Where to wire my new solar charging system into my 4x4?

[nickc]

Hi

I have a 4x4 with a duel battery system whereby the 2nd 12V battery is currently trickle charged via a regulator when the engine is running - this system came with the car when I bought it.

I have just purchased a 80W solar panel and controller that I want to add to the 2nd battery charging system (I intend to mount the panel on the roof)and have a few queries as follows re: how the tickle charge and solar charging systems will work together (or not):

- Can I use the same input/connection into the battery;
- and if so where do I link in the cables from the solar charger i.e. between the battery and the existing regulator (and is this simply just splicing the cable together)?
- how do the two systems work togther and switch between themselves i.e. is it automatic? I assume when the engine is not running only the solar system will be working, but when the engine is running will both work in tandem or does the trickle charge system overide the solar?

Many thanks in advance,

Nick

[Mike90250]

Fro simplicity, I would connect the panel and charger to the terminals on the 2nd battery (or the battery you want to charge. )

For safety, I'd install a 5A fuse within a couple inches of the battery terminal, on the + lead.

Depending on your charger and loads, and heat at the battery, you may want to check the water in the battery every couple of months.

[nickc]

Thanks for your reply.

The battery is in a power pack/box with 12V lighter sockets for inputs and outputs so is not that accessible hence my query as to whether I could link into the input socket from the existing regulator?

Also it is a deep cycle gel battery so am I right in thinking I don't need to worry about water topping up?

[Mike90250]

I don't like using lighter jacks as critical power connectors. And , if you are using a GEL (is it GEL or AGM - they are different) or AGM, preventing overcharge is critical, as you can vent H & O2, which translates into capacity lost forever. You need a Charge controller that works with a Battery Temperature Sensor.
This page http://store.solar-electric.com/chco.html has 2 articles in it, about charge controllers, please read it. Even a 80W panel, can destroy an AGM/GEL battery, because the batteries have low self discharge, and once fully charged, begin to vent gas.
A cig lighter connector is not robust enough, I would suggest getting into the battery box, and hard wire cables with "Anderson Connectors" to it.
link: http://store.solar-electric.com/ansb50amphoo.html And don't forget to protect the wireing with a fuse sized for your loads and wires.

[nickc]

Thanks for the invaluable advice.

I am not sure what type of controller (other than it is 12A/12-24V) I am getting with the panel as I have not received either of them yet (they are in the post).

I have had a look at the first link you suggested but was unable to find the articles that referred to temp sensors and gel batteries?

I have looked at my battry pack again and can confirm it is called a 'Calibre 40AH Deep Cycle Gel Battery Pac'.

I have also looked inside the box to find a jumble of wires and some instructions on the back panel. Regarding charging the instructions say the following (it can be charged either via 240V mains or 12V):

2240V - Battery Pac is fitted with a 10 Amp two stage battery charger with boost and float modes of operation. Simply connect the supplied cable to the 240 volt input plug to charge.

12V - The battery Pac can be recharged via the 12 volt input plug from either solar panels, vehicles or other DC voltage sources. Note Battery Pac input is limited to 15 volts max. Solar panels must be regulated below 15 volts with maximum of 8 amps output. Once the battery voltage reaches 15 volts charging will cease until the battery voltage falls below 13.5 volts."

From the above description it sounds like it is designed to be charged from solar panels (with a controller) and has an in-built overcharge protector if I use the supplied 12V input socket (though I note you don't recommend this type of connection)?

On this basis do I need the protection you describe?

[Mike90250]

Well, you've got something that is not standard.

Sorry about the links, I thought the chargers talked about the different charge requirement for different batteries. here's the scoop on gell:

http://www.windsun.com/Batteries/Battery_FAQ.htm#Gelled%20electrolyte

thermal effect - requirement for Battery Temperature Sensor

http://www.windsun.com/Batteries/Battery_FAQ.htm#Temperature%20Effects%20on%20Batteries

Battery charging voltage also changes with temperature. It will vary from about 2.74 volts per cell (16.4 volts) at -40 C to 2.3 volts per cell (13.8 volts) at 50 C. This is why you should have temperature compensation on your charger or charge control if your batteries are outside and/or subject to wide temperature variations. Some charge controls have temperature compensation built in (such as Morningstar) - this works fine if the controller is subject to the same temperatures as the batteries. However, if your batteries are outside, and the controller is inside, it does not work that well.


So, anyway, I cannot be sure what you have, and so you will have to make the best guess as to what to do. you might try searching for "Calibre 40AH Deep Cycle Gel Battery Pac" see if you can find the mfg or some ad for it, and figure out what you have.