2017.06.19 FwdMan2.8.17.docx 2-11
2.2.3 System Powering
General remarks
The entire FWD/HWD Test System, i.e. the Loading Unit Hydraulics as well as the
Electronics, is powered exclusively by 12VDC, normally supplied from an alternator in the
towing vehicle.
Optionally, a “stand-alone”, trailer mounted, gasoline engine driven Power Generator Unit is
available for vehicle independent powering, see 17.1.9, “Power Unit”.
The FWD/HWD trailer electrical system is connected to the 12V system in the towing vehicle
(or to the optional, trailer mounted Power Unit) by a “Trailer Power Cable”.
The entire Test System (FWD/HWD hydraulics and Electronics) typically requires a total
supply of up to 40 Amps (HWD: 60Amps) average during extensive use, like e.g., three full-
height drops plus one lowering/raising of the drop weight subassembly every two minutes.
ADDITIONAL Alternator (RECOMMENDED Solution)
As mentioned above, the FWD/HWD towing vehicle should preferably be equipped with an
ADDITIONAL alternator of 12V, 60 Amp. (HWD: 90 Amp.) minimum output rating. Please
take this into account when selecting the towing vehicle and make sure that the engine
compartment has sufficient space for this. Perhaps ask your vehicle supplier to deliver the
vehicle fitted with such an extra alternator.
IF you use this recommended, additional alternator solution, then you can skip the following
paragraph and continue from “Electronics Buffer Battery” below.
Using/Replacing the EXISTING Vehicle Alternator (ALTERNATIVE solution)
If for some reason the only possible solution is to use the existing alternator, then this should
have an output current rating of at least 90 Amps (HWD: 120 Amps) and if a Diode Unit is
used for battery separation, it should preferably be ADJUSTABLE (to 15.0 Volts output
instead of the standard 14.3 Volts - see below).
Many vehicles are factory fitted with a 65 Amp. alternator which MAY be sufficient (FWD
only, not for the HWD), if it can be adjusted and if the FWD is not used very extensively and
the need for 12V supply for other devices (like warning flasher lights, etc.) is rather limited,
but we strongly recommend to get the existing vehicle alternator upgraded/replaced to achieve
the recommended 90 Amp. (HWD: 120 Amp.) min. current output rating.
Note on alternator rating
Please note that the buffer batteries i.e., the 12V 40-60 Ah Electronics Buffer Battery in the
towing vehicle and the Loading Unit Buffer Battery(-ies), are NOT intended for providing
CONTINUOUS supply, but ONLY for peak current BUFFER supply OR to provide UUa couple
of hoursUU of back-up supply in case of alternator failure or disconnection, e.g., due to blown
fuse(s), so THEREFORE the alternator MUST be able to supply AT LEAST the AVERAGE
current consumption of up to some 40 A (HWD: 60 A), otherwise the batteries will be
discharged after some time.
A larger buffer battery capacity will ONLY be useful, if OVERNIGHT charging is applied,
using a HEAVY, mains operated battery charger with at least a 40 Amp charging current
output rating. In that case the buffer batteries MAY be able to supply what the alternator
“misses” during a day’s work.
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