Would this suffice?
https://www.ebay.co.uk/itm/ABSAAR-Heavy-Duty-Battery-Starter-Charger-12-Volt-20-Amp-with-180-Amp-Boost/192447683179?hash=item2ccec69a6b:g:1HQAAOSwicpaeF5q
I wouldn't bother with this tbh. Its just an old glorified workshop starter battery charger. All starter battery chargers aren't designed to charge a starter battery to its optimum. As long as it puts enough charge into the battery to start the vehicle, that's all thats needed. The average repair workshop won't care if they just charge a battery to 50 or 60% charged. All they are interested in is getting the car started, getting paid and sending the driver on his way.
I would certainly check with the company you bought it from and ask them for their charger recommendations. Perhaps tell them what charger you are currently using.
The peak bulk charge is higher than a vans alternator pushes old (pre smart alternators) and much higher than the 13.9 volts my Numax charger delivers. They do say that the battery is 100% charged at 12.8 volts so it could be that a standard intelligent charger will work - but I would want to make sure. If your charger isn't completing the job of fully charging the battery, the battery won't last as long.
If you take 50 amps out of your battery a day, then thats going to take the best part of 8 or 9 hours to recharge it with a 10 amp charger. If you only recharge every second night, then you my find your charger hasn't fully recharged your battery the next morning.
