2022 KISS Dual Battery (3 Viewers)

[TeCKis300]

No surprise but batteries have taken an giant leap in technology, availability, and cost. I've been playing with all too many battery systems between work, my travel trailer, home, and EVs. Time to bring the LX overlanding setup into 2022. I'm a big proponent of KISS. Working in the engineering world, I've seen all too many complicated systems dreamed. In my mind, a sophisticated system can be one where less is more - with lifecycle benefits to installation, maintenance, and use. Objective is to install a house battery for $500-650 depending on capacity and specific parts.

Major update for 2022 is the availability of LiFePO4 batteries at commodity prices (~$300 for 100Ah). LiFePO4 batteries are a unique chemistry from standard lithium, i.e lithium-ion (li-on), which arguably started the battery revolution. Both flavors are compact, high energy density, sealed (AGMs are only partially sealed and can vent when overheated which is why they should not be mounted in the interior). LiFePO4 has the additional benefit of longer cycle life and heat tolerance over li-on. This makes it well suited for install in the cabin. The discharge curve looks very much like a classic flooded lead acid battery making it relatively easy to discern state of charge (SOC).

This setup is easily expanded to accommodate solar, inverters, etc. This would be a very high performing house battery, especially when compared to the traditional dual AGM based batteries. Lithiums have full use of stated capacity vs generally 50% for traditional batts. 100Ah is enough to power a fridge and misc electronics for a long weekend of stationary camping. Solar (installed or portable) would be a great way of expanding reserve without installing larger batts. If overlanding with driving mixed in, could last indefinitely (without solar) to power power hungry gear like heated blankets, etc. In my camping, I've found little use for inverters and 120V gear.

In a hat tip to KISS, this setup avoids a separate ground bus. Technically no reason to run an isolated house battery network, and the common chassis ground can be used across both banks, negating a need for a ground bus bar or extra negative wire lengths. You also won't find extra battery monitors or shunt meters. Sure they can be used, but a simple voltage readout as part of a USB socket or panel mount is all that's really needed to discern LiFePO4 SOC, as we use to for flooded lead acids.

Note that lithiums in general should not be installed in the engine bay as they aren't tolerant to the types of heat that can be seen in slow crawling. Temps that can exceed 160°F and damage the battery. This is also true for AGMs. People may do it, but it will lead to premature wear and damage, especially for those that live in warm climates and partake in slow driving activities.

Parts list, example links:

1. 50Ah - 100Ah LiFePO4 battery (~$200-350)
2. Victron DC-DC 12V/12V 18A Smart charger ($170)
3. Resettable fuse 50A, or depending on system sizing or loads, x2 ($20)
4. 12V fused distribution block ($12)
5. Socket panel mount ($20)
6. Misc wire and hardware ($80)

Schematic

2018 Edition of KISS Dual Batteries

KISS Dual Battery Upgrade

There’s been a lot of discussion on batteries and battery systems. Here’s my attempt to offer an easy button. The task of a battery first and foremost is to offer power and reserve capacity. There’s many battery setups and systems talked about. But perhaps some of those are solving a problem...

forum.ih8mud.com

 

[TeCKis300]

My setup is mostly KISS, but there were some elements that I already had from other projects that got used. Space utilization was the big priority for me. So KISS and using minimal parts helped that.

House battery, Victron charger, and distribution tucked here with an aluminum beauty panel over top. The LiFePO4 battery I sourced is a non-standard format with terminals on the small face. To minimize storage interference. It interestingly has USB ports and a voltage readout as part of the BMS. I like the little cubby nearest the back where I can dump camp lights or other gear I'm charging.

Dual purpose breaker and master on/off switch for the house battery.

Usable flat space over wheel well alongside fridge slide

 

[Mogwai]

Nice this is good upgrade to your original KISS - does that battery fit into the typical passenger side dual-battery spot (for example w/ Slee tray)? One comment on that battery, the BMS is set to allow discharge down to 10v which is pretty much 0% capacity, they even say you'll only get 2000 cycles vs 8000 (@50% discharge). Optimal is prob discharge voltage of 12.9v/20% so I'd keep an eye on that.

Any thoughts of just not connecting it to your truck at all? In the end this is the route I went, left my standard dual battery setup as just a backup starter battery but if I didn't have this I'd prob still have gone this route, and keep one of those jump starters in the center console. I also added the ability to charge by plugging into an extension cord or solar, but this is also a downside as I don't have the ability to charge via alternator unless I added a unit like you have w/ the victron. Allows me to keep the fridges on while at home though, which I wanted since I don't always drive the truck often. It's still very KISS and bonus you can take it out of the truck if I want it to sit somewhere else at the campsite or need a mobile power solution.

If you're handy (I know you are, this is just a general statement) for about the same prices you can get (4) 280ah cells off Alibaba, add a BMS (also off Alibaba) and have 2.5x more power and a configurable BMS. This setup won't fit under the hood unless you really move stuff around. Anyway, your revised KISS setup is great and prob the best solution for 99% of us.

 

[TeCKis300]

Nice this is good upgrade to your original KISS - does that battery fit into the typical passenger side dual-battery spot (for example w/ Slee tray)? One comment on that battery, the BMS is set to allow discharge down to 10v which is pretty much 0% capacity, they even say you'll only get 2000 cycles vs 8000 (@50% discharge). Optimal is prob discharge voltage of 12.9v/20% so I'd keep an eye on that.

Any thoughts of just not connecting it to your truck at all? In the end this is the route I went, left my standard dual battery setup as just a backup starter battery but if I didn't have this I'd prob still have gone this route, and keep one of those jump starters in the center console. I also added the ability to charge by plugging into an extension cord or solar, but this is also a downside as I don't have the ability to charge via alternator unless I added a unit like you have w/ the victron. Allows me to keep the fridges on while at home though, which I wanted since I don't always drive the truck often. It's still very KISS and bonus you can take it out of the truck if I want it to sit somewhere else at the campsite or need a mobile power solution.

If you're handy (I know you are, this is just a general statement) for about the same prices you can get (4) 280ah cells off Alibaba, add a BMS (also off Alibaba) and have 2.5x more power and a configurable BMS. This setup won't fit under the hood unless you really move stuff around. Anyway, your revised KISS setup is great and prob the best solution for 99% of us.

I'm actually using a different battery than the one I linked as I needed a specific form factor. Don't really recommend them as they initially shipped me a battery that was fully discharged (into BMS protection). But the battery was pretty unique with high quality stainless case, built in meter, USB sockets, looked to be for a specialized OEM application. Will post pics of my install later.

I think it would be easy to find one that could fit the engine compartment. I would caution that position for heat and cold, though if one must, could probably really benefit from a heat shield.

Good point on the BMS protection. Even 2000 cycles is 5yrs of everyday use. I'll likely not baby the battery as there will likely be even better tech then. That said, the primary load is my Iceco fridge which has a built in settable low voltage cutoff.

As for not tieing into the car, surely that's an option. Or tie in only with solar. I find having flexibility and a balanced solution to be best. It's easy to get sucked into the bigger is better and get hung up over say a 30amp DC-DC monster.

I've had a 1000 Goal Zero lithium for the last 4 yrs of camping, with only a 5A DC-DC charger and it did great for my use. Only used the portable 100W solar on a few occasions.

I have a home charging solution that I'll post a pic of tonight.

 

[dubyahard]

I've thought of doing the segregated version using solar. Right now, my solar just charges a primary/solo G31 AGM with a Overland Solar MPPT. I'm considering a Lithium batt in the back connected only to the solar and a panel to plug in the fridge, USB-A/USB-C and shore power. I already have a lithium jump pack. As I already have power to the rear, I could just add the DC-DC controller later, at any time.

I also live in Portland, so not really realistic to have only the LiFePo4 100Ah running the fridge non-stop with no charge from the truck.

 

[sdnative]

This looks familiar.

I thought you were a big fan of the power station (Yeti, etc?) Why the shift?

I am not a fan of those resettable circuit breakers. Maybe just bad luck, but I have had two fail (installed in engine bay next to starter battery). I am changing to a fuse (probably MRBF) and marine battery switch for the cable from the engine battery to charger.

I believe the 12-12/18 is only available in isolated. Easy to connect the input (-) and output (-) to convert to non-isolated if desired.

I would recommend at least 6awg (or even 4awg) if installing in the back to minimize voltage drop.

I wouldn't rely on voltage to determine LiFePO4 SoC. Charge/discharge curve is too flat for most of the range.

What about short circuit protection? While lead acid's higher internal resistance is somewhat self-limiting, LiFePO4 can deliver massive amounts of current in a short circuit.

Looking forward to see where this goes and maybe learn some tips and tricks.

 

[Sandroad]

Nice. Love the KISS thing with electrical work. I’m in the process of redoing my off-grid cabin solar system using rather extreme KISS principles. I would only comment that terminal voltage under load is a pretty crud SOC measurement for any battery. I’ve found in real world applications that LiFePO4 batteries experience less voltage sag under load and voltage falls off fast at the end of the discharge cycle compared to AGM. So, I think it takes some practice to get a feel for voltage as a SOC proxy with LiFePO4 batteries if you’re used to using that for AGM batteries. I’m not as familiar with FLA.

 

[sdnative]

If you're handy (I know you are, this is just a general statement) for about the same prices you can get (4) 280ah cells off Alibaba, add a BMS (also off Alibaba) and have 2.5x more power and a configurable BMS.

As someone who has built and uses a DIY LiFePO4 battery in my truck, I'm not sure I would do it again. If this were in a trailer, then probably, but not in the truck with the typical loads. I would probably just get a 100Ah battery from one of the major manufacturers (Battleborn, Renogy, etc).

 

[Fisher23]

On your diagram there I think you mean to connect the #4 dist. block to the other side of the Breaker ... or to the Aux battery.

I had a 20amp charger and then swapped it out for a 40 amp, price was near the same and the charge 2 times as fast.

My setup is near what you have there .. but I have breakers at both ends of the run from the Main battery to the DC/DC charger. I think I may of had power on the input of the dc charger when hooked up to the aux battery if I remember right?

All that gear dc block and other things grounding I ran to a small marine ground bar then grounded the bar.

 

[TeCKis300]

This looks familiar.

I thought you were a big fan of the power station (Yeti, etc?) Why the shift?

I am not a fan of those resettable circuit breakers. Maybe just bad luck, but I have had two fail (installed in engine bay next to starter battery). I am changing to a fuse (probably MRBF) and marine battery switch for the cable from the engine battery to charger.

I believe the 12-12/18 is only available in isolated. Easy to connect the input (-) and output (-) to convert to non-isolated if desired.

I would recommend at least 6awg (or even 4awg) if installing in the back to minimize voltage drop.

I wouldn't rely on voltage to determine LiFePO4 SoC. Charge/discharge curve is too flat for most of the range.

What about short circuit protection? While lead acid's higher internal resistance is somewhat self-limiting, LiFePO4 can deliver massive amounts of current in a short circuit.

Looking forward to see where this goes and maybe learn some tips and tricks.

Great points. I still have my GZ Yeti 1000. Several things I'm looking to optimize
- As compact as the GZ is, it still takes up space. I have to position it in a way that protects the things plugged into its face, taking up more space. Generally not a problem until I try to host all 4 of my family in the LX over a long weekend where space gets tight. Since I've recently decided to forego an off-road trailer build, I'm putting effort into optimizing my loadout
- Camping in the desert in the summer on 95°F+ days can have the GZ running its cooling fans. When it's heat saturated, it'll do that into the evenings. This is at low draw not using the inverter. LiFePO4 has more heat tolerance which makes me more comfortable than carrying Li-on in the desert.
- I agree on the resettable breakers as engine bay heat should be considered a factor. May need to size up to account for premature tripping or buy higher quality units. I do like the resettable breakers for the switch function. In my own setup, the house battery DC-DC charger is actually powered by my solid state SwitchPros that has short, LVD, and other protections.
- I find voltage to be a good indicator for SOC in LiFePO4. Sure, it's pretty coarse, but with a generous 100Ah usable battery, I don't really find a need to have detailed SOC resolution. To @Sandroad 's point, it's actually more accurate than old school flooded lead acids, as voltage under minor/medium loads doesn't really change the voltage readout in LiFePO4. Agree it may take time to get a feel. From my 400Ah LiFePO4 install in my travel trailer with a shunt reference, I feel pretty comfortable reading voltage that cross checks well with the Ah meter.
- Yup to 4AWG and is what I've run from way back in the day anticipating future upgrades. Trying to keep KISS and cost, 8AWG is fine for the Victron 18A DC-DC charger, as it'll boost to the same output regardless of input voltage sag. Both Victron 12/12 18amp and 30amp units accept a max of 6AWG at its terminals, though surely one can run larger gauge and step down.

 

[TeCKis300]

On your diagram there I think you mean to connect the #4 dist. block to the other side of the Breaker ... or to the Aux battery.

I had a 20amp charger and then swapped it out for a 40 amp, price was near the same and the charge 2 times as fast.

My setup is near what you have there .. but I have breakers at both ends of the run from the Main battery to the DC/DC charger. I think I may of had power on the input of the dc charger when hooked up to the aux battery if I remember right?

All that gear dc block and other things grounding I ran to a small marine ground bar then grounded the bar.

Definitely could run the #4 distribution block the way you're suggesting. In my setup, I'm dual purposing the larger resettable breaker as a master off for the LiFePO4 battery.

More charging amps would be useful for higher demand use cases. I found my 5A DC-DC charger with my GZ Yeti to be all I needed. So 18A was a good balance for my setup of fast enough, cheap enough, with minimal space utilization.

I have another 20/40A DC-DC in my travel trailer, so wanted to make sure I don't overtax my alternator.

 

[Sandroad]

Good call posting the LiFePO4 battery SOC chart. Comparing it to the same chart for AGM batteries shows how very different they are. Someone familiar with AGM voltage for SOC will need to learn the new number for lithium.

 

[TeCKis300]

Posted pics of my setup in post #2.

Any thoughts of just not connecting it to your truck at all? In the end this is the route I went, left my standard dual battery setup as just a backup starter battery but if I didn't have this I'd prob still have gone this route, and keep one of those jump starters in the center console. I also added the ability to charge by plugging into an extension cord or solar, but this is also a downside as I don't have the ability to charge via alternator unless I added a unit like you have w/ the victron. Allows me to keep the fridges on while at home though, which I wanted since I don't always drive the truck often. It's still very KISS and bonus you can take it out of the truck if I want it to sit somewhere else at the campsite or need a mobile power solution.

For charging the aux house battery from an extension cord, I'm dual purposing the Anderson outlet ports on my power panel as inputs to the battery. Made a pigtail that adapts my Noco float charger SAE connector to Andersons. This will charge the battery and power/pre-cool the fridge prior to a trip if necessary. I'm borrowing my small 2A Noco from my other car for the moment but have a larger 5A unit coming in the mail.

The same Anderson port will allow my portable 100W solar panel to charge through. I can close the hatch with the power wire coming through.

With dual Anderson ports, should be able to support multiple charge sources. Using both the 5A and 2A Noco's simultaneously for example.

 

[sdnative]

- Yup to 4AWG and is what I've run from way back in the day anticipating future upgrades. Trying to keep KISS and cost, 8AWG is fine for the Victron 18A DC-DC charger, as it'll boost to the same output regardless of input voltage sag. Both Victron 12/12 18amp and 30amp units accept a max of 6AWG at its terminals, though surely one can run larger gauge and step down.

Yes a boost converter like the Victron Orion can and will compensate for low or high input voltage but I believe they do expect the voltage to be fairly constant over the range of charge current. So voltage loss is an issue. Typically size DC-DC wiring for less than 3% voltage drop.

I had my Victron Orion 12/12-18 wired with 8awg from engine bay to back (~20ft one way) and I was not satisfied with the performance. It would go in and out of engine off and low voltage detect as the voltage at the charger input terminals would fluctuate with load. I strongly recommend at least 6awg, even 4awg if possible, for longer wire runs.

Also, the charger can be configured to stop charging at a given voltage, but also need to consider something to prevent the battery from become over discharged. I am using the Victron Battery Protect and am happy with it. Just need to make sure it is wired properly (current can only flow from input to output).

This is an interesting video:

 

[TeCKis300]

Yes a boost converter like the Victron Orion can and will compensate for low or high input voltage but I believe they do expect the voltage to be fairly constant over the range of charge current. So voltage loss is an issue. Typically size DC-DC wiring for less than 3% voltage drop.

I had my Victron Orion 12/12-18 wired with 8awg from engine bay to back (~20ft one way) and I was not satisfied with the performance. It would go in and out of engine off and low voltage detect as the voltage at the charger input terminals would fluctuate with load. I strongly recommend at least 6awg, even 4awg if possible, for longer wire runs.

Also, the charger can be configured to stop charging at a given voltage, but also need to consider something to prevent the battery from become over discharged. I am using the Victron Battery Protect and am happy with it. Just need to make sure it is wired properly (current can only flow from input to output).

This is an interesting video:

Interestingly, I have a 20A DC-DC on my trailer as well, that's fed by the OEM 7-pin harness. The wire there is only like 12gauge. It's probably on the boundary but it works with full output.

To your point, for higher loads, wire gauge is something to be aware of. KISS is something to start from and should be tailored for different use cases.

Couple things that benefits KISS. The wire gauge takes in the totality of the circuit, including the ground path. You probably know this but for the benefit of others, it's the overall combined resistance. Half the circuit is the ground at the chassis which is the largest conductor in the system. A common shortcoming is resistance tieing into that ground path however. Bolt points need to have the paint scuffed or removed with a wire wheel to make sure paint or anti-corrosion coatings aren't adding to the resistance of the circuit.

 

[Mogwai]

As someone who has built and uses a DIY LiFePO4 battery in my truck, I'm not sure I would do it again. If this were in a trailer, then probably, but not in the truck with the typical loads. I would probably just get a 100Ah battery from one of the major manufacturers (Battleborn, Renogy, etc).

Curious why you say that? I've had my setup running for over a year and half, no issues (and it's def not production quality craftsmanship ). At the time the "Battleborns" of the world were ~$1k for 100aH.. I understand the prices have come down which is great so that may change things. My setup is not kiss, but as kiss as possible for what I wanted (I have two built in fridge "drawers"), together they draw 2x what your typical fridge would draw. I also wanted the ability to work from anywhere (AC). And much like not wanting to drive a truck I constantly have to work on our worry about breaking down, I also didn't want to worry about my battery getting drained, nor have to worry about powering while I'm out. This setup ran me ~$1k at the time. Now you can do it for ~$700. Some bonuses in here like 1k watt pure sine inverter, built in mpp charge controller, auto-switching of charge source and power sources based on what's available, etc... so again not quite KISS but it's only 4 components. The battery, the BMS, fuse block, and the all-in-one inverter/charger. 280aH, will ONLY run my setup for 4 days in 100 degree heat. It's also mobile, unsnap the andersons and go. Cons: heavy. and takes up more space than just a battery.

 

[TeCKis300]

Curious why you say that? I've had my setup running for over a year and half, no issues (and it's def not production quality craftsmanship ). At the time the "Battleborns" of the world were ~$1k for 100aH.. I understand the prices have come down which is great so that may change things. My setup is not kiss, but as kiss as possible for what I wanted (I have two built in fridge "drawers"), together they draw 2x what your typical fridge would draw. I also wanted the ability to work from anywhere (AC). And much like not wanting to drive a truck I constantly have to work on our worry about breaking down, I also didn't want to worry about my battery getting drained, nor have to worry about powering while I'm out. This setup ran me ~$1k at the time. Now you can do it for ~$700. Some bonuses in here like 1k watt pure sine inverter, built in mpp charge controller, auto-switching of charge source and power sources based on what's available, etc... so again not quite KISS but it's only 4 components. The battery, the BMS, fuse block, and the all-in-one inverter/charger. 280aH, will ONLY run my setup for 4 days in 100 degree heat. It's also mobile, unsnap the andersons and go. Cons: heavy. and takes up more space than just a battery.
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Kudos to homebrewing. I've considered rolling my own as recent as 2021.

I think market conditions have changed to @sdnative 's point. With the drop in prices, fewer people are building batteries from the ground up. It's so cheap to get an integrated battery with a compact form factor.

For others, there's some unique product opportunities. Some batts now have integrated heaters and BT enabled BMS with output of status and SOC. That might be an easy button for those that prefer a tightly integrated products minimizing external wiring and complexity.

 

[rlynch356]

I used a Renogy 100ah LiPo battery (with BMS and bluetooth as well).. they are reasonable at ~$500.. This is fed with a Redarc DCDC 40amp charger with solar input.
all built into the Goose Gear cabinets infant of the fridge, hidden, with an air vent on the charger.
I decided on a 4ga cable from the battery with circuit breakers at both ends of the cable, a blue sea fuse box and a Victron battery gauge (also bluetooth).
I am going to add a bit of gaurd behind the charging panel to keep stuff from hitting the cables (I store tools and stuff in that area)

 

[sdnative]

Curious why you say that? I've had my setup running for over a year and half, no issues (and it's def not production quality craftsmanship ). At the time the "Battleborns" of the world were ~$1k for 100aH.. I understand the prices have come down which is great so that may change things. My setup is not kiss, but as kiss as possible for what I wanted (I have two built in fridge "drawers"), together they draw 2x what your typical fridge would draw. I also wanted the ability to work from anywhere (AC). And much like not wanting to drive a truck I constantly have to work on our worry about breaking down, I also didn't want to worry about my battery getting drained, nor have to worry about powering while I'm out. This setup ran me ~$1k at the time. Now you can do it for ~$700. Some bonuses in here like 1k watt pure sine inverter, built in mpp charge controller, auto-switching of charge source and power sources based on what's available, etc... so again not quite KISS but it's only 4 components. The battery, the BMS, fuse block, and the all-in-one inverter/charger. 280aH, will ONLY run my setup for 4 days in 100 degree heat. It's also mobile, unsnap the andersons and go. Cons: heavy. and takes up more space than just a battery.

I don't necessarily have any issues with DIY battery packs. Mine has been mostly issue free. It was a little bit of a hassle trying to find good matched cells, building a proper compression rig, top balancing, etc. Not that this was difficult, and I enjoyed the process and learned a lot. But if I had to do it a second time, I probably would just buy a factory built battery.

I have always worried about using these particular cells in a moderately rough service application like a off-road vehicle. The terminals are small and seem to be delicate using M4 threaded connections. No issues so far though, but I dread having to remove the nylock nut from the stainless stud as I fear I will strip out the soft aluminum terminal. I would prefer cells with much beefier terminals like the Fortune with M10 studs, but those wouldn't have fit in my space.

I am also using solid pure C110 copper busbars. In hindsight I should have used tin plated copper as I am having some oxidation issues. I figure I'll need to remove the busbars and clean every couple of years.

I guess the short answer is there is just more maintenance and diligence required with a DIY pack (in my experience). The factory batteries seem to be just install and forget as long as the charging, distribution and protection is setup properly.

If I had to buy a battery today, I would seriously look at the Weize battery. Seems like a lot of bang for the buck.

 

[tbisaacs]

I don't necessarily have any issues with DIY battery packs. Mine has been mostly issue free. It was a little bit of a hassle trying to find good matched cells, building a proper compression rig, top balancing, etc. Not that this was difficult, and I enjoyed the process and learned a lot. But if I had to do it a second time, I probably would just buy a factory built battery.

I have always worried about using these particular cells in a moderately rough service application like a off-road vehicle. The terminals are small and seem to be delicate using M4 threaded connections. No issues so far though, but I dread having to remove the nylock nut from the stainless stud as I fear I will strip out the soft aluminum terminal. I would prefer cells with much beefier terminals like the Fortune with M10 studs, but those wouldn't have fit in my space.

I am also using solid pure C110 copper busbars. In hindsight I should have used tin plated copper as I am having some oxidation issues. I figure I'll need to remove the busbars and clean every couple of years.

I guess the short answer is there is just more maintenance and diligence required with a DIY pack (in my experience). The factory batteries seem to be just install and forget as long as the charging, distribution and protection is setup properly.

If I had to buy a battery today, I would seriously look at the Weize battery. Seems like a lot of bang for the buck.

I just dropped one of these in my setup