Battery charger

Battery charger output will vary with the state of battery charge. The 110 VDC rating if read off the name plate on the charger is just that a rating for the battery potential.

With what did you test the voltage output?

This sounds like a charger for a nominal 96V lead acid battery array.

The float charging voltage should be close to 110VDC.

119VDC is a little high even for boost or equalisation charging.

70VDC is useless.

Sometimes is when exactly?

There might be something wrong with the regulation circuit. Probably gets real hot at 70VDC. It is DC right? Did you check for ripple?

Could even be a fault in the battery array itself. Have a better look and apply some science. Note the conditions when the errant voltages are observed.

Shailesh, You need to check the exact charging voltage required, as stated. We use (for two very different applications with very different battery technologies) either 53 or 55 lead acid cells of nominally 2V each, and both departments refer to their battery banks as 110V banks despite carging in the 117-118V range! But more to your point of the charger, i agree that it sounds like a fault on the regulating/ feedback circuit. How does the voltage change - is it related to the load being drawn, did you measure that? Take note that, depending on the charger type, you usually would have a lower voltage when the battery was really flat, to ensure the charging current stays low enough (for constant voltage / current limited chargers anyway). But even then 70V is too low, as you would normally lock-out your battery at around 90V (if i recall correctly- i haven't worked with this for a few years now!). There could also be a problem with loose connections, either in the battery bank itself, or in the connections to the charger or the load, etc.

I think we all assume charger to be connected to a battery- but is this true for all your readings?

Is your battery always on-charge, discharge only in emergency?

Or is it discharged and then re-charged as normal use?

Is there any normal [standing] load, additional to battery charge?

If this were a starter battery, you could get the battery voltage range you wrote, but time as low as 70V would usually be very short - this might be "overshoot" of an un-damped meter.