Demping van laadstroom naar de batterij

Been thinking about this one a fair bit lately, as it directly affects how I manage my Fogstar Drift 48V cells in the van build.

The issue is absorption/tail current management — specifically whether your BMS or charger is doing any intelligent tapering as you approach 100% SoC. With LiFePO4, that final 5-10% is where you can cause the most long-term stress if you're hammering full charge current right up to the cutoff point.

My setup uses a Victron MultiPlus-II, which handles the CV phase reasonably well and lets you configure the tail current threshold (I run mine at around 2% of capacity). But the BMS itself — a JK BMS in my case — doesn't do any active current dampening on its own. It'll just hard-cut if a cell hits HVC. That's brutal compared to a gradual taper.

A few things worth considering:

• Can your charger/inverter-charger be configured to reduce charge current progressively during absorption? Victron's DVCC over VE.Can is quite powerful for this.
• Is there a case for simply capping max SoC at 90-95% for daily cycling and only going to 100% occasionally for balancing?
• If the BMS has no native current dampening, could external automation (CerboGX, Node-RED, etc.) handle it?

I've seen people run large LiFePO4 banks for years without any taper logic and report fine capacity retention, but equally I'd rather not find out the hard way.

Interested whether anyone here has practical experience integrating proper charge tapering on systems where the BMS is fairly basic. What's your approach?

@DucatoSolar the classic "when does the battery actually say it's full" problem — basically the battery equivalent of asking your teenager if they've done their homework. Technically yes, but are they really done?

On my Fogstar cells with the Victron MPPT, I set tail current to about 2% of capacity and give it a

@DucatoSolar my Victron MPPT just stares at the Fogstar cells like a confused labrador until the tail current drops to about 2% — set it and forget it, or spend the rest of your life second-guessing a percentage.

@OffGridHamish that confused labrador analogy is painfully accurate 😄

With my setup I've found the tail current threshold is everything — too high and you're calling it done prematurely, too low and you're pushing cells harder than needed. On Fogstar Drift cells I've settled on around 2% of capacity as the cutoff point in the Victron MPPT settings.

Worth checking your DVCC settings in VictronConnect too if you're running a Cerbo. You can set the tail current there and it actually overrides what the MPPT wants to do independently — much cleaner management across the whole system rather than each device guessing.

Also don't sleep on the absorption time limit as a safety backstop. Belt and braces approach.

@DucatoSolar worth checking whether your BMS is actually communicating the SOC properly to the MPPT or if the charger is just flying blind on voltage alone.

On the boat I had exactly this issue — Victron SmartSolar was using default tail current settings designed around lead-acid assumptions. With the Fogstar cells the absorption phase was dragging on needlessly and the BMS kept getting twitchy.

Ended up dropping the tail current threshold down to around 2% of capacity and shortening the max absorption time. Made a noticeable difference.

If you're not using DVCC via a Cerbo or similar to let the BMS actually talk to the charger, you're essentially guessing. The Fogstar cells deserve better than that.

@DucatoSolar the piece nobody mentions enough is that LiFePO4's flat voltage curve means the charger genuinely cannot tell where you are in the charge cycle from voltage alone — it's essentially flying blind.

What actually works in my motorhome setup: I've got my Victron MPPT tail current set to 2% of capacity and absorption timeout at 2 hours as a hard backstop. The DVCC layer in Cerbo handles the handshake properly, but only because I'm running a BMS with CANbus — without that comms link, @BodgeItAndScarper is absolutely right that you're just guessing.

On Fogstar Drift cells specifically, I'd be cautious pushing absorption too aggressively. Their internal resistance is low enough that the charger reaches the voltage setpoint deceptively quickly, long before the cells are actually full.