Measured FWC power use

I started this camping season,to shut the 3/way off about an hour out from the nights camp. That way all the trucks and solar charging will go into the camper battery.
Not by any means an expert,but it seems to work. Now that I have upped my solar to 100w I feel better about a good battery charge for the night time hours.
I have a watt meter to place in the system maybe it will give me more useful info.
Frank
 
Cayuse said:
With only having the built in FWC meter currently I can only present ancillary evidence based on my experience but since I put in my Isotherm 65 a 2-3 hour drive with the fridge running only brings the charge up to 4 lights most of the time. If I drive 5 hours with the fridge running it will bring the batteries to all the way full. Doesn't seem to matter what level the batteries were at when I started.

Hopefully this is all going to change soon as 200W of solar is scheduled to be delivered next week!
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Mine does that too but the meter on our campers are very optimistic. At 12.5 my meter will say charged but that's not close to the 12.8 my battery sits at when charged with my iota/iq4. What's 12.5 like 80% charged?
 
Here is a link for the percentage of charge based on battery voltage:
http://modernsurvivalblog.com/download/battery-state-of-charge-chart.pdf

The problem is always that the voltage is always based on a resting battery. So if there are loads on the battery it is not always accurate.

Then the battery monitors are always very optimistic. It may show a full battery at 13-13.5 volts when it wouldn't even be close to charged at that point. The trimetric won't show 100% until the amp hours are all restored or the voltage and amps meet the criteria you set.

It's very frustrating trying to make a decision on your power use if you don't really know what's happening.
 
DrJ said:
Here is a link for the percentage of charge based on battery voltage:
http://modernsurvivalblog.com/download/battery-state-of-charge-chart.pdf
The problem is always that the voltage is always based on a resting battery. So if there are loads on the battery it is not always accurate.
Then the battery monitors are always very optimistic. It may show a full battery at 13-13.5 volts when it wouldn't even be close to charged at that point. The trimetric won't show 100% until the amp hours are all restored or the voltage and amps meet the criteria you set.
It's very frustrating trying to make a decision on your power use if you don't really know what's happening.
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That's the exact thing I have learned by adding a refrigerator to my camper. That's why I'd be so interested to see what the trimetric says about the charge it gets from an alternator.

I drive a lot when I go on vacation so if the alternator is charging my batteries to 90% I'm OK with cycling them that way for a few weeks before they get a good charge. However, if the alt is only charging to 80% that's too low for my taste and it would confirm my need for a solar panel permanently mounted to top off my batteries more often.
 
Since float voltage is typically about 13.6 volts for lead acid batteries, 13.5v would not be optimal.

From what I understand about the voltage sensing battery isolator that FWC installs, the truck alternator will not be allowed to provide charging power if the camper battery voltage drops below a certain level. That would mean running the engine earlier if the sun doesn't cooperate or your alternate charging source can't work.

I guess in a pinch, you could use an inverter to produce AC from the running truck and plug that into the camper AC input although that seems risky as the camper chassis is electrically tied to the truck chassis and who knows what is the electrical potential of the inverter case.

That Trimetric and careful note keeping while camping is becoming more attractive. Great thread even if there are more questions than answers.

Paul
 
After hearing so many requests about truck charging, I've started an experiment this week to test it out.
I'm disconnecting the solar panel system. This is really easy to do - just unplug it at the roof.
I'll continue to run the compressor fridge until I get the battery to 50% of charge. Then the only charging method will be from the truck.
Later this week I have a several hour drive to make. We'll see just how much power gets restored per hour of driving and if I can get back to 100%. Total drive time is about 6 hours so if the system works that should be a reasonable time to try it out. I'll also look at the FWC battery charging lights and see what they tell me along the way. I will try it running the compressor fridge along the way as that would be the most common way I traveled. Should be interesting to see how much battery power is restored. I would think 80-90% of recharge in 6 hours of driving.
Any other guesses for how much battery can be recharged?
 
I'm guessing closer to the 80% but I'm pessimistic at times. Do you think you can also tell me what voltage you get at your aux battery with the truck running, solar disconnected, fridge running and battery at 50% charge? This should give me an idea of your voltage drop compared to mine.

Thanks in advance for your willingness to experiment. This is helping me refine my setup until I can blow some cash on a trimetric myself.
 
Smoke, we are currently using the truck engine on idle when off the grid for two days when we don't take the portable 60 watt panel. Idling the truck for 1 hour increases voltage from 12.3 to 12.9 volts. ....Bottom reading slowly drops point one volt every 12-14 hours running the comp refer and lights couple hours in evening.

We use a what meter to check the amp draw of the refer ...Range 2.5 down to 1,5

As I read this I wonder if a "Trimetric" would be overkill for just 4 circuits??

Ether I get 13.6 volts engine running and refer cycling on - off
 
RC what size is your wiring and what are you getting off your truck battery? My voltage is 13.5 at the truck battery and 12.5-9 at the aux depending on if the refer is running or not and the state of charge of my aux battery.

Is that number with a fully charged battery?
 
I have 10 gauge wiring from the truck back to the camper. I get 13.95 V from the alternator at the camper battery with the truck engine at 2000 rpm.
 
ski3pin said:
I have 10 gauge wiring from the truck back to the camper. I get 13.95 V from the alternator at the camper battery with the truck engine at 2000 rpm.
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That's incredible. Is that with the battery fully charged. What voltage do you have from the main battery?
 
I will measure the volts at the truck battery tomorrow at 2000 rpm. I've calculated the difference (drop) before just don't recall it right now.
 
Ether, wiring gauge is stock FWC .i beleve it is 10 gauge from engine compartment to the separator. Will measure tomorrow.
I have the trailer pkg so I have the 130 amp alternator.

On my trip to Oregon I camped two days off the grid without a solar panel and recorded the following readings.

Recorded (conditions) Temp cool – low 70’s during day.Mid 50’s at night.
Day 2
Engine off overnight - 17 hours – low reading 12.3 volts. Run engine one hour (6: am) = Voltage 12.9
Engine off 12 hours – low reading 12.2 volts. Run engine one hour (6:pm) = Voltage 12.9
Day 3 morning
Engine off 13 hours – low reading 12.1 volts. Run engine one hour (6am) = voltage 12.9
Charging voltage 13.6. I was losing ground over time so wasn't completely charging the battery just idling 1 hour per day at about 1500 rpm.
 
If you have an iPhone iPad, download one of the Voltage Drop apps. Most are free and work fine. The most important thing to remember in using them is that you must use the total wire length from the truck battery plus the return path back to the truck battery. (Or solar panel, or camper battery, etc). Some assume there and back for length. Others expect you to do the math.

Tools also exist for Android. You can have the apps calculate the voltage you drop will see, the wire size you should use, etc. Follow up with measurements to ensure you are OK.

On my iPad, I use "Voltage Drop" & "Circuit Wizard by Blue Sea Systems". The latter will calculate fuse size also.

Paul
 
I have just started draining down the batteries for my experiment but looked at the Trimetric meter this am.

With the truck just idling the meter showed 13.4 volts. It was at 93% state of charge and charging at 3.5 amps/hour at that moment.

Should be interesting to see the voltage and amps with the truck at 2000 rpms.
 
I've been letting my fridge run down to batteries to 50% and have noticed some interesting findings from the stock battery monitor that FWC installs.
It of course has 4 lights with each representing a percentage of charge. Here is the breakdown:
4 lights - full or 100%
3 lights - 2/3 full
2 lights - 1/3 full
1 light - empty?

I have found the following with my trimetric readings:
4 lights - anything above 12.4 volts
3 lights 11.9-12.3 volts
2 lights 11.8 or lower
1 light - I've never discharged the battery below 11.8 to find out

Has anyone else with a volt meter had similar data?

This would mean that if you are depending on the FWC monitor for data, it's incredible optimistic.
There is some difficulty determining your battery reserve by voltage alone, but the monitor might be leading you astray.

If your battery is charged by truck or solar only to the start of 4 bars - 12.4 volts - it's no where near close to being charged.

If you only have 3 lights, you have discharged a significant portion of your usable battery bank and it's no where near 3/4 full - which is what I originally thought when I relied on that monitor. Probably closer to 50%. I am not a big fan of discharging my batteries below 50% as I worry about damaging them.

If you have only 2 lights, your battery is close to being discharged too much and you need to charge it right away.

I would have to assume that if you only see one light, you have discharged your battery too far and could potentially damage it.

Anyone else have similar findings?
 
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