I'd like to add a system to charge a lithium battery, specifically for the trolling motor in my dinghy. I have a standard lead acid battery and solar assist now and do not want to change that. What's the best way to do this?
Lithium Trolling Battery
- Thread starter DanMaine
- Start date
You will need a solar controller that is programmed to handle LFP batteries and a shore power charger.
The Shore power charger is pretty easy, this one from Victron (Amazon Link) is the one I use.
The solar power maybe a bigger issue because the panel has to have a fairly high open circuit voltage for the controller to work, at least 19 or 20 volts. At least for the Victron controllers the VOC needs to be 5v higher than the battery voltage.
Depending on your usage, you may not need to have a solar panel. The LFP battery will give you almost double the run time of your LA battery, assuming equal capacities.
The Shore power charger is pretty easy, this one from Victron (Amazon Link) is the one I use.
The solar power maybe a bigger issue because the panel has to have a fairly high open circuit voltage for the controller to work, at least 19 or 20 volts. At least for the Victron controllers the VOC needs to be 5v higher than the battery voltage.
Depending on your usage, you may not need to have a solar panel. The LFP battery will give you almost double the run time of your LA battery, assuming equal capacities.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 23,053
The best way is so subjective.
Since we do not have any knowledge about your trolling motor or the size of the battery (AmpHours), the best I can offer is general ideas.
Good luck. Share your solution.
Since we do not have any knowledge about your trolling motor or the size of the battery (AmpHours), the best I can offer is general ideas.
- WattCycle.com has a variety of Lithium batteries they market as "Trolling Motor" batteries. They also offer solar panels to support the batteries.
- GrapeSolar and other companies make rigid panels that can be attached to a fixed surface (either removable or permanent.
- There are several builders of "Flexible" solar panels that meet the needs of attachment to curved decks and bimini covers that could be adapted to your solar charging needs.
Good luck. Share your solution.
I have a 50Ah / 12V lithium for mine. So far I've mostly been good charging it ashore, but I also have a solar panel with MPPT that I can manually plug into either the house bank or dinghy. I also have a Renogy DC to DC charger waiting to be installed for longer trips. However...with a DC/DC, you need to get the energy to charge it from *somewhere*. Either you're stealing it from your house bank, or you need to be running the engine while you charge.
Passive solar gets a little tricker: how do you prioritize which battery? One solution might be just to put a second MPPT on your dinghy battery. You could try supplying both from the same solar panel and let them fight it out. They should generally share but they might oscillate back-and-forth, which could be bad (batteries don't like ripple currents). Some DC/DC chargers have a voltage sense that only turns on when the input is above a certain voltage, so they only come on with the alternator and don't drain the house battery. If you want to try this approach with solar, an "under-sized" charger might be your friend. A 30A charger that kicks on at 14V will immediately collapse the voltage and shut itself off again. But a 5A charger being fed by a 200W panel will just siphon a little off the top, even at half sun.
Passive solar gets a little tricker: how do you prioritize which battery? One solution might be just to put a second MPPT on your dinghy battery. You could try supplying both from the same solar panel and let them fight it out. They should generally share but they might oscillate back-and-forth, which could be bad (batteries don't like ripple currents). Some DC/DC chargers have a voltage sense that only turns on when the input is above a certain voltage, so they only come on with the alternator and don't drain the house battery. If you want to try this approach with solar, an "under-sized" charger might be your friend. A 30A charger that kicks on at 14V will immediately collapse the voltage and shut itself off again. But a 5A charger being fed by a 200W panel will just siphon a little off the top, even at half sun.
Let me add: I already have a lead acid system with a solar panel controlled well with a Victron MPPT 75115. I'd like to add a way of charging a separate lithium battery just for a dinghy. I know these two different batteries have different charging profiles. I am thinking I need a separate controller that takes power from the main ships lead acid battery bank, perhaps only one under power, but I'm throwing it out there to see if there's a way of using the solar panel too. Maybe I would need a separate manual switch to go from one controller to the other with the solar panel?
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 23,053
From your description, it seems that a DC-DC charger could be placed between your existing system and the LiFePO4 trolling battery. Connect the trolling battery to the charge wires and then switch on the DC-DC charger.
Victron has one of these.
www.victronenergy.com
Victron has one of these.
Orion-Tr Smart DC-DC Charger Isolated | Victron Energy
The Orion-Tr Smart DC-DC charger is an adaptive 3-stage charger (bulk – absorption – float) designed for dual battery systems, such as in vehicles or on boats where the starter battery (hence the alternator) is used to charge the service battery. The name "Smart" comes from its built-in...
www.victronenergy.com
- "the charger can be monitored and configured via Bluetooth and can be remotely controlled via a remote on/off switch and has an engine running detection mechanism."
The trolling battery can be charged directly from the house bank by using a DC-DC charger, like the Orion Smart Charger. The small 18a one would be fine. What ever source is charging the house batteries will then also charge the trolling motor, alternator, solar, or shore. It can be programmed with a minimum input voltage so that charging the trolling battery doesn't kill the house battery.