Can a solar charge controller act as a battery monitor?

[RKW]

Back in the day I installed a Link 10 battery monitor so I could know exactly what was going into and out of the battery bank while I was boondocking. Fast forward and I now have a new trailer and I'm in the process of moving mods from the old to the new. My new trailer will, eventually, have a solar system installed. Can the modern charge controllers today double as a battery monitor of sorts? If, at the least, the charge controller registered every amp hour sent to the battery from all sources, that would meet my biggest need. Do the new controllers do this?

Thanks

[RKW]

Thanks folks.

[Almot]

RKW wrote:
... I now have a new trailer and I'm in the process of moving mods from the old to the new.

Have missed this. Of course move that old monitor to new trailer, why asking...

When and if you get enough solar to keep batteries full on most days - a doable thing in New Mexico - then with a good controller display you won't have much use for battery monitor. Until then, you need some way to keep an eye on SOC. People don't usually buy controller before the panels.

With a substantial solar system a controller should still have a display for ease of adjusting the controller and checking some things sometimes that monitor might miss - built-in display is fine, doesn't have to be remote. Or a laptop connectivity if there is no display. In fact, I would discourage from getting a remote solar display when you already have a remote battery monitor. Too many toys in a small space of RV isn't always a good thing.

[Almot]

BFL13 wrote:
you cannot get the battery SOC from the AHs "in"

Nobody said you can. My battery SOC by the end of the day is Full, it's that simple :)... It is full because it is full after 6-7 hours floating. These data solar controller would supply, and this is enough, in this case.

If you can't get them to full most days and/or can't keep them in Float while running your afternoon loads, then solar controller is not enough.

[BFL13]

jrnymn7 wrote:
BFL, I wonder if that means the Trimetric is more accurate with higher charge rates than with lower? (because there is less heat generated at a lower rate)

Sort of. There is a discussion of that in the Trimetric's manual. They say once gassing gets really going above 80% SOC, they don't have a good handle on it, but also that isn't many of the total count from 50-100% Also that in the mid-SOCs it can be less than 4% for heat loss. So 4% is a number that works fairly well over-all.

[jrnymn7]

BFL, I wonder if that means the Trimetric is more accurate with higher charge rates than with lower? (because there is less heat generated at a lower rate). I mean, is there an optimal range the trimetric functions within, or would the difference be very minor?

[BFL13]

It doesn't matter if the solar is the only charging source.

The trouble is those AHs "in" are not all for the battery when you run loads with the solar "extra" once the batts accept less than what the solar can do, such as in the afternoon.

So you cannot get the battery SOC from the AHs "in"; you would think the batts are more full than they are.

Plus--the AHs "in" include some for heat loss. The Trimetric allows 4% for heat when showing the AH count on recharging. The solar controller would not have that built-in adjustment.

So that is two ways the AH count on the solar controller will be too high for the battery's SOC.

[Almot]

RKW - no.

Even most sophisticated solar controllers don't monitor ALL the input sources to battery. I've only heard of one "exception", sort of - Midnite Solar Kid 30A MPPT. They offer an optional battery monitoring add-on, but I think there are better 30A MPPT controllers out there (and there are also cheaper MPPT, if budget is your primary concern, and then of course there are cheaper yet PWM).

However, I've been lucky in not needing a battery monitor when off-grid. My controller display tells battery voltage, solar amps and amp-hours or watt-hours IN. It also tells the battery charge status and the history of charging by the end of the day, i.e. was Absorb or Float ever reached and for how long. Since it gets to Float by noon on most days, and very close to Float on those days when it doesn't, I don't care to monitor amp-hours OUT. I don't have other sources IN, and neither feel any need.

If you follow links suggested by Don Pianotuna, and considering your location, you should be able to get enough solar amp-hours without any other input sources. The only times when you will need a generator, will be when you run air conditioner, and that time can be reduced with 12V fans like FanTastic and others.

It looks like Xantrex have replaced Link 10 with Link Lite.

To me, Victron looks nicer than Xantrex or Trimetric. Single-battery version is $40 cheaper.

[MrWizard]

some solar controllers will tell you the battery voltage ?

but it won't take the place of a more sophisticated Power monitor

[msiminoff]

RKW wrote:
Can the modern charge controllers today double as a battery monitor of sorts? If, at the least, the charge controller registered every amp hour sent to the battery from all sources, that would meet my biggest need. Do the new controllers do this?

Hi RKW,
Bogart Engineering's TriMetric TM-2030 can do this when used in conjunction with their SC-2030 charge controller.
Here's a Quick Reference Guide that shows how the two interact.

Cheers,
-Mark

[time2roll]

RKW wrote:
If, at the least, the charge controller registered every amp hour sent to the battery from all sources, that would meet my biggest need. Do the new controllers do this?

Thanks

No, only solar production is measured by the controller.

Although you may find less need to monitor the battery with a well sized solar charging system. (220+ watts)

[BFL13]

Mostly, no. The solar monitor just has a shunt for the solar and not for the rest of the rig. It is nice to know the amps the solar is doing at any time, but the solar AH info is fairly useless.

The Trimetric has a shunt that sees everything including the solar. the solar monitor shunt( if any) is upstream from the Trimetric.

There is a new controller monitor (ISTR called the Kid?) which has the shunt arranged to subtract solar from "all" and you get the whole story--forget exact details.

So take the Link with you to the new rig.

Some solar controllers have a built in ammeter and display so you don't need a shunt etc. Tthat gives you what you want to know about how the solar is doing without having to pay for a solar monitor at all. The $35 Solar30 PWM has that and so does the $102 Eco-Worthy MPPT for instance. Works great.

[pianotuna]

Hi Ryan,

Yes, some controllers have sophisticated monitoring systems, including the ability to be tweaked using a computer.

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT. What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

One rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!

Solar Spread Sheet N8GS

For a nice explanation of solar, try this link:

Golden rules of solar