KISS Dual Battery Upgrade

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Sandroad said:
I really like the KISS of the OP. I would add 3 notes:

3) Don't bother with a voltage readout of a battery under load using a cheap device. That's such a coarse and variable way to check battery SOC and health it's not worth it. I'm in the "use a good battery monitor or nothing" camp.
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#3 is really true. I have a number of USB charger outlets in my truck that have voltage indicators...**because it’s frankly hard to find 2.4V USB outlets that DON’T have them!** Seriously...they’ve become almost standard features, which is a little annoying/useless.

But anyway... Agree. Under even small loads like low draw USB devices USB...the readings range up to 1V or more different depending on distance from battery and loads on that particular line.
 
Sandroad said:
I really like the KISS of the OP. I would add 3 notes:

1) if you're buying 2 new batteries, for sure get deep cycle/hybrid batteries. Their internal construction will make a difference in longevity in this scenario.
2) If you go with a low voltage voltage protection mechanism, make sure it's auto-reset. When the stater is run, even a dual battery setup like this will momentarily pull the voltage down low enough to trip a low voltage detection device.
3) Don't bother with a voltage readout of a battery under load using a cheap device. That's such a coarse and variable way to check battery SOC and health it's not worth it. I'm in the "use a good battery monitor or nothing" camp.
Click to expand...

Great point on #2. Is there a specific unit you recommend? The threshold could probably be set lower than typical sag.

#3, is not so clear. This would assume that absolute voltage readout is a perfect science, which it is not.

Voltage should be used as a rough reference with even the best and most precise high end monitor (even cheap voltmeters are pretty precise btw). This is because battery voltage to state of charge is not linear. It varies per the particular design, and particular battery. It's also very subject to load, battery temperature, battery health, etc.

I would agree a monitor that reads directly at the terminals would be more accurate. Still to be best utilized as a rough estimate of available capacity left.

A shunt type battery monitor (which measures actual net amps in and out), would be more useful still. It would be going down the overkill path tough.
 
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TeCKis300 said:
Great point on #2. Is there a specific unit you recommend? The threshold could probably be set lower than typical sag.

#3, is not so clear. This would assume that absolute voltage readout is a perfect science, which it is not.

Voltage should be used as a rough reference with even the best and most precise high end monitor (even cheap voltmeters are pretty precise btw). This is because battery voltage to state of charge is not linear. It varies per the particular design, and particular battery. It's also very subject to load, battery temperature, battery health, etc.

I would agree a monitor that reads directly at the terminals would be more accurate. Still to be best utilized as a rough estimate of available capacity left.

A shunt type battery monitor (which measures actual net amps in and out), would be more useful still. It would be going down the overkill path tough.
Click to expand...

Unfortunately the only monitor I'm familiar with is the Victron, which violates the KISS principle! It pretty much does it all, including a "starter delay" that keeps alarms from sounding unless it take the engine more than 10 seconds to start. And, over/under settings are programmable. And, it's an accurate, shunt-based, monitor. But, it's not in the KISS category, so I'll take a look around in the RV world and see if anyone has a simple low voltage alarm that auto-resets.


https://www.solar-electric.com/lib/wind-sun/Victron_Datasheet_BMV-712.pdf
 
Can anyone confirm whether the truck will "run" on the alternator alone? I was under the impression that it will not, and that if the battery/bank of batteries is too low that even if you get the truck started via jump start it would still eventually die on you on the road. True or false?
 
^Not likely. Especially a vehicle as technology laden as the 200-series. It will probably run, but will stall in transitions.

Still, a marginal or dead battery can be jumped and will work in a pinch. A dual battery setup like this is still better off than a standard single battery setup, with more options if an issue were to arise.
 
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I'm waiting a bit more on dual battery until I can get a house cell that's lithium. A couple more years of output from the gigafactory should depress prices enough.
 
Mogwai said:
Can anyone confirm whether the truck will "run" on the alternator alone? I was under the impression that it will not, and that if the battery/bank of batteries is too low that even if you get the truck started via jump start it would still eventually die on you on the road. True or false?
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I can't speak for the 200, as I don't own one, but many previously-owned cars in the family did, in fact, run without batteries. That said, they were not driven without batteries.

In eastern Europe it is common practice to start a car with a dead battery by removing said battery, connecting a charged battery from another vehicle, starting the car, and while it's running, removing the charged battery and connecting the dead one in its place. Neutral + some skinny pedal to maintain high revs for a few minutes (gives the dead battery a bit of a charge), and you're good to drive home. A bit of work, but saves your butt without the need for jumper cables.
 
grinchy said:
I'm waiting a bit more on dual battery until I can get a house cell that's lithium. A couple more years of output from the gigafactory should depress prices enough.
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I do believe a standalone lithium to be potentially an easier, more flexible solution.

Between the built in onboard battery vs standalone batt, the major deciding factor is really how the rest of the vehicle is built.

If one has more built in devices on vehicle, than it needs to draw from a built in battery setup. If one goes the more modular device route, then those can lean on a standalone house batt.

That said, there's plenty of opportunity for mixing and matching. A expanded onboard single grp 31 batt, with standalone lithium might just be the ticket. Especially when weight is taken into account.
 
TeCKis300 said:
A expanded onboard single grp 31 batt, with standalone lithium might just be the ticket. Especially when weight is taken into account.
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That's what I would do.
 
What are you thoughts on having different battery size for this KISS solution? I can do either a group 27 or 31 on the primary battery location but only a 35 on the secondary location.

Also, does anyone know who has a tray kit for the secondary location that would accommodate a battery larger than a group 35?
 
^Unforunately, that's a no go. When Batts are setup as a bank, they must be matched, preferably acquired at the same time.

If not, there will be uneven draw, and constant micro-currents as the batteries attempt to balance each other under load/idle/charge. This is a sure way for them to prematurely wear and ultimately fail. Hence the old wives tale KLF mentions in the 3rd post.
 
SteveP said:
Also, does anyone know who has a tray kit for the secondary location that would accommodate a battery larger than a group 35?
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I am working on this now. I have the Slee 2nd tray installed, and I am going to try to install a group 34/78 battery. It's a little bigger than the 35, but what I really like about it is the dual set of terminals. Anything larger than that, and you will need to relocate the P/S reservoir to behind the air box, which I really don't want to do.

(I also have the Slee primary tray, with a group 31 AGM, but I will be using the Blue Sea ML-ACR)
 
Follow up, I did get the group 34/78 battery installed, it was a pain, but it works. I had to hack up the Slee tray and fab up a top clamp, so I could put the ACR on top of the battery. If I were doing this again I would just use a generic tray, or see about the OEM parts for the second battery for the diesel trucks. There's no way anything bigger will fit, unless you move the PS reservoir behind the air box. I also had to cut an unused mounting ear off the radiator to make room.

IMG_20190117_175121.webp
 
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KLF said:
Follow up, I did get the group 34/78 battery installed, it was a pain, but it works. I had to hack up the Slee tray and fab up a top clamp, so I could put the ACR on top of the battery. If I were doing this again I would just use a generic tray, or see about the OEM parts for the second battery for the diesel trucks. There's no way anything bigger will fit, unless you move the PS reservoir behind the air box. I also had to cut an unused mounting ear off the radiator to make room.
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KLF, that's pretty enough that I'd stick it on an airplane. VERY nice work. :beer::beer::beer:

Steve
 
KLF said:
Follow up, I did get the group 34/78 battery installed, it was a pain, but it works. I had to hack up the Slee tray and fab up a top clamp, so I could put the ACR on top of the battery. If I were doing this again I would just use a generic tray, or see about the OEM parts for the second battery for the diesel trucks. There's no way anything bigger will fit, unless you move the PS reservoir behind the air box. I also had to cut an unused mounting ear off the radiator to make room.

View attachment 1882947
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Curious about your terminal connections.
Do you have a link to those by chance?
 
Willy beamin said:
Run a group 31 and a jumper pack as back up. That is KISS
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Agreed.

I had his setup in my Tacoma for a couple of years. I sold the truck and it’s still going strong for the current owner.
 
Going with the KISS approach of a single better-than-stock battery etc can anybody recommend a specific group 31 and/or group 35 battery that would best suit wheeling the truck and the characteristics of the 200’s “intelligent” alternator?

I have read a lot of battery threads this morning and my head is beginning to spin... Thanks!
 
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