Another Solar Charger setup question

[The Canuck]

Like others, I have been intrigued about a solar kit that will allow our boat batteries to be topped off while we are not at the lake. I have seen some flexible panel kits posted here on the forum, as well as some that have a more permanent solution, but they are typically attached on the boat. As the season is getting closer to beginning (for those not down south), and finding out I need at least one new battery (starter), I am back on the hunt/research for a kit that will top off the batteries and maintain them.

I have used Lake Lites solar dock lites, and have been very impressed. Our lake floods a couple times a year with our gangway going underwater, yet the lights continue to shine at night, both out of water and underwater. So it got me looking back at their website, and I came across a kit that they are offering for dual battery setups. Dual Battery Solar Kit. In reading through the description, and going through some of the different manuals (links not always working), I feel like this might be a nice all in one kit. But I have some questions, which I have sent to the company, but figured I would ask a few here as well.

- Are the dual 20w panels sufficient enough to charge or top off, while also maintaining? I am/was under the impression that more was needed. But knowing they use these kits for boat lifts (assuming they work well), it is essentially the same setup. Solar panel charges a battery that is then used to raise and lower a boat lift. Or in my case, solar panel charges a battery that is then used to start boat, or play music on boat.
- Max Power - 20w
- Rated Voltage - 18 volts
- Rated current - 1.12 amps
- Their description isn't great in that it states you get dual regulators, but then you also have to click the box next to pole length. Are the regulators sufficient? I am assuming they are for the system, but will they truly control the charge/topping off/maintaining based on the description/specs for the unit?
- If you have your boat at the dock and say you are wanting to play some music, is it possible to have the batteries connected to the solar panel (charging) while also playing music? Or is that potentially too much draw or demand in that the regulator is trying to "refill" the battery, but say the battery is depleting quicker.

Whether I use their all in one system, or try to piece something together while using theirs as a template for what to get, I feel like this is a great option (if it works) for those that don't have the ability to have power down at a dock. I would imagine the controller would be mounted in the boat similar to how people have the NOCO charger installed. Then I just have to route the cable along the dock and have the disconnect located close to the controller. As well as remembering to make sure it is disconnected before leaving. lol.

Any input/thoughts would be appreciated.

 

[zackmorris]

I just started going down this rabbit hole.

I have a 36V trolling motor battery and then a 3 battery house / starting battery setup I want to keep topped off as the boat sits in the high & dry.

What I came up with was:

Dual-Battery Solar Charging Setup for Boat​

System Overview​

This setup powers a 12V and 36V dual battery bank on a boat using a single compact 100W bifacial solar panel. It’s designed to trickle charge both systems over extended periods between outings — ideal for weekly boating schedules.

Components​

• Solar Panel:
  BougeRV 100W N-Type 16BB Bifacial Panel
  • 25% cell efficiency, bifacial design (front rated at 100W)
  • Vmp: 23.8V | Imp: 4.2A
  • Compact size: 34" × 23.1" | Weight: 12.9 lbs
  • Estimated real output: ~412.5 Wh/day with 75% system efficiency
• Charge Controllers:
  • Victron SmartSolar MPPT 75/15 → 12V battery
  • Victron SmartSolar MPPT 150/35 → 36V battery
• Batteries:
  • 12V 250Ah LiFePO₄ – currently at 75% SoC
  • 36V 100Ah LiFePO₄ – currently at 50% SoC
• Breakers & Cabling:
  • 25A breaker → Y-split MC4 connectors from panel
  • 25A breaker (12V controller) & 25A breaker (36V controller)
  • 10 AWG and 8 AWG marine tinned wire

---

Charging Performance Estimate​

Battery	Capacity	Starting SoC	Energy Needed
12V	250Ah	75%	~800 Wh
36V	100Ah	50%	~1920 Wh
Total Energy Required	–	–	~2720 Wh

• Daily Energy Generation: ~412.5 Wh/day
  (Florida sun, horizontal mount, 5.5 hrs/day)
• Recharge Time:
  

  ~6.6 days to full charge from current SoC

---

Summary​

With a single 100W bifacial panel and dual Victron MPPTs, this system can safely and reliably charge both battery banks in just under a week. It’s ideal for small- to mid-size marine systems where space is limited but uptime between trips matters.

The 75% figure on the starting / house bank is an aggressive depletion estimate, as it recharges on the cruise home. It was just an added safety as the boat sits outside. The real goal is to keep my 36V battery charged and ready since it currently relies shore power to charge.

 

[Zackdadams]

Just keep in mind, solar is not as efficient as you think.

I use it on many different scenarios, and it can be hit or miss.

Cloudy days or weeks can kill your charging.

Let us know your results.