LiFePO4 charging and BMS question - can someone explain?

[sixty_cycle_hum]

Howdy folks.

I really enjoyed my bike this last summer, but now it's too cold to ride any real distance here in Michigan, and my mind is wandering of what to do with my battery pack in the off-season. Instead of letting it sit and go unused and forgotten about, I've decided that it's a great emergency power source. It's a Goldenmotor 15Ah 16S LiFePO4 pack (actually just uses headway cells - not sure about who makes the BMS just yet, but I'll get to that)

To continue, I've already bought this really great power inverter to hook up to it. It's a really slick COTEK 48VDC > 120VAC Pure Sine inverter. http://www.cotek.com.tw/upload/PDF/S600.pdf It absolutely rocks. It's even got enough guts to run my refrigerator. The sine wave looks perfect on a scope.

So far, it's all well and good. As long as I have a charged battery, I have a really slick and /silent/ auxiliary power source that can run almost any load that's necessary. Well, what happens when I need to charge with no AC mains available (maybe take it car camping or use it during a power failure). Solar comes to mind, but most reasonably priced charge controllers don't work at 48V, much less the actual 60V or so to charge LiFePO4 properly. Also, a PV array that is 48V is far more expensive than one or two lower voltage panels (at least twice the cost).

That brings me to the idea of using a DC-DC boost converter like this one to get 60V or so from a 12V or 24V PV panel. http://www.ebay.com/itm/Boost-DC-DC-Converter-Power-Supply-Step-up-Module-10V-60V-to-12V-80V-600W-10A-/221302058197?pt=LH_DefaultDomain_0&hash=item3386a16cd5

My question is this: How smart does my "charger" need to be? If I set the voltage output of the DC-DC converter to 58V or so, is my BMS smart enough to take care of the rest (assuming I plug into the charge leads, not the load leads). Also, the DC-DC converter is capable of limiting current.

Here's the number on my BMS board: PCM-L24S60-622(B) - the info I find about it tells me it is for 24S, but it is obviously modified or another version.

For the TLDR people: Is my BMS smart enough to take care of charging from a constant voltage source, also... can I simultaneously draw a load from the load leads of the battery while it charges without major badness?

 

[dnmun]

you can charge at any voltage you wanna. even 60V directly from the panels if you only have that. the battery will build up charge and as the voltage of the pack gets close to final voltage then one of the cells will hit the HVC and shut off the charging. but it will balance if you can get the voltage to about 58.4V and hold it there while the balancing current fills the low cells so the battery would be balanced.

 

[sixty_cycle_hum]

Thanks dnmun. So the little fan in my charger is shutting off because the load went down so low after the BMS went to balance mode at 58.4V?

How about drawing a load from the battery (like into the power inverter), while simultaneously charging at the charge leads? I'm failing to understand exactly what the BMS is doing in its different modes. Is there a good diagram around that would be similar to my BMS? I have a pretty good grasp of electronics, but I don't know the whole story of the different types and approaches of BMS design. Sorry if this has been discussed a million times before, but I really want to understand it all so I don't make s dumb mistake.

 

[dogman dan]

I don't see why you cannot charge while simultaneously discharging. If discharge exceeds charging too much, the bms will shut off the discharge.