Charging schemes

[Mad_Labs]

Hi All,

Well, I have a good start on my charge controller/data logger. I can track my solar amps, generator amps, battery voltage and temperture. I have PWM control of the alternator on my lawnmower/alternator rig, and while I don't have auto start, I do have auto shutdown. Soon I will be able to track my load amps as well, waiting on a current sensor. With another unit, a manufactured module that tracks net amps, I know the ~ amp hours taken from the battery bank. (When the current sensors arrive, I'll be doing this myself). So, I have just about any charging scheme at my disposal. Since I don't have anywhere near enough solar even on a good day, I run the lawnmower a fair bit, so I want to optimize my charging scheme. The solar panels are connected directly to the battery bank without a controller. I use all they can give me, and 18 amps isn't going to cook my batteries in any case, but I do want to get or make a MPPT for them.

The basic specs of the system are: 1200aH, 12V battery bank, 10 golf cart batteries in series/parallel. I have a Trace 2512 inverter, about 18 amps of solar and the lawnmower/alternator which is good for about 60 amps. The controller is based on a Propellor chip. I have a keypad and VFD display out in the power shed and a touchscreen in the house (trailer) that is wirelessly connected to the power controller.  Fun stuff, I can see what is going on, change charging parameters on the fly while the genny is charging and so on. Good clean fun, although I still have a lot of programming to clean up. Anyway...

As we all do, I want to hit the sweet spot of fuel usage and battery life. So, does this seem like a reasonable charging scheme? Please feel free to point out any errors in my thinking, this is my first off grid setup and I am learning. I usually charge at about 100aH out, sometimes drawing as much as 200aH before charging but never more. All voltages are TC'd.

I enter the desired number of amp hours needed to charge the batteries, + 20 - 30%. I let the genny pump out 60 amps and allow the voltage to ride as high as 15.5V before limiting the current. I keep an eye on battery temperature. When I have replaced 80% of the amp hours, lower the voltage to 14.4V and allow the current to ramp down to a preset limit (I'm thinking 15 amps) and shut down the genny. The pro's of this scheme is quick as possible charging. The con is more water usage in my batteries, but as long as I keep up on that shouldn't damage the batteries.

Once a month (or when a SG check of the cells indicates), equalize the batteries, running the voltage up to 15.5V, then ramping down the current down for a couple of hours, or until the current drops below x (any reccomendations for x?) or when all cells read the same.

So, how does that sound?

As far as temp. compensation goes, I see some varying figures out there. Is there a consensus here about V/degree?

Thanks all!

Jonathan

[mike90045]

That's a lot of batteries in parallel.

I'll let you look at my favorite link with a grand explanation about parallel connections (mili-volts/ohms count).
http://www.smartgauge.co.uk/batt_con.html
and some great info on their other tech pages.

Quick charging up to the 80% full, should not use much water at all, it's the last 10% where you get most of the gassing.