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Solar trickle charger for car battery


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Good morning all

I have a bakkie I only use once a month and almost every time the battery is either flat or just about.

I want to build (or buy) a small solar trickle charge that will keep the battery floating, any ideas?

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Just buy a small panel and connect it. Car alternators have no fancy charging electronics, they just supply the current the battery requires. I have a a 15W panel I use to keep my tractor battery topped up, but I'm sure a 50W or 100W panel would be fine without a charge controller.

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2 hours ago, DeepBass9 said:

Just buy a small panel and connect it. Car alternators have no fancy charging electronics, they just supply the current the battery requires. I have a a 15W panel I use to keep my tractor battery topped up, but I'm sure a 50W or 100W panel would be fine without a charge controller.

So I just couple + to + and - to -?

Does the panel not short out (or drain when the sun is down) the battery?

Found this on BOB https://www.bidorbuy.co.za/item/359107081/12V_4_5W_Portable_Solar_Panel_Power_Car_Boat_Battery_Charger_Backup_Outdoor.html

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3 hours ago, DeepBass9 said:

I have a a 15W panel I use to keep my tractor battery topped up, but I'm sure a 50W or 100W panel would be fine without a charge controller.

I would keep to the 10W/15W range, any more than that would almost definitely cook your battery if you are not using a charge controller.

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9 hours ago, DeepBass9 said:

Just buy a small panel and connect it. Car alternators have no fancy charging electronics, they just supply the current the battery requires. I have a a 15W panel I use to keep my tractor battery topped up, but I'm sure a 50W or 100W panel would be fine without a charge controller.

Actually  a car's alternator is limited to about 14.5V

 

@Anthony I use a small DC-DC buck converter, limited to 14.2V to keep some car batteries charged from a 20W solar panel. it's not as efficient as a MPPT, or probably a PWM charger (10A would cost about R300) but it does it's job

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