KingArthur
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Let’s talk about battery chemistry.
The reason I ask this question is because I’m at a bit of an impasse. I’ve recently realized how little I know about the various types of batteries and how to correctly care for them. In this post, I’m going to put out there what I know and then hopefully someone will come along and enrich my knowledge and give me some advice or give me some specifications on their setups with pictures being appreciated. I would also appreciate if someone could point me towards more resources in learning more about battery chemistry and more specifically what different chemistries are more suited to certain situations and how certain chemistries respond to certain charging programs. What I mean by that is I’d like to know more about the intention behind bulk, float, trickle, etc etc. and the other charging jargon. Not only what it means, but what each phase is designed to accomplish any why.
I’ve seen plenty of videos on youtube and have read some posts and blogs regarding all these topics, but I’ve struggled to find anything really conclusive. So if there are any books or manuals that you could suggest, I would appreciate it.
Anyway, on to the batteries:
The way I see it there’s only four or five chemistries that van dwellers would be interested in at least at this point.
FLA, SLA AGM, Li-Ion (Cobalt), LiFePo4, and for fun I’ll throw in a category for what I’ll call ‘experimental’ batteries.
Each of these chemistries has a different character, and after I’ve found a good match to achieve my needs, I’m going to dive into researching and learning how to properly care for the chemistry I’ve selected.
Flooded Lead Acid:
These guys seem to be very popular on cheaprvliving right now usually as two golf cart batteries in series to achieve 12v. The advantage of this chemistry is that it seems to be more forgiving than any of the other chemistries when it comes to over-discharging and incorrect charging methods. They are significantly cheaper than any of the other batteries I have listed, and they are readily available at common retail establishments, making them easy to replace. The disadvantage of FLA is the hydrogen gas that is created during charging, the necessity of maintenance, and the possibility of spillage. These batteries are also the heaviest compared to the usable amp hours provided.
Sealed Lead Acid Absorbent Glass Mat:
Another really popular battery in the van dwelling community at large. They have the advantage of being completely sealed and can be mounted in any orientation. They do not require any maintenance. They tend to be more expensive than their FLA counterparts however, and are less forgiving to abuse. Seeing as they do not release gas when charging, they are great for small enclosed environments where venting is either impossible or inconvenient.
Lithium Cobalt:
I haven’t seen anyone personally using a lithium cobalt bank for their house battery but these cells deserve a mention. They are used frequently in EV and electric bike applications, usually in the form of the 18650 cell. Tesla is currently using these types of batteries to power its cars. They are commonly found as laptop and flashlight batteries. These batteries have an excellent energy density, tolerate a much deeper depth of discharge, and have an astronomically longer cycle life than any lead acid battery. The disadvantage of these batteries is their nominal voltage of 3.6v, making it difficult to use them as a house battery for a 12v nominal application. They also are more prone to explosion than any of the other chemistries. One must also be willing to buy the cells individually and either solder or spot weld the desired sized battery together, seeing as readymade Lithium Cobalt house batteries are obnoxiously expensive.
Lithium Iron Phosphate
These batteries are most likely going to continue to replace lead acid batteries in many application, house batteries being one of them. They have an excellent nominal voltage of 3.2v, have an excellent cycle life, are very stable and safe, lightweight, sealed, and have an energy density close to lithium cobalt. The downside is that they are close to prohibitively expensive, may require a battery management system, and are not supported by most solar charge controllers without a programmable function. I’m not sure if it’s safe to link these guys to your alternator either.
Experimental batteries:
Zinc battery
The Oasis battery
I know nothing about these other than they make wild claims and I have no idea if they are credible.
So here’s what I’m trying to accomplish. I want to put an air conditioner in my van this summer. I have a 2000 Chevy astro, very well insulated with reflectix on walls, roof and floor, 4” of denim insulation in the walls and 2” on the floor and ceiling. Also nine cans of window sealer sprayed into every available crack. The space is very small, so a modern energy efficient air conditioner should only have to run sparingly to keep the space cold.
There was a really interesting van tour done on a guy I’ll called hurriedyear. He has a website with the same name where he has an extrapolation of his entire van laid out for our viewing pleasure. He has a 2006 Sprinter with a 960w system, and 780aH of SLA batteries he uses to power everything in his van, including an induction cooktop and an 8000 btu air conditioner. He can run his air conditioner non-stop for about five hours before running through his useable capacity of 390aH.
I have the advantage of having a smaller space, and I believe slightly better insulation. I will also be using a window unit instead of a portable unit, which is less efficient than a window unit. My air conditioner pulls 45aH @ 12v per hour while the compressor is running. My goal is to be able to leave the air conditioner on overnight, I would assume on the hottest night probably only running with the compressor on for a total of three hours.
My van had 520w of solar on the roof (the whole roof, lol), which I think will be sufficient even if the weather isn’t perfect. I have a 40A solar charge controller that is just an amp or two underweight for the peak efficiency of my panels, but I doubt I’ll hit peak efficiency anyway, so I don’t think it’ll ever see a 40A charge. The van is wired with 0 gauge pure copper, and I have a 1500w/3000w peak inverter to power my laptop, TV, and hopefully soon my air conditioner.
So that leaves one thing… batteries, and which to get.
At this point I think I should shoot for at least 300 useable amp hours of power. More is better. 500 is probably the upper limit; it’s definitely more than my panels would be capable of generating on even a perfect day. So that means I’m looking for a battery bank that has a capacity of 600-1000Ah at 12vdc.
That’s a big ol battery bank….
My van is very small. It’s too small to fit 8-10 golf cart batteries, and also ventilation = air loss = reduced efficiency, so FLA for me seems to be out of the picture.
SLA is a little more attractive, and probably the cheapest route at this point… however, these beasts( http://www.apexbattery.com/apex-apx12-260-12v-260ah-group-8d-agm-battery.html ) weight almost 150lb each and I would need 3 of them to hit my target of useable aH. Neither me nor my astro is interested in adding 450lb of lead and acid to our lives, and really I don’t think I have the space for those monsters. I would, however, go this direction if I had no other choice. I could make it work.
So that leaves the lithium batteries. They are very expensive, but they are excellent batteries. They are the most likely to be able to survive the abuse of running an air conditioner regularly. LiFePo4 is probably a better choice over making a pack out of 18650 cells, but I’m leaving the option on the table, just in case I really want to punish myself.
So I guess this is where my question actually beings (sorry!). Do you see anything I’m not seeing? Do you think I’m crazy? Do you know any nuances about LiFePo4 cells that I don’t know? Where to buy them? Where not to buy them? Do you live on the east coast and could I come look at your setup? I’m really just looking for more advice before I dive headlong into such an expensive and uncharted territory.
If you made it this far you have my deepest thanks.
The reason I ask this question is because I’m at a bit of an impasse. I’ve recently realized how little I know about the various types of batteries and how to correctly care for them. In this post, I’m going to put out there what I know and then hopefully someone will come along and enrich my knowledge and give me some advice or give me some specifications on their setups with pictures being appreciated. I would also appreciate if someone could point me towards more resources in learning more about battery chemistry and more specifically what different chemistries are more suited to certain situations and how certain chemistries respond to certain charging programs. What I mean by that is I’d like to know more about the intention behind bulk, float, trickle, etc etc. and the other charging jargon. Not only what it means, but what each phase is designed to accomplish any why.
I’ve seen plenty of videos on youtube and have read some posts and blogs regarding all these topics, but I’ve struggled to find anything really conclusive. So if there are any books or manuals that you could suggest, I would appreciate it.
Anyway, on to the batteries:
The way I see it there’s only four or five chemistries that van dwellers would be interested in at least at this point.
FLA, SLA AGM, Li-Ion (Cobalt), LiFePo4, and for fun I’ll throw in a category for what I’ll call ‘experimental’ batteries.
Each of these chemistries has a different character, and after I’ve found a good match to achieve my needs, I’m going to dive into researching and learning how to properly care for the chemistry I’ve selected.
Flooded Lead Acid:
These guys seem to be very popular on cheaprvliving right now usually as two golf cart batteries in series to achieve 12v. The advantage of this chemistry is that it seems to be more forgiving than any of the other chemistries when it comes to over-discharging and incorrect charging methods. They are significantly cheaper than any of the other batteries I have listed, and they are readily available at common retail establishments, making them easy to replace. The disadvantage of FLA is the hydrogen gas that is created during charging, the necessity of maintenance, and the possibility of spillage. These batteries are also the heaviest compared to the usable amp hours provided.
Sealed Lead Acid Absorbent Glass Mat:
Another really popular battery in the van dwelling community at large. They have the advantage of being completely sealed and can be mounted in any orientation. They do not require any maintenance. They tend to be more expensive than their FLA counterparts however, and are less forgiving to abuse. Seeing as they do not release gas when charging, they are great for small enclosed environments where venting is either impossible or inconvenient.
Lithium Cobalt:
I haven’t seen anyone personally using a lithium cobalt bank for their house battery but these cells deserve a mention. They are used frequently in EV and electric bike applications, usually in the form of the 18650 cell. Tesla is currently using these types of batteries to power its cars. They are commonly found as laptop and flashlight batteries. These batteries have an excellent energy density, tolerate a much deeper depth of discharge, and have an astronomically longer cycle life than any lead acid battery. The disadvantage of these batteries is their nominal voltage of 3.6v, making it difficult to use them as a house battery for a 12v nominal application. They also are more prone to explosion than any of the other chemistries. One must also be willing to buy the cells individually and either solder or spot weld the desired sized battery together, seeing as readymade Lithium Cobalt house batteries are obnoxiously expensive.
Lithium Iron Phosphate
These batteries are most likely going to continue to replace lead acid batteries in many application, house batteries being one of them. They have an excellent nominal voltage of 3.2v, have an excellent cycle life, are very stable and safe, lightweight, sealed, and have an energy density close to lithium cobalt. The downside is that they are close to prohibitively expensive, may require a battery management system, and are not supported by most solar charge controllers without a programmable function. I’m not sure if it’s safe to link these guys to your alternator either.
Experimental batteries:
Zinc battery
The Oasis battery
I know nothing about these other than they make wild claims and I have no idea if they are credible.
So here’s what I’m trying to accomplish. I want to put an air conditioner in my van this summer. I have a 2000 Chevy astro, very well insulated with reflectix on walls, roof and floor, 4” of denim insulation in the walls and 2” on the floor and ceiling. Also nine cans of window sealer sprayed into every available crack. The space is very small, so a modern energy efficient air conditioner should only have to run sparingly to keep the space cold.
There was a really interesting van tour done on a guy I’ll called hurriedyear. He has a website with the same name where he has an extrapolation of his entire van laid out for our viewing pleasure. He has a 2006 Sprinter with a 960w system, and 780aH of SLA batteries he uses to power everything in his van, including an induction cooktop and an 8000 btu air conditioner. He can run his air conditioner non-stop for about five hours before running through his useable capacity of 390aH.
I have the advantage of having a smaller space, and I believe slightly better insulation. I will also be using a window unit instead of a portable unit, which is less efficient than a window unit. My air conditioner pulls 45aH @ 12v per hour while the compressor is running. My goal is to be able to leave the air conditioner on overnight, I would assume on the hottest night probably only running with the compressor on for a total of three hours.
My van had 520w of solar on the roof (the whole roof, lol), which I think will be sufficient even if the weather isn’t perfect. I have a 40A solar charge controller that is just an amp or two underweight for the peak efficiency of my panels, but I doubt I’ll hit peak efficiency anyway, so I don’t think it’ll ever see a 40A charge. The van is wired with 0 gauge pure copper, and I have a 1500w/3000w peak inverter to power my laptop, TV, and hopefully soon my air conditioner.
So that leaves one thing… batteries, and which to get.
At this point I think I should shoot for at least 300 useable amp hours of power. More is better. 500 is probably the upper limit; it’s definitely more than my panels would be capable of generating on even a perfect day. So that means I’m looking for a battery bank that has a capacity of 600-1000Ah at 12vdc.
That’s a big ol battery bank….
My van is very small. It’s too small to fit 8-10 golf cart batteries, and also ventilation = air loss = reduced efficiency, so FLA for me seems to be out of the picture.
SLA is a little more attractive, and probably the cheapest route at this point… however, these beasts( http://www.apexbattery.com/apex-apx12-260-12v-260ah-group-8d-agm-battery.html ) weight almost 150lb each and I would need 3 of them to hit my target of useable aH. Neither me nor my astro is interested in adding 450lb of lead and acid to our lives, and really I don’t think I have the space for those monsters. I would, however, go this direction if I had no other choice. I could make it work.
So that leaves the lithium batteries. They are very expensive, but they are excellent batteries. They are the most likely to be able to survive the abuse of running an air conditioner regularly. LiFePo4 is probably a better choice over making a pack out of 18650 cells, but I’m leaving the option on the table, just in case I really want to punish myself.
So I guess this is where my question actually beings (sorry!). Do you see anything I’m not seeing? Do you think I’m crazy? Do you know any nuances about LiFePo4 cells that I don’t know? Where to buy them? Where not to buy them? Do you live on the east coast and could I come look at your setup? I’m really just looking for more advice before I dive headlong into such an expensive and uncharted territory.
If you made it this far you have my deepest thanks.
