From the thread:
http://www.pedelecs.co.uk/forum/threads/battery-advice-please.17548/#post-216573
I could see several pedelecers use lipo hardpacks such as this 4s 5Ah:
http://www.hobbyking.co.uk/hobbyking/store/__26801__Turnigy_5000mAh_4S1P_14_8v_20C_hardcase_pack_UK_Warehouse_.html?strSearch=4s hard
The more I read about lipos, it seems that apart from punctures (risk aleviated by the hard pack) and bad connections (coming from connect and disconnect at every charge), a big risk is that a battery in parallel gets damaged for any reason, damaging the rest of the batteries in the pack. Instead, if there is no parallel connection (only series) the risk diminishes a lot (eg a main fuse should be able to control that risk).
So, let me assume I have enough with 5Ah, so no parallel connection. Then, I select 12s, so I need a 3x connection in series.
Let me assume I build a 3x series harness, such as the following (just an example, this is for 2x series, 3x series harness is not available at HK, I believe):
http://www.hobbyking.com/hobbyking/store/__18604__HXT4mm_Battery_Harness_14AWG_for_2_Packs_in_Parallel.html?strSearch=parallel
using HXT 6mm:
http://www.hobbyking.com/hobbyking/store/__20353__HXT_6mm_Gold_Connector_w_Protector_10pcs_set_.html?strSearch=hxt
(a technician at HK has told me these bullets are the best connections, better than XT90 http://hobbyking.com/hobbyking/store/__25662__XT90_Battery_Harness_10AWG_for_2_Packs_in_Parallel.html, for example)
as well as:
http://www.hobbyking.com/hobbyking/store/__9677__Turnigy_Pure_Silicone_Wire_8AWG_1mtr_RED.html?strSearch=8awg
or
http://www.hobbyking.com/hobbyking/store/__9671__Turnigy_Pure_Silicone_Wire_10AWG_1mtr_RED.html?strSearch=10awg
So, if I build a 3x series harness, from the output point of view, I have created a "big 12s battery".
However, the balance wire presents a problem:
A 12s BMS has a balance wire plug with 12+1 pins (12s plus ground). In principle, this is plug and play with a big, expensive 12s lipo battery. However, if I consider a "synthetic" 12s battery built out of 3x 4s lipo batteries, each JST-XH of a 4s pack has 5 pins (4 + 1 ground). So in total 15 pins.
My question is then: is it possible to "connect" the three 4s JST-XH of the three 4s lipo batteries into a single male 12s JST-XH, which connects into the female 12s JST-XH of the BMS? can I share the three grounds, of the three batteries, into a single one, the single remaining pin of the BMS?
If this could be done, it would be relatively simple, no need to dismantle cables to charge, no spot welding, and cheap.
Mistakes / suggestions for improvement?
http://www.pedelecs.co.uk/forum/threads/battery-advice-please.17548/#post-216573
I could see several pedelecers use lipo hardpacks such as this 4s 5Ah:
http://www.hobbyking.co.uk/hobbyking/store/__26801__Turnigy_5000mAh_4S1P_14_8v_20C_hardcase_pack_UK_Warehouse_.html?strSearch=4s hard
The more I read about lipos, it seems that apart from punctures (risk aleviated by the hard pack) and bad connections (coming from connect and disconnect at every charge), a big risk is that a battery in parallel gets damaged for any reason, damaging the rest of the batteries in the pack. Instead, if there is no parallel connection (only series) the risk diminishes a lot (eg a main fuse should be able to control that risk).
So, let me assume I have enough with 5Ah, so no parallel connection. Then, I select 12s, so I need a 3x connection in series.
Let me assume I build a 3x series harness, such as the following (just an example, this is for 2x series, 3x series harness is not available at HK, I believe):
http://www.hobbyking.com/hobbyking/store/__18604__HXT4mm_Battery_Harness_14AWG_for_2_Packs_in_Parallel.html?strSearch=parallel
using HXT 6mm:
http://www.hobbyking.com/hobbyking/store/__20353__HXT_6mm_Gold_Connector_w_Protector_10pcs_set_.html?strSearch=hxt
(a technician at HK has told me these bullets are the best connections, better than XT90 http://hobbyking.com/hobbyking/store/__25662__XT90_Battery_Harness_10AWG_for_2_Packs_in_Parallel.html, for example)
as well as:
http://www.hobbyking.com/hobbyking/store/__9677__Turnigy_Pure_Silicone_Wire_8AWG_1mtr_RED.html?strSearch=8awg
or
http://www.hobbyking.com/hobbyking/store/__9671__Turnigy_Pure_Silicone_Wire_10AWG_1mtr_RED.html?strSearch=10awg
So, if I build a 3x series harness, from the output point of view, I have created a "big 12s battery".
However, the balance wire presents a problem:
A 12s BMS has a balance wire plug with 12+1 pins (12s plus ground). In principle, this is plug and play with a big, expensive 12s lipo battery. However, if I consider a "synthetic" 12s battery built out of 3x 4s lipo batteries, each JST-XH of a 4s pack has 5 pins (4 + 1 ground). So in total 15 pins.
My question is then: is it possible to "connect" the three 4s JST-XH of the three 4s lipo batteries into a single male 12s JST-XH, which connects into the female 12s JST-XH of the BMS? can I share the three grounds, of the three batteries, into a single one, the single remaining pin of the BMS?
If this could be done, it would be relatively simple, no need to dismantle cables to charge, no spot welding, and cheap.
Mistakes / suggestions for improvement?