CTEK help

Hi everone,
I have just used a CTEK M200 to charge the dual batteries (lead acid) in my camper trailer since I came home from a trip.

The charger has been putting in 14.9Amps (as read off the Victron battery monitor) all night and my battery monitor says the batteries state of charge is now 100% but the charger has continued to input the high current so I switched it off.

The batteries are standard Marine lead acid batteries and I could hear the liquid in them bubbling.

Should I have let the CTEK continue to charge and hoped it would switch to the next stage?

Does this extended time charging at high amperage sound right (does my CTEK know best) or does it sound like something is wrong??

The battery monitor will be looking at either the current voltage (where 12.8V or so means 100% charge and anything > means the same thing) or it's done some math on the amps used and amps replaced and discovered that the batteries SHOULD now be full, if no losses have occurred and the measurements were all accurate.

The C-Tek charger on the other hand has a program that looks at charge rate and surface voltage (which is a reaction to the charge rate in both volts and amps). It's usually very, very good at what it's doing.

It does sound like it's in "recover" mode though. I recently used my C-Tek to recover a bulldozer battery. Took it all night and half a day and then needed a second run - it was a bloody big battery! It worked - and the C-Tek dutifully turned its recovery mode off when complete.

I can't help wonder if the two batteries are mismatched in some way though. A fully charged battery will present a higher surface voltage and then pump power to the lesser charged battery. A charger attached to the pair will see the surface voltage and be somewhat confused by it, plus the continued acceptance of extra current. Eventually it will have both batteries charged properly, but I wonder about the cost in terms of damage to the battery with higher charge - overcharging batteries can damage them too.

I'd charge them individually to be safe and ensure both are brought to 'full' again before reconnecting them. Are they both the same battery, with the same capacity, purchased around the same time? If not, the mismatch between the two batteries will cause eventual problems (including self-discharging at an alarming rate).

Thanks for your help Tony. I think you are right about the battery monitor. It remembers how many amps have been used and replaced so I'm guessing that's how it calculates that the batteries are full.

The two batteries connected together are not mismatched. They are 2 identical batteries bought and installed at the same time.

I have since found the user manual for the ctek charger and it states that stage 2 of charging (bulk) can take a maximum of 20hrs (as timed by the charger itself). Stage 1 and stage 3 also take about 4 hours each so I have just plugged it back in and will let it do its thing. Eventually it should commence the float stage and I'm sure the batteries will be charged by then!

Good to hear.

Are the batteries used separately, or maintained in their parallel state at all times?

They are maintained in parallel at all times.