Electrical – Solar charge controller wiring

Based on my experience being qualified as a battery charging electrician on submarines and installing/upgrading/maintaining the 12v electrical system in my motorhome.

1. Battery electrolyte specific gravity is not model or battery specific so your chart is fine.

2. Amp-hours is a measurement of current consumed (or the sheer number of electrons you've pulled out of the battery) rather than tracking watts which is a measure of power. You can easily track the amount of power used, but it would be impossible to determine the actual state of charge in your battery. It would be like if you tried to gauge how much fuel you had left in your car by reading a "cumulative horsepower meter".

3. A manual hydrometer is fine - just avoid the super cheap ones available at the auto parts store.

4. Get a real battery charge monitor that measures amp-hours in/out. I use one made by Xantrex.

5. You have to test the battery to know its bad.

6. An equalizing charge involves holding charge current at a low value, which boosts charge voltage - so if your charge controller won't allow you to set EQ current at a value, get a new one. 10 amps is probably close enough to the charge rate appropriate for equalizing - however if your array is only capable of delivering 10 amps with full sun, you might want to reconsider that strategy.

7. Who cares. Battery capacity is a function of the rate of discharge so that value is effectively worthless to you as a monitoring metric.

I was headed this way until about 2009. In the most modern and expensive setups you might have all the devices communicating and coordinating. In most, each one has its charging parameters that it's trying to meet, and the only communication is the voltage on the bank.

With multiple, uncoordinated charge controllers you may exceed the optimum charging current, and you should expect to have disagreements among uncoordinated charge controllers (and a water turbine with no charge controller) as their charging set-points and algorithms are almost certainly different.

If you have the money to put into it, or you see it as saving money on the battery bank's lifetime, a set of networked, coordinated smart charge controllers would certainly work more optimally (and can all work at the same time) - but you should also realize that any system that won't leave you in the dark for large parts of the year is going to have some excess capacity when everything is going well, charging-wise.

You can't simply add more battery without making it really hard to get it fully charged and equalized, and you can't reduce power sources without finding yourself in the dark after a few dry, cloudy, windless days. So sometimes, you are going to be dumping excess power. If you can do something useful with that power, great; (laundry is a good one, often) otherwise it's just part of the cost of having power more of the time. In the case of a fuel burning generator and a wind turbine, common sense would be to shut down the fuel-burner on a windy day.