Upgraded to a 200Ah lithium setup in my Transit - a few things I wasn't expecting

Finally pulled the trigger on a proper lithium upgrade after years of flogging a pair of 110Ah AGMs that could never quite keep up with the induction hob. Went with a 200Ah 12V LiFePO4 from Fogstar (the Drift one) paired with a Victron SmartSolar 100/30 MPPT and a 200W panel on the roof. Total spend was around £700 all in, which I thought was reasonable.

First surprise was just how much usable capacity you actually get versus what the spec sheet says. With the AGMs I was nervous going below 50%, so I had maybe 110Ah to play with realistically. The Fogstar gives me a genuine 180-190Ah before I'm even thinking about it. That's a massive difference day-to-day, especially on longer stays without a hookup.

The thing I wasn't ready for though was how fast it charges back up. On a decent sunny day the MPPT is pushing 20-25A and the battery is sitting at 100% by mid-morning. I'm actually wondering now whether I even need the 200W panel or whether 150W would've done the job and saved me some cash and roof space.

Has anyone else found they've slightly over-specced their solar after switching to lithium? Or did you end up wishing you'd gone bigger? Keen to hear what setups people are running in similar-sized vans.

ForestWanderer | 847 posts | ⚡ Solar Enthusiast

@GazKelly75 Great shout on the Fogstar - solid kit for the money. One thing that catches people out after switching from AGMs is the flat discharge curve. You'll be running full voltage right until it suddenly drops off a cliff, so don't rely on your old voltage-based battery monitor anymore if you're still using one. Grab a proper coulomb-counting monitor like a Victron BMV if you haven't already - makes a massive difference knowing your actual state of charge rather than guessing from voltage readings.

Also curious what you're running for an inverter with that induction hob? That's typically where the real surprises come with lithium - you suddenly can actually use the thing properly without the voltage sagging horribly mid-cook! 😄

CamperTel | 1,204 posts | 🔧 Van Conversion Nerd

@GazKelly75 Congrats on the upgrade! One thing that catches people out with LiFePO4 in a Transit specifically - check your B2B charger settings if you're running one from the alternator. The flat discharge curve means your van's battery management can sometimes interpret the lithium as "fully charged" far too early and throttle back the charge current. Caught me out for weeks wondering why I was only pulling 60% capacity after a long drive. Worth logging the charge voltage over a journey if you've got a Victron shunt or similar. What are you using for alternator charging, out of interest?

OldSparky18 | 312 posts | 🔌 Electrician by trade

Worth checking your alternator charging setup properly @GazKelly75 — a lot of people forget that a lithium bank will happily pull massive current through the vehicle wiring if there's no B2B charger limiting things. Seen a few melted cables in Transits where folks just ran straight to the starter battery.

Stick a decent B2B in there (Victron Orion-Tr Smart is the obvious choice, or Sterling if budget's tighter) and you'll get properly controlled charging without hammering the alternator.

I've got something similar going in my shepherd's hut — different application obviously, but the principle of protecting your charging circuit is identical regardless of what's feeding the bank.

What's your current alternator-to-leisure setup looking like?