Charging the batteries with converter?

TMfor4ofus · 01-12-2017, 03:16 PM

We recently were fortunate enough to get a 2011 TM 2720. I'd like to know how effective is it use the converter to charge the batteries?? I'm assuming its all original and so how good is the converter at charging the batteries. Is it a smart or multi stage charger? It seems like after a night its charged up good. I found out it has 2 - 6v GC batteries. I was happy to see that and the date stamp says 7/15 so fairly new? We got a Westy 2400i Gen and I was wondering if I should go and buy a good 3 stage charger and power that off the Gen or is the converter sufficient? I only have 30w of solar which was okay for our 1 Gp 24 battery in our popup. If I keep them aimed at the sun and they actually get the batteries charged almost all the way on a good day if they werent discharged too much. The 30w solar is pretty useless on a cloudy winter day. I may upgrade the solar and so don't want to spend $$$ on a charger. ??
One more question is should I disconnect the batteries when sitting for even a couple weeks? Just pull the Neg terminal?

**Bill** · 01-12-2017, 08:21 PM

Congratulations on your new-to-you TM! You will love it.

As to your questions, I first need to ask if there is some reason behind these specific questions. Are you having some problems? Has someone suggested a problem?

The TM's built-in converter contains a battery charger that is very good at charging your battery. There should be no reason to consider replacing or augmenting it. It is a smart charger, which will keep your battery up very well under normal conditions. Where it fails, in my opinion, is in keeping your battery properly charged during long periods of non-use. If you put your TM in storage for a couple weeks, and leave the converter/charger powered up, it may tend to overcharge the battery a bit. For that reason, it is often suggested that if you put the trailer in storage for more than a few days, you should unplug shore power, disconnect the battery from the entire trailer, and just let the battery sit there. Some people disconnect the negative terminal - I disconnect the positive terminal. Either will work.

The real reason for disconnecting is to prevent the trailer's "phantom loads" from discharging the battery. Phantom loads can pull your battery down in only a few days, so if you plan to leave the trailer for more than that, it is a good idea to simply disconnect the battery. On the other hand, if you plan to leave the trailer in storage for a really long time - more than a couple months, say - it is a good idea to keep a "battery maintainer" on the battery. You can use the forum's Search tool to find discussion of the Battery Tender, for example.

As for powering the converter from shore power vs generator power, they are absolutely the same. No reason to do one over the other.

Bill

LoveToCamp · 01-12-2017, 09:12 PM

I am biased, but I do use solar to keep my batteries charged. I have 2 12v deep-cycle batteries (110 aH each). I initially had one 100w solar panel, which was good much of the time, but during a week of rain most of every day, the batteries didn't fully re-charge daily.

So, I put a second 100w panel on the roof, and now I have full power every afternoon, even when camping in the winter (November and December, once in January). They are just mounted on my roof, so they are not aimed at the sun.

My opinion is that 200w of solar will keep your batteries charged, unless you camp in heavy tree cover. However, I have camped under tall, seemingly thick, Ponderosa or Lodge pole pines, and even on cloudy days, I have never been at less than a full charge by evening (usually by 1 or 2 in the afternoon). Others may say fixed panels are not good, but I have used them for 5 years, and am very happy with them. I don't own a generator, and we boondock for up to 9 nights (I work, so have not gone longer).

Enjoy your TM!

TMfor4ofus · 01-12-2017, 09:41 PM

Okay thanks for the info guys. I have noticed after just a few days left alone the charge has dropped quite a bit so I either plug it in our hook it up to the solar panels on our deck above the trailer once a week. The puny 30w solar only does good if its a bright sunny day and I have them leaned toward the sun. Then it will get to about 13.4V at best for 5-6 hours now. So two things: I'll disconnect the batteries after this weekends trip. We are in a hook up site for 2 days so it should be charged good when we get home. Also look into upgrading the solar. Good to know the converter has a smart charger. It does seem to charge it up well after one night. Thanks Again.

Padgett · 01-13-2017, 08:05 AM

Agree with Love plus the caveat that when in the grove I connect a little float charger. Otherwise I would just remove the batteries and keep on a board in the garage when home.

BrucePerens · 01-13-2017, 09:09 PM

you should unplug shore power, disconnect the battery from the entire trailer, and just let the battery sit there. Some people disconnect the negative terminal - I disconnect the positive terminal. Either will work.

I am dubious that this is a good strategy, because the battery will self-discharge, and when it gets low enough, that will further damage the battery.

We don't really know yet what the converter's float voltage is and how often it might try to do an equalization charge. The temperature of the battery is also at issue. Measuring the float voltage and looking where it's stored would tell us if there is much of a chance to overcharge. It is also possible to carefully measure if any electrolyte is being boiled off over the winter.

If you don't want to run extended science experiments, a float charger that has internal temperature compensation, such as the NOCO Genius G750, might be the easiest solution, at $30. NOCO claims that that all of their chargers are temperature compensated, since it's cheap to do this is plausible. 750 mA is enough to take care of parasitic drains, so you can leave everything connected if you make sure all of the loads are turned off.

**Bill** · 01-14-2017, 11:25 AM

Quote:

Originally Posted by TMfor4ofus

... should I disconnect the batteries when sitting for even a couple weeks?

Quote:

Originally Posted by Bill

... it is often suggested that if you put the trailer in storage for more than a few days, you should unplug shore power, disconnect the battery from the entire trailer, and just let the battery sit there.

Quote:

Originally Posted by BrucePerens

I am dubious that this is a good strategy, because the battery will self-discharge, and when it gets low enough, that will further damage the battery.

Bruce -

Interesting thought. In my experience, self-discharge is vastly over-rated as a cause of problems. Why? Self-discharge is a very slow process. Online sources such as batteryuniversity.com and wikipedia agree that the self-discharge rate for lead-acid batteries is around 5% per month - a little more when it is hot, a little less when it is cold. When you multiply that out in a geometric progression, it shows that even after 6 months of storage, a disconnected battery still has around 70% charge. This is well within the rule of thumb, often-repeated on this forum, that a battery should not be discharged below 50% capacity.

My personal experience bears out this conclusion. For the last 16 years, I have owned two cars which are each used for only half the year. Each of these cars is left unattended, with the battery disconnected, for 6 months of each year - no other measures are taken. One is in a very hot place (Phoenix area summer) and one in a very cold place (Maine winter). Every year, when I return to the unattended car, I simply re-connect the battery and turn the key, and the engine starts immediately. Even after 6 months of self-discharge, it has never failed.

By contrast, far more damage is done by leaving a battery connected to the phantom loads in the trailer for a week. In that time, the phantom loads will completely discharge the Group 24 or Group 27 battery used in most TMs. Sadly, I have experienced this result as well - leaving a battery connected to the TM's phantom loads will indeed harm the battery quite quickly.

So I still think that for mid-term storage (less than a couple months), it is sufficient to simply disconnect the battery. In that time frame, the degree of self-discharge is very small, and the risk of overcharge from an over-zealous converter/charger is eliminated. I also fully support the use of a battery maintainer for long-term storage. I use a Battery Tender, and as I have written, it seems to work well.

TECHNICAL GUDGE FOLLOWS:

If anyone other than Bruce and myself cares to delve into it, here is a good technical discussion of self-discharge.
http://mathscinotes.com/2012/04/batt...ischarge-math/
This discussion includes a family of self-discharge graphs that confirm my thoughts on self-discharge. One of the stated conclusions is that "A lead-acid battery can be stored for about a year at room temperature before it needs a recharge."

Bill

tentcamper · 01-14-2017, 04:57 PM

Phantom load is the get you. I think the worst is that propane detector. But you also have the radio antenna, the radio if its installed. Also any thing you left on, plus any mods that are alway powered up.

Padgett · 01-14-2017, 05:03 PM

I have a disconnect at the batteries that removes all trailer loads & just leaves the float charger connected.

RottieMom · 01-15-2017, 07:49 AM

TMfor4ofus, if you have power where you store your TM and your battery is not easy to access like mine (which is inside the TM under the sofa), you can easily use the bargman connector on your TM and connect it to a battery tender. Bill taught me how to do this and there are some threads on it on the forum.