Can you have too much solar power for your battery?

[Hedges]

If battery can get hot and cold, I think you're already pushing a charge rate that can accelerate battery degradation.
But if camper means you cycle only a few dozen times per year not a few hundred, maybe not a big deal.
Still, I'd rather reduce charge rate to 0.15C

What is your charger or inverter/charger equipment?

 

[slayer666]

If battery can get hot and cold, I think you're already pushing a charge rate that can accelerate battery degradation.
But if camper means you cycle only a few dozen times per year not a few hundred, maybe not a big deal.
Still, I'd rather reduce charge rate to 0.15C

What is your charger or inverter/charger equipment?

Right now I'm running a 60 amp Y&H mppt on the 400 watts of panels on my camper. The only reason I am is because the 35 amp mppt doesn't seem to work right and I'm talking to the seller to see what they will do about it. The 60A does a good job, though. It seems to work just fine. As a matter of fact, today I was a little shocked to see that it was telling me it was actually pulling in about 422 Watts ! My inverter is just a little 300w pure sine wave but it's fine for my needs. I run a swamp cooler on the inverter and the little swamp cooler only pulls 100 watts. I'll get a picture off of the internet of the scc since I haven't taken one. Might take me a few minutes but, I will edit this post to add the picture.

 

[HRTKD]

I leave my inverter running except in the summer. I don't have enough active ventilation/cooling to handle the heat the inverter can create in the summer. This is in an RV that sits at the RV storage lot when not in use.

 

[ksmithaz1]

I'm pretty sure, if you have a reasonable bms, you will not degrade your battery leaving it, or chargng it to 100%. Even non po4. The tesla battery data seems to indicate the #1 factor for degradation is age. Other factors/abuse as outlined above, too high charge rates for the given temps. Over discharging.

 

[Hedges]

Because it is a stand-alone MPPT SCC, you won't be able to tell it 15A for the battery, only supply more if needed by inverter.
So have to live with what it can do.

If possible tilt some panels East, tilt others (in parallel not in series with the first group) to the West. For slower, longer charge.

Try to keep battery at a comfortable temperature, shut down SCC if its current is higher than what LiFePO4 tolerates per data sheet at current temperature.

 

[Flunkyboi]

I stay below 0.2c , charge or discharge.

As a noob, i keep hearing this .5c, .2c, 1c, etc, but have zero clue as to what "c" means. Can someone explain this in basic terms?

 

[slayer666]

As a noob, i keep hearing this .5c, .2c, 1c, etc, but have zero clue as to what "c" means. Can someone explain this in basic terms?

Charge rate. Amperage your battery can tolerate while charging.

 

[slayer666]

.5c is half your battery's amp hour rating. 100ah battery? 50 amps max charge current.

 

[timselectric]

As a noob, i keep hearing this .5c, .2c, 1c, etc, but have zero clue as to what "c" means. Can someone explain this in basic terms?

It's the charging or discharging rate. Based on the percentage of battery capacity.
.2c is 20%
.5c is 50%
1c is 100%

For a 100ah battery, 1c would be 100a.

 

[CaySol]

So my max discharge is .36C and max rated charge is .3C. Is this too high?

 

[Flunkyboi]

It's the charging or discharging rate. Based on the percentage of battery capacity.
.2c is 20%
.5c is 50%
1c is 100%

For a 100ah battery, 1c would be 100a.

Bloody well...thank you for that explanation! I knew it was something simple, but it is so simple that folks gloss over it.

 

[Q-Dog]

So my max discharge is .36C and max rated charge is .3C. Is this too high?

Your battery should have a recommended charge rate and a maximum charge rate. You should try to do most of your charging at the recommended rate.

 

[timselectric]

So my max discharge is .36C and max rated charge is .3C. Is this too high?

It's pushing the cells a little harder than I would like.
That's going from full to empty in less than 3 hours.
And almost the same, in the opposite direction.

 

[Flunkyboi]

.5c is half your battery's amp hour rating. 100ah battery? 50 amps max charge current.

I just discovered i can charge my little bank at .4c. Now I can talk like the real solar nerd I'm striving to become.

 

[CaySol]

Your battery should have a recommended charge rate and a maximum charge rate. You should try to do most of your charging at the recommended rate.

It’s the eg4 wallmount indoor. Apparently the recommended range is .21c -.5C. I can’t get to .5 and shouldn’t be at my max for too long of durations discharge. Charging I will wait and see when I have my arrays up.

 

[Zwy]

I just discovered i can charge my little bank at .4c. Now I can talk like the real solar nerd I'm striving to become.

You should get more battery. With 140A running into my battery bank, it's not even .1C rate.

 

[sunsurfer]

Bloody well...thank you for that explanation! I knew it was something simple, but it is so simple that folks gloss over it.

Its something that allot of people miss when starting out. We really need a newbie sticky on this forum. So much knowledge but its spread out.

One of the challenges with building systems with LFP has been getting enough battery to handle the solar input. Its nice to have the overhead of lots of panels and inverter power but if your battery is getting over run, its a problem. Luckily, it's getting less of an issue with LFP prices dropping.

 

[timselectric]

One of the challenges with building systems with LFP has been getting enough battery to handle the solar input. Its nice to have the overhead of lots of panels and inverter power but if your battery is getting over run, its a problem.

Over run?
Problem?
I don't understand.

 

[sunsurfer]

Over run?
Problem?
I don't understand.

Lets say you have a 50a battery and 100a of DC out of your SCC. Its great for say running AC and such but if its just going to the battery, you just maxed out your charge rate.

 

[HRTKD]

Its something that allot of people miss when starting out. We really need a newbie sticky on this forum. So much knowledge but its spread out.

Thread 'Commonly used Forum Acronyms & Abbreviations'

Oct 16, 2019

Solar is befuddling enough! Why use acronyms? Well, we're lazy typists....

• xSyP - e.g., 2S2P, shorthand for how many cells in Series (S) and Parallel (P).
• A - Amperes or amps. A measure of current. See warning.
• AC - Air Conditioning, sometimes A/C.
• AC - Alternating Current, a waveform of varying voltage with steady frequency.
• AFAIK - As far as I know
• AGM - Absorbent glass mat, a type of lead acid battery.
• Ah - Amp Hours
• AHJ -...

• svetz
• Replies: 76
• Forum: Frequently Asked Questions

• 

 

[0truck0]

Haha sunshine eggo. I can appreciate your smartassness. However, this is in a camper and at night you wouldn't have much at all for loads. Maybe a couple hours of TV watching or something but it would never take the battery below 90 or so percent. How about if you view the question as hypothetical and just give me an answer? And, while I'd like to just stay on topic here, I must say one example. Alaska!

He ruined your thread with really bad wasteful inconsiderate humor, err nonhumor of complete waste of everyone's time who was so unfortunate to have read it and been sad and mad after. "Where do you get sun at night?" Really? You have to ash this? Buddy, the sun does not shine at night, that is why it is night, literally it has to do with the sun if we call it day or call it night. You dont get sun at night. Thanks for nothing and wasting my and everyones time. Leave the humor to someone slightly funny or better.

 

[Dagoth Ur Does Solar]

He ruined your thread with really bad wasteful inconsiderate humor, err nonhumor of complete waste of everyone's time who was so unfortunate to have read it and been sad and mad after. "Where do you get sun at night?" Really? You have to ash this? Buddy, the sun does not shine at night, that is why it is night, literally it has to do with the sun if we call it day or call it night. You dont get sun at night. Thanks for nothing and wasting my and everyones time. Leave the humor to someone slightly funny or better.

To be fair this is a question OP could easily search for- even probably the AI generated garbage on search engines nowadays.

It's pretty common knowledge that for lithium ion chemistries, it's not good to sit them at 100% state of charge constantly.

 

[CaliSunHarvester]

Lets say you have a 50a battery and 100a of DC out of your SCC. Its great for say running AC and such but if its just going to the battery, you just maxed out your charge rate.

Doesn't the BMS limit how much current it pulls? It certainly won't pull more than 1c, right?

That said, I have set up a rule in Solar Assistant to reduce the max charge current depending on how empty my batteries are.
(I have 800Ah capacity. So 80A = 0.1c)

 

[timselectric]

Lets say you have a 50a battery and 100a of DC out of your SCC. Its great for say running AC and such but if its just going to the battery, you just maxed out your charge rate.

I see what you are saying. If you have separate SCC's ,you can't adjust the charging, by itself. Only the total output. Yeah, that could be a problem if you have a large array and a small battery.
This is another benefit of an AIO. You can set the charging, independently from the maximum output of the solar production.

 

[sunsurfer]

I see what you are saying. If you have separate SCC's ,you can't adjust the charging, by itself. Only the total output. Yeah, that could be a problem if you have a large array and a small battery.
This is another benefit of an AIO. You can set the charging, independently from the maximum output of the solar production.

Yep, its all a trade off. I like being able to add a string if I want. There is probably a way to use the victron shunt to controller what the battery gets but most people on here are not at that level.