This is a technical conversation with the support department at Goal Zero, manufacturers of a line of portable power-supply units. These can serve the functions of small generators or inverters, and be recharged from various types of sources. The company offers a "vertical market" of accessories to build out integrated systems with solar recharging and additional battery capacity.
In the process of evaluating their units and adapting for my own fast-charging setup, I came up with several questions. The email exchange started out positive but went a little downhill as I discovered certain limitations in the design and pressed for sufficient assurance that I could still do what I needed. The reader can be the judge of Goal Zero's quality of support when faced with an unusual level of analysis -- especially when it's obvious that numerous RVers and ham-radio operators who start using these units in vehicles are going to want to do exactly what I'm doing here.
The 40A mini-Powerpole connectors can be had from Amazon, in all kinds of multi-pack quantities, and they're usually genuine Anderson. Ultimately, my fast-charging rig worked out nicely, and didn't burn itself up. The unit's on-board charge controller pulls as much as it can from the Powerpole input without letting the source fall below 12.5 volts, up to a maximum of 360 watts which is right about 30 amps on average. [Input current actually gets pulse-modulated at around 200 Hz.]
Email thread follows.
### Msg 1 From: *Hobbit* To: email@example.com Subject: Yeti unit questions Date: Sat, 25 May 2019 06:27:36 -0500 I've just taken delivery of a pair of Yeti 1000 units, and have some technical questions. [I've also called in a few others prior to purchase, and was pleased to not only be able to easily reach a human on the phone but get good answers from them -- thank you very much for keeping it domestic in that regard]. I've found that the "12V" output isn't what a typical 12V jump-box would produce, but only seems to follow the internal lithium pack's voltage at 10.something. This is going to make some "12V" devices that actually expect more like the 13.8 - 14 running voltage from a car less happy, and possibly unable to function at all. Was there no engineering discussion of adding a small boost circuit here to bring that to a more normal expected range? Having purchased two units, I found that I can charge at double the wall-charger rate by plugging two chargers into the two available ports. 60W from the one alone really is a pretty piteous charge rate, but I realize that the OEM supplies you use for that are limited and run pretty warm on their own when supplying the unit. I will be investigating a more rapid-charge solution using the powerpole inputs, and if you have advice on a good place to source those mini-powerpole connectors, I'd love to know it. To that end, the manual is full of warnings about the voltage to present to the powerpole input, 14 to 22, but I was assured by one of your support people on the phone that the abovementioned typical output from a car's system will provide a workable source and the unit will begin charging from about 12.5 volts on up. That happens to be important to me, and I'm sure to many other users who aim to recharge from a high-current 12V hookup in some scenarios, and may have been a showstopper if that couldn't be done at all. The rep acknowledged that your manuals need quite a bit of re-writing to reflect the facts of the more recent unit designs, as there omissions and a few misstatements in what ships with the units and the PDFs presently on the website. Do you have details on the pack topology, e.g. what is the series/parallel layout? Does the battery controller do effective per-cell management, i.e. never letting any bank of cells wander out of safe voltage range? What are the various weird connectors, such as the unusual concentric 12V output barrel connector and its similar one on top under the cover? What about the two large connections and the micro-USB port under the small cover, what's all that for? Even if a new owner of these units may never intend to use those, the manual should describe exactly what they're for and what their input/output spec is. Thanks for any additional information you can provide! _H* ___________________________________ ### Msg 2 From: Goal Zero Support <firstname.lastname@example.org> To: *Hobbit* Subject: RE: Yeti unit questions Date: Thu, 30 May 2019 21:40:49 +0000 Hello, Thank you for contacting Goal Zero. 12V is an umbrella term that does cover a range of voltages, as you have seen. If you have a device that will not work on the lower voltages of lithium batteries, we do have a voltage regulator that will step up the output voltage to a steady 13.8V (https://www.goalzero.com/shop/yeti-accessories/yeti-lithium-12v-regulated-cable/). We also have a new Yeti 25A fast charger that will charge your power stations at a rate of about 300W (https://www.goalzero.com/shop/yeti-accessories/yeti-fast-charge-25-amp-power-supply/). These are both out of stock right now, but we expect to have more of them in the next 2 weeks. We are working on our user guides, to more accurately reflect the recent changes to the units. If your vehicle is running, you should have a high enough voltage from your battery to charge the Yeti power stations from the 12V car charger. We do not have any public specs on the battery topography, but the battery management system does have effective per-cell management. The barrel connectors in the 12V output are 6mm connections, and they work with our Light-a-Life 350 lights (https://www.goalzero.com/shop/yeti-accessories/light-a-life-350-led-light/) and some other adapter cables that we have. The expansion port up inside the lid, with the micro-USB data cable is for our MPPT charge controller (https://www.goalzero.com/shop/yeti-accessories/yeti-lithium-mppt-solar-charging-optimization-module/) or our Yeti Link (https://www.goalzero.com/shop/yeti-accessories/yeti-link-expansion-module/). Regards, Becky Davis Solutions Center Representative EMAIL RDavis@GoalZero.com OFFICE 888.794.6250 #GetOutStayOut #OfficeAnywhere GoalZero.com | Facebook | Instagram | YouTube | Twitter GOAL ZERO IS AN NRG COMPANY ___________________________________ ### Msg 3 From: *Hobbit* To: email@example.com Subject: Re:Yeti unit questions Date: Mon, 10 Jun 2019 16:54:49 -0500 Cc: firstname.lastname@example.org Thanks for answering my previous questions [in all their multi-part glory], that really helped, and will hopefully guide you in the production of updated documentation that's perhaps more "geek-friendly". I suspect a lot of geeks are going to be hollering for these products. I have another question, which your phone folks suggested I ask "engsupport" about. I finally received some of the Powerpole connectors, and am playing with building a "12V" fast-charge car harness. The input will typically be the nice solid 13.8 - 14 volts from a Prius downconverter, and preliminary tests indicate that it will work fine and deliver the full 350W limit of charging or whatever it is. To better understanding what various limitations on that setup might be, I'm playing with some boundary conditions. I have a variable supply, up to about 15V with a *deliberately* imposed internal resistance, i.e. a "weak supply" that droops when high current is asked of it. Between 12.3 V or so input and the 12.5 "real charging" threshold, the unit draws up to about an amp of current, but the blue light doesn't go on and no input wattage is indicated. However, the box will continue to draw that current if the too-low voltage is sustained. That current has to be going *somewhere*, so the immediate questions is this: into the battery, or just overhead in the charge control circuit? If into the battery but the charge control is inactive, it is potentially unmetered charge which could *eventually* bring the cell voltages too high. It's an edge case and would take a long time, but if someone left a "bad" supply or solar rig hooked up for many days... So how does the pack protect itself from "under the radar" charging situations? You could of course also create this situation from the direct hookup under the little cover; is there a master pack cutoff someplace in case something goes really wacko? I like how that charge circuit soft-starts very slowly and ramps up, clearly watching for the "sag" to either hold at the right level or give up after someone's blown the fuse to their cig-lighter type accessory cord... I'm using a direct hookup, of course, for which I've long since standardized on the larger 75A Andersons since I had a lot of them around. Thanks _H* ___________________________________ ### Msg 4 From: *Hobbit* To: email@example.com Subject: More on 12V charging Date: Wed, 19 Jun 2019 14:33:51 -0500 In the process of working up a fast-charge harness for the car ... per my last msg ... It seems to work nicely, coming right up to the 360 watt limit, but boyhowdy, those little 40A powerpoles get warm! After scoping the current waveform, I realize that with the input modulation they're handling over 50A in bursts. Kind of leaves me wondering if you should have used a larger size connector... I'm using 10ga wiring and have nice solid crimp/solder connections to the lugs, and as far as I know they're the genuine Anderson 40A part. _H* ___________________________________ ### Msg 5 From: Goal Zero Support <firstname.lastname@example.org> To: *Hobbit* Subject: RE: More on 12V charging Date: Mon, 24 Jun 2019 20:17:03 +0000 Hello, The APP input port can handle up to 30A, which is probably why they are getting so hot. You may want to step down the input a bit. Regards, Becky Davis Solutions Center Representative EMAIL RDavis@GoalZero.com OFFICE 888.794.6250 #GetOutStayOut #OfficeAnywhere GoalZero.com | Facebook | Instagram | YouTube | Twitter GOAL ZERO IS AN NRG COMPANY ___________________________________ ### Msg 6 From: *Hobbit* To: Goal Zero Support <email@example.com> Subject: Re: More on 12V charging Date: Tue, 25 Jun 2019 07:18:39 -0500 Well yes, the Yeti *is* drawing that average 30A by itself that the APP connector is supposed to handle, but this is *your* design running things right on the edge of what they can take. At current levels like that any small defect in wiring, connector mating, etc is going to heat parts up a lot *more* than where they're already going to be, just due to physical limits and the amount of metal in the path. It's not easy to "step down the input" from a fixed voltage car charging system that's only doing its normal job, so that seems rather infeasible. How, would you suggest? Drop in series resistance, which would reduce efficiency and increase a fire hazard?? If anything, the *Yeti* should offer a way to back off the input modulation width, and allow the user to regulate down the pack's own maximum input rate. I don't suppose there's already some hidden way to do that, a "magic chicken-dance" one could do with the three display buttons to get into a limit-setting mode? Please run this one by engineering, they need to pay attention. I can't imagine that your own product line accessories that use the same connector aren't experiencing the same thing under normal operation. Anderson connectors are great for applications like this, but they do have their limits. _H* ___________________________________ ### Msg 7 From: Goal Zero Support <firstname.lastname@example.org> To: *Hobbit* Subject: RE: More on 12V charging Date: Tue, 25 Jun 2019 14:02:21 +0000 Hello, We do not recommend connecting to your alternator in this way in the first place, and it is one reason that we do not have cables that connect from your alternator into the built-in input ports of the Yeti power stations. The panels and power supply cables we do have are within safe limits for these ports. We have recently released a product that allows you to safely charg e from the alternator (https://www.goalzero.com/shop/kits/yeti-link-car-charging-kit/), but it does not use these input ports. Regards, Becky Davis Solutions Center Representative EMAIL RDavis@GoalZero.com OFFICE 888.794.6250 #GetOutStayOut #OfficeAnywhere GoalZero.com | Facebook | Instagram | YouTube | Twitter GOAL ZERO IS AN NRG COMPANY ___________________________________ ### Msg 8 From: *Hobbit* To: Goal Zero Support <email@example.com> Subject: Re: More on 12V charging Date: Tue, 25 Jun 2019 16:27:21 -0500 Well, one of your support people told me on the phone that the unit would begin taking charge at 12.5V [as noted in my previous messages] and would be fine, and that the confusing warnings about vehicle systems in the older manuals were bogus. It sounds like 1> y'all need to get your stories straight, and 2> give customers a much clearer picture of *what happens* when you connect the Anderson inputs to a car 12V/alternator [or any other] system. It's clearly in spec of what the unit will accept, and there shouldn't be anything special about the fact that the supply happens to be a vehicle. How many units have come back with melted Anderson connectors by now? I gather that the Link in car mode will do about the same thing that the base unit does from observing the supply voltage at the Andersons, but uses the direct high-current battery connections instead and the data port to regulate and cut off. Another $475 to solve what's arguably *your* engineering problem? Maybe if I was running from depletion-mode batteries, sure, a booster would be needed. But my scenario is one that a *lot* of buyers are going to want to set up for themselves. _H*=== end of email thread ===
[*Note: they never responded past this point.]