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

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Safiery Pty Ltd ABN: 87 624 588 807 30/75 Waterway Drive, Coomera QLD 4209 (07) 210 22 55 3 safiery.com sales@safiery.com Proprietary Information not to be published or copied without written approval from Safiery Pty Ltd. Q & A: Alternators, Conventional DC to DC’s, Scotty & Starter Batteries. Will a high powered (>30A) DC to DC kill an alternator? • Fixed power DC to DC: Yes, several do. However, some “may not” if they have a high voltage release; • Killa-wasp releases at high voltage so “No” it will not damage an alternator. • Variable Power DC to DC (Scotty): No, its not possible, Scotty turns off power at a slight drop in voltage below the set point. A) Fixed power DC to DC’s are either “on” or “off”. When “on” they extract fixed power from an alternator and using a transformer, produce an output voltage (generally higher) to charge a battery. If this power is more than the alternator can produce at idle then its probable they will damage the alternator. However, there is one proviso: a. the more advanced fixed power DC to DC have an elevated “turn off” voltage after start-up. This is designed to release the power extracted from the alternator if the voltage cannot be sustained. The Safiery Killa- wasp has this set quite high at 12.9V. If this voltage can’t be produced, the Killa-wasp turns off and waits to check for a high threshold voltage before turning back on. It does this in a proprietary way to protect the alternator first and maximize the power transfer second. b. In other brands, there may be low “turn off” voltages. When the input voltage setpoint is low, the current increases and the losses increase, and the DC to DC gets very hot – so does the alternator. These may shorten the life of the alternator. Other popular brands may decrease the power transfer to compensate. However they also decrease the power as the efficiency is low. Once the alternator and DC to DC are hot after 30 mins of running, its common to see a reduction up to 50% of the stated power with popular brands. (but not Killa-wasp) c. One other problem with fixed power units with a low cut off threshold is that they may not be Euro 6.2 compliant. There is no fixed power DC to DC that claims to be Euro 6.2 compliant that we are aware of. B) Scotty is a variable Power DC to DC. The extracted power is automatically adjusted if the produced voltage can’t be met. Scotty measures voltage to 3 decimal places every 1/400 of a second and reassesses power level based on a proprietary algorithm every 1-5 secs. This ensures not only that the alternator is not overloaded but more importantly, that the other loads required by the engine and the vehicle are given priority. The 1-5 second time interval is based on having a good vehicle starter battery which acts as a buffer. If the vehicle starter battery is in poor condition, small dips in voltage will be visible. This will not damage or affect the alternator. This have been proven in over 120 field live examples with nearly every model of 4WD and light truck. Safiery issues a “letter of comfort” to new vehicle van conversion companies that the warranty and power demand from the vehicle will not be compromised. Scotty is Euro 6.2 compliant.

“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 safiery.com sales@safiery.com 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.

“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 safiery.com sales@safiery.com Proprietary Information not to be published or copied without written approval from Safiery Pty Ltd. double 70mm2 for 140mm2 joint size for 0.3V drop. What Fuse Size should be used? A) The fuse is there purely to protect the cable from melting and/or catching fire. It will NOT protect the electronics from power spikes or adverse voltage levels (most people think the fuse protects everything). a. As a guide we divide the fuse current rating by 7 to give the maximum fuse size. So a Killa-wasp 80A with a 125A fuse needs a 125/7 = 18mm2 What if the alternator to battery fuse melts over time? A) A melted, deformed fuse indicates sustained power close to the fuse limit but generally not over the limit. Advice would be a bigger alternator or reduce the power load on the DC to DC (only possible with Scotty) to reduce the current. However, as Scotty is tuned to deliver maximum power at road speed, and it is during this time that the fused circuit will be at maximum current, it would reduce the benefits of Scotty fast charging and as a solar backup. MARINE APPLICATIONS What is the situation with outboard engines? A) Outboard engine alternators have a big alternator output power ratio. At idle the alternator power produced is very low. a. Fixed DC to DC has to be sized so it won’t bog down the outboard EFI at idle and kill the engine. Field results are that this is a very small number. Possibly with twin outboards 20-25A at idle. As a result this is the max size with most outboards. b. Variable DC to DC (Scotty): Scotty can deliver 25A at idle but 125A at full power. Scotty will not kill the engine at idle. What is the impact of cabling size from Alternator to DC to DC? A) It is common to pick up a roll of cable and read on the roll “maximum current”. This number is the current limit before the cable will melt and catch fire. It is totally irrelevant to power loss over distance. a. One reason small power DC to DC’s are promoted by 4WD shops is that they can install with smaller cables and without the need for lug and mega fuse fitting precision. For 50A over 5m, 50mm2 cables has a 2.3% voltage loss. That’s only 18W power loss. Install a 16mm2 cable (what is commonly done), the power loss is double at 36W but the charging voltage has dropped by 0.6V and the power transfer will most likely only get the battery to float voltage at a slower rate. b. Now step up to big power: 200A target. A 120mm2 cable will give 0.3V drop which is good for charging. Installing only a 50mm2 cable will give a 0.8V drop and the system will not charge properly. At Safiery our guide is at 3.5m, a single 70mm2 will give 0.3V drop. At 6m we recommend

“Travel the World, Without Consuming the Earth”

cable OR bigger. A 16mm2 cable would be too small for that fuse. With a 100A fuse, a 16mm2 cable would be fine (100/7 = 14.1). b. A Scotty with 250A fuse would need a minimum of 250/7 = 35.1 so we would use 50mm2 as a minimum. Using 70mm2 or double 70mm2 means the fuse is protecting these cables. c. On the 48V side of Scotty, a max current is 60A. This 48V cable need to be no bigger that 25mm2 for 3,000W capacity with a 125A megafuse. Bruce Loxton Coomera February 1 st 2022

Safiery Pty Ltd ABN: 87 624 588 807 30/75 Waterway Drive, Coomera QLD 4209 (07) 210 22 55 3 safiery.com sales@safiery.com Proprietary Information not to be published or copied without written approval from Safiery Pty Ltd.

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