# Any experience with Battery Blocs?



## Hasufel (May 4, 2017)

I was starting to look into Li-ion battery packs (in the near term for UPS-type applications but eventually maybe for a Powerwall-type system) but I'm concerned about having to go through a lot of trouble resoldering packs if one cell goes bad. I saw something called Battery Blocs (batteryblocs.com) that seemed to be a good system for easily building and rebuilding battery packs without having to solder or spot weld. It's a little pricey at $1 per cell but otherwise seems ideal for my needs. Is anyone here familiar with this system and can speak to how well it works in real life? Thanks in advance...


----------



## woodgeek (May 5, 2017)

Ok.  I looked into Lithium for a Hobby-sized off grid Solar system I have (50W panel), when my 100 Ah flooded lead acid battery faded after 4 years of use...

I found this outfit selling biggish lithium packs in LiFePo: http://www.batteryspace.com/lifepo4batterypacks.aspx

I like the look of this stuff better than your site, since it seems to be bigger cells with screw connectors and commercially sourced battery boxes, rather than little cylindrical cells and custom machined (or 3-d printed?) parts.  While it might be possible to source the cylindrical cells for cheap, the whole soldering/spot welding connections sounds like a bad idea (frying the cells, or requiring specialized equipment and techniques). The battery-blocks run the current through a Neodym magnet for contact? Off-gridders have been building high power batteries (on lead-acid chemistries) using heavy cables, crimp lugs and screw connections for a LONG time and there is a wealth of info on the 'net about that stuff, and a lot of prefab cables and parts available.

You will want to read a LOT about Lithium chemistry....there are a number of different lithium battery chemistries in use, which have different durabiltiies, care and feeding habits, costs, and *tendency to burst into flames*.  The LiFePo chemistry is popular in that it has excellent cycle durability and very low flammability.  I believe it is what the Chinese EV makes like BYD use.  The downside is that it is slightly heavier and more expensive than some other Li chemistries.

My understanding is that the cylindrical cells (same as used by Tesla) are the MOST flammable.  Of course, fires start at cell manufacturing defects (like a shorted spacer from a small pinhole or piece of debris).  All the exploding macbooks and samsung phones come down to manufacturing precision...I would not want to go bottom feeding for the cheapest no-name brand cylindrical cells here!  Of course, one burning cell is not going to explode your house, but the problem is then one of packaging.  IF you pack hundreds of these cells together tightly, one cell can catch a neighbor and the whole bank can go up!  How does Tesla deal with this?  They space the cells out (costly from a pack density point of view) and fill the space with a special, solid, fire-retardant foam....and then test the heck out of it!  Good for them.  But would I get a TEsla's worth of cheapo cylindrical cells, dense pack them into a unventilated box, spend days soldering them together (and possible damaging them) and then run them in my house?  Not in a million years. Your insurance company might agree with me.

Lest you think I am down on Lithium and DIY...I own a 600 lb LiMnO battery in my LEAF, and have built my own 1.5 kW V2G system to use it to power my house during blackouts.

Digging into the engineering of these large Li packs, I learned about balancing.  All these packs are (of course) in parallel/series strings with high amperage cabling, but they also have this network of low current wiring to each cell, hooked up to a highly multiplexed controller that periodically rebalances the SOC on each cell!  In lead acid, this rebalancing is achieved by periodic overcharging of the entire bank....the highest SOC cells make a little hydrogen, while the lowest SOC cells come up to a full SOC.  This is not possible with Lithium...a high SOC cell must have a little extra charge taken off by a shunt.  Hobbyists describe walking through their bank a couple times a year with a multimeter and a power resistor draining higher voltage cells by hand.  Ugh.  Failure to rebalance will cause the bank to fail eventually...will that be after 2 years or 5 years...I don't know.

An automatic balancing solution is offered by my site above:
http://www.batteryspace.com/lifepo4...e-with-led-balancing---un38-3-passed-dgr.aspx
each cell gets its own microcircuit that shunts it when it gets to high SOC, with an indicator light.  Makes sense to me, but again, would favor using biggish individual cells, to minimize the cost/complexity of rebalancing circuits.

So, after many hours of geeky fun reading about this stuff, what did I do?  I decided that the cost was higher than I wanted, would have been a several hundred dollars to build out a 300-400 Wh LIFePo pack with rebalancing, that likely would have lasted for 10 years, of course.  I was tired of the clunky flooded lead acid.  I got a cheap AGM lead acid battery from amazon:   35Ah, 400 Wh, and I think it was $40-50 and it works with my existing solar controller and is auto-balancing.  Should last 5 years, at which point Li batteries should be a lot cheaper.

Have fun!


----------



## Hasufel (May 6, 2017)

woodgeek said:


> Ok.  I looked into Lithium for a Hobby-sized off grid Solar system I have (50W panel), when my 100 Ah flooded lead acid battery faded after 4 years of use...
> 
> I found this outfit selling biggish lithium packs in LiFePo: http://www.batteryspace.com/lifepo4batterypacks.aspx
> 
> ...


Thanks for the detailed reply! You've given me a lot to think about. I was aware of the safety issues with Li-ion batteries and shared your concern about welding or soldering them into packs, which is what prompted me to look for alternatives like the Battery Blocs I happened upon. You've gotten me to look seriously at LiFePO4 cells for the first time and I see some products that might meet my needs. The SLA replacements in particular caught my attention. They don't seem particularly cost effective, as you noted, but I've had bad luck with SLAs failing in my UPSs just when I need them the most. I might give one a try and see how it works out, and if it seems like a good long-term solution then I'll keep my fingers crossed and hope that the prices keep coming down!


----------



## woodgeek (May 6, 2017)

You got me thinking about this again, and I found these....

https://www.bioennopower.com/collections/12v-series-lifepo4-batteries

which are available online.  These guys have batteries intended as replacements for starting batteries which are very dear, and then the ones at the link that have lower peak amperes, and a somewhat more reasonable price (about 5X SLAs).  Many of them have built in BMS systems that prevent overcharging, overdischarging, over-current and which provide rebalancing.

For a stationary UPS type application, these seem to be overkill...weight is not an issue, nor is the ability to cycle a lot (the above are rated for 2000 deep cycles).  For an off-grid solar system, you could see them, maybe, if you knew you would use the extra cycles.

The most cost effective for a UPS app is likely still a big dumb lead acid, even a flooded cell, on a decent, temp-controlled float charger that won't electrolyze the water.  With no cycles in standby at reasonable temps....should last 5 years no problem...and then recycle them at WallyWorld every 5 years even if you never used em.  For the cost of the LiFePos, you can get 25-50 years of flooded cells in standby service, replaced every 5 years.

I guess after years of being skeptical, and seeing a lot of gel-cel SLAs fail with age, I have decided that AGMs are likely a much better technology.

The 'preppers' of course get 'dry' flooded cells, store them in nitrogen with a separate store of acid, and then voila...brand new, fully charged flooded cells when the demand shows up....but that is not what you are looking for either.


----------



## Hasufel (May 6, 2017)

woodgeek said:


> You got me thinking about this again, and I found these....
> 
> https://www.bioennopower.com/collections/12v-series-lifepo4-batteries
> 
> ...


That site has a wide range of options--thanks! Your points about relative costs make sense, but it occurs to me that the LiFePO4-based SLA replacements have at least one big advantage for UPS applications that we haven't talked about yet: increased capacity. I can replace the 12V 7Ah SLAs in my UPSs with a 10Ah LiFePo4 unit that's the same size. And if you factor in the better discharge characteristics of LiFePO4s, the replacement is about equivalent to a 12Ah SLA. So basically I can do a direct swap that increases my UPS's capacity by nearly 75%. Obviously that comes at a cost, but potentially there are circumstances under which that might be worth it.

One other interesting option I noticed is the big cylindrical LiFePO4 cells made by Headway. They come in 10Ah and 16Ah sizes and maybe even larger ones. They have built-in screw terminals that make connections easy, and their higher capacity would reduce the number of cells required and simplify the balancing.


----------

