Lithium for an RV

[heynow9991]

HI

Im looking for suggestions for a lithium battery pack for an rv trailer that will be used in film and tv production. The company I work for has several of these trailers and we use 6v golf carts batteries in packs of 4 or 8 and as you can imagine they add a lot of weight to the already heavy trailer. The batteries are 6 volt s and they have 190 amp/hr at the 5hr rate and they are 66 lbs.

What I am looking for is a battery pack with a lighter chemistry that can deliver approximately as much as 8 of the 6v batteries we are using now, in a 24 v pack. It has to be safe with no chance of fire. Cost is an issue, I am looking for the best bang for my buck. I am good with wiring so I have no problem putting together the battery pack. For an inverter we use Victron inverter/chargers, which can charge lithium batteries. There would also be a separate solar charging system.

I am looking for suggestions on where to buy the batteries and hardware, not a completed pack, that would be too expensive

Im in Canada so any North American supplier would be OK

Im not sure on how to do the math on the size of our battery packs so if someone could help me do the math to figure out the size of a pack with 4s x 6v 190 Amp/hr x 2p that would be a great help

Thanks

Peter

 

[Grizzl-E]

You won't beat lead for cost. But you could look into recovered (from wrecks) Nissan Leaf cells. 6 or 7 in series depending on the allowable input to your inverter.

 

[Jon NCal]

24V 380Ah system = 9.12Kwh

 

[Alan B]

Used Leaf battery modules, 8V 60AH (2S2P cells packaged in a module)

190AH in 2P is 380AH.

3 modules in series is 24V.

3S6P is 18 modules giving 24V (or a little less as they discharge) at 360AH

Lead should never be drawn more than 50% down, Lithium can go much lower, so if your lead pack was only being used 50% you could downsize the lithium pack to 3S or 4S.

The lithium can handle MUCH higher current with little sag, if that's important.

You want to find local suppliers for Leaf batteries, or buy a pack and take it apart.

 

[Punx0r]

I suspect something new and available off-the-shelf may be required for this application. Large format cells like CALBs might be good. They might not be the best performing Li-ion but they should be better than lead (and get used in plenty of electric car conversions).

 

[heynow9991]

Yes I am definitely looking for large format cells. I was hoping to get some ideas of good companies to deal with, thanks

 

[Alan B]

This may not be a good forum for that, more likely an electric car forum. Very few folks on here deal with those.

 

[wesnewell]

No such thing as a safe battery. Not even a lead battery is safe. You'll probably want high ah calb batteries. Just google calb batteries.

 

[nutnspecial]

I don't know why I'd ever choose anything other than lead for my Rv? Shearly for weight is negligable since a powerbank is such a small percentile of gvr.

The idea of large format lithium is very interesting tho, and I'm glad to know about it. It actually appears (from link) that the cells are not priced outrageously (more than 2x) compared to leadacid.

 

[Alan B]

If you want to run an inverter or other high current load the peak current capacity of lead is poor. So you have to either put a lot more battery capacity onboard, or trash them fast with high current.

If you want to carry more capacity than the RV was designed for you quickly run out of space and the weight gets very high with lead. Lithium helps a lot here.

RV batteries are in a poor place for weight, at least on trailers.

Lead batteries are very energy inefficient. A great fraction of your energy is lost during charge which is important for solar or generator charging. Lithium is much more efficient.

Lead batteries have very poor discharge depth capacity. You have to discharge less than 50% to get good battery life.

Lead batteries need to be maintained. Water needs to be checked and replaced. Gets very tiresome.

Lead batteries discharge significantly while sitting. Over the winter they will discharge and possibly be damaged without maintenance. Lithium will float at storage charge with minimal discharge during storage.

 

[nutnspecial]

If you want to run an inverter or other high current load the peak current capacity of lead is poor. So you have to either put a lot more battery capacity onboard, or trash them fast with high current.
If you want to carry more capacity than the RV was designed for you quickly run out of space and the weight gets very high with lead. Lithium helps a lot here.

I see those points. Lead must be oversized compared to lithium to provide similar higher currents and maintain lifespan. Lead just isn't for as high of continuous discharges for similar capacities it seems, and of course weighs more per capacity. There does seem to be a certain robustness to it though.

RV batteries are in a poor place for weight, at least on trailers.

N/a for me and most rv customizations imo. You put the access and weight where you want it, and condition the space if necessary. But still a valid point in theory provided 100ah of lithum is maybe 50% that of lead? Considerable also is vs in lifetime, manufacture/recycle, and consumer cost too, but that's obvious I guess.

Lead batteries are very energy inefficient. A great fraction of your energy is lost during charge which is important for solar or generator charging. Lithium is much more efficient.

I wasn't aware of this. Are there percentages to compare?

Lead batteries have very poor discharge depth capacity. You have to discharge less than 50% to get good battery life.

Depending on current I assume? This means 400ah of lead might get 250ah(?) usable @ 100a(?) discharge vs 400ah lithium gets 95%(?) with 100a discharge? Sag and charge range must have some effect for discharge current and time vs capacity between the two chemistries and various capacities vs discharge, and lithium can provide more current in a shorter time at a lower weight.

Lead batteries discharge significantly while sitting. Over the winter they will discharge and possibly be damaged without maintenance. Lithium will float at storage charge with minimal discharge during storage.

This is very true. Best life is attained when kept full charge, so system should be oversized for 'decent' current draws and should be trickle charged over time to much greater extent than lithium.

 

[Alan B]

A significant fraction of energy in the lead acid charge cycle is lost:

https://en.wikipedia.org/wiki/Peukert%27s_law

Here's some data on lead vs lithium:

https://www.victronenergy.com/blog/2015/03/30/batteries-lithium-ion-vs-agm/

Some folks have been quoting that used lithium from electric cars is cheaper than new lead. I haven't compared it but lead cost has gone up a lot in recent years, and I think the quality of lead batteries has gone down. It is hard to get a fix on the price of used lithium, but with the increase in electric cars on the road it is becoming more available.

On my trailer the weight and volume of batteries is a significant issue, and lead batteries require ventilation and significant strength to support compared to lithium. With the trend toward smaller RVs the size and weight of lithium is an advantage. Carrying hundreds of pounds of lead is also not free, it adds up over time. A large inverter requires very heavy lead batteries which aren't very practical on the tongue of my trailer.

 

[nutnspecial]

Atm I'm covered with lead for portable energy storage, and double price would have me highly considering value of lithium even if it needed expanded or replaced right now.

I am so young to be so slow to change. Seems we go the way of the world and lithium it is! I'm still not sold it's any better than lead for our environment, combined with curtailed 'energy' usage, but the chemistry does not seem anything other than superior for power, weight, and upkeep.

I hoped maybe someday to live offgrid (independent of utilities, and hopefully more green for energy, life suppliments, and waste management), and it would be smart to fully consider all aspects of the energy storage possibilities. Thanks for the info, it does very much look like lead will be phased out for that purpose.