New battery recommendations

[Cruisertrash]

@DaveInDenver @DougCruiser
I just got comoletely lost by acronyms 🤣

I understand I’ll need some sort of computerized device between the “house” battery and the rest of the truck electrics to manage the charging of both batteries from the alternator that’s on the truck side of things, and then a separate feed and fuse panel, and really separate electrical, for all the things powered from the house battery. I don’t understand the diode or VSL or MCACL or whatever was mentioned above. I need one of those “for dummies” books. Maybe it’s as simple as a second voltage regulator and a diode to keep the alternator charging the house battery, but not letting the house battery supply current to the truck side. I don’t know.

 

[DaveInDenver]

You don't strictly need to separate the starter and house batteries. The reason to do this is so that you don't discharge your starting battery and can't start.

ML-ACR means Magnetic Latching - Auto Charging Relay.

VSR means Voltage Sensing Relay

Not sure what VSL means in this context. VSL is the NIST equivalent in the Netherlands. It means something in Dutch but I have no idea what.

The purpose of the sensing part of ML-ACR or VSR is watch when the engine is running. When the alternator voltage is high enough to charge the relay closes and puts both batteries on the charge and when it's not running the voltage will go down and will separate the two sides, presumably meaning the house battery is isolated from the starting one, which is always connected to the charging system.

You're an electronics guy. A diode has a characteristic forward voltage drop, right? So the trick here is you take out the ALT-S fuse out, which is a fuse that links the battery (via the fuse box bus) to the alternator voltage sense (literally ALTernator Sense) so the alternator knows how to regulate. Normally a fuse has no voltage drop across it.

But a diode will, normally 0.7V in the classical textbook description, drop voltage. So what you're doing is telling the alternator to run 0.7V higher. The voltage regulator wants, say, 14.2V but since the sense line is forced 0.7V lower than the battery the alternator actually runs at 14.9V, for example.

In purpose built trucks, like fire trucks and ambulances, they actually do run two alternators and two voltage regulators. One side only deals with the starter and the other (usually much larger) charges the house batteries. You could not do this with one alternator. You can only have one regulator telling it what to do. The factory uses the starting battery as the criteria.

This works fine if you parallel a house battery that's similar to the starting one. Doesn't have to be exactly the same but it does ideally need to want the same charging voltages at the same time.

That's where the problem comes in. Even if you use exactly the same batteries you don't leave them in the exact same condition. The house will have been discharged more deeply overnight. So the next morning you start and the main battery wasn't run down much. So the alternator thinks it's done after a few minutes and starts to ramp down. But the house needs a hour or 4 to charge back.

So what do you do? So you keep the charge aggressive and harm the starting or roll back and never get the house back to 100%? It seemed in my case that the factory system was OK for the starting battery but aging the house very fast.

That's the root of the simple relay-based dual battery system. You can't do two things well at the same time.

What you can do is us the starting/charging side to feed into a smart box that makes a new voltage that is right for house. That's what a DC-to-DC charger does. It takes the lower voltage that is OK for an already fully charged starting battery and make a higher voltage to charge the house faster and fully.

 

[HDavis]

So I bought the cheapest G35 Wal-Mart had, standard car, 12 month warranty, made in Spain. That was in 2019 and I still have that battery.

I pretty much only buy EverStart Walmart batteries. One of them we had was 7 years old and was still charging fine when we sold my wife's Frontier last month. The other is in the Stout and dated 2019. I just replaced a wasted 3-year-old interstate battery in the 200 with an EverStart. I hope I can get a least 4 years out of it.

 

[Cruisertrash]

I pretty much only buy EverStart Walmart batteries. One of them we had was 7 years old and was still charging fine when we sold my wife's Frontier last month. The other is in the Stout and dated 2019. I just replaced a wasted 3-year-old interstate battery in the 200 with an EverStart. I hope I can get a least 4 years out of it.

I’m hoping this Duracell lasts longer than the two Interstates I had prior. Before that my Tacoma had an Optima that was approaching 10 years old.

@DaveInDenver i need to read your post like 30 more times. I can rebuild and test an amplifier on a scope, but for some reason this dual battery thing is very confusing for me.

 

[CardinalFJ60]

Did you order directly from the Aussie company and have it shipped from there?

Directly from Australia. It took forever. But after I tried to make one and failed I just purchased the right thing

i got the correct diodes and tried to solder together one on a fuse. A more skilled person could do it. An OG outlaw showed me the trick

 

[dan1554]

I know for fact that @dan1554 has a slick setup

I run a small 30ah lithium iron phosphate battery that gets charged by the alternator and solar. Just enough to run my fridge indefinitely. It's hidden in my right rear quarter panel. Lots more usable ah vs lead acid and great for tight spots. That said the lifepo4 starting batteries are out of my budget.

 

[DaveInDenver]

@DaveInDenver i need to read your post like 30 more times. I can rebuild and test an amplifier on a scope, but for some reason this dual battery thing is very confusing for me.

Where does it go off the rails for you? I don't want to confuse you (or anyone) but I also don't want to insult by being too elementary.

The keys lie in understanding a few main concepts (e.g. knowing keywords to search and read about).

One being the different types of lead-acid (sticking with that type for the moment) - FLA (Flooded Lead-Acid), wet, vented or sealed, VRLA (Valve Regulated Lead-Acid), AGM (Absorbed fiberGlass Mat).

Another being discharging, open circuit (the do nothing middle) and charging, which are states that a battery can be in at any moment in time.

Then knowing about charging steps, those being basically bulk, absorption and finishing/float.

A knock-on to those are SoC (State of Charge), DoD (Depth of Discharge) and capacity (the amp-hour rating), charge rate, over voltage tolerance.

What ties all of those together is various voltages that trigger things to happen, which is a function of the electrochemical nature of batteries and implicit to the internal workings, e.g. the equivalent circuit inside, and it's interaction with the outside device and circuits.

What is important to realize is that the type of lead-acid, and indeed the specific brand and model or other chemistries, determine voltage, current and time necessary for a battery to work, how well it works, how to avoid damage (or repair it, if possible) and, thus, reliability and lifespan.

That's basically what I'm on about. All lead-acid are close enough that you can put them together and it'll work sort of. But the devil in the details is getting 5 or 10 years from a battery instead of 1 or 2 years. Or it may manifest is being able to count on having a fridge run for 3 days or getting worried after just one.

Just one starting battery is hard enough to get it all right. Doubling them up and mixing chemistries will multiply the ways to screw it up and get burned (perhaps literally) by details you overlooked or weren't aware.

Those last few statements encompasses about 250 years of chemistry, physics and electrical engineering. So it's hardly a small topic...

Wading into lithium makes some things easier, some not.

 

[rover67]

I run a small 30ah lithium iron phosphate battery that gets charged by the alternator and solar. Just enough to run my fridge indefinitely. It's hidden in my right rear quarter panel. Lots more usable ah vs lead acid and great for tight spots. That said the lifepo4 starting batteries are out of my budget.

Yep that’s kinda the direction I was thinking. I’ll have to check out your setup

 

[Corbet]

I run a small 30ah lithium iron phosphate battery that gets charged by the alternator and solar. Just enough to run my fridge indefinitely. It's hidden in my right rear quarter panel. Lots more usable ah vs lead acid and great for tight spots. That said the lifepo4 starting batteries are out of my budget.

Something like this has also been on my radar.

 

[C.Gerdo]

I’ve gone away from AGM and back to flooded lead acid.
I’ve had great luck with the Walmart everstart flooded/mid-range.
I just replaced a 2 year old AGM with a flooded/everstart.

 

[Inukshuk]

This thread could be a sales piece for the Dometic PLB40 - self contained 40 ah Lithium Iron Phosphate battery (which BTW just dropped from $849 to $539 on Dometic's website)

I have been using one for 4 years to run the fridge and small accessories like 300W inverter for starlink, charge devices while parked
charge at home b4 trip, from truck as you drive, from solar (built in controller)
Max input on PLB40 is 8A, so it takes a while to charge from 0%
You get use of almost the full 40ah. it has a % readout and built in protections.
Outputs are 2x12v (one cig, one ARB style for fridge) and 2 x USB A
Can charge as you use, but then charges slower. When needed I run fridge off truck by day and let the PLB just charge. If I am camped all day I can hook solar to PLB as it runs fridge (with solar producing more than the fridge needs anyway) and charges. If I really need to charge the PLB for fridge use (hot weather), I hook two solar panels - one to truck and one the PLB and let the fridge run off the truck (with solar producing more than the fridge needs anyway) and PLB charge off solar.
Only once or twice ever was the batter too cold to charge since I keep it in the passenger compartment.
minimal extra wiring.
Portable between trucks and anywhere else.

 

[Stuckinthe80s]

Just to keep adding to the discussion of what battery to use, I'm going to summarize my takeaways from the numerous threads I've read through on the subject over the years:

• There are plenty of examples of expensive batteries going bad within just a couple of years - Optima, Odyssey, etc.
• There are plenty of examples of cheap batteries lasting a long time
• Almost all brands are now made in the same factories so brand loyalty is moot now, for the most part
• I've swore off expensive batteries and just keep switching out the cheap ones. If they die within a year, I get a "new" battery for free. Is it a pain in the ass? Yeah, but maybe the next one will last longer.
• No matter what battery you have, if it isn't maintained properly, a $400 battery has just about as much chance of leaving you stranded as a $100 one does so just invest in a good jump box instead

YMMV