brianjonesphoto
New Member
I have 2 lfp batteries I would like to charge from a single charge controller. A 12v/150ah and a 24v/304ah.
The 12v system runs my trailer electrical system and currently uses a SBSM0 with 2 12v 100 watt panels.
The 24v system is used to recharge our electric dirt bikes and is a mobile system that is independent of the trailer but is often transported inside it.
My goal is to be able to charge both batteries from the same solar array and utilize the solar idle time to heat a dc water heater.
I’ll likely start with 2 450ish panels and a controller (sized for future expansion to 4 panels) mounted to the trailer. The current 12v panel will need to be removed for space.
Here’s where I go “off script” from the usual application. Set the mppt to output for 24v nominal. Use a 15amp buck converter in parallel to the mppt output to send metered current charge to the 12v system. This would allow the current to be sent to the 24v system. The 24v and 12v batteries would both share charge current as long as there was good sun. The 12v battery is a bit over sized and rarely sees 60% DoD so it will charge quickly. I would then set up a voltage sensing relay to divert 24v current to the water heater when the mppt output reaches 28v indicating that all batteries are fully charged and there are no other loads.
I know a better solution would be upgrading the trailer to a 24v battery but that isn’t an expense I have budget for at the moment.
Thanks.
The 12v system runs my trailer electrical system and currently uses a SBSM0 with 2 12v 100 watt panels.
The 24v system is used to recharge our electric dirt bikes and is a mobile system that is independent of the trailer but is often transported inside it.
My goal is to be able to charge both batteries from the same solar array and utilize the solar idle time to heat a dc water heater.
I’ll likely start with 2 450ish panels and a controller (sized for future expansion to 4 panels) mounted to the trailer. The current 12v panel will need to be removed for space.
Here’s where I go “off script” from the usual application. Set the mppt to output for 24v nominal. Use a 15amp buck converter in parallel to the mppt output to send metered current charge to the 12v system. This would allow the current to be sent to the 24v system. The 24v and 12v batteries would both share charge current as long as there was good sun. The 12v battery is a bit over sized and rarely sees 60% DoD so it will charge quickly. I would then set up a voltage sensing relay to divert 24v current to the water heater when the mppt output reaches 28v indicating that all batteries are fully charged and there are no other loads.
I know a better solution would be upgrading the trailer to a 24v battery but that isn’t an expense I have budget for at the moment.
Thanks.
