Originally Posted by Camper_bob
It seems like ideally they should be the same age and type, but would one of a different age (while not ideal) work to add a little "umph" to my system?
What happens with a battery as it ages, its internal resistance changes with time. Just like when we age things change. Even if you maintain your battery as directed and have never dropped below the 50% battery level (which is 12VDC) the aging process still continues. The issue when adding a 2nd battery to the system is that the internal resistance does not match that of the existing battery.
When the internal resistance of each battery is different so are the charging needs of each battery (older battery needs more/longer charging than the newer one). On the outside you may not notice a difference in voltage, but the Ah output is affected. So the 2 batteries average out the voltage and the TT's battery charge controller is looking at an average voltage and not the actual battery voltage (the newer battery voltage drops and the older battery voltage increases). Whereas with 2 matched date/month/Ah/mfr the internal resistance of each battery is very close.
When you have disconnected shore power and you are on battery power, the older battery becomes a load to the newer battery and you have a reverse charge, where the newer batteries excess power (greater than old battery) is heading into the older battery. Batteries connected in parallel eventually (with load) will seek an equal level. As time goes on the newer battery ages faster because of this and will eventually be at the same output of the old battery. So the life-cycle of the newer battery is then reduced dramatically.
The rule of thumb is that the batteries be manufactured in the same month/year. They need to be identical, manufacture, model, voltage, and rated Ah. So when you go shopping you need to look for batteries that have the same month/year and do not have a lot of shelf life (storage) as many places do not properly maintain there batteries while sitting on a shelf. When you decide on a specific battery mfr, log on to their website and get the date code (month/year) conversion information, so you can figure out the code on the batteries. When I purchased mine, they originally brought out 2 batteries that had different mfr months and took the older one back and replaced it with the same mfr date as the newer one. I purchased them in the month of May and they were mfr in April of that year, so I was happy. They were a main distributor and had a fast turnover of batteries.
As for which is the best, that is another one of those questions that has a lot of answers. Research is your best tool in selecting the proper battery to meet your needs
. Your budget will be a big part of your decision.
You indicated that you want to spend a 2 or 3 days off the grid, so you need to have an idea as to how much energy you use before thinking about a specific batteries. If you use a lot of energy even the bigger Ah batteries may not meet your needs either, which would become costly should you continuously drain the batteries below the 50% level (12VDC point). You need to do an energy audit, just like at home before you pay the big $$$ for batteries.
OK, now with that being said and you have a basic understanding of what happens with old/new batteries connected, if you are not one that is used to following the 50% rule or check your batteries water level regularly (if off grid I check mine at least once a month with SOLAR charging), I would recommend adding an another inexpensive battery (same mfr/model/Ah) like the one that you already have and use them as a learning experience
. You may not get a long period of time out of them (a couple years), but you will have learned the requirements for dry-camping on a set of inexpensive batteries, and you may not even like dry-camping, so you will not have to sink $$$ into unneeded batteries.
If you want there is additional information on batteries on the "RVing with SOLAR
" social group, it mostly has SOLAR info, but some on batteries.
Do not rule out a small generator.
2013 Jayco Eagle 284BHS
250Watt Grape Solar Panel, MorningStar MPPT 60 Charge Controller
1500 Watt Ramsond PSI, 2 Trojan T145 Batteries (260Ah)
2 - AirSight Wireless IP Cameras (used as rear view cameras)
EnGenius WI-FI extender, D-Link wireless (n) modem
MagicJack Internet Phone
2012 Ford F150XLT, EcoBoost w/3.73
157" Wheel base, HD Towing Package
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