Using your charger in vehicle

We see lots of charger/cycler manufacturers advise against using the charger when the car is running. I've never experienced a problem. Never have it plugged in when starting the car, but as soon as it is running it set up to charge on the way to the field.
Has anyone experienced a problem here? Kind of charger, make of vehicle - any details would help.

Red Scholefield wrote:
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All I can think of is that they're afraid of load dump; if you design devices for automotive applications you gotta pay attention to that or plan on having _lots_ of product returns.

Tim, Exactly what do you mean by "load dump" I've not run into that term associated with automotive devices. But then I don't have all that much experience in that specific area.
Red S.
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Load dump.
The starter motor is an inductive device. You cannot stop current instantaneously in an inductor.
When you stop cranking, the current reverses direction from the starter motor into the vehicle wiring harness, known as "load dump" or "inductive kick".
This reversed current can induce large voltage spikes into the vehicle wiring harness.
Typical tests for automotive devices can involve voltage spikes of 90volts or more usually lasting mico seconds
RCS
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So you are only supposed to use a DC charger in your car with the vehicle running or stopped?
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Wouldn't the capacitance of the car's battery being connected act as a filter against spikes?
RS
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It doesn't -- load dump is real, and must be dealt with in any automotive (or aviation) application.
Red Scholefield wrote:
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| It doesn't -- load dump is real, and must be dealt with in any | automotive (or aviation) application.
More accurately, the battery does filter (though I'm not sure filter is the right word) the spikes, but not completely.
If you take a running car and disconnect the battery, the odds of you frying the entire electrical system are quite good, since there will be nothing to stop any spikes anymore.
Personally, I run my chargers in the car with the engine running or not, and have for years, and so far have had zero problems ...
| Red Scholefield wrote: | > Wouldn't the capacitance of the car's battery being connected act as a | > filter against spikes?

Doug McLaren wrote:
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IIRC much of the concern about load dump is loose connections, either to the battery or elsewhere. There's no reason you couldn't build a battery charger that could survive the transients, but you'd have to add circuitry, and cost, etc. -- it's much easier for a manufacturer to just impose a blanket veto on operating on a running car.
What it probably boils down to is this:
Having a feature on the outside of the box "you can charge when your car is running!" doesn't outweigh the extra $10 or $20 bucks they'd have to charge for the thing. Just telling you "no" in the instructions means that by the time you find out you've already bought it and opened it. Leaving off the cigarette lighter plug means that if you _are_ using it in a running car then you've modified it, you bad boy, you can't return it and it'll be difficult to sue their pants off.

Has anyone actually seen any charger manuals that state not to use it when the vehicle is running? As I recall I only found one.
Red S.
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Red Scholefield wrote:
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I saw that and was kinda ignoring it for the purposes of spouting off about load dump.
While doing so I was wondering if the longevity of Doug's charger is due to luck on Doug's part or planning on his charger manufacturer's part?
And can I put a cigarette plug on my Triton and charge things in my car? The only reason I haven't is 'cause opening the hood reminds me to keep the batteries away from all that flammable upholstery while charging.

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I did that, ignoring the cue under the hood. Should have paid heed 'cause it does present a hazard. Popped the fuse, and until I got to Rat Shack for some spares, it caused some anxiety for other drivers while I was fumbling around in the glove box trying to find a matchbook.
Abel

Wouldn't the capacitance of the car's battery being connected act as a
filter against spikes?
RS
Red, one would think so. However the ESR of the battery is high when i comes to a high voltage short time spike as as been noted.
I had a CB on a cigarette lighter plug about 1978 and stopped at a res stop. I forgot to turn the radio off before I started the car. Poof al gone. BTDT. It won't get you every time but it will eventually
-- Iflyj
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Load dump can also occur when loads get switched out of circuit, not just on starting.
3for3 wrote:
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I have measured a 600 volt spike from a starter solenoid coil. The starter itself will also generate a spike, but probably smaller since it has far fewer coils than the solenoid. At any rate, that spike finds its way into sensitive electronics and fries them if they aren't protected. The guys successfully using chargers in their cars will have chargers with internal protection. The protection doesn't have to be expensive. A Zener diode across the supply will short to ground a spike, as will an MOS device. In our Cessna airplanes an ordinary diode is connected across the master solenoid coil to short the spike generated at shutdown; the radios in an airplane can be worth as as much as the rest of the airplane. The diode is $28 from Cessna but $.25 from an electronics shop. Same diode.
Dan

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Yeah, if you are certified...

On Wed, 10 Aug 2005 20:29:50 -0400, "Red Scholefield"
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It's always worked for me, except for LiPo's, as the club where I use them doesn't allow them to be charged at the field. Actually, I wouldn't have any qualms about charging them at the field where I can properly monitor them, but I'm not yet confident enough in the LiPo charger technology to be comfortable with charging them in my vehicle while my attention is necessarily on driving.
Abel

AP
There are millions of LiPo powered cell phones being charged while the vehicle is running.
Are you serious? A club that doesn't allow LiPos to be charged at the field? Must be in Kalifornia, right? :-) How did this ever get passed by the membership? Or is it an anti-electric thing and this is just a means to an end.
Red S.
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On Thu, 11 Aug 2005 08:53:55 -0400, "Red Scholefield"
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Yes, and there are no controls on the charger for the user to possibly set in error, and their battery packs have charge protection modules built into them. Ours don't.
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It's a lot better than the policy that preceded it. Lipos were not allowed to be at the field, period. It did not get passed by the membership (nothing is), but was dictated by "the board."
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I expect we will see more products offered in the hobby market that will incorporate charge protection. However I don't suppose that will change your "the board" . Ignorance can be fixed, stupidity is incurable. Who elects these clowns anyway? If there is a good answer lets change the thread subject for it and keep this one on topic.
Red S.
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field?
an