Lifepo4 replacement quandary

BB. · August 2018

Bluesea has some latching relays upwards of 500 amps at 12 and 24 volts... May be expensive in the ~$250 USD range. These are designed to connect battery banks when charging--May need "hacking" for the disconnect function/control.

https://www.bluesea.com/products/category/35/Automatic_Charging_Relays

250 Amp latching solenoid:

https://www.bluesea.com/products/9012/L_Solenoid_-_12_24V_DC_250A

-Bill

Dave Angelini · August 2018

Cool might help someone. For my money, this needs to all be done and tested by the people who build the battery.

Dave · August 2018

karrak said:

Dave said:

nevermind my last post, i was reading up and this PMC really doesn't do the same job as a BMS.

I am puzzled, it looks like a BMS to me,does all the functions of a BMS
Monitors individual cell voltages and charging current
Will disconnect battery if cell voltages or charge/discharge current goes out of operational limits
Will keep the battery balanced.
I think it will also output this information to a computer but am not sure about this. Am I missing something?

Simon

I called Electric Car Parts (ECP) today but unfortunately I had not seen this post so I didn't ask these questions. But, here's some explanation:

The Protective Circuit Board management system (https://www.electriccarpartscompany.com/48V-512V-576V-Custom-Built-Lithium-LiFePO4-LFP-PCB-PCM) only had 70 mA available to balance so if there is much V discrepancy, it would take a very long time to correct. The battery balancer he recommended (https://www.electriccarpartscompany.com/3V-1S-Lithium-Lighted-Battery-Balancers) has 6 A to do the job.

The setup he recommends is a battery balancer for each cell (16 for me) and then a battery manager (https://www.electriccarpartscompany.com/48V-100A-EV-BMS-Battery-Management-System) for the system. The BMS would provide the disconnects and do large scale balancing of the bank.

Looking at ivor's earlier post it sounded like he was getting a battery bank for $2k (24V 400Ah as I recall) and that's a lot cheaper than it would cost thru ECP from what I could tell. That may apply to other components too. For some reason, I am nervous about ordering from Ali. For one thing, if there is a warranty issue, would you try to handle through them or the manufacturer? I suppose if you save enough on hte order, you could apply the savings to new components if that was easier than trying to get warranty coverage.

mcgivor · August 2018

The batteries arrived today, a week from order date, not bad.
@Dave said. For some reason, I am nervous about ordering from Ali. For one thing, if there is a warranty issue, would you try to handle through them or the manufacturer? I suppose if you save enough on hte order, you could apply the savings to new components if that was easier than trying to get warranty coverage
At first i was a little apprehensive about Alibaba, perhaps the Ali Baba thieves association

, but in reality they act as a go between offering protection to the buyer by holding funds from the seller until the transaction is complete and the customer is satisfied. When I imported cars from Japan to Canada I used a similar trade assurance company in Japan, as protection from shady operators. All my dealings so far with Alibaba have been positive.

karrak · August 2018

Dave said:

But, here's some explanation:
The Protective Circuit Board management system (https://www.electriccarpartscompany.com/48V-512V-576V-Custom-Built-Lithium-LiFePO4-LFP-PCB-PCM) only had 70 mA available to balance so if there is much V discrepancy, it would take a very long time to correct. The battery balancer he recommended (https://www.electriccarpartscompany.com/3V-1S-Lithium-Lighted-Battery-Balancers) has 6 A to do the job.
The setup he recommends is a battery balancer for each cell (16 for me) and then a battery manager (https://www.electriccarpartscompany.com/48V-100A-EV-BMS-Battery-Management-System) for the system. The BMS would provide the disconnects and do large scale balancing of the bank.

Looking at ivor's earlier post it sounded like he was getting a battery bank for $2k (24V 400Ah as I recall) and that's a lot cheaper than it would cost thru ECP from what I could tell. That may apply to other components too. For some reason, I am nervous about ordering from Ali. For one thing, if there is a warranty issue, would you try to handle through them or the manufacturer? I suppose if you save enough on hte order, you could apply the savings to new components if that was easier than trying to get warranty coverage.

If the cells are all reasonably balanced to start with the high rate 6A balancers will be unnecessary. From the pictures the 48V-100A-EV-BMS-Battery-Management-System looks like it has a balancing function but the balance current would probably be around 70mA as well. Doesn't look like you can connect it to the outside world and it doesn't have a display.

One function that a BMS should provide which is extremely useful is the SOC of the battery (battery fuel gauge).

As for ordering from Ali I have ordered many different things from different suppliers and have never had any problems. I think Ali will help you if the goods don't arrive, are DOA or not as advertised but you are probably on your own if things go pear shaped a few months down the track. I always do an Internet search on the supplier and the product to see how much feedback there has been. For Lithium batteries and BMSes I suggest you have a look at the Endless Spheres Forum

Simon

Lifepo4 replacement quandary

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