TomC4306
Solar Obsessive
HUH?
Parallel.
If you're trying to sound like a know-it-all at least try to know it all.
Drop-in car battery DIY?
- Thread starter danroonie
- Start date
Parallel.
If you're trying to sound like a know-it-all at least try to know it all.
Sean Very North
New Member
Fets in series with the current flow, it's multiples of parallel FETs that dictate the amount of current they'll pass.... if you're wanting to score cheap points then crack on there.
TomC4306
Solar Obsessive
Hmm. Interesting. I guess as opposed to perpendicular?
Cheap point? No.
I already know who you are.
That guy.
Sean Very North
New Member
Great, I'm happy for you.
sunshine_eggo
Victron's little biatch
Your description is correct. It effectively treats two batteries arranged in 16S2P as 2P16S.
BMS control of the system means there can be layers of response. A runner doesn't shut down the entire bank. It simply stops charging analogous to a BMS that prohibits charging without the actual cut-off. The charger never sees the load removed. It simply receives instructions to charge at 0A. Critical levels can be defined that do actually open a relay to cut off the battery entirely, but there is ample opportunity to avoid that.
With 0.5A of passive balancing, runners are rarely a problem.
I would also assert that the Batrium is a poor choice for LFP. It does not support float charging as a concept. One can overcome this, but it is a nuisance and requires iterative customization to find the right solution for the system.
@Sean Very North,
This debate is context specific - having been on this site for a bit, I would assert that 90%+ of users on this site use a FET based BMS with no inverter communication, 9 percent using AiO/Server Rack Battery communication and 1% or less use Batrium or REC; therefore, the default advise is to NEVER rely on the BMS for routine charge termination and treat it PURELY as a safety device.
The concept doesn't even apply to AiO/rack batteries, Batrium or REC as those BMS are actually in control of the hardware.
Sean Very North
New Member
I'm not disagreeing, my opinion is that many folks aren't aware of what a quality BMS can provide in terms of control, data and stability, I disagree with the "default advice" but I'm long enough in the tooth to recognise that folks seem to enjoy doing what the off grid garage chap seems to do so I'm not intending pointing out the futility of playing lucky dip with random components.
400bird
Solar Wizard
So here's the thing, it sounds like you are saying that using a communicating BMS to control the charger/inverter is your preference. (This is a fine strategy)
But, as already stated, most BMS's don't do that. So, everyone is hearing you recommend using a FET based BMS to control charge/discharge by opening the FETs to stop current flow. (This is a bad strategy)
I hope now you can see why you're getting the push back on your opinion.
sunshine_eggo
Victron's little biatch
Few are willing to spend more on the BMS than they are on the battery. Most pursuing DIY are cost driven.
Commercial batteries are sold with FET based BMSs. Would you encourage everyone who buys one to charge to 16V because the BMS will protect the cells at ~3.65, or would you encourage users to program their chargers in accordance with the manufacturer's specifications?
Answers are influenced by the audience asking the questions.
You're a Batrium/Victron Elitist... as am I. I think the difference is that I can read the room. You either can't or aren't willing to accept that there is more than one solution besides the one you have chosen.
Sean Very North
New Member
You've either deliberately, or accidently misunderstood my opinion, I'm certainly not recommending a "BMS" that feature FETs passing the full battery current.
I'll acknowledge that the majority of folks here seem to prefer components, often called battery managements systems, that have an ability to pass current to/from a battery, and stop/start that flow if it detects a cell issue.
I believe they have been somewhat blinded, by the generally poor reliability, features and compatability of these cheap devices, to the advantages of a quality BMS, that has full control of the entire ESS, which is what the likes of a RECC or Batrium will do when combined with a Venus device, it just works.
400bird
Solar Wizard
I'm pretty sure I understand.
You are staying this, right?
If so, I agree and you are correct. (Assuming a quality BMS)
The rest of my post was just pointing out that is not what people are hearing.
Sean Very North
New Member
Nope, not a Batrium/Elitist at all, we've used a lot of quality equipment over the years, SMA, Schneider could equally have been added to a list of preferred manufacturers that are well proven.
sunshine_eggo
Victron's little biatch
You'll find a few threads of Batrium users here who are dealing with serious issues, Core's locking up, needing to be rebooted, poor support outcomes, etc.
Batrium is a strong product, but IMHO, you're screwed if you need support. I've had two support issues. One I had to figure out for myself, and you should have as well as the Batrium instructions for Victron interface is absolutely incorrect. The second remains unresolved, admitted to be a firmware issue with zero commitment to fixing it on the WM5 and only tentative commitment to fix it on the Core product.
Noted that you ignore relevant questions and only engage in using top tier hardware, spend far more than the vast majority, and have no reasonable perspective on helping those asking the questions. I'll re-label you as a top-tier elitist.
Read the room.
Sean Very North
New Member
These days people "hear" whatever they want to "hear", what was actually said doesn't seem to matter.
sunshine_eggo
Victron's little biatch
You epitomize this behavior.
Sean Very North
New Member
As i've previously stated, in the early days the miniscule husband, wife and a couple of mates company that was Batrium was selling products designed for folks who know what they were doing, we didn't really need their help, but their general response, or lack of it, when we pointed out documentation and firmware errors, such as their Eltek implementation wasn't ideal, but given they were drowning in trying to support folks who very obviously expecting to string a few cells together, plug in the cheapest AIO and bingo instant ESS we didn't really mind as the instant response we got from RECC when asking for custom compatibility was perfect, which is why they got lots of business, but like an old car I'm quite happy with the Batrium systems still running.
I'm not sure that labelling me simply for buying quality equipment is of any value, buy cheap buy thrice ..... but I guess some folks don't value their time.
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Sean Very North
New Member
In your opinion ....
How about we get back to the topic of the post that started the thread?
Vigo
Solar Wizard
In order to change the battery of a stop-start vehicle in any way you first need to know what the vehicle is monitoring and what it expects to see. As far as i know, basically all stop-start vehicles use shunts or current sensors at or near the battery terminals to watch power in and out of the battery. From this we can easily infer that the vehicle expects to see certain correlations between current and voltage signals based on what it thinks a stock battery should do. This in addition to other signals like HVAC request and engine coolant temp etc, is how it determines whether auto stop-start should be allowed or disallowed, whether the system is in a fault mode due to poor battery state of health, whether to restrict other electrical loads to preserve battery energy, etc.
Unfortunately, even factory service information usually won’t go into full detail on this stuff and will only give you enough to be able to fix it (if it has broken in a normal/predictable way..) but not necessarily enough to modify it and stay within the lines to avoid faulting out (ie trick it into working in an unintended fashion). There are LOTS of stories about dealerships unable to resolve stop-start issues, and im not saying every single one of them has a real badass on staff but it lends credence to the idea that even having access to all factory service information very well may not be enough.
Obviously if you put a smaller battery into a stop-start vehicle it would appear similarly to a stock battery that is somewhat degraded, but what happens if you install one with a higher resting voltage, totally different peukert factor, and higher capacity? The system may not recognize those conditions as poor or suboptimal and fault out for THAT reason, but that’s not the only possibility.. almost all monitored circuits or systems have ‘windows’ of acceptable signal range, outside of which the sensor/circuit is assumed to be reading inaccurately and thus the system takes some kind of action, usually: storing a trouble code, giving the driver a warning, and disabling/limiting some functions. Lots of signals are also cross-referenced against other signals when those signals should change in some kind of predictable relationship to each other. ‘Checking plausibility’.
So, what im saying is dont spend a bunch of money installing a different starter battery in a stop start vehicle unless you’re ok making it a new hobby of reverse-engineering some poorly documented programming, OR you have seen someone else do the exact same thing on the exact same vehicle and have it work. Theres a pretty good chance a car will react to a ‘better’ battery by giving you some ‘signal out of range’ or ‘signal implausibility’ errors and refusing to work. ?
Unfortunately, even factory service information usually won’t go into full detail on this stuff and will only give you enough to be able to fix it (if it has broken in a normal/predictable way..) but not necessarily enough to modify it and stay within the lines to avoid faulting out (ie trick it into working in an unintended fashion). There are LOTS of stories about dealerships unable to resolve stop-start issues, and im not saying every single one of them has a real badass on staff but it lends credence to the idea that even having access to all factory service information very well may not be enough.
Obviously if you put a smaller battery into a stop-start vehicle it would appear similarly to a stock battery that is somewhat degraded, but what happens if you install one with a higher resting voltage, totally different peukert factor, and higher capacity? The system may not recognize those conditions as poor or suboptimal and fault out for THAT reason, but that’s not the only possibility.. almost all monitored circuits or systems have ‘windows’ of acceptable signal range, outside of which the sensor/circuit is assumed to be reading inaccurately and thus the system takes some kind of action, usually: storing a trouble code, giving the driver a warning, and disabling/limiting some functions. Lots of signals are also cross-referenced against other signals when those signals should change in some kind of predictable relationship to each other. ‘Checking plausibility’.
So, what im saying is dont spend a bunch of money installing a different starter battery in a stop start vehicle unless you’re ok making it a new hobby of reverse-engineering some poorly documented programming, OR you have seen someone else do the exact same thing on the exact same vehicle and have it work. Theres a pretty good chance a car will react to a ‘better’ battery by giving you some ‘signal out of range’ or ‘signal implausibility’ errors and refusing to work. ?
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