R/C Battery - Why and How

My decision to go with R/C battery was made for the following reasons.
1.  I don't like to clean track.
2.  If this RR reaches its goal, it will have a main line approaching 400-500 feet.  Trying to maintain electrical continuity and dealing with voltage drop are two things I want to avoid.
3.  I enjoy taking engines apart, making modifications and putting them back together.  My knowledge of electricity is well above average amongst garden railroaders.  So doing a battery conversion is not a frightening concept.
4.  It is as close to prototypical operation as you get with sparkers.  Having built some, I hate block control systems.  I don't enjoy the construction or the operational side.
5.  I like the idea of being able to walk around with my trains, controlling them with radio control.

The Off-Grid Decision

Elsewhere in this child blog is a discussion of my decision to power my railroad off-grid with PV solar power.  I won't get into why here.  That issue is covered adequatly in other posts.  The decision to power with solar, like the decision to power with batteries is made.

You might want to review the post in this child blog describing the components of a sophisticated off-grid PV system.  It describes each component and provides a diagram of how they are wired together.  The system described could power a house, cabin, or workshop.  My needs are nowhere near as great.  At this point here are the components I envision in my off-grid PV system.
1.  A PV solar array providing sufficient power to serve multiple NPC GRR needs including charging batteries, powering th epond pump, provifing power to the drip irrigation control system and other putposes to be determined..  I will choose panels at a size and quality level that I will be able to upgrade capacity later if needed.
2.  A PV panel DC disconnect that will allow the solar panels from the rest of the system for maintenance and to provide overload protection for unanticipated events like a lightening strike.
3.  A Battery Charge Controller that will monitor battery charge levels and cut off charge when fully charged, and cut off battery power when batteries reach their discharge limit.
4.  A Battery Bank where the charge from the solar panels is stored until needed.  I am likely to run a 12 volt system as many of the devices I intend to power require 12 volt input.  This will eliminate the need for step up or step down transformers.
5.  A Main DC Disconnect allowing the power delivery side of the system to be disconnected from the power using side for maintenance and in the event of overload.  I anticipate this main DC disconnect will have smaller DC circuit breakers that control the load to the various users of the power.  This will allow me to run wiring consistent with the load, provide overload protection, and allow these syatems to be disconnected for maintenance.

That's it.  Here are the components in the sophisticated off-grid PV system discussed elsewhere I don't anticipate using.
1.  Generator - I hope to design this system with suffieiecnt capacity that I won't need supplementary power.  If my needs outgrow capacity I'll add PV panels and batteries to upgrade the system.
2.  Inverter - I'm going to try very hard to avoid using 120V AC on the system.  Just about everything I'm planning to do can be powered with 12 volt DCS.
3.  AC System Disconnect and AC Distribution Panel - Not needed for the same reasons listed above.

Should I absolutely need AC power, I have a 1000 watt AC inverter that could be provided power using a DC circuit breaker from the main DC Disconnect panel.  It has recepticles for two 120V AC plugs.

Number of Engines to be Powered

Given the size of my track layout I have a hard time imagining running more than three engines at one time.  I have a hard time imagining an operating session of more than 4-5 hours.  And it is unlikely I will be running trains more than twice a week.  So the weekly charge capacity required by the battery charging circuit of the solar PV system needs to be adequate to charge batteries providing a maximum of 3x5x2 or 30 hours of run time per week.  That times the average current draw of the engines should allow me to calculate the amp hour capacity needed for the batteries and the watt production capacity needed by the solar panels.  I'll update this area of the post once that calculation is complete.

While adding track in years subsequent to 2008 would increase the number of engines that might be run on the system, under normal circumstances the number of operators will not increase beyond three.  Should an event be held, it is possible some will bring their own battery powered locos and fully charged batteries.  On the other hand, ther may be events requiring additional battery powered engines.  Events like that are likely to be infrequent.  Under those circumstances, I'll need to decide whether to build excess capacity into the system or use grid power  to del with charge requirement overloads.

As for the number of engines the number needed to be converted to battery power - a lot.  I'm an accumulator of engines.  In my office alone is an Aristo Pacific, a Bachmann Spectrum 2-6-0, a Bachmann 2-6-0 Industrial, an Aristo 2-8-0, a Bachmann Spectrum Climax, and an Aristo Diesel Powered Combine, and a LGB 0-4-0 switcher.  The number of engines at home significantly exceeds those at work.