Field Charging

[Chaosfruitbat]

Apologies if this is the wrong part of the forum for this!

I'm off to do some racing in a few months, and I will need to charge lipos at the trackside (there is no power on site). What do you experienced people recommend for a power source? Leisure battery, or is there a better alternative?

Ta

[Howards]

Leisure batteries are the cheapest way. 

If you want something more generally useful you could spend more and get a 'solar powerstation' - basically an array of LiFe batteries with a battery management system and converters for 240AC and USB DC in a box that's easy to carry. We have one as we use it to power a fridge and kettle whilst camping.  

[Wooders28]

Chances are, they'll be someone you can borrow a spare plug from, (I always offer a tenner ,but no one ever wants any money) , it's not a huge racing community, so everyone is usually understanding.

The hard-core racers use petrol inverter generators, they're quiet and small enough, to sit out the way somewhere, and can be shared between 2-3 racers.

Some use a leisure battery , but they're quite heavy, so some have them on a porters truck, to help transport them.

I've seen some using a decent mah 3s batteries (or a few in parallel), and just plug them straight into the 12v port on a charger, but guess you'll need to work out how many watts you'll need to charge etc).

I normally charge a few the night before (the later the better, lipos don't like being left fully charged, did at one point think I'd charge them when i got up, but I'm useless of a morning...), so I'm not panicking trying to get them charged as soon as I set up.

Where is it you'll be racing?

 

[alvinlwh]

Powerbank + USB powered charges like ToolkitRC M4 Pocketnor ISDT 60PD/608PD. Alternative is rig up a clip/ciggy lighter to XT60 plug, charge off your car using a charger that takes 12V in by XT60. 

[Tamiyabigstuff]

I've used a car battery and an inverter out in the field to run a model railway at a local fair.

The wonders of modern technology can turn 12v into 240v and then back into 12v...

 

[Eric Bloodsmith]

I just use a 20,000 mah power block for phones and a 1A USB balance charger to top off my packs that I charge the night before.

[MadAnt]

Whenever I've gone to bash sessions where there is no power outlets, I've just hooked the charger up to my car's 12v battery.

[alvinlwh]

3 hours ago, Tamiyabigstuff said:

I've used a car battery and an inverter out in the field to run a model railway at a local fair.

The wonders of modern technology can turn 12v into 240v and then back into 12v...

Since your railway runs on 12v, can you not power it directly with the battery?

[Tamiyabigstuff]

6 hours ago, alvinlwh said:

Since your railway runs on 12v, can you not power it directly with the battery?

If I had a controller which takes a 12v input then yes, but I didn't have one available. 

[Mad Ax]

Work out how many races you will be doing in a day, and how many races you get from a battery, and how many batteries you have.

Also work out what extra electrical equipment you need.  Usually someone with a generator will have a kettle; pit lights can be battery operated.

Tyre warmers are a big drain on your power source and may dictate what sort of power you need.

I can generally get 2 races out of my batteries, so if I arrive at the track with 3 fully-charged batteries, I can do 4 heats and a final without needing a charger.  However, since I'm often racing at 2-day events, I'll be topping up the batteries throughout Saturday.  Once the first 2 heats are over on Sunday, I'll be rationing out what I have left so I can pack my charging equipment away early, and all my packs will be at least partially discharged, so I can wait until Monday to storage-charge them (I often don't get home until silly o'clock on Sunday evening and don't want to mess around unpacking chargers and batteries).

I've also always been a charge-the-night-before kind of racer.  I know the more dedicated racers are arrive-early-charge-on-the-day-discharge-before-they-leave types, but my batteries seem to last me a good few years, so I'm not worried.

My experience from years of racing:

Car batteries - you will see a few people popping their bonnets and attaching crocodile clips to the starter battery.  When you realise how little charging you may need for a single day's racing, this doesn't seem like a bad idea.  However it's worth keeping some jump leads with you (somebody will need them someday, even if you don't) and this is a problem if your pitting area is not near your car.

Leisure battery - heavy, awkward to carry, but effective.  Should get a few seasons out of a battery.  I replace the leisure battery in my camper every 2 years or so, and I used to keep the old one for racing.  There are some "smart" leisure batteries that have a built in monitor which sends the capacity and other data to an app on your phone.  At some events I pit directly from my van - I sit under the tailgate and have banana ports installed under the seat for easy power, however at some tracks the parking area is a long way from the track / pitting area so there's lots of walking, can't hear the announcer, can't chat to other racers etc...

Power bank - these are really popular now, probably see more of these trackside than anything else.  People oven bring them to indoor meets as they're easier than rolling out an extension lead to the venue power supply.  I have a 500W Awanfi with a 24Ah capacity.  It can run battery charger and tyre warmers for a 1 day event (practice, 4 heats, 1 final).  Needs charging overnight before it can handle a 2nd day, which is a problem at camping events.

Generator - not as expensive as they were, in fact can be cheaper than a power bank, although how long the unbranded ones will last, I couldn't say.  They are overkill unless a group of you are going to an event, and you can all share it; I feel a bit self-conscious firing up my generator just so I can run my tyre warmers.  Mine is a decade-old Honda, it's smokey and runs rough but it's a living, breathing thing, which is so much more fun than a power bank.  Requires maintenance, stinks your car out, needs fuel and is a theft-magnet.  You'll need to drain the fuel and carb if you're not using it for a few months, as modern fuel is horrible.

Borrow someone else's power - as mentioned above, usually a few people will bring petrol generators to the site.  They output waaaay more power than required, so generally people will let you plug in an extension lead.  I always offer petrol money but the offer has never been accepted; likewise I have never accepted an offer of money to borrow my generator, although I do accept biscuits, cookies and cakes, and I will allow myself to be included in the club burger cook-off.

[sosidge]

As @Mad Ax says, the "power banks"/"power stations" have become extremely popular over the last couple of years. They are not the cheapest solution, but the prices are coming down. Compact and lightweight with ample power. They're also something you can use for other hobbies/holidays that might need an extra power source.

Leisure batteries are still the cheapest but you probably need to factor in the cost of a charger if you don't have a suitable one already, and they are heavy. Probably too heavy for a lot of people in this day and age.

Generators have gone out of fashion, I see very few at outdoor meetings now, even the clean, compact "suitcase" generators are seen as anti-social. 

[Mad Ax]

3 hours ago, sosidge said:

They're also something you can use for other hobbies/holidays that might need an extra power source.

This is actually a great point.  My 500W Awanfi is small enough to fit in my (admittedly large) laptop rucksack.  My laptop battery only lasts around an hour with the screen turned down, but I can run it off the power bank for a few hours at full brightness.  I spend a lot of time in hotel restaurants that don't always have wall plugs, but I can work all night with the power bank.

[OnTheTrail]

I've been through this many many times.   Been trying to come up with the best way to charge airplane batteries from the field for years.   Over the years the batteries and planes have gotten much larger in capacity/voltage so what worked 15 years ago, may not work as well for now.   

-Tried charging from a the car battery.   It's not a matter of if, but when you'll draw down the car battery to the point where you will not be able to get the car started.  12V cigarette lighter ports can only handle so much current so be careful what you try to plug into them.   Also....most new cars turn off power to that port about ten minutes after you turn off the car.   You can charge from under the hood with alligator clips but keep in mind you will draw the battery down somewhere along the way.  

-Tried deep cycle batteries.   As mentioned above they are heavy.   Ungodlily heavy.   My younger back didn't like them, my old back certainly wouldn't.   Also, my experience as well as several of my friends is the deep cycle batteries are only good for about two years tops for the "somewhat affordable" lead acid types.   Sometimes you get lucky but there's a reason most retailers only offer a one year warranty on these.   A few friends have even tried two of these in parallel and one always dies off well before the other...???    

-With my various experiences, I'd recommend a small inverter generator.   (if you're in the US, Harbor Freight offers a 1400 watt for $429US).   While you may purchase this specifically for RC, somewhere along the way you will find a need to use it for something else (power outage, camping trip, need to power a tool far away from an outlet etc)

While I haven't tried the route of the lithium deep cycle batteries due to the fact that they cost as much as a small generator perhaps they'd last more that two years.  

[alvinlwh]

This post just reminded me, I have to discharge a battery that I brought on holiday but the car died before I can use it. 

I always loved USB PD* chargers and my first was a ISDT PD60 (as mention above, PD608 is a newer model). It is quite basic offering full charge only. Sufficient for charge and use situations. 

Then I got a ToolkitRC M4 (cannot find it at the moment) Pocket. It offers storage charge, reverse charging (a point I will get to) and XT60# input. 

My latest is a SkyRC B6neo+. It offers more features and higher power using USB PD 3.1 protocol. More importantly, it offers reverse charging at much higher power than the M4 above. 

#normally at home I power it off a 12v power supply through the XT60 that also powers my diesel heater. 

The battery connected is nearly full at the moment. 

Reverse charge feature. 

Wired up to charge my phone. 

The M4 reverse charge at 18w but this can charge the phone at the full 30w.

This way, instead of using a discharge which just turn energy into waste heat, I put the energy into the phone which is now being used to post this. 

*make sure your powerbank has at least USB PD, and for safety, I charge at 2A off powerbanks as I had blew up a QC wall plug by going higher before. There are some powerbanks like @Mad Ax's 500w one that can push serious power to charge laptops, most do 18w - 30w. I do not want to blowup two lipos at the same time so I played it safe. In theory, USB protocol means supply and demand should communicate with each other to establish the best power flow, but I had seen it fail spectacally before. 

[Tbird232ci]

I've been looking to get into parking lot racing this season. Most of the places who host the races will have a generator but I ended up digging into using a portable battery like a Jackery or the ones sold by harbor freight.

I'd say that it'll depend on the type of racing you'll want to do, and how you'll want to treat your batteries. A lot of stock racers will charge at 30-40 amps. A generic car battery or a deep cycle battery wouldn't break a sweat at that. With that, some chargers such as the Toolkit M8d will do regenerative discharging where you basically dump all of the excess power from the battery back to the source battery. You can discharge at 20 amps that way. Most chargers can't charge at high amp rates unless they're powered by DC making a battery or a stand alone power supply being the best option there.

Using a power bank is definitely convenient. They are nice if you want to set up things like a fan, lighting, a kettle for you cheeky Brits, and so on. Some are nice as you can also have solar panels to recharge as the day progresses. You'll have to be mindful of output ratings and be sure that it can pump out enough power for a power supply if you do intend on charging at high amp rates. It shouldn't be a problem but the less expensive ones do like to lie about their ratings. They also do tend to be a bit more expensive than a car battery.

My personal choice would be a car/truck battery. A generic battery that you would have in a tractor/trailer weighs about 65 pounds which is fairly heavy, but it has roughly 96,000mah. That will charge a TON of batteries and they are used to abuse. I just came across a really neat collapsible hand cart at Costco which would make lugging a battery around much easier.

[Mad Ax]

10 hours ago, alvinlwh said:

Then I got a ToolkitRC M4 Pocket. It offers storage charge, reverse charging and XT60 input. 

I have one of these too - a very neat bit of kit, and it feels good to use the charge in a LiPo that would otherwise be wasted to top off my phone, charge my camera, or power any other USB device.

It is kinda finicky though - sometimes it won't charge anything and it's not clear why.  It's probably due to one of the cells reaching a cutoff voltage, but since it doesn't explicitly state this anywhere on the screen, it's hard to know.

I like the look of the SkyRC one.