Going Lithium

[Isaac-1]

a good MPPT such as a Victron gets about 20%-30% more effective power out of a panel, not all MPPT's are good. MPPT's are around 95-98% efficient, compared to around 70% for PWM. Some MPPT will also allow you to run higher voltage panels with 12V output, for example I have 40VOC panels on my roof mated to a Victron MPPT, charging 12V LiFePo4 batteries, and could have double that VOC. By comparison with PWM controllers are effectively limited to using panels with 18-20VOC. Though many of the cheaper MPPT's are limited to 25VOC

 

[Mark_K5LXP]

PWM vs MPPT

Mark B.
Albuquerque, NM

 

[Isaac-1]

Mark, I would call a lot of that information dated, with the introduction of relatively low priced MPPT's

 

[Isaac-1]

p.s. on battery brand recommendation, I recently bought a Dr Prepare 100AH LiFePo4 battery with low temperature charging protection and a 5 segment bar graph charge meter for under $150 that I have been impressed with. (using it along with a solar panel and MPPT controller to support a streaming remote security camera), the same Dr Prepare 100AH is sold with a multi attachment module with lighter socket and built in solar charge controller for $189

Amazon.com

 

[DonTom]

What is the difference between PWM and MPPT?

"The differences between PWM (Pulse Width Modulation) and MPPT (Maximum Power Point Tracking) solar controllers are as follows:

• Efficiency: MPPT controllers can be up to 30% more efficient than PWM controllers, especially in cooler climates or with higher-voltage panels.
• Cost: PWM controllers are generally less expensive, making them a budget-friendly option for smaller systems.
• Complexity: MPPT controllers are more complex and require more sophisticated technology, which can make them more challenging to install and troubleshoot.
• Versatility: MPPT controllers can handle a wider range of panel voltages and are better suited for larger, more complex systems4.
• Application: PWM controllers are ideal for smaller systems where cost is a significant concern, while MPPT controllers are preferred for larger, high-demand systems."

FWIW, I do not fully agree with the "complexity" above. They are just as simple to install as are PWM controllers in most simple solar RV systems such as your 100w worth of solar.

I use MPPT in each of my motorhomes.

-Don- Reno, NV

 

[Lou Schneider]

What is the difference between PWM and MPPT?

PWM controllers are basically a switch. They turn the solar panels on and off as needed, so the current coming out of the controller equals the current coming out. Since a solar panel's current is basically independent of the voltage they're delivering you'll only get part of the panel's total rated power.

For example, 200 watt, 36 volt panel may produce something like 5.5 amps at it's maximum power point and this will increase to maybe 6 amps into a short circuit. At 13.5 volts using a PWM controller the panel only delivers 80 watts, not 200 watts. (13.5 x 6 amps = 81 watts),

MPPT follow the panel's Maximum Power Point, converting any excess voltage coming into the panels into more current. You'll get closer to the panel's full rated power into a lower voltage load, anywhere from 85-95%. Or 12-14 amps at 13.5 volts.

 

[tlmgcamp1]

Ok...so I am going for the MPPT solar controller. They have different amperage ratings I have 100w solar on a 30amp TT and looking at 100Ah lithium. What should be the amperage rating on the controller?

 

[Lou Schneider]

Ok...so I am going for the MPPT solar controller. They have different amperage ratings I have 100w solar on a 30amp TT and looking at 100Ah lithium. What should be the amperage rating on the controller?

A controller's current rating is how much current it will put out. 100 watts is 7.4 amps at 13.5 volts, you'll likely get something like 80% of that if the panel is laying flat on your roof. So any MPPT controller rated at that current or above will work. You can go larger if you want, say to 20 or 30 amps in case you decide to add more solar panels in the future.

 

[tlmgcamp1]

Ok...this is what I have now so I will stick with 10amps as I don't want to be concerned with wire sizes

 

[Isaac-1]

The solar panel will be the limit here, a single 100 watt panel will at most put out at most about 8 amps regardless of the size of the solar controller. Something like this would be ideal Amazon.com

 

[IBTripping]

What is the difference between PWM and MPPT?

MPPT controllers are more efficient and can harvest more power from the solar panels. PWM controllers are simpler, cheaper, and more suitable for smaller systems.

 

[IBTripping]

OP needs to figure out how much wattage he's putting on his roof before buying a charge controller.

FYI -- all your Amazon links can be shortened by deleting everything from "ref=" on, like so:

Amazon.com: Victron Energy SmartSolar MPPT Solar Charge Controller (Bluetooth) - Charge Controllers for Solar Panels - 75V, 15 amp, 12/24-Volt : Patio, Lawn & Garden

Buy Victron Energy SmartSolar MPPT Solar Charge Controller (Bluetooth) - Charge Controllers for Solar Panels - 75V, 15 amp, 12/24-Volt: Energy Controllers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Thanks!!!

 

[tlmgcamp1]

Ok...settled on Victron 10amp solar controller. I see the controller is Bluetooth enabled. Does this man I don't need a smart shunt? Next is a 10amp dc-dc charger which will likely also be Victron, just to try to simplify troubleshooting. Then is the battery itself. I would like to stay away from Chinese products, but understand that might be difficult. It looks like batteries might also be Bluetooth enabled. That makes the potential for 3 apps for this setup which is way too gadgety for me. What is the simplest way to get this done? I plan to review Will Prose videos but thoughts on the 100Ah battery brands from the community would be appreciated. I need to have this all put together by early July for first trip

 

[Lou Schneider]

Ok...settled on Victron 10amp solar controller. I see the controller is Bluetooth enabled. Does this man I don't need a smart shunt? Next is a 10amp dc-dc charger which will likely also be Victron, just to try to simplify troubleshooting. Then is the battery itself. I would like to stay away from Chinese products, but understand that might be difficult. It looks like batteries might also be Bluetooth enabled. That makes the potential for 3 apps for this setup which is way too gadgety for me. What is the simplest way to get this done? I plan to review Will Prose videos but thoughts on the 100Ah battery brands from the community would be appreciated. I need to have this all put together by early July for first trip

It's hard to avoid Chinese made products, they make something like 95%+ of all lithium cells and related BMS circuitry and they've become commodity items. All the manufacturers do is assemble them in a plastic case and slap their label on it.

A shunt (bluetooth or not) measures the net current flowing in and out of the battery and so keeps track of the battery's state of charge. The charge controller only tracks how much power it's putting out, it has no way of knowing if that power is actually going into the battery or is being consumed directly by a load, nor does it know how much power is being drained out of the battery when the sun isn't shining.

If the battery is bluetooth enabled it likely supplies that information directly via it's app. You will need a shunt if you want to use a permanent display to monitor your system instead of a series of apps.

Here's an example of Victron's system monitors. Other brands may offer something similar but few offer this many options.

Battery Monitors and Monitoring Solutions - Victron Energy

Victron Energy have a comprehensive range of Battery Monitors, Battery Balancers, BMS and Shunt options, plus a wide variety of panel and system monitoring solutions (local & remote) such as the Victron GX product range for example. There’s also a range of complementary accessories. Amongst the...

www.victronenergy.com

 

[Isaac-1]

You will still need a battery monitor, as the Victron MPPT will only tell you the solar production, ie how many watts your solar panels are currently producing, and how many total watts they have produced today, yesterday, last week, etc. as well as associated details like current amps and volts coming from the panels, and battery voltage.

Victron makes some good shunt style monitors they have a couple of bluetooth smart shunts, the older version that is not water proof and a new one that is., as well as panel mount meters.

If you want a cheaper option here are 2 I can recommend depending on your needs.

First is this basic one sold under a number of brands, Binta, Qwork, Aili, etc. (Aili may be the actual manufacturer) This is a no frills panel meter for under $40, I am using a Camway branded one as I like the blue color scheme better than the orange on a Lithium converted golf cart. Amazon.com Simple to setup, works great, just be aware the included data cable means it must be located within 3 meters (9.5 ft) of the batteries.

Second cheaper choice is this one Amazon.com note 5 meter / 16 ft data cable

I have their previous very similar model which is this very similar looking model Amazon.com It works, though the setup is not very intuitive, they have removed the control box and improved the display layout on this years version while keeping the same style display panel. New model also has wifi, vs the old model being blue tooth

 

[tlmgcamp1]

Existing:

TV Fuse to trailer power = 30 amp

30 amp TT

Converter is Lithium-Compatible.

• WFCO WF-8735-AD-GE.
• Converter output to LI is 14.6VDC/32.5A

Type 27 FLA Marine/Deep Cell

Photo at Battery Box attached. Is the fused line for brakes?

Proposed:

100Ah Lithium – Brand TBD.

Victron MPPT 75-10 Controller (existing controller is 10amp but not lithium compatible)

I want to install a dc-dc charger to protect the TV from high recharge surge from the lithium. I also want to check if there is anything protecting the TV battery from giving power to the TT when the TV is not running.

Questions

1. Where should the dc-dc charger be located?

• Does in go in the TV?
• Does it go in the Battery box to intercept the wires at the battery?
• Does it go at the converter?

2. Am am seeing "Isolated" and "Non-Isolated" chargers. What is the difference?

3. Since the controller is blue-tooth enabled, and many batteries are also, do I really need a separate shunt?

Thanks in advance. I need to either get this done in the next couple of weeks before the first trip or simply buy another FLA as the battery I had sprung a leak over the winter and I now have nothing. There is nothing about this (so far) that would make me defer installation to somebody else, but my pride will not stop me from hiring somebody is this gets too techy. I have better-then-average skills for home repair (electrical, plumbing, etc.) and I have already installed some add-ons to the TT but try to stay conscious of my limitations.

Thanks to all in advance.

 

[Isaac-1]

Be aware there are a LOT of reports out there about those WFCO auto detecting converters failing to detect LiFePo4 batteries, so make sure to check the voltage output with a multimeter to confirm it has properly detected the battery type.

To answer your questions,

1, the DC-DC charger should generally be located as close as practical to the batteries, though since it does put out heat I would not locate it in the battery box, they also tend not to be weatherproof)

2. Isolated chargers are mostly used in marine installations, when you have a negative frame ground setup like in RV's and most cars and trucks, non isolated will work fine, though for your installation either would probably be acceptable.

3, This depends, if you have Bluetooth enabled batteries you can use the app to track charge level, the problem is many of these Bluetooth BMS's can't track small parasitic loads of under about 400ma, this can allow the batteries to slowly drain down while the Bluetooth App still shows at or near 100% SOC. Shunt monitors suffer from this same issue, but not to the same degree, The Victron Smart Shunt for example claims to detect down to about 10ma. The Junctek KG-F I have claims the same performance as the Victron, but I don't know how much I trust this number, though it is still much better than the JBD Bluetooth BMS in my batteries.. So it all comes down to how much accuracy you want, the Bluetooth BMS may be fine is you make sure to manually top off batteries before a trip, just don't take those readings as gospel.

 

[tlmgcamp1]

Be aware there are a LOT of reports out there about those WFCO auto detecting converters failing to detect LiFePo4 batteries, so make sure to check the voltage output with a multimeter to confirm it has properly detected the battery type.

To answer your questions,

1, the DC-DC charger should generally be located as close as practical to the batteries, though since it does put out heat I would not locate it in the battery box, they also tend not to be weatherproof)

2. Isolated chargers are mostly used in marine installations, when you have a negative frame ground setup like in RV's and most cars and trucks, non isolated will work fine, though for your installation either would probably be acceptable.

3, This depends, if you have Bluetooth enabled batteries you can use the app to track charge level, the problem is many of these Bluetooth BMS's can't track small parasitic loads of under about 400ma, this can allow the batteries to slowly drain down while the Bluetooth App still shows at or near 100% SOC. Shunt monitors suffer from this same issue, but not to the same degree, The Victron Smart Shunt for example claims to detect down to about 10ma. The Junctek KG-F I have claims the same performance as the Victron, but I don't know how much I trust this number, though it is still much better than the JBD Bluetooth BMS in my batteries.. So it all comes down to how much accuracy you want, the Bluetooth BMS may be fine is you make sure to manually top off batteries before a trip, just don't take those readings as gospel.

Thank you Isaac,

In #1, I assume you mean the TT battery? That should not be an issue as the battery is on the tongue and I have a storage compartment across the front of the TT, which is where the solar controller is. So a few feet away. The question is wiring. The charger has one set of input wires and one set of output wires. What wire am I interrupting to insert the charger?

 

[Isaac-1]

Generally speaking the wire you want to connect the DC-DC charger to the aux power wire from the 7 blade towing connector, then connect the output from the DC-DC charger to the battery, right now that wire is most likely directly connected to the battery, though it may go through a self resetting breaker first.

p.s. don't assume color code for the wire, positive might be red, might be black might even be brown depending which wiring color scheme the RV manufacturer used. In the old days trailer wiring was black positive / white negative, even though in more modern times you often see red as positive and black as negative, then to add complexity in the boating industry they decided negative should be yellow, etc.

 

[tlmgcamp1]

Generally speaking the wire you want to connect the DC-DC charger to the aux power wire from the 7 blade towing connector, then connect the output from the DC-DC charger to the battery, right now that wire is most likely directly connected to the battery, though it may go through a self resetting breaker first.

p.s. don't assume color code for the wire, positive might be red, might be black might even be brown depending which wiring color scheme the RV manufacturer used. In the old days trailer wiring was black positive / white negative, even though in more modern times you often see red as positive and black as negative, then to add complexity in the boating industry they decided negative should be yellow, etc.

Isaac,

THere are only 2 sets of wires at the battery. One is pretty gefty and the other looks to be about 12ga with an in-line 20amp fuse. I am guessing the smaller one is the brakes. As I see it, there are 3 sources of power charging the battery:

1. The TV
2. The solar controller
3. The trailer's power center (aka converter)

How are these 3 coming together in one wire set at the battery without fighting each other?

Do I simply intercept the positive wire going to the battery and detour it through the dc-dc?