Do I need battery monitor?

[Shurik]

Hello folks,

Today we have one 110w solar panel (and one group 27 flooded battery). I know it’s not ideal, but I don’t have budget to buy lithium battery and usually we are not staying without shore power more than two days.

Unfortunately it’s not enough for us, so I would like to add more solar panels.

First I would like to understand our battery usage.

Can I use solar charge controller as a battery monitor (like AiLi Battery Monitor)? If so, is there any specific model/type I should look for?

Thanks!

[hclarkx]

This is a complicated question (or the answer is complicated). You could get away with a simple voltmeter if you understand the characteristics of lead acid batteries or are interested in learning those characteristics.

Something like the AiLi six-in-1 would be the next step up from a voltmeter in that it reads both voltage and current and can track Watt-hour usage as well. This would be more effective, but would still require some understanding of lead-acid battery characteristics (like the amount of charging needing to be greater than the amount of discharging).

Does your solar controller by any chance have "load terminals" and will your loads be within the capability of those load terminals? If so, and you have a handle on how energy moves between the solar charge controller and the battery and load, you might get away with just the solar controller.

[nvs4602]

You will need a shunt type battery monitor like the AiLi you can order one from AliExpress for $10 less if you don't mind waiting about 3weeks to get it.

https://a.aliexpress.com/_mt88q6S

This way you can see the both charge and draw current.

[Tomahawk]

I am sure a lot of people will disagree with this. I would say to get a decent mppt charge controller and expand your battery bank by at least one more, and add 200 to 300 more watts of Solar. More if you are mounting flat on roof.

Adding monitoring does nothing to reduce your usage or increase your capacity. It just tells you your battery is dying.
My wife and I are without shore power for 3 to 6 days at a time. I have a group 29 and group 24 FLA wired in parallel and connected to 270W of Solar. That is enough for us. We can't run AC or the microwave or watch 5 hours of TV. We can run lights, heater, water pump, charge tooth brush, charge phones, and charge a laptop. I watch the battery voltage to understand about where I am at. You can estimate your power usage with a spreadsheet or ledger. Determine what you and for how long. Power = voltage x current. Let's say I want to charge my phone and it takes 45 minutes on 2.1 amp 5 volt charger. 45 minutes is .75 hour. Then .75 x 2.1 x 5 = 7.5 watt hours. In terms of battery capacity I can convert that to amp hours or convert the battery capacity to watt hour. Your group 27 about 70 usable amp hours or 70 x 12 = 840 watt hours. Charging the phone uses about 1%. You can look at every item in your rv that way. Some things like inverters use power even when they are not being used.

[Shurik]

I’m using very basic kit from Costco: https://www.costco.ca/coleman-120-w-...100704057.html

I don’t think I have “load terminals"…

As Tomahawk suggested, I might install some 30A-40A controller, add second panel and see how it goes. I saw some controllers show charging info and status of the battery as well.

Thank you guys!

[Mark_K5LXP]

Have your cake and eat it too. There are a few modestly priced shunt battery monitors (<$50) that will tell you Ah in and out. No reason you can't afford one of those and some form of system expansion such as additional battery and panel capacity. It's my guess that even with a single group 27 and some solar input you should easily be able to go 2 days unless there's a compressor fridge in the mix.

Mark B.
Albuquerque, NM

[TravelSolo]

Get the shunt/monitor first. If you don't know how much power you are using how you camp. Not knowing could mean you don't buy enough upgrades later or buy too much. Both of those could end up wasting your money.

You can get advice from others about what they have/need based on how they camp or what comforts they like, but no one will do things or need things exactly like you do.

[96 Wideglide]

I think I would invest in more battery capacity, before more solar.

Starting batteries, really aren't that good as house batteries!

[Shurik]

Thanks!
50A battery monitor will be enough or should I go with 100A version?

I thought to go with something like that: https://www.amazon.ca/dp/B07DW3T7K5/...lig_dp_it&th=1

At this point I don’t see I will have more than four 110/110 watt solar panels on the roof.

[TravelSolo]

Originally Posted by Shurik

Thanks!
50A battery monitor will be enough or should I go with 100A version?

I thought to go with something like that: https://www.amazon.ca/dp/B07DW3T7K5/...lig_dp_it&th=1

At this point I don’t see I will have more than four 110/110 watt solar panels on the roof.

Kind of up to you and where you think you will end up in terms of electrical upgrades. I wouldn't go lower than the 100A one as that will allow some room for some upgrades over time

[SJ-Chris]

Originally Posted by Shurik

Hello folks,

Today we have one 110w solar panel (and one group 27 flooded battery). I know it’s not ideal, but I don’t have budget to buy lithium battery and usually we are not staying without shore power more than two days.

Unfortunately it’s not enough for us, so I would like to add more solar panels.

First I would like to understand our battery usage.

Can I use solar charge controller as a battery monitor (like AiLi Battery Monitor)? If so, is there any specific model/type I should look for?

Thanks!

My first question/thought would be: "Is your battery good? Or is it old and failing?" If it is a bad battery, no amount of solar is going to give you a solution.


My next question is: "Do you have a generator for backup charging if your battery gets low?" If you do, and you need to save money (as you mentioned) you can run your generator for 2-3hrs in the morning to give your battery a great amount of charge, and then use your 100w-200w to complete the charging throughout the day.



If you want to add more solar, look for a compatible (same approximate output voltage) USED solar panel and hook them up in parallel to your existing panel. I've found 100w panels for as low as $25 each (tested and working) on craigslist and/or FB Marketplace. Then all you need are Y-cables to connect them in parallel. It is quite likely that your existing controller can handle at least an extra 100w if not 200w. You could probably add another 100w for less than $60.



You absolutely don't need Lithium if you mostly plug in while camping and you only go 1-2 days without power.


Also, yes having a battery monitor makes life much easier as you will know what your approximate state of charge is always. It will also help highlight which of your items take up the most battery power and you will likely adjust (reduce) your usage because of it. The inexpensive Aili monitor for <$50 is well worth it.


Good luck!
Chris

[Shurik]

Originally Posted by SJ-Chris

My first question/thought would be: "Is your battery good? Or is it old and failing?" If it is a bad battery, no amount of solar is going to give you a solution.


My next question is: "Do you have a generator for backup charging if your battery gets low?" If you do, and you need to save money (as you mentioned) you can run your generator for 2-3hrs in the morning to give your battery a great amount of charge, and then use your 100w-200w to complete the charging throughout the day.



If you want to add more solar, look for a compatible (same approximate output voltage) USED solar panel and hook them up in parallel to your existing panel. I've found 100w panels for as low as $25 each (tested and working) on craigslist and/or FB Marketplace. Then all you need are Y-cables to connect them in parallel. It is quite likely that your existing controller can handle at least an extra 100w if not 200w. You could probably add another 100w for less than $60.



You absolutely don't need Lithium if you mostly plug in while camping and you only go 1-2 days without power.


Also, yes having a battery monitor makes life much easier as you will know what your approximate state of charge is always. It will also help highlight which of your items take up the most battery power and you will likely adjust (reduce) your usage because of it. The inexpensive Aili monitor for <$50 is well worth it.


Good luck!
Chris

Thanks Chris!

Yes, it’s fairly new battery, got it two years ago.

No, I don’t have a generator. I thought about it, but the starting price for inverter generator is about $700. Besides that, space/weight/regulations etc. I thought I can install four panels for that price.

Used it’s a good idea

Yea, I decided to go with Aili battery monitor, not sure if I should get 100A or 350A..

BTW, do you know if I can install the shunt in the battery box? It’s not weather proof.

[bigb56]

Originally Posted by Tomahawk

I am sure a lot of people will disagree with this. I would say to get a decent mppt charge controller and expand your battery bank by at least one more, and add 200 to 300 more watts of Solar. More if you are mounting flat on roof.

Adding monitoring does nothing to reduce your usage or increase your capacity. It just tells you your battery is dying.

The issue I see with this is that the OP is using FLA, which have a very shallow discharge floor before permanent damage occurs. Without knowing how deeply he is discharging the FLA it would be easy to allow too deep of a discharge and ruin the FLA in short order.

[Tomahawk]

Originally Posted by bigb56

The issue I see with this is that the OP is using FLA, which have a very shallow discharge floor before permanent damage occurs. Without knowing how deeply he is discharging the FLA it would be easy to allow too deep of a discharge and ruin the FLA in short order.

I hear what you are saying. I also use FLA (3+ years) and just use voltage to monitor the depth of discharge. It works for me. I use a table with temperature compensation to monitor the SOC. A couple more comments. I used to check constantly, now I only check in the evening to see if the voltage is back up where belongs. If the day has been really overcast or smokey, I might run the generator for a bit to get where I want to be. I have several battery manufacture test reports on depth of discharge versus cycle life. It is pretty clear if you go below 20% SOC you damage the battery quickly. Above that, the data is much less compelling. If you integrate the area under the curve, total amp hours over the life of the battery, it comes out pretty close regardless of the depth of discharge. Made up example, if I have one battery and take down to 40% SOC it lasts me one year, if I have two and only go to 70% (same power out batteries) they will last a little more than twice as long. There are downsides to one like more frequent replacement and lower margin for error. There are downsides to two, like more initial expense and weight. Twin boat (I think) pointed out the data to me,and being an engineer, I ran off and looked at it and did some calcs. Not looking to argue or debate with anyone. Just giving my experience and opinion. Seems like the OP bought the shunt. I have one last comment about the shunt, my understanding is it tells you current in and current out. It doesn't tell you the condition of the battery or any self discharging internal to the battery. I think that means it doesn't help you if the battery is taking a crap.