Getting started with solar and lithium

[kb0zke]

Our new Reflection came with a solar panel on the roof. There seems to be some confusion over the exact capacity of that panel, but since the sun doesn't always shine on it anyway, I'm not sure that the difference is really all that important. Apparently Reflections don't come with batteries as standard, so we paid $1000 each for two lithium batteries of 105 AH each. The converter may or may not be up to charging them fully.

Questions:
1. The meter on the wall shows 100% charged and 13.32 volts. Is that right?
2. We'd like to visit Quartzsite next winter, and then head up to Alaska during the summer. I suspect that we will need more solar capacity. Who is the go-to person for installing solar panels?
3. I also suspect that I'll need more battery capacity. Can I add more batteries? If so, where should they go? From what I'm reading it sounds like I ought to buy more batteries identical to the ones I have, or else replace these two with two with more capacity. True?
4. What else should I know that I don't know I need to know?

[huntindog]

Our new Reflection came with a solar panel on the roof. There seems to be some confusion over the exact capacity of that panel, but since the sun doesn't always shine on it anyway, I'm not sure that the difference is really all that important. Apparently Reflections don't come with batteries as standard, so we paid $1000 each for two lithium batteries of 105 AH each. The converter may or may not be up to charging them fully.

Questions:
1. The meter on the wall shows 100% charged and 13.32 volts. Is that right?
2. We'd like to visit Quartzsite next winter, and then head up to Alaska during the summer. I suspect that we will need more solar capacity. Who is the go-to person for installing solar panels?
3. I also suspect that I'll need more battery capacity. Can I add more batteries? If so, where should they go? From what I'm reading it sounds like I ought to buy more batteries identical to the ones I have, or else replace these two with two with more capacity. True?
4. What else should I know that I don't know I need to know?

The meter on the wall is next to useless.
Get a shunt based battery monitor fo an accurate reading

[Redapple63]

The meter on the wall is next to useless.
Get a shunt based battery monitor fo an accurate reading

That’s correct, battery voltage is a very “course” and inaccurate means of measuring state of charge.

A shunt it a device that measures everything going in and out of the battery. Two of the most popular ones are the Victron BMV-712 and the Victron Smart Shunt. They attach to the negative reroof you battery before any loads. Both I believe are Bluetooth. One has a physical monitor and the other uses the Victron app on your phone. These are pretty much at the top tier.

There are other battery monitors and shunts far less expensive that do the same job. I prefer the Victron components, but the others are I am sure very reasonably accurate and will do the job just as well.

Renogy: https://a.co/d/6K7BZFs

Victron Smart Shunt https://a.co/d/eGMEtDF

Bill

[Soundsailor]

Our new Reflection came with a solar panel on the roof. There seems to be some confusion over the exact capacity of that panel, but since the sun doesn't always shine on it anyway, I'm not sure that the difference is really all that important. Apparently Reflections don't come with batteries as standard, so we paid $1000 each for two lithium batteries of 105 AH each. The converter may or may not be up to charging them fully.

Questions:
1. The meter on the wall shows 100% charged and 13.32 volts. Is that right?
2. We'd like to visit Quartzsite next winter, and then head up to Alaska during the summer. I suspect that we will need more solar capacity. Who is the go-to person for installing solar panels?
3. I also suspect that I'll need more battery capacity. Can I add more batteries? If so, where should they go? From what I'm reading it sounds like I ought to buy more batteries identical to the ones I have, or else replace these two with two with more capacity. True?
4. What else should I know that I don't know I need to know?

There are a lot of good threads on solar and batteries on the forum, the search bar is your friend.

1) The wall-mounted meter is not going to help much with lithium batteries, as others have said, get one with a shunt, much more useful.
2) I suppose that varies based on where you are. I went the DIY route, that way if anything comes up I feel like I know how to fix it. There are a lot of threads here about how people have installed their own systems which you could follow. Also, let us know if you need help.
3) Depending on your energy needs, more batteries can help. Ideally, you want the batteries as close to the place where you'll be using the power as possible to minimize loss due to cable length. And yes, you want the batteries to be the same.
4) I've found the Will Prowse videos on YouTube useful, he also has a book that covers all the basics.

Let us know how you make out.

[kb0zke]

Bill, is this the one you are referring to?

https://www.amazon.com/Victron-BMV-7...23&sr=8-5&th=1

This looks like it is a direct replacement for the gauge I now have. I think I'm going to have to find the actual wires from the batteries and see how they are connected, since it looks like the shunt connects between the negative post of the battery bank and ground. Correct?

[Redapple63]

Bill, is this the one you are referring to?

https://www.amazon.com/Victron-BMV-7...23&sr=8-5&th=1

This looks like it is a direct replacement for the gauge I now have. I think I'm going to have to find the actual wires from the batteries and see how they are connected, since it looks like the shunt connects between the negative post of the battery bank and ground. Correct?

Yes same BMV-712.

Yes, between negative post of the battery and system ground. Stock, negative battery post goes straight to frame ground.

In my system, negative pot of battery to the shunt to the negative bus bar. The other negative wires of the rv loads also go to the same bus bar. One main ground wire goes from bus bar to frame ground.

Bill

[xrated]

Voltage readings are impossible to use for battery capacities on LiFePO (LFP) type batteries....you need a shunt to see the actual State Of Charge (SOC) with the LFP. Here is an example of some battery voltages with LFP. At 13.00 volts, your battery SOC is right at 30% remaining. At 13.30 volts, you are right at 90% SOC. 3/10s of a volt difference, but SOC goes from 30% to 90%. Then when you throw in an error in the meter's accuracy, it could be even more inaccurate....so Yes, a shunt like the ones mentioned above will give you a lot better idea of the SOC.

And when installing a shunt, it is very important to make sure that ALL the negative wires are downstream of the connection on the shunt. In other words, a wire/cable directly from the battery negative post to the shunt, and then any/all of the neg wires/cables from the shunt to wherever they go. Most folks will install a negative buss bar for the purpose of having a terminal point for the other battery neg. wires and being fed from the ONE wire/cable from the battery neg post to the shunt. Hope this helps.

[kb0zke]

The weather was pretty nice today, so I decided to open the battery boxes and see what I could see there. I found two lithium batteries (which is what I paid for). One battery has only one red and one black cable connecting it to the other battery. The second battery has three red and three black cables. One of each is, of course, from the first battery.

Question: when I get this, should I disconnect all three black cables from the second battery and reconnect them to the one end of the shunt, with the other end connected to the second battery? Or would I leave the negative cable from the first battery connected where it is, and only connect the other two cables to the other side of the shunt?

My guess is that the instructions will tell me how to connect, but at the price of what's involved (not to mention that we live in this trailer) I don't want to destroy things.

[Redapple63]

The weather was pretty nice today, so I decided to open the battery boxes and see what I could see there. I found two lithium batteries (which is what I paid for). One battery has only one red and one black cable connecting it to the other battery. The second battery has three red and three black cables. One of each is, of course, from the first battery.

Question: when I get this, should I disconnect all three black cables from the second battery and reconnect them to the one end of the shunt, with the other end connected to the second battery? Or would I leave the negative cable from the first battery connected where it is, and only connect the other two cables to the other side of the shunt?

My guess is that the instructions will tell me how to connect, but at the price of what's involved (not to mention that we live in this trailer) I don't want to destroy things.

If you could post a picture that would be very helpful. The shunt is going to be installed on the negative cable that goes to the chassis ground. There should be only one cable. Disconnect the one cable that is going to the chassis ground at the battery and connect it to the shunt. You will then need a small cable to go between the shunt and the batteries.

Now, the reason for the pictures is to see how they paralleled your batteries.

There should be one cable going between each post pos-pos and neg-neg. Then from one battery connect the positive side to the rv load and from the other battery connect the negative to the chassis ground. By connecting this way you have a much better chance of getting equal discharge/charge between the two batteries.

The shunt should go between the battery neg and chassis ground.

See attached image


Bill

[MaddyBob]

Jumping in agreeing with what has been said thus far.

At the risk of stating things you already know. It would be best if you had one cable coming from the negative terminal of the first battery and then one cable coming from the negative terminal of the 2nd battery to the shunt. You should have a cable coming from the positive terminal of the 2nd battery to the positive terminal of the first battery. Then the positive terminal of the first battery feeds to the coach. It is important not to have the cables feeding the coach coming from the same battery.

Another cause for inadequate charging could be the size of the cables between the batteries and from the converter to the battery, as well as the length of the cable run. There are many good calculators and tables on voltage drop available with a quick internet search.

I used AM Solar as my consultant for our solar system. We boondock a lot, so we needed a biggish system, plus I like my electronics. They helped with the design and answered many questions. Their shipping was great $15/order. (That was for everything, including 8 solar panels and 3 batteries.)