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#1 BryanToyFWC

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Posted 23 July 2021 - 08:12 PM

I’ve been reading everything on this forum regarding batteries. You all sound beyond knowledgeable.

I’m not an electrician, so you all are making my head spin. Im handy in a way that I can take stuff apart and figure out mostly anything, but electrical stuff has never sunk in.

I recently scored a 2017 Hawk, side dinette, solar, Zamp controller, 2xAGM 12V batteries (group 24), big fridge (non propane). Well cared for rig, super sweet. I have not changed or updated any of the components of the Hawk, so think everything is original.

It’s riding on a 2021 Tundra Limited with Firestone airbags.

I think my batteries need replacing. When we wake up in the morning, the fridge compressor is cycling through the low voltage protection, zamp controller is reading 10V. When the sun comes up the controller reading climbs, fridge cycles less, and in full sun we are back to 13v plus. Run the water pump and lights flicker a little during this time. My impression is that the 4-5 year old batteries are done.

With that said, I can’t decide between AGM and Lithium. AGM would be an easy swap. Lithium is intriguing for longevity and weight. With Lithium I have absolutely no idea if I need to update more of the electrical components (Iota 30/IQ4, Battery Link ACR, etc). I have no idea if I need new components.

What I really need is for a non technical summary of going Lithium and what if any I need to add and/or replace.

Help!
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#2 rando

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Posted 23 July 2021 - 11:56 PM

Your first step should be to install a battery monitor like the Victron BMV-712 or Victron Smart Shunt so you can see what is actually going on with your batteries.   It sounds like the batteries aren't doing well, but it also may be that they just aren't getting enough charge.   Depending on your usage, and the size of the solar panel, you may not be harvesting enough solar power to charge the batteries enough to get through the night.   You can get some idea about this by leaving the camper plugged into shore power overnight (which will fully charge the batteries), and then seeing how long the battery lasts with your normal loads.  

 

Once you have figured out what the real problem is, you can decide on replacing the batteries. 


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#3 Vic Harder

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Posted 24 July 2021 - 12:13 AM

+1 on what rando said.  Get a shunt based monitor as he suggested so you can get a good reading on what is going on.  Voltage readings are almost useless.


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#4 ckent323

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Posted 24 July 2021 - 03:06 AM

+2 with what Rando suggested

You did not say how much capacity your group 24 battery has.

I think that group 24 batteries have a capacity ranging from about 70 - 85 Amp hours. (Edit: per battery)
 

Conservatively that gives you about 35 to 45 useable amp hours (maybe a bit more).   (Edit: per battery so 70 to 90 Ah total)

Some things to consider:

You said you have a large refrigerator non - propane so I assume it is AC/DC compressor refrigerator.  You said it is a large refrigerator some of the larger models can pull upwards of 3 amps/hr on average depending on the outside temperature.  For exmple here is the info for the the Isotherm 130 

  • Current Draw:
    • Compressor Running: 4.7 - 5.0 Amp @ 12 Volt DC (half at 24 Volt DC)
    • Average: 1.2 Amp @ 12 Volt DC (measured at 43°F in refrigerator, 72°F ambient temperature)

I have seen average numbers for Dometic refrigerators in the 2+ amp range.    If you are using the refrigerator in temperatures higher than 72 degrees it will probably draw more current on average.

Also if you are using the ceiling fan or heater or other powered items that will also up your power consumption.

 

Conservatively assuming your solar system produces neglegble power from 5 PM to 8 AM and your refrigerator will comsume 2 amps an hour on average then 15 hours * 2 amps/hour your battery must provide around 30 Amps overnight.  Edit: That would leave enough capacity to power the system for one subsequent night unless the weather or shade prevents the solar system from recharging your battery during the subsequent daytime.

I did not see the size of your solar panel in your post but it will need to be big enough to produce at least 30 amps during the day.  How much power your panel will produce depends on  a number of things but first order is full sun and no shade or clouds.  If you have clouds or shade your panel will produce less power.

But as rando and Vic have commented you need to measure your power consiumption and then determine how much power your solar system is producing.
 

I hope this is helpful (as well as correct - sometimes I make mistakes in in my posts).

 

Edit:  I checked the FWC website for the largest refrigerator.  I noted the following information:

From the FWC website:

"The Isotherm 130 Liter Refrigerator/Freezer is a compressor style refrigerator unit that runs on either 12 volt battery power or 120 volt shore power electricity. This refrigerator does NOT run on propane. 

 

The benefits to a compressor refrigerator like this, is that is does not need to be level to work properly, once you turn it on, it works, and it usually will cool more efficiently in hot weather. But you will need a dual battery system and a roof mounted solar panel to keep up with the power it uses.

Without dual batteries and a good solar system, this style of refrigerator will drain your camper battery down in about 1 day."

(so with your two battery system you should be able to go two nights without a full recharge but if you do not get much charging during the day, due to clouds or shade, your battery bank may only last 24 to 36 hours).

 

Regards,

 

Craig


 


Edited by ckent323, 24 July 2021 - 08:44 AM.

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#5 CougarCouple

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Posted 24 July 2021 - 03:37 AM

Hello BryanToyFWC
Yes listen to those above. I also read a lot here and elsewhere. Keep educating yourself on what it would take to go Lithium. We got our ATC with 2 AGM’s in 2017 and they just started failing. There can be a lot to going lithium and I’m glad I had the time to get the knowledge.
My guess is it’s about 3x more to go lithium vs the replacement AGM. Hope this helps.

Congratulations on your Hawk

Russ
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#6 JHanson

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Posted 24 July 2021 - 04:46 AM

Lithium technology has awesome potential, but it is far from a plug-and-play proposition at this point. Please read this for some background information.


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#7 Jon R

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Posted 24 July 2021 - 05:09 AM

The rough cost for my lithium battery and solar power system:
200 Ah battery $1250 ahipped
Victron Orion Smart 12/12-30 isolated dc to dc charger $265
Victron Smart MPPT 100/30 solar charger $220
Victron Battery monitor BMV-712 $210
Blue Seas bus bars and fuse block $120
6awg wire, lugs, wiring incidentals $150
Renogy 200watt solar panels (two) $600

Never worrying about having enough electrical energy: priceless

If I was doing it again I’d probably do a single 320 watt panel instead.
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#8 Wandering Sagebrush

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Posted 24 July 2021 - 01:51 PM

Lithium technology has awesome potential, but it is far from a plug-and-play proposition at this point. Please read this for some background information.

Jon, interesting.  Please do continue to keep us updated on your experience.  I’m a bit of a retro-grouch, so it will be good to learn a little more.


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#9 BryanToyFWC

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Posted 24 July 2021 - 02:51 PM

Your first step should be to install a battery monitor like the Victron BMV-712 or Victron Smart Shunt so you can see what is actually going on with your batteries.   It sounds like the batteries aren't doing well, but it also may be that they just aren't getting enough charge.   Depending on your usage, and the size of the solar panel, you may not be harvesting enough solar power to charge the batteries enough to get through the night.   You can get some idea about this by leaving the camper plugged into shore power overnight (which will fully charge the batteries), and then seeing how long the battery lasts with your normal loads.  

 

Once you have figured out what the real problem is, you can decide on replacing the batteries. 

Thank you very much for the thoughtful response!  I'm very much a novice on this.

 

I would assume that after driving for several hours plugged into the truck, or directly leaving shore power to go off camping would also mean that I'm starting the night with a full charge.  Just my naive assumption.  Last weekend we went straight from shore power/home to camping, fridge was low volt protection cycling by early morning (also a 3am propane false alarm, but a different problem I'm reading about here).  By afternoon in full CO sun the voltage reading (understand now this isn't the best way to evaluate batteries, thanks Vic) was 13.5 and everything was running as normal.  Nothing but the fridge running all night (Isotherm 130L compressor).

 

Batteries are 75 Ah each.  Not sure the size of the solar panel, that wasn't in my paperwork!  

 

I will look into a battery monitor.  Something to learn about and install, hopefully without breaking stuff. 


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#10 BryanToyFWC

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Posted 24 July 2021 - 02:55 PM

Hello BryanToyFWC
Yes listen to those above. I also read a lot here and elsewhere. Keep educating yourself on what it would take to go Lithium. We got our ATC with 2 AGM’s in 2017 and they just started failing. There can be a lot to going lithium and I’m glad I had the time to get the knowledge.
My guess is it’s about 3x more to go lithium vs the replacement AGM. Hope this helps.

Congratulations on your Hawk

Russ

Thanks Russ, the Hawk is so fun!  Lithium definitely sounds like a big investment/change.  


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