Question about adding 2nd battery and switch

wvcampincpl · 04-19-2012, 02:49 PM

Am considering adding a second battery to our TT. Also would like to add a switch. Have some questions.

I understand how to wire the batteries in parallel. Since I am not depending on a battery to start an engine like with a boat would I be better off to wire the batteries in parallel and put a disconnect switch between them and the TT or if I use a 4 position battery switch (off, 1,2, both) can I use that instead of wiring the batteries in parallel?

I guess maybe that is my real question, does a battery switch on "both" serve the same as if the batteries are wired parallel?

Triguy · 04-19-2012, 02:59 PM

I have a disconnect that only works on one bank because of my two 6-volt setup, but I would do it this way if I had two 12-volt batteries.

Using a disconnect like this ...

I would wire like this which would give me a choice of either battery or the two together (in parallel)....

TURBS · 04-19-2012, 03:05 PM

Triguy is correct and its also how mine is wired

Triguy · 04-19-2012, 03:40 PM

It just occurred to me that the diagrams could be clearer. Those were from Blue Sea who caters to boaters. Here's some direction catering to campers if and when you do this...

Disconnect the negative from your original battery (battery 1).
Install positive from battery 1 to terminal one on the switch.
Install positive from battery 2 to terminal two on the switch.
Install wiring from the trailer (that had previously been wired to the positive on battery 1) to the common terminal of the switch.
Make sure selector is "OFF"
Attach a ground from battery 2 to the frame.
Reattach the negative cable to battery 1.

pony express · 04-19-2012, 04:34 PM

Quick question guys new to the battery disconnect so if you hook these up as you have said when you pull the battery disconnect will it disconnect both as well . thanks

TURBS · 04-19-2012, 04:51 PM

U can run 1 or 2 neither or both

jar3316 · 04-19-2012, 06:00 PM

My old RV had a switch like this but had been wired with 2 current blocking diodes positive side of both diodes hooked to load (house side) and then negative side of each to bat 1 and 2 respectively. This allowed both the batteries to charge but not drain in any position, but once the battery was selected the power could flow freely in both directions on that battery.

wvcampincpl · 04-20-2012, 07:33 AM

Thanks for the replies, quick follow up. I am assuming (dangerous I know) that if I am using a switch and have it set on "both batteries" for example if the convertor is running then both batteries would be getting charged, correct?

TURBS · 04-20-2012, 07:34 AM

Correct!

Triguy · 04-20-2012, 07:55 AM

I am glad we all could help you, wvcampincpl!

Jar3316 - that's an interesting idea with the diode. I would have never thought of that.

Triguy · 04-20-2012, 07:57 AM

Being very basic here, but getting back to your first post about adding the second battery. You will want to match the new battery with the old. This means type and size, of course, but also matched closely in age.

TURBS · 04-20-2012, 08:02 AM

I agree with triguy 2 of the same age batteries is a must.
If yours has some age replace them both.
if yours is fairly new then get another of the same model and size.

wvcampincpl · 04-20-2012, 09:54 AM

Got the TT last year so battery is only a year old but when add second my thought was to replace with 2 identical batteries as that seemed to be the recommendation I seen in almost all posts on here. Right now more or less thinking ahead of improvement projects I can do. As well as an excuse to tinker with things!

acadianbob · 04-20-2012, 09:56 AM

Quote:

Originally Posted by wvcampincpl

Am considering adding a second battery to our TT.

May I take this discussion in a different direction? I want to ask WHY you are considering a second battery. IMO, there is only one really valid reason; that is extended and frequent dry camping. And even then, it is unnecessary, IMO, if you have a generator. We go for 2 weeks with one 12 volt 130 amp Trojan. I run the genny a little in the morning for the microwave and DW's hair drier. I run it a night for a bit during dinner. We never have a problem. 2 batteries will give you more initial power, but, once that is gone, you are into the genny anyway.

I suppose if you want to go 3 or 4 days and then go home, 2 batteries allow you to never use a genny. I'm not picking on you guys with 2 batteries. Am I missing something here? I just have never had a problem with 1 battery.

OK, 1 exception. Couldn't get an electric site and no gennies allowed in WI/MI state parks. Got really cold and needed the furnace. After 2 days, we were out of battery and needed to move. But that is pretty exceptional.

Bottom line is it seems like a lot of expense unless you REALLY need to do it. Just asking the question before you go through all of the work and expense.

jar3316 · 04-20-2012, 10:07 AM

well if your like me you run a cpap machine on a pretty high setting and it drains the battery in a cold environment pretty quick, couple that with no gens in quite a few state parks in CA and there you have it. I have a honda 2000 gen but the second battery is also a good piece of mind for about $100ish for the bat, box, switch, and wire.

wvcampincpl · 04-20-2012, 10:16 AM

We actually did have battery issues on our first trip of the year. We were in the mountains last week and it snowed, first 2 nights were in the 20's. Needless to say we used the furnace. We had a generator and ran it a couple hours each morning and about 3 hours each evening.

The first night no problem but the 2nd and 3rd nights the battery ran down enough overnight between the cold temperatures and the draw of the furnace fan that the fan could not run which meant the furnace could not run. This didn't seem to happen until about 5 or so in the morning so it was no huge deal, got up and turned the generator on and was back in business.

Almost all the camping we do is at dry locations, which is one of the reasons we got the generator. I guess I like being prepared or over prepared. I'm probably going to get a charger as well instead of relying just on the convertor. Always thinking what if generator won't start, have times when I can't use it, convertor goes out, so on.

**Terier** · 04-20-2012, 10:31 AM

I just had a second battery added to my trailer. Also upgraded the original battery at the same time since the set up will only be as strong as the weaker battery. I don't have a generator nor do I expect to buy one based on my style of camping.

There was a good point made about whether or not a second battery would really be worth it if you have a generator. There were good points also made supporting the second battery choice. Either choice is food for thought. Good luck with your decision.

jar3316 · 04-20-2012, 10:57 AM

Quote:

Originally Posted by wvcampincpl

I'm probably going to get a charger as well instead of relying just on the convertor. Always thinking what if generator won't start, have times when I can't use it, convertor goes out, so on.

My honda gen has a 8 amp battery charge setting when I need to charge batts off the gen I use that the converter (i am told) is not a battery charger and can effect the battery if used to bring the bat from dead many times. I don't really know if this is true but I do know that the batteries will charge up faster than converter alone.

My father in law has always used his truck to bring up his batteries when out, says all he needs is to plug back in and run the truck for about 15 min each battery. Honestly I don't have any numbers to back this up but it seems to work for him. His batteries seem to last as long as mine and other than that system he has a 15x15 HF solar charger for when its stored.

**Herk7769** · 04-20-2012, 11:21 AM

One of the better documents I found on care and feeding of "house batteries"

There is also an excellent thread in the FAQ section.
Lots of real bad "I heard that ..." and "Urban Legend" information out there.
Most of it is "dead" wrong.

Triguy · 04-20-2012, 11:39 AM

Jar - Your Honda generator will certainly be faster than the converter (which does have a charger).

Your trailer's charger is probably a wfco three-stage and its fine. It is not good enough to charge a truly dead battery, but no charger can bring back the dead.

I can't explain why your dad's batteries would charge that fast. I would guess that the 15 minutes your dad uses to charge his batteries is applying a surface charge only. I know it takes hours for my batteries to charge from 50%. Even when I had a group 27 on an old camper, it would take hours for the absorption charge and hours longer after it hits about 90% charged.

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