Battery Management Overview

B

bignerdski

New Member
Joined
Nov 20, 2015
Messages
7
Hey guys,

How's everyone doing?

I'm the proud new owner of a Fleet that was installed on Monday. I've been reading up on forums, the user manual, and all over the internet in order to educate myself as much as possible and to avoid paying unnecessary idiot tax.


An area where I continue to get lost is battery management. As I've sifted through the information, the answers are so granular that I'm having a hard time grasping the larger concept. If anyone can explain in layman's terms, or their personal approach, it would be appreciated greatly.

My goal is to know how to use my FWC properly so I don't kill my batteries and understand the relationship between my 160 watt solar panel and 2 battery set up (Exide group 24, 75ah x2).

Some specific questions are as follows:
  • Does the Zamp Solar Controller act as a tri-metric battery monitor as well as monitoring the solar data?
  • Can you explain the relationship between Volts, Amp and Amp/hours in general?
  • During the day, the zamp controller shows various values for Volts, Amps and Amp/hours. Are the values instantaneous values of what is happening at that moment. Do volts indicate the current state the batteries are in?
  • Should I be weary of running the fridge (85L) too long?
Again, thanks so much for the advice.

Best,
Adam B
 
bignerdski said:
--snip--

Some specific questions are as follows:

  • Does the Zamp Solar Controller act as a tri-metric battery monitor as well as monitoring the solar data?
  • Can you explain the relationship between Volts, Amp and Amp/hours in general?
  • During the day, the zamp controller shows various values for Volts, Amps and Amp/hours. Are the values instantaneous values of what is happening at that moment. Do volts indicate the current state the batteries are in?
  • Should I be weary of running the fridge (85L) too long?
Again, thanks so much for the advice.

Best,
Adam B
Click to expand...
Congratulations on your camper.
1. Zamp controller has some features of Trimetric but not as complete plus the Zamp is also a charge controller.
2. Think of volts as how hard the electrons push, amps as rate of flow down the wire, and amp/hours as how much energy is stored in the battery or how much of the battery's contents was consumed by a device over time
3. Displayed volts and amps are instantaneous readings. Amp hours on the Zamp is not a useful reading because it does not take into account charging by the truck or the Iota power supply.
4. Voltage gives a poor approximation of State of Charge unless the battery has been sitting for hours withoun charging or power being removed by devices.
5. Use the voltage to tell you when your running the fridge has pulled the batteries low and then run your truck to recharge the batteries if you have insufficient solar to keep it charged.

The 160 watt should be able to more easily keep the batteries charged than the 100 watt panel FWC used to supply. For a while record the Zamp voltage in the morning before solar charging and in the evening after charging stops untill you get familiar with how your system works. You will get in the habit of staying aware of your battery SOC and learn when to start the truck to charge the batteries before they get too depleted. Use your camper like you want but be aware that continued overcast or camping under trees in hot weather may require running truck more than usual.

Paul
 
Adam, first welcome aboard. You are in for some fun. I'm one who reads this forum on a regular basis, but some of the topics are way over my head. I chose not to get caught up and get myself more confused. We have a 2014 Grandby with 2 batteries and 100W solar panel on the roof. We have the 80L compressor fridge and I use a CAP Machine. We watch the AMPs very closely and have never gotten close to the danger zone. When we drop the top to sight see we are also charging the camper. I held off purchasing the 80W portable solar panel for a year. When we are going camping off grid I take the portable panel. Right now my camper is Covered and I check on it every week. All power is off and I plug the portable panel in every 3-4 weeks. Saturday was sunny and I charged for 4 hours getting my amps up to 13.3. We have camped with lots of rain and never have I gotten nervous. With 2 batteries and 160W you shouldn't have any issues or concerns. You didn't mention whether you are going camping anytime soon or storing your camper for warmer weather. Like I said, the electrical is completely off and the fridge door is open. If you aren't going anywhere you can turn the power off or just the fridge. Enjoy your camper. jd

Sent from my SM-G900V using Wander The West mobile app
 
bignerdski said:
  • Can you explain the relationship between Volts, Amp and Amp/hours in general?
Click to expand...
Here's an analogy for what Paul explained on this fundamental point.

It's like water stored in a reservoir behind a dam (like a battery, a way to store and provide energy), with a pipe coming out of the bottom of the dam (the pipe is like the wires):
"Volts" are analogous to how deep the water is behind the dam (over the pipe) -- how hard the water can push, how much pressure at the pipe
"Amps" are analogous to the flow rate of water coming out of the pipe (e.g., "10,000 gallons per minute")
"Amp-hours" are analogous to an amount of water -- how much water is stored behind the dam or how much water has flowed out of the dam (e.g., "10 million gallons")


And welcome to WTW, bignerdski :)
 
northshorehenry said:
I find this to be an excellent read. http://www.marxrv.com/12volt/12volt.htm


Sent from my iPad using Wander The West
Click to expand...
Period in the URL (not the text) is going 404, try: http://www.marxrv.com/12volt/12volt.htm

the link above looks to cover the basics and there are some good books on the topic. I have these two for reference:
http://www.amazon.com/gp/product/0071392335?keywords=the%2012%20volt%20bible&qid=1455552776&ref_=sr_1_1&s=books&sr=1-1

http://www.amazon.com/gp/product/0964738627?keywords=managing%2012%20volts&qid=1455552746&ref_=sr_1_1&s=books&sr=1-1
I think either will be a good choice, but it is my recollection that the Barre book is a little more user friendly.

When you feel that you've got a good grasp on the basics have a look at: https://handybobsolar.wordpress.com/
Without a grasp of the basics I fear that Handy Bob's blog will be more hurtful than helpful. Some of what he says doesn't apply or is way over the top given the way that pop-tops tend to be used. To be fair, he is writing from the full-timer's perspective with other full-timers in mind.
 
Everybody, thanks for all the great info. I’m currently reading through the links you sent, which will probably result in more questions. Until I get through them all, I've responded to everyone below.

@PaulT
All this is great. I’m pretty sure I get what you’re saying. Bear with me, and let me summarize in my own words to see if I’ve got it right:
  1. Besides the Zamp’s main functionality as a charge controller, I can roughly use it to gauge the current state of the battery but without the exact specs a true Trimetric would provide.
  2. Got it. Basically, Amp Hours is how much energy I have to use in my batteries. From what I’ve read as well, you never want to drain more than 50% of the batteries. Correct?
  3. Instantaneous Voltage is the reading of the batteries is at the current state. Instantaneous Amps is how much current is being generated by the solar panels at that moment. I understand that Amp/hrs is how much energy is stored in my batteries, but does the Amp/hrs reading on the Zamp controller indicate how much energy is being put back into the batteries?
  4. If Voltage is a poor approximation of the SOC, should I pay much attention to the Voltage reading on the controller?
  5. Is there a do not dip below this number? I think I read if you dip below 12.2 Volts, that’s no bueno.

@longhorn1
What’s a CAP Machine? Cappuccino? (kinda serious/kinda joking). When you watching your AMP’s closely, what exactly are you looking for? Do you mind giving me a couple specific scenario for context? Also, I live in Portland, OR so we’re not exactly the sunshine state. I’m starting to think my camper will live on my truck permanently (my drift boat took up the extra driveway space). I’m taking the family out for an inaugural trip this coming weekend, so I’ll put everything to the test then.

@MarkBC
I speak fluent analogies. Thanks Mark. I understand the basic difference between Amps and Amp/hours, but am still unsure of when to pay attention to one versus the other. You got another analogy up your sleeve?

@northshorehenry
Reading this now. Thanks bud.

@ntsqd
I’ll get to these after I get my solar/battery legs firmly planted in the ground. Appreciate the resources.

@ETAV8R
That Expedition Portal link looks deep. Appreciate that as well.

@Timothy McGowen
Thanks for the kind words. Looking forward to contributing more as I learn more.
 
bignerdski said:
Everybody, thanks for all the great info. I’m currently reading through the links you sent, which will probably result in more questions. Until I get through them all, I've responded to everyone below.

@PaulT
All this is great. I’m pretty sure I get what you’re saying. Bear with me, and let me summarize in my own words to see if I’ve got it right:

  • Besides the Zamp’s main functionality as a charge controller, I can roughly use it to gauge the current state of the battery but without the exact specs a true Trimetric would provide.
  • Got it. Basically, Amp Hours is how much energy I have to use in my batteries. From what I’ve read as well, you never want to drain more than 50% of the batteries. Correct?
  • Instantaneous Voltage is the reading of the batteries is at the current state. Instantaneous Amps is how much current is being generated by the solar panels at that moment. I understand that Amp/hrs is how much energy is stored in my batteries, but does the Amp/hrs reading on the Zamp controller indicate how much energy is being put back into the batteries?
  • If Voltage is a poor approximation of the SOC, should I pay much attention to the Voltage reading on the controller?
  • Is there a do not dip below this number? I think I read if you dip below 12.2 Volts, that’s no bueno.
Click to expand...
1. You can get an approximation of SOC from the Zamp
2. Essentially correct but that is 50% of amp hrs, not 50% of voltage. Here is where the Trimetric has an advantage.
3. As near as I can tell, the Zamp amp hrs indicates how much solar generated energy has been sent to batteries but does not include energy from truck or shore power nor does it track power consumed from battery.
4. Voltage does give some indication of SOC but be aware that indicated voltage will drop when a power draw like fridge is happening & rise after the power draw stops. This makes judging SOC from voltage iffy.
5. If the charge gets too low, you may have to turn off the loads to allow the solar to bring the voltage up enough to allow the battery separator to connect to and charge from the truck. And, yes, you can shorten battery life by too deep discharge.

Paul
 
bignerdski said:
@MarkBC
I speak fluent analogies. Thanks Mark. I understand the basic difference between Amps and Amp/hours, but am still unsure of when to pay attention to one versus the other. You got another analogy up your sleeve?
Click to expand...
When to pay attention to amps vs amp-hours? Well...it depends on what you want to know.
Another analogy? OK, how about this one, based on motion: Amps are like speed -- how fast you're moving. Amp-hours are like distance -- how far you've gone or how far you have yet to go. You divide distance by speed to get the time it'll take to travel the distance. And you divide amp-hours by amps to get time to empty (at that discharge rate). And both quantities are needed to figure that out.

I think both quantities are important...but I guess I might say that amp-hours are what you should pay most attention to, just as (yet another analogy) "I have 1/8 tank of gasoline left in the truck's tank" is probably more useful to know than "I'm using gasoline at 1 cup per minute".

But, as Paul points out, that meter doesn't directly measure how much energy (amp-hours) are in the battery. So, you may not really know how many amp-hours of energy you have in the battery.

So, what do I pay attention to with my system (240 watts of solar feeding into two 130-amp-hour batteries)? Well, I don't have a meter that monitors energy in and energy out, my simple meter only measures what the solar panels are feeding and have fed the batteries, so I don't have any kind of measure of amp-hours in the battery.
I pay attention to battery voltage. Yep, the voltage can be misleading -- even completely wrong -- when my solar panels are charging the battery and similarly misleading when my refrigerator is pulling several amps from the battery. But I'm aware of that and can still get useful, if approximate, information about "how full" my battery is, based on voltage.
  • If it's late at night or pre-dawn in the morning, it's been hours since the batteries were receiving solar charge, and if it's been a while since my fridge has been running, then the battery voltage on the meter is a good approximate indication of the battery charge.
  • Even when my solar panels are charging the battery I can still get useful information: If the charge controller light is steady on then it's in bulk charge stage -- a ways to go before full. If the light is blinking slowly then it's in absorption stage -- getting up there. If it's blinking fast then it's in float stage, battery full or close to it.
Of course, this is only approximate...but I don't need high accuracy. In that sense it's not like the gas tank analogy -- the consequences of "running out" aren't nearly as bad for my camper electricity as it is for truck fuel when driving in the middle of nowhere.
And I can always run the engine and drive if I need to charge the camper batteries.

(By the way, that "amp-hr ÷ amps = time" calculation is only theoretical. And rate of discharge affects the amount of electricity that's available. That is, the higher amps you're pulling from a battery the less total amp-hours you'll be able to pull. It's kinda like driving faster reduces gas mileage, so you can't go as far on a tank of gas when you're driving fast.)
 
+1 on the analogy to the fuel tank with the caveat that you don't reduce the fuel tank capacity by running it too low.multiple times.
The liquid analogy simulates the electrical system only so far. :p I started to use it in my reply to OP but have been pounded around the ears too many times by more pedantic electrical engineer co-workers after using it. :oops:

Paul
 
I too have been subjected to that by my EE co-workers. So now I use it exclusively in their presence. :)
 
Alright, I think I have the basics understood well enough to put theory into practice this weekend.

Thanks for the further clarification @PaulT and @MarkBC.
 
And you know what? It's ok to make a mistake. We have all left a porch light on now and then, ran the battery low, and oops. No different then if you left your head lights on. Fortunately, if you ran your house battery low, you can still get in your truck and drive away. Experiment a little the first few nights. Perhaps go to a place where shore power is available. Run your camper for an entire night with the furnace on and see where the battery ends up, the shore power in the morning will make your life easier. When you have a good idea of what your system is capable of, then start the boondocking experience.


Sent from my iPad using Wander The West
 
PaulT said:
5. If the charge gets too low, you may have to turn off the loads to allow the solar to bring the voltage up enough to allow the battery separator to connect to and charge from the truck.

Paul
Click to expand...
This is a great thread - I have almost the exact same set-up (but w/ 2 6 volts) and am trying to understand it better.

This one really caught my attention as I had never considered this and need to research this further. Now that i look back I may have had this exact problem on a prior trip. Now I need to find the separator and see if it has any specs on it for connecting.

-Vic
 
You must log in or register to reply here.

Similar threads - WTW

S
Appropriate batteries for Hawk FB?
Sagefemme
S
S
I did a stupid solar thing!
pvstoy
pvstoy
K7MDL
Installed Renogy One Core monitor and Battery Shunt 300
K7MDL
K7MDL
S
Battery died, time for big conversion solar, fridge, etc
2
craig333
craig333
J
2021 Total Composites camper and 1999 Ford F-250 Super Duty, $40,000, Fraser, CO
jklabak
J

New posts - WTW

Back
Top Bottom