Can CTEK CT5 CT79FR Bring Back Dead Battery At 5.6 Volts?  

Question:

Expert Reply:

We've all been there, Josh, you're not alone! The CTEK CHARGER # CT79FR can sometimes recover low-voltage batteries, but it depends on how far gone the battery is. If its still above around 7V and not heavily sulfated, there’s a good chance it’ll begin the charge cycle. If its dipped lower than that like in your case at 5.6V, the charger might not detect it right away, and you may need to give the battery a quick bump from a jump pack or another charger first. You can use jumper cables to a car battery for a few seconds and then the charger will work and you can disconnect the cables right away.

Darryl in Flagstaff had a marine battery sitting at 8V and got another full season out of it using this model. Want help checking yours before plugging it in? Let us know what type of battery you're using — we can walk you through a quick multimeter test to see if it’s salvageable. One thing you can do is turn off the lights and make sure there are no loads or draws on the battery, and see if the voltage comes back up after sitting a few hours. This sometimes helps to allow the charger to engage, if it doesn't automatically. If charger still doesn't give it a full charge after a charge cycle, the battery is likely bad and needs replaced unfortunately :(.

expert reply by: Andrew N

0

Alex

7/8/2025

Josh, I was in the same boat with my camper battery stuck at about 6V. I used a cheap jump starter for 30 seconds just to wake it up, then let the CT5 take over. Brought it back slowly over two days and it's back to good health.

Josh

7/8/2025

@Alex Awesome thanks Alex. I'll try that this weekend when I get to my property. Hopefully I can dodge a bullet and not have to replace the pricey battery this year...