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Old 03-13-2022, 07:46 PM   #1
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Thoughts on Lithium System

I appreciate the experts on this forum and am hoping I could get some feedback on my planned battery system.
I am interested in running a microwave to make cooking on the go easier. I got the smallest 700W microwave I could find. My single group 31 is not enough to run an inverter for any reasonable amount of time, so I have been looking into a lithium conversion. The existing setup meets our needs for the most part as-is except for these new potential loads. Wouldn’t mind having a bit more capacity for the cold nights camping in November where the furnace is running a lot, or to feel good about keeping the fridge on a colder setting.
The van is pretty much how it came from Sportsmobile. I have drawn a “before” diagram based on how I understand it to be set up.
We don’t stay put for too many nights at the same place, often on the go to the next hike, sight, etc. I have a 100W solar suitcase that I have connected directly to the house battery on the occasion where the van will stay put camping for a few days. The van currently has the standard progressive dynamics to charge from shore power. It’s inconvenient for me to charge at home because I can’t park the van near my house because it blocks the driveway and would have to run 150’ of extension cord. So, my primary charge mode is and would be off the engine as most of our destinations are at least 30 minutes from our house.
I upgraded the alternator in 2019 to a 200A unit from Nations (though it’s not one of the crazy versions).
With that said, I have a few questions related to my tentative “after” setup as shown.

1)Progressive dynamics says that the PD9100 will charge lithium with the Charge Wizard by pushing the button. This would be ok to me since I don’t plug in to shore power too often and would just push the button to start the charge. Would this work on this application?

2)Is the 50A Kisae appropriate given the anticipated size of battery bank, alternator, and existing wiring? Could I get away with sizing down (I think there is a 30A version).

3)Do I need to wire into the ignition switch t okeep the Kisae from running down the starting battery,or is there some other protection built in?

4)Do I have my auto transfer switch in the right place?

5)Is there anything major wrong here? Is there a better way to do this?


I will plan for appropriate fuses/wire sizes and I also understand that the solar panel won’t charge this system fully in a day.

Also interested in hearing from anybody with experience with the lower-priced lithium batteries available on Amazon. Hard to justify paying 2x as much for a BB or Relion in my simple setup. Thinking maybe Chins or Eco-worthy (the Eco-worthy 150Ah will fit in the spot where my lead acid is right now I think).

Thanks in advance.
-Mike
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Old 03-13-2022, 08:29 PM   #2
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1)Progressive dynamics says that the PD9100 will charge lithium with the Charge Wizard by pushing the button. This would be ok to me since I donít plug in to shore power too often and would just push the button to start the charge. Would this work on this application?

I would personally stay clear of this option.

2)Is the 50A Kisae appropriate given the anticipated size of battery bank, alternator, and existing wiring? Could I get away with sizing down (I think there is a 30A version).

I don't believe there is a good enough cost saving on going down to 30 amp version. For a 200 amp Lithium bank you could charge up to 100 amps, so a 50 amp version would still work with your 100 amp solution or 200 amp solution.

3)Do I need to wire into the ignition switch t okeep the Kisae from running down the starting battery,or is there some other protection built in?


The ignition wiring for the KISAE DMT1250 is for if you have a smart alternator ( it lowers the acceptable voltage range). The DMT1250 does stay active until it drops below the voltage threshold (this is much like a ACR disconnecting at the low voltage) I found this somewhat annoying but certainly not the end of the world. I have isolated the input with a ignition controlled relay, and can supply information on how it can be done.

4)Do I have my auto transfer switch in the right place?

To be honest I would just look at a inverter that has a built in auto transfer switch. For that matter you could purchase one that also has a built in charger, and then no need for the PD9100

KISAE, BIC1220080

or

Xantrex Freedom XC 2000 Pure Sine Inverter/Charger

5)Is there anything major wrong here? Is there a better way to do this?


Battleborn batteries are pretty reasonably priced Lithium batteries with good support. I would question some of the cheaper alternatives.


-greg
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Old 03-14-2022, 05:44 AM   #3
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I should also add, that in choice of batteries you need to look at the max discharge rate of the battery. This is pretty much limited by the BMS of the battery. So a 100 Amp-Hr Lithium battery may only allow 100 amp continuous discharge. So you need to make sure you size for your worst case use. In this case the 2000 watt inverter you plan on using.

-greg
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Old 03-14-2022, 10:10 AM   #4
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You should explore Will Prowse's Youtube channel for recommendations and information. He does battery tear downs of all batteries he reviews (even Battle Borns) and tests. Here's the link to his channel:

https://www.youtube.com/channel/UCoj...q8kmJme-5dnN0Q

And here's a link to some info he's posted on battery recommendations:

https://www.mobile-solarpower.com/li...batteries.html

Note that some of the info, like "out of stock" and pricing might be a bit outdated.

One of the key things he's found missing in some low cost batteries is low-temperature charging cut-off. And in some of his teardowns, even when it exists, the placement of the sensor is inappropriate. Unless you live in a very cold environment, heated batteries aren't necessary but low-temp charging cut-off is.

In a nutshell, I wouldn't buy a LiFePO4 battery that hadn't been positively reviewed by Will following a teardown.
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Old 03-14-2022, 11:12 AM   #5
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Greetings Mikerson,

My eyes perked up when I saw your project here. I did a similar upgrade to microwave/lithium with very similar goals about two years ago. At the time I was going to wright up a build thread here but also at the time there was a literal flood of house sized, 12k dollar, Bluetooth enabled, off grid power system in every sprinter van, posts all over social media and YouTube . So I thought no one is going to care about my little microwave in a old van post. Fun fact it all started with buying a 69$ microwave and ended up with what Mrs. ShuttlePilot calls my 3000$ microwave.

I'm sending you this in an effort to give some real world feedback to help you and others make great design decisions. First I will say that my system works well for us but I am aware that I'm pushing the limits and isn't ideal. This is just for your reference.

The equipment

Sharp Carousel 700 watt microwave.
(I recommend)

2 BattleBorn 100Ah batteries
(I highly recomend if your budget allows. Especially if your going to be running your batteries near the maximum current levels. i.e. a microwave)

Magnum Energy mms 1012 1000watt inverter.
(I am a proponent of heavy iron transformer inverters vs high frequency types. This is based on lots experience of HF inverters failing well under their rated capacity. I also am "getting away with" running this little 1kw beyond it's rated capacity for the microwave. More on that below)

Sterling Power BB1260 DC to DC Converter 60 amp
(Works for me with conditions and I don't recommend)


Nations 270 XP Alternator 270 amp capacity
(works fantastic so far but I've heard on the internet bad luck with some, ymmv)


Lots of larger cabling, ground bus, lugs, etc
( I took this opportunity to improve cabling and grounding from the alternator, to a new main ground bus, to moving the batteries to inside the van, to the Dc to Dc converters, yada, yada since I'm now trying to move larger amperage currents around the van.



So, just a 69$ microwave.



Anyway here is what I wanted to offer you.
I warmed up my coffee in it this morning to double check this before posting.

700 watt microwave consumes 1040watts at 120 volts AC (measured with kill-a-watt)

Batteries at 96% (shown at Bogart meter)
batteries are chilly this morning aprox 40*f

batteries start volt 13.2

batteries under microwave load volt 12.2

battery current 120 Amps/1460watts to run microwave
(shown at Bogart meter)

I double checked the math a few ways and it adds up. Note - the math shows that the inverter is running at 70% efficiency. This is not normal. Under light loads I see 85 ish. I assume the inverter is this inefficient due to operating it so far beyond it's full duty rating and though I have comically large cabling for power and ground to the batteries, there is still a sizable loss there as well. So yea, to get 700 watts into my frozen burrito I need to burn another 700 watts in losses. Also it is interesting how much longer a 700 watt microwave needs to run in minutes to heat food compared to the counter top or especially an over the stove mounted type. So, regarding battery capacity, cooking is not 700 watts for 3 minutes in home microwave it's more like the full 1460 watts for 8 minutes. Just keep your expectations within reason

Final thoughts, I hope this gives a point of reference on real world usage. My recommendation is to be aware if you are planning to run your batteries near their rated current capacity and if you are I wouldn't skimp on quality of battery. Budget in to improve your cabling positive and negative, to and from everywhere. I feel my setup is the minimum capable to run the smallest of microwaves. I see why people now days install power grid sized lithium systems in RVs in order to have house sized appliances.

- Eric
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Old 03-14-2022, 11:40 AM   #6
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Great feedback and sharing of real world experiences.

ShuttlePilot - it might be interesting to do the same evaluation and measurements but with the engine running at rpm's high enough for the alternator to compensate for the voltage drop.

Our rig is AGM based and we use our microwave frequently. Our 360w solar panel can cover part of the current draw during a sunny day but we almost always start the engine to have the alternator keep the voltages up in the 13 range. Without the alternator contribution, the battery voltage drops into the 11.8 vdc range before recovering into the mid 12's.

While I am okay with this for a few minutes I am not comfortable going for more than five. This is ~ 100 amp/hr draw rate. To protect the batteries I usually try to keep draw rates at no more than 15 amps. This is on a 400 AH battery bank.
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Old 03-14-2022, 02:07 PM   #7
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1der, you caught me at home on one of those days when I've got five projects to do today and my mind wants to do this instead. I ran the junk because I'm curious, and answer your question. First, it sounds like your (1der) system is working great for your needs and expectations however for me the want to not have to run the diesel engine to run the microwave was a no go if I'm spending the money/effort on lithium. I could continue to use the portable Yamaha generator instead.
Here is what I just ran in the driveway.

Resting condition before test

- This run, vs posted above, is with the BB batteries much warmer, at least 70*F.
Batteries 100% charged voltage 13.4 solar controller in float regime.

- I have 280watts of solar on the roof, 50*F Ambient temp, in full sun, controller in Float voltage, delivering 4watts.

- Microwave off


Running Microwave running on solar (really ideal conditions)
- Solar delivering 205watts at 15.2 Amps, controller in MPPT regime.

- Batteries delivering 101 Amps at 13.2 volts indicated on the Bogart meter, 12.7 volts indicated at the inverter terminals.

- Microwave running normally as described in above post

- This is as they say "Money".


Running Microwave with engine running (idle and hi idle same, same)
- Batteries delivering 37 Amps at 13.4 volts indicated on the Bogart meter, 13.1 volts indicated at the inverter terminals.

- Alternator through Dc to Dc converters (2) delivering 51 Amps total. Alternator and starter batteries voltage stable at 14.5 volts in idle and 1200 motor RPM hi idle no difference.

- Solar delivering 15.2 Amps. (remember with a DC to DC converter the solar and alternator are additive as the house batteries and the starter batteries are isolated.

- Microwave running normally as described in above post

I didn't double check all the math there as with the motor running, variables in solar output, and the water starting to boil in the microwave, things were at they say "getting dynamic". Anyway all this also shows the limitations of a 12 volt system. That 1 more volt to 13 that lithium provides is a big jump in efficiency. Also how much temperature effects even low resistance lithium batteries. The above tests were, by just luck, run in really ideal conditions. Real world is it's 0530, 50 degrees inside the van, batteries are at 40% SOC and Mrs ShuttlePilot would love to have a warmed up creassaunt with coffee. I can do that now and most importantly, completely silently. I've thought that if I was to build another van I would consider moving to 24 volts cabin/house system.

Good fun, now I really need to get some stuff completed today.
- Eric
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Old 03-14-2022, 02:44 PM   #8
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Good data Eric. Microwave ratings are based on cooking power. So a 700 watt microwave takes more than 700 watts of AC power to produce the 700 watts cooking power. Usually somewhere on the microwave there is actual power usage data.

-greg
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Old 03-14-2022, 10:17 PM   #9
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Thanks to all for the thoughtful replies. Going to take me a bit to digest it all. My quick takeaway is that I have all the right “pieces” planned for my system, but may want to rethink which products to actually put into service.
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Old 03-16-2022, 09:30 AM   #10
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Few follow up questions.

Does anyone have a picture of the display/control panel that comes with the kisae bic1220080? I am leaning towards an integrated charger/inverter/switch as Greg suggested since it’s not that much more expensive when you add it all up.

Anyone aware of an equivalent to this kisae unit with lower power inverter? I only need 1100W as measured by running microwave. (But my searching has indicated that in general, inverter efficiency doesn’t start to crash until below about 15% of rated output, so 2000W may not be a big disadvantage)

Any comments on SOK batteries? They seem well built and supported.

The Chins (Chins’s?) are also recommended by Will Prowse (at least according to mobile-solarpower.com) and they have a unit with built in heating out. We cold camp and ski so need low temp cut off in the bms and preferably heating.
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