Lithium Phosphate batteries

[Gents]

Hi Funsters, I’m thinking of going mad & putting a whole new set up in my PVC.
I know it’s not going to be cheap but I like the idea of not being tied to hook up pitches.
Looking at Solar panels, inverter, B2B charger & 2 x 145W Lithium phosphate batteries. “Ouch, I hear you cry”. Me too,
would just like any feedback on what I am suggesting. I am looking for the extra easy life, the big 70 in Feb.

 

[Kannon Fodda]

A number of issues to be considered from this thread, going back to the OPs first questions, rather than worrying about some of the techy stuff.

First battery capacity & how much do you need:
How long are you spending off grid between EHU and any lengthy drive to get a re-charge?
What are you doing to chew through power whilst away?

Solar:
Great, during sunny weather during the warmer months. When it's cloudy, rains, it's winter, or you've parked in a nice shady spot, you could have smothered your roof with panels, but you aren't then going to refill those batteries.

B2B:
A must on the average modern van, especially with Lithium that can take the higher recharge. But even with a 60A B2B (and the average PVC probably couldn't support much more from the standard alternator), working super efficiently, an hour's drive isn't going to give you more than say 55Ah back into that battery. So this comes back to how long you are off grid, what you want to do.

Inverter:
What size. What have you got that must run off mains power and how much juice will it need? Make sure you don't overload the batteries, of any type, they can only support certain rates of discharge for short and extended periods - the C rate. Bigger inverters may need 2 or more batteries simply to support the discharge rate, not how much you are using. Run for too long and you've not got enough power for your general habitation. As far as possible have stuff that is 12v so you don't need to upscale to mains, then down again to your appliance, with two inefficiency processes. Many TVs and such like can run 12V. If recharging devices, perhaps do that whilst driving, you at least won't be discharging the battery even if the B2B can't quite keep up.

Lithium:
Despite the techy stuff above on how much to charge / store, once you get over the hiccup of cost, for a PVC the advantage has to be space as one 120Ah Lithium is going to do the work of at least 2 conventional batteries, when you can take the lithium down to 20% or less, yet lead-acid will not like regular discharge below 50%., and you've saved weight as the lithium might even be lighter than one of the lead acids.

I had my pathetic 75Ah lead acid swapped for a 120Ah lithium over summer, together with a 60A B2B and the 100W solar upgraded with a MPPT controller rather than the manufacturer's one. I've since fitted a battery monitor, and a 375W inverter. The original charger has remained, that being decidedly unsmart and just want's to do a flat 13.8V charge, whatever demand is or is not made of it. The BMS will stop an overcharge, so if I'm on EHU it won't matter how long it took to get a recharge. It's more if I'm off grid what might happen. 100W solar will never recharge, but on a decent day it might earn me an extra day or two of sitting in a field without moving. I do tend to use sites, CS rather than wildcamp. Autumn I found that an evening's TV (I'll watch a lot being on my own), and other stuff, I would take the 75Ah down to it's 50%, so 30Ah would be my working allowance per day, as I could be a bit more frugal, without being miserly. Was last out just before lockdown, and used about 60% of the 120Ah Lithium over 2 days, including a bit of the inverter to power a beefy 150W laptop charger (too big to run off 12V). The hour's drive back home didn't refill the lithium. Today, sitting on my drive, the solar is still trying to get the charge back up to full, bearing in mind with a Battery Master the hab battery can trickle the van's engine battery so the alarm can't make it all go flat.