BATTERY CHARGING KRC4 STD

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But how is the battery charged if the X305 connector only sends current?

why do you think that? if CCU X305 only sends current to charge batteries... what is the point in having batteries at all? according to you those batteries are there just for one thing - to consume energy..!?

if so, why not put small heater instead of batteries? this could run maintenance free forever...

the thing is that charge goes both ways.... when batteries are low, CCU charges batteries. actually this is pretty much default state ....

but when main power is off, batteries are powering part of CCU and KPC and RDC and part of KPP and perhaps some other things too.

during this period, KPC is supposed to close any open files, stop any services etc. it should also wait for robot to stop moving and save that position (to RDC). once everything is done (plus maybe some optional delay) KPC, RDC and most of the things are powered off... but not all.

and this is why X305 need to be disconnected if you do not want batteries to drain while your shop is closed (you are on a vacation etc.). otherwise batteries will be dead when you come back.

but CCU or more specifically PMB is also checking if batteries are worth charging. if they are too low (or connected wrong) charging is disabled.

periodically PMB also tests the batteries... basically is draws current from batteries and records voltage changes during the test. if during that test current or voltage are inadequate, batteries may be deemed dead. normally this results in message being displayed to warn user to replace them but ... sometimes ... it fails to do that. and if batteries go low without notification, next time there is a power outage or someone thinks it is a good idea to power off controller while robot is moving will be presented with a surprise on next powerup - since last recorded position in RDC does not match current robot position, affected axes (and their dependents) will be unmastered.

žicu ne zanima kojim putem teče struja ...

you connected amp meter to CCU X305?

that means you literally created short circuit on X305...

that could explain a thing or two....

using multimeter requires training and knowledge of both circuit and multimer function, characteristics and the effects on the circuit caused by connecting measuring device...

batteries are DC devices, so direction of current can be determined from sign of the measured value.

ampmeter (or multimeter configured to measure current) is a low impedance device. essentially it is a short circuit. this is why ampmeter is always wired in series with the load. connecting ampmeter directly (without load) to devices that are sources of power is wrong and could lead to destruction. and in most cases does because there need to be something to limit the current to some reasonable value. if the ampmeter the only thing that limits the current, something will be smoked... you need to test your multimeter too. maybe the fuse is blown.

btw.

there are also ways to measure current without interrupting circuit, for example using clamp meter. but not all clamp meters are created equal and therefore cannot be used in all circuits. they could use different technology to sense current. the most common type of clamp meters use current transformer. this works only on AC circuits. Rogowsky coil is another sensing device but really it is only a form of a current transformer.

and then, there are some clamp meters that use HALL effect. those can be used for both AC and DC circuits...