Battery power

[Speckul8r]

Why not go with AGM batteries?? Totally maintanence free, don't freeze, truely deep cycle. I have a pair of these on my boat for the trolling motors and they are so much better than the lead acid group 27's that I used to have there is no compairison. More expensive than the lead acid but you get what you pay for, in this case. Gels may even be better but they are really expensive. I just (3 weeks ago) bought a 2720 and it came with a lead acid but when it starts giving up, I'll be looking real hard at a different battery type. Also, if you look at the discharge curve of an AGM, it is much flatter, longer than the lead acid.

[Caver]

As an engineer I'm always faced with making design decisions and you have to decide what you’re trying to optimize since there is usually no one size fits all solution. That seems to be the problem we have with our TMs. I love the TM for boondocking and the solar panels have kept my batteries charged in the situations that I camp. My wife doesn't understand why we can't run the AC given nearly $1000 investment in solar components.

If I were going to use a generator I would consider two of the EU2000s with the parallel kit which should run the AC. That way I would have the option of taking none, one, or two generators depending on the trip requirements. However, the EU2000s don't have the remote start capability of the EU3000.

I had the same problem not being able to mount the T-105 6 volt batteries due to the height available with the swing tongue so I just went with the two flooded 12 volt batteries for now. I would like the replacements to be AGM but I'm concerned that the constant 13.6 volt output from the 7300 converter is much higher than the max 13.32 volt float voltage recommended for the Concorde AGM batteries. A multi-stage charger would be a better match for these. At least with the flooded batteries I only have to add distilled water a few times a year and don't have to worry about damage due to overcharging. I haven't found it very difficult or time consuming to periodically water the batteries mounted on the front frame.

I'm not familiar with the new converter that TM is using but for the 7300 it should be possible to insert a silicon diode with a shorting switch. This would allow reducing the output voltage when you are on shore power for an extended period of time and then switching to the higher voltage to more quickly charge the batteries. Unfortunately the AGM batteries are best charged at an initial 14.1-14.4 volts. I set my solar charge controller at 14.1 volts but if I were charging AGMs from a generator with the 7300 converter it would take a long time to reach full charge.


I guess I'll stick with the flooded batteries for now. However, I'll be interested in the experiences from other TM owners as they look at alternate batteries.


A point that I have learned from the solar power forums is that when connecting batteries in parallel it is best to connect the positive and negative load to batteries on the opposite ends of the string and not to one battery. This helps distribute the load/charge more equally given the finite resistance of the cables between the batteries.

Keep your flooded batteries watered. Ray

[RockyMtnRay]

Originally Posted by Speckul8r

Why not go with AGM batteries?? Totally maintanence free, don't freeze, truely deep cycle. I have a pair of these on my boat for the trolling motors and they are so much better than the lead acid group 27's that I used to have there is no compairison. More expensive than the lead acid but you get what you pay for, in this case. Gels may even be better but they are really expensive. I just (3 weeks ago) bought a 2720 and it came with a lead acid but when it starts giving up, I'll be looking real hard at a different battery type. Also, if you look at the discharge curve of an AGM, it is much flatter, longer than the lead acid.

AGMs do indeed have great deep cycle and low maintenance characteristics. However, unless something's changed since I last investigated AGMs a couple of years ago, their power density (amp hours per battery) was a heckuva lot less than from a true deep cycle battery of the same size such as a Trojan 105 Golf Cart battery ...or even from a quasi deep cycle RV/Marine Starting battery like the Group 27s or Group 24s. My recollection was that an Optima AGM of the same dimensions as a Group 27 (~115 amp hours) had only about 55 amp hours of capacity. By contrast a true deep cycle flooded cell battery like the T105 has around 225 amp hours of capacity (granted you need two of them).

Since I usually camp at high altitudes where the mid summer temps are in the 30s at night and therefore run the furnace 3 to 5 hours a day even in July and August, it's not uncommon for me to use 60 to 80 amp hours every day between 6 pm and 8 am. The dual T105s (in conjunction with a 170 watt solar array) can almost indefinitely and readily meet my admittedly very high daily power demands. The Group 27 I originally had certainly couldn't (even with the solar panels) and the AGMs I've seen so far wouldn't either.

I've found the T105s to be nearly maintenace free...I only need to add water twice each year (once in the spring, once in the fall) and no worries about discharge/freezing since I keep the trailer on a float charger year around when it's not in use (the trailer is stored in my garage so keeping a charger hooked up is not a problem). I also expect to get 8 to 10 years of service from the T105s due to their exceedingly thick plate design and robust construction.

[Caver]

As Ray pointed out the Trojan T-105 are rugged and should give good RV service. That was my choice but they didn't fit. Another point is that they are less expensive than the alternatives because they are usually available locally since large quantities are used for golf carts and electric fork lifts.

The AGMs have comparable AH/weight and volume as the deep discharge flooded batteries. Concord even has a 6 volt AGM battery that is almost identical to the T-105 in capacity and size.

Here is the Concord RV link:

http://www.lifelinebatteries.com/rvbatteries.php

Here is another good source of battery information:

http://www.windsun.com/Batteries/Battery_FAQ.htm

[RockyMtnRay]

Originally Posted by Caver

As Ray pointed out the Trojan T-105 are rugged and should give good RV service. That was my choice but they didn't fit. Another point is that they are less expensive than the alternatives because they are usually available locally since large quantities are used for golf carts and electric fork lifts.

The AGMs have comparable AH/weight and volume as the deep discharge flooded batteries. Concord even has a 6 volt AGM battery that is almost identical to the T-105 in capacity and size.

Thanks for the links and info re these Concorde AGM batteries, Ray. My local battery suppliers (multiple) only were aware of Optima brand starting type AGM batteries and those definitely did not have high energy density.

I'm still glad I bought the T105s though...as noted above, they've been nearly maintenance free for me (twice a year watering is not a huge burden, IMO); the expected lifespan is probably similar to the AGMs in my usage; and they were an easy fit in the rear storage compartment of my 2720SL. Furthermore, I was able to buy them at a nearby battery store and only paid $136 for a pair (that price includes sales tax). They were already filled; all I had to do was bring them home and install them in the trailer.

The best web price I'm finding for the Concorde equivalent is about $165 each ($330 for a pair)...list is around $250 each ...and there will definitely be a hefty shipping charge on that much lead. I'm definitely not suffering from buyer's regret in purchasing the T105s.