Adding Solar to Sprinter RV

[Naruto]

The coach (WB Navion) is equipped with: (2 * 100) Zamp panels on a 30A PWM Controller, (2 * 125 Ah,) Lithium Batteries. and a Zantrex 2KW Inverter/Charger.

So here's my plan:
1) Connect the (2 *100) Zamp panels in Series and feed them to a Victron MPPT 100/20 Controller.
2) Add (2 * 210) Newpowa panels (Voc=39.6V, Imp=6.24A) and feed them to a Victron MPPT 100/50 Controller.
Did not want to mix panels, so opted for separate Controllers... Please ignore the "extra" stuff: Lynx Distributor, Smart-Shunt, Cerbo GX, and GX Display/Touch.
Question: Is 620W of Solar overkill for this system?
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[SunEagle]

Having 2 CC's may cause them to fight each other trying to charge the same battery.

But if they do work together then 50 amps of charging into a 250Ah battery system may be too high.

[chrisski]

I have three Victron SCCs charging my batteries. They network together through a virtual network. I don’t really know what that does because there’s not a lot of documentation. As I watch the charging stats on the Bluetooth App, all three are at the same state.

Check the stats on the battery. I have a small lithium battery bank that is rated to charge at 1C, the 25 ah Topband cells, and I am charging these at 10 amps, or about .3C. I don’t have longevity stats on this because I just built this and its an emergency backup generator, only 300 watt inverter, but I’ve used it for hours on end with the panels pushing 220 watts, about 9 amps, for that amount of time.

I’m installing two banks of 280 ah eve cells in my RV. So its a 560 ah battery pack, and the max charging I think I’ll see is 100 amps.

The other thing to check on the battery stats is the max discharge rate for the lithium BMS. Some BMS or batteries may be limited to .5C, and in that case would not push enough amps to power the inverter. Even if it is rated at 1C, those battery packs may not last long enough or you may be underpowered on the solar panels. A good power audit will tell you.

THe SCCs are extremely overpowered for the panels you have, unless you plan on future expansion, which is a great idea. THe 100/50 is good for 720 watts 12 volt or 1440 watts 24 volt. The 100/20 I can’t remember the stats, but a 75/15 would work. None of those SCCs will upgrade to 48 volts at a future date. If you’ll never upgrade to 48 volts that’s a non-factor. I may have went to 48 volts with the 12 to 24 volt upgrade I’m working on, but that meant three new SCCs.

For reference, on 12 volts, my microwave pulls 155 amps. My 500 watt coffee maker pulls 55 amps. My LED lights pull 1 amp or less.

Also, the Cerbex is a nice to have thing, but unless its for remote over the internet monitoring this cab be added later. THe cost is looking though multiple Bluetooth apps to get the data.

[Ampster]

.......

But if they do work together then 50 amps of charging into a 250Ah battery system may be too high.

50 Amps into a 250 Amphour battery is .2C which is way below the acceptable rate for most Lithium chemistries. Are you thinking about charging rates for Pb?

[SunEagle]

50 Amps into a 250 Amphour battery is .2C which is way below the acceptable rate for most Lithium chemistries. Are you thinking about charging rates for Pb?

While it is way too fast for Pb I still thought it a little fast for even LiFe chemistry. I guess I am always learning.

[Ampster]

While it is way too fast for Pb I still thought it a little fast for even LiFe chemistry. I guess I am always learning.

It is better to be safe. Some EVs can charge at 10C briefly before temperature rise causes the BMS to throttle back the DC charging. At home it is not practical to charge at that rate. The multitude of LIPO fires among RC hobbyists is probably a result of charging at high C rates.

[SunEagle]

It is better to be safe. Some EVs can charge at 10C briefly before temperature rise causes the BMS to throttle back the DC charging. At home it is not practical to charge at that rate. The multitude of LIPO fires among RC hobbyists is probably a result of charging at high C rates.

I can attest to LiPo's going up in smoke. Not mine but some friends. I still have a few RC planes and batteries around.

[chrisski]

I’m doing a lithium upgrade right now and what surprised me was the BMS shuts the batteries down at a user selectable amperage output, which should not exceed the cell rating I make the batteries out which is .5C. So the lithium’s can provide much more amperage continuously. Where the Pb batteries put out more energy is for those trying to run a microwave off a couple of 100 ah batteries. Those who had Pb before found that the batteries powered the microwave, but after a direct replacement for Lithium batteries, they found their microwave would not work.

Whether or not these people, usually van builds, should be running a microwave on 200 ah of batteries on a 12 volt systemis a different discussion, but at least with the lithium BMS there are some limits that cab be put on.

[Ampster]

.......... Those who had Pb before found that the batteries powered the microwave, but after a direct replacement for Lithium batteries, they found their microwave would not work.
.......

Hopefully they figured out that they could change the discharge limit on their BMS to a level that could provide enough Amps run the microwave. Lithium batteries of the same Amphour capacity as Pb should be more than capable to run the Sam microwave as the Pb batteries ran.

[chrisski]

Hopefully they figured out that they could change the discharge limit on their BMS to a level that could provide enough Amps run the microwave. Lithium batteries of the same Amphour capacity as Pb should be more than capable to run the Sam microwave as the Pb batteries ran.

As I look at the Battleborn spec sheets, two drop in will work. Will supply 200 amps total. Enough to power the 155 amp microwave.

I guess the posts I’ve seen must have come from home made batteries with BMSs less than 1C, or other types of lithium batteries which are not spec’d for a 1C discharge.

[Ampster]

......
I guess the posts I’ve seen must have come from home made batteries with BMSs less than 1C, or other types of lithium batteries which are not spec’d for a 1C discharge.

The discharge rate of most BMSs is usually specified in Amps. I think what you are saying in the posts you referred to was that they used a BMS with a current setting below what the components drew in Amps. For short durations most Lithium batteries can discharge at greater than 1C. As with anything DIY, it is simply a matter of making sure the use case matches the specs of the components. It is up to the DIYer to configure components appropriately. For those that can't figure it out, there are always high priced solutions like Battlborn.