Solar Charger Suggestions

[tjcarlin]

Hey all. I just replaced my start battery with a Grp 27 and my house battery with a Grp 31. I will be keeping my boat in the water for the next 5 months but the spot I have does not offer shore power. I am looking to install a solar charger for each battery but am not sure what sizes I would need. If any of you have found one(s) that you like, and are working, I would love to hear some suggestions. Thank you.

 

[oakley24]

Next spring, I am going to be in the same boat as you (pun intended), docking without shore power. I have not implemented this yet, but have tested in my driveway and so far it works well on my 2 Group 24 batteries. I got this solar panel on Amazon (You could probably get a higher Wattage panel to be safe)

SOLPERK Solar Panel Kit 20W 12V, Solar Battery Trickle Charger Maintainer

And since the included controller only has one output, I replaced it with this dual output controller so i could connect both batteries to one solar panel

Temank Dual Battery Solar Charge Controller 20A 12V 24V Duo-Battery Solar Controller for RVs Caravans and Boats

I am going to redo the wiring and use 10 gauge tinned marine wire, but my testing so far has been to connect both batteries that were around 12.3V (about 70%) on a partly cloudy day, and they both easily got to 12.75V or so the same day. Before I trust my boat with this solution, I plan on testing with load and over a couple of days, but just haven't had the time yet

 

[212s]

If you're intention is to simply maintain the batteries when away from the boat, then a 20w panel with do the job for both batteries. However if you intend to run the house battery down while using the boat (loud tunes while floating), and then charge it up again at the slip, you'll need a 200w panel minimum for several hours of daylight otherwise you risk not fully charging the battery and eventually killing it. It all depends on your usage.

 

[tjcarlin]

Thank you both. I do use the house quite a bit while anchored down and listening to music. It sounds like exceeding 100W may be a good idea. Would one for each battery be better, or would one, wired into both, with the controller be enough?

 

[FSH 210 Sport]

I think you need two panel charger set ups, one for the start and one for the house. Its also important to make sure that the dvsr / charge relay is not active when using your solar charger.

If you were to use 50% of your house battery, or 50Ah on a given day that is how much you are going to have to put back into a lead acid battery, PLUS extra to account for the resistance inherent in lead acid battery charging, as well as the less than advertised output of the solar charger.

Lets say you have a 150 W panel, cut that by 40% so the efficiency is 60% that leaves 90W. 90 / 14.5 =6.2A of charging power. 50Ah / 6.2A=8.06 hrs to charge that house battery back up again on the bulk charge, but lead acid batteries require up to 8 hours of a float charge to charge them properly. Increase the panel size to 200W and you reduce the bulk charge time to 6 hours, but the float charge time remains upwards of 8 hours.

I’m assuming these are flooded lead acid batteries, you will also need to check the specific gravity and balance of the cells of the batteries regularly to make sure you are getting a proper charge, and if not you will have to pull them out and take them home and charge them or these batteries will enter a death spiral.. flooded lead acid batteries need regular equalizing charges as well to keep the cells balanced, keep the battery working optimally, and give the best life out of it.

Here is another idea, one that one of our JBN members set up, who, like you does not have shore power. He installed an on board charger, I think it was a NOCO 10x2. He would then bring one of those lithium power station packs with him that produces 120VAC. While out on the water he would just hook this “battery / inverter” up to the onboard charger and let it do its thing..at the end of the day he would just unplug the power pack and take it home to recharge it. If it were me going this route, I’d get a Victron IP67 charger to charge the house battery with at least, this charger has 25A (or 10A) of output and can be used as a power supply while it is charging the battery. The 25A would be more than enough to carry the load of your stereo as well as charging the batteries. The nice thing about the Victron charger is the bluetooth connectivity so you can see what the charger is really doing as far as amperage output and where it is at in the charge cycle, and it is highly configurable.

I’d also suggest a Victron smart shunt so you can monitor your batteries. The basic one is Bluetooth and shows everything you would want to know about your battery at any given time. There is a link in my signature about LiFePO battery upgrades and there is more information in that thread about the smart shunt and what GUI looks like.

 

[212s]

Thank you both. I do use the house quite a bit while anchored down and listening to music. It sounds like exceeding 100W may be a good idea. Would one for each battery be better, or would one, wired into both, with the controller be enough?

If you use the boat every weekend, you won't need anything for the start battery as it'll be recharged easily by the engines. The house battery will need the solar charger, or power pack like @FSH 210 Sport mentioned.

For off-season storage you would need a maintainer for the start as well though. That's where the onboard 2-bank charger and power pack idea would work well.