We connect right to the batteries when installing AM Solar charging systems by running a dedicated charge line directly from the controller. Usually, 8 or 6 AWG, fused or with a 40 DC amp circuit breaker. With only a 20 amp panel, you don't need a heavy gauge like we use. Probably, 12 AWG will work well. It depends on the maximum amperage that the controller will output to the batteries.
A 20 watt panel will only give you a 'trickle' charge of about 1.6 amps peak or so. Fine to maintain batteries that are already charged, but will take a very long time to charge batteries that are depleted.
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lewster
Solar Tech Energy Systems, Inc.
Victron Solar Components and Inverters, Zamp Solar Panels, LiFeBlue and Battle Born Lithium Batteries, Lifeline AGM Batteries
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