FYI Solar 101 - A General Guide to Solar in your RV or Motorhome

[Richpatty]

These recommendations make sense and my Magnum devices are above recommended levels and I have not had any issues with charging my Lithiums. I am using the ARC50.

And each manufacturer has their own recommendation. Here is what Battelborn told me:

To set for lithium battery charging in a 12VDC system:

• Press the SETUP button;
• Turn SELECT knob to 03 Charger Setup, Press the Select knob;
• Rotate to 03C Battery Type, press Select knob;
• Rotate to Custom, press Select knob;
  • Absorb volts = 14.4VDC;
  • Float volts = 13.2VDC;
  • EQ volts = 14.4VDC;
  • EQ Done Time = 0.1hrs
• Rotate to 03D Absorb Done Time, press select knob;
• BattleBorn wants this set for 0.5hrs per parallel battery string, if you have 8 12V batteries then this would be 4hrs.
• Rotate to 03G, press Select knob;
• Rotate to Silent, press Select knob;
• ReBulk volts = 13.2VDC

 

[Notsotalltexan]

Thank you Neal for your reply. This is interesting. As you said, your solar array is just a battery charger. It happens that the original owner of my 3709, from whom I bought the coach, lives in Wisconsin. He learned the hard way and had to replace his eight factory installed 6V batteries. So, they're newer FLA batteries, eight 6V Duracell to be specific. So obviously Neal, since you've not made the switch, your FLA battery bank does the job.
Since we plan to dry camp on our half acre lot in northern NM at 9200 feet, we won't need to run our air conditioners. Maybe I could wait to see if my FLA batteries power our residential Whirlpool fridge, TV, lights etc.. without having to use the generator.

And thank you Richpatty. So does your Magnum Energy Remote Control manual say ARC50 or ME-RC like mine? And, do you mean each battery manufacturer or each inverter manufacturer? "And each manufacturer has their own recommendation. Here is what Battelborn told me:"

 

[Neal]

It's all about amp hours and usable capacity. LifePO4 opens up that capacity window as we only get down to 60% realistically with FLA, not to go below 50%. I run everything from frig, tv's, computers, etc. with my setup, I originally installed it as I had no power storage and I didn't want to empty/load the frig every time but more so not be cycling power circuits as that's when things fail. I'll note that I've done tests on what my SOC is in the morning when home theater is on, computer is left on and compare that to a more conservative power setup for overnight in between solar availability. Without being conservative I'm waking up around 70% SOC which is not going to be enough to turn on the Keurig without a low battery voltage cutoff spike. With a conservative approach I can wake up to around 80-82% SOC. So many variables but yes, if you have the amp hours it can be done.

 

[Richpatty]

And thank you Richpatty. So does your Magnum Energy Remote Control manual say ARC50 or ME-RC like mine? And, do you mean each battery manufacturer or each inverter manufacturer? "And each manufacturer has their own recommendation. Here is what Battelborn told me:"

My remote is the ARC50, which is different (it is an upgraded version with more controls and features). It is an easy upgrade (unplug old one, plug new one in). If you are going to boondock, this would be a good upgrade as It allows you to use the Magnum BMK (battery monitoring kit) which allows you to see what your battery bank SOC (state of charge) is. It is critical if you really want to see where you batteries stand - regardless of type.

As far as manufacturer recommendations, yes to both…..but I tend to follow the battery manufacturer as they know best how they batteries perform under various charging scenarios.

Hope this helps.

 

[Kevin D Pem]

It's all about amp hours and usable capacity. LifePO4 opens up that capacity window as we only get down to 60% realistically with FLA, not to go below 50%. I run everything from frig, tv's, computers, etc. with my setup, I originally installed it as I had no power storage and I didn't want to empty/load the frig every time but more so not be cycling power circuits as that's when things fail. I'll note that I've done tests on what my SOC is in the morning when home theater is on, computer is left on and compare that to a more conservative power setup for overnight in between solar availability. Without being conservative I'm waking up around 70% SOC which is not going to be enough to turn on the Keurig without a low battery voltage cutoff spike. With a conservative approach I can wake up to around 80-82% SOC. So many variables but yes, if you have the amp hours it can be done.

Would like to add! When considering how low to discharge, 80% charge is what is accepted as a cycle. So typical FLA have been rated with??? 365+- a few cycles.
If you cycle batteries daily (deeper than 80%), you can expect annual replacement if your full time. Your batteries have cycle life on the label.

 

[Richpatty]

Hi Kevin, I am not sure where you found those numbers, but they do not reflect generally accepted values for LA batteries. I have never seen anyone claim 80% soc as a cycle nor that LA batteries only have 365 cycles before they are exhausted….

Lead Acid battery downsides

Learn about the limitations of lead acid batteries and why exceeding their recommended usage can drastically shorten their lifespan.

www.powertechsystems.eu

 

[Kevin D Pem]

Hi Kevin, I am not sure where you found those numbers, but they do not reflect generally accepted values for LA batteries. I have never seen anyone claim 80% soc as a cycle nor that LA batteries only have 365 cycles before they are exhausted….

Lead Acid battery downsides

Learn about the limitations of lead acid batteries and why exceeding their recommended usage can drastically shorten their lifespan.

www.powertechsystems.eu

I think it came from batteryuniversity but couldn't find it. However I can support my claim with data that shows typical cycle life.

Cycles vs Lifespan​

A battery "cycle" is one complete discharge and recharge cycle. It is usually considered to be discharging from 100% to 20%, and then back to 100%. However, there are often ratings for other depth of discharge cycles, the most common ones are 10%, 20%, and 50%. You have to be careful when looking at ratings that list how many cycles a battery is rated for unless it also states how far down it is being discharged. For example, one of the widely advertised telephone type (float service) batteries have been advertised as having a 20-year life. If you look at the fine print, it has that rating only at 5% DOD - it is much less when used in an application where they are cycled deeper on a regular basis. Those same batteries are rated at less than 5 years if cycled to 50%. For example, most golf cart batteries are rated for about 550 cycles to 50% discharge - which equates to about 2 years.

Battery life is directly related to how deep the battery is cycled each time. If a battery is discharged to 50% every day, it will last about twice as long as if it is cycled to 80% DOD. If cycled only 10% DOD, it will last about 5 times as long as one cycled to 50%. Obviously, there are some practical limitations on this - you don't usually want to have a 5 ton pile of batteries sitting there just to reduce the DOD. The most practical number to use is 50% DOD on a regular basis. This does NOT mean you cannot go to 80% once in a while. It's just that when designing a system when you have some idea of the loads, you should figure on an average DOD of around 50% for the best storage vs cost factor. Also, there is an upper limit - a battery that is continually cycled 5% or less will usually not last as long as one cycled down 10%. This happens because at very shallow cycles, the Lead Dioxide tends to build up in clumps on the the positive plates rather in an even film. The graph above shows how lifespan is affected by depth of discharge. The chart is for a Concorde Lifeline battery, but all lead-acid batteries will be similar in the shape of the curve, although the number of cycles will vary

The Northstar blue+ is my battery of choice...

 

[Richpatty]

Ok. You are talking DOD while I was talking SOC, which have opposite values….

 

[Notsotalltexan]

Update: I found an ME-ARC and will swap it out when it arrives.

I've decided to purchase most all components for my system from A.M.Solar. The only component I will acquire myself is the Cyrix battery combiner. What I need to know from either Neal or Rich or anyone else is what is the alternator rating? I need this prior to purchasing the unit. Is it 120A or 230A? My coach is a 2017 Ventana 3709 with a Cummins 360.

Victron Cyrix Battery Combiner

Victron Cyrix battery combiners connect your house battery bank to your starter battery and alternator to allow alternator charging. Additionally, when a charge is applied to a house battery bank the Cyrix will close and allow current to flow to the starter battery. Select an appropriate Cyrix based on your house battery type and alternator current rating.

Alternator 160A or less - 120A Cyrix
Alternator more than 160A - 230A Cyrix

 

[Notsotalltexan]

My remote is the ARC50, which is different (it is an upgraded version with more controls and features). It is an easy upgrade (unplug old one, plug new one in). If you are going to boondock, this would be a good upgrade as It allows you to use the Magnum BMK (battery monitoring kit) which allows you to see what your battery bank SOC (state of charge) is. It is critical if you really want to see where you batteries stand - regardless of type.

As far as manufacturer recommendations, yes to both…..but I tend to follow the battery manufacturer as they know best how they batteries perform under various charging scenarios.

Hope this helps.

Hey Rich-- Did your Ventana come with a Magnum BMK like this? Or did you buy it after your went solar?

Magnum Energy ME & MS Series Battery Monitor Kit (ME-BMK)​