Looking for Smart BMS options for 6S6P bank from Fiat 500e

kilkenny2 · Apr 10, 2018

I'm looking for suggestions on a BMS\PCB

I have 6 x Lithium 24v (6s-22.2v) batteries connected in parallel for my RV house battery bank.

1K solar array -10 panels x 100W

Battery (see photo)- Six x 22.2v Bosch/Samsung 64ah 6S batteries salvaged from a Fiat 500e connected in parallel.

Charge controller- OutBack Power FM60-150VDC FLEXMax 60 Charge Controller (configured for lithium)

Inverted - Samlex Sa-1500-124 Commercial Grade Pure Sine 24v 1500 Watt Power Inverter

My typical charge rate is around 24v+- 5-20A. My typical discharge I rarely exceeds 40A (pull from inverter maxes at 24V/1500W/60A )

Currently I have no BMS. I am charging the bank to 24.10v keeping cells about 85% (4.016v per cell). This has been working well for past year or so but having to periodically manually re-balance cells. I would like to install some sort of Smart Bluetooth BMS\PCB and looking for suggestions. I would like to have a digital monitor to log\monitor each of my 36 cells. Also I need them to be kept in balance automatically. Given the size of each cell I would think I need at least 100-200mv for balancing if not more. I am looking for a $300-400 solution. I have looked at commercial BMS like Orion but these are very pricey and seem like overkill.

Keep in mind these are all the same brand cells and should all have very similar specs and history. All seem healthy. Also being a house battery they tend to get drained\charged slowly vs. in a EV situation where there is a larger draw and fast charge.

Monstarr · Apr 11, 2018

kilkenny2 said:
I'm looking for suggestions on a BMS\PCB

I have 6 x Lithium 24v (6s-22.2v) batteries connected in parallel for my RV house battery bank.

1K solar array -10 panels x 100W

Battery (see photo)- Six x 22.2v Bosch/Samsung 64ah 6S batteries salvaged from a Fiat 500e connected in parallel.

Charge controller- OutBack Power FM60-150VDC FLEXMax 60 Charge Controller (configured for lithium)

Inverted - Samlex Sa-1500-124 Commercial Grade Pure Sine 24v 1500 Watt Power Inverter

My typical charge rate is around 24v+- 5-20A. My typical discharge I rarely exceeds 40A (pull from inverter maxes at 24V/1500W/60A )

Currently I have no BMS. I am charging the bank to 24.10v keeping cells about 85% (4.016v per cell). This has been working well for past year or so but having to periodically manually re-balance cells. I would like to install some sort of Smart Bluetooth BMS\PCB and looking for suggestions. I would like to have a digital monitor to log\monitor each of my 36 cells. Also I need them to be kept in balance automatically. Given the size of each cell I would think I need at least 100-200mv for balancing if not more. I am looking for a $300-400 solution. I have looked at commercial BMS like Orion but these are very pricey and seem like overkill.

Keep in mind these are all the same brand cells and should all have very similar specs and history. All seem healthy. Also being a house battery they tend to get drained\charged slowly vs. in a EV situation where there is a larger draw and fast charge.

When you look for a BMS solution for parallel operating batterypacks, I would think 1 BMS per series string for optimal protection. Parallel the - connection after the P- output so that the BMS is able to exclude that string from the whole battery.
You can also connect small balancers for balance operation only.

Check the FAQ on:
https://123electric.eu/products/123smartbms/
A similar answer you can find there.

kilkenny2 · Apr 11, 2018

Monstarr - thanks for suggestion. I have looked at the 123SmartBMS and the Batrium BMS. I am still unclear as to the exact configuration that would be required given my parallel setup. I have emailed both 123 and Batrium and waiting to hear back from them... I suspect those solutions will be $700-1000 which may be out of my price range but we'll see.

One thing I have considered is using six small hobby battery checkers mounted on a single panel (example ISDT BattGo BG-8S) and just leaving them connected with a disconnect switch on the negative lead. It would allow for a reliable and semi-attractive cell monitor. I doubt the balancer function would be able to do much since I'm guessing its only 50mv but I for $30 x 6 it a low cost cell monitor.

Monstarr · Apr 12, 2018

kilkenny2 said:
Monstarr - thanks for suggestion. I have looked at the 123SmartBMS and the Batrium BMS. I am still unclear as to the exact configuration that would be required given my parallel setup. I have emailed both 123 and Batrium and waiting to hear back from them... I suspect those solutions will be $700-1000 which may be out of my price range but we'll see.

One thing I have considered is using six small hobby battery checkers mounted on a single panel (example ISDT BattGo BG-8S) and just leaving them connected with a disconnect switch on the negative lead. It would allow for a reliable and semi-attractive cell monitor. I doubt the balancer function would be able to do much since I'm guessing its only 50mv but I for $30 x 6 it a low cost cell monitor.

At some time you tend to forget about the balance checking because the battery performed so well over the years. And then 1 cell runs bad, reverses polarity due to no lvc and your house burns down. :?
Over exaggerating perhaps but plausible. It is better not to save money on protection.

Parallel the cells before the series connection and you need only 1 BMS.

fechter · Apr 12, 2018

If you make parallel connections for each cell, not just the main +/- terminals, then you could use a single BMS to watch the entire pack.

kilkenny2 · Apr 13, 2018

fechter said:
If you make parallel connections for each cell, not just the main +/- terminals, then you could use a single BMS to watch the entire pack.

OH WOW I had not even though of that...ok thinking this through....

Two questions:
Does this drawing look correct? (I'm only showing 3 of 6 batteries in the diagram)
Based on the proposed config, can you think of any pitfalls to paralleling the cells between batteries? I realize one major drawback would be my inability to monitor each individual cell. Instead I would be monitoring the combined six cells in parallel.

Looking for Smart BMS options for 6S6P bank from Fiat 500e

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