damagesolar cellvoltage
I have a small 12v system for my cottage with a solar panel, charge regulator and a battery. Mostly used to charge phones and to drive a few lights.
Now I'm planning to connect a inductive load (12v water pump) to this system and I'm worried that this motor can cause voltage spikes that can damage other electronics connected.
How should I connect this motor to be sure it doesn't damage other stuff connected to the system?
The car charger is most likely a small switched mode power supply.
This should be fine running from any voltage (assuming a 5v output) of say 7v up to 50v+ (check the chip to be sure of the upper limit).
I am currently working with the MAX5035 family of chips which run from 7.5VDC (or 15VDC for the 12V version) up to 74VDC to give 3.3V, 5V or 12V.
I wouldn't recommend connecting the panels in series in case the 20V panel pumps too much current through the ones that don't work very well. To decide how to connect them (if it's possible) details of those panels would be required.
However, for the 20V panel I would say you need a switch mode buck regulator that takes the 20V and reduces it efficiently to 12V to power the two 12V motors. At 0.8A total draw from the two 12V motors the power requirement is 9.6W. The panel and regulator should be able to supply 90% of 20V x 0.8A = 14.4W.
This leaves about 4W (conservatively) for the 6V motor which you imply requires 0.6W. You'll need a second step down buck regulator for this device and it sounds feasible.
Switch mode buck regulators - there are tons of them but I can only recommend a design type such as the LT3976: -
For a slightly more efficient regulator there is the LTC3780 which will work providing 12V down below 12V from the panel: -
Both regulators can supply 12V at 5A.
I wouldn't bother thinking about a linear regulator because it will waste about 8W in heat.
It's possible that you can search along these lines and get some kind of module/PCB that you don't have to build. Maybe someone can recommend something?
Best Answer
You don't state what type of battery you are using but based on the size I'll guess that they are flooded lead-acid or similar.
Connecting a 10A pump directly (fused, of course) to the 240Ah battery bank should cause no problem. Typical lead-acid batteries like yours can supply 10x that amount for short periods (for this reason, be careful about shorts...)
Your diagram shows the DC loads coming off of the charging regulator, but it is not necessary to do it that way. Note that the charger output as shown may provide low-voltage cutoff and similar features to protect the battery.
Except for the solar input, millions of RVs have very similar setups with a lead-acid battery driving a variety of 12V DC appliances including water pumps. The water pump cycling is not a concern there, even with chargers and lights.
Most 12V DC items are made to handle noise and a wide range of actual DC voltage inputs. 11 to 15V should be considered a normal range for the "12V" supply.
If you experience problems with interference and want to specifically reduce motor-induced voltage spikes onto your 12V system, use a heavy-gauge wire and connect the water pump direct to the battery; don't share the wire with other devices that may be sensitive.
Alternately, consider running a separate 12V wire for any devices that show sensitivity or placing a large capacitor across the 12V input of any device that experiences problems (a technique used in high-power car audio systems.)
Heavy gauge wire and short runs provide the best results.
N.B. & disclaimer: I say directly-connected to the battery but every connection to the battery positive terminal must include a fuse located at the battery terminal sized appropriately for the wire gauge.