Well, this is what I want to do. I want to have a snazzy-dazzy toggle switch under one of my front hatches of my HL Tiger. I intend to put two batteries in parallel, have a red light be on while charging and a green light when the power is applied to the tank. Please tell me if this makes sense!

If you're using a peak charger, the diode may prevent it from detecting the peak. Plus it will have enough wattage to handle the charge current.

D.

The red LED is suppose to tell me the batteries are charging and the green LED is suppose to tell me the batteries are supplying power to the tank. Should I scrap the RED Charge indicator light?

To be honest, I think you can dump the Diode, as it will only protect you if you manage to connect the charger up the wrong way. But if you are using a molded plug /socket affair that is hard wired to the charger this shouldn't be an issue. I am a little worried about the battery packs hardwired together. I suggest that you stick with a single pack, but with a bigger capacity. Re the LED's they will make no odds, but why the green one when the headlights flash on power on?
Otherwise I'm completely in agreement with darkith.

Yours Simon M.

I think he put the diode in to prevent the batteries from powering the LED, otherwise the red LED would be on all the time. (Might drain the battery in around 100 hours maybe).

Like Simon says (remember that childhood game?), the LEDs probably aren't essential. Since you have the switch wired to only allow the batteries to *either* be charged or power the tank (not both), there's no real danger.

D.

Err whoops missed that D.[sm=red_smile.gif]
I wonder if a 2.5mm switched power jack would be up to the job? Probably not, might over heat of battle..

Yours Simon M.

To be sure, the LED indicator would have to be in a secondary SERIES path to acurately determine current flow to the battery.

The way its currently configured, you are only assured of verifing the charger is engaged, not the batteries.

A transitor based current sensor with LED indicator, would tell if the batteries are truely being charged or the tank being supplied power.

All in all, they really would not be needed when the switch can show CHARGE and ON positions.

I suppose the ideal solution is to have the charger tell if it is charging/charged/disconnected, this way the red led & diode inside the tank problem disappears.

Yours Simon M.

Why am I not advised to connect two 7.2V batteries in parallel?

Also, does it matter if I choose between NiMh and NiCD?

Nothing "wrong" with having them in parallel, only problem I think is if you're trying to charge them together with a charger made for charging less than 12 cells at one time, might be wrong (not my specialty area)

12 cells has nothing to do with it.
2 2000mah 6-cell packs in parallel will appear to the charger as if it were a 6-cell 4000 mah pack, which would take twice as long to charge as a single 2000mah pack.

Overall, the recommendation with parallel packs is to separate them for charging, to ensure that each pack is properly charged to it's peak. You could use a switch or unplug the y-harness.

*If* the packs are charged in parallel, there's a fair chance that one pack will peak before the other, and the charge may detect this false peak and stop charging, leaving one pack mostly charged but not fully charged. In the *worse* case, the charger might miss the peak of the first pack if the other pack is still soaking up current, and end up over-charging one pack.

I wonder if it's more of an issue with high-performance vechicles (cars, planes, boats) than with tanks, which generally aren't sucking a pack dry in 5 minutes of racing. You might be able to get away with it, but I'd avoid fast charging the packs in parallel. Use more moderate charge rates, and check the temperature of the two packs. If they're similar, you're probably okay. If one gets really hot, it's being overcharged. If one stays really cool and never gets a hint of warmth, it's probably being undercharged.

D.

D.

You don't need leds if you have a good peak charger: the charger itself will perform all the tests upon connection.
Also, the chargers could handle 12 cell elements, but when in series.
I cant' see how a charger would correctly handle 2 packs in parallel in case of different discharge levels.


edit: Darkith explainded it better at the same time I was writing the reply.

Have a look at this [link=http://www.direxplorers.com/dir-equipment-configuration-articles/328-nimh-batteries.html]Artical[/link], it explains it faster than I can type and better!

Yours Simon M.

Interesting article

What do you guys recommend? The included 1700 mAh battery is a bit weak since my tank will be getting heavy with metal wheels, metal tracks and metal everything. Would 3300 mAh NiMh be sufficient for, say, 40 minutes of tanking?

Sorry to duck the question, but how long is a piece of string..
Ask yourself how long does my 1700 last, then approx double it. From my car days, with the kids, I found that the batts go 'off' quite quickly, that is when they are getting on a bit they don't last as long or give as good a punch, and take longer to charge. In the end I lived with a stack of cheap 1700's and just kept swapping them around. If you get a car based fast charger, and around 4 of the 1700/2000, then you could keep going for ages, charging one set whilst running another.
Or that's my master plan!

Yours Simon M.

Umm I wonder if any one has nitro'ed there tank yet??

Yours Simon M.

People have, but they end up with a slow, noisy, smelly, oily heap...

Reminds me of the car I drive!
Yours Simon M.

Matt,

Think of it as two water balloons hooked to a 'Y' shaped hose. your switch is a valve on the leg of the 'Y' that switches between your tank, driven by a water wheel, and a big 'smart' tank of water (the charger). You run the tank's water wheel untill the balloons are almost, but not completely, empty. Then you recharge the balloons by switching to the water tank. The balloons begin to refill. The 'smart' water tank senses that water is flowing out of the tank and into the switch (and thus the balloons) and everything is fine. As the balloons fill, one reaches capacity before the other and the water flow decreases. The flow is still enough that the "smart' charger still thinks that all is well, but,,, the full balloon begins to rebound and starts pushing water out and into the unfilled balloon, further decreasing the flow from the charger. The charger senses that further decrease flow and thinks everything is full, so it shuts down. The two balloons equalize the water levels, which leaves both below optimum charge, and then begin to leak back into the charger's back end..

I suggest that you setup your switches so that you can charge one batt at a time, if you are using a smart charger. If you use the stock charger, you are better advised to charge one batt at a tim, but you can get away with charging two in parallel, but you'll be putting a strain on the stock charger. See PzrWest's post on cooling mod to the HL stock charger.

splat