4 batteries - yes, OK - 6 batteries OK ??

Re: 4 batteries - yes, OK - 6 batteries OK ??

You should be able to go with upwards of 20-25% rate of charge--However, I would recommend that you get the remote battery temperature sensor option for your charge controller (if it has one available). One of the issues with high charge rates (other than the cost of the "extra" solar panels and that batteries are recharged by noon or sooner--so "wasted energy" unless you have a lot of day time loads) is that batteries can get hot with >~13% rate of charge--And hot batteries require lower charging voltages.

A charge controller can get confused (sees lower charging voltages and "thinks" the batteries need more charging current)--Batteries get hotter and voltage falls even more--And you get thermal run-away.

The problem with mixing battery ages is that the newer batteries can end up carrying more of the loads and aging quicker while the old batteries do less of the work. Also, you get problem of having to monitor/debugging your battery bank and having to replace part of it a few years down the road (and the possibility of a failing cell/battery causing damage to other good batteries if the failure is not caught quickly).

Mixed banks can work--It is just more work to keep everything working well. Sort of like replacing one bad tire at a time on a car... It will work, but not a lot of fun to keep on top of the problems and the "risk" of a flat/failure due to the oldest tire.

If you have a working bank and even an "over sized" array--Why not try the system as is. You will get experience and when the battery bank needs to be eventually replaced, you can size the battery bank to your, now known, needs.

If this is going to be a new install--Look at getting some "less expensive" batteries for your first bank or two. Between learning about your new off grid needs, most people end up killing there first bank well before its time. Poor maintenance, somebody leaves a load on when going on a trip. Kids/friends come by for a visit and leave all the lights/TVs/hair driers running. A water pump switch fails and leaves the pump running for a couple days before anyone notices... Etc.

My personal recommendation is to try for one string of batteries (i.e., larger AH capacity cells, drop from 12 volt to 6 volt to 4 volt to 2 volt "batteries", etc.) and 2-3 strings maximum (some people like two parallel strings--run on one string if a battery fails). There are just more cells to monitor specific gravity, more connections to make/keep clean, more debugging/monitoring to ensure that everything is working well--Each parallel string should have its own fuse/breaker to protect against short circuits, etc....

Batteries just do not "share current" well. Proper Wiring helps, and today you can get pretty cheap DC Current Clamp Meters which makes it very easy/safe to check that each string is taking its "fair share" of charging/loading current.

There are certainly people with parallel battery banks (and more than 3 parallel strings) that are very happy with their installation and battery life--It is just something I would suggest you reduce to 2 or 1 string if possible. Most people really do not like the extra maintenance/work involved to keep everything working well (in some areas where you cannot get larger AH cells, there is no real choice--and they have to build a bank out of whatever they can get--have to make do).

-Bill

Re: 4 batteries - yes, OK - 6 batteries OK ??

Fluke is going to be a very nice current clamp meter. Here is the 325 Fluke AC/DC DMM with True RMS reading. (otherwise similar functions to Sears unit).

http://www.fluke.com/fluke/usen/Clamp-Meters/Fluke-325-True-rms-Clamp-Meter.htm?PID=74609

$185 from Amazon.

The only problem I had with the Sears unit is the thermal couple probe failed almost immediately (do not use, so never bothered to get it replaced).

There is a similar Radio Shack DC Current Clamp Meter, and at least one person here had problems with the DC current readings (as I recall).

-Bill