For several years now I have been conducting a battery life expectancy test with my diesel motorhome. In January 2015, we arrived at Quartzsite for a winter stay, our first shot at Q. Shortly after arriving, it became obvious my house batteries were not in shape for a long boondock stay. I have four 6V house batteries, 2 each in series, connected in parallel. I disconnected all four and tested voltage and it seemed I had two low batteries out of the four. Since I was driving into Phoenix anyway, I stopped at the Interstate Battery store along I10 and bought 2 new GC2-XHD-UTL, 232Ah deep cycle batteries which I installed upon my return.
Of course, best laid plans and all that, I still did not have sufficient power and (since I was not going to Phoenix) decided to replace the other two with Trojan T-105s with 225Ah@20, and 185Ah@5hr available locally in Q. All this took place within a couple of days. My goal was to see which batteries lived longest.
It is now 6 years later and all four are chugging along with no problems. During this time I have monitored water level, and kept the batteries and connections all clean. I have a Magnum Inverter/charger with 3 stage charge function. During the 6 years, I have had to add a nominal amount of distilled water, barely enough to mention.
Last year I took a trip from Ohio to Arizona (four months, july,August,Sept.,Oct), and back. This year we are spending the winter in Florida and two days ago I checked my water. Interestingly the Interstates took the typical nominal water charge, barely 1/4 cup. Meanwhile, the Trojans required a full cup in each cell!
I was surprised by this information and now will keep a much closer eye on those two as I take this as a sign of possible beginning failure.
I'm happy with 6 years out of both sets, just curious about the final outcome. I now have to decide if I will change all four when one or the other fails, or keep the winner going until...........
Of course, best laid plans and all that, I still did not have sufficient power and (since I was not going to Phoenix) decided to replace the other two with Trojan T-105s with 225Ah@20, and 185Ah@5hr available locally in Q. All this took place within a couple of days. My goal was to see which batteries lived longest.
It is now 6 years later and all four are chugging along with no problems. During this time I have monitored water level, and kept the batteries and connections all clean. I have a Magnum Inverter/charger with 3 stage charge function. During the 6 years, I have had to add a nominal amount of distilled water, barely enough to mention.
Last year I took a trip from Ohio to Arizona (four months, july,August,Sept.,Oct), and back. This year we are spending the winter in Florida and two days ago I checked my water. Interestingly the Interstates took the typical nominal water charge, barely 1/4 cup. Meanwhile, the Trojans required a full cup in each cell!
I was surprised by this information and now will keep a much closer eye on those two as I take this as a sign of possible beginning failure.
I'm happy with 6 years out of both sets, just curious about the final outcome. I now have to decide if I will change all four when one or the other fails, or keep the winner going until...........
time2roll wrote:larry cad wrote:
I would be interested in your calculation to support this statement. I assume you know the internal resistance of the two types of batteries, and also the resistance of the jumper wire between the two series sets of batteries. No doubt you included the resistance of the series jumpers as well.
By the way, the calculated resistance of the jumper wires, (both the series connections and the parallel connections) are .000047 ohms. If I were ever to pull full load (i.e. 400amps) through any one of those jumpers, the voltage drop calculates out to be .0188 volts DC which is .00156% of the 12vdc
http://www.smartgauge.co.uk/batt_con.html
Calculated resistance for EACH of the four jumpers is .000047 ohms. The jumper wires are rated at 400 amps DC, but would almost never exceed 60 amps. Voltage drop between the two positive leads in that condition would be .00281vdc. To me that sounds a lot like balanced.
pianotuna wrote:
Hi Larry,
Treat each pair of six volt batteries as if they were a single twelve volt battery. Wire them in a balanced manner. (see below)
Yes, this is exactly what I have. Only difference is that I have 2 (two) positive feeds from the parallel set. One feeds my 12v fuse panel, and the other feeds my inverter/charger. One feed is connected from the rear positive post, and the other feed is connected from the front positive post. There is a jumper between those two positive posts consisting of 400 amp copper wire which serves to balance the loads. There is a single, negative wire which is firmly attached to the chassis of the coach.
Keep in mind that these batteries do not feed the motor starter as there are two more batteries to do that job and they are not connected to this array.
Hi Larry,
Treat each pair of six volt batteries as if they were a single twelve volt battery. Wire them in a balanced manner. (see below)
Treat each pair of six volt batteries as if they were a single twelve volt battery. Wire them in a balanced manner. (see below)
