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[Keith]

I fried my 2.5kW inverter and I have not found a reasonably priced replacement. Inverters that can handle the full Zero battery voltage are rare.

[talon]

Keith, sorry for the bump but server grade uninterruptible power supplies make very economical, reliable inverters. They almost always are scalable battery-wise, <$400 because the batteries have died, and made to work in hot humid climates (no ac when the power is out!)

I am doing the exact same project with a standalone 2012 ZF9 battery. My discovery seems to be that ALL the precharge circuitry is either done by the MBB/CCU/or the motor controller. The contactors' coil wires are directly wired to a large connector on the rear of the battery (and seemingly not to the BMS at all), so it's very manual and I may need a precharge circuit. I'm curious if your modular FX batteries are this way or if the BMS gained that circuitry when they went modular/post 2012.

[Keith]

Good luck! Be careful about the inverter DC input voltage, scalable might be batteries in parallel not series. Server grade is good stuff but transistor breakdown voltage is not forgiving regardless. Precharge is essential whenever a battery and capacitor are connected. It can be done with a resistor, I used 4.7k 5W if memory serves. The 16 FX BMS just checks the voltages across the contactor, won't close it unless precharged. 

[talon]

What I meant by scalable is that there is literally a parallel connection for "unlimited" additional batteries at the rear of the unit. Due to the strange voltage of my lithium pack (18S--65.7Vnom) I went with a 72V (5B or 30S) lead acid UPS that has plenty of headroom on the max voltage specs. It has an adjustable low-voltage cutoff and a max range of at least 80Vdc. I could have gone with a rare 60V (4B or 24S) lead-acid UPS and it likely would have been fine being well outside it's upper voltage range, but I wanted to be within spec of the UPS.

I'm assuming precharge is only to protect the contactor and nothing else? As much as I hate it, I'm thinking of using a board with 3 switches and a couple sacrificial relays. I even have a spare contactor from a larger, dead Zero pack I could use. I'm thinking the process goes like this:  feed load with resistive line (1Amp fused) to charge caps, next additionally connect low-current (30A fused) carrying line with no added resistance, then close contactor. Then disconnect resistive and low-current lines and increase load. Do you believe the contactors are designed to break full load current if the battery is being overcharged or overdischarged with your FX?

[DonTom]

Wire round resistors?  What frequency AC?  There will be less current with AC because of the inductance of wire-wound resistors. .  To do a fair comparison, you need to have an AC ammeter in series.


-Don-  Reno, NV

[Keith]

Your relay scheme will probably work fine. The contactors can handle a lot of inrush current, but without precharge the initial current is theoretically infinite, limited in reality by the wire, inductance and capacitor imperfection. The Zero will close the contactor with a pretty large voltage difference, including between two modular packs which then equalize instantly.  So precharge doesn't need to be perfect, but it needs to be.

[talon]

All voltages listed are DC. I'm not doing anything with the pure sine wave output of the UPS inverter. Trying to figure out the DC side of things from the battery pack's cells through the contactor to the UPS DC input.
Would something like this work for basic precharge function (closing PRE, then QUIQ, then CONT, and then disconnecting QUIQ and PRE)? Forgive me, I have no experience drawing circuit diagrams and am aware that this has backfeeding issues that would drain the caps, feed the relays, and has garbage component values.

Part of me is considering leaving the resistive wire attached full time, except when I need to completely manually disconnect the load to save the <30W or so that can be drawn at UPS idle if its computer wakes up. It's so weird that the BMS on this 2012 ZF9 pack seemingly has no control of overdischarge and overcharging! That's a lot of faith by design in the (albeit well-made) Delta Quiq chargers! Even the Quiq charge and onboard charge ports are simply fused (30A) and go straight to the positive bus bar (no contactor)! I suppose the BMS could "beg" the MBB/CCU/Sevcon to open the contactor in an emergency or send a disable signal to the Quiq, but having that functionality external to the battery makes no sense to me. Dealing with a contactor raw is nice in some ways but makes me a little uneasy that I'M responsible for all the protections, and I currently have no way to verify balance/imbalance except the light signal.

I might add an extra high rupture capacity fuse or two to this everywhere I make a major connection.

[Keith]

Chargers don't rely on the contactor. They supply a current that is reduced when the battery voltage approaches full charge, becoming zero when it does. Contactor can stay closed without worry during charging (with a smart charger like the DeltaQ).

If the resistor is fairly large, the UPS won't be able to run because its current draw will drop the voltage below its minimum. So leaving it connected may be ok.

Too many problems with your diagram to even begin, but I get the idea.

[talon]

I just meant in terms of tolerance to a faulty charger (say, if it somehow was set to overcharge or had an internal short draining the battery below cutoff)--not to break charging regularly. I believe all later zeros can't charge when the contactor is open so this just seems like a very strange design quirk for this year. Honestly it makes the MBB really part of the BMS system rather than keeping all protection (over temp/voltage/current, balance, low voltage, isolation) "in house" to the battery. But that is looking at these components with a perspective as if they were designed to work independently off-bike (not as part of the bike's system), which AFAIK isn't true until the 2015 powertrains were developed to be sold separately.

Yes, the diagram is embarrassing to me and was done in crazy haste as I've been travelling a lot and haven't had the time. I did read through yours and Farfle's posts on precharge circuits and theory on endless-sphere to see what I could grasp and if I was missing any important considerations. Posted here as a sanity check. Thank you for your work and for sharing your time and research with the community.

[ieism]

This is a neat idea, but i'm not skilled or smart enought to pull that off.

I have a 2kw battery in my 4x4 with solar and a few bits and bobs running more or less full time. When I go camping, I sometimes run out of battery, but there is not much more room to put leisure batteries and they are expensive.

The Zero FXS comes on trips, that's 7kw of power just sitting there and I wish I could use that. Could I get a 12v out from the bike easily and run my 12v car stuff from the bike in case I ever need it. The batteries on the car are wires with Anderson connectors, my thought was to just wire a plug form the bikes 12v directly to the 12v system on the car but I'm assuming I'd have to disconnect my solar to prevent it putting in power somehow.

Is there a better safe and simple way. I can solder and understand simple 12v stuff, but I'm not that good with the rest of the thongs mentioned above.

[Richard230]

This is a neat idea, but i'm not skilled or smart enought to pull that off.

I have a 2kw battery in my 4x4 with solar and a few bits and bobs running more or less full time. When I go camping, I sometimes run out of battery, but there is not much more room to put leisure batteries and they are expensive.

The Zero FXS comes on trips, that's 7kw of power just sitting there and I wish I could use that. Could I get a 12v out from the bike easily and run my 12v car stuff from the bike in case I ever need it. The batteries on the car are wires with Anderson connectors, my thought was to just wire a plug form the bikes 12v directly to the 12v system on the car but I'm assuming I'd have to disconnect my solar to prevent it putting in power somehow.

Is there a better safe and simple way. I can solder and understand simple 12v stuff, but I'm not that good with the rest of the thongs mentioned above.

I have been hearing news reports lately regarding the new Ford Lightning electric pickup truck that claims that its battery will be able to power your entire home automatically, should your power go out. While a great idea, I assume that a certain amount of electrical infrastructure would be needed to be installed in your home to allow that to happen.   

[Crissa]

I have been hearing news reports lately regarding the new Ford Lightning electric pickup truck that claims that its battery will be able to power your entire home automatically, should your power go out. While a great idea, I assume that a certain amount of electrical infrastructure would be needed to be installed in your home to allow that to happen.   

Yeah, you'll need a transfer switch and the 'Ford Charge Station Pro' price currently unreleased.

-Crissa

[mryan]

I fried my 2.5kW inverter and I have not found a reasonably priced replacement. Inverters that can handle the full Zero battery voltage are rare.

DC to DC converter down to 12v and then the options are plentiful I can't say you'll find a reasonably priced one however. There's this one, or elcon makes a 1kw version, maybe there's an ev that has a high kw version to salvage from.

https://www.electricmotorsport.com/isolated-600w-dc-dc-converters-48v-60-72v-96v-108-144v-to-12v-50a-select-model.html

[talon]

A note on precharge, solar DC breakers seem to work pretty well. I understand breakers aren't made to be used as switches but it's a quick and dirty solution if you only rarely need to power down a load. Obviously this is ignoring many relevant safety considerations and should be used at your own risk. I don't know if the ampacity of a lithium battery could damage the input capacitors on the load so precharge may still be necessary.

Midnite's MNEDC and MNEPV breakers seem pretty nice, rated around 150VDC and any regular current rating you would need. At ~$20 this seems much less expensive than fuses and the highly reliable contactors. With the above considerations, if it was in a "fixed" location (not a vehicle) and installed in a proper enclosure I fail to see any reason personally to go another route.