Hello! I’ve been searching around the forum and the internet in general and can’t seem to find a solid answer for my question. Me and my girlfriend are working on building out an old conversion van and we’re currently trying to chose our best option for batteries. We’d obviously love to get lithium batteries (weight, safety, 100% DOD if needed, etc.) but we’re also trying to save some money where we can (we’re both college students). In my search, I found these batteries
Miady 12V 16Ah Deep Cycle LiFePO4 Battery on Amazon (sorry can’t post links yet!)
They’re quite small but they are lithium and I was thinking about getting 5 or 6 of them and wiring in parallel to get a larger capacity out of them. If this worked, I’d have nearly 100ah of usable battery capacity for around the same price as a VMAX 125ah AGM which weighs much more and only has a 50% DOD.
Is this a feasible plan? Are there downsides? I’m not an electrician/ my electricity knowledge is pretty small so I’m not sure if there’s a loss in efficiency with so many connections or anything like that.
With LiFePO4 (LFP) batteries, for long life every cell in every battery needs to be individually charged/managed with a battery management system (BMS). Some of the larger batteries have a BMS built-in, but most do not and require a BMS type charger. LFP batteries have different needs than lead-acid in terms of charging voltages etc. A standard charger might work, but probably won’t contribute to the longevity that LFP batteries are capable of. It might be a challenge to properly charge LFP batteries using alternator power or a solar system. It may be that LFP batteries are best suited for an environment where they are fully charged, depleted, and then fully charged again; not an environment where they may get sporadic charging here and there.
Thanks for the reply! On Amazon, it says that the batteries do have a built in BMS. I was planning on having a solar setup with an MPPT charge controller and also a hook up to the alternator.
So you’re saying that having those batteries in parallel could lead to imbalances in charging them which could damage them/ their longevity?
Might be okay if each battery has a BMS built in. I don’t think they’ll get an imbalance if they all have a BMS. It might work just fine, but I can’t give a 100% assurance that it will. The technology is still young, and in terms of sporadic charging through a starting battery/alternator isolator or solar panels (clouds do occur), I really don’t know. Might be fine, might not be.
We use two 92 amp hour AGM’s that in total were ~$400 which is a lot, but far cheaper than lithiums. they’ve been good over a year. Granted we only run our maxx fan, fridge and lights. We probably drive an hour a day as we travel extensively and are always on the go hiking, climbing, whatever. That seems to be enough to keep ours charged just fine though probably never 100% unless we do a long drive. We only have an isolator as our charger.
We have thought about switching to lithium for our hose batteries, but I do not know how that would mix, having an agm for the starter and the lithium for the house? Technically they are wired together when the isolator is on, depending on the isolator type.
I would start with regular batteries and make sure you have your setup correct before you throw money at expensive batteries. Don’t want to kill them because something was configured wrong. You can always replace them after they die with lithium if you want to.
I wouldn’t abandon the idea of Lithium yet, but it may require more research on your part to get a better understanding of what’s involved. You could start with looking up the specs for your MPPT controller to see what voltage it puts out at the maximum charging rate, and compare that to the voltage range that the BMS in your batteries require. If the controller voltage falls within that range you might be good to go. Today’s solar charge controllers (including your MPPT controller) are basically smart chargers designed for either sealed (AGM or gel), or flooded lead acid batteries, and are programmed to charge to certain voltage points throughout the charge cycle, and when charging is complete they go to a float/maintenance mode to not overcharge. If the BMS can take advantage of the controller’s charging voltage curve then it might work as long as its in the part of the charging curve with the full power of the panels. For alternator charging you want to be sure that alternator output falls within the range of what the BMS needs.
Another way that might work if controller voltage isn’t compatible with the BMS, is use a switching type regulator (which should be more efficient than an old fashioned linear regulator). It would have to be big enough to handle the amperage of the solar panels, and supply clean DC to the BMS at the proper voltage. Panel output would have to be less than the switching regulator maximum input in terms of both voltage and amperage.
I go to a junkyard and pick up nearly new $300+ RV deep cycle batteries for ~$20 and they last 5-7 years. I don’t have solar, just a $20 solenoid, and a $20 set of jumper cables with the clamps swapped out for ring terminals for the heavy wiring. One 100ah battery gives me all the power I need, and if I drive 15-30 minutes every 3 days or so it keeps it fully charged.
So I stuck my house battery in a boat box behind my drivers seat, and have 4 acc. plugs on each side of the boat box for a total of 8, and my entire electrical system is done. If I need power way in the back, I have a 20’ extension cord.
I have an el cheapo generator & a battery charger for backup, but rarely use them. My starter battery is also deep cycle, and each battery will last about a week before my low battery cut-offs kick it off, but that still leaves me plenty of starting power even after it cuts off.
So my entire electrical system, including the generator and battery charger is probably under $200 total, and in the last 11 years I’ve replaced my house battery and my starting battery once each. My generator & battery charger mainly get used to charge other people’s systems who have falsely put their faith in solar.
I’ve tried both the expensive routes with solar etc; and the cheap routes, and the cheap routes seem to be sooo much better and more reliable too.
Cheers!
"Keep it cheap, and use the extra money for your adventures." ~ Van_Dweller
I have been looking at battery power for a while. Those batteries are so Small!! Perfect my tiny travel trailer. I have a small little box that I can power up with a small solar panel. This little thing can actually power my small cooluli fridge in eco mode, charge my phone and lights. I only use the cooluli for my milk, butter and creamer. Other than that I don’t need a lot of power. I think I have used the lights once? But In the future my trips are going to be longer. My youngest is almost 18. After shes 18, my husband and I will be going out longer. So I was looking at a bit bigger fridge and more solar and battery power. I will be keeping an eye on this thread for more ideas. Thank You!
