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Very general question about hooking something electrical to my FFR


Bilbo42
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Let me preface by saying that I know nothing about how to hook up a radio to my FFR. I do have an American radio that opertes from a number of power supplies, one of which is a DY-105 which requires 24 volts to operate AND I do have an FFR!!! With that said, I don't want to screw up the FFR by hooking something up that will blow something in the Ltwt!!!! But, it would be nice if I could run the radio that way instead of hand cranking!! The DY-105's purpose is to translate the many different voltages required for the GRC-9 to operate from a 24 volt source. Using the DY-105 does not require any batteries between it and the GRC-9. I know that a vehical with a NEGATIVE ground must be used. In American vehicles, the connection from the DY-105 (the power converter) can be made directly to the vehicle's batteries to get 24 volts to it and from it comes the voltages for the radio. I guess my question is, is it something that I don't need to do, or is it something, if done correctly would work fine. On my prior post, it was said that the FFR system was intended to charge and keep charging storage batteries that were then hooked up to the radio(s). Would it be more practicle for me to have two extra 12 volt car batteries wired correctly to get 24 volts hooked up to the FFR's system and those extra two batteries then hooked to the DY-105. That way the rover would just be charging the xtra batteries or is it more complicated than that? What I don't want to happen is for me to transmit and the power drain do something to the rover or have something else happen because I did something I was not supposed to. I hope this makes sense. I would appreciate your thoughts. Bil

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Bil, so I take it the only batteries you have giving 24v are the vehicle batteries? The FFR set up was intended to provide split charging to an independent set of 24v batteries for radios in the rear of the vehicle as well.

 

The system is -ve earth so you are ok there. With the system installed correctly if you talk too much & flattened the radio batteries it will have no effect on the vehicle batteries.

 

The Generator Panel No.9 (of which there were 5 versions the most common Mk 3 & Mk 4) has an isolating relay keeping the two sets of batteries separate. When sufficient voltage output is delivered from the alternator (Generator No.10) a large relay closes. This connects the alternator to charge both set of batteries & they are then joined in parallel for as long as there is adequate alternator output. If the revs fall too much & charging is inadequate, then the connection between the two sets of batteries is broken so that the low radio batteries don't cause a discharge from the vehicle batteries.

Edited by fv1609
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Thank you Mr. Elliott

With the isolating relay doing its job to keep the two sets of batteries separate, sounds like I need to get another set of batteries...hook them to the vehicle at the approriate place and then come off those batteries to the DY-105 power supply to run the radio. Now, the $64 question is...do I connect the two new batteries to the terminals on top of the generator box or is that not the place. Sadly, without the chance to get British radios for the vehicle, I have never explored the approriate process. Thanks for your help. I don't know if you remember me but you directed me to a friend of yours sometime back who really helped me research approriate 1974ish military vehicle marking. Best regards, Bil

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Bil, ah yes I remember you now. The radio batteries can go to the black & red terminals on the distribution panel. I don't know which Mk of set up you have. But if you look through this it shows the role of that isolating relay & how the various connections from the Generator Panel to the shunt box are distributed.

 

http://hmvf.co.uk/forumvb/showthread.php?20662-All-Charged-Up-Part-4

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