[84bertone]

Have a 96volt lithium pack. Bottom balanced. No BMS. What would be the simplest, most cost effective (meaning cheap), way to monitor output from pack to know when I have reached bottom limit?

I like the Victron monitor using a shunt, but it only reads to 90volts.

 

[john61ct]

LFP?

2.81Vpc isn't too low for you is it?

Yes would be nice if that were the bottom-most failsafe withe a higher primary LVD, but I thought EV regularly goes that low. . .

 

[84bertone]

Yes. LFP. And no 2.81 would not be too low.

So........maybe the 90vdc Victron would work. Not sure how it would react at the high end.

 

[john61ct]

Nothing says you need one device to do it all.

 

[Ivansgarage]

Simple Answer JDL404 really great meter 69 bucks for meter 40 bucks for shunt
http://www.evwest.com/catalog/product_info.php?products_id=162

Here is a write up from Jack EVTV
http://store.evtv.me/proddetail.php?prod=JLD404AH

Here is the manual for the JDL404
http://media3.evtv.me/JLD404AH.pdf

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[dcb]

but you do need at least two voltage monitors to get a first order (extremely coarse) balance monitor.

edit apparently the jld404 isn't isolated either, so you would need two of them and two isolated dc-dc. or you can reference both to ground but that will create an imbalance over time with the lower pack half having 2x the leakage current.

http://www.electricsubaru.com/fuelGauge.html

 

[john61ct]

The extra circuit on the BMV-702 can be used as a rough "mid-string" balance monitor.

Or just use cell-logs?

 

[john61ct]

JDL404 really great meter 69 bucks for meter, 40 bucks for shunt

The documentation really needs an overhaul by a professional tech writer for that unit to be usable by laymen.

And the Chinese-cr^p hardware sourcing does not inspire confidence, do they really hold up over time? I'm not saying quality gear can't be produced in China, but in my experience it only happens when the foreign customer builds in and takes charge of monitoring stringent QA requirements, e.g. as with Apple

Victron is Dutch engineered, designed to last for decades in a harsh marine environment, and a lot more "user friendly", including good docs. And yes, why it costs over double the price.

 

[Ziggythewiz]

jld404 is isolated. I've had 2 in my car forever.

It's really overkill for just voltage monitoring though. You can get up to 4 digit meters for 5 or 10 bucks and same for each isolated power supply.