I'm revisiting this project and redesigning it cope with a full twenty subpacks as I need to do something to speed up and automate my pack refurbishing for UK owners. Ron has a good setup running in the US but I need to try and help more over here as the cost of shipping packs and import duty etc is just horrendous.
As most IMA batteries I have worked on have required subpacks changing, then you may as well remove them all from the case first. This gives a number of advantages IMO which i'll elaborate on.
1) When cycling the packs will now be fully exposed and can be cooled more effciently.
2) Physical problems can be detected like a blown/leaky cell etc.
3) It is a lot safer as no high voltage pack to deal with.
4) It allows my new design to be utilised.
The new design will use a large wooden board as a building block. On it will be fixed a length of 90degree angled copper or aluminium drilled at intervals for 20 subpack bolts. This negative end of each subpack will be bolted to this - BUS. The postive end of each subpack will be bolted to small seperate sections of individual angled brackets. These will then attach to one side of an individual 70A 12v high power relay. The other side of all the 20 relays will again be attached to a common + BUS
A PWM controlled 0-50A load and charging source will be attached to the BUSES.
Each subpack can be selected at will via the relays.
The current flowing and voltage of the BUS will be measured. All the ptc strips will be connected in series using some simple crocodile clips on short lengths of wire to duplicate the OEM connections. The whole board will be covered with a clear plastic cover/enclosure with a fan to allow forced cooling air to be drawn over the subpacks. An enclosure temp sensor will also be fitted.
The 20 relays will be driven via the main board and controlled via a Picaxe chip driving a MAX6956 I2C I/O expander and ULN2003A driver IC's
The board will have a mini LCD display some simple buttons and will send data via USB to an attached netbook PC running excel, which will basically gather all the data the subpack cycler spits out.
It's early days again and I do have a few other things to sort out, but I have seen a bargain set of 25 x 12v 70A relays on e-bay in the UK which look ideal for this project.
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