Multi-Battery System | Looking for input

[SmokingRocks]

Hey guys, so I have a three-battery system, multiple isolators, and 200 watts of sollar in my cruiser currently and it's been working well for the last 5 years. Now it's time to start looking towards replacing some of the batteries and I wanted to get yall's input on my setup and what (if anything) can be improved.

So below I've attached a simple schematic of how my system is wired currently. Solid red lines indicate positive paths that can move in either direction, dashed lines indicate positive loads only. I've left out breakers and various other protection devices to try and keep it as simple as possible. That said this layout has worked quite well for my intended use.

Before we get to the schematic let me state the goals I was shooting for when built this system;

1. Always have a fresh and charged starting battery
2. Have the ability to manually link all batteries if desired
3. All batteries must automatically isolate when no charge is present
4. Have 2 sources of charging (Alternator & Solar)
5. Front House Battery is intended to be used at camp for extended periods for aux lights and stereo (if it's that kind of party)
6. The rear Battery is intended to be the sacrificial battery that took the constant cycles the two fridge/freezers would put on it, thus extending the life of the 3x more expensive main house battery

View attachment 2680132

This has worked well, just this last year I added the Victron MPPT Bluetooth controller which has smart charging profiles and would've probably extended the life of the 35ah Deep Cycle better than the previous PWM controller.

But in short, the solar floats up the rear battery, then the blue sea isolator links the rear house bat to the front house batt and once that hits float it links the starter battery and tops it off. Has worked well since all the batteries are roughly the same style (only the rear one is a dedicated deep cycle). When the alternator is spinning it charges up the front house battery first then links both the starter and rear house battery sending charge to them if needed.

So 5 years on and the rear battery is tired and the front house is showing its age. Then the question you might ask is 'if it worked so well, how could that be any better?' Short answer because I can't help myself. But moreover, there are a couple of things I'm considering;

• 35ah rear battery is way undersized (most of you know you only can really use 50% of the advertised ah rating of a lead-acid battery so really it's a 17.5 ah battery)
  • I have a 75ah AGM dual-purpose battery in my amazon cart that would work great in the back.
• My alternator puts out 14.3 volts ish, these batteries really need 14.8v to charge correctly, however technically my Victron has the charge profile for these batteries and when they are all linked (solar panels in full absorption) it should maintain them well enough?
• I can get a true deep cycle 95ah replacement for the front house battery for $114 vs $380 for another x2power (that said the x2power has performed very well soo that's something to consider before changing direction)
  • An additional consideration is that it's usually not ideal to use different battery types, capacities, and makes in systems that link in parallel for charging unless you have a DC-DC controller between them...

What are my options?

well, I was looking at the Renogy DCC30S DC-DC charge controller with an integrated solar MPPT controller to replace the Victron & Blue Sea 7600 smart isolator.
PROS:

• Retains the isolation functionality of the system when no charge is present
• It has adjustable charging profiles based on battery type so it will properly charge the rear deep cycle battery
• Replaces two components for one
• Will 'reverse charge' / trickle charge the front house battery once the rear battery is maintained

CONS:

• It only addresses the rear deep cycle battery and doesn't do anything for the others as far as providing a correct charge profile
• Its some money
• I would lose the low volt cutoff functionality of the Victron in the event the fridges draw down the battery too much
• Would need to upsize my wiring/breakers to the front house battery & run the alternator wiring to my box in the rear

Here's a schematic of that
View attachment 2680140

Ideally, I'd like to:

1. Change all of my batteries to dedicated types that fit their roles better
   • change my starter battery to a true starting battery and not a dual-purpose unit
   • Make both house batteries true deep cycles

Thoughts? Any other ideas? or should I just stick with the way it is and increase the capacity of my rear battery?

 

[renago]

May I ask you what kind of ah /day do you get from your solar panels ?
The reason is I am in the process of installing them and doubtful of the real power I need .

Thanks for your input .

 

[renago]

I drop in my experience , have 2 yellow Optima 75ah hooked up together .
These run starter , fridge,lights , water pump ,and recharging phone,cameras,computer,gps.
Stay put now, they are 16 years old !!!!
But tired now.
The first 10 years I had on top of my roof tent maggiolina also 2 small solar panels , and they topped up nicely the batteries .now only motor alternator.
Traveling in very remote areas , I am a fan on KISS, keep it simple and stupid .
In order to minimize any inconvenience and failure.
With 200w solar panels I would use just 2 batteries ,hooked up together .
You can easily put 100ah x 2 in your car, and have effectively 100 ah of usable energy, that's a lot .
Buy good quality battery, in the long run ,they are cheaper.
The solar panels Should be enough to recharge the batteries even if you stay camping for 1 week in th same spot ,without moving.
You gain semplicity in the system ,less expensive , easier to maintain and inspect,save space in the cargo area.
In practice you don't run out of juice for starting the vehicle.
Just my experience .

Renago

 

[SmokingRocks]

Final layout / one-line diagram for the revised rear battery bank

So let's break down the cost of this system and the pros/cons vs a new larger deep cycle battery:

Cost

Lithium Battery Option​

ITEM	PRODUCT INFO	COST	Notes
Battery - 18 amp-hour reserve	RoyPow S1218 | LiFePO4 Battery with Built-in Battery Management System	$110	Amazon buy, $20 discount with Honey app
Battery - 18 amp-hour reserve	RoyPow S1218 | LiFePO4 Battery with Built-in Battery Management System	$110	Amazon buy, $20 discount with Honey app
Battery - 18 amp-hour reserve	RoyPow S1218 | LiFePO4 Battery with Built-in Battery Management System	$110	Amazon buy, $20 discount with Honey app
DC-DC Charge Controller	Renogy DCC30s with MPPT Controller	$212	Amazon (memorial day sale 15% off)
MPPT Solar Charge Controller	Victron Energy SmartSolar MPPT 75|15	($100)	sold for $100
	Total:​	$412

Sealed Lead Acid Deep Cycle Option​

ITEM	PRODUCT INFO	COST	NOTES
Battery - 76 amp-hour reserve	X2Power BCI Group 24M 12V AGM	$350	60 lbs, largest amp-hour reserve for an SLA battery that would fit in the rear box
	Total:​	$350

Sure I could have used a cheaper true deep cycle battery for this cost comparison. But to do it properly I'd still need to get a charge controller to charge and maintain the different battery types.

Lithium PROs​	Lithium CONs​
~30% more usable amp-hour capacity than the SLA battery	Upfront cost
Rated for 3500+ cycles | 10 Years	Requires DC-DC charge controller to charge and maintain bank
Should retain 80% of charge capacity after 2,000 cycles	Can't charge below 32* F (0*C)
Can be used to 80% depth of discharge repeatedly without impacting life expectancy
Discharge voltage remains constant as the state of charge decreases
15 lbs total weight (all three batteries)
Built-in BMS with Low temp charge cut-off, low voltage disconnect, overcurrent protection
Ability to quickly recharge when depleted

AGM Deep Cycle PROs​	AGM Deep Cycle CONs​
Cheaper initial cost​	4x heavier than the LiFePO4 option (60 lbs)
No need for a special charger if matched with other batteries it's being charged with	Loses 20% of charge capacity after only 200 cycles
	Easily damaged / life shortened if taken below 50-80% depth of charge
	Discharge voltage decreases as the state of charge decreases
	Recharges slowly

Examining all of the info and cost lead me to choose Lithium over sealed lead-acid. I'm happy with this decision and am excited to see how it works out.

 

[SmokingRocks]

May I ask you what kind of ah /day do you get from your solar panels ?
The reason is I am in the process of installing them and doubtful of the real power I need .

Thanks for your input .

I don't have a data logger so I can't tell you with accuracy, however, based on my experience the solar has been able to keep my fridges at 0° C even when the cab gets up in the 50° C range on the hottest summer day with the windows up. It was very common for me to come out to my vehicle and see that all three batteries were linked and charging because there was so much juice.

Initially, I started out with a single 100w panel and a PWM solar controller, it worked just fine for 80% of the time, the best that setup could harvest was 6 amps. My fridges draw about that much each when they are on which on a normal day 20°C (68°F) day is about 30% of the hour, so on hotter days when their duty cycles increased to 50% or 75% the panel simply couldn't keep up.

So I added the 2nd panel, wired them in series, and upgraded to an MPPT controller. This worked great and really I didn't need to change anything except for the 3rd battery because it was worn out. Since I needed to replace that battery I naturally wanted to upgrade it, a 35ah SLA AGM only has about 17ah of usable energy under perfect conditions which is really not even worth it's weight.

Lastly, the point of the rear battery bank was to keep the constant cycles of powering the refrigerators off of the two expensive group 27 batteries up front.

I drop in my experience , have 2 yellow Optima 75ah hooked up together .
These run starter , fridge,lights , water pump ,and recharging phone,cameras,computer,gps.
Stay put now, they are 16 years old !!!!
But tired now.
The first 10 years I had on top of my roof tent maggiolina also 2 small solar panels , and they topped up nicely the batteries .now only motor alternator.
Traveling in very remote areas , I am a fan on KISS, keep it simple and stupid .
In order to minimize any inconvenience and failure.
With 200w solar panels I would use just 2 batteries ,hooked up together .
You can easily put 100ah x 2 in your car, and have effectively 100 ah of usable energy, that's a lot .
Buy good quality battery, in the long run ,they are cheaper.
The solar panels Should be enough to recharge the batteries even if you stay camping for 1 week in th same spot ,without moving.
You gain semplicity in the system ,less expensive , easier to maintain and inspect,save space in the cargo area.
In practice you don't run out of juice for starting the vehicle.
Just my experience .

Renago

The old optima's were excellent batteries, however, since they were bought out their quality has slid down the hill quite a lot. Odessey / x2Power & Interstate are today's top dogs in the lead-acid battery world.


I hear what you are saying about KISS, there certainly is validity to building a rig that way. years ago I was bit by having a system I installed fail in the backcountry which caused other problems for me. I gained the following bits of knowledge from that experience:

1. Functions that are critical to the operation of the vehicle should be on their own harness, fuse box, and fusible link (in my case this is the stock harness)
   • I have a rule that aftermarket accessories, relays, lights... or anything else do not get tapped into this harness. (taps for relay signal references is ok)
2. Accessories/aftermarket electronic wiring is to be incorporated into ONE independent, well though-out, color-coded, labeled, mapped (EWD) harness with its own fuse/breaker/link
   • Construct the harness using color-coded wires, harness tape, wire loom sheathing, Deutsch connectors & heat shrink
3. Assign one battery to handle starting the engine and NOTHING else, therefore regardless of the state of the other batteries the engine will still start and you can charge (theoretically)
4. Resettable breakers are invaluable

I like all my creature comforts, so when I rebuilt my engine I took out my dash and removed the rat's nest of wiring which had been piecemealed together over time. I then painstakingly laid out, constructed, and installed a loom for all of my auxiliary switches, devices, lights, sensors etc. For overcurrent protection, I repinned a factory Toyota fuse block and installed it adjacent to the main engine fuse block.

Now all of my accessories, gadgets are independent of the vehicle's operation so if there is an issue I am never stranded, additionally, if I have an issue I can look up my custom harnesses electrical wiring diagram on my iPad and troubleshoot it. Lastly, the fuses and relays used in the auxiliary harness are the same ones used in the main engine harness so if I ever need a spare relay or fuse they are right there.

 

[renago]

I keep the stock wiring separate from the auxiliary stuff as well .
don't want to mess too much with the electrical stock system .
thanks for you input on solar panels ,
I was thinking to go Deka , but I am very tight on size ,we'll see ....

thanks

 

[jgranthevagrant]

I have the same rule #1 as Smoking Rocks. Nothing but stock for the starting battery. -30 starts with no block heater can be very challenging. I also run a second alternator to charge my house battery. Looking closely at solar because I want to add it at some point.

 

[yngmrostrvile]

I don't have a data logger so I can't tell you with accuracy, however, based on my experience the solar has been able to keep my fridges at 0° C even when the cab gets up in the 50° C range on the hottest summer day with the windows up. It was very common for me to come out to my vehicle and see that all three batteries were linked and charging because there was so much juice.

Initially, I started out with a single 100w panel and a PWM solar controller, it worked just fine for 80% of the time, the best that setup could harvest was 6 amps. My fridges draw about that much each when they are on which on a normal day 20°C (68°F) day is about 30% of the hour, so on hotter days when their duty cycles increased to 50% or 75% the panel simply couldn't keep up.

So I added the 2nd panel, wired them in series, and upgraded to an MPPT controller. This worked great and really I didn't need to change anything except for the 3rd battery because it was worn out. Since I needed to replace that battery I naturally wanted to upgrade it, a 35ah SLA AGM only has about 17ah of usable energy under perfect conditions which is really not even worth it's weight.

Lastly, the point of the rear battery bank was to keep the constant cycles of powering the refrigerators off of the two expensive group 27 batteries up front.


The old optima's were excellent batteries, however, since they were bought out their quality has slid down the hill quite a lot. Odessey / x2Power & Interstate are today's top dogs in the lead-acid battery world.


I hear what you are saying about KISS, there certainly is validity to building a rig that way. years ago I was bit by having a system I installed fail in the backcountry which caused other problems for me. I gained the following bits of knowledge from that experience:

1. Functions that are critical to the operation of the vehicle should be on their own harness, fuse box, and fusible link (in my case this is the stock harness)
   • I have a rule that aftermarket accessories, relays, lights... or anything else do not get tapped into this harness. (taps for relay signal references is ok)
2. Accessories/aftermarket electronic wiring is to be incorporated into ONE independent, well though-out, color-coded, labeled, mapped (EWD) harness with its own fuse/breaker/link
   • Construct the harness using color-coded wires, harness tape, wire loom sheathing, Deutsch connectors & heat shrink
3. Assign one battery to handle starting the engine and NOTHING else, therefore regardless of the state of the other batteries the engine will still start and you can charge (theoretically)
4. Resettable breakers are invaluable

I like all my creature comforts, so when I rebuilt my engine I took out my dash and removed the rat's nest of wiring which had been piecemealed together over time. I then painstakingly laid out, constructed, and installed a loom for all of my auxiliary switches, devices, lights, sensors etc. For overcurrent protection, I repinned a factory Toyota fuse block and installed it adjacent to the main engine fuse block.

Now all of my accessories, gadgets are independent of the vehicle's operation so if there is an issue I am never stranded, additionally, if I have an issue I can look up my custom harnesses electrical wiring diagram on my iPad and troubleshoot it. Lastly, the fuses and relays used in the auxiliary harness are the same ones used in the main engine harness so if I ever need a spare relay or fuse they are right there.
View attachment 2686220View attachment 2686221View attachment 2686222View attachment 2686223View attachment 2686224View attachment 2686225

Any images of your solar setup?

 

[SmokingRocks]

Any images of your solar setup?

I have the same rule #1 as Smoking Rocks. Nothing but stock for the starting battery. -30 starts with no block heater can be very challenging. I also run a second alternator to charge my house battery. Looking closely at solar because I want to add it at some point.

The new system ran flawlessly for the last 4 days out in Lockhart Basin, both fridges were set to and held 30° F (-1°C) throughout the 90°F (32°C) days. Even floated up the front house and starting batteries after about 3 hours of direct sunlight on the panels. I was also charging USB speakers and phones off the rear power ports, using the water pump on occasion, and running my tailgate lights in the evening.

I really need the Bluetooth module to come in for tracking since bank voltage is no longer an accurate metric for gauging the LiFePO4 banks' state of charge.

 

[SmokingRocks]

 

[yngmrostrvile]

I have similar setup. Researching my options for adding solar.

 

[SmokingRocks]

Nice, what are the specs on the battery. Do you have specific questions regarding solar? Whats stopping you??

 

[yngmrostrvile]

Nice, what are the specs on the battery. Do you have specific questions regarding solar? Whats stopping you??

138ah
The battery capacity has been good to run everything so far for a week. But I figured the size and price of panels these days, it would be a great option.
What panel(s) did you go with?

 

[SmokingRocks]

I have two 100w panels run in parallel mounted to my roof. I didn't save the info on the first panel I put on my rig (at the time I didn't think about keeping a log of my components which was a mistake). Both panels are 100w units with similar Vmp specs, the second one I added is a Newpowa NPA100-12H 100w panel. I chose that unit because I wanted to match the size of the other panel as best I could.

Here are the other items I purchased to install the panels.
Mounting Brackets:
XOOL Mounting Brackets

Riv-Nuts from McMaster Carr

Power Cable Pass-Through:
Cable Gland Waterproof Adjustable 3-13mm Cable Connectors

Solar Cable Crimper & Connections
Kohree Solar Crimping Tool

 

[SmokingRocks]

I have similar setup. Researching my options for adding solar.

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Do you like the Renogy monitoring screen? I got the BT-2 but was very unimpressed with the apps so I'm sending it back, however they have a note on the mppt dc-dc monitoring screen's product description that makes it sound like the monitor is not ideal for Li-ion batteries.

 

[yngmrostrvile]

I have the 500a battery monitor and the BT-2. The monitor works well. I have it tucked away with my inverter but it has an alarm for when house.battery discharges to a set point, large display of capacity and usage. The renogy app needs a bit of work, I mainly use it to monitor what the charger is putting into the battery while traveling. I do wish it showed the battery capacity in ah not just voltage.

 

[SmokingRocks]

Yea I was very unimpressed with both Renogy apps. So I'll just go with the monitor screen

 

[SmokingRocks]

I have been monitoring the temperature swings inside my battery box over the last several weeks and noticed it peaking as high as 130° during some of the 100° days. So I decided it would be best to provide ventilation to the box. The plan is to have a high static pressure case fan draw air from an intake under the rig (around where the spare tire used to live) and exhaust into the cab of the rig.

Here's the parts list:
Fan: Noctua NF-F12 iPPC 3000 PWM
Temperature Ramping PWM: Temperature Control Speed Controller
Heating / Cooling Controller: Inkbird Dual Stage DV 12V Digital Temperature Controller
Battery Heater: Facon 7-1/4"x25" RV Water Holding Tank Heater Pad

With this set up the batteries will be ventilated in the summer and heated in the winter. Should help keep them happy.

 

[LandLocked93]

Tried to read most of this. Ton of info from all of you.
Have you thought of moving to 24v? I'm running 2 - D4 200Ahr AGMs in series for all non-factory accessories.
Still building it all in, but been a year or so since the air system has been operational.
2 pumps and a 6 gallon pancake. Together they draw 12amps and I've been able to fill 5 - 33" tires from 0psi, twice, with no recharge needed, tho a 24v RedArc BCDC handles the recharging when it is. But only when the truck is running.
So the solar is where I'm at now...installing, wiring etc. What method of pass-through have y'all used to get power to/from the roof? Have a rack ready to install, and have "a plan" for the wiring to get from outside to inside tho it painfully requires penetrating the roof (and screwing with the headliner ).
There has to be a better way that still looks and performs well.

Fascinating journey, clearly. lol Re-reading to digest it all.

 

[SmokingRocks]

So I did think about going 24v but it complicated the charging from the alternator capability with additional components. Further, all my led lights that run off this bank are 12v rated, so it would add components on both sides. But I did consider it.

box ventilation and heating pad have been installed. The inkbird Hvac controller has set points I can customize to when it will power on the fan or heating pad.

When the fan circuit is powered on it runs through a temperature sensing PWM controller that controls the fan speed from 20%-100% depending on the temp inside the box. It’s the black box that’s screwed to the far wall in the photo below.

What you can’t see in these photos is how the subwoofer sits in the box. It creates a barrier directly between the fan and the PWM controller from the bottom of the box to the lid and extends to within 3” of the back (right side in the photo above) of the box.

so I cut exhaust ports to the left of the PWM controller on the front face of the storage box, passenger side of the sub woofer hole. This way the air has to snake through the box and past the temp probe of the PWM.

I still would like to have the fan pull air from under the vehicle (shaded area, probably the coolest when it’s sitting in the sun) and I want to add a dust filter.