I don't know if that diode you described would be meaty enough as I'm no expert! I would ensure that it was a higher rating. They're only a few £s.
Well I take the advice of EEs - there's a guy called Tiberius on here that seems to know what he's talking about and I quote one of his posts (there's a few - you can search if you want):
Re: Re:How do I connect 2 LiFePO4 packs in Scooter?
Postby Tiberius » Sat May 22, 2010 7:32 am
Battboy wrote:I won't go any further on this. it is getting redundant a bit now. Like I said earlier, each person can decide for themselves......
DH
Well, let me try to help the OP, Snowryder, and anyone else reading.
It is quite possible to parallel battery packs, but you need a few precautions. If they are separate packs you can't just connect them directly together; you need some kind of reverse current protection, but its relatively simple to achieve that. You can connect them through a selector switch, or through reverse protection diodes. Some BMSs may have the equivalent of diode protection built in, but you need to check.
Where it gets difficult is if you want to also charge them with a common connection. Generally this is not possible unless you disconnect the discharge path from each battery pack first. So the simple solution is to have separate charging connectors. You then need multiple chargers or you have to move one charger from pack to pack.
With the above approach, you are treating them as separate packs. It works very well with removable packs, and you then have the choice of using one, the other or both, each time you go out
Another approach is to effectively combine the packs into one, keep them permanently connected, and charge and discharge them together. This is a bit more complex and a lot depends on the BMSs in the packs. Also, you can only do it with packs of the same chemistry. Despite some questioning, I just couldn't work out from Don Harmon (Battboy) whether this is what his system does. I learned stuff about lion tamers and army generals and their excellent regard for customers but not what LifeBatt's electronics actually does.
Forgive me Don, but a lot of the time it sounded as if you were talking about series combinations rather than parallel.
HTH,
Nick
Like I said it seems you can try it without and if identical batts at same charge level it'll be OK. The mod is so simple and batt BMS's expensive I can't see the problem with doing it.... but then I'm no EE so no point in me debating the issue! I was using batts of 2 differing Li chemistries so perhaps more important for me?
