Where to put the solar controller?

[EllPea in CA]

Originally Posted by John in Santa Cruz

if the meter doesn't involve a shunt on the negative terminal, it can't monitor the actual power in and out of the battery. There are plenty of alternate shunt monitors, this one is $75 and doesn't have bluetooth, but tracks battery capacity nicely.
https://www.amazon.com/Renogy-500A-B.../dp/B07RP5B5P7

I know theres one that several fiberglass folks have used that was inexpensive and does have bluetooth but I don't know offhand what brand it was.

Question after sleep and a coffee... is the purpose of the shunt to monitor use, i.e. tracking when the refer is on, etc. I'm not sure I need that, really. I would just like an item (installed on a cool panel) that lets me check the battery health. Do I really need a "shunt"?

[Jon Vermilye]

Originally Posted by EllPea in CA

Question after sleep and a coffee... is the purpose of the shunt to monitor use, i.e. tracking when the refer is on, etc. I'm not sure I need that, really. I would just like an item (installed on a cool panel) that lets me check the battery health. Do I really need a "shunt"?

The less accurate but often used method of determining battery health is with a volt meter. Done properly, it is useful, but the conditions under which accurate results can be obtained are a bit complex.


A shunt is it is a device that tracks current going through it. If connected to an amp meter, it tells you the current in either direction. A battery monitor uses a shunt and combines the current in either direction with the voltage and time and tracks it. If the parameters are properly set, it provides an accurate record of the amp hours going in & out of the battery. This is a much more accurate way to keep track of the state of the battery than a simple voltage measurement, although it does require proper configuration to provide accurate results.

While a shunt is the most often used method of measuring current, and involves wiring it in series with the negative battery lead, there are Hall Effect current measuring devices that do the same by clamping around the negative battery wire. None of the major battery monitor manufacturers use Hall Effect sensors but some of the inexpensive versions do.

[John in Santa Cruz]

hall sensors aren't very accurate. my old ham radio friend calls them 'amp guessers'. a shunt is very accurate for both small and large currents.

yes, you do need to configure a shunt based battery monitor. typically, you tell it whether you have a lead acid or a lithium iron phosphate battery, and how many amp*hours that battery is, then you fully charge the battery and 'reset' or 'synchronize' the monitor., and boom, its good to go. this only has to be done once unless something major happens (like, a new battery being installed).

[Glenn Baglo]

If you run out of power, all you have to do is tell yourself that you're tenting.

[computerspook]

35 watts does not sound very big, so probably you can put it where is convient. Near the battery is great.

If you are doing a charge controller for something larger, make sure you consider the amount of heat it generates when locating it.

[John in Santa Cruz]

FWIW, I'm running a Victron SmartSolar 100/30 MPPT on a 360W panel and it doesn't get that warm, but its mounted vertically with plenty of airflow possibilities along its heatsink. It regularly sees 36V @ 10 A Solar input, and outputs 13.8-14.4V at 25A or so when the batteries aren't already fully charged.

[Glenn Baglo]

Originally Posted by computerspook

35 watts does not sound very big, so probably you can put it where is convient. Near the battery is great.

I run two 40-watt solar panels to a 7 watt controller without issues. It's about the size of a pack of smokes.

[computerspook]

Originally Posted by John in Santa Cruz

FWIW, I'm running a Victron SmartSolar 100/30 MPPT on a 360W panel and it doesn't get that warm, but its mounted vertically with plenty of airflow possibilities along its heatsink. It regularly sees 36V @ 10 A Solar input, and outputs 13.8-14.4V at 25A or so when the batteries aren't already fully charged.

I can't see this as being a problem as long as the area is not small and sealed. I have seen some of these things be a problem if the area is sealed. Heat sink kind of says it all. Anything with a heat sink at least expects some level of air flow.

[John in Santa Cruz]

Originally Posted by Glenn Baglo

I run two 40-watt solar panels to a 7 watt controller without issues. It's about the size of a pack of smokes.

a 7 watt solar controller?? say huh? maybe 7 amp. 2 40W panels would need at least a 80 watt controller, 100W controller would have a better margin.

[Glenn Baglo]

Originally Posted by John in Santa Cruz

a 7 watt solar controller?? say huh? maybe 7 amp. 2 40W panels would need at least a 80 watt controller, 100W controller would have a better margin.

Watt are you saying?
Yup. 7 amps.

[John in Santa Cruz]

Originally Posted by Glenn Baglo

Watt are you saying?
Yup. 7 amps.

heh. and yeah, a 7 amp solar controller is about 90-100 watts. which is a perfect size for 80 watts of solar juice.

[Markz]

I used this shunt. I love the performance, size and price. Plus it works with Lipo batteries.

[EllPea in CA]

John, you will be happy to know your recommendation paid off. I was not sold on the Bluetooth connection... would be happy with something much more old school. But I got PowerWerx salesman by phone to order a few things, and some $ later, now have almost everything coming.

I thought it would just be simpler to have the Victron thing, which he advised would also advise me of the battery health. I did NOT know that the manual for said item would be 60+ pages long!

After just being bullied by Microsoft to download Win 11 and discovering that office computer can no longer connect to the internet (and 3 wasted hours later fixing the mess), I'm feeling a bit trepidatious about the new gizmo coming.

Also, I was planning on having handyman build connections, but have been subsequently sold everything ready-made. Well handyman will have fewer hours to bill me, I guess.

So possible progress being made, and I do like the convenience of all wiring handled by solid connections. So, after HM works here on the weekend, there should be more progress to report. Will carry on smartly... good news is it's not as hoot here today as it has been!

Originally Posted by John in Santa Cruz

best place to get andersen powerpole stuff is PowerWerx. A lot of whats sold on Amazon is chinese counterfiet, almost works but doesn't quite fit together right.

they are sold as discrete pieces, usually in a box or bag of enough to make like 20 or so connectors. black shells, red shells, and crimp on pins. You do need to make sure to assemble them in the proper relation so the positive is always on the correct side.



as far as exterior use goes, when I did this on my Casita, I stored the PP30 connector on the end of its wire in the battery 'cave', and just slipped it out through the air vent slats when I needed it.

Powerwerx does sell a PP30 in a panel mount, installs into a 1-1/8" hole and has a rubber weather tight cover.
https://powerwerx.com/panelpole-pane...e-black-single

I like to use Marine duplex wire for stuff like this, available in AWG 12, AWG 10, and other gauges. for example, 50 feet of AWG 12.
https://www.amazon.com/gp/product/B00MI5EOGG
(this is proper made in USA tinned pure fine strand copper cable that is true to gauge...
a lot of off brand wire sold on Amazon has funky gauges, where '12' is more like 14).