41 replies to this topic

[PaulT]

If you use either a Trimetric or Victron, you will have a more expensive but more capable instrument for managing your power system. There is a cheaper option for measuring power used by specific subsystems that could be useful. The Powerwerx wattmeter. https://powerwerx.co...tBoCWFIQAvD_BwE

This is more useful and easier to use if there are already Anderson Powerpoles installed on those power using devices that you want to know about.

Just another option.
Paul

Edited by PaulT, 14 December 2017 - 09:46 PM.

[billharr]

If you use either a Trimetric or Victron, you will have a more expensive but more capable instrument for managing your power system. There is a cheaper option for measuring power used by specific subsystems that could be useful. The Powerwerx wattmeter. https://powerwerx.co...tBoCWFIQAvD_BwE

This is more useful and easier to use if there are already Anderson Powerpoles installed on those power usung devices that you want to know about.

Just another option.
Paul

 

I agree the Trimetric and Victron are great but $$$.   Useful information can can be had for much less .  

 

Amazon link. $15.99

 

 

[abqbw]

Thanks Rando, Paul T, billharr. Good advice.

[Timothy McGowen]

Rando-My new 85L isotherm must be a dud. FWC has agreed to replace it. It runs most of the time even in mild temps and kills my 2 75ah batteries. The 180w factory solar barely keeps up. FWC has agreed to replace it. Hopefully the new fridge will perform more like what you experience even though it is larger. Your post is encouraging..

 

I run the 130L Isotherm with dual 75 ah batteries and 160w factory panel. Mine keeps up just fine. Keep in mind most of my travel has been in southern California and drive every couple of days. Refer pre-chilled at home but have no problem with it keeping the main compartment in the 30's and freezer in the single digits. I am going to add a 120w portable panel just so the batteries don't get pulled down as much in the hot weather.

[buckland]

I have the small digital volt meter I installed to monitor the batteries (2 AGM) in the camper but did want to know more as to the usage... don't have the deep pocket to buy quality so sprang for the one Bill suggested above. I have the 65L Isotherm and it is quiet and efficient as I have never run into a power problem with the 165 watt solar on the roof. Being a novice electrical person... I know how to set it up but the optimal spot... is it right after the battery on the main wire out?

[rando]

You would want to put the shunt in line with the negative terminal to the battery if you want to know about the status of your battery - but you should check to see if this can measure bi-directional current  - if not it won't be able to measure the charge current to the battery (in which case the Wh measurement is kind of meaningless).

[buckland]

Thanks Rando. I sent an email to their service department asking whether it measures bi-directional current. I'll report back when they do.

[PaulT]

You would want to put the shunt in line with the negative terminal to the battery if you want to know about the status of your battery - but you should check to see if this can measure bi-directional current  - if not it won't be able to measure the charge current to the battery (in which case the Wh measurement is kind of meaningless).

One of the reviews at the link discusses using two of these to measure charging with one and discharging with the other. That implies that these are unidirectional and that manually doing the math between them is necessary to determine SOC.

Paul

[rando]

I am not sure wiring two of them and trying to subtract the 'Wh' readings is really going to give you what you want, and could actually be more confusing.   

 

 The issue with coulomb counting (ie integrating) power meters is that they integrate any small offsets or errors in the measurement, eventually leading to big errors and confusing data.     The bi-directional meters have the advantage that at least their errors are the same in each direction - so if your shunt is a little off or the current meter is a little off it effects both the charge and discharge currents equally and the SOC measurement can still be fairly good.   Using two separate meters, the errors are independent, so if the discharge current meter reads a little higher than the charge current meter, within a few days the difference will be telling you your battery is empty, even if it is full.   

 

Secondly, even if they were dead-on-balls accurate,  you would still end up pretty far off as they don't take into account charge efficiency (about 0.9), which means you need to put 1.1Ah back into your battery for every Ah you take out.   Over the course of a couple of charge cycles this will make the math very tricky. 

 

I don't want to be to much of a downer - the amazon or powerwerx meters could be very useful in understanding the power use by a specific appliance, such as your fridge, but don't expect them to be able to replace a dedicated battery power meter. 

[abqbw]

If I already have the Zamp controller that came with the factory solar system wouldn't it in combo with a unidirectional meter give me all I need. The zamp gives me Ah and (rough) SOC, and Amps coming in from the panels and volts. I'm mostly interested in how much power my fridge is consuming... Compared to what you all are posting about your isotherm fridges mine seems to be a power hog.