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Charging batteries


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Hi all,

I'm wanting to charge batteries. The basic thing is I have a bus I'm converting to a motorhome. I want to charge 4 D cells from a smallish solar panel. While there are commercial chargers available, they don't perform as required. I need more than just small cells and a diode in an expensive plastic box.

What I want to do is to control the charge in each cell to prevent overheating. I also want to have the panel on the roof with the batteries charging inside the vehicle.

My problem is nobody seems to cater to this level of sophistication. I'm OK with buying panels from china via eBay and charge controllers. Just not sure what I really need.

Any ideas?

Sent from my Nexus 7

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  1. Are you going to integrate the buses charging system (alternator) with the solar charging system, if so you must determine the voltage the bus is running on (12V/24V)

If you are going to integrate the charging systems there is 2 ways. The one is to have a blocking diode so that your charge current from the bus does not flow towards your charge controller and solar panel. The other way is to wire a relay into the buses accessories system on the ignition side, this will make the solar system go open circuit once the bus starts and in this way the buses alternator will charge the batteries while the bus is running.

Solar panels and vehicles can be tricky the biggest panels i would suggest you use is 90W panels (2 or 4 of them). You will also have to redo all the silicone between the frame and the glass, meaning put a second layer of silicone on to attached the frames better to the glass. You really need to do this as they do come loose.

As you will not always park in direct sunlight (when on a camp site) you can make the panels removable with a a long cable so that you can park in the shade and put the panels in the  sun, so take care when you built the frame to attached your panels too.

If you go bigger then 90W panels you will have to have custom made panels as the frames would have to be different. 

Please take note that most charge controllers cannot be combined with your vehicle charging system,

You can also google for local mobile solar power companies i am sure they would be able to assist you.

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Be especially careful when working with cheap PWM controllers. Very often they switch in the negative line, with a common positive. Even the better charge controllers often have their current sensing in the negative line. Since the vehicle is negative-ground (usually), it's easy to make a costly mistake :-)

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