geopaj

Simultaneously charging 2 batteries with 1 charger?

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My son and I both have RC cars with matching 2,000mah nimh batteries (same age, brand and capacity).

We also do a lot of camping away from mains power.

I have bought a Imax B6-AC (ie https://www.hobbyking.com/hobbyking/store/__6478__IMAX_B6_AC_Charger_Discharger_1_6_Cells_GENUINE_.html) which can be run on mains power or off the car battery (I have a 4x4 with an auxiliary deep cycle battery for running a car fridge and other accessories).

Charging the batteries at 1c (2amps) obviously takes about an hour per battery which means it takes two hours before both cars can be run again.

The charger can charge up to 6 amps.

Could I make up a "double adaptor lead" to charge both batteries at the same time and set the charger to 4 amp (two 2,000mah batteries = 4,000mah so 1c would be 4 amps).

This would 1/2 the time required to charge both.

When not camping the batteries would be charged desperately via mains chargers (I have only one charger capable of running off 12v)

Is this plan sound / safe for occasional use when camping?

Could I do this with LIPO batteries? (If yes, how would I wire up the cell balancing wires?)

I assume, as LIPOs can often be charged at over 1c I could even bump the charger up to 6 amps, assuming the LIPOs are 2,000mah??

Thanks

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For NiMh and NiCad it should work fine if you wire them to the charger in parallel as essentially here you have just created a bigger battery, however the 2 batteries do need to have been discharged to roughly the same amount in order for charging to be even (measuring with a multimeter individually would ascertain this).

As far as LiPo goes you would essentially be treating 2x 2S batteries as 1x 4S battery and so you would need to make a 4S to 2x2S balance lead but personally I'd prefer to use 2 LiPo chargers and do it that way as I don't thing I could trust the technology enough to start patching wiring in to make it work.

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Whether you can do 4S off a 12V source *reliably* is an issue.

Even decent chargers aren't so reliable when running voltage boosting internal circuitry.

HK sells a few models of Multi chargers that do 4 or more packs at once.

Worth it for flexibility of independently starting/ending charge alone.

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For NiMM/NiCd no parallel charging, delta peak detection will most likely not work.

For LiPo if they are discharged at roughly the same voltage, you need Y cables for both power and balance connectors

Easiest way is to use two separate chargers or one dual port charger

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Whether you can do 4S off a 12V source *reliably* is an issue.

Even decent chargers aren't so reliable when running voltage boosting internal circuitry.

HK sells a few models of Multi chargers that do 4 or more packs at once.

Worth it for flexibility of independently starting/ending charge alone.

For NiMM/NiCd no parallel charging, delta peak detection will most likely not work.

For LiPo if they are discharged at roughly the same voltage, you need Y cables for both power and balance connectors

Easiest way is to use two separate chargers or one dual port charger

WillyChang and danb1974 - could you please suggest sure chargers? I would prefer a charger that will run on both mains power (240v in Australia) and automotive 12v (which is really 12v-14v, depending on if the engine is running)

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Hobbyking has a good range of chargers, since you're already aware of their offerings.

Have seen ppl use the HK Eco4 and Quattro, Turnigy etc units locally and they all do the job

when you're lucky enough to get an example that is reliable.

For out in the field... I'd prefer the DC-only B6 IMAX or HK Eco6 and have multiples

instead of a 4-in-1 unit... pricewise they ain't far off & if one blows up, you are not all lost ;)

When 240V is available, I use a 13.8V PSU... gaycar sells decent units but they don't come cheap.

I've for a 20A unit that travels (good for 2-3 chargers) and a 60A monster on workbench.

HK might sell some ok ones, avoid the small computer plugpack types.

For all-in-1 single pack duty, I use a SJ Swallow EQ :) popular little AC/DC job in Australia.

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