Solar discussion continued..

cannesdo wrote:
How do you know when you're at 50%? I do have green, orange and red lights on the control panel. Nothing below orange?

I use the CHART METHOD here...


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This of course is not absolute but gives you a close assumption that you are getting close to the 50% State Of Charge point with your batteries..

I monitor this on my BATTERY MONITOR PANEL that looks like this pictorial. The OEM % panel meters are pretty much worthless for me

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I have my Battery Monitor panel mounted in a good spot to be able to observe it when being used... I can watch BANK 1 - Bank2 or both together as well as total DC Current being drawn from the loads or how many DC Amps are being demanded by the batteries when being charged. Only thing I wish I have added was a settable AUDIO ALARM when the batteries get below a threshold like 12.0VDC etc...

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When my battery voltage drops to around the 12.0VDC range than I want to start my re-charging routines to get it back up to its 90% charge state as soon as possible. Going below the 50% charge state will start doing harm to your batteries...

My battery use was all planned out for camping off grid running the things I wanted to run... My biggest drain of course is between 6PM and 11Pm each evening and of course always have the parasitic drains to deal with. Camping at various place sometimes does not allow one to run the generator to get the batteries charged back up and this is where having solar panels will be the best PLAN B thing to have. Of course solar panels don't work except in high sun so in my case I would always have the generator around.

I am just now starting to consider installing solar panels for my setup and have been doing the generator three hour run every morning since starting to use my off-road camper and bigger batter banks in 2009. I only think of the solar panel to be battery chargers...

My new battery bank just now being planed will be two groups or two 6VDC batteries in series which will give me around 440AHs capacity replacing my current battery bank shown in this photo... This was originally two groups of two 12VDC GP24 Interstate Batteries in parallel but one died from being over-charged using a single mode converter/charger unit. I now use a PD9260C 60AMP DC Converter/charger unit

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Roy Ken

cannesdo wrote:
I was thinking that with 200 Ah 6v batteries you'd have 400v so the total Ah of 4 6v golf batteries won't be much higher than 4 12v deep cell batteries. So what's the advantage? They last longer? This gives me only 200v to play with. How do you know when you're at 50%? I do have green, orange and red lights on the control panel. Nothing below orange?

No idea what you mean by "400v" and "200v" :h but regardless a single GC-2 flooded 6 volt battery such as the Trojan T-105 is 20-HR rated @ 225 AH so obviously four connected in series parallel would offer 450 AH, half of which is usable @ 50% DOD (Depth of Discharge) which is about as far as you'd want to draw them down on any regular basis. Compare that to the Trojan SCS200 12 volt flooded 12 volt deep cycle battery which is 20-HR rated @ 115 AH - obviously four of those connected in parallel would offer 460 AH, half of which is usable @ 50% DOD.

While GC-2s like the T-105 are perennial favourites with the dry camping crowd some do prefer 12 volt versions because they may fit available space better and because if one goes bad the others can still remain in service. 12 volt jugs also generally have less internal resistance so for those of us running an inverter that can mean less voltage drop under heavy inverter load, which in turn means the inverter is less likely to low voltage alarm compared to powering it with a 6 volt battery with higher internal resistance.

Next is the issue of whether you want flooded or might benefit from the advantages more expensive AGMs can offer, not the least of which includes easier installation as they don't have to be mounted sitting up, generally can be safely drawn down to a lower DOD than flooded, and will usually accept a recharge more quickly. These of course are generalizations so the key is to make sure you compare apples to apples when designing your battery system which consists not just of batteries but also an appropriate charger for properly maintaining those batteries.

Idiot meters with coloured bands to indicate state of charge are just about useless - at the very least get yourself a reasonably accurate DVM but those seriously interested in solar and wanting to accurately track how much power they're using and how much their system can restore are much better served by investing in a Bogart Engineering Trimetric.

compare the light blue (12v marine RV) line to the red line (6v GC deep cycle). For properly charged batteries. either can be ruined quickly from abuse. although the 6v can handle more abuse.



Volt meter, digital multi meter, 50% state of charge @ ~ 12.2v under little load. colored lights are a guess.