The house battery that was in the RV when we bought it was a Interstate SRM-4D. It finally failed. It would read 11 volts but as soon as a load was applied it would drop to 5 volts. I found this out right before a winter camping trip. I new I didn't want another SRM-4D but I didn't have time to do the research on which battery(s) I should get. So I just pulled the big SRM-4D and installed a random deep cycle battery I had sitting in my garage, a 4 year old Interstate SRM-27. Although its tiny, this worked fine for our winter camping trip since we had shore power the whole time.

Once I had some more time for research, I decided the best first step would be to get a battery monitor that would let me accurate determine our battery needs. I opted for the Victron BMV-712. I don't mind spending more on a quality product, and this thing is awesome. It requires installing a smart shunt on the negative from the battery to the ground. If I was going to be replacing battery cables, I might as well go big with some 2/0 gauge high strand count wire.

And if I am replacing any cables, I might as well add a shutoff / disconnect switch on the positive leads in case there was a parasitic load that killed my SRM-4D house battery. Running new positive and negative battery cables also had the added benefit of giving me longer leads to accomodate one small battery, one big battery, or 2 6volt batteries. I now have enough slack for any of those setups.

The installation was not hard. The longest part was making my obscenely girthy cables. I am very happy with the results. Once I had the Victron installed, I played around with the bluetooth capability and their Android app. Its very nice. I used it to measure the load applied by each different electrical component running on the house battery. By doing this in isolation, one load at a time, I got very accurate wattage/amprage numbers.

Fast forward a bit and I replaced all the interior lights with LEDs. These use about 1/4 the wattage of the original incadencents. I then went on a camping trip and measure our overnight usage. With our usage of some lighting in the evening, floor lights on at night, both roof fans going on medium, we ended up with about 60% battery capacity left over in the morning. That is great for a crappy little SRM-27 battery that only has like 60 amp hours of capacity. I don't think we need a massive house battery... we don't run an AC inverter, power the air conditioner off DC, and our fridge runs on propane. I can probably get by on this SRM-27 for a couple of nights.

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Smll Med Lrg 18 bulbs are 1141 incandecent, each uses 18 watts!	Smll Med Lrg	Smll Med Lrg Floor lights (x2) are T67, each uses 7 watts	Smll Med Lrg
Smll Med Lrg got all new LED lights to replace incandecents. In general, they use 25% the wattage	Smll Med Lrg floor lights = 67-NW12-G, all other lights = 1156-WW18-T	Smll Med Lrg	Smll Med Lrg
Smll Med Lrg The new LEDs (warm white 2700k) are a perfect color match to riginal incandecents	Smll Med Lrg	Smll Med Lrg left = LED, right = original incandecent	Smll Med Lrg
Smll Med Lrg floor lights only came in natural white (3000k). They are way too white but oh well	Smll Med Lrg	Smll Med Lrg Even replaced the range lights, both old bulbs were 1157's that used 23 watts each	Smll Med Lrg
Smll Med Lrg crappy but tiny SRM-27 battery where the SRM-4D used to be	Smll Med Lrg battery ground attached to frame here	Smll Med Lrg behind the generator, I will need to run a cable from the shunt to the gauge through here	Smll Med Lrg
Smll Med Lrg	Smll Med Lrg In the closed, I had to remove this panel to get access	Smll Med Lrg now I can see where the cables come in	Smll Med Lrg original city water connection, I never use it, leaks like crazy
Smll Med Lrg I couldn't get the signal cable (phone cable) for the gauge through that	Smll Med Lrg	Smll Med Lrg ended up drilling a new hole just for the new cable	Smll Med Lrg
Smll Med Lrg with the new hole, the cable is easily reached	Smll Med Lrg	Smll Med Lrg signal cable routed through wire hold does for armored cable	Smll Med Lrg smart shunt, good for 500 amps
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Smll Med Lrg my first 2/0 cable	Smll Med Lrg	Smll Med Lrg	Smll Med Lrg
Smll Med Lrg	Smll Med Lrg	Smll Med Lrg shunt goes between the battery negative terminal and ground	Smll Med Lrg new marine battery disconnect
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Smll Med Lrg	Smll Med Lrg the 2/0 cables are still pretty flexible thanks to the high quality, high strand count	Smll Med Lrg this old turd works fine for this application	Smll Med Lrg
Smll Med Lrg	Smll Med Lrg The Victron gauge is digital so I can't have it normally visible from inside the RV, hid it here	Smll Med Lrg	Smll Med Lrg It provides good info at the gauge, and even better info in the android app
Smll Med Lrg wattage for each load, measured with engine off, no shore power connected, incandecent bulbs	Smll Med Lrg Victron app showing that 2x LED bulbs use 5 watts, vs 18 watts for one old bulb, 86% reduction