Hairy Animal
Member
I note there are plenty of useful and interesting suggestions in other threads such as "Current-measurement-How-would-you-do-this" but not much of what's referred to there is particularly appropriate to what I'd like to do.
Basically, I've got two banks of 6 x 12V 110Ah batteries i.e. two 72V 110Ah batteries, each with a suitable current shunt connected to a DMM measuring volts, current, time and other useful things, but the two DMMs are fixed and not easily visible (in a cupboard).
What I'd like to do is to monitor the current from these batteries remotely using an 08M2 sending the data via an NKM2401 to a roving display. Each battery (fused at 355A) is connected to the motor controller via a hefty contactor and either or both can be connected as required. It's unlikely that the current, even when the batteries are combined, will exceed 500A. I don't really need to measure it more accurately than about +/-25A i.e. about 5%, though ideally it would be more accurate at lower currents.
I note from the aforementioned thread, interesting devices such as the LEM part HTFS-800-P available from Farnell but it's a bit OTT for what I need, with 1% accuracy, and is relatively expensive. Because I'm working with 72V d.c. (can be 90V when on charge) I really don't want any direct connection so a Hall Effect type device would be ideal but the ACS758 (now obsolete anyway) despite being Hall Effect, still requires a break in the current path. I dare say I could get a cheap clamp-on current meter and maybe modify it, but would be interested to know if anyone's done anything like this or has any suggestions as to cheap devices which might help please?
Basically, I've got two banks of 6 x 12V 110Ah batteries i.e. two 72V 110Ah batteries, each with a suitable current shunt connected to a DMM measuring volts, current, time and other useful things, but the two DMMs are fixed and not easily visible (in a cupboard).
What I'd like to do is to monitor the current from these batteries remotely using an 08M2 sending the data via an NKM2401 to a roving display. Each battery (fused at 355A) is connected to the motor controller via a hefty contactor and either or both can be connected as required. It's unlikely that the current, even when the batteries are combined, will exceed 500A. I don't really need to measure it more accurately than about +/-25A i.e. about 5%, though ideally it would be more accurate at lower currents.
I note from the aforementioned thread, interesting devices such as the LEM part HTFS-800-P available from Farnell but it's a bit OTT for what I need, with 1% accuracy, and is relatively expensive. Because I'm working with 72V d.c. (can be 90V when on charge) I really don't want any direct connection so a Hall Effect type device would be ideal but the ACS758 (now obsolete anyway) despite being Hall Effect, still requires a break in the current path. I dare say I could get a cheap clamp-on current meter and maybe modify it, but would be interested to know if anyone's done anything like this or has any suggestions as to cheap devices which might help please?