Victron ip65 8-24 battery charger for LAB and Lion packs

[robint]

Ive spent a few years trying to fathom the mysteries of Lead Acid Batteries - its real black art stuff and covered webwise in a mountain of BS. I am referring to deep cycle batteries used in golf carts and mobility scooters - so called maintenance free Gel and AGM types. I wont go further on this as it would take hours and hundreds of pages - google as you wish but discount 99% as premium BS.
As for Chargers, these are important to maintain the battery wrt to charge capacity, charge time, life cycle.
Alarming fact - contrary to what you might believe from the outrageous hype, Deep cycle means no less than 50% SOC - State of charge wrt to factory Ah capacity  100Ah gives 50Ah useful capacity.  That capacity can drop 30% after say 300 cycles ie 35Ah.  It can also drop 25% with temp say bringing you down to 25Ah.  Draw heavy current at say 50A and capacity drops a further 50%.  So under adverse conditions, when you might expect a 20 mile range you might only get 5 miles -  thats how drastically bad LABs are for motive power.

Well thats some background

There is a plethora of so called smart chargers on the market - dont get me started on the so called desulfating restoring myth - waste of money.
A simple charge block will have 3 stages - bulk ca 5A, absorption ca 0.5A and float ca 0.2A (I would put a 4th stage of STORE as something that trips in once a week to abs charge back up to Vend - good thing as modern batteries have a very low discharge and can go a month without a top up).

This is all fine provided you take care and never leave a battery discharged >24hrs >50%SoC and always fully recharge - remember a 120Ah set will cost ca£400 and should last 4 years 500 cycles
There are many graphs available (try Sonnenschein)

So I was encouraged by an alleged expert Victron in Solar energy storage system ( their special batteries cost 4x and weigh 2x those deep cycle I discussed above)

Their charger cost 4x a conventional 3 stage block but has a mobile Android app that you can view battery charging and historical data - the answer to a maidens prayer - or so I thought

Ive set up a comprehensive test bench with accurate DMMs with data logging to monitor charging profile over a 24hr period - after each trip.  You need to measure Volts to 4.5 places eg 25.67V.  that last digit has a significant difference.  At the end of a trip your battery needs to relax for at least an hour to get true Vend from which by historical experience you might deduce realistic SoC

I want  to know if any other board members have similar experiences before I go into a rant about the potentially fraudulent Victron.

BTW Lions batteries used in EVs dont suffer anything like this kind of grief

BTW must point out that the Solar power off grid guys are on a different planet and have far superior stationary LABs with a much more robust internal construction and a life expectancy of up to 10 years - but at 4x price, 2x size and weight and dont like being shaken around. Forklift batteries are usually wet flooded type so the electrolye pH can be measured and the SoC accurately determined.

[deadlylover]

I use a Victron IP67 12V 17A and I've been happy with it as a "basic" charger. I chose this mainly because you're able to adjust the voltage to whatever the battery specifies.

I wouldn't rely too much on the historic charge data for SoC use, it's just a 2 wire system after all. You should be using some kind of battery monitor/shunt for that.

What kind of trouble are you having with it? Looking forward to the data.