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Powering a small refer?

hardtop

hardtop

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Sep 13, 2020
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Las Vegas, NV
I've been using an ice-chest for a couple years as a full-time overlader and I'm graduating to a portable refer. I run a pure sinewave generator (Yamaha 2200) all day and will use that to power the refer but at night I turn the generator off. Since space is limited (in a car) and so is budget, I'm questioning if I really need a battery during that time. I have zero experience with refers and thought maybe I could crank the temp down during the day and let it thaw overnight.

The refer is an Engel MT45 and I will pack it with about 30 pounds of fatty rib eye or chuck steaks. The refer needs to be ice-cold to keep the meat fresh. I know it would be better with a battery, but I'm looking at the marine starter batteries lead-acid batteries at Orielly Auto Parts and some charger (not sure which?).

But if there are ways to make the temperature stay near freezing or to 40F and last through the night then I'm going that route. I also thought about buying one of those small jumpstart lithium battery replacements because of their size, but that probably isn't right nor is a starter deep cycle. Any ideas on the impact of leaving the Engel off just for overnight?

MT45F-U1CD-P-3_700x.jpg
 
Welcome to the forum hardtop!

Here is what the Engel site says about power consumption:

Power Draw Variable from 0.54-2.35 Amps (12V DC)

Now we get to the guessing part.

Let’s say it draws 1.5 amps average and you want to power it for 8 hours a night. That is only a 12 amp hour load.

My opinion? Forget lead. Go straight to LiFePO4. For weight, depth of discharge and lifespan it’s a no brainer.

To start with you could get one of these:


That MAY get you through the whole night and it may die before sunrise but it’s way better than a fancy cooler full of spoiled meat!

And a second battery if you want to be safe and rest your genny a bit.

After that it’s just deciding if you want to charge the battery via your genny or solar.
 
Welcome to the forum.

Using this as a basis for worst case:


2.35A/hr

24h * 2.35A = 56.4Ah

In all but extreme heat, you should use notably less.

Something like an Interstate SRM-24 for $120 has about 81Ah - more than enough to survive 24 hours without substantial damage and should be able to take several hundred cycles. Many more, if you only run it at night.

Guessing 30# of that luscious moo-muscle costs way less than $120 :)
 
JoeHam said:
Welcome to the forum hardtop!

Here is what the Engel site says about power consumption:

Power Draw Variable from 0.54-2.35 Amps (12V DC)

Now we get to the guessing part.

Let’s say it draws 1.5 amps average and you want to power it for 8 hours a night. That is only a 12 amp hour load.

My opinion? Forget lead. Go straight to LiFePO4. For weight, depth of discharge and lifespan it’s a no brainer.

To start with you could get one of these:


That MAY get you through the whole night and it may die before sunrise but it’s way better than a fancy cooler full of spoiled meat!

And a second battery if you want to be safe and rest your genny a bit.

After that it’s just deciding if you want to charge the battery via your genny or solar.
Click to expand...

That is a surprisingly cheap battery. Just the right capacity, size and budget. I'm not sure about charging it though. The cheapest Victron charger is $150 for the IP65. I'm not sure of what brands to look at that could be less money. Any suggestions?
 
Look at the lithium chargers on the same Amazon page.

$20 I think. This is budget stuff but worth a go for sure .
 
After reading the 200+ Q/A on that Miady battery at Amazon, the lead acid battery chargers that are LIFEPO4 compatible aren't a good first choice.

When the battery is completely depleted, the Shumacher charger won't charge it. The battery will need a reset which fully compatible LIFEPO4 chargers can do and the typical lead acid LIFEPO4 compatible chargers won't.

Another issue is charging voltages and charging algorithms are different compared to lead acid and the manual said absolutely nothing about LIFEPO4 specific charging algorithms. I returned it and bought this one instead. It is ony 2amp, but I'm hearing it is better longevity-wise to use less juice to charge it rather than more juice.

I originally wanted to charge my car battery and the lithium with one charger. If the car battery dies I'll stick the lithium charger on there and hope for the best, lol.
 
Yes, charging at a low amperage is called a low C rate and it’s a good thing.

That charger will be charging at 2/16 or a 0.125 rate which is fine. I use something very similar.

The battery BMS will cut off when it gets where it’s happy.

To egg you on further ? I would get two batteries, keep one charging via solar power, and rest the generator, maybe forever.

But then you wouldn’t have all the fun of oil changes and hauling gas around!
 
Believe me, I was close to upgrading the battery to the 36ah or getting two. But the size you first suggested is perfect. It will handle the worst case scenario of running the refer full bore at 100% duty cycle all night (8 hours). A likely scenario would be using only ~8ah of the 16ah and I typically only sleep 7 hrs so there is plenty of energy buffer for error.

My budget for the refer was $500 and I doubled that so I didn't have much to spend on a battery. I've been wanting to get the Lithium cells from Winston or CALB(?) and learn how to do the custom bms and geek out on it. There is a big ramp-up for that. I think just getting an el-cheap-o lithium with BMS and a charger to get my hands dirty is a good first step. I'll begin to feel the power and excitement of LIFEPO4 as an amature and look up to the big kids at the deep end of the pool.
 
Yes the LiFePO4 Miady is a good gateway drug ?

When you look at the cost, size, depth of discharge, weight and lifespan it’s impressive.
 
The Amazon seller responded to my charger question asking if that Shumacher was compatible and if not, what chargers are compatible. That battery needs a 14.6v lithium charger and the second charger I picked only goes up to 14.4v, but there is a tolerance of +/- .2v.

However, the battery is rated at .2C which is about 3.2 amps. That charger is only a 2amp charger and it would take 12hrs to charge and a 3amp charger would take 8hrs to charge. (hrs)=(1.5 x Li-Ion pack capacity, Ah) / Charging current.
 
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The battery arrived today at 13.8V and I put a Dakota brand 3A charger on it. The charger ran for about a half hour and indicates a full charge at 14.28V, below the 14.6V +/- .2V specs. I guess the 14.28 is all the charger can put out? It is cheap asf and I kicked myself once I saw the quality, but if it works that is all I need. I needed to cut corners so it looks like I cut myself a few tenths of a volt somewhere. I'm not sure what the impact is since I'm a newb.
I put broccoli in the refer at 0F and plan to run it overnight and check the battery voltage in the morning.

I set the battery saver feature on the fridge to power down at 11.5V, the highest setting. It would go down into the 10.xV but I have no idea what that voltage correlates to in depth of discharge. How can I determine the depth of discharge using a volt meter and specs? Also, is the low(ish) 14.28V reading on the Miady an issue?


kYusCiG.jpg




7EGueDz.jpg
 
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Voltage is not a good indicator of SOC for LiFePO4 due to the flat discharge curve so a volt meter is not much help there.

I treat my Miady battery like crap. That said here is what I would do.

Leave your charger on it overnight. Even a small amount of current adds up over time.

Then discharge it until it’s BMS protects it. But don’t let your broccoli spoil! For a better test you might put something with a greater heat latency in there like a jug of water during a test.

If you really want some capacity testing you will need to coulomb count but you probably don’t want a Victron SmartShunt for this budget setup.

Let me find the el cheapo one I use to test.
 
Meanwhile see here:

diysolarforum.com

Miady testing

Anyone tested this batteries. https://smile.amazon.com/dp/B07X7MD2JK - the 16AH versiom. Although price has gone up, it seems too good be true.
diysolarforum.com diysolarforum.com
 
I can’t remember where I got it years ago but I put Anderson Powerpoles on it since it is not bidirectional. I put it between the charger and battery to measure power in then flip it around for a discharge test.

The only problem with discharge is that the meter has no memory after the battery shuts down so you have to pay attention near the end.

True confession: I ran all my LiFePO4 batteries for years before I ever started capacity testing so don’t drive yourself crazy with the testing.

It might be more helpful to just measure how long your cooler runs before the battery shuts down during different ambient temperature tests.
 
JoHam said:
I can’t remember where I got it years ago but I put Anderson Powerpoles on it since it is not bidirectional. I put it between the charger and battery to measure power in then flip it around for a discharge test.


The only problem with discharge is that the meter has no memory after the battery shuts down so you have to pay attention near the end.


True confession: I ran all my LiFePO4 batteries for years before I ever started capacity testing so don’t drive yourself crazy with the testing.


It might be more helpful to just measure how long your cooler runs before the battery shuts down during different ambient temperature tests.
Click to expand...

JoHam said:
Voltage is not a good indicator of SOC for LiFePO4 due to the flat discharge curve so a volt meter is not much help there.


I treat my Miady battery like crap. That said here is what I would do.


Leave your charger on it overnight. Even a small amount of current adds up over time.


Then discharge it until it’s BMS protects it. But don’t let your broccoli spoil! For a better test you might put something with a greater heat latency in there like a jug of water during a test.


If you really want some capacity testing you will need to coulomb count but you probably don’t want a Victron SmartShunt for this budget setup.


Let me find the el cheapo one I use to test.
Click to expand...


I know good advice when I hear it and that right there was good advice :) I blew a soldered circuit on the multi-meter years ago by giving it too much current so I can't measure draw in or out of the battery and then use that measurement with time to get amp hours. It has USB data logging and drivers for Windows. Plus charts and graphs.

Would using time to recharge as a measurement produce a ballpark AH figure for battery capacity after a full depletion? But that would assume I'm really getting 3A into it and I don't trust the charger to be accurate. If I get 16AH back in then all is good.

If the fail safe trigger in the BMS turns off the battery after it is depleted, would I need a special charger to reset the BMS? I just have that Dakota charger and its features list did not include a BMS reset feature. Is that reset a common feature LIFEPO4 supported chargers all have or would Dakota list that if the charger had it? Dakota has been unresponsive so I'm not sure if their charger will bring the battery back to life from the dead.


Below is Miady pic having the cigarette lighter and USB power center by its side with the refer plugged in. I need to attach the power center somehow, probably with double stick tape so I can rip it off in the future. I've excluded using 4 long mounting screw to fasten it. No pilot holes are going in either, lol.


x07LOmE.jpg
 
Thanks.

Some batteries lose their mind after a BMS shutdown and have some elaborate wake up procedure. My Miady gets run to shutdown every time and it automagically comes back to life every time I charge it up. I don’t think you’ll have any problem.

I found what looks like my meter here:


The Miady terminals are called F terminals. I crimped up a short F to APP (Anderson Power Pole) jumper and it is shrink wrapped onto the Miady forever I hope. All of my stuff has APP’s on the power cord so it can all plug into whatever I need. IMHO it’s worth standardizing all your stuff like this since it costs a little time up front and saves you time for the rest of your life.

I would immediately cut off all alligator clips and convert to APP. There are too many problems with alligator clips to list here.

APP’s of this shell size come in 15, 30 and 45 amp sizes depending on the wire size used. Always upsize when in doubt.
 
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If you don’t want to make your own ebay and Amazon are full of vendors who will:

Amazon.com: Valley Enterprises Battery Cable F-Type Terminals 12AWG Wire with Anderson Powerpole Connectors 45 Amp: Automotive

Buy Valley Enterprises Battery Cable F-Type Terminals 12AWG Wire with Anderson Powerpole Connectors 45 Amp: Connectors & Adapters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com

Or you can get the tool and some connectors and go to town:


Amazon.com: Anderson Powerpole Connectors 10 Pair Genuine: Electronics

Amazon.com: Anderson Powerpole Connectors 10 Pair Genuine: Electronics
www.amazon.com
 
I’ve been using a domestic CFX95. It sips power and takes 12/24v DC as long as there is mass inside the cooler.
If there isn’t stuff inside, you’ll waste more power. (So stick a gallon of water in there for good test numbers!)
Really, I would expect similar load draw from any compressor driven unit.
I’ve been keeping half my CFX at at around 2f - deep freezing for a couple of months to test the draw. And performance. It averages something like 40w when the compressor is on at 12v.

If you’d like some really good data, consider grabbing a victron Bluetooth smart shunt. For $130, you’ll have nice data with graphs over timer. (Worth it for protecting those steaks IMO!)
 
The Miady 16ah LIFEPO4 battery is performing good. It has more than enough energy to power the refer overnight and well into the next day. Today I pushed the draw time further and harder with a 100% duty time for hours after wake at sunrise. At that time it was 68F and today's high was 97 F here in the Mohave according to my Volt. It had 26 pounds of beef, broccoli and a warm (68F) 3 liter Arrowhead water bottle in there.

Aside from that, the Miady initially on first usage would only take 14.28v before the charger would claim it was finished. From there, I drained the battery to 10.5V and began a full charge and it completed charging at 14.31V. I did another drain down to 12.66V and rechargeed, but there were no gains at the top end. It was still topping off at 14.31V.

Because of the ambient temperature today the refer had to work harder and I had enough time to test the battery saver feature on LOW which stops the refer power draw at 10.5V. But what happened was I approached the refer and it was off. The Miady showed 1.1V and I'm guessing the low voltage reading was probably the BMS fail-safe protection taking action.

I put the charger on it and boom, it started charging again. There was no pain or suffering trying to bring the battery back to life to begin charging. As a test to reproduce the behavior minutes later, I powered the refer back on and watched the volt meter to see how/why the voltage was not ~10.5V as expected.

The result was once the volt meter hit 10.5V, the battery and refer stopped producing at the same time quickly after that voltage threshold. The battery voltage was at an uncharged ~10-11V at the beginng of the test and the decline in voltage was a qick slippery slope downhill because of lack of energy. I think the refer and volt meter were a few tenths apart on the battery voltage measurement and as a result the refer didn't turn off right at at 10.5V and coupled with the rapid decline in power that pushed the voltage limit down to 10.0V quickly which is where the BMS fail-safe trigger is set to fire. That is my theory at least, lol. The refer could have shut off by design and it was just a timing issue where it seemed like the battery powering off kicked the refer off.

I appreciate the tips, they have helped me realize I need to exercise the battery to get it excited about life. The battery is a lot like like life. Exercise it to keep it healthy. I think I might be able to squeak a 14.4V top end out of it by working it good a few more times. It needs some long runs. Some some long hard runs of drain and recharge cycles in the Mohave Desert. This is a good high temp boundary test too so this summer when it gets hot up at high elevation in the forests, I can do my work and not have to worry about battery/charger temps or wondering if I'm going to start smelling burnt chips, burnt insulation or burnt plastic.
 
Just be careful about letting it sit at cutoff for long. Recovering an over discharged battery is a pain.
 
hardtop said:
I appreciate the tips, they have helped me realize I need to exercise the battery to get it excited about life. The battery is a lot like like life. Exercise it to keep it healthy. I think I might be able to squeak a 14.4V top end out of it by working it good a few more times. It needs some long runs. Some some long hard runs of drain and recharge cycles in the Mohave Desert. This is a good high temp boundary test too so this summer when it gets hot up at high elevation in the forests, I can do my work and not have to worry about battery/charger temps or wondering if I'm going to start smelling burnt chips, burnt insulation or burnt plastic.
Click to expand...

It's not the exercise per se, but it's likely top balancing that's going on. One of the cells is hitting HVD before the others and tripping the BMS. Deep cycles aren't going to to anything more for you than shallow cycles in terms of driving the peak voltage higher, and it's unlikely that you're making more than a 1-3% difference in total capacity.
 
snoobler said:
It's not the exercise per se, but it's likely top balancing that's going on. One of the cells is hitting HVD before the others and tripping the BMS. Deep cycles aren't going to to anything more for you than shallow cycles in terms of driving the peak voltage higher, and it's unlikely that you're making more than a 1-3% difference in total capacity.
Click to expand...
There may not be much to gain, but this Miady LIFEPO4 battery has become more than a problem solver. Its like I have a new hobby now. A 3% gain just by using it feeds the fire inside.
 
willo said:
Just be careful about letting it sit at cutoff for long. Recovering an over discharged battery is a pain.
Click to expand...
I appreciate that tip. I will switch the Engel low battery cutoff to HI which is set to stop drawing from the battery at 11.5V. I'm guessing that number is a safe threshold to kick off the refer and keep the battery fail-safe mechanism from firing. I need to wait until tomorrow to test it. There is a lot of energy in that 16ah Miady and the refer is a fuel sipper.

I'm super happy with the battery for the price. I was originally thinking of lugging around a lead acid battery because they are convenient to buy at the local auto parts stores and less expensive. But the Miady is proving to be the strong winner in energy usage, space, weight, cost, recharge time and hopefully longevity.
 
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