Microsoft Word - Q and A on Alternators DC to DC and Scotty…

“Travel the World, Without Consuming the Earth”

Safiery Pty Ltd ABN: 87 624 588 807 30/75 Waterway Drive, Coomera QLD 4209 (07) 210 22 55 3 Proprietary Information not to be published or copied without written approval from Safiery Pty Ltd. What is the best sizing of Alternator and DC to DC? A) Variable Power DC to DC with Scotty: Choose an alternator size that will be max charging power plus vehicle loads at road speed. Increasing the alternator size will be a worthy long term investment. Power fluctuations at idle is not important as Scotty is variable power at idle. B) Fixed DC to DC: Here idle is important. Choose an alternator that is at least 2 times the size of the fixed power DC to DC. Will the starter battery be properly charged with a DC to DC? A) Fixed power DC to DC small size (<30A) generally do as the alternator at road speed will produce more power than the DC to DC draws. The result is an elevated voltage that keeps the starter battery properly charged. (note this may not occur at idle as noted above, but most vehicles are not at idle for long). B) Fixed power DC to DC of high power (80A) like Killa-wasp have two scenarios: a. If installed in just the 4WD, then after the target lithium battery reaches float voltage, the Killa-wasp turns off and stays off for a reasonable period. During this “off time”, the alternator will increase voltage either during regen mode in a Euro6.2 engine or at higher RPM in others. This will properly charge the starter battery to an absorb voltage level. b. If installed as the DC power for a towed caravan: then the maximum power of the alternator must be more than the Killa-wasp + vehicle loads. Originally, we tested the Killa-wasp at 100A but found this did not meet the above criteria for an LC200 or LC79 with a factory alternator. Our testing showed 80A to be the sweet spot for these vehicles (AND the Ford Ranger). Other vehicles with an alternator over 150A output is fine even with a Euro 6.2 engine. When the caravan is disconnected and the vehicle driven, the Killa Wasp is off and the vehicle alternator charges the starter battery perfectly. C) Variable Power DC to DC (Scotty) will continue to extract maximum power (providing alternator can deliver it (see first question) until the target batteries are at float voltage. a. When extracting the maximum set power, Safiery leave room during commissioning to witness a high alternator voltage at higher revs than idle. This ensures a high voltage is produces after power extracted and keeps the starter battery properly charged. b. Regardless of (a) when the target batteries are at float voltage, Scotty reduces power, it may even turn off. During this period, the alternator voltage also increases to properly charge the starter battery. c. Safiery measure the starter battery and if customers have online monitoring and support, monitor that the starter battery achieves an elevated voltage as part of the post commissioning period. We are not aware of any situation where the starter battery has been compromised because of Scotty.

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