteries last longest when discharged the least amount during each usage cycle.

- You could wind up camped with hookups in a campground that experiences an extended power outage.

- You could wind up camped with hookups in a campground during an extended lightening storm in which you wish to disconnect from shore power to prevent lightening discharge travel through the cabling into your RV.

- You could wind up camping without hookups but being stranded an extended length of time due to equipment failure or bad weather.

- With four 6 volt batteries and one of them ever experiences catostrophic failure, you can then still have 12V power on board via two of the three remaining good batteries.

- You could wind up stranded for an extended time in a massive highway traffic jam due to unexpected weather, earthquake, flood, bridge failure, forest fire, etc.. such that you need to hunker down in the RV along the road.

- If you're able to store your RV at the location of your personal residence, then you may want to live in it for several hours/days without hookup power while remodeling work is being done on the residence requiring shutting off of the power at the property.

Having solar on board and a generator on board can also be justified as additional backup in situations such as the above.

RobWNY wrote:
Do you just not like anything about me SoundGuy? You have been putting me down with every post you've made regarding my questions.

Huh? :h Here I am trying to offer useful suggestions that could save you considerable $$$, time, and effort installing batteries you may well not need and this is your response?! No worries, I won't even bother reading the rest of your post. :R Good luck with whatever you decide. :)

I will make this simple as possible.

For charging your "Battery bank" it does not matter if you have a row of 12 volt in parallel. Or two rows of six volt in serries/parallel. or a hugh 3,000 pound Fork Lift battery, or ________.

Electrically you have a battery. Now the amp hours will vary from one "Bank" to another (And by the way I've used that fork lift battery) but you charge them all together as though they were a single battery.


Exception.. If there is a problem. THEN you separate each 12 volt set (Either each 12 volt or each PAIR of six) so as to isolate, But otherwise treat them as ONE BIG battery.

Do you just not like anything about me SoundGuy? You have been putting me down with every post you've made regarding my questions. Not everyone is as well versed in this stuff as you are. Apparently not many are. I certainly appreciate your input and knowledge on all of this but I can really do without the sarcasm and smugness of your replies. You pick apart every word I say. I never claimed to be an expert or even partially knowledgeable on this topic so I come here to ask questions and to learn. Not to be berated. Besides, what I do or how much money I spend is really my business. Just because you don't like anyone's opinion other than your own, be a little more understanding that we aren't all in the same place knowledge wise with every camping situation. As for the generator I bought, I have other intentions for the use of a generator besides bringing it with me camping. They are always handy to have for many reasons. That played a role in my decision on what unit to buy. Furthermore, I haven't made a decision on how many batteries I will buy. I know I have the room to put 4 batteries behind my propane tanks if I choose to get that many. Just because I haven't posted dimensions or a photo of it, doesn't mean I haven't made sure that 4 would fit. To answer your thoughts on why I would even consider buying all of this now rather than wait until I knew if I needed it? It's because it's much easier to pay for these things now while I'm still working than it will be after I retire. Sure there's a chance I will spend more now than ends up being necessary but I'd rather have it and not need it than need it and not be able to afford it later on. I guess we have a different philosophy regarding that. It doesn't make either of us wrong, it makes us have a difference of opinion and nothing more than that.

Out of curiosity I just Googled battery prices for a Trojan T105-AGM and it seems ~ $250 US per battery is about average ... this is one example. Certainly there could be better deals out there but that's $1000 US for the four the OP is talking about, not to mention what he's already spent for a genset, plus any more $$$ he may have to expend to properly install four GC-2 batteries like this. For someone who dry camps regularly, perhaps wants to also power an inverter, and may already have a genset and/or suitably sized solar system I can see the justification for such an investment ... BUT I sure don't see the logic for someone like the OP who "thinks" he may like to do a "little" dry camping in the future, who currently has no idea what his dry camping power requirements might be, and may well not even have a charging system suitable for properly maintaining four T105-AGMs. Needless to say, that's a heck of a commitment for a few days of dry camping! :E

RobWNY wrote:
MrWizard, 4 batteries was my original plan but SoundGuy thought it was way more than what I would need. Now I'm only more confused. There seems to be a difference of opinion on how much power is needed. When I get the prices of the Trogan AGM batteries, I'll buy what I can afford.

It's unfortunate you're "confused" as the issue really is quite simple. :) This entire discussion started with you saying you almost always camp on electric sites, sometimes even full service sites, only seldom dry camp, but are now planning a 4-day dry camping trip in the fall with friends. To that end you've since purchased a new 3000 watt genset and are now planning on replacing your single flooded battery with FOUR 6 volt GC-2s, originally flooded IIRC, but now with much more expensive AGMs - in total a significant investment. :E Yes, you've since clarified your retirement plans may (or may not) include more dry camping but at this stage you say you have no idea just what your dry camping power requirements might be, nor have you said anything about how you would mount 4 batteries (which in itself may involve spending even more $$$), nor AFAIK are you even considering an inverter which itself could then justify the expense of 4 GC-2s over just 2. JMO, but your approach of simply throwing your wallet at a problem to make it go away is what is "confusing", especially since you have the option before you of starting with just 2 6 volt batts and seeing how it goes ... if after a few dry camping trips that proves need for 2 more batts then so be it, at least you then know what you're up against.


In a previous post MrWizard said -

"i've never meet anybody who said they had two much battery power
and they should have bought less batteries" ...

Well, I have - ME! ... and the countless others, including yourself, who mostly camp on electric sites, only occasionally on dry sites. Upgrading from a single G24 to a single G31, or adding a second G24, or even upgrading to a pair of GC2s is IMO a reasonable intermediate step, but if one later decides more is required then that's the time to go further with it. I've been through this exercise myself, have chosen to just stick with my existing G27, and load support (4 pics) with my truck those few times each season we may find ourselves without shore power. Eventually that aging G27 will need to be replaced so at that time I'll mostly likely upgrade to a single G31 AGM or at most a pair of GC-2 AGMs, but no genset because past experience in owning 2 different EU2000i gensets proved how little they were actually used. :R

There are those on these forums more than willing to offer ultimate solutions, more than willing to spend your $$$$ with recommendations, but will they be there when it's time to pay for all that gear, be there to mount it, to wire it, or pay for whatever other items (such as a better converter or a larger battery box) that may be required to install and better maintain that equipment? The answer to that shouldn't be confusing at all. ;)