I'm absolutely not expert on this topic. However, I seem to have spent a lifetime at sea/offshore finding workarounds for various tech "improvements "
Chargers.
Modern electronic Chargers like the Ctek etc are very capable, and v useful, however they do have some issues/limitations...imho...
I have several newish chargers, including a very whizzy Victron 15A IP565 (£100 ish, even has blue tooth connx to my phone display, data logger etc...), an poor man's Ctek 5A Aldi ripoff £15ish, and an AA branded mini 2A version for small batteries £15ish.
They all share what to me is a very similar issue. They seem to use charging algorithms that cannot cope with a " dead flat" battery. When initially connected they test for battery residual voltages, and without seeing this they register an error and will not move forward into proper charge mode. (Perhaps this is somewhat akin to "waking" a sleeping LifePO4 battery? My fancy Victron has a mode for this too!).
The Victron manual explains this algorithm, and the ctek too (desulphation/soft start) to a lesser degree.
This can fool you/me into thinking the battery, or perhaps the charger, is "faulty". It definitely fooled me the first time encountered.
My solution is to use my old school 11A heavy copper wound transformer charger (nil electronics, so don't leave it too long, especially on a smallish battery) to get the battery up to 11/12v or so. The fancy electronic Chargers will, then "see" the battery and go through the appropriate modes, including desulphation if necessary.
Of course, I don't claim to have invented this method, I've worked alongside very skilled heavy-power electricians who have also used another "known good" 12 V battery to temporarily trick the electronics under similar circumstances, as many industrial chargers are too big to use, indeed too big to move!
Works for me. AT YOUR OWN RISK! Let me know how/if it goes for you.
I've only this week had to use this technique to enable recharge of the battery in my old Ford Focus estate "crapmobile" (mobile shed/toolbox) that had inadvertently been left standing for 9 days with consumers plugged into the always-live cigarette lighter
socket. The Aldi-CTek showed a fault error code initially.
1. Copper 11A charger for 2hrs. A lower rate would be preferable, but none available....
2. Victron on reconditioning mode.
Car now fine.
Solar charge controller.
Perhaps similar? I don't know!
My MPPT solar controller, and seperate battery "contents monitor " (both now Renogy, original 10 yo Victron couldn't do my new Lithium batteries) both display the same V as my multimeter.
I agree with GW re multi meter readings. Borrow another, or even buy one, they are cheap as chips nowadays, while reasonably accurate, and perfectly safe to use on LV. I keep my second one on the boat.
O duffer. Has the controller perhaps "fixed itself" now the battery is charged?
Many MPPT controllers, even Victron quality ones, don't have digital displays.
