Mastervolt Chargemaster 12/70 that ignores programming?

[Eric Jan]

hi all,

I have a fun one with a Mastervolt Chargemaster 12/70-3 that I would like to serve a bunch of Lifepo4 batteries, but it seems its ignoring its programming.

The 2 issues I seem to have:

1. Ignores Bulk / Absorp setting and keeps going at full blast
2. After AC being re-activated it doesn't initiate charging

challenge 1 - ignoring bulk / absorp max
When putting AC on it starts charging and having set bulk at 14.00v and absorp at 13.95v for 20 min you would expect it would stop at 14.00v and go for absorp at 13.95 for 20 minutes.

However it seems it ignores this and just keeps going and at 14.20v I turned the charger off manually.

HOWEVER after doing a factory reset, and setting all the settings again via the 3 buttons on the machine, it seems to work well again for a couple times.

THEN when not being hooked to AC for say 24 hours-ish, challenge 2 shows up.

challenge 2 - After AC being re-activated it doesn't initiate charging
After not being hooked up to AC for say 24-36 hours and when being hooked up again it stays at float. Voltage being 13.30ish and charging 0 and not reactivating charging. Also waited for say 10-30 minutes, but no change.

A factory reset and resetting it all to settings below it seems to go back to challenge 1


Settings (and yes they are very very very mild to lifepo4, but I'm a wuss with this):
Bulk - 14.00v
Max timer - 530 min (just shy of 9 hours)
Min timer - 0 min
Absorp - 13.95v
max timer - 20 min
min timer - 0 min
return amp - 0%
ret amp - 0
float volt - 0.0v
cont. volt - 0.0
return bulk* - 12.50v
return bulk delay - 4 min
warnings (they are not tripped so not important i think)

*return bulk seems to work when being hooked to AC, hit its point to go to float and when voltage reaches 12.50 it would kick in again. Tried this once, basically by using heavy AC load via inverter. I dont think (might be wrong) this is the issue as in other cases it started charging when well above 12.50v as well when AC being turned on again.

I'm doing all settings via the 3 buttons on the chargemaster which only takes like 10 minutes.

Also no heat sensor connected at this stage.

What am I doing wrong? please feel free to shoot.

(ps. i dont want to invest to much money in this as I'm planning to put a victron multiplus in somewhere in the next 12 months anyways)