I'm looking in to creating a simple split charger for my leisure battery so that when the Van is running I can charge with both the 100watt solar panel and the altenator.
I have a 25V voltage sensor and a 200 amp relay
my question is can I connect the relay line to the main van battery or does it need to feed straight off the altenator?
I don't know a great deal about how electricity works just the basics so not sure if that's effectively the same thing or if there's a difference, I'm just a lowly programmer.
Any help would be greatly appreciated thanks I'll be using a nano for the project btw.
well the battery is under the drivers seat which is much closer to the leisure battery. I have seen lots of people use branded split chargers before surely it wouldn't make a difference as the charger stops charging as soon as the voltage reaches a certain point no?
So it doesn't matter if I connect it straight to the main battery instead of the altenator, would doing that not drain the main battery which I need to start the engine?
MorganS:
Usually it is better to only charge from one power source at a time. Alternator or solar, not both.
As to exactly where to hook in, that is usually a function of which end of the wire is easiest to reach.
Its easier/simpler, not necessarily "better" if you want that battery charged in a hurry!
Charging from multiple sources involves more hardware and more control logic and safeguards, as
there may be issues of overcharging and sharing the load between the power sources sensibly that
are avoided in a simpler setup.
MarkT:
Its easier/simpler, not necessarily "better" if you want that battery charged in a hurry!
Charging from multiple sources involves more hardware and more control logic and safeguards, as
there may be issues of overcharging and sharing the load between the power sources sensibly that
are avoided in a simpler setup.
Would a voltage sensor be sufficient that would break the relay connection at max voltage for leisure battery? The basic set up I was planning would just be voltage sensor on main battery to tell when altenator is working that creates the connection with relay then voltage sensor on leisure battery that will break the connection when max voltage is reacehed.
The solar panel charge controller will take care of itself obviously that is over simplified I'll have all the neccissary fuses etc.
There are a lot of commercial modules available to do exactly that. Even though you already have the 200A relay it is going to be cheaper to buy a module. Especially if you are not confident at electronics.
MorganS:
There are a lot of commercial modules available to do exactly that. Even though you already have the 200A relay it is going to be cheaper to buy a module. Especially if you are not confident at electronics.
I like dong things myself and learn along the way and those kits are at least £30 I can do it much cheaper. Thanks for your help though I'll draw up a schematic once I get it all planned out maybe you could tell me if you see any problems with it.
Obviously I'm no expect but I think it's quite a simple project and there are other features I plan on adding to the device that aren't included with those kits.
moderategamer:
I'm looking in to creating a simple split charger for my leisure battery so that when the Van is running I can charge with both the 100watt solar panel and the altenator.
You have not told us what size is the battery. Big batteries can take more current than smaller batteries.
I have 2 x 80W solar panels connected directly (without a regulator - long story) to a 200Ah deep cycle lead acid battery (the type you top up) and in my experience when the alternator is running it dictates the voltage - by comparison the solar panel current is puny. However I rarely have the alternator running around midday when the solar power is at max.
I reckon a relay to cut-off the solar panel if the battery voltage is too high would be the simplest solution.
Robin2:
You have not told us what size is the battery. Big batteries can take more current than smaller batteries.
I have 2 x 80W solar panels connected directly (without a regulator - long story) to a 200Ah deep cycle lead acid battery (the type you top up) and in my experience when the alternator is running it dictates the voltage - by comparison the solar panel current is puny. However I rarely have the alternator running around midday when the solar power is at max.
I reckon a relay to cut-off the solar panel if the battery voltage is too high would be the simplest solution.
...R
Interesting I think most alternators put out around 14 V but the sensor on the altenator side is just to close the relay for charging are you saying it will affect the voltage across the battery? never thought about that.
Robin2:
Closer to 15v I suspect.
I don't understand what you mean by that.
...R
I mean it's just to sense that there's power coming from the altenator so that it can charge without draining the battery when the ignition is off. I'm not sure if the altenator sets the voltage of the battery though because if it does I can't protect from overcharging which is a bummer.
When you put 14V at the battery terminals current will flow into the battery. It doesn't matter how the 14V got there. You can measure it with a voltmeter or an appropriate Arduino circuit.
If the battery is in a low state of charge then it will take a lot of current at 14V. To hold it up at 14V requires a lot of power to keep that high current going. If you don't have that power available then your source must either blow its fuse or reduce the voltage. Fortunately wires have positive resistance so just the wiring keeps the system stable with no dangerous runaway.
@moderategamer, I am still not clear what you had in mind when writing Reply #10 - there seems to be something you think needs to be avoided but you have not said what it is - something that you could do if there was more distance between the connections? I have the sense that you are trying to say something like "if the placing of the parts was different I could do X"
Posting a diagram of the circuit might help. See this Simple Image Guide
As @MorganS has said, just measure the voltage at the battery terminals.
In an electrical cable without a resistor the voltage will be the same everywhere.
MorganS:
When you put 14V at the battery terminals current will flow into the battery. It doesn't matter how the 14V got there. You can measure it with a voltmeter or an appropriate Arduino circuit.
If the battery is in a low state of charge then it will take a lot of current at 14V. To hold it up at 14V requires a lot of power to keep that high current going. If you don't have that power available then your source must either blow its fuse or reduce the voltage. Fortunately wires have positive resistance so just the wiring keeps the system stable with no dangerous runaway.
Thanks very helpful so do car batteries need protection from overcharging? How does the van avoid overcharging by default if there's nothing between the altenator and the battery?
Robin2: @moderategamer, I am still not clear what you had in mind when writing Reply #10 - there seems to be something you think needs to be avoided but you have not said what it is - something that you could do if there was more distance between the connections? I have the sense that you are trying to say something like "if the placing of the parts was different I could do X"
Posting a diagram of the circuit might help. See this Simple Image Guide
As @MorganS has said, just measure the voltage at the battery terminals.
In an electrical cable without a resistor the voltage will be the same everywhere.
...R
I just want to charge the leisure battery while the altenator it running and to not charge when it isn't the fuses were just there to protect the battery in the chance of over current. I was wondering if the altenator is charging the battery how could I measure the battery level if it's being pulled up by the altenator to avoid overcharging.
moderategamer:
Thanks very helpful so do car batteries need protection from overcharging? How does the van avoid overcharging by default if there's nothing between the altenator and the battery?
All automotive alternators have a built-in voltage regulator. I have been assuming you knew that.
Robin2:
All automotive alternators have a built-in voltage regulator. I have been assuming you knew that.
...R
Yes but I thought you were saying that when the altenator is running it pulls the batteries Voltage up to 14V which would be over the rated 12.6 or whatever it is for fully charged. So my question is how does the regulator know when to stop charging?
As soon as you take it off the charger and use the battery, current is flowing the other way and the unavoidable resistance makes the voltage on the terminals lower.
moderategamer:
So my question is how does the regulator know when to stop charging?
It doesn't. It just keeps putting out the regulated voltage. In a car or truck in normal use there will be lots of other things drawing power from the alternator.
If you want more sophisticated battery charging control then you need to get a 3- or 4-step battery charger. It will reduce the charge voltage to about 13v after some period of time so that the battery is never overcharged.
Robin2:
It doesn't. It just keeps putting out the regulated voltage. In a car or truck in normal use there will be lots of other things drawing power from the alternator.
If you want more sophisticated battery charging control then you need to get a 3- or 4-step battery charger. It will reduce the charge voltage to about 13v after some period of time so that the battery is never overcharged.