TantoTrailers
Well-known member
F-it...I went with the Victron cause I want the charging data (amps in) and the app history data.
Need the solar/power pros to weigh in
- Thread starter TantoTrailers
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shade
Well-known member
Installing A Battery Monitor - Marine How To
Battery Monitor Diagram This article features the older Victron BMV-602. The 602 has been replaced by the BMV-7oo series. Everything in this article is still relevant to the current series of BMV monitors. Purchasing recommended products from our affiliate partners.Helps keep content coming...
marinehowto.com
Making Your Battery Monitor More Accurate - Marine How To
Program The Ah Capacity This article features the older Victron BMV-602. The 602 has been replaced by the BMV-7oo series (700, 702 & 712). Everything in this article is still relevant to the current series of BMV-7xx battery monitors. WARNING: This article
marinehowto.com
Good stuff.
TantoTrailers
Well-known member
Thanks man! I will definitely be following those guidelines.
dwh
Tail-End Charlie
If you can confirm that solar and/or driving actually are putting out sufficient power to the battery...
And you can confirm that your loads actually are what you think they are...
That just leaves the battery.
It has a rating of 100ah...at "the 20 hour rate", which would be a 5a load. But due to the Peukert effect, if you double the load to 10a, you will get less than the 10 hours that you would logically expect. Conversely, cutting the load in half to 2.5a will get you more than 40 hours.
Because of that, batteries have various amp*hour ratings...@5hr rate, @10hr rate, @20hr rate are the most common, and @20hr is what most people go by.
Temperature also plays a role. Higher temps = less amp hours. So does sulfation. More sulfated plate area, less contact between plate and electrolyte = less amp hours.
Just bacause a battery tested out "good" doesn't mean much. It could be so heavily sulfated that the actual amp hour capacity is 30ah and still test out "good". It will also charge up to normal voltage (faster than it should of course) and otherwise look like it's working fine.
So you assume that battery is a 100ah battery, but until you do a capacity test, you don't know that for sure. You could have got a dud.
And a 100ah battery should have 100ah of usable capacity...with a 5a load and not too hot.
And you can confirm that your loads actually are what you think they are...
That just leaves the battery.
It has a rating of 100ah...at "the 20 hour rate", which would be a 5a load. But due to the Peukert effect, if you double the load to 10a, you will get less than the 10 hours that you would logically expect. Conversely, cutting the load in half to 2.5a will get you more than 40 hours.
Because of that, batteries have various amp*hour ratings...@5hr rate, @10hr rate, @20hr rate are the most common, and @20hr is what most people go by.
Temperature also plays a role. Higher temps = less amp hours. So does sulfation. More sulfated plate area, less contact between plate and electrolyte = less amp hours.
Just bacause a battery tested out "good" doesn't mean much. It could be so heavily sulfated that the actual amp hour capacity is 30ah and still test out "good". It will also charge up to normal voltage (faster than it should of course) and otherwise look like it's working fine.
So you assume that battery is a 100ah battery, but until you do a capacity test, you don't know that for sure. You could have got a dud.
And a 100ah battery should have 100ah of usable capacity...with a 5a load and not too hot.
TantoTrailers
Well-known member
I am not charging from the vehicle, solar only. I had my panels set up in the bed of the truck with 12# back to the MPPT. The shade varied as I drove.
The tester I have was recommended here by someone in the past:
Not sure if that can get me all the health data or not.
dwh
Tail-End Charlie
That's a good tester, but it has its limits. It reads voltage and resistance and guesses the rest.
Since it doesn't actually apply a load and run the battery dead, it doesn't know the actual amp hour capacity. Since it doesn't apply a dead short through a carbon pile, it doesn't actually know the cranking amps.
Still, measuring voltage and resistance can make a pretty good guess.
There are shunt-type battery monitors like the BMV (called amp counters). These slowly get less accurate over time and have to be periodically recalibrated.
There are also what are called "algorithmic" battery monitors like the SmartGuage. Algorithmic types measure voltage and resistance, but unlike the handheld you linked, keep track of data points and get more accurate over time.
Balmar recently came out with a new unit that combines shunt and algorithmic...
http://www.balmar.net/sg200-battery-monitor/
Since it doesn't actually apply a load and run the battery dead, it doesn't know the actual amp hour capacity. Since it doesn't apply a dead short through a carbon pile, it doesn't actually know the cranking amps.
Still, measuring voltage and resistance can make a pretty good guess.
There are shunt-type battery monitors like the BMV (called amp counters). These slowly get less accurate over time and have to be periodically recalibrated.
There are also what are called "algorithmic" battery monitors like the SmartGuage. Algorithmic types measure voltage and resistance, but unlike the handheld you linked, keep track of data points and get more accurate over time.
Balmar recently came out with a new unit that combines shunt and algorithmic...
http://www.balmar.net/sg200-battery-monitor/
dwh
Tail-End Charlie
The problem with amp counters (and that hand held tester), is that you have to tell it the amp hours.
So say you tell your BMV that the battery is 100ah. It does its calcs based on that. But as the battery ages and sulfates, maybe now it actually only has a 95ah capacity...but it still thinks it's a 100ah battery.
As time goes by, the "% Full" it's showing gets more and more out of touch with reality.
So with an amp counter, you have to periodically do a full capacity test to find out the actual capacity of the battery, then reprogram the amp counter with the correct amp hour number.
So say you tell your BMV that the battery is 100ah. It does its calcs based on that. But as the battery ages and sulfates, maybe now it actually only has a 95ah capacity...but it still thinks it's a 100ah battery.
As time goes by, the "% Full" it's showing gets more and more out of touch with reality.
So with an amp counter, you have to periodically do a full capacity test to find out the actual capacity of the battery, then reprogram the amp counter with the correct amp hour number.
luthj
Engineer In Residence
If you are using portable panels in a truck bed, you are not getting nearly the charge rate you think you are. Even a small amount of shading on one panel will drop its output by 50%. Panels in series (depending on bypass diodes etc) will both be brought down by the low panel.
You may consider swapping you panels to parallel if you are encountering lots of partial shading. You also need to verify you are getting a full charge. This can be done by looking at your voltage near the end of the day with the panels in the sun. You want to see ~14.4V at the batteries.
You can also add alternator charging, which may add noticable amp-hours of extra charging. Decent sized wiring is required though.
You may consider swapping you panels to parallel if you are encountering lots of partial shading. You also need to verify you are getting a full charge. This can be done by looking at your voltage near the end of the day with the panels in the sun. You want to see ~14.4V at the batteries.
You can also add alternator charging, which may add noticable amp-hours of extra charging. Decent sized wiring is required though.
dwh
Tail-End Charlie
And driving with the solar in the bed, variable shade...
My default assumption would be you got little if any usable battery charge from that.
Even a little shade can drastically reduce solar output.
Plus, MPPT controllers periodically "sweep" up and down the voltage range of the solar to find the operating voltage to get the most watts (Vmp), which changes through the day based on temps and solar angle...and shade.
Doing it the way you did...Vmp becomes a moving target that the MPPT might not be able to track accurately.
My default assumption would be you got little if any usable battery charge from that.
Even a little shade can drastically reduce solar output.
Plus, MPPT controllers periodically "sweep" up and down the voltage range of the solar to find the operating voltage to get the most watts (Vmp), which changes through the day based on temps and solar angle...and shade.
Doing it the way you did...Vmp becomes a moving target that the MPPT might not be able to track accurately.
shade
Well-known member
Solar charging is swell, but when there's abundant charging power a few feet away, I think it's wise to at least have alternator charging as an option. Even if the theoretical solar charging output is far above consumption, you never know when you'll be parked in the shade, get snow on the panels, decide that you really do need to run a microwave oven, etc.
shade
Well-known member
Disconnect all loads and let it run. 3.5A isn't much, but once it gets out of Bulk, it'll get the job done.
TantoTrailers
Well-known member
Man you guys are dumping some useful info on me!! Much appreciated and a lot to take in but I think I am slowly getting this more and more. I was hoping to avoid alternator or DC to DC charging but that may be a very good option (more questions about that maybe later). I unplugged everything with the battery still really low, the Renogy controller was showing 25%. I hooked up the battery tester and these are the results:
I then hooked up my chargers but no load and about 1 minute later the Genius charger was showing 100% full?
Renogy was showing 95% and then 100% a few seconds after this picture:
Are these normal readings while shore charging? No solar hooked up in the garage.
I then hooked up my chargers but no load and about 1 minute later the Genius charger was showing 100% full?
Renogy was showing 95% and then 100% a few seconds after this picture:
Are these normal readings while shore charging? No solar hooked up in the garage.
shade
Well-known member
That charger has a desulfation mode ("12V Repair"). If distilled water can be added to the battery, top it off before and after using it.