Using 2 x 12Volt battery packs in series . Is it possible ?

clawnfish

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Nov 28, 2014
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Hi,

I need a battery pack of around 24 volts and 5 - 6 Ah to power a 100Watt COB LED Module. I live in Europe and could not find anything fabricated ( there are LiFePo battery packs but I want to use Li-Ion/LiMn based battery pack ).
I have searched the forum and googled it but could not find anything about it.

But there are quite some options for , for example 12Volt 5Ah battery packs ( 3S2P ) . So if I can connect/use these in series , I can have a 24Volt 5 Ah batterypack which consists of 2 seperately PCB protected packs and I can carry and charge them separately too.

So , when I think about it , it all makes sense but I just want to be sure if there are any problems/danger with this approach.

Any input is highly appreciated

Thanks in advance
 

mattheww50

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The only potential hazard is if the negative terminal of the battery pack is connected to the frame or anything else other than negative terminal of the battery pack. As long as the positive and negative connections on the battery pack are connected to nothing else except that positive and negative terminals of the pack, you are safe. The bind is that in some packs, the negative terminal of the battery is connected to the frame (much like in automobile)of the pack. If it is connected to the frame, and the frames of two packs touch, you have a short circuit for one of the battery packs, since the negative side of one pack is connected to the positive side of the other pack. YOu just need to make sure that the wiring to/from the batteries only connects to the battery terminals of the pack. As long as you do so, yiou should be OK.

However there are always hazards associated with series connected Li-Ion batteries, which is why people who use series connected cells use protected cells, and in packs, often are equipped to do balanced charging.
 

clawnfish

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Thanks for the explanation mattheww50. Very useful information . I think I will be better trying to find a single pack in those specs to be on the safe side .
 

lucca brassi

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I need a battery pack of around 24 volts and 5 - 6 Ah to power a 100Watt COB LED Module. I live in Europe and could not find anything fabricated ( there are LiFePo battery packs but I want to use Li-Ion/LiMn based battery pack ).

LiMNO4 /24V (or 36V ) battery packs are standard for e-bikes

http://shop.strato.de/epages/613330...61333079/Products/"ASN E-Bike-Block 24VV15Ah"

http://www.linergy-shop.de/product_...v-23-2ah-aus-panasonic-ncr18650pd-zellen.html

call them and ask for costum configuration
 
Last edited:

tamas970

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Jan 23, 2013
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NiMH or Lithium?

Dear All,

I am in the process of rebuilding an old halogen dive light, and considering the power options. As for light source I most likely stay with halogen because of the high cri/good color rendering -> if someone
knows a 30-50w LED module, that performs well in this department (even spectrum, CRI93+, ~4000K) I am also open for changes at a later stage.

Back to the battery question - I ask for some logic check here:

The energy demand part: 2x100W 12V halogen bulbs, 60minutes runtime = 200Wh capacity needed at a current draw of ~17A.

NiMH option1 (original setup of the light): 10x SAFT NiMH 15Ah 1.2V F-cell (weight: 265g) This F-cell in theory has 18Wh capacity or 68Wh/kg - expected runtime is ~50min.
Advantage: less cells to deal with. Besides, the SAFT cells easily deal with the 17A discharge. However, their weight will be close to 3kg/6lbs. One question here: does anyone
know a higher cap F-cell (or >10Ah D).

NiMH option2: eneloop pro's (2.9Wh/piece or ~100Wh/kg) -> 70-80 pieces are needed
:faint:
. True, I could save about 600g weight or add some capacity. Advantage: some
added capacity, and I would not exceed the 12V limit.

Li-ion option: 20x 18650 cells, weight around 1kg/2lbs. -> one issue here: a charged 18650 can exceed 4V(!) alltogether killing the bulbs with 16V(!!!). From the capacity point of view I
like this option the most, however, somehow I want to limit the peak voltage.
 

tamas970

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Jan 23, 2013
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Re: NiMH or Lithium?

I am still awaiting shipping. I'll return with the sizing once I got the battery tank in my hands. 10x F-cells (32x90, original setup) certainly fit in. The tank measures outside 100x345mm, which is a bit oversized for
the F-cells - how much exactly I'll find out.

Looking at the discharge curves of the lithium and the NiMH cells, I am more set on the NiMH option. The 18650's usually start at 4V/cell, which translate a 25%(!) overvoltage for the bulb (candidate: Osram 64623 HLX,
design life 2000h). OTOH, if the bulb survives the overdrive, and nothing melts in the lamp head, I could get a nice pair of mobile Sun's underwater:).

It makes sense if you tell us the required dimensions of the battery pack ?

you also have to calculate weight between old /new setup .
 
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