How To Upgrade To a Victron Solar Controller

[profcbutler]

I have a 2025 R25. It came with the Abso (Kisae) DC to DC charger. Abso was also used for the charger and inverter. Nothing against Kisae but the Bluetooth reporting in the Victron world is a whole lot better. One of the challenges I have is seeing (clearly) what is going on with the solar panel at any point in time as well as historical. Based on prior suggestions from this wonderful group on Tugnuts I have placed two additional Victron monitoring devices on the Thruster and Starter battery (easy install). It was also suggested that upgrading to a Victron solar controller is a worth while endeavor. I just took the boat out of the water for the winter and have some extra time on my hands! So my question to the group is this....

Has anyone done a Victron Solar controller (or monitoring device) on my year and model (with the above configuration)? Again, my main goal is to get better information from the solar panel. I have heard this is a fairly easy upgrade but based on my current configuration it looks like the Abso DC to DC battery charger needs to be swapped out (I am assuming). I believe the input ports are different between the Victron and Abso. It does not look like a one to one swap out. I have not been able to find any Youtube install videos on this. Has anyone done this and if so what does the install look like?

 

[Brian John]

The model of the boat should make no difference. On an R-31, I upgraded to a Victron 3000-watt inverter, solar charger, GX 50 display, and Lynx Distribution. Separately, I installed two AC Digital displays for voltage and current.

 

[Submariner]

I have a 2025 R25. It came with the Abso (Kisae) DC to DC charger. Abso was also used for the charger and inverter. Nothing against Kisae but the Bluetooth reporting in the Victron world is a whole lot better. One of the challenges I have is seeing (clearly) what is going on with the solar panel at any point in time as well as historical. Based on prior suggestions from this wonderful group on Tugnuts I have placed two additional Victron monitoring devices on the Thruster and Starter battery (easy install). It was also suggested that upgrading to a Victron solar controller is a worth while endeavor. I just took the boat out of the water for the winter and have some extra time on my hands! So my question to the group is this....

Has anyone done a Victron Solar controller (or monitoring device) on my year and model (with the above configuration)? Again, my main goal is to get better information from the solar panel. I have heard this is a fairly easy upgrade but based on my current configuration it looks like the Abso DC to DC battery charger needs to be swapped out (I am assuming). I believe the input ports are different between the Victron and Abso. It does not look like a one to one swap out. I have not been able to find any Youtube install videos on this. Has anyone done this and if so what does the install look like?

I did a solar upgrade on an R25-OB for a fellow boater. I installed a Victron 100/30 Smartsolar MPPT controller, took off the existing solar panel and replaced it with a pair of 210 watt solar panels.
It's fairly straightforward on the R25. I mounted the solar controller in the cave on the back bulkhead. With your DMT1250, you simply have to disconnect the solar + and - wires and back haul them to wherever you want to install the solar controller. Then run some wire back to the house battery with a fuse for the 12volt house battery side of the solar controller.

Note: You do not swap out the DMT1250. It's a dual-purpose device. It does engine to house DC to DC charging for engine charging of the LFP house bank, and it does solar charging (but not at the same time). Installing a dedicated solar charger provides for solar and engine charging at the same time.

I'm currently working on an electrical overview of the LE's with LFP to publish on our YouTube channel. Similar to the one I did for the NW edition, but specific to the LE's with LFP.

 

[Submariner]

The model of the boat should make no difference. On an R-31, I upgraded to a Victron 3000-watt inverter, solar charger, GX 50 display, and Lynx Distribution. Separately, I installed two AC Digital displays for voltage and current.

The electrical systems are different. Having a DMT1250 DC to DC charger/Solar controller means the boat is LFP. The NW editions are AGM batteries and started out with a PWM solar controller. The end result is the same, and the work is nearly identical, though, whether it's a NW edition or LE with LFP. The R25-OB is actually pretty easy to run wire for 12volt DC, and has plenty of room to install the solar controller.

 

[profcbutler]

I did a solar upgrade on an R25-OB for a fellow boater. I installed a Victron 100/30 Smartsolar MPPT controller, took off the existing solar panel and replaced it with a pair of 210 watt solar panels.
It's fairly straightforward on the R25. I mounted the solar controller in the cave on the back bulkhead. With your DMT1250, you simply have to disconnect the solar + and - wires and back haul them to wherever you want to install the solar controller. Then run some wire back to the house battery with a fuse for the 12volt house battery side of the solar controller.

Note: You do not swap out the DMT1250. It's a dual-purpose device. It does engine to house DC to DC charging for engine charging of the LFP house bank, and it does solar charging (but not at the same time). Installing a dedicated solar charger provides for solar and engine charging at the same time.

I'm currently working on an electrical overview of the LE's with LFP to publish on our YouTube channel. Similar to the one I did for the NW edition, but specific to the LE's with LFP.

Martin, I was hoping you would respond to this. Thank you! Just a few questions...
If I connect it up in the way you are suggesting it would only support the house batteries. Am I wrong in thinking that the current configuration keeps a charge from the solar on the starter and thruster batteries?

In the marina I am at I have no access to power over the winter. Keeping a trickle charge on those two batteries is not an option...hate to have to pull them and bring them home. Of course I will remove all the loads but I hate not being able to charge them time to time. Any thoughts on this? As for the house batteries I am working with the boat wrap folks to put a clear panel at the top to allow sunlight to charge the house batteries from the panel.

What gauge wire would you suggest to put back to the batteries from the Victron MPPT ( I would mount it on the bulkhead in the cave as you suggested. Close to the house batteries on the port side)?

What Victron model would you suggest? You have done a good job prior explaining parallel versus serial with multiple panels. For now I am going to stay with the OEM panel (I think its around 180w).
Very much appreciate the guidance!

 

[Submariner]

Martin, I was hoping you would respond to this. Thank you! Just a few questions...
If I connect it up in the way you are suggesting it would only support the house batteries. Am I wrong in thinking that the current configuration keeps a charge from the solar on the starter and thruster batteries?

In the marina I am at I have no access to power over the winter. Keeping a trickle charge on those two batteries is not an option...hate to have to pull them and bring them home. Of course I will remove all the loads but I hate not being able to charge them time to time. Any thoughts on this? As for the house batteries I am working with the boat wrap folks to put a clear panel at the top to allow sunlight to charge the house batteries from the panel.

What gauge wire would you suggest to put back to the batteries from the Victron MPPT ( I would mount it on the bulkhead in the cave as you suggested. Close to the house batteries on the port side)?

What Victron model would you suggest? You have done a good job prior explaining parallel versus serial with multiple panels. For now I am going to stay with the OEM panel (I think its around 180w).

Your boat is a LE with LFP batteries. You have a DMT1250, which is an MPPT solar controller. A disadvantage to this device is you get either engine charging or solar charging, but not both at the same time. Your boat currently only gets solar power to the house bank.

The engine and thruster batteries are fairly well isolated from electrical loads. AGM batteries lose up to 3% charge a month. If you shut off the DC switch for the house and engine and thruster, that'll isolate those banks from the loads. All that would remain is the 24x7 loads off the house bank. The factory solar panel, with LFP should be able to keep up with that throughout the winter.

Being a 2025 model, you probably have the two G31 Dakota 320AH batteries. LFP batteries can't be charged in sub-freezing temperatures. However, those G320 aH batteries from Dakota have a thermal blanket. The BMS will turn it on when the temp falls below 40 degrees to keep the LFP cells warm so they can be charged in sub-freezing temps (down to around -10dgrees F). Your Victron battery monitor won't accurately show this since the load is within the battery and bypasses the shunt. I don't know what part of the country you are in. If it's Anchorage or Fairbanks, I'd give different guidance than if it were Seattle as the length of time spent frozen with the amount of sunshine provided matters. It also matters how many months you plan to put the boat away for.

If you do add a dedicated solar charger, I'd go with a Victron MPPT Smartsolar 100/30 or the 150/35. That'd future proof your setup should you ever decide to add a second panel in the future. The max wire size those solar controllers support is 6AWG, and install a 40 amp fuse. The simplest way to do this is to replace one of the MRBF fuse holders on your bus bar next to you T-class fuse with Dual MRBF Fuse Block.

This is what I'd recommend.

https://www.bluesea.com/products/2151/Dual_MRBF_Terminal_Fuse_Block_-_30_to_300A

This makes it easy to connect the solar controller to the house bank, properly fused. With your existing solar panel, you could get away with 10AWG wire on a 30 amp ATC fuse. But here again, it all depends what you plan to do with the boat in the future.

AGM batteries, and LFP, can be left unattended for a period of time without harm, without any loads on them. When we left for our SE Alaska trip, we were gone for 55 days. I had three vehicles in my driveway without solar, without a trickle charger, and without being ran, and started up just fine.

 

[profcbutler]

Your boat is a LE with LFP batteries. You have a DMT1250, which is an MPPT solar controller. A disadvantage to this device is you get either engine charging or solar charging, but not both at the same time. Your boat currently only gets solar power to the house bank.

The engine and thruster batteries are fairly well isolated from electrical loads. AGM batteries lose up to 3% charge a month. If you shut off the DC switch for the house and engine and thruster, that'll isolate those banks from the loads. All that would remain is the 24x7 loads off the house bank. The factory solar panel, with LFP should be able to keep up with that throughout the winter.

Being a 2025 model, you probably have the two G31 Dakota 320AH batteries. LFP batteries can't be charged in sub-freezing temperatures. However, those G320 aH batteries from Dakota have a thermal blanket. The BMS will turn it on when the temp falls below 40 degrees to keep the LFP cells warm so they can be charged in sub-freezing temps (down to around -10dgrees F). Your Victron battery monitor won't accurately show this since the load is within the battery and bypasses the shunt. I don't know what part of the country you are in. If it's Anchorage or Fairbanks, I'd give different guidance than if it were Seattle as the length of time spent frozen with the amount of sunshine provided matters. It also matters how many months you plan to put the boat away for.

If you do add a dedicated solar charger, I'd go with a Victron MPPT Smartsolar 100/30 or the 150/35. That'd future proof your setup should you ever decide to add a second panel in the future. The max wire size those solar controllers support is 6AWG, and install a 40 amp fuse. The simplest way to do this is to replace one of the MRBF fuse holders on your bus bar next to you T-class fuse with Dual MRBF Fuse Block.

This is what I'd recommend.

https://www.bluesea.com/products/2151/Dual_MRBF_Terminal_Fuse_Block_-_30_to_300A

This makes it easy to connect the solar controller to the house bank, properly fused. With your existing solar panel, you could get away with 10AWG wire on a 30 amp ATC fuse. But here again, it all depends what you plan to do with the boat in the future.

AGM batteries, and LFP, can be left unattended for a period of time without harm, without any loads on them. When we left for our SE Alaska trip, we were gone for 55 days. I had three vehicles in my driveway without solar, without a trickle charger, and without being ran, and started up just fine.

Martin, very much appreciate all the recommendations. I do have the Dakota 320ah batteries and store the boat on the upper chesapeak in MD. Real cold is not an issue, but it is stored for around 6 months. I also appreciate the Blue Sea block recommendations (did not think about that). Look forward to all the videos you post. You are greatly appreciated by all of us Ranger Tug owners!

 

[bonjon]

I have a similar question, I am in the process of purchasing a 2025 Ranger Tug R-27. I do not have the vessel in my possession yet as I'm in getting ready to order a survey. I live in South Florida and wish to run the air conditioning quite a bit. My question is; can I add another solar panel to the existing and also add one or possibly two more house batteries? Kinda pre-planning.

 

[Submariner]

I have a similar question, I am in the process of purchasing a 2025 Ranger Tug R-27. I do not have the vessel in my possession yet as I'm in getting ready to order a survey. I live in South Florida and wish to run the air conditioning quite a bit. My question is; can I add another solar panel to the existing and also add one or possibly two more house batteries? Kinda pre-planning.

I recommend doubling up on solar and installing a dedicated MPPT solar controller. I generally don't recommend additional batteries. Solar has a much larger ROI. If you are looking to run the AC quite a lot, it's possible that the boat just isn't big enough to add enough solar or enough additional batteries and thus, a portable generator may be best for you.

This post provides more detail.

Post in thread 'How To Upgrade To a Victron Solar Controller'

Oct 20, 2025

Martin, I was hoping you would respond to this. Thank you! Just a few questions...
If I connect it up in the way you are suggesting it would only support the house batteries. Am I wrong in thinking that the current configuration keeps a charge from the solar on the starter and thruster batteries?

In the marina I am at I have no access to power over the winter. Keeping a trickle charge on those two batteries is not an option...hate to have to pull them and bring them home. Of course I will remove all the loads but I hate not being able to charge them time to time. Any thoughts on this...

• Submariner

• 

 

[bonjon]

I recommend doubling up on solar and installing a dedicated MPPT solar controller. I generally don't recommend additional batteries. Solar has a much larger ROI. If you are looking to run the AC quite a lot, it's possible that the boat just isn't big enough to add enough solar or enough additional batteries and thus, a portable generator may be best for you.

This post provides more detail.

Post in thread 'How To Upgrade To a Victron Solar Controller'

Oct 20, 2025

Martin, I was hoping you would respond to this. Thank you! Just a few questions...
If I connect it up in the way you are suggesting it would only support the house batteries. Am I wrong in thinking that the current configuration keeps a charge from the solar on the starter and thruster batteries?

In the marina I am at I have no access to power over the winter. Keeping a trickle charge on those two batteries is not an option...hate to have to pull them and bring them home. Of course I will remove all the loads but I hate not being able to charge them time to time. Any thoughts on this...

• Submariner

• 

Thank you Martin. ( Watching your YouTube videos and love the content) Not quite understanding, would I remove the existing solar controller and replace it with something else? What is ROI? Sorry was building contractor and worked with wood before retiring

 

[Submariner]

Thank you Martin. ( Watching your YouTube videos and love the content) Not quite understanding, would I remove the existing solar controller and replace it with something else? What is ROI? Sorry was building contractor and worked with wood before retiring

A 2025 R27 will come with LFP (LiFePo4/Lithium batteries). It will have a Kisae DMT1250, which is a dual-purpose device. It performs engine to house battery charging, it also performs solar to house battery charging, so you do not want to remove it. It performs engine or solar charging, but not both at the same time.

Install a dedicated solar controller, back-haul the solar panel wires from the DMT1250 to the dedicated solar controller. Then you'll get solar charging at the same time you get engine charging.

ROI, return on investment. Adding another battery is just adding another bucket to hold electrons, which gets filled primarily on shore power as solar and engine charging are considerably less than shore power charging.

Let me give you this example. I have 420 watts of solar. I have 320 amp-hours of house battery bank. My boat uses 100 amp-hours a day. My solar panels provide me over 100 amp-hours a day, every day. It's like adding a battery that recharges itself daily.

I have a power management spreadsheet available to let you play with the numbers so you can see the difference solar makes over adding more batteries.

How Much Power Does Your Boat Actually Use?

csurf.co

 

[bonjon]

Thank you. I appreciate your help. If you ever get to Southwest Florida or the Keys give me a shout.

 

[georgeboarhunter]

A 2025 R27 will come with LFP (LiFePo4/Lithium batteries). It will have a Kisae DMT1250, which is a dual-purpose device. It performs engine to house battery charging, it also performs solar to house battery charging, so you do not want to remove it. It performs engine or solar charging, but not both at the same time.

Install a dedicated solar controller, back-haul the solar panel wires from the DMT1250 to the dedicated solar controller. Then you'll get solar charging at the same time you get engine charging.

ROI, return on investment. Adding another battery is just adding another bucket to hold electrons, which gets filled primarily on shore power as solar and engine charging are considerably less than shore power charging.

Let me give you this example. I have 420 watts of solar. I have 320 amp-hours of house battery bank. My boat uses 100 amp-hours a day. My solar panels provide me over 100 amp-hours a day, every day. It's like adding a battery that recharges itself daily.

I have a power management spreadsheet available to let you play with the numbers so you can see the difference solar makes over adding more batteries.

How Much Power Does Your Boat Actually Use?

csurf.co

Martin, thanks for your wisdom on this important topic. I am wondering, as I look to upgrade, where to obtain the correct wires (gauge and type) and also the correct connectors between the wires and the solar panels. Are they standard solar connectors? If I string two together, I will need connectors and wiring and I want to be sure to get the right stuff. Any advice appreciated.

George R. Brown, MD
Ranger 31CB 2023
Tioga Tide

 

[georgeboarhunter]

A 2025 R27 will come with LFP (LiFePo4/Lithium batteries). It will have a Kisae DMT1250, which is a dual-purpose device. It performs engine to house battery charging, it also performs solar to house battery charging, so you do not want to remove it. It performs engine or solar charging, but not both at the same time.

Install a dedicated solar controller, back-haul the solar panel wires from the DMT1250 to the dedicated solar controller. Then you'll get solar charging at the same time you get engine charging.

ROI, return on investment. Adding another battery is just adding another bucket to hold electrons, which gets filled primarily on shore power as solar and engine charging are considerably less than shore power charging.

Let me give you this example. I have 420 watts of solar. I have 320 amp-hours of house battery bank. My boat uses 100 amp-hours a day. My solar panels provide me over 100 amp-hours a day, every day. It's like adding a battery that recharges itself daily.

I have a power management spreadsheet available to let you play with the numbers so you can see the difference solar makes over adding more batteries.

How Much Power Does Your Boat Actually Use?

csurf.co

Do the Ranger tugs use MC4 connectors and 10AWG wiring, pretty much standard? Thanks.

 

[Submariner]

Do the Ranger tugs use MC4 connectors and 10AWG wiring, pretty much standard? Thanks.

I've never seen the factory use MC4 connectors. It's 10AWG wire, butt spliced with heat shrink to the solar wire. When I do solar upgrades on other boats, I add MC4 connectors to the boat, as the new panels will come with MC4 and I don't want to cut the wires on a new panel under warranty.

I illustrate the easiest way I've found to add MC4 cables in this video.

Ranger Tug R27 Solar: How to Install 400 Watts Without Crimping a Single MC4 Connector

 

[georgeboarhunter]

Very helpful video! What I am trying to do is set up a removable, second 100 watt panel that I can place outside of the shrink wrap, which will be covering up my main panel in the winter storage outside, in full sun. I want to use all MC4 connectors, so I can set up the two panels in parallel (so i can use the second panel along with the primary if I choose to). Can I avoid the butt crimping and just put on MC4 connectors coming out of the boat, then Y-splitters, and MC4 to each of the two panels?

George R. Brown, MD
Ranger Tug 31CB, 2023

 

[az9133bm]

Consider contacting Grant Wilson at FreedomVanGo in Jacksonville FL. Grant is ABYC certified. He and his team installed our conversion and we love it. See YouTube videos:

 

[Submariner]

Very helpful video! What I am trying to do is set up a removable, second 100 watt panel that I can place outside of the shrink wrap, which will be covering up my main panel in the winter storage outside, in full sun. I want to use all MC4 connectors, so I can set up the two panels in parallel (so i can use the second panel along with the primary if I choose to). Can I avoid the butt crimping and just put on MC4 connectors coming out of the boat, then Y-splitters, and MC4 to each of the two panels?

George R. Brown, MD
Ranger Tug 31CB, 2023

Out of the back of the boat, up on the roof, is 10AWG wire. If you crimp an MC4 connector onto 10AWG wire, it won't be waterproof. MC4 connectors are designed for Solar Wire. Solar wire is close to 10AWG wire, however, the insulation is 2x as thick, since solar panels are always outside, exposed to the elements. MC4 connectors are designed for Solar Wire not 10AWG wire.

10AWG comes out the top of the boat, it's crimped to the solar wire from the solar panel and heat-shrunk. You could cut the wire on the solar wire side of the factory crimp, and then crimp an MC4 connector to that.

I have done it both ways. My boat, being the first solar upgrade I did, I crimped MC4 connectors onto the solar wire portion of the cable. I cut the cable on the factory solar panel too short, which made it difficult to re-use the old panel (I gave it to a friend for his R29). After messing with MC4 crimp, their special crimp tool, and connectors... I later found out that just doing a butt splice with heat shrink was faster and much easier to do as I illustrated in a previous post. Simply buy a 3' MC4 extension, cut them in half, and butt splice/crimp them to your boat.

Start at timestamp 13:50 where I show how to do MC4 connectors. This video is 5 years old, and was the first and last time I crimped MC4 connectors on any boat.

 

[georgeboarhunter]

ok, thanks for that advice!