House battery bank replacement

sbiossat

Member
I have a 2015 144WB with a modular conversion. After a couple years of abuse of the house batteries (3 Optima yellow tops) and then sitting during the pandemic, it looks like my 3 optima AGMs are fried. I have 2 under the hood in one of Hein’s custom mounts, and one under the passenger seat. Do you have any recommendations for replacement, or should I just go with the same thing. Also, I am wondering if I added some solar if it will help to not have this happen so soon. I am in Chicago, so cold weather can be a factor for Lithium, although I have heard there maybe options for cold weather versions. I would prefer to not have to reconfigure a lot of the wiring and components.
 

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kcshoots

VanTripping.com
You can place up to four battle born lithium batteries under the slider door recess, laying sideways. Obviously there are other places. Within the engine bay is a hard place to live for any battery with the large temperature extremes, plus further away from your loads, which likely will be larger than the Sprinter alternator will provide as charge, so thus requires large cables than if further back. Yes there is space and it can work but if you can install them mid to rear underneath or inside for better weight and power load distribution.

Lithium batteriese do not have an issue in the cold, no worse than AGMs. They will not take much of a charge when cold, as neither do AGMs, but cold down to -20 to -40F will not hurt them, unlike it will with AGMs. Lithiums will continue to provide more available current at colder temps than AGMs by a large margin and to much colder temps. This coming from a guy that ran lithium battery production for two lithium battery companies.
 

Midwestdrifter

Engineer In Residence
Charging a lfp pack below freezing will permanently damage it. Typically a bms will disconnect is that happens. Not ideal.
 

erik.wahlstrom

Well-known member
Semi-related question. Reading the MB documentation on the AUX battery it says that they should be exactly the same as the starter battery. Is there any reason for this? Why couldn't I put a single large Lithium battery as the AUX?
 

marklg

Well-known member
Semi-related question. Reading the MB documentation on the AUX battery it says that they should be exactly the same as the starter battery. Is there any reason for this? Why couldn't I put a single large Lithium battery as the AUX?
They charge completely differently. On my T1N, the alternator does not stay up at a high enough voltage to fully charge a LiFePO4. Newer Sprinters have smart alternators that drop down voltage even more to save fuel.

Each battery wants to charge in a specific way. Putting them together will result in one not being charged enough or one being overcharged and damaged, or maybe both. I don't see paying $1000 for a LiFePO4 that should last a decade or more and charging it incorrectly so it lasts a much shorter time.

Regards,

Mark
 

sbiossat

Member
You can place up to four battle born lithium batteries under the slider door recess, laying sideways. Obviously there are other places. Within the engine bay is a hard place to live for any battery with the large temperature extremes, plus further away from your loads, which likely will be larger than the Sprinter alternator will provide as charge, so thus requires large cables than if further back. Yes there is space and it can work but if you can install them mid to rear underneath or inside for better weight and power load distribution.

Lithium batteriese do not have an issue in the cold, no worse than AGMs. They will not take much of a charge when cold, as neither do AGMs, but cold down to -20 to -40F will not hurt them, unlike it will with AGMs. Lithiums will continue to provide more available current at colder temps than AGMs by a large margin and to much colder temps. This coming from a guy that ran lithium battery production for two lithium battery companies.
Thanks for the reply. I do understand that they will still perform in cold weather, but it’s also my understanding that if you charge them below a certain temperature (I cannot remember what temp) the cells will crystalize and be permanently ruined.
 

Colorado_Al

Well-known member
If your system was designed for AGM batteries, I would just replace them with AGMs. You don't have to get Optimas though. There are many cheaper high quality AGM batteries that will also work.
 

sbiossat

Member
If your system was designed for AGM batteries, I would just replace them with AGMs. You don't have to get Optimas though. There are many cheaper high quality AGM batteries that will also work.
Thank you. Do you have any recommendations for specific brands of AGM that might be comparable to optima for replacement?
 

Midwestdrifter

Engineer In Residence
It sounds like you don't have much charging infrastructure at all. So you can use whatever battery works best. Consider a set of GC2 flooded batteries under the hood.

Add some solar. Depending on your usage case you should also consider adding a small shore power maintainer/charger.
 
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sbiossat

Member
It sounds like you don't have much charging infrastructure at all. So you can use whatever battery works best. Consider a set of GF2f flooded batteries under the hood.

Add some solar. Depending on your usage case you should also consider adding a small shore power maintainer/charger.
Thanks again. I do have a shore power charger, but unfortunately I live in Downtown Chicago, so I am unable to plug-in whenever I want. I really only use the shore power when camping at a site. My alternator is quite powerful, so when driving it sufficiently charges, but I think you’re correct that I do need to add solar to maintain/trickle charge consistently.
 

Midwestdrifter

Engineer In Residence
The T1N alternator does not produce more than about 14V, which is not sufficient for charging lead acid to 100%. If lead acid batteries are not charged to 100%, they sulfate, and die very quickly. LFP batteries do not suffer from this issue.

Despite what many drop in LFP makers will tell you. LFP batteries will charging to ~99% from 14V. So charging from the alternator can work fine, especially for a 100AH or smaller pack. In many ways an LFP battery would be superior for your usage, other than you won't be able to charge it if the battery is below ~38F.

Adding even a modest amount of solar will dramatically improve the life of your lead batteries, as they are likely simply never getting to 100% charge.

The quick method is 2 GC2 flooded batteries (sams club or batteires plus sell the duracell/deka brand). These are the best value at about 120$ each, and more durable than the AGMs you are using. Put these under the hood.

Then install a 100-200W solar system that reaches at least 14.,4V in absorb.

That should get you 2-5 years depending on usage and abuse.
 

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