Solar Panel battery chargers

[LAKERtoo]

.. Canadian Tire has a 40W Crystalline solar panel with fold out stand and 7A charge controller on sale .. my 2005 R21 has 2 batteries wired such that ONE/BOTH/OFF is wired to the power switch .. use of the boat would be 3-4 times a week for 2-4 hours .. there is a 110/120 recharging system in place with converter/controller but the boat will not have AC/DC handy ..
so my questions are:

1) is the 7A controller adequate to protect from over-charging ? .. I've read that even low watts panels can lead to battery damage
2) what terminal connections can I make that will ensure that both batteries will top up ? ..
3) can the 12 volt dash pug-in be used to charge ?
4) would my running time be enough to keep batteries charged without the panel ?

Thanks for any comments .. Rob

 

[SGIDAVE]

.. Canadian Tire has a 40W Crystalline solar panel with fold out stand and 7A charge controller on sale .. my 2005 R21 has 2 batteries wired such that ONE/BOTH/OFF is wired to the power switch .. use of the boat would be 3-4 times a week for 2-4 hours .. there is a 110/120 recharging system in place with converter/controller but the boat will not have AC/DC handy ..
so my questions are:

1) is the 7A controller adequate to protect from over-charging ? .. I've read that even low watts panels can lead to battery damage
2) what terminal connections can I make that will ensure that both batteries will top up ? ..
3) can the 12 volt dash pug-in be used to charge ?
4) would my running time be enough to keep batteries charged without the panel ?

Thanks for any comments .. Rob

Hello Rob,

1. Perhaps. Solar charge controllers come in at least two varieties...MPPT vs PWM. From what I've seen the PWM are cheaper while the MPPT can provide more amps to your batteries in some cases. The 7 amp rating is relative to how many amps the panel outputs...a 40 watt panel will be well under the 7 amps so you should be fine.

2. If the charge controller has a way of splitting the output then you can connect both of your batteries. Otherwise, plan to connect it to your starting battery only.

3. If you use the 12v dash plug the house battery will get all the charge...or whichever (A or B) is connected. Heck, I guess you could leave your A/B/Both/Off switch on 'Both' then the 12v dash plug would charge both. But there is significant hazard in that your boat electrical system is ON while you are away. That's generally a bad idea. Sensors fail, pumps (like bilge pumps) come on and run until the batteries are dead or a fire occurs, etc. I believe it's best to turn the boat completely OFF while away. You've read the threads about the thruster coming on for no reason, right? Turn all that stuff off!

4. If you use your boat ONCE a week for 4 hours your batteries should be fine charge-wise. Unless you've got a bad battery. So 3-4X/wk usage really negates any benefit of solar charging in your case. That's assuming the boat is electrically 'off' while you are away and the fridge, lights, stereo memory, etc are all OFF.

davee

 

[LAKERtoo]

Thx Dave .. my 2005 21 Classic is bare bones regarding electrical extras ... basically bilge pump, legal lighting requirements, search light, horn .. so I'll forego the panel for now ...