Although admittedly not common for off-grid solar, 36v/3-12v series battery systems are extremely common for marine trolling motor applications. I'm trying to figure out the most cost effective way to recharge (not just trickle/maintain) a 50ah system that will be used 2-3 hours then stored for several days at a remote dock without shore power. This typically equates to about a 25% discharge or 12.5ah/450Wh so it seems like a 100-300W solar panel would fit the bill. Available ready to go systems are sold with one 36v charge controller, which does not seem like the best way to charge the 3-12v cells. All 120V marine chargers for this application use individual 12 banks with individual cell monitoring and charging. Can you successfully parallel connect 3-12v charge controllers to a single solar panel ? I haven't been able to find any 36v charge controllers with 3-12v charge outputs either. Mounting a single 100-300W solar panel plus a control enclosure on a dock is a big enough hassle. Having to install three panels would be a huge pain. Any suggestions would be greatly appreciated
Solar Charging of Common 3 @ 12v Series 36v Trolling Motor Battery Bank
- Thread starter pts1956
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MTM98290
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Victron 100/20 mppt can be adjusted to 36v. I think it can be done via bluetooth if you buy a Smartsolar model, I could be wrong about this.
Midnite Solar Kid can be set to 36v also and comes in a marine version, but it is larger and 3x the price. This only requires setting via buttons and a menu
I am sure there are many big Outback, Midnite, Schneider, and Morningstar charge controllers that can charge 36v too, but those are way beyond overkill.
The solar array voltage must be 5v over to start charging and 1v over to continue.
3 25w panels in series would be roughly 54V at 1.5A it will likely take days to charge, but they are easy to deal with and can be mounted easily.
3 100w panels in series would be 54-62v @ 5A
It will likely charge pretty well with 300w.
1 larger panel with a high cell count such as 132 or 156 cell panels will have a high be 54-58v but they are 7'x4' and 440-550w which is way larger than you likely need.
Sounds like a neat project. Let us know what you set up.
Midnite Solar Kid can be set to 36v also and comes in a marine version, but it is larger and 3x the price. This only requires setting via buttons and a menu
I am sure there are many big Outback, Midnite, Schneider, and Morningstar charge controllers that can charge 36v too, but those are way beyond overkill.
The solar array voltage must be 5v over to start charging and 1v over to continue.
3 25w panels in series would be roughly 54V at 1.5A it will likely take days to charge, but they are easy to deal with and can be mounted easily.
3 100w panels in series would be 54-62v @ 5A
It will likely charge pretty well with 300w.
1 larger panel with a high cell count such as 132 or 156 cell panels will have a high be 54-58v but they are 7'x4' and 440-550w which is way larger than you likely need.
Sounds like a neat project. Let us know what you set up.
Thanks for your answer. Looking at this today I realized that this is an opportunity to simplify and improve things. I found a really reasonable 36v/50ah LifePO4 Battery with BMS and High/Low Temp ($280 and 20kg vs the 210lbs plus (3) 100ah Lead Acid Batteries I have now!) Also sourced a used Kyocera 265W 36v Panel ($50) and an Amazon ($36) PWM 12/24/36/48 Solar Charge controller. Even if the battery turns out to be less than great, the price is right for a real world test ("Name Brand" 50ah 36v Lion's are from $800-$1800).
The greatest advantage of LifePO4 is that they are lighter at equivalent ah capacity BUT you find that since you can actually use 100% capacity (vs Lead acid 50% of rated on a good day) you can actually drop to 50% of Lead Acid Capacity and really save some space and weight. My brother-in- law has a big, heavy 21ft Bass Boat and he can use his 36v Trolling Motor hard for a full day of fishing and ends up using only 40% of the (3) 50ah 12v series connected LifePO4 batteries...so he doesn't really have to charge them right away. The former 100ah Lead Acid batteries would work all day too, but would be dead at the end of the day.
I'll keep you updated on how this works out.
The greatest advantage of LifePO4 is that they are lighter at equivalent ah capacity BUT you find that since you can actually use 100% capacity (vs Lead acid 50% of rated on a good day) you can actually drop to 50% of Lead Acid Capacity and really save some space and weight. My brother-in- law has a big, heavy 21ft Bass Boat and he can use his 36v Trolling Motor hard for a full day of fishing and ends up using only 40% of the (3) 50ah 12v series connected LifePO4 batteries...so he doesn't really have to charge them right away. The former 100ah Lead Acid batteries would work all day too, but would be dead at the end of the day.
I'll keep you updated on how this works out.
op, I broke down and bought a bluetti ac180p to charge my trolling batts, while tidy up and pack stuff away, the bluetti charges the battery.
I also have a minnota alternator charger in my little tin boat, it charges the trolling batts while I motor out to my super secret honey hole.
I also have a minnota alternator charger in my little tin boat, it charges the trolling batts while I motor out to my super secret honey hole.
