lipo help

hi,i need info on lipos.i have 20ah of lipo units and have worked out ish that i can only use 10 ah of power before lvc stops bike.i am using the never above 4.1 and never below 3.65 rules.
is this normal as it seems a waste to carry 20 ah and only use 10 of them.
the batts. are turnigy 5000 mah at 20c and i have 8 of them .

cheekybloke said:

ok thanks I will go ask elsewhere MR CAPITALS i am sorry i did not know where to post

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Sorry you don't like my text formatting. Good luck with your problem....

I think that going as low as 3.5 V is OK. I wouldn't drop lower though. Charge em up to 4.2 V and you'll get most of their rated capacity, but don't leave them up there for very long without going for a bit of a ride.

Your lvc is set to 3.65v? Set your lvc lower, so it will stop your discharge when at 3.65 resting. Are you seeing more like 3.85 after you stop, and the packs are at rest?

Other factors may be involved as well, as said in another thread just today. Cold will cost you capacity. As will a high discharge rate. And lastly, you lose some more charging to 4.1v.

However, it depends on what matters more to you. Carrying more than you need, or buying more all the time. My routine for years has been carry 10 to discharge 7-8 ah. But that's not as bad as you seem to be getting. When I stop at 5-6 ah though, I'll see about 3.85v per cell at the end.

You are running 4p right? if not, then you have a 10 ah pack.

Likely you are seeing half an ah per pack loss from undercharging. Then it might be another half ah from cold. x4p there's 4 ah gone right there. If you are stopping early, it could add up to 10 ah real easy.

dogman said:

Your lvc is set to 3.65v? Set your lvc lower, so it will stop your discharge when at 3.65 resting. Are you seeing more like 3.85 after you stop, and the packs are at rest?

Other factors may be involved as well, as said in another thread just today. Cold will cost you capacity. As will a high discharge rate. And lastly, you lose some more charging to 4.1v.

However, it depends on what matters more to you. Carrying more than you need, or buying more all the time. My routine for years has been carry 10 to discharge 7-8 ah. But that's not as bad as you seem to be getting. When I stop at 5-6 ah though, I'll see about 3.85v per cell at the end.

You are running 4p right? if not, then you have a 10 ah pack.

Likely you are seeing half an ah per pack loss from undercharging. Then it might be another half ah from cold. x4p there's 4 ah gone right there. If you are stopping early, it could add up to 10 ah real easy.

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thanks dogman,my understanding of any electrics is way worse than basic.
all these numbers and letters do nothing but confuse me as well as all the conflicting info.your info says 3.65 min and then you tell me to set it lower?that type of confused.
i used 5 amps on a run and the cell voltage was 3.89 when i had done.it is very cold here especially in the shed where i charge.not sure what 4p means either.
i have 8 packs of 5000mah 20c turnigys and have 4 packs stacked together on each side and then jumped to make right voltage.dont understand series and parralel (stoner moment again).i use the hk quattro charger and stop at 4.1 or 4.11.how is cold costing capacity,is it during charge or use?
motor kit is aft limited to 40a with lvc at 44v are these figures correct?
sorry for being a bit thick

yes. way worse than basic you should start with some basic knowledge. especially when handling lipo, and even more when you do high voltage.
if you put two batteries in SERIES (connect PLUS of first battery to MINUS of second) then their voltage adds up, and Ah stays the same.
if you PARALLEL two batteries (connect PLUS of both batteries together, and do the same to MINUS), than you have a battery with the same voltage as a single one, but double the capacity.
you did not write about your setup. you say 8x 5000mAh lipo. and you say 20Ah.
this would equal to a 2s4p setup. 4 of those packs in parallel and then another pack 4 in parallel, in series with the first one.
this would give you 49,2V fully charged (if i assume 6 cell packs) and 20Ah.
but if those are 3 cell packs only, it could be a 4s2p setup, which equals 49,2V charged, but only 10Ah.
start reading a bit more, and then give us all info needed to answer your question

izeman said:

yes. way worse than basic you should start with some basic knowledge. especially when handling lipo, and even more when you do high voltage.
if you put two batteries in SERIES (connect PLUS of first battery to MINUS of second) then their voltage adds up, and Ah stays the same.
if you PARALLEL two batteries (connect PLUS of both batteries together, and do the same to MINUS), than you have a battery with the same voltage as a single one, but double the capacity.
you did not write about your setup. you say 8x 5000mAh lipo. and you say 20Ah.
this would equal to a 2s4p setup. 4 of those packs in parallel and then another pack 4 in parallel, in series with the first one.
this would give you 49,2V fully charged (if i assume 6 cell packs) and 20Ah.
but if those are 3 cell packs only, it could be a 4s2p setup, which equals 49,2V charged, but only 10Ah.
start reading a bit more, and then give us all info needed to answer your question

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yes they are 6s packs and i now understand series etc thanks.
a friend of mine wired all the packs for me and its all colour coded so i cant cock it up hence no fires and he set up the charger too.
all is slowly becoming clear.
many thanks for the help

The lvc of 44v on a 12s4p setup is storage voltage. or about 3.85 per cell. So you really want to go to at least 42lvc if you want any range. Going much lower will shortin the battery life. Also you might want to charge to 4.166 per cell or about 50v hot off the charger. Which is 25v per 6s pack.
that will give you much more of the rated AH of the battery.

i've been running 15s4p for the last 2 years, charging to 62.4v and shuting down at 52v. Last test last week showed 18.4Ah capacity after 2 years of use on a MAC 8t with 45a controller. Oh they are trinugys on one bike and Zippy's on my other.

So use the battery to it's potential if possible as they will degrade over time if not used too.

Dan

4p would be 4 packs paralleled. So for example you say you have 8. If you are running approximately 48v, you have 4p and 20 ah of battery. If you are running about 90v, you have a 10 ah pack with the same 8 packs.

I'm assuming for now, you have 4p 12s pack, made from 6s 5 ah packs. Four 6s, packs are paralleled. A 6s pack is 6 cells connected in series, about 22v. Your pack is 22v 20 ah, connected in series with another 22v 20 ah, for 44v 20 ah total.

Charging to 4.1v is costing you several ah of capacity. Then to get ALL of the remaining, 18 ah or so, you'd have to discharge all the way to the very bottom, below 3.5v. If you stop at 3.65v, you could still be leaving about 2 more ah in there. Doing so helps the battery last longer.

So start thinking in terms of 16-18 ah of actual capacity.

But if your 6s packs are smaller than 5000 mha (5 ah) each, then it's even smaller. There is also a possibility that the device you are using to measure your capacity is not calibrated.

All this assumes all your cells are perfect as well. One bad pack with low capacity will lower your total some more.

He mentioned charging in a shed where is very cold. Is that below 0 cold? they should not be charged in freezing temps.

Ok as long as the cells themselves have not chilled too much. Don't put a frozen cell on the charger. And don't expect much capacity either, if the cell spends it's wh heating itself up. The resistiance of the cell will be higher when really cold. That extra resistance will just cause the cell to heat up, then it will perk up. But some just got lost in the heating.

But yeah, I bet he sees a lot better capacity come spring. Cold is compounding his apparent low capacity. Because of this, it might be worth it to charge to 4.2v in the coldest months.

the shed is very cold at the mo due to weather.
i do not store the batteries in there to keep them from freezing.
i tried charging to 4.16 and got way better results,thanks you are all true gentlemen.
still crapping my pants as they are in my rucksack and dont want to crash and burn.

It will help in a crash, if you box em up somehow, then put them in the rucksack. I like to use old coroplast political signs to create tight fitting boxes to protect my lipo. Then I can carry them in pannier bags with less worries. But even plain cardboard can work fine.

dogman said:

It will help in a crash, if you box em up somehow, then put them in the rucksack. I like to use old coroplast political signs to create tight fitting boxes to protect my lipo. Then I can carry them in pannier bags with less worries. But even plain cardboard can work fine.

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cheers dogman ,i have plenty of correx sign boards as i make reflective stickers.will make one till i get aluminium case made for front triangle on the frame.
also having weight on my back tends to make the bike power wheelie up the steep hills i have to ride