First Time Poster, Long Timer Reader. Engel MT-45 Power Question

[RaptorCoastie]

Hello everyone,

As the title says, I've been coming to this forum for quite some time, just to read, gather information, ect. But I never made an account and posted until now. Long story short, I'm planning a trip with my long time girlfriend up to the Arctic Circle from Northern CA in April-March of 2018 just before I get out of the military. My current truck is a Ford F250 and I use that for weekend/3-4 day excursions around here, but I'll be working my way into a Ford Raptor later this year. That will be the truck we'll take up there. It should be an amazing time.

But I have a question regarding powering an Engel MT-45. I plan to get a second battery to run any auxiliary items off of since it provides added security over a single battery situation. But I want to make sure my power situation is going to be okay for the trip/running the fridge. So far, I have this set up:

Dual batteries under hood (Optimum Yellow Top. Currently run two, and love them)
National Luna Dual Battery Kit
1500 watt Sine Wave inverter mounted inside the cab behind the rear seats (Direct wired to second battery)
Two power outlets run to the driver side rear bed area, where the Engel MT-45 sits

Now the idea would be that while the truck is running the alternator would work with the Nat. Luna system and charge the batteries, and the fridge would get power via the inverter plug in the bed, which is again, wired right to the second battery. But when I turn the truck off, for say 24 hours, what is the best and safest means of powering the MT-45?

Do I just turn the truck on and let it idle for 15 minutes ever 12 hours? Or plug the MT-45 into the Yeti 400 solar generator? I know the yellow top can probably handle powering the Engel for maybe 3-4 days without the truck ever turning on, but I want to be as safe as I can since I'll be in some semi-remote places at times.

Any suggestions or critiques are welcomed. Or let me know if there's an entirely better way to go about this whole system. Thank you!

 

[AndrewP]

Sounds like your battery and charging system is in good shape.

I would not run the MT45 off an inverter. Even a decent inverter with it's conversion inefficiencies and heat generation, will waste 25%-50% of the power consumption of the fridge. That's nuts. Just wire the 12 volt side of the fridge directly to the #2 battery. If you're driving every day, you won't need to do any other charging. On days you sit, you can either use solar, or if you must, run the truck for an hour or so to charge the battery.

I've measured the power consumption of my MT45 and it's 15-25 amp hours daily depending on ambient temperature. So you could easily go 2 days without running and still not take the battery down too far. If you can supplement with solar power, it sounds like you're golden.

My general bias is that for tiny systems of 2 batteries (like a typical SUV install) is that inverters are evil due to their excessive power consumption anytime they are on (even without a load!) and should be avoided at all costs.

 

[RaptorCoastie]

My general bias is that for tiny systems of 2 batteries (like a typical SUV install) is that inverters are evil due to their excessive power consumption anytime they are on (even without a load!) and should be avoided at all costs.

Awesome. Thank you for the input. So I could just wire the 12V side all the way to the second battery, or rather have a fused 12V lead coming into the bed from the second battery and connect there.

In regards to not using the inverter, I'd still like to have it with the truck, even though I may not use it for this scenario. Since I have a Ford truck, I have the upfitter switches which make wiring rather simple. Maybe I could put the inverter on one of the higher amped upfitter switches, so in the event that I do need more power for something inside the truck for a short time, I can flip an upfitter switch, turn on the inverter, in turn powering anything I need. My only concern would be wiring and fusing at that point. Maybe a solution to having an inverter "on" 24/7 even when not in use.

 

[DiploStrat]

...

Do I just turn the truck on and let it idle for 15 minutes ever 12 hours? Or plug the MT-45 into the Yeti 400 solar generator? I know the yellow top can probably handle powering the Engel for maybe 3-4 days without the truck ever turning on, but I want to be as safe as I can since I'll be in some semi-remote places at times.

Any suggestions or critiques are welcomed. Or let me know if there's an entirely better way to go about this whole system. Thank you!

Ouch! There are a lot of things you ought to consider, starting with this: http://d26maze4pb6to3.cloudfront.net/optimabatteries/1213/4333/7097/Battery_User_Guide.pdf

If you want to use Optima batteries, your second battery should be a Blue Top, not Yellow Top.

Beyond that:

-- A lot of folks report issues with National Luna. You may want to look a Blue Sea as a US sourced alternative.

-- Inverters suck power; avoid them if you can. Use the smallest inverter you can get away with.

-- Reread the manual on charging a lead acid battery; it takes hours - 15 minutes does nothing.

-- Reread the manual on charging a lead acid battery; you don't want to wait days, you want to recharge immediately. Look into solar.

-- Reread the manual on charging a lead acid battery; there is a reason for the 50% rule.

If nothing else, read the relevant posts on this forum, they contain a lot of useful links. You have time, use it. Don't wait until you are out in the bush to discover that you have undersized your system or don't know how to care for your batteries.

Have a great trip!

 

[RaptorCoastie]

Hi Diplo,

I'm not sure why you say a blue top is better suited for my secondary battery. Even after re-reading Optimas pamphlet, all options still point towards a yellow top being the better option.

Yellow tops are typically used for vehicles with sound systems, a lot of electronics (OEM and aftermarket), winches, inverters and just generally in vehicles which have a copious amount of electronics and need a deep cycle battery that can withstand being deeply discharged better than a standard battery. Literally all things I have and will have on the next truck as well. So I'll most likely be going with a dual yellow top scenario like I'm currently running.

I will look into Blue Sea as I've heard decent things about them as well. What're the issues people are having with National Lunas DBS?

In regards to your last three points, if I were to use a yellow top, which is a pretty robust deep cycle battery, and after having experience with two of them in my current truck, I have confidence they can run an Engel with 25ish amps a day (Most likely less due to the cold ambient temps) for at least 2-3 days without hitting anything too dangerously low. And given that it's a deep cycle, I'm again not too concerned. But that is why in my original post I mentioned I have back up options such as the Goal Zero Yeti as my solar option and Generac iQ2000 as my gas generator option.

Since seeing people being pretty wary of inverters, I may reconsider my 1500 watt inverter option. If anything, just putting it on a switch so it remains off when not in use, not just on and in a "standby" mode. Should hopefully significantly reduce any draw. And only using it when the vehicle is running should be another safety practice.

 

[Martyn]

I'd have to second the idea of not running the fridge off an inverter. Leave the inverter off when not in use, use the inverter as little as possible, only use the inverter when running the engine, best of all leave the inverter at home. I've seen more people kill batteries with inverter use than I care to mention.

The National Luna is a good dual battery system, the biggest problem I see with any dual battery set up is either people don't understand them or people haven't spent the time needed to understand the system. Not to say that elements such as solenoids can't or don't fail but the majority of issues we see are with fuses blowing, wires not being connected tightly, incorrect wiring, or failed batteries.

We put the draw of an Engel 45 at 28 amps, this comes from research we did running the fridge for 3 months 24/7 and recording the draw. A 60 watt panel will provide enough power with 8 hours of good sun and a few hours of partial sun to provide enough power for the fridge.

You seem to like Optima batteries and if you are confident with them go for it, they are just not my personal favorite.

 

[jonyjoe101]

how big is the yellowtop? I went to the optima website and their biggest yellowtop was 55ah.

From my own experience with a 75 ah agm battery, I never got more than a day of 12 volt refrigerator use out of it. Once the battery voltage goes below 12 volts, the fridge starts misbehaving. With the fridge set to 40 degrees, a danfoss compressor fridge will use about 25 amps in a 24 hour period.

The goal zero 400, only has a 33ah battery, so that will at most give you half of day of power. And the 20 watt panel that goal zero uses only provides 1 amp of charge power which is not very comforting.

But if your going into a remote area you do need a solar panel, even the 20 watt would be better than nothing. Worst case scenario you leave your lights on and all your batteries are dead because the fridge drained them, hooking up a large enough panel to your start battery and a few hours of sunlight should be enough to crank you over. The situation happened to me and the 240 watt panel I got on the roof of my van saved me that time.

 

[DiploStrat]

Do your Homework

Do the research.

While scholars differ on which battery isolator/combiner they prefer, as noted by Martyn and others, most dual battery systems fail due to inadequate wiring, poor installation, etc.

As one battery manufacturer's rep put it, "Batteries don't die, they are murdered!"

-- A refrigerator is just about the nastiest load you can put on a battery as it ALWAYS pulls more than specced and it pulls ALL the time; all day, all night. You want a true deep cycle battery, not a "dual purpose." Reread your Optima literature. Big car stereos are not a serious load, a refrigerator is.

-- Most people simply slap in the battery that will fit, rather than a battery bank big enough to carry the full load. Sizing the battery bank is the first, essential step. Get that wrong and nothing else matters.

-- Too many people don't understand that a lead acid battery hates to be run down and wants to be under charge all the time. Also, lead acid battery MUST be fully recharged or else it will lose capacity over time. A full recharge requires high voltage (which your Ford can probably supply) and a long time. 15 minutes from time to time does nothing - you need solar or a generator.

Were I thee, I would:

-- Carefully size my battery bank, using Martyn's numbers, not yours.

-- Use a true deep cycle battery, not a dual purpose battery.

-- Install at least 100w of solar or carry a genset.

 

[Ducky's Dad]

If you want to use Optima batteries, your second battery should be a Blue Top, not Yellow Top.

Well, yes and no. Per Optima Tech Support, the Blues with the dark gray case are electrically identical to the Reds. The Blues with the light gray case are electrically identical to the Yellows. The only difference between the Blues and their corresponding Reds and Yellows are that the Blues have an extra pair of studs on top. Some Optima dealers don't know the difference, so be careful if you buy Blues. Your Yellows should be fine. I'm running an Indel B 50 fridge on a pair of Blue dual purpose (i.e., deep cycle) Grp 34 Optimas, and it works fine in nasty conditions. I have two Blue house batteries because much of my use is in AZ desert summers, and I can keep the Indel frozen all day (-21C), but I need to recharge to keep things frozen the next day when ambients are around 110+F. House batteries are isolated from starting battery, but I can combine everything easily with a dash switch.

 

[DiploStrat]

... The only difference between the Blues and their corresponding Reds and Yellows are that the Blues have an extra pair of studs on top. Some Optima dealers don't know the difference, so be careful if you buy Blues. Your Yellows should be fine. I'm running an Indel B 50 fridge on a pair of Blue dual purpose (i.e., deep cycle) Grp 34 Optimas, and it works fine in nasty conditions. I have two Blue house batteries because much of my use is in AZ desert summers, and I can keep the Indel frozen all day (-21C), but I need to recharge to keep things frozen the next day when ambients are around 110+F. House batteries are isolated from starting battery, but I can combine everything easily with a dash switch.

As always, I defer to Ducky's Dad for all things Optima. He has them and gets good results with them. I prefer true deep cycle batteries, but then Optima's "Dual Purpose" may be a true deep cycle.

 

[verdesardog]

All optima's with dark cases are dual purpose and light colored cases are true deep cycle. I have two light colored case blue top optima's for my trailer with two 100 solar panels to keep the charged up and run lights after dark. The only thing using current in the day is a Engle MT27 fridge, 2.5 amps when running.