lipo

josh · Post by **josh** » Sun Sep 24, 2006 12:18 pm

hi

ive got a 160 mah lipo in merge which i have been using since aws20, it was fine at aws20 but now it seems to run down quickly in 30 secs it will run great for 10 seconds and then gradually get slower and slower and im not sure what is causing it. any ideas?

thanks

Post by **BeligerAnt** » Sun Sep 24, 2006 7:45 pm

Hi Josh

Lithium batteries should be OK for about 500 charge/discharge cycles, but there are many things that can seriously shorten their life. It does sound like you have a dead battery (or at least one cell in the pack) which is no longer holding its charge properly.

Recharging batteries whilst hot is not recommended. They usually do get pretty warm in use, so it's best to let them cool down a bit before charging.

NiCd batteries should be fully discharged before recharging. As far as I understand it lithium batteries do not suffer from this problem.

Lithium batteries do need to be charged properly. Due to the chemistry involved, it takes at least 1hr to charge a lithium battery. In fact it takes about 4hrs to do a proper charge cycle, but it's about 95% done after 1hr.

Charging is a 2-stage process. Some chargers appear to only do the first stage. I don't know what the effects of repeated charging using a simple charger might be.

Lithium batteries do not like being over-discharged. Mobile phones etc have circuits built into the battery packs to automatically disconnect them before the voltage gets too low. Our battery packs do not have this feature. A lithium cell should not go below 2.5V, so for a 2-cell pack (7.4V) this means 5V. Unfortunately most ants will still run OK on 5V so it's hard to tell when the battery is flat.

Josh, it sounds like your battery pack has failed in some way. It should last longer than a couple of months, so maybe it has suffered some sort of accident. A brief short-circuit could cause a high internal temperature leading to partial failure. Over-discharge is another possibility.

If you can measure the voltage across each cell individually it may give you a clue. If one is a different voltage to the rest then that cell is probably dead. You may need to measure the voltage with a load to get the right result.
You could compare the performance of the battery with a known good one on a simple load like a motor, but be careful not to over-discharge the battery!

HTH

josh · Post by **josh** » Mon Sep 25, 2006 6:14 am

ok i was speaking to joacim and he reakons that maybe the 160mah lipo(these were cheap ones from japan) isnt up to drivin the sozbotboard and 4 sanyo look alikes and maybe i need a higher capacity battery coz i had a lipo fail after rrc in merge as well.

were do people buy lipos now indoor flyer only stock 130mah and below?

peterwaller · Post by **peterwaller** » Tue Sep 26, 2006 8:50 am

I buy mine direct from China but you need to buy enough to overcome transport costs. If you want some from this country Robotbirds at http://robotbirds.com/catalog/index.php?cPath=63_64 have a good selection 145, 250, 300, 360, 450mah. I have started using 250mah packs in both Mutant and Antrax and they seem fine. I notice that the robotbird 250mah are only 7.5C so I wouldn't recomend them as the ones I use from China are 15C and 20C burst.

josh · Post by **josh** » Tue Sep 26, 2006 2:34 pm

pete wereabouts do u buy in china? have they got a website?

peterwaller · Post by **peterwaller** » Tue Sep 26, 2006 6:16 pm

I get them from a company called Himodel and their website is
http://www.himodel.com/
Their prices are really good but you do have to pay about $8-10 for postage, wait 2-4 weeks and of course you may get caught for VAT and or import duty. They have a slightly strange way of working you go onto their site and order the bits. They then send you a confirmation email with the exact delivery costs added and you then pay through PayPal to confirm the order. I actually bought 4 spare 2 cell 250mah packs on my last order so if you are desperate I could let you have 1 or 2 at say 9 pounds each.

josh · Post by **josh** » Wed Sep 27, 2006 6:10 am

can u bring them along on sat and if the whole thing goes kaput ill give u 10 pound for 1

Post by **petec** » Sat Oct 14, 2006 6:14 pm

Interested to know where people are buying Lipos from and what types they are buying. Indoor flyer has changed hands and doesn't seem to have the Kokam cells anymore.

josh · Post by **josh** » Sat Oct 14, 2006 7:35 pm

www.robotbirds.co.uk sell the same ones as people used to buy from indoor flyer also i have been buying from a japanese modelshop ho sell thro ebay http://cgi.ebay.co.uk/Lipo-5-X-3-7V-160 ... dZViewItem which are good

Simon Windisch · Post by **Simon Windisch** » Sat Oct 14, 2006 9:06 pm

I've just bought two of these http://www.eurobatteries.com/sitepages/ ... d%20Models. At ?5.85 for 7.4v 260mAh they're the cheapest I've come across. I haven't plugged one in yet though...

Simon