Power supply dilemma for wiring noob

[john61ct]

One additional question: can a B2B charger top up a deep cell with the starting battery? Can this be used as an additional charging source, maintaining a deep cell for days at a time without shore power?

A B2B battery is just designed to modify the **charge source** (alt / solar / genny / mains) output to match the needs profile of the target bank.

Makes little sense to deplete one battery to charge another with no charge source active. There are a **lot** of physics laws at work that make this very inefficient.

Most B2B can't even do it.

Only scenario I can think of is from an LFP bank, to get the lead bank to 100% Full over a few hours after a genny/alt run, tiny AH transferred in total but helping lead longevity.

 

[dwh]

I know that vehicle alternators have their limits in ability to completely charge a deep cycle. So I was hoping this was some type of device that could alternately, COMPLETELY charge a deep cycle with the vehicle system.

Yes, that's the purpose of a B2B - it sucks power from the alternator at whatever voltage then adjusts the voltage to do a proper charge on the aux battery.

But to properly and fully recharge a deep cycle lead-acid battery still takes many hours. The B2B can't change that, but it can shorten it.

Like instead of taking 24 hours drive time to reach 100% without the B2B, it might only take 6 hours drive time with the B2B.

 

[DiploStrat]

Oh. Lol. I know that vehicle alternators have their limits in ability to completely charge a deep cycle. So I was hoping this was some type of device that could alternately, COMPLETELY charge a deep cycle with the vehicle system.
...
How obvious is it that I don't understand much about electricity?

Actually, your vehicle alternator will have no problem at all charging a deep cycle battery - I do it all the time, as do others. The REAL issue is that you rarely drive long enough to complete the charge. So yes, vehicle alternators rarely complete the charge, but it has nothing to do with the alternator itself.

As a practical matter, most of us depend on some combination of solar and shore charging to assure that the camper batteries, which should indeed be deep cycle batteries, achieve a full charge regularly.

(Pedantic? Yes, but worth making the distinction as this plays to the other common misconception - you cannot charge your camper batteries without a B2B.)

 

[john61ct]

Actually, your vehicle alternator will have no problem at all charging a deep cycle battery - I do it all the time, as do others. The REAL issue is that you rarely drive long enough to complete the charge. So yes, vehicle alternators rarely complete the charge, but it has nothing to do with the alternator itself.

Sorry, but plain wrong.

Many many stock alternator/VR setups are so flawed they will **never** get a deep cycle batt to 100% Full

using a proper definition of that state

even in 24 hours of driving.

Others can do it pretty well, in as few as 6 hours without assistance; that just depends on the vehicle and year.

Many modern ultra-efficient Euro-style vehicles have the most trouble.

Some older, more traditional vehicles' VR (or entire alt+VR) can be replaced to improve that problem.

Some have room enough to add an entirely different second alternator.

Many cannot be improved at all, and a DCDC charger becomes the only solution.

For many use cases, the contribution of alternator charging to the overall energy input is so small, it is not worth spending money on that aspect at all.

So, as usual many factors are involved, and the solution for a given rig "depends".

The good news is even a total noob can spend a bit of money on tools like a DMM and ammeter, and with our help, learn how come to a correct decision based on objective data.

 

[luthj]

A bit more information. For a battery that is seeing starting service, the alternator charging voltages are good for returning the tiny amount of power used to start the engine. For batteries that are deep cycled (over 10% DOD), most alternator charge voltages are too low to get then fully charged. This means the last 1-3%. It isn't just a matter of returning the removed AHs. The last 1-3% needs a higher energy level (voltage) to convince the lead sulfate to separate. This usually means at least 14.4V, but often 14.7 or higher for some batteries.

Most vehicle alternators have too low a voltage for this. Newer vehicles may have a smart alternator/charging system. This has a variable voltage, and may have a crude shunt on the battery negative wire. These systems will charge at a higher voltage (~14V) for a short period, and then drop down to the low 13V range. Voltages this low result in very low charging currents.

I am roaming about NZ currently. The cloudy and short days have resulted in 75% or more of my power needs being met by my alternator. Even before boosting its voltage by 0.5V, I was getting good charge rates up to about 90%SOC. That last 10% of charging would take 4 hours at 13.8V, and the last 1% may not return completely at all!

With lead acid any active material not recovered during a charge cycle (partial recharge) becomes harder to recover with each passing cycle (or just with time). This will eventually form a crystal of lead sulfate which in irrecoverable without special chargers. Called sulfation, this process is a major source of capacity loss, and early death.

The good news is that getting the active material recovered with a complete full charge every 7-10 days (or via equalize once a month) can stop this process almost completely.

 

[john61ct]

2-3 times per week is what I shoot for.

Every cycle is of course ideal.

Some people just don't care that much, if their House bank only costs a few hundred fair enough.

But if it's thousands, can be done.

First step is, you need to know how to measure it.

 

[toyick]

I haven't read the whole thread OP, to be honest a lot of this means nothing to me out in the rear world. I to have the same exact ideas as you when it comes to being out camping. I just want stuff to work, and be simple.
With that said, I have installed Several different setups, but my favorite and most simplistic setup is, the Blue Seas ML-ACR 7622 or 7623(one has a remote, one doesn't)...
This is the most basic and effective Battery Isolator that i have come across. I personally run this and love it. I have an Optima red top (starter) and a Yellow top as a house battery.
I run an Arb fridge wired off a Blue seas, circuit breaker, strait to the fridge, Off the house battery i also run my Switch Pros panel.

I used to have a blue seas fuse panel with all the necessary wiring, but the Switchpro is very clean and simple.
(things i like about the switch pro: you can use your smart phone to turn things off and on, also you can set switches to run even with car off)
One thing not to forget is, alot of this stuff can be complete overkill. I can park for a couple days without starting, and have more then enough juice. When building trucks for customers, i try to talk them into simplistic setups. I have built over kill, and simple. But I can tell you that from reading your post a setup like i have, even if you dont do the Switch Pro, and something like a Blue seas panel with a couple relays for bigger lights, im pretty sure you will be plenty happy with an Isolator such as the ML-ACR.

Feel free to PM me if you have any questions.

 

[toyick]

I also forgot to add, Not everyone needs a dual battery setup, how ever the first thing i mention about it is the saftey factor.
My wife takes the truck out camping with her friends, on all girl trips, Every time they leave lights on doors open, have to charge their phones all day... and drain the truck battery, every time with a quick click of a button they jump themselves and be on their way. Being self sufficent like that and having the backup source esp when we are all the way out in lala land, is a huge peace of mind. So i always Recommend going that route, its just something most people dont even think about.

 

[DiploStrat]

Sorry, but plain wrong.

Many many stock alternator/VR setups are so flawed they will **never** get a deep cycle batt to 100% Full

using a proper definition of that state

even in 24 hours of driving.

Others can do it pretty well, in as few as 6 hours without assistance; that just depends on the vehicle and year.

Make up your mind already! Which is it?

Actually, I agree with you - we are quibbling over a few words:

-- "most", and
-- "alternator"

probably driven by our different experiences.

Most of the vehicles that I deal with are based on "Big Three" US trucks and most of these vehicles come with 100A+ charging systems that run at well over 14v, 15.5v in the case of my Chevrolet. There are other vehicles, most notably some Toyotas, especially the Tacoma, and some Mercedes Benz, specifically the Sprinter, that have systems that hover around 13.9v. Obviously, the former will have no problem raising a deep cycle battery to full charge, if they will but run long enough. The latter, not so much. So which is more common, which is "most?" I can only speak to my experience which leans towards the former.

The other quibble is the term "alternator." You are clearly including the voltage regulation system while I an speaking only of the alternator itself. Unless you have a flux capacitor under the hood, you are probably going to want to use your alternator to charge your camper battery. The only question is whether the stock alternator/regulation system can do it. Got a Big Three pickup and the odds are good, a Sprinter or a Tacoma, not so much. But raise the voltage or add a B2B and that same alternator may be fine.

I would hasten to add that I have no experience with the new regen braking systems, but the concept is the same as the REDARC B2B that I use on my MB 917 - the B2B can take in a wide range of voltages and buck/boost as needed to hit a target charging profit.

So while the original poster has probably run screaming from the room, I would make the following recommendation:

Assuming that the alternator on your Tacoma is rated at over 100A (to allow ample reserves) and assuming that your base voltage is around 13.9v and assuming that we are discussing lead acid and not lithium:

-- Your alternator is big enough, but your voltage is too low. Raise it, either by adjusting the overall system voltage or by using a B2B.
-- But, even with the voltage corrected, you will probably never drive long enough to fully charge your batteries. If you have ruled out solar, invest in a good shore charger and use it at least once a week.

I make these comments based on years of running two different, all electric campers with 600Ah battery banks. Unless you are running air conditioning, your overnight drain is unlikely to exceed 150Ah and with a high charging voltage, the battery voltage is likely to rise so quickly that you will not sustain a charge rate much over 50A for very long. (This, of course, is the "dirty" secret of how the relatively low outputs of most B2B can actually be successful.) Thus three - four hours of driving is often enough to complete a bulk charge of between 100 and 150Ah.

For more detail, you may wish to consider these:

Planning your system: https://cookfb.files.wordpress.com/2016/09/plan-electrical-system.pdf

Charging lead acid: https://cookfb.files.wordpress.com/2016/09/battery-charge-slides.pdf (incidentally, posted a call for edits/comments on this one. Still welcome comments. https://www.expeditionportal.com/forum/threads/how-to-charge-a-lead-acid-battery.192038/

Dual Battery systems: https://cookfb.files.wordpress.com/2016/09/dual-battery-slides-2016.pdf

These papers go into more detail than is possible in an Internet post and contain references to help you judge the accuracy of the information presented.

With every best wish and a quick prayer that there are no typos or logic skids in this post ...