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Old 02-13-2021, 11:29 AM   #21
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Originally Posted by 1der View Post
Just some musings for a Saturday morning. I am interested in how others are solving this low temperature constraint.
I mounted two BattleBorn batteries (200Ah total usable) under the goucho a little over a year ago. I selected this location because it was an unused cubic foot-ish which was where the original lintellipower charger was. I removed the charger years ago after installing an inverter charger elsewhere thus making the charger redundant. Before purchasing I tested various lithium battery sizes with cardboard mock ups. Discovered the BattleBorn GC2 (golf cart size) fit with such perfect clearance it looked as if the goucho was fabricated around them. I can install or remove them without disturbing the goucho frame. My decision to go to lithium was contingent on weather I could mount them inside. For me, the idea of hanging this amount of money in batteries under the van in the original location just wasn't palatable. Now into my second Colorado winter with them I'm very glad they are inside the heated van. Lots more to talk about but just wanted to share a suggestion to the packaging challenge for a lithium retrofit. There are a few more pictures in my album if interested.

Also, I don't believe lithium is the end all be all solution for energy storage. Lithium has lots of advantages but in some cases lead may still be the best choice. Cost still being a big one but that may continue to change.

- Eric


Cardboard mock up



Batteries in there final location.

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Old 02-13-2021, 02:42 PM   #22
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Originally Posted by ShuttlePilot View Post
...I selected this location because it was an unused cubic foot-ish which was where the original lintellipower charger was. I removed the charger years ago after installing an inverter charger elsewhere thus making the charger redundant. - Eric
I like that whole idea Eric - been trying to figure out how to mount three Firefly 116amp Batteries under my rig using the same space the AGM now sits (just behind the rear axle), but the only way I can make that work is by reducing the grey water tank by half its size...not sure I want to go that route.
I like your idea, but just can't think of where i would move the charger without compromising additional interior space - do you mind revealing where you mounted yours?

Edit: By the way - nice job on your install!
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Old 02-13-2021, 05:22 PM   #23
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Originally Posted by 1der View Post
The wind chill factors present under the van while of driving had to be near 0 F.
Wind chill won't affect your batteries -- it's a perception thing based on how fast heat is carried away from your skin. No matter what the wind chill is the batteries will never get below the still air temperature.
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Old 02-13-2021, 05:34 PM   #24
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Wind chill won't affect your batteries -- it's a perception thing based on how fast heat is carried away from your skin. No matter what the wind chill is the batteries will never get below the still air temperature.
Thxs Orv - I did not realize that but totally (now! haha) makes sense.
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Old 02-13-2021, 05:57 PM   #25
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- do you mind revealing where you mounted yours?

Sure, it's an old photo for a different thread but the inverter is in the same place today. It's a Magnum MMS-1012 1000 watt that I have ran harder than I should admit to. This location was where the original owner had a stereo amplifier that wasn't needed any more so I just utilized the same location. The little fold up shelf is one of Mrs ShuttlePilots most used features once parked and just passes the inverter when deploying.

- Eric

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Old 03-10-2024, 12:03 PM   #26
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Hi Everyone,
I just want to say WOW to all the reply's regarding changing over to Lithium.
I am happy to report several years later that everything is still running fine and I have not had to adjust any part of my change over to Lithium, still no DC to DC just the BluSea.

The real unanswered question was going to be the sub freezing temperature affect on the batteries mounted underneath. Well I gave this a good test drive above Flagstaff, AZ in 12 degree temps over several days. I watched the battery temperature and it never approached the cutoff temp, reason being that while the batteries are working they produce some heat of their own. I have no external heaters installed as a safety net. The other unknown answer was what about extreme heat. Well I frequent the deserts and Baja just for this reason, warmth and relaxing water. I had the privilege of being in Arizona during an extreme heat of 122 degrees outside. Once again the batteries surprised me with no failure what so ever.

The bottom line here is, it works and reliable and kiss.
Best to everyone!

Sam
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Old 03-14-2024, 02:16 PM   #27
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Sloya,
I understand that you think you have a workable system despite defying conventional wisdom. So rather than simply throwing darts, I tried take the information you provided and determine what can be deduced from that data. In certain instances, I introduced other typical/standard information related to charging LiFePo4 cells.

You have done a good job of researching your system and the tradeoffs, but there are some of your conclusions that need a little more detailed analysis. The primary one of course, the evidence will tilt toward a DC-DC Charger to match your battery system even though you may not need it for your particular (low) consumption profiles.


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Mine has a steady 14.0 volts
output. The thing that saved me from having to add a DC to DC charger was the fact the Blue Sea Battery Isolator charges the batteries to 80-90 percent charge, not 100 percent. Because of this fact it prevents the high charging that is known to burn up alternators using lithium batteries.
What burns alternators is too high of a current demand that exceeds the cooling capacity of the alternator. Cooling capacity in minimal at idle because the built-in fan speed and airflow are minimum. Lithium batteries have low internal resistance which means they more readily accept charge and are capable of demanding large currents from an alternator. Generally, this is not a problem except when a DC-to-DC convertor is installed. The DC-DC has a built-in boost battery charger that operates down to > 9volts typically. The DC-DC tries to maintain the (selected) rated current e.g. (40Amps @ 14V) but to do this with 10 V at the input terminals (voltage drops between DC-DC and alternator, or overtaxed alternator outputting less than 14V) it would have to boost the voltage making the alternator current draw much higher (e.g. 40*(14v/10v)*(100%/.90%)) = 40*1.54=62 amps! This is what can overheat the alternators. Some type of control must be used. A simple control is only activating the DC-toDC when at highway speeds. Alternator thermal control is another)

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Here is the trade off using the Blue Sea, you only get a max of 90% charge while driving. If you are one of those who has to have 100% charged batteries, you can spend the extra money for that last 10% of charge. Having solar takes care of charging the batteries to 100% during the day, and if you have shore power you are all set.
I tried to track down what your logic was for this statement and found this.

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Let's start, you are absolutely correct about the Blue Sea ACR not knowing anything about Lithium. However it does know to switch off at around 13.7v. I think if you do the math it would equal that 80-90 percent charge status you see in the SMB manuals for house battery charging. I have come across a couple of manufactures that make something similar but has an adjustable voltage setting allowing you to increase or decrease the switching point. I find the Blue Sea doing what it does best and no need for the 100% charging during driving. When I arrive at a site 80-90 percent is plenty to get me through the night. The next day the solar will pickup or I will be driving again. From everything I have read lately is that by not charging to 100% you increase the battery life of lithium batteries. This is a big plus considering the cost of lithium batteries.
I would be very surprised if the Blue Sea ACR stops charging when the Lithium is at SOC=90% even if it does switch off at 13.75V. I don't think you have considered the significant voltage drops you could be getting between the Alternator and you LiFEPO4 battery and another unknown is where in that ACR is in between (it affects how much of the alternator-battery voltage drop it sees)?

If your alternator is only outputting 14V at the alternator terminals, then you only have about 0.5 Volts before your Lithium terminal voltage is only 13.5V. I ran some numbers for your 315 amp-hr battery array. If you had 2,5,8 AWG wire you would push 31.5A,15.8A,8A respectively ( through the wires between the alternator and battery array ) without dropping below 13.5V.

It is a little difficult to estimate how much current the alternator is pushing to your 315 Amp-hr LiFEPO4 bank; the easiest thing is to see how much it outputs with a current clamp at the input of the battery bank.

https://www.amazon.com/UNI-T-Digital...xEALw_wcB&th=1

As Porschedpm had suggested you can install a battery Monitor and get a good idea of capacity as well as voltage and amps into the battery bank.

It is difficult to get the State of Charge of a battery without understanding how charging and discharging is affecting (i.e. through internal resistance) your battery terminal voltage measurements. If you are monitoring battery voltage from the alternator all bets are off.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Your Solar Charge Controller, a 120V to 12V DC battery charger and a DC-Dc convertor all have one thing in common. They all have a lithium battery charging interface. They only differ in where the power is coming from (solar, vs shore power vs alternator).

In the Renogy 40Amp DC-DC manual they have absorption voltage levels programmable for a Type 1 (13,12.8 and12.6v ) and Type 2 (14.6, 14.4, 14.2. and 14v). The LiFEPO4 is the Type 2 category. To properly charge LiFEPo4 you generally need more than the 14.0V you say your alternator is supplying (even if that is at the battery terminals)?

Quote:
Originally Posted by Sloya View Post
Right now we are in the winter season and the solar is keeping up with charging duties while the SMB is parked. On a good day in full sun the solar charges approximately 50 Ahrs and on a short day about 21 Ahrs.
At full sun your 200W system, is only delivering 10amps? It seems the Zamp charger is PWM. I regularly get close to 30 amps out of a 435 watt used panel with a MPPT charge controller. That is probably about 50% better conversion efficiency.

These are a good deal by top-name company that should noticeably increase you solar production.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Quote:
Originally Posted by Sloya View Post
In Summary, I was able to make the switch to Lithium without any additional major expenses except for the batteries themselves. Having equipment that was compatible eliminated any hardware changes that would have pushed the price higher. During solar charging the battery voltage goes as high as 14.4v but averages 13.3v and goes as low as 12.9v during high use. When using the coffee maker with 85 amps being used the voltage goes to 12.4 as the lowest and as soon as it stops it shoots right back to 13.0v. I find the controller electronics works better with the built-ins appliances in use. I know this report makes it all sound simple but believe me when I say I moved very
cautiously, reading everything I could find on the subject before making the battery purchase. Once this was done it was game on!

I hope you find this informative thought provoking, it works for me.
Your Solar charger despite being PWM knows to charge at 14.4v well above what is available from your alternator. If it drops to 13.3v it is because of pretty heavy loads exceeding you solar charge currents. With an MPPT mentioned above these voltages should rise closer to the 14.4 level.

At 13.0V, SOC~20-30% and apparently enough to handle an 85 amp draw but it is the very low side. The LiFEPO4 SOC chart starts to drop precipitously at 12.8V and by the time you are at 12V SOC~10% . It is not good to be running at these low levels.

Generally, I think that you have improved your situation with Lithium probably more usable Amp-hr capacity (than your older AGM batteries, and faster charging LiFePO4 for the properly configured solar charger.

That said, depending on your system voltages, the MPPT is superior to the PWM MPPT solar charge controller. Finally, the alternator charging is unverified as such (no charging current measurements) but based on other circumstantial evidence it is likely not very effective without DC-DC charger.

Finally, your 21-50 Amp-hr daily solar replenishment can be used to approximate your daily consumption requirements corresponding to 6.7% and 16% respectively as %SOC for a 315 amp-hr battery bank.

Nowhere have you said directly where this minimal daily pattern is riding (top, middle or bottom of the SOC?) except when you said that your battery gets occasionally down to 13.0 (about the bottom).

The bottom line is you have much more battery (315 amp-hr) than charging capacity (Solar, Alternator) or for your usage pattern (21-50 Amp-hr).

Regards,

PS: if you are wondering I am an EE in the process of designing my own solar/battery system. Just this week have been testing two sets of 300 Amp-hr AGM batteries to couple with 200 Amp-Hr DIY LiFePO4 to handle 12V Rooftop Air Conditioner loads.
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