Going from one battery to two

[jimmy2546]

When we picked up our new 397thr it only came with one battery. I may eventually switch over to lithium but for now I just want to add an additional battery to make sure our residential refrigerator works during travel and occasional parking lot boondocking. We almost always be hooked up to shore power except when traveling or maybe an occasional boondocking weekend. My question is, when adding the second battery is there anything else I need to do other than connecting the two batteries together with battery cables? My battery currently has a generator, inverter and solar hooked up.

[Jimmer]

When I first got my Reflection Travel Trailer, it came with one lead acid battery. I added a second and connected it up in parallel (Negative to Negative, Positive to Positive. It worked fine without changing anything (until I upgraded to 5 Battleborn batteries).

[StephenO]

You should be good to go connecting a second battery in parallel with your existing 12v with heavy gauge connector cables. I believe you should try and keep the battery chemistries the same though, IE both traditional LA, or both LA AGM, but hopefully someone with more experience will weigh-in there.

[WickedJulesTikiAl]

You should be good to go with a couple of caveats. 1. The age of the original battery…you don’t want to mix older and newer lead acid batteries. If the original is fairly new…no problem. 2. Make sure you hook up in parallel…not series. Parallel maintains your 12 volt system…series turns it into a 24 volt system.

[DarnDave]

jimmy2546 I hate to be Darndave downer, (Debbie's little known big brother) but I think you will find that even with two batteries, you will be challenged to make it thru the night with that res refer. Especially if you like tv, lights, fans, etc. We have four new very expensive 6 volt AGM batteries which we probably didn't need. The night before leaving on our thanksgiving trip, I hooked the truck to the trailer (which had been plugged in for weeks and unoccupied), pulled it out of the rear yard and into our driveway, where we also have an electrical hookup. I didn't plug in, thinking "its just one night". I also neglected to unplug trailer cord from truck. And in the morning, everything was dead. After the trip, (which went well with no further issues thanks to hookups) I ordered new, bigger batteries (again, 6 volt) and decided to install them myself. I had originally trusted that the dealer knew how to correctly install batteries (that I supplied) since every RV has at least one. For whatever reason, they had one pair (wired series/parallel to make 12 volts) attached to the trailer house wiring as you would expect. The other pair were connected only to the generator (like a really expensive starter battery). So now I have four batteries out in the garage there is nothing wrong with.

If you are only able to do two batteries for now, I would abandon the dealer supplied (probably cheapest thing they could buy in quantity) battery and install the largest pair your budget will allow. I would recommend two 6 volt units vs two 12 volt. They are more tolerant to deep discharge. FWIW, I looked into the lithium option and couldn't make a cost case for it in our situation. We almost always have hookups; two nights boondocking is a very rare exception to our routine. We get thru one with no problems, and don't have to worry about power conservation.

[WickedJulesTikiAl]

jimmy2546 I hate to be Darndave downer, (Debbie's little known big brother) but I think you will find that even with two batteries, you will be challenged to make it thru the night with that res refer. Especially if you like tv, lights, fans, etc. We have four new very expensive 6 volt AGM batteries which we probably didn't need. The night before leaving on our thanksgiving trip, I hooked the truck to the trailer (which had been plugged in for weeks and unoccupied), pulled it out of the rear yard and into our driveway, where we also have an electrical hookup. I didn't plug in, thinking "its just one night". I also neglected to unplug trailer cord from truck. And in the morning, everything was dead. After the trip, (which went well with no further issues thanks to hookups) I ordered new, bigger batteries (again, 6 volt) and decided to install them myself. I had originally trusted that the dealer knew how to correctly install batteries (that I supplied) since every RV has at least one. For whatever reason, they had one pair (wired series/parallel to make 12 volts) attached to the trailer house wiring as you would expect. The other pair were connected only to the generator (like a really expensive starter battery). So now I have four batteries out in the garage there is nothing wrong with.

If you are only able to do two batteries for now, I would abandon the dealer supplied (probably cheapest thing they could buy in quantity) battery and install the largest pair your budget will allow. I would recommend two 6 volt units vs two 12 volt. They are more tolerant to deep discharge. FWIW, I looked into the lithium option and couldn't make a cost case for it in our situation. We almost always have hookups; two nights boondocking is a very rare exception to our routine. We get thru one with no problems, and don't have to worry about power conservation.

I can’t disagree with “downer Dave” in anything he wrote. I actually bit the bullet and did a lithium upgrade for the exact reasons brought forth. However cost is a huge consideration and, unlike the OP’s situation, our rig doesn’t have a generator, inverter or solar. All of those things extend the useable amp hours of dual lead acid batteries.

[jimmy2546]

The only other question I would have is after connecting the two batteries in parallel should I connect the in flow terminals like solar and generator to different positive and negatives than the out flow terminals like inverter and coach power. ?? Or does everything get hooked up to the same positive and negative which would obviously be positive on one battery negative on the other.

[howson]

jimmy2546
-- best practice (as explained to me) is shown below. (Remember I'm just an owner like you...)

[Country Campers]

Do not forget to vent the new battery similar to the stock battery.

Brian

[jimmy2546]

jimmy2546
-- best practice (as explained to me) is shown below. (Remember I'm just an owner like you...)

Yea. That's the duel battery parallel connection. I understand that. What about the power in and power out ? I do know if I was only connecting the camper I would attach positive to one battery and negative to the other. I'm just wondering about all the other connections such as generator, solar and inverter?

[StephenO]

I'm just wondering about all the other connections such as generator, solar and inverter?

Short answer is, it's the same, in that you would connect them to the same positive and negative points. That's assuming that the solar, inverter, etc. connect directly to the battery now. IE, in addition to the trailer positive and negative cables connected to your battery, you have connections for those elements. If they don't, and that they connect somewhere else on the DC system, you won't need to do anything different, and just connect up the batteries.

[Trrbossman1]

I worked on many different truck and trailer units which have additional accessories added. We always follow the manufacturers recommendations and they strongly suggest to NOT hook all accessories to one battery. They also say to connect the positive terminal to one battery and the negative to another battery. Never had any issues. I’m not an electrical engineer I’m just stating what I have been experienced to.

[DarnDave]

If you decide to add another 12 volt battery to your existing (it would need to match--brand and capacity and group size), I would follow Howard's diagram; above. There is a different diagram for dual 6 volt system.

[familytruckster4]

I added a second battery but I am struggling to find a vent kit anywhere. Amazon and E trailer dont show anything. I have seen systems that had a "T" in the top of the main case and the hose from the second battery connects there. If someone has a source please share it with me.
Thanks
Scott

[Cate&Rob]

familytruckster4
Hi Scott,

For my second battery, I got the box, vent line and outlet from Grand Design (through my dealer) and installed a “mirror image” battery through the front compartment floor on the curb (right) side. There are pictures of this somewhere on this forum, or I can repost if you are interested in this idea.

Rob