Charge Controllers and setting charging rates.

We will again use this scenario example of the 1/10th Amp Hour design and design a system that will operate for 10 hours at anticipated current draw before using a charger of any kind.



The importance of a 10 hour system is that the storage of electricity in the DC batteries will operate your needed electrical items for a minimum of 10 hours before a charge is required. It is far less expensive to charge the battery bank than it is to have an AC generator powering the home as the engine is running.



Using fuel to power the AC generator becomes very expensive in comparison to using the DC generator to charge up a battery bank. Using the below scenario will exhibit the best method to make an efficient use of your charge controller, battery charger, or solar charge potentials.



Scenario exampling the best method to recharge your storage system.



2 light bulbs @75 Watts each or 150 Watts, one refrigerator freezer using 850 Watts and both running for 10 hours using a total of 1000 Watts per hour = 10000 Watts or 10 kWh ( kilo watt hours).


Usage would then need the 20% added for safety buffer @1200 Watts AC electrical power. Storage would be 12kWh or using the 1/10th method you would use a 48 volt system which would be four 12 Vdc batteries wired in a series formation for potential @ 48 volts. Using the 100 Amp hour batteries and the 1/10th calculation method would calculate 48 Vdc and 10 Amps per hour or a potential of approximately 480 watts per hour potential storage battery bank output. Four additional 12 Vdc 100 Amp hour batteries would be required and hooked up parallel to the original 4 to produce 48 Vdc and deliver 960 watts per hour. That is slightly under the required amount so we add an additional 4 - 12 Vdc 100 Amp hour batteries making the total potential delivery of 1440 Watts per hour for 10 hours. This is a couple hundred watts extra potential but when hooking batteries in series to gain voltage potential and adding more batteries in parallel to gain storage in capacity they need balanced out. A total of 12 batteries that are 12 Vdc and deliver 100 Amp hours of direct current are required to properly operate the system at a minimum for 10 hours before re-charging is necessary.




Charge rate is calculated by temperature rise in the cells of the batteries. Although the preferred optimum method is 1/10 the Amp hour capacity or charging the system for 10 hours for every 10 hours it has been used at the calculated rate of 1/10th Amp hour capacity. When your charging the battery bank with a conventional gas powered generator that would mean operating the generator for 10 hours per night and charging becomes expensive compared to the quicker method of charging at a rate the cells do not exceed 115 degrees farenheight. A better newer type battery can take charges quicker and for shorter lengths of time making this heat method a less expensive way to charge batteries when using the gas powered generators.

For the battery bank as written in the minimum scenario 12 total batteries are used for a total of 1200 watts per hour current draw at the 1/10th Amp hour calculation optimum. The charge rate should be around (30 Amps per hour) or 30 X 48 = 1440 Watts. At that rate the battery cell are warm but what if you cranked the charge rate to double that to get a 100% full charge in 5 hours or less. At that rate you get the same electricity in half the time making your gas bill go down 50% for the generator and 50% less time from the noise.

A charge controller usually has one input cable, a generator usually has more than one plug in receptacle. The total capacity of the generator in watts is divided up between all the plugs so simply using one plug in receptacle limits the potential charge rate for the battery charging section. This causes you to use more fuel for less electricity delivered.



Remember the optimum @2.2 Vdc per cell and the minimum to produce useable 120 Vac to your house appliances. So the maximum optimum charge for the 48 Vdc system would be 52.8 Vdc after the surface charge is taken off. The system can take slightly more voltage when charging using the temperature controlled method (preferred) so maximum charge potential should be around 55 volts DC. The lower limit is when you monitor 115 Vac at your appliances as they are being used, normally there is a monitor volt meter in the house that tells you the AC voltage as it is being used. When going out to your battery bank you may read that the battery DC voltage going into the inverter is @ 42 Vdc or lower. The key is watch the AC voltage, lights will run ok (IR device) with less AC voltage they only get dimmer until they glow red. The induction devices like fans and refrigerator will burn out at a voltage that is to low and will probably run ok on 115 Vac but the temp gun should be used to find when the temperature in the motor starts to rise due to lack of proper AC voltage. Also it is harmful to appliances to exceed 121 Vac for supply voltage. Most all charge controllers have an upper and lower limit voltage warning system and will shut the system down when over or under the limits set.



In this scenario the charge controller can be manually set, for maximum DC voltage and minimum delivered AC into the house. Amps going into the batteries as DC (direct current) and the output in watts AC (alternating current) can be adjusted according to heat developed in each system. Using an inexpensive temp gun is a good way to find system efficiency in any form of physics as elements operate dynamically together. Heat is the one single way to destroy all electrical systems but can also be used to optimize your systems by monitoring the temperatures.  

Temperatures to monitor & setting charge rates.



There are two important phases of electrical energy, one phase is discharge and the other is charging the storage system (battery bank). Both are the same, the flowing of electrons either from the storage or into the storage.



The temperature of the batteries (storage) should never exceed 120 farenheight, that is the maximum upper limit of temperature the battery plates can withstand without going into a deterioration mode of absorbing the H2O (water) in the electrolyte solution. This deteriorates cell capacity and the ability to hold a charge, it drops voltage in the cell quickly. The acceptable temperature of the batteries should be between 100f and 110f but not going over 115f.



The wires from the charge controller to the battery bank also do not want to run at over 100f but that is acceptable up to 115f. When charging the storage system from the lower limit to the maximum optimum (12 volt battery to 13.2 Vdc) the charge controller output can be set so the battery temperature during charging never exceeds 115f. This is using the maximum charge method and should be used when attempting to save generator run time. The less you charge your battery in current the longer your generator has to operate to get the charge into the batteries.




Once your charge rate is set by the temperature controlled method then a calculation of watts is needed to add to the generator rating when the charge controller also provides AC voltage to run household appliances. Lets just say we are charging a 100 Amp hour 12 Vdc battery @ 50 Amps (charger voltage approximately 16 Vdc). The temperature never exceeds 115f so the watts delivered is 16 Vdc X 50 Amps or 800 Watts. If the home scenario is the 1440 watts for refrigerator and lights then the additional watts + 20% = 960 watts. The generator would be sized according to the closest to a 2.4K electrical current generator that is available. 2,400 watts / 746 would require a 3.21 horsepower engine. The important concept here is to purchase generators that are not larger in horsepower than a person needs to operate. More horsepower = more fuel burned per minute, each additional minute a person uses while charging batteries and operating household appliances is that much more fuel and noise in run time for the generator.



The lower limit for the batteries would be measured at the AC outlet in the household as all items calculated were operating. The AC 120 Vac will deviate down to 119 or 118 Vac but a lowest limit allowable would be the 20% under, so 120Vac - 24 Vac would be 96 Vac and heat would destroy motors and lights would go dim. I would not want my 120 Vac loads to drop below 108 Vac for safety purposes.

The volt meter AC needs to be set at a lowest minimum voltage by now checking the overall battery voltage in DC. Your system is a 48 volt DC system with an optimum of 52.8 Vdc full charge. Now after the AC meter is reading 110 Vac the overall battery voltage may be slightly under the 48 volt reading or possibly down to 46 Vdc. There is where you will want to set your lowest limit for battery bank voltage prior to charging.



Using a modern charge controller the upper limit voltage determines the current flowing into the battery. On the 48 volt system the batteries can achieve 52.8 Vdc at 100% full charge. The charge controller needs to be set at more voltage and to the point heat is evident in the battery cells, batteries like a warm environment over 60f, anything under that the battery has a normal discharge rate for the time it is under 60f.



The current flowing into the batteries develops heat, as the current increases so does the heat in the wiring from the generator as well as the temperature in each cell of the battery bank. Any cells not equal in temperature can be an indication of a damaged cell within the storage system. A damaged cell wastes energy and causes other cells to gain heat.



Setting your system up for long life and maximum efficiency requires balance; electrolyte specific gravity, charge rate versus temperature, time in charge, time in usage, generator run time and not using more power than needed in the charging system.




A free consultation regarding your system can be scheduled by contacting us on this link. CONTACT US



We also monitor dirty electricity, when someone has simply changed an electrical component and not realized the importance of polarity. This is very common but generates a high amount of electromagnetic disturbance (EMR).



CONTACT US or call 248-7379 - 248-8727 for a free consultation for your DC storage systems.