Lithium battery BMS questions

[TurnNBurn]

I guess my only problem with the DIY arduino route is there's no clear instructions for it. Its not a kit. Its buy a bunch of parts and learn something new that I'm not sure I'm up to (without step by step instructions)

And I like the celllog setup, except I'd need three. And what benefit would that provide? I can see the voltages and all, but ideally I'd like it to integrate with the charger. More DIY work with no instructions.

As for my budget, I was expecting to spend $200 or so on a BMS. Could always pay more depending on features.

[P-hack]

the celllogs have an output signal when any cells are too low or high. what model number/make charger do you have, id like to see what bms hooks it has.

[TurnNBurn]

Originally Posted by P-hack

the celllogs have an output signal when any cells are too low or high. what model number/make charger do you have, id like to see what bms hooks it has.

The charger I'm looking at is:

1500W 1.5kW 12V, 24V, 36V, 48V, 60V, 72V Output 1500W 1.5kW LiFePO4 Li-Po Lithium Battery Charger 1500W 1.5kW Lead-Acid Battery Charger 1500

OR

900W 12V, 24V, 36V, 48V, 60V, 72V Output 900W LiFePO4 Li-Po Lithium Battery Charger 900W Lead-Acid Battery Charger 900W LiMn2O4 Battery Char


OR

9V 12V 24V 30V 48V 60V 72V 96V 120V 144V 1200W 1.2kW Lithium LiFePO4 LiFeyPO4 Li-ion LiPo Li-Mn Lead-Acid AGM GEL Silicon Battery Charger

I was looking at the Elcon PFC 1500 or 2500 which have cut-offs for charging. But those are pricey, unless I can find them for a reasonable price. All of these have cut-offs for charging. So is a BMS really required? Or do you guy recommend the BMS to monitor as I ride?

[P-hack]

k, I shot them an email asking how a bms can interface with their chargers. You didn't happen to see an online manual for them perchance?

worst case you add a ~20 dollar solid state relay to shut off the charger.

[TurnNBurn]

Originally Posted by P-hack

k, I shot them an email asking how a bms can interface with their chargers. You didn't happen to see an online manual for them perchance?

worst case you add a ~20 dollar solid state relay to shut off the charger.

I googled a while and couldn't find a manual anywhere.Why would I need a relay when these chargers include a cutoff?

[Daox]

You want to give the BMS a way to turn the chargers off if it starts overcharging a cell. Otherwise, you can and probably will run into either dead cells, or worse. For me, I had my BMS disconnected once. I overcharged two cells and one literally overheated and shot part of the battery through my rear windshield. This is the kind of stuff that can happen if you don't properly control things.

Since the BMS monitors every cell, its going to be way smarter than the charger, which only sees the total voltage of the entire pack. So, you really want the BMS to be able to control the charger.

[TurnNBurn]

Originally Posted by Daox

You want to give the BMS a way to turn the chargers off if it starts overcharging a cell. Otherwise, you can and probably will run into either dead cells, or worse. For me, I had my BMS disconnected once. I overcharged two cells and one literally overheated and shot part of the battery through my rear windshield. This is the kind of stuff that can happen if you don't properly control things.

Since the BMS monitors every cell, its going to be way smarter than the charger, which only sees the total voltage of the entire pack. So, you really want the BMS to be able to control the charger.

Ok. That explains it. I didn't know the charger only does the full pack. When I see some chargers they ask how many cells, what chemistry, things like that and I assumed this was because they auto detect each individual cell voltage.

[TomCat60]

I am researching for the best BMS right now myself. I am haven't decided what BMS I will use yet but maybe this guy can help you? I can't post a link yet because I am new to this forum. So Google Housepower BMS and there are vehicle rv and boat systems there too.

Tommy

[P-hack]

Yah that is the same setup as minibms, high cost per cell and endboards, cell boards only report over/under voltage, built for different battery chemistry.

[TurnNBurn]

Originally Posted by P-hack

Yah that is the same setup as minibms, high cost per cell and endboards, cell boards only report over/under voltage, built for different battery chemistry.

yeah, I saw that. Looks just like miniBMS. Same cost.

I was looking at more celllog mods to see if there's any instructions or projects for charging cutoffs. I still cannot find anything. I e-mailed a few vendors about chargers to get more information. I have not heard back yet.