General Battery Recharging Question

Thread Starter

djsfantasi

Joined Apr 11, 2010
6,716
I titled this “general” because the battery specifications are unknown

Is it possible to design a bus that can recharge ~2o battery packs in parallel?
How do I determine the total current and voltage requirements for s recharging bus? Is it possible to feed such a bus and have individual, local BMS at the location of the various battery packs?
 

MrAl

Joined Jun 17, 2014
7,757
Hi,

Do you mean two packs wired directly in parallel?

This is something i always did not like doing because you cant tell if one pack is not charging and the other is getting the full charge meant for two packs not just one. The best bet might be to charge at the level of one pack only.

I think my drill monitors all the battery cells individually. It's a very fast charge 30 minute charger but it's very specially built with multiple contacts on the pack.
It's that Makita brand.

A trick is to keep the packs separate with a small value resistor in series with each pack. It might take a little longer to charge but then you can monitor the current in each pack too.
 

Thread Starter

djsfantasi

Joined Apr 11, 2010
6,716
Actually, I am talking about 20 or more packs in parallel during recharging. After they are charged, they are 20+ individual battery packs.

I could just run a power bus to the 20+ systems and do away with the battery packs, but the whole point is to avoid power bus wiring. When the systems aren’t in use, temporary cabling can be used to recharge the battery packs and removed before they could be seen during operation.

The systems to be powered are various animated devices for entertainment. Power wires would break the illusion. Plus, some of the animated devices are free moving and can’t be tethered at any point.
 

MrAl

Joined Jun 17, 2014
7,757
Actually, I am talking about 20 or more packs in parallel during recharging. After they are charged, they are 20+ individual battery packs.

I could just run a power bus to the 20+ systems and do away with the battery packs, but the whole point is to avoid power bus wiring. When the systems aren’t in use, temporary cabling can be used to recharge the battery packs and removed before they could be seen during operation.

The systems to be powered are various animated devices for entertainment. Power wires would break the illusion. Plus, some of the animated devices are free moving and can’t be tethered at any point.
Well what current level would you use for that many in parallel?
 

TeeKay6

Joined Apr 20, 2019
572
Actually, I am talking about 20 or more packs in parallel during recharging. After they are charged, they are 20+ individual battery packs.

I could just run a power bus to the 20+ systems and do away with the battery packs, but the whole point is to avoid power bus wiring. When the systems aren’t in use, temporary cabling can be used to recharge the battery packs and removed before they could be seen during operation.

The systems to be powered are various animated devices for entertainment. Power wires would break the illusion. Plus, some of the animated devices are free moving and can’t be tethered at any point.
I agree with @MrAl; it is not wise to charge batteries in parallel. As a worst case, what if one of the 20 under charge is defective/shorted/whatever. Far better would be as MrAl suggests and at a minimum limit current into each battery via a separate resistor so that current and voltage of each can be monitored. The charging for all could be "in common" (i.e. a single power source for charging all) but the monitoring could be done one by one in a cycling process (i.e. multiplexed), e.g. checking each battery voltage/current once every minute. This is a very viable approach using CMOS multiplexers driven by a microcontroller.
 

ronv

Joined Nov 12, 2008
3,770
Actually, I am talking about 20 or more packs in parallel during recharging. After they are charged, they are 20+ individual battery packs.

I could just run a power bus to the 20+ systems and do away with the battery packs, but the whole point is to avoid power bus wiring. When the systems aren’t in use, temporary cabling can be used to recharge the battery packs and removed before they could be seen during operation.

The systems to be powered are various animated devices for entertainment. Power wires would break the illusion. Plus, some of the animated devices are free moving and can’t be tethered at any point.
Something like this?
https://www.maxamps.com/12-port-parallel-charge-board-jst-xh-jst-micro-losi?gclid=Cj0KCQjw1MXpBRDjARIsAHtdN-3RhOl5VKR3VFGvivQ06bJStMD6_LD05kNkPcbRDv7gUtMLIcxrLDYaAgpAEALw_wcB
 
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