Panel size to charge 420 AH FLA battery without any CC?

[maple flats]

I have a sawmill that uses a 12 V 420 AH battery to start the motor. The mill frequently sets idle for long periods of time but I prefer not having to remove the battery and put it on a trickle charger to keep it charged. Someplace I've read that a solar panel can be connected directly to a battery without a charge controller. How does one calculate what panel to use? I would make a mount on the sunny side of the sawmill carriage and leave it there all the time. Please advise. The sunny side faces about 170 degrees south. Would I be better off using a CC? If yes, in a case like this will a PWM be a good choice, or should I still go MPPT?
If going without a CC should I size it for 1 small panel in summer, til mid fall, then 2 small panels til mid spring in parallel?
I am located on the 43th parallel in New York State.

[littleharbor]

An inexpensive PWM charge controller would be recommended. It would give you a full bulk charge when needed, and absorb and float voltage while your battery sits idle. Even a small solar panel will put out full voltage (possibly up to 18 volts) and not limit voltage when your battery is full and only needs a float voltage around 12.8-13.6.

[Wy_White_Wolf]

All you need is a little battery maintainer panel in the 1.5 to 5w range to overcome the self discharge of the battery. They usually come with cigarette plugs so just wire up one to the battery and plug it in.No need for a larger panel or charge controller.


As far as your battery I Think you're mixing up CCA and AH. I've never seen a 420AH 12V battery but lots of smaller engines do have 420 CCA batteries.

WWW

[Sunking]

Hey Flats, long time no hear. Hope all is well.

Ditto to both comments.

All you need is a 10 watt, 12 volt battery panel. All that means is the panel Voltage at max Power is around 16 to 18 volts. If just using a panel you will need to buy a diode to prevent the battery from back feeding the panel at night and thus discharging the battery.

But a cheap PWM controller no more than $15 is money well spent on top of a slightly larger panel like 20 watts. Even better any spare panel you have say 100 watts and a cheap 6 amp PWM controller.

[Mike90250]

There are many brands of 3-10w dashboard PV panels that plug into the lighter socket to keep a car battery charged up. Many have a blocking diode on the cigar plug on the cord, so if you cut the plug off, you loose the diode.