Dual battery maintainer with ‘smart’ isolator and daily driving.

[wADVr]

Hello,

after much overthought the last year on how to set up a dual battery setup in my 09 JKU I stumbled across a fantastic deal on a pair of brand new Odyssey G34 PC1500s and a Genesis JK dual battery setup. For those that dislike this setup due to the price that is not a factor here to say the least. Installed all of his last Saturday (Nov 13th) roughly the same exterior temp etc. Battery voltage upon installation was 12.9 on each battery. The smart isolator connects the batteries when the starter battery is above 13.2 volts with a time delay of 2 minutes. They stay connected even after the engine is turned off until voltage drops to below 12.7. In theory this all sounds great and am not complaining about that but it dos seem to come at a cost for my use. To define my use would be in the daily driver/weekend warrior category but most importantly it must be noted that my commute is relatively short at only 20 minutes each direction.

so on to some data then the issue as I see it and the question….

since Saturday I have made two trips of 35 minutes each on Sunday, then daily driving this week (3 days two 20 minute each day) so in total 190 minutes of driving over 8 trips. This morning I tested the battery voltage using my electronic multimeter and was a bit surprised to find the starter battery at 12.45 and the aux battery at 12.77 @41°. I started the Jeep to see what charging voltage was (my original intent of testing in the first place) voltage at the starter battery when the Jeep was running was 14.7-8 which I was impressed to see.
my theory is that the limited run time is not charging the starter battery back with the aux being connected at the same time. My typical weekend trips can have between 1 hour of drive time up to all day driving. I believe all day driving will get them topped off and all good but I’d rather keep them topped off during the week and ready to go limiting the time where the batteries are not fully charged and reducing their performance and most importantly longevity.

My original goal/concern was to find facts on adding a maintainer to ensure the batteries are being fully charged. I am looking at the Noco Genesis 10 in my internet searches it seems like this is a good option for this setup and doesn’t seem to matter with the ‘smart’ isolator. There was two opinions on whether to get the dual bank charger Noco Genesis 10x2 https://no.co/genpro10x2 to charge both at up to 10 amps each at the same time. I found a thread where Noco recommended this option. Seems like a risk with the smart isolator that will then connect the batteries when charging but.. more research. The Noco chargers charge at 14.8 in AGM mode and while it is not listed it sounds like they float charge at the desired 13.5-6 so it seems like an ideal setup that I can plug in a couple days a week and keep the batteries topped off since my driving habits are not doing this on its own.

My question is if you’re still reading this long winded post is am I on the right track with a maintainer such as the Noco or with everything considered should I be looking at a different solution?

thanks in advance, always a lot of good info on this forum.

 

[DaveInDenver]

The issue is the Odyssey batteries. I have two of them in a dual battery configuration, although mine are G25/G35 rather than 2 x G34. You have to be a lot more particular about charging them. Even the ~14.7V you see on your alternator is kind of a false sense of security. It's better than 14.2V but it's still not ideal.

With other batteries relying on your vehicle charging system is leaving some battery life on the table but with Odysseys being diligent ends up not being a marginal difference in how long your batteries will last. If you just let them charge it's going to mean it'll last 2 or 3 years instead of 5 or 6 sort of thing.

In my experience you need to routinely put them on a "good" maintainer/charger that is temperature compensated (such as the GEN10X2 is I think) so that the bulk and absorption (at 14.7V nominal at 25°C) are done completely (held for 8 hours) and float (at 13.6V nominal) is held for an extended period.

When the battery temp increases or decreases those two voltages need to compensate, especially absorption. At 41°F you should be stepping up. Going up and over 15V is fine as long as your charger is well controlled. You needn't be too gentle as long as you take care not to abuse them and in fact doing proper temperature compensation is what you want to do. Odyssey recommends 24mV/°C (their suggested formula in the technical manual), so at 41°F/5°C you should be 24mV * (25°C - 5°C) = +0.48V or 14.7V + 0.48V = at 15.18V.

The problem here is under hood temperatures. Even if it's 41°F outside when you're driving it's warmed under the hood. So IMO it's better to err on the side of caution. If you can't do temp compensation (which I can't with my truck and few alternators-based charging systems can) then leave your vehicle safe for driving on the Interstate during the summer knowing that you can only ever achieve 80% or 90% charges and then augment with regular conditioning as often as you can.

It's important to also realize compensation works the other way, too. So if it's +40°C ambient then you need to reduce charging voltage to 14.34V per the formula. That's part of the "don't abuse" thing since overheating to venting or boiling of the electrolyte shortens their life, too. So it's not necessarily better to have your alternator voltage set too high, either. I cringe when I see people bumping their voltages with diodes and stuff, especially in the summer. If you undercharge your battery it's not as immediately harmful as overcharging.

It's when you leave it at 80% SOC all the time where the damage is done. It's fine to drive around only trickle charging your battery/ies at lower voltage as long as you put it on a charger when you park. OTOH putting 110% voltage on it on the highway could be ruin it and that's not recoverable capacity. You can sometimes do a deep discharge and hard charge to break up sulfation from leaving it undercharged too much but once a sealed battery vents that electrolyte is gone forever.

 

[john61ct]

I admit I skimmed only, so will pontificate in generalities, do what you like.

Low amp sources are only suitable for maintenance not replenishing a rig cycling deep.

AGM units need **high amps** at the right voltage for longevity

as well as (separate specs) very regular recharging to

TRUE 100% FULL

most cycles. That takes 7+hours, no matter how many amps are available, high is good but does not speed the process up much.

Each maker defines endAmps differently, but usually, do not stop until current trails down to 0.01C or maybe even 0.005C if you're monitoring manually.

But the voltage has to match the maker data sheet as well if you are combining for charge purposes

or match the expensive House bank, and just replace cheaper Starter every three years instead of four.

Now I know that's just scratching the surface, but it's the most important part so I'll just pause there for feedback before adding fuel to the fire.

Main point being, mains power might need to be your main energy input, rather than just maintenance between drives.

Getting precise profile output for a deep cycling bank from alternator output requires not just a DCDC charger these days, but day-long driving sessions.

 

[wADVr]

Thank you for the detailed replies. I have a lot to read and re-read and research. I am attempting to keep this simple but it appears that is not going to be the case at least initially while I figure this out. I agree with DaveinDenver that the Odyssey batteries being the issue. I ran for a year now literally a normal Napa battery out of my ‘67 VW beetle and never any issue for normal use (I did not run accessories or any deep cycling activity) now I run a larger fancy battery for a couple days and find a low battery (12.45v) kind of sad.
I do need to read up more on my alternator charge voltage set point. Older Jeeps I know had a battery temp sensor that fed the PCM to adjust the alternator charge voltage. This JK does not have a battery temp sensor so how it is compensating for the temp change is a mystery at this point. Using the ambient temp or intake temp is not going to read under hood temps let alone the actual battery temp. It sounds that if I want these Batteries to last I need to get the alternator to charge in the recommended range for the Odyssey. Given the temp I measured the voltage at this morning it should have been higher as DaveinDenver calculated above. I really didn’t want to mess with the Jeep side of things but both posts seem to point to the alternator charge voltage being a problem here. I need to read up on the DCDC charger, I do understand what they are and do but not sure how that would fix my starter battery being low. For the house or aux battery it makes total sense.

Because I am slightly hard headed and read a couple posts of others using the same equipment and installing a Noco maintainer I am still interested in that to help the situation. I emailed Odyssey earlier this week and was told a 7 amp per battery charger/maintainer is their recommendation. Here is a thread with an example of this method toward the end, would be nice to see a long term review..

Genesis Duel Battery, Duel Odyssey Batteries and a NOCO Genius onboard charger.

I knew he was just poking the Expo Bear.

www.expeditionportal.com

 

[DaveInDenver]

It's very difficult to get even a smart alternator charging system to really maintain and condition batteries.

One is that what exactly *is* ideal depends on too many things. What's perfect for an Odyssey isn't for an Optima or plain flooded. So the OEM builds a charging system for the lowest common denominator, which is the battery they install at the factory. It's about keeping the battery charged enough to do the tasks they ask of it under typical driving conditions.

Factor in, too, that "smart" in this context is a system design. They want to charge enough without overtaxing the engine. They are interested in using the engine power to move the vehicle at the best MPG and lowest emissions and not just spinning the alternator. So smart alternators are trying to balance keeping the electrical system just functional enough and nothing more.

That's where the DC-DC charger comes in. This decouples the battery charging from the energy generation. The alternator only needs to produce sufficient constant power, the actual voltage and current isn't important. The device converts the power the charging system makes into the right voltage and current the battery needs. Nice chargers are usually capable of being tailored to a specific chemistry or brand, even.

Your charging system does this to some extent but it's mostly designed to bulk as much as possible to get back to 80% or so, which is enough to keep starting your engine each morning. But it's not trying to ever achieve 100% charge and doesn't really care to coddle exotic batteries to get maximum life.

How you drive is the other problem. You see the Odyssey profile, it requires 8 hours of absorption at 14.7V nominal. Are you even normally driving for 8 hours, much less at an RPM sufficient to guarantee that voltage and current? Very, very unlikely on a daily basis.

That's where the shore charging comes in, whether that's mains or perhaps a permanently installed solar panel. No matter how you actually do it to keep batteries happy you need some sort of solution to provide regular and consistent energy over long periods.

 

[4000lbsOfGoat]

The Noco chargers charge at 14.8 in AGM mode and while it is not listed it sounds like they float charge at the desired 13.5-6

Noco chargers *do not* float. I have a GenPro 10x2 in my trailer. I too expected that it would float, but they do not - by design.

From Noco support:
"Our chargers do not use a traditional float voltage. Instead they remove the charge once it is complete and go into a low energy maintenance mode where they monitor the battery. If the battery voltage drops below its resting voltage (approximately 12.8V +/-0.2V) the charger will top the battery back off to full. This is a better maintenance charge for the battery than a constant float voltage."

That behavior may or may not work for your use case but it's good to know.

 

[DaveInDenver]

Noco chargers *do not* float. I have a GenPro 10x2 in my trailer. I too expected that it would float, but they do not - by design.

From Noco support:
"Our chargers do not use a traditional float voltage. Instead they remove the charge once it is complete and go into a low energy maintenance mode where they monitor the battery. If the battery voltage drops below its resting voltage (approximately 12.8V +/-0.2V) the charger will top the battery back off to full. This is a better maintenance charge for the battery than a constant float voltage."

That behavior may or may not work for your use case but it's good to know.

That's interesting to know. Noco should perhaps not make absolute statements because "better maintenance" to Odyssey seems to contradict that statement. They recommend a continuous float and even say to not let your battery dip below 13.2V on float. In the end you really do have to watch the details and tailor your system around idiosyncrasies of the stuff you choose. Really the thing I wish all manufacturers did a better job of is giving technical specifications just so you know. But especially chargers, it's sometimes hard to really tease out exactly the profile they're doing and what options you have to adjust values.

FWIW @wADVr, this chart is a good visual to charging voltages. Understand too that cyclic and float are both kind of true depending on your situation. Starting duty is more like float than cyclic since the battery rarely gets a real deep discharge. But it's also potentially just sitting off a charge but with a parasitic load, which is hard on them and if left long enough would be a deep cycle.

 

[wADVr]

4000lbs of goat: Good info thank you.

This is getting more difficult to solve. Hoping I could run an on board charger so I could just plug it in like a block heater seems to be a challenge, will need to broaden my search. My immediate issue is bringing the starter battery to a full charge not the aux until I actually use the Jeep for camping. Because now I'm obsessed slighting I tested voltage again this morning prior to starting the Jeep: 12.3V on the starter and 12.77 on the aux @ 42 degrees. At this rate ill have a wasted battery in no time. I am hoping to find a long term solution for all situations, although it seems I should either stop driving the jeep to work and/or get a normal flooded starter battery to run direct off the vehicle charging system..

 

[DaveInDenver]

It can be confusing but don't get too wrapped around the axle. Knowing that you need to be more diligent puts you steps ahead of the curve.

So even if the Noco doesn't perfectly follow Odyssey's advice it's probably still better than doing nothing.

If you want to do it exactly right Odyssey sells their own chargers, which you have to guess would be the best option. But if they don't have an option that suits then just realize that there's details you have to figure out for whatever brand and model you're considering is all.

 

[john61ct]

A charger that doesn't even drop to Float is not suitable for lead batts IMO.

Volts are volts, amps are amps.

A good charger accepts custom user adjustments to match the target battery profile.

Automotive chargers are not, if you choose your battery to match their output then you are OK, but IMO that is putting the cart before the horse.

But with most modern vehicle charging circuits these days (which suck if you care about the battery) that's what you're stuck with.

Or put in a DCDC.

Which BTW when parked you can feed from any stupid old garage charger.

 

[DaveInDenver]

A good charger accepts custom user adjustments to match the target battery profile.

Examples?

I can think of the Victron Phoenix Smart or Blue Smart. I'd like to know of others.

 

[john61ct]

You mean AC-DC?

Sterling Power ProCharge Ultra and

ProMariner Pronautic P series

 

[DaveInDenver]

You mean AC-DC?

Sterling Power ProCharge Ultra and

ProMariner Pronautic P series

Yeah, mains powered. Maybe not quite as large as those, which are intended as permanently mounted marine bank chargers so would be difficult to accommodate in @wADVr's Jeep. Not all of us are driving ex-Army FMTVs or large vans after all.

They both appear to offer several profiles with the ability to customize the voltage and current if you want. I'd like to know if there's any chargers that actually allow you to program in a profile, specifically giving you control over time or perhaps just what parameter triggers each step.

For example, neither of these (indeed none that I know of) appear to allow telling the charger to stay in absorption per Odyssey's recommendation, which is either 0.1% of the C10 rating (e.g. 4mA for a PC1200) or held to a maximum of 8 hours if that current isn't reached.

That's a frustration I have with the BatteryMINDer I use now. It uses fine voltages (14.7/13.6 @ 25°C) and a temperature compensation (25mV/°C over -20°C to +50°C) but seems to triggers the end of absorption at 100mA. So it kicks down to float a little early. Sure, it's probably marginal but at about 4 years old my Odysseys are starting to show more aging than I'd like and I can only wonder how much difference it's made not holding absorption fully.

There are some chargers that give you the ability via DIP switches to set absorption time, but I haven't seen any that allow tailoring any further than that.

 

[john61ct]

The usual best practice with trying to hit a specific endAmps range is trial and error using whatever AHT algo offered, until you measure it's holding long enough

then just checking every say 20 cycles to verify still on track.

The ability of the automated charge regulator to actually control charge termination directly off trailing current measurement

is very rare, usually requires Battery Monitor / remote control add-ons to the already very expensive base system.

Magnum combi units for example, a few high end solar controllers...

But I believe the Victron BMV 712 relay circuit can? Apparently they removed that from firmware a few years ago, but might have put it back by now.

A DIY Arduino setup could do it too.

 

[john61ct]

If you get say a Sterling BB DCDC unit setup to make a given bank happy

just feed all other sources through it.