Things I learned from Diplostrat at Expo East and the questions I still have . . .

Capt Jon

Observer
Diplostrat taught some electrical classes at Expo East, and I learned enough to understand (sorta) why my system wasn't working, but didn't get far enough in the time allowed to get very far into solutions . . . . It's progress to know what you don't know, right?

I was using a Nat. Luna power pack with an Optima Group 31 Yellow top in Dubai to run a National Luna fridge (Weekender 50). On almost every trip, the fridge would be screeching its low battery alarm 7-8 hours after I shut off the truck at night. (late model 70 series LC). (Fridge was packed cold and chilled overnight in the house before leaving, ambient temps usually in the 70-90F range at night. Fridge was usually set to -1* C, no travel cover, but plenty of ventilation. I worry about the sufficency of the insulation no the fridge because the outside was always very cold to the touch). My goal is to run the same fridge on short camping trips in the US, not that unusual I would think. Hopefully at a little lower ambient temps.

After listening to Fred's excellent presentation, my theory is that two things may have been hurting me:

(1) I simply never got the battery topped up due to the combination of low Toyota-specific charging voltages and the fact that my 30-minute commute was simply never long enough for the battery to spend enough time in the absorption phase of the charge cycle. So I was essentially never getting the battery over 80% charged. (optima G31 = 75AH, 80% of that is 60AH, and 50% of that is 30AH. But, even in Dubai, I am having a hard time believing the fridge was pulling 30AH in 7-8 hours).

and (2) I think the battery alarm on the fridge is much more conservative than I am. While I appreciate a conservative approach, I am willing to deplete the battery a little further than the Engineers at NL. I don't mind replacing the battery at 3 years instead of 5-6 if it gets me what I need.

The question becomes what to do about it?

I am back in Atlanta, and in another Landcruiser. I don't know, but expect that my 1990 FJ62 is not going to charge any better than my 2015 76-series did. My commute is actually shorter than it was in Dubai, so I am not likely to get much improvement there.

Things I am considering:

Dual batteries - Blue Sea ACR to keep them separate when not being charged. The NL box will still be around for horse shows, but won't live in the truck. So I can plug it into a charger between trips. A higher-capacity G31 battery - something in the 100AH range.

Pigtail - Fred mentioned a plug in pigtail that tricks the Toyota voltage regulator into giving a little higher charging voltage.

Solar?????? - I want something to top up the batteries during the week, and don't think I will be on the road enough, but then again maybe I will? A 30-minute commute is five hours of charging a week, plus whatever good I do on the drive back from camping trips. Shouldn't the charging be cumulative?

I am not stationary enough to need solar that keep up with a fridge for days at a time. I just want to get the battery topped up during the week so I am good for the next trip. Am I going to have to install a permanent panel on the truck? Am I better off just plugging it in at night? How is the rest of the world dealing with this?
If I am at a slightly higher voltage, will that be sufficient to keep an aux battery healthy and up to full charge?


Battery Charger at the house - Is my 40-year old Sears battery charger going to take care of topping up the batteries, or have I entered a world where that's suddenly not good enough?

I would love some advice/comments from the good folks here, but admit that I may not be able to tell the difference between the experts and the internet commandos.
 

DiploStrat

Expedition Leader
Some Ideas1.

Let's guess some numbers. The last time I was in Dubai, it was warm, but not like Djibouti (but I digress). Given that, what does the refrigerator draw?

The website claims 1.5 to 2.5A, so call it 2.0A per hour. (http://www.nationalluna.com/weekender50.htm) Call that 40Ah per day, rounded down a bit.

How much battery do you have? If we are talking about the same battery, Optima calls it 75Ah. (https://www.optimabatteries.com/en-us/yellowtop-deep-cycle-battery/d31t)

Sooooo, a full day's use will draw the battery down about 50%. You specified that the shut off was the Nat Luna monitor; I would guess that that would go off when the voltage drops to around 12v, but I have no way of knowing.

Guessing again, with a fully charged, new battery, you should be able to get at least 12 hours. The operative points are "fully charged" and "new." And of the two, "fully charged" is more important.

I would agree that the problem is simply that you were never charging the battery fully.

As they say in West Africa, "What to do?"

-- Raise your charging voltage and use a relay or switch. You can do this by playing round with diodes, like this: http://www.smartgauge.co.uk/alt_mod.html or by buying some thing like this: http://www.mechman.com/accessories/...e-voltage-boost-module-for-oval-3-pin-toyota/ (Note that there are 3 pin and 4 pin models.)

-- Use a battery to battery charger. CTEK, Sterling, and REDARC all make different models with different features. The REDARC rep (yes, they are now in the US) took me aside to show me a very slick 40A model: https://www.redarc.com.au/dual-input-40a-in-vehicle-dc-battery-charger The nice features of this unit are:

1. 40A and adjustable profiles
2. MPPT solar controller built it
3. Small, sealed, and rated for the heat of under hood mounting.

If you are looking to add solar, and you should, the one stop shopping of the REDARC or the CTEK D250S is a nice feature.

Solar really gets interesting when you have at least 150w, that is, enough to cover the basic loads (e.g. your refrigerator) and another 5A or so left over to actually charge your battery. Below that, it is hardly worth the effort if you have a refrigerator.

Charging over the week is not really cumulative as the battery self discharges a bit and the refrigerator is always running.

Any charger is better than none, as long as it is smart enough to shut off when the battery is charged. A more modern charger with the proper profile will be better, and probably safer as well as it will almost certainly have a true float setting.

You can download the slides and more here: https://diplostrat.org/documents/

Hope this is helpful. Others with more experience with the Weekend 50 and Optima batteries may have better comments to add.
 

john61ct

Adventurer
Get a real deep cycling bank. Optima is great at starting and marketing.

If the fridge uses 60AH per day, you need 70-80AH absorbed by the bank to replace it each day.

200+AH bank would be my minimum, no counting othet loads.

If you use dino juice for charging, to minimize runtime high CAR chemistry like LFP is ideal, maybe I hour each day is enough.

If lead go AGM, Odyssey Lifeline or Northstar, but for longevity takes 4-6 hours of charging every day to get to 100% Full.

Morning dino juice to 85% then solar for the long tail will do it.
 

Capt Jon

Observer
Thanks for your help and the quick response. Forgive me if it was inappropriate to call you out in the thread title, but it was intended as a compliment. I have never understood internet etiquette very well, and tend to just bumble along and hope my good intentions will prevent any offense.

Due to the problems I was experiencing, the fridge came out after each trip. The rough volt meter on the panel of the National Luna box would show some charging over the course of the week, so I am assuming some cumulative effect, but I don't know if it ever got to fully charged. Nor am I confident that instrument would have told me if it did. I wonder if there may have been some overhead from the NL box itself, but I can't be sure.

I think I'll probably start with the pigtail from mechman.

I will eventually add solar, so if I understand you correctly, the CTEC and REDARC units will perform the functions of both the Blue Sea ACR and a solar controller?

If that is the case, then I will "buy once, cry once" and start there instead of with the ACR.

Thanks again for your help.
 

DiploStrat

Expedition Leader
...
I will eventually add solar, so if I understand you correctly, the CTEC and REDARC units will perform the functions of both the Blue Sea ACR and a solar controller?

If that is the case, then I will "buy once, cry once" and start there instead of with the ACR.

That is correct - the right B2B will charge from both solar and the starter battery, the CTEK gives you 20A, the REDARC 40A. The biggest drawback to a B2B is that they are one way devices; a solar or shore charger connected to the camper battery will not charge the starter battery and you cannot use the camper battery to jump start yourself without some extra effort. (And one of the reasons that bi directional charging is so slick is that it greatly reduces the chance that you will have to self jump!)
 

Capt Jon

Observer
The ability to self-jump is nice, but not something I would sacrifice other functionality for. I have found jump starts to be both rarely needed and easily accomplished with the cables I will carry anyway. All the more so if there is a good (charged) battery 4 feet away. Bi-directional charging sounds great, but again, I have a hard time seeing it as a feature worth sacrificing for.

Would the Mechman pigtail still be necessary if using a B2B? My starting battery is happy enough as is, and the CTEK or REDARC would be setting the charge voltage on the house battery even if the alternator was coming in below the set value. (i.e. trading some amps for volts). So the mechman pigtail starts to look like more wiring (and hence another point of failure) that I don't need.
 

dwh

Tail-End Charlie
Even if you only used the fridge on weekend camping trips and let the battery charge during the week's commute, it wouldn't get the battery fully charged. Even with the diode. Even with the DC->DC charger. Even with both.

The reason is not so much about self discharge. That happens, but for most lead-acid batteries it's on the order of couple percentage points per month.

The problem is voltage vs. time vs. battery resistance. The closer a lead-acid battery gets to full, the more it resists (chokes off) the flow of current (amps).

To overcome that problem you either need a higher voltage, or more time.

Actually...both, because a higher voltage only helps so much. You can't go too high with the voltage, so the only way to compensate for the current being reduced is to give it more time.

Even if you use the diode to increase the voltage, at some point the battery voltage is going to be close to equal to the supply voltage, and the current flowing will be very little, and the only thing that will help is time.

The same will happen with the B2B.

By limiting the time, you'll only get the battery to a certain point (say 85%-90% SoC) and no higher. This will happen each day as you repeat the cycle. Starting from battery resting voltage, driving a bit and pushing the battery voltage/state of charge to a certain point, but not spending enough time to get the state of charge to move up any higher.

So no - the charging won't be cumulative.

You have to first push the battery voltage up, then hold it there for enough hours, letting the battery slowly absorb, to get the state of charge to move up past that first plateau and eventually reach 100%.

The main advantage of the B2B is a steady higher voltage (without it, voltage usually drops at engine idle). That steady supply of a higher voltage can shave a couple hours off the charge cycle.

But it still takes hours to get it done.
 

Capt Jon

Observer
Got it. No replacement for time. I either have to drive for hours or get those hours somewhere else I.e. solar or shore power.

B2B will assist with all of the above, but is not the answer in and of itself. With my driving pattern, I need some kind of permanent trickle at 14.4+v to tease the battery up to 100%.

The Mechman solution sounds like a waste of time because it won’t solve the problem. Even with more colts, I still need more time.

Thanks guys for the education.
 

DiploStrat

Expedition Leader
Even if you only used the fridge on weekend camping trips and let the battery charge during the week's commute, it wouldn't get the battery fully charged. Even with the diode. Even with the DC->DC charger. Even with both.

The reason is not so much about self discharge. That happens, but for most lead-acid batteries it's on the order of couple percentage points per month.

The problem is voltage vs. time vs. battery resistance. The closer a lead-acid battery gets to full, the more it resists (chokes off) the flow of current (amps).

To overcome that problem you either need a higher voltage, or more time.

Actually...both, because a higher voltage only helps so much. You can't go too high with the voltage, so the only way to compensate for the current being reduced is to give it more time.

Even if you use the diode to increase the voltage, at some point the battery voltage is going to be close to equal to the supply voltage, and the current flowing will be very little, and the only thing that will help is time.

The same will happen with the B2B.

By limiting the time, you'll only get the battery to a certain point (say 85%-90% SoC) and no higher. This will happen each day as you repeat the cycle. Starting from battery resting voltage, driving a bit and pushing the battery voltage/state of charge to a certain point, but not spending enough time to get the state of charge to move up any higher.

So no - the charging won't be cumulative.

You have to first push the battery voltage up, then hold it there for enough hours, letting the battery slowly absorb, to get the state of charge to move up past that first plateau and eventually reach 100%.

The main advantage of the B2B is a steady higher voltage (without it, voltage usually drops at engine idle). That steady supply of a higher voltage can shave a couple hours off the charge cycle.

But it still takes hours to get it done.

dwh just saved me a ton of typing! (Again!)

You may remember that I give three presentations, and that I mentioned that the most important one is the one on what it takes to charge a lead acid battery:

-- Time, and,
-- Voltage, and,

to quote my friend at Lifeline batteries, more time. Lifeline specs two additional hours of charge AFTER full charge. Most folks never drive that long, hence the importance of solar and/or shore chargers. Sorry I wasn't clearer, faster.

Part of the problem is that lead acid batteries are perverse beasts - as soon as you put them on charge, they start to develop a surface charge which raises their internal voltage. As that voltage, they will only take an ever smaller charge. The "absorb" stage of charging, hi-volt/lo-amp is intended to allow the charge to spread through the battery. Remember, it is a chemical reaction, not at all the same as filling an air tank or a gas tank.

To your detail question - if you want to use a relay based system, you boost the voltage, if you use a B2B, that will take care of that detail for you; there is no need to do both, unless you are having problems with your starter battery, in which case a B2B on the camper battery will do you no good.

Sooooooo, if you are only driving 30 minutes to an hour a day, you will never keep a 75Ah camper battery happy. What do do?

-- If you park in the sun, and have room for 150w of solar, go for it.
-- If you only camp/travel on the weekends, spring for a decent shore charger and keep your camper battery on charge during the week; even one or two nights should be enough.
 

Capt Jon

Observer
Public Service Announcement - Mechman no longer sells the voltage boosting pigtails.

Lots of work travel interfered with my tinkering, and my job situation has changed my route. I am parking in a deck these days, so solar is not going to help me during the week.

I decided to go with a simple ACR and a pigtail to boost the charge voltage. I installed a Blue Sea ACR, but just discovered I have missed the boat on the Mechman pigtails. They no longer appear on the website, and I just received a response from their customer service that they no longer sell these due to "compatibility problems." (The quotes are not because I don't believe the response, but rather because I don't know what compatibility problems they experienced.) I have plenty of battery, and am getting by just fine by using a charger to top off the house battery during the week, but I would like to get more out of my drive time when I am on trips. My 1990 Toyota is only producing 13.15 volts running down the highway. Sometimes in the morning it will briefly give me 13.7, but it soon settles back down below 13.2. It does not appear to be providing much, if any, charge to the house battery. I am considering an external voltage regulator or biting the bullet and changing to a B2B system.
 

john61ct

Adventurer
Go B2B, ideally a fully adjustable Sterling.

Will allow you to never worry about the regulation ability of whatever umpteen charge sources you tap into over the coming decades.

Fixing that Jeep's alt output does only that.
 

Capt Jon

Observer
I agree on the Optima, that was just the best I could find at the time in Dubai. I am now back in the US and using a Duracell deep cycle.

This one: https://www.batteriesplus.com/battery/marine-and-boat/deep-cycle/bci-group-31m/sli31mdc

It's a traditional flooded lead acid type. A better, and higher capacity, deep cycle battery than the Optima. Not very high tech, but with a reasonable replacement cost so that I won't feel guilty about beating on it if I have to. My concern is that I'm just not getting any charge into the battery at the 13.15 volts my Toyota is giving it.
 
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Capt Jon

Observer
My Toyota is a 1990 FJ62. I'm not committed to spending several hundred dollars on a ten cent problem, but I will admit there are gaps in my electrical skills. I don't want to save a few hundred on parts so that I can spend it on a tow truck when I reap the consequences of my own lack of skill. Is 0.5-0.7v what I need? Do I want it all the time or should it rise and fall with load and SOC? How idiot-proof is the install of the diode?

Right now the voltage at idle will occasionally drop low enough to trip the ACR.

I don't necessarily want adjustable, so much as trouble-free.
 

john61ct

Adventurer
using a Duracell deep cycle.

This one: https://www.batteriesplus.com/battery/marine-and-boat/deep-cycle/bci-group-31m/sli31mdc

It's a traditional flooded lead acid type.

While Duracell/Deka/EPM make a great FLA battery, FFR even better are pairs of their 6V golf car units, no more expensive but last a **lot** longer. And their AGM are meh BTW.

That is generally true for flooded batts, the automotive form factor one are inferior to GCs.


> My concern is that I'm just not getting any charge into the battery at the 13.15 volts my Toyota is giving it

Yes, that will murder even the highest quality batt.

Save up for the Sterling BB chargerat an appropriate amps size, and pull the trigger before you next replace the bank.

If your vehicle is already in the shop for something, you could ask their sparkie if a low-cost VR tweak would get you up to the 14.7V Deka spec for Absorb V.

But I wouldn't spend much money on that, since the DCDC will solve it anyway
 

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