pic: Cart Wiring Plans

[eshteyn]

well looking at your design it could be greatly simplified. everything runs through the inverter except the car battery charger. My method only requires 2 AC relays.

[BlackShadowFox]

The only problem with that is a inverter can't make 100% of the DC energy to AC their is about a 20% loss as compared to a DC to DC converter where near to none is lost.

[eshteyn]

Originally Posted by BlackShadowFox

The only problem with that is a inverter can't make 100% of the DC energy to AC their is about a 20% loss as compared to a DC to DC converter where near to none is lost.

very true but honestly unless your planning on leaving it unplugged for 2 days straight and expect everything to be charged then theres really no need to be so concerned about it, thats just my experience. Your idea is great, but there has to be a way to simplify it. Simplicity is usually the best thing especially when in competition you cant devote any time to fix the system.

[robostangs548]

Looks pretty sweet, i hope to see it in Atlanta

[Al Skierkiewicz]

Not to rain on anyone's parade but... Game rules require that robot batteries be charged with the KOP supplied chargers only. As I have pointed out in other posts, UL Safety Advisors will be taking a long look at this type of design as it mixes high voltage AC and low voltage DC as well as having no safety ground while moving.

[Billfred]

Originally Posted by Al Skierkiewicz

Not to rain on anyone's parade but... Game rules require that robot batteries be charged with the KOP supplied chargers only. As I have pointed out in other posts, UL Safety Advisors will be taking a long look at this type of design as it mixes high voltage AC and low voltage DC as well as having no safety ground while moving.

Not quite, Al...

<R54> The ES17-12 can only be charged between matches by a 6-ampere rated automatic battery
charger. When recharging the Kit Of Parts batteries, either the charger provided by FIRST
or an automatic charger with an equivalent charging current rating may be used.

Edit: Read Richard's post, too.

[Richard Wallace]

Billfred cited the rule correctly. However, I would still heed Al's suggestions above. He has many a grey hair and he earned them all the old-fashioned way.

The UL Safety Advisors are, well, UL people. Their professional responsibility is looking out for safety hazards, and they literally set the standards for that. I would expect them to look for UL labels on any electrical device that is connected to the AC power system, and for any such device to be properly connected to an earth terminal (aka "ground") when it is in use.

[Al Skierkiewicz]

Bill,
You are correct. What I was pointing to is the DC powered trickle chargers shown on the diagram.

[BlackShadowFox]

Thanks Billfred for the Rule <R54> and sorry about the last time i debated about the the rules.

I'm kinda lost in what you guys are saying here. I see that you people are saying it would be safer if their was a AC (earth) ground, but i am lost on why the DC tinkle chargers would no be o.k. please explain why charging DC with DC at different amperages using a current limiter is wrong.

Am i right to assume that if i hooked the main battery to the DC to AC converter then to the AC to DC chargers that would result in a lot of noise that would have to be filtered and would be highly inefficient and may cause weird result in the robot batteries/ chargers.

Please Explain

[Richard Wallace]

Originally Posted by BlackShadowFox

... Please Explain

I'll take a whack at it.

First, the trickle chargers must be UL rated if they are active while the cart is connected to AC power. And they should be appropriately fused to protect the wiring to the cart battery. Since Chargers 2 and 3 effectively become trickle chargers when their batteries are full, separate trickle chargers aren't really needed anyway. Chargers 2 and 3 should be connected to AC power when it is available, and switched over the inverter output when AC power is not available.

Second, the connection shown as a red line across the top center of the diagram indicates direct connection of the inverter output to an AC power cord. This is generally not a good idea, and in any case it provides no benefit to your cart that I can see. Powering the inverter from the cart battery and then powering Charger 1 from the inverter to charge the cart battery -- well, that arrangement has power chasing its own tail! The inverter should provide power to AC devices when AC power connection is not available, and should not be connected to Charger 1.

[BlackShadowFox]

Oh this is my fault i should have done this sooner but i forgot. the ac input mean input only that line wouldn't provide power back to system. The inverter

I'm using a Vanner inverter where their is a AC relay inside of it that choses whether AC from the wall is used or the create its own. Sorry for the miss direction about that but i thought that people would take input as input only.

[Richard Wallace]

Originally Posted by BlackShadowFox

... I'm using a Vanner inverter where their is a AC relay inside of it that choses whether AC from the wall is used or the create its own. Sorry for the miss direction about that but i thought that people would take input as input only.

This is getting interesting! Maybe the inverter you are using addresses the safety concerns that have been raised here. Are you using this one? I haven't checked out all of its specs yet (slow internet this morning) but it seems to handle change-over to shore power automatically.

Also, what else can you tell us about the trickle chargers?

[Al Skierkiewicz]

Specifically at issue here is the chance for a wiring error to cause high voltage to be present on exposed metal on your cart. I know you are going to tell me that everything is done correctly and it has been checked over by a knowledgeable mentor but we still have the potential for personal injury of not only your team but those around you in the pit and in the cue. As Richard has pointed out, I have a few grey hairs (and many that have dropped out by themselves) from being witness to a variety of damages from miswiring. These events are mostly non-robot related. One of the things I and other mentors strive for is a safe event where everyone can have a great time. I would feel very bad if I was able to head off a disaster but failed to cry a warning. So for the record, the use of an inverter and the obvious use of high voltage on a cart requires some extra precaution and safety checking that even I am not able to give (either via CD or in person). I caution you (and other teams that may be thinking along the same lines), that event staff may not be open to the use of this cart where the public is at risk. I would rather you have an interesting cart with no power on board than a cart which event staff and other teams find objectionable and needs to be removed from the venue.

On another note...although there is no rule against charging batteries right up until you take the field, I think many people could and would take it as giving you an advantage over those teams that don't have that capability. I wouldn't commit to this design without an official FIRST OK. Sorry.

[BlackShadowFox]

For Richard:

This is the right company but however that is not the same inverter. I'm using a donated inverter that was a scrap part from an ambulance. As for the model number and specs i will have to wait till Monday to give you further information.

For Al Skierkiewicz:

if we were at competition i would give you a lot of safety credits for your constant strive for safety. i understand what you are saying with my heart but with a obsession like mine it would be hard to break. i desire that this cart be more robot than cart if you know what i mean, not trying to go against you here. the only promise i could give you would be that i will ensure that my cart wouldn't endanger others and if i see fit i would cancel the project and remove it myself. All i ask is for you to believe in my planning skills and to try to trust in me.

As for the charging till the point of the game i will ask first but in thinking about it. it shouldn't have that much of an effect but still it is better safe than sorry.

[Al Skierkiewicz]

Fluffy,
Don't let your obsession shadow your thought process. I don't want to shut you down on this design but it is a dangerous undertaking that involves a great many other people. I would suggest you follow a few additions to your plan.

1. You need to add appropriate fusing of the main battery, DC and AC wiring and a simple quick disconnect to remove all power from the cart.
2. You must adequately insulate (and I mean prevent any contact by using enclosures not just tape and heatshrink) all electrical connections. This includes the main battery.
3. Promise me that before applying power at all events, you seek out the UL safety advisors and event staff. They both must examine your cart and pass on it's design and use before you can connect the main battery.
4. You need to provide adequate control (key switch or lockout) such that only you or your mentor may apply power to the cart. You need to know that a new team member hasn't comprimised your design by connecting something they shouldn't have or made repairs that you do not know about.

Let us know how you progress and post a picture.