KISS Dual Battery Upgrade

[abuck99]

@TeCKis300

I thought this was an informative and helpful thread, thank you- I hadn't ever considered the simple solution you outlined to dual battery set up.

Question: With both batteries wired together without an isolater, how is the load demand on the stock alternator and how much additional charging duration to keep battery(s) charged to 12.6 or better?

 

[TeCKis300]

Thanks abuck99.

To your question... Generally isolators are setup to isolate with engine off. So when on, the isolators don't usually isolate such that both house and starter batts can charge. In this case, when charging, the load is no different to the alternator whether there is an isolator or not.

That said, a second battery is going to load the alternator relatively more. It depends on the state of charge (SOC) of the batts and how much current they will accept, and duration to charge. As second (flooded batt) is no big deal.

I pointed out flooded batt there because you hit an important point. Some batt types, because of their design and low internal resistances will take larger currents when charging. AGM and lithiums have these characteristics and are very large loads to the stock electrical system. Lithiums in particular, have been known to overheat alternator regulators because of the huge charging loads they present for long durations on the electrical system.

Which brings us full circle. Again, the stock electrical system is not really setup for different battery architectures.

A second flooded batt is fine and compatible with the stock charging system, charge profile, and outputs. One will never have to worry about installing a maintainer charger with a dual non-isolated flooded battery setup. Just like stock, but with way more reserve. Isn't that the point?

 

[Mogwai]

Just wanted to come back to this thread and share an experience I just had - IMO a dual battery setup is really the only option, having a single battery + a small lithium battery pack that can only "jump" the truck is not a good solution.

I took a trip last week from San Diego to King of Hammers to San Francisco, and back to San Diego over a weeks time. When I got to SF I parked the truck near the painted ladies (scared to death it was going to get broken into) - but instead I come out to a completely dead truck. The fob wouldn't work to unlock, the light on the ignition button wouldn't come on, and of course it wouldn't try and crank. I had just driven 8hrs and parked the truck for 1 night so there was really no reason the battery should be dead. So I linked my two batteries (Blue Sea ACR) and gave it a few minutes, and the truck started. I drove around for 10 mins, then cut the isolation to try and determine what was going on. The truck died almost immediately, and while I was driving which was scary. Moral of the story: if your battery is dead, and won't take a charge from the alternator, jumping it won't really matter. I was able to keep the batteries linked for the remainder of my trip, another 4 days and plenty of driving/ignition off/on situations. Finally had a chance to hook a multi-meter up today and was able to confirm the alternator is working fine, but the main battery doesn't want to take a charge (less than a year old Interstate from Costco) so I'll be taking it back for warranty. KISS is good, but if I didn't have a second battery installed my trip would have been a LOT different, would have cost me money, time, and headache to "fix" while in SF just so that I could get on w/ it.

Side note, while truck is running the multi-meter is reading 13.85V at my main battery, and 14.1 at my secondary (AGM). Not sure why the "charge" would be different at each battery?

 

[SteveP]

While i was on a 4000mi road trip last year, i brought along one of those lithium battery jumper pack since i didnt have a dual battery setup. There as an instance when a random guy at thengas station asked for a jump. I pulled out the jumper pack, and IT DIDN’T WORK. But it works once i connect my actual battery to his car. That moment made me realize that a dual battery setup was the way to go.

 

[Mogwai]

While i was on a 4000mi road trip last year, i brought along one of those lithium battery jumper pack since i didnt have a dual battery setup. There as an instance when a random guy at thengas station asked for a jump. I pulled out the jumper pack, and IT DIDN’T WORK. But it works once i connect my actual battery to his car. That moment made me realize that a dual battery setup was the way to go.

Had the same exact thing happen when we had a Honda Pilot, went to jump someone else who had a truck and it wouldn't work. I think now though they have much stronger lithium jump packs that would work for our trucks, but the one we had was more in line for a car I guess. Either way, didn't instill much confidence.

 

[grinchy]

My jumper pack started my rig several times when the battery had failed. It does need to be maintenance charged every couple months, and it certainly need to be rated for the engine size.

 

[TeCKis300]

Just wanted to come back to this thread and share an experience I just had - IMO a dual battery setup is really the only option, having a single battery + a small lithium battery pack that can only "jump" the truck is not a good solution.

I took a trip last week from San Diego to King of Hammers to San Francisco, and back to San Diego over a weeks time. When I got to SF I parked the truck near the painted ladies (scared to death it was going to get broken into) - but instead I come out to a completely dead truck. The fob wouldn't work to unlock, the light on the ignition button wouldn't come on, and of course it wouldn't try and crank. I had just driven 8hrs and parked the truck for 1 night so there was really no reason the battery should be dead. So I linked my two batteries (Blue Sea ACR) and gave it a few minutes, and the truck started. I drove around for 10 mins, then cut the isolation to try and determine what was going on. The truck died almost immediately, and while I was driving which was scary. Moral of the story: if your battery is dead, and won't take a charge from the alternator, jumping it won't really matter. I was able to keep the batteries linked for the remainder of my trip, another 4 days and plenty of driving/ignition off/on situations. Finally had a chance to hook a multi-meter up today and was able to confirm the alternator is working fine, but the main battery doesn't want to take a charge (less than a year old Interstate from Costco) so I'll be taking it back for warranty. KISS is good, but if I didn't have a second battery installed my trip would have been a LOT different, would have cost me money, time, and headache to "fix" while in SF just so that I could get on w/ it.

Side note, while truck is running the multi-meter is reading 13.85V at my main battery, and 14.1 at my secondary (AGM). Not sure why the "charge" would be different at each battery?

Glad you had a provision to get you back on the road, and back on your trip! Seriously, it was a good save.

With any failure, it's always worthwhile to ask what got you there. You might not like what you're going to hear, but I highly suspect the following that led to your failure. Please correct me if any of my assumptions are wrong, as I haven't looked at your setup in detail.

I believe you said you have an AGM house battery and flooded starter batt. An isolator that disconnects the banks upon stopping the vehicle. They link together to charge when the vehicle is on.

Battery setup 101 tells us to never mix battery types. Yes, you have an isolator to separate under discharge. In charging, it's just as important. Mixing batts of the same type even if they differ in capacity, is somewhat okay. Mixing different battery types is bad.

What led to your flooded starter batt prematurely failing is that it had been systemically undercharged.

Because of the mixed battery type.

AGMs have less internal resistance, and can charge and discharge quicker. When the vehicle is on, two things are likely going on:

1. AGM, due to less internal resistance, is taking majority of the current to charge first
2. Once AGM is full, the regulator senses reduced load on the electrical system, reducing its output, causing the flooded never to fully charge.

Exacerbating this perhaps is the AGM has better standby leakage qualities and you may not be regularly using house accessories. When starting the vehicle and the isolator closes, the alternator/regulator senses full just about immediately and never putts charge back into the flooded starter batt.

Flooded batts hate being undercharged and will sulfate. Sulfate sheds collect as piles underneath the battery plates. When enough of this happens, and potentially with the long drive the day prior, winds up shorting the cells such that it will never have a chance to produce 12V again.

Shorted cells happen, but it is not the normal failure mode of a battery in a well designed system. As you found out, cannot support a running vehicle. Batts generally fail in the manner of holding less charge, and in this failure mode, a jumper can help a car run with a compromised battery.

In regards to your side note. The AGM is full and reads higher. The flooded batt is drawing the voltage down either because of an internal load or short. What does it read without any charging?


I believe you can fix your setup with a common battery type. Otherwise, this may well occur again.

 

[BetoLC]

Glad you had a provision to get you back on the road, and back on your trip! Seriously, it was a good save.

With any failure, it's always worthwhile to ask what got you there. You might not like what you're going to hear, but I highly suspect the following that led to your failure. Please correct me if any of my assumptions are wrong, as I haven't looked at your setup in detail.

I believe you said you have an AGM house battery and flooded starter batt. An isolator that disconnects the banks upon stopping the vehicle. They link together to charge when the vehicle is on.

Battery setup 101 tells us to never mix battery types. Yes, you have an isolator to separate under discharge. In charging, it's just as important. Mixing batts of the same type even if they differ in capacity, is somewhat okay. Mixing different battery types is bad.

What led to your flooded starter batt prematurely failing is that it had been systemically undercharged.

Because of the mixed battery type.

AGMs have less internal resistance, and can charge and discharge quicker. When the vehicle is on, two things are likely going on:

1. AGM, due to less internal resistance, is taking majority of the current to charge first
2. Once AGM is full, the regulator senses reduced load on the electrical system, reducing its output, causing the flooded never to fully charge.

Exacerbating this perhaps is the AGM has better standby leakage qualities and you may not be regularly using house accessories. When starting the vehicle and the isolator closes, the alternator/regulator senses full just about immediately and never putts charge back into the flooded starter batt.

Flooded batts hate being undercharged and will sulfate. Sulfate sheds collect as piles underneath the battery plates. When enough of this happens, and potentially with the long drive the day prior, winds up shorting the cells such that it will never have a chance to produce 12V again.

Shorted cells happen, but it is not the normal failure mode of a battery in a well designed system. As you found out, cannot support a running vehicle. Batts generally fail in the manner of holding less charge, and in this failure mode, a jumper can help a car run with a compromised battery.

In regards to your side note. The AGM is full and reads higher. The flooded batt is drawing the voltage down either because of an internal load or short. What does it read without any charging?


I believe you can fix your setup with a common battery type. Otherwise, this may well occur again.

Wow, this is like watching “House, MD”...

 

[Eric Sarjeant]

It’s funny how different people define “simple”. I read the initial post and did not find it any more simple than using a traditional isolator. My limited knowledge is: you want a deep cell battery isolated from your cold-cranking battery. Of course you can talk about battery elements, placement, etc. but that’s the gist of it.
If you want simple, bring the jump box or a Goal Zero, as mentioned above.
If that’s not simple enough an isolator (or cheap DCDC) and a battery box gets you going for <$500.
I don’t challenge the offered solution brings any added value or simplicity. Especially because the instructions say to start with two new matching batteries, which makes your initial start up cost as high as doing it traditionally. But I could be wrong and appreciate the proposed solution as a viable one.

 

[Mogwai]

House MD? Fun, I'll play. So I took the battery back to Costco, good news is it was "free" exchange ($5 + tax). Bad news is, they didn't diagnose the battery. Got the new battery in and first tested both at rest: 12.59 new starter battery off the shelf; 12.71 AGM house. Started the truck but kept the circuits isolated: 14.11 off new starter battery. After a few mins I linked the two while truck was on: 14.08 starter; 14.06 AGM. After ~5 mins truck idle the starter dropped to 14.06; and AGM stayed at 14.06.

@RET2 had another theory, I recently went on two multi-day desert trips (including KOH before the long drive to San Fran) so fast travel and whoops, vibrations for sustained periods of time vs slow crawling. Could I have broken a lead plate or something? Maybe this is some offroaders/UTVers prefer AGM since they have better vibration resistance?

Other than that, I think my best course of action is to... do nothing to the setup, but run the circuits isolated by default, and only connect after prolonged use of the house/AGM battery. To your point, I don't actively run something off house during day-to-day use - no fridge, etc... only lights + power for additional sockets. Although the quick voltage measurements don't really make me worry that the starter battery is being systematically undercharged by using the ACR (for the record Blue Sea ACR 7622), in my case, just in case it would make sense to only connect the two while I'm driving as needed. And I can always connect the battery tender at home if I want to make sure either is tip top.

 

[RET2]

Dual voltage displays ( clearly visible from drivers seat) could be your friend?

 

[TeCKis300]

House MD? Fun, I'll play. So I took the battery back to Costco, good news is it was "free" exchange ($5 + tax). Bad news is, they didn't diagnose the battery. Got the new battery in and first tested both at rest: 12.59 new starter battery off the shelf; 12.71 AGM house. Started the truck but kept the circuits isolated: 14.11 off new starter battery. After a few mins I linked the two while truck was on: 14.08 starter; 14.06 AGM. After ~5 mins truck idle the starter dropped to 14.06; and AGM stayed at 14.06.

@RET2 had another theory, I recently went on two multi-day desert trips (including KOH before the long drive to San Fran) so fast travel and whoops, vibrations for sustained periods of time vs slow crawling. Could I have broken a lead plate or something? Maybe this is some offroaders/UTVers prefer AGM since they have better vibration resistance?

Other than that, I think my best course of action is to... do nothing to the setup, but run the circuits isolated by default, and only connect after prolonged use of the house/AGM battery. To your point, I don't actively run something off house during day-to-day use - no fridge, etc... only lights + power for additional sockets. Although the quick voltage measurements don't really make me worry that the starter battery is being systematically undercharged by using the ACR (for the record Blue Sea ACR 7622), in my case, just in case it would make sense to only connect the two while I'm driving as needed. And I can always connect the battery tender at home if I want to make sure either is tip top.

Plausible in regards to the whoops/vibrations. Not likely IMO.

In a 6000lb rig (7000+?) rigs like the LC, because of mass dampening and refinement, it would be frame hitting or serious bottoming of suspension type hits that would get anywhere near battery vibration thresholds. As hard as we drive our cruisers, IMO, they are generally gentle on batts on account of lots of tire, lots of suspension travel, bushings in the suspension and non-rigid body on frame connection, and all the mass dampening. Perhaps you do abuse your rig that hard, but I suspect not. UTVs or more smaller/raw type vehicles with very direct transmission paths, yeah, more likely.

I hope you don't take my inputs as pointed critique. I'm here to learn and share tech on our awesome cruisers.

I'll leave you with this:

We would strongly discourage anyone from connecting batteries in series or parallel applications, if the batteries are not identical in age, size and type. It sounds like your batteries are different in each of those ways. Different brands of batteries can have different charging and discharging characteristics, with some accepting a charge or delivering current faster than others. That can be true even if the batteries are the same size. Different types of batteries (flooded or AGM) also can have different charge/discharge characteristics. When you connect two or more batteries that don't charge and discharge at the same rate, one battery will probably end up overcharged and/or one battery will end up undercharged. Neither is a scenario you want to have happen to your batteries, as it will probably shorten the lifespan of both and could create a potentially create a dangerous situation, if one battery gets severely overcharged.

The same is also true of batteries that are identical in every way, except that one battery is older than the other. As batteries age (or get used), their charge/discharge profile changes. As such, they essentially charge and discharge at a different rate a year later, than they did when they were brand-new. That means you shouldn't connect batteries together that aren't the same age or haven't been used in the same application since they were new, even if they are the exact same make and model.

Unfortunately, that means when one battery in a bank of two or more batteries needs to be replaced, they should all be replaced at the same time. That doesn't mean the other functioning batteries should be discarded entirely, but they should not be used in an application that has batteries that differ in age, size or type. For some marine and RV applications that use a lot of batteries, it may make sense to isolate a larger bank of nine batteries into three smaller banks of three batteries, instead of connecting them all together. That way, if one battery goes bad, far fewer batteries need to be replaced.

 

[TeCKis300]

It’s funny how different people define “simple”. I read the initial post and did not find it any more simple than using a traditional isolator. My limited knowledge is: you want a deep cell battery isolated from your cold-cranking battery. Of course you can talk about battery elements, placement, etc. but that’s the gist of it.
If you want simple, bring the jump box or a Goal Zero, as mentioned above.
If that’s not simple enough an isolator (or cheap DCDC) and a battery box gets you going for <$500.
I don’t challenge the offered solution brings any added value or simplicity. Especially because the instructions say to start with two new matching batteries, which makes your initial start up cost as high as doing it traditionally. But I could be wrong and appreciate the proposed solution as a viable one.

A dual battery setup, on the face of it, seems like an easy proposition. There's more going on here. Solutions like an isolator, causes trades that most don't recognize. For anyone that's "invested" in a setup, don't like to hear from people like me that it's a flawed setup that wouldn't pass engineering scruitiny. Hence I suggest KISS as an alternate solution. I'm not your traditional off-roader/overlander who follows others annecdotes. Rather a trained and practicing engineer (and a long time gear head), who critically reviews engineering solutions to be applied on more complex systems. This stuff is my wheelhouse.

Why an isolator causes more problems than it's worth - battery balancing. As they operate as separate banks when the vehicle is off, they'll be drawn down independently to various state of charge (SOC). The assumption that they can be charged by linking together when the vehicle is on is flawed, and will cause premature failure relative to a single battery, or a balanced bank. I'd encourage one to research charging multiple unbalanced batts with a single charger...

You may have bought chargers that advertise multiple states of charge. In a modern vehicle, the alternator/regulator does react to states too, to maintain the highest level of vehicle battery health. Connect 2 batteries, the house battery in a deeply drawn state, and starter battery full, what is the alternator reacting to at that point? It likely detects the full battery and not go into a bulk charge mode, on a shorter drive, that then never fully charges the other battery.

 

[SteveP]

A dual battery setup, on the face of it, seems like an easy proposition. There's more going on here. Solutions like an isolator, causes trades that most don't recognize. For anyone that's "invested" in a setup, don't like to hear from people like me that it's a flawed setup that wouldn't pass engineering scruitiny. Hence I suggest KISS as an alternate solution. I'm not your traditional off-roader/overlander who follows others annecdotes. Rather a trained and practicing engineer (and a long time gear head), who critically reviews engineering solutions to be applied on more complex systems. This stuff is my wheelhouse.

Why an isolator causes more problems than it's worth - battery balancing. As they operate as separate banks when the vehicle is off, they'll be drawn down independently to various state of charge (SOC). The assumption that they can be charged by linking together when the vehicle is on is flawed, and will cause premature failure relative to a single battery, or a balanced bank. I'd encourage one to research charging multiple unbalanced batts with a single charger...

You may have bought chargers that advertise multiple states of charge. In a modern vehicle, the alternator/regulator does react to states too, to maintain the highest level of vehicle battery health. Connect 2 batteries, the house battery in a deeply drawn state, and starter battery full, what is the alternator reacting to at that point? It likely detects the full battery and not go into a bulk charge mode, on a shorter drive, that then never fully charges the other battery.

So matching battery hardwired in paralell would the way to go? Maybe a better solution would still be keeping the isolator but also using a DC/DC charger to charge the house battery?

 

[yonah]

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!

I’ve had great experience with X2Power’s AGMs. I had one of their Group 31s in my Tacoma and have a smaller variant in my wife’s Q5.

They’re rebadged Northstars. 4-5 year warranty depending on the model. And have a nationwide dealer network - Batteries+Bulbs for convenience.

 

[TeCKis300]

So matching battery hardwired in paralell would the way to go? Maybe a better solution would still be keeping the isolator but also using a DC/DC charger to charge the house battery?

Yes, hardwired parallel as a single bank, if you want the alternator/regulator to charge and tender both of them correctly.

I believe the isolator concept worked well on older vehicles with less regulated electrical systems that ran hot. Yet they were also good about boiling/cooking batts, so one had to regularly water them. Remember the days of hydrometer and measuring electrolyte density? People haven't had to water car batteries in decades.

Modern vehicle alternators regulate voltage and current output much tighter, and will stop just short of electrolyte gassing. Such that there's relatively little extra current to charge anything when it "sees" a full battery on the circuit. So either house battery is full and the starter battery is not sufficiently recovered, or starter battery is full and the house battery never fully recovers. There's really no such thing as a single channel DC charger that can manage multiple batteries at different charge states simultaneously, unless it's trickle charging which is not useful for the limited on time of a vehicle.

DC/DC chargers are a possibility. Not sure I've seen realistic ones that have good bulk charge capacity over something like 5-10amps?

 

[SteveP]

Yes, hardwired parallel as a single bank, if you want the alternator/regulator to charge and tender both of them correctly.

I believe the isolator concept worked well on older vehicles with less regulated electrical systems that ran hot. Yet they were also good about boiling/cooking batts, so one had to regularly water them. Remember the days of hydrometer and measuring electrolyte density? People haven't had to water car batteries in decades.

Modern vehicle alternators regulate voltage and current output much tighter, and will stop just short of electrolyte gassing. Such that there's relatively little extra current to charge anything when it "sees" a full battery on the circuit. So either house battery is full and the starter battery is not sufficiently recovered, or starter battery is full and the house battery never fully recovers. There's really no such thing as a single channel DC charger that can manage multiple batteries at different charge states simultaneously, unless it's trickle charging which is not useful for the limited on time of a vehicle.

DC/DC chargers are a possibility. Not sure I've seen realistic ones that have good bulk charge capacity over something like 5-10amps?

I’m lookin at this one. Pretty reasonable e compared to the cost of some fancy dual battery setups. DC to DC Battery Chargers - Dual Battery Setups | REDARC Electronics

 

[Mogwai]

There's a pretty slick "Dual Battery Selector" app on that website that runs you through a few questions and spits out the version Redarc to purchase. Interestingly it doesn't differentiate by AGM vs flooded (same choice) nor does it care about size/type of starter vs Aux.

I selected yes to solar (you know just in case) and it spit out: Dual Input 25A In-vehicle DC Battery Charger

That seems a lot more "simple" and has more benefits than running the same exact type/size batteries in parallel for many reasons.

 

[BetoLC]

I’ve had great experience with X2Power’s AGMs. I had one of their Group 31s in my Tacoma and have a smaller variant in my wife’s Q5.

They’re rebadged Northstars. 4-5 year warranty depending on the model. And have a nationwide dealer network - Batteries+Bulbs for convenience.

Thanks for the suggestion - from all the discussions here I’m actually thinking that a larger-than-stock flooded wet cell is the way to go with either KISS Goal Zero or DC-DC charging.

So, what are people’s suggestion for the toughest Flooded Wet Cell on the market? Thanks!

I’m willing to pay up for this component as I don’t want have to reply on a LiPo “jumper” pack unless its’s worst case.

It would be great if there was a way to “chip” a late-model LC200 ECU into properly charging an AGM. I have seen some references to tricking it with an in-line diode (i remember from some class that would drop the measured voltage by 0.7v). My truck is mostly parked in the dark nowhere near an outlet so I have no good option to finess the charge on the cranking battery away from the alternator.

Thanks!

 

[Markuson]

In our week+ Baja group, we had two different instances of dead batteries on two of our 5 200’s for different reasons. One was a lithium, btw. Not blaming lithium, but simply noting we had a variety of setups. Neither instance of failure was my dual battery setup—which is based on two AGMs that not run in parallel.

This is significant especially considering that I am an exceptionally-high electrical-power user in the field...not only keeping things both frozen and refrigerated ...but also recharging stuff for myself and others in the group...running a microwave(!!) every single day (with truck running), constantly charging devices while driving and while not running the engine....and never having an opportunity to top-off either battery via an external charger over the 8 days.

All of this was done using a type 31 AGM main and a type 35 AGM 2nd. You know... the type some here say is fundamentally incompatible with our trucks?

If they are “fundamentally incompatible”...and I’m a massive power user—which logically should exacerbate such an incompatibility—then why I was one of the three trucks that ran into zero battery issues on the trip despite extreme power use throughout the trip?

Me-thinks some doth protesteth & theoretically declareth much...

It is certainly not a simple puzzle...and it is not without effort to make sure of potential issues—which I’ve run into and overcome. One issue turned out to be a faulty booster module within my IBS system...which they replaced & had nothing to do with battery type. Despite repeated declarations of demise & predictions various dooms ... I’m sticking with demonstrated and repeatedly-experienced success using non-parallel AGMs.

I have nothing against theory, and I am a very careful shopper. But given the choice between theory and remarkably-successful practice, I’ll take the latter...even as I consider theory, research, products & the ever-changing options available to us.