3800 MAH batterys at 130mah trickle charge

[purplerob]

ok doen and dusted, i got a KO BX-213MH . just a bit over budget []. but it sounds really sweet.

if i could past the ebay link i would

[XanderP]

quote:Originally posted by purple_rob

if i could past the ebay link i would

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Im pretty sure you can as long as the auction is finished.

[purplerob]

well it is my link and im sure they can take it right off if its being naughty

http://cgi.ebay.co.uk/KO-BX-213MH-CHARGER-...1QQcmdZViewItem

[jimbo858]

okay so how long will it take to recharge a 7cell 3300Mah NiMh pack using a 4.5amp peak charger?

[raemin]

There is a 40% loss of power when chargin batteries, so time should be adjusted, but voltage should also be taken into account:

A 1Ah 7.2v pack battery charged at 7.2v 1A will take roughly 1.40 hours (i.e 1h24min)

A 1Ah 7.2v pack battery charged at 12v 1A will take roughly 1.40hours*7.2/12 (i.e 50min)

Theo please correct me if I am wrong...

Now cone into account the charge rate: a high charge rate is acceptable if the cel internal resistance is very low. the main avantage is that this high rate will bust the internal "dendrite" (the litlle cristals that builds up within the cell and tends to short it by building "bridges" between + -). A High charge rate also permits to more acurately detect the "peak". However a high charge rate deteriorate the chemistry of the cell. Personnally I would tend to prefer an initial burst at 2C or 3C followed by a charge at 1C. A better option is a periodical zapp of the cell (short a 60v burst). I remember my father and uncle zapping their pack with automotive 12v batteries: was pretty freaking but would revive (or difinitively kill?) any battery. I have no experience with 3800 so cannot say for these batteries.

To answer your question, trickle charge is Ok but won't prevent your battery for building up internal shorts in the long run. In order to avoid this phenomenon, never leave you battery fully charge (self discharge is producing lots of these), and just ask on of your friend to cycle your batteries from time to time with a strong charger.

[jimbo858]

quote:Originally posted by raemin

There is a 40% loss of power when chargin batteries, so time should be adjusted, but voltage should also be taken into account:

A 1Ah 7.2v pack battery charged at 7.2v 1A will take roughly 1.40 hours (i.e 1h24min)

A 1Ah 7.2v pack battery charged at 12v 1A will take roughly 1.40hours*7.2/12 (i.e 50min)

Theo please correct me if I am wrong...

Now cone into account the charge rate: a high charge rate is acceptable if the cel internal resistance is very low. the main avantage is that this high rate will bust the internal "dendrite" (the litlle cristals that builds up within the cell and tends to short it by building "bridges" between + -). A High charge rate also permits to more acurately detect the "peak". However a high charge rate deteriorate the chemistry of the cell. Personnally I would tend to prefer an initial burst at 2C or 3C followed by a charge at 1C. A better option is a periodical zapp of the cell (short a 60v burst). I remember my father and uncle zapping their pack with automotive 12v batteries: was pretty freaking but would revive (or difinitively kill?) any battery. I have no experience with 3800 so cannot say for these batteries.

To answer your question, trickle charge is Ok but won't prevent your battery for building up internal shorts in the long run. In order to avoid this phenomenon, never leave you battery fully charge (self discharge is producing lots of these), and just ask on of your friend to cycle your batteries from time to time with a strong charger.

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So, we should discharge both ALL types of batteries when we store them? (NiCd, NiMh, Lipo) or does each type get handled differently?

[DJTheo]

NiCDs yes, NiMH many say store only half charged, LiPos shouldn't be completely discharged, that's why LiPO ESCs have a shutoff when a low voltage is reached.

Raemin, excellent post, no disagreements! [^]

Cheers

[raemin]

As Theo says:

> The NiCd self discharge rate is much lower than nimh, hence you let them fully discharged.

> The Nimh do have an important self discharge rate, hence it is preferable to store them slightly charged (1/3

is the recomended rate). And fully discharge them prior to recharging them.

> for lipo the technology is different and there is almost no self discharge and no internal build up. Technically you could store them either discharged at 3v or fully charged. On a safety point though a fully charged lipo may cause a much stronger explosion than a discharged one, hence the recomendation is not to leave them unatended & fully charged.

There are some prety good recomendations on all these battery maintenance either on the schulze charger manuals (the wording is poor but content is good), you may also have a look at www.ni-cd.net (partially in French).

There are pros and cons regarding full discharge. To tell the truth this is the best way to equalize batteries (true for NiCd) but also the best way to kill them also (very true for NiMh) ... In any case when fully discharging a battery, the end of the discharge should be at very low amps: I personnally discharge my NiCd packs at 0.5A till 0.9v per cell and finish the job with a 430ohm resistance + led + diode (takes 3 days to fully discharge the pack down to 0.1v per cell). This very slow discharge will equalize the pack without strong reversal of the weak cells. A weak cell is the one that tends to be discharged before the other ones. At 30Amps a weak cell within a pack will be tortured by the other cells of the pack that will still maintain a high flux of current tthrough the weak cell and reverse it. If the current is very slow the weak cell may receive a reverse current, but not enough to reverse it.

For Nimh I equalize the pack the other way: instead of fully discharging I fully trickle charge at C/40 : in this case the cells that get charged first are not damaged by the extra current.

Recomendations for long storage procedure / maintenance

NiCd (The idea is to equalize the cells through a low final discharge): discharge pack (normal discharge) add a full discharge (end discharge rate should be 10mah). At that point the battery can be stored. After the long storage period cycle the battery at least 3 times.

Nimh (The idea is to equalize the cells through a low charge): discharge pack, recharge it at 30%. At that point the battery can be stored. After the long storage period slow trickle charge at C/40 during 2 days and a half, and after that cycle the battery.

Lipo (The idea is to equalize the cells through individual charges): strore them at 3v per cell (safer), after storage charge the pack at 80% and finish the cells individually (which equalize them).

As you see the whole idea behind it is to have cells "equalized" and avoid as much as possible self discharge of Nixx batteries. My tamtech / kyosho baja bug batteries are still -relatively- strong after 15years, so are my 1700SCR packs, and I personnally pretend to buy fresh packs every 2 or 3 years only ... My suggestions are consequently valid for long lasting packs but for pure performance the barbarian options might be better : brute discharge, brute charge, zapping, discharge tray, etc.

[RETRO R/C]

A discharge tray is not barbaric[:0] - the amperage discharge is low. Trays like the novak let you choose the voltage per cell that you want to go down to. There are ones on the market that will rip 35 amps out of your cells if you are racing - but bashing does not require this.....we want to use all our charge in our cars!![]

NIMH dont suffer the memory effect whatsoever - so the discharging is not that critical for mucking around. It is only when you are trying to squeeze the very last out of the cells for racing that you take the very time consuming route of dicharging, 1/3 charging then discharge again before fully charging......

Slow charging any cell is always going to be the very best for the older cells in particular - but as most of the newer cells on the market are designed for rapid charge and discharge it matters little. In the real world you are only going to let your cells live 50 to 60 cycles more by trickle charging them......frankly, the advantages gained by fast charging and the subsequesnt higher output the cells provide by being charged at this higher rate far outweigh those few extra charges with lesser performance![]

(I am not trying to contradict anyone here - or be argumentative - just want to clear that up so no one thinks I am being reactive etc etc)id="red">id="size1">

Li po cells are a whole different kettle of fish - they are highly volatile, fragile cells and really do need to be treated with respect. I have seen many cells die from what we could consider to be gentle treatment. I use them in my heli's and micro cars. In the cars in particular you have to be wary of not discharging them too much. When the car gets slow - you need to stop running. I have killed a pack because I drove too long (because I forgot that my car did not have a voltage cut off like my heli's)....cells are dead - never to return.........expensive mistake.[]

For the point of the story in this thread though, - intellect themselves recommend a 6 amp charge. Discharge to 0.9v per cell - and leave em till you are ready to charge again.

There are so many methods, as I mentioned previously. I am trialling a few at the moment - always something to learn....all the suggestions here have merit. At the end of the day though for bashing, just use the kiss priciple : Keep It Simple Sam

Cheers

Darryn

[DJTheo]

Very nice infos posted here [^], wanted to add though to some degrees also the newer battery types (NiMH and LiPo) show memory effect, only its less then on NiCDs. Actually always when a new type comes to the market, advertisments shout "no memory effect", till the next type comes out which again has it for the first time... []

Cheers

[RETRO R/C]

LOL - you are right about the adverts on memory.

I have to be honest though and say that these latest NIMH cells like the GP3700's and IB3800's really appear to hold their "match" longer......these days the manufacturers are certainly going for low internal resistance and high voltage, capacity really is becoming less of an issue. I never thought I would say it - but I am manking run time comfortably in touring car quite easily with these latest cells - and I am running a 7 single............unheard of less than 3 years ago!

The "memory" effect now is a fading issue - cells hiolding their low internal resistance and voltage is the issue..........but that is racing - and that will bore most people here....

Good thread for sure though.

Nice purchase Rob - that unit should see you well for a while to come mate.

Cheers

Darryn

[jimbo858]

whoa... that's whole bunch of info. now I just have to try to understand it all to put it in perspective. good info though...

still don't know how long it should take to charge a 7cell 3300 Mah NiMh battery pack using 4.5amps. but, still good info.

[raemin]

quote:Originally posted by RETRO R/C

A discharge tray is not barbaric[:0]

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By barbaric I meant high amp / high costs... One cannot safely use high discharge without a certain investment. You are very true regarding the general idea of a high charge rate + safe discharge down to 0.9v

To get back to the subject sounds curious to spend money on a very high end 3800 pack and not offer it the charger it deserves. An ultramat5 charger by graupner can charge at up to 5.5amps for 30euros. add to this 5euro for a DIY mild discharge tray. That's barely half the costs of the 3800 (or not)?

another point to take into account is that nimh do not require sophisticated charge as nicd that were highly benefiting from reflex chargers, burst charges, etc... A plain charger capable of delivering high amps is fine.

[RETRO R/C]

"By barbaric I meant high amp / high costs... One cannot safely use high discharge without a certain investment."id="red">id="size1">

I was refering to the discharge tray, they are not high amp draw, I mentioned that. Making a cheap one is not hard either, it is only to bring the cells down to 0.9v each. I also agree on the relative trade offs with charging at high amps, as I put in my previous postings.

I dont think Rob has "high end" cells?? Not sure. Actually, if anything, these new cells are quite cheap in un-matched form...

Just like the Ni-cad, many racers are finding that the "reflex" and or "step" method of charging is indeed giving them much inproved performance. A standard delta peak charge is just fine for just about any cell for bashing.

Agree totally - you dont have to have all the bells and whistles, but Rob wanted something good value for around 60 pounds. So I did a quick search on a uK shop, (I am on the other side of the world and have no idea what is selling over there), and made some suggestions from just one shop. I have heard of the ultramat - nice and simple. It is still handy to have a discharge feature, and variable current.Also great to have the ability to charge transmitter packs etc etc.... Just depends on your budget.

jimbo858 - at 4.5 amps, depending on the condition of your cells with things like internal resistance and voltage etc, I would anticipate that your 7 cell should take around the 40 to 50 minute mark. Alot depends on the charger as well.

Another thing to keep an eye on with these new IB3800 cells is that they perform at their very best when freshly charged and quite warm from the charge. DO NOT cool the batteries as you are charging them - as this inhibits the natural chemical reaction that is producing the power in the cells. This goes for bashing or racing.

Cheers

Darryn

p.s - Again - I am not being argumentative. I just want to cover that base, as it seems a couple of people seem to think I have been in the past, and this is definately not the case. I am just trying to share my passion with fellow enthusiasts like everyone else here..[]id="red">id="size1">

[nigeninja]

Damm fine info so far ,but can anyone clue me in then please.

I brought a Nosram Sirius charger,to charge up my 3000 Ni-MH cells but ever since I've had it its seems to over charge cos when its finished the cells are always too hot to handle.

So I thought it was a dodgy charger and had it replaced but this one is just the same.[V]

As this charger is meant to be all singing and dancing I thought it would not do that.

So anyone out there want to giz us a clue please.

[RETRO R/C]

Hi nigeninja,

I have very limited experience with the Nosram/LRP (both the same factory - just different name and colour)....

Warm to hot NIMH cells is fine. Are you able to adjust the charging threshold on the charger - if so - try 4 or 5 millivolts per cell....that should help a bit. Do not nbe to concerned though. If the heatshrink is splitting - then it is time to be concerned!

When my 3800's come off the charger - I can only hold in my hand for about 10 secs before it becomes uncomfortable.

Cheers

Darryn