LiFePo4 House Bank Using SmartHousePower BMS

[electric1]

Originally Posted by jlubimir

Electric1-

Have followed all the threads (here and on the DIY EV circuit) for several years.

I apologize to you and others who have tried to contact me in this thread and got no response. I abandoned this forum since the discussions were no longer constructive. Same trend is on other forums, you get a lot of armchair experts and a lot of wind blowing ( not in a good way as would be for this forum ).

In the meantime LiFePO4 market has been steadily growing, more suppliers, better known reputations, better quality controls, etc etc. Most DIY EV projects don't even mention Lead Acid anymore, everyone has accepted LiFePO4 as best choice for large capacity batteries IN MOST APPLICATIONS ( some exceptions exist ).

I applaud Paul for starting a new thread for practical discussions, I will try to be active there until it becomes counterproductive.

If you have any direct specific questions you want me to answer, please PM me since I am not allowed to post links to my own sites, or just Google CleanPowerAuto and you will find me.

[capn_billl]

About the OP's question about balancing the cells. 12volts nominal at 3 volts per cell is only 4 cells in series. It is not quite like other applications were you have up to 100 cells in series operating at full current capacity, (IE electric car). If the cells go out of balance, (less likely with matched sets), you will notice an imbalance in resting voltage after a full charge as the first symton, and reduced capacity as a second.

Charging as a set, and periodically monitoring individual cell voltage after charging, (and after discharging), will most likely give you plenty of advance warning that cells need to be rebalanced. And advantage you will not have with a SLA due to inability to get at individuals cells in a trojan, etc...

Other than smaller size and weight for same capacity, and slightly more care when charging, and discharging than Lead acid, (if you want to protect your investment)., there are really no disadvantages to Li compared to lead.

The only changes I noticed in switching to Li in portable power tools, and my laptop is much longer use times between charging, (and slightly more heat).

Two things I have heard from users of Thundersky batteries. 1. Sandwich batteries in a metal case to prevent swelling from heat as it can cause them to lose capacity and fail prematurely, (this was from an electric car owner that used them at 200amps or better).
2. Have forced air cooling in battery compartment, (also required for lead batteries in same application), see above.

[electric1]

Originally Posted by capn_billl

Two things I have heard from users of Thundersky batteries. 1. Sandwich batteries in a metal case to prevent swelling from heat as it can cause them to lose capacity and fail prematurely, (this was from an electric car owner that used them at 200amps or better).
2. Have forced air cooling in battery compartment, (also required for lead batteries in same application), see above.

Heat related concerns only apply to high C rate applications. House bank is a very low C rate application, so there are no heat concerns from the batteries. However, if ambient temps in the battery compartment can reach 50C or more, then forced cooling would be helpful for the battery.

Strapping to prevent swelling applies more to high C rate applications as well, but in any case I would recommend to constrain cells to prevent sagging on the large side over long time due to its own weight and thin plastic walls. Don't go crazy with strapping, you are not making a vise, just simple structural support and tight bounds.

[goboatingnow]

dont know if this has been linked before , but heres a good roundup of BMS producsts

Li-Ion BMS - Li-Ion BMS options

[McG]

Hi there. Just a quick update as promised: I've had my 800A/H 12v 4 cell Thundersky battery pack now for 18 months. I must say, it has been such a pleasure. No issues. We went overseas for 3 months. I set the Outback solar controller to not exceed 14.2V and switched off all accessories. So there were no draw from the pack. Got back, switched on the 12v compressor fridge and laptops etc. It is almost like being connected to the grid! I will never look back. During the middle of winter, I run a generator and power supply at 14.2v 100A/H to fill the pack once a week because the solar is insufficient in winter.

The BMS from Electric1 is working fine too!
Cheers for now.

[DeepFrz]

Thanks for the update.

[s/v Jedi]

Originally Posted by DeepFrz

Thanks for the update.

Will cost me money next time I need new batteries. And come up with a new way to hold them down somewhere again

[senormechanico]

Originally Posted by s/v Jedi

Will cost me money next time I need new batteries. And come up with a new way to hold them down somewhere again

If you haven't already gone "To The Dark Side", trust me. Do it and you will never look back !

Steve

[travelnodes]

Hello,

I'm new to this thread and I have an opportunity and an offer some of you may be interested in... I have a friend who purchased a pallet of used LifePo batteries. He foolishly cut off and threw away all of the BMS boards.

But the cells are still useable (i.e. they are holding a charge per my multimeter) I can buy them cheap and in large quantities. But I would offer some in trade to a skilled Electrical DIY person in exchange for a safe, tested and working array for use as house batteries.

In other words, I send you (or deliver to you) a large supply of LifePo cells clusters and you solder on all the BMS boards, etc. and keep some for yourself and give the rest back to me, ready to use.

If anyone is interested please direct message me or post questions here.

Joe