biggoolies
Adventurer
I have the older model. I don’t think the older model does this
New DC to DC Charger From Renogy-20 amps or 40 amps-Flooded/AGM/GEL/Lithium
- Thread starter continuecrushing
- Start date
IMO BMS is just backup protection of the bank for when the primary devices fail.
The entire point of a DCDC charger is proper regulation. If a cheaper unit matches your existing bank, great use it, but batteries are consumables, personally I don't want to have to replace infrastructure if I want a different chemistry in future.
I acknowledge many don't care that much about precision with such issues.
The entire point of a DCDC charger is proper regulation. If a cheaper unit matches your existing bank, great use it, but batteries are consumables, personally I don't want to have to replace infrastructure if I want a different chemistry in future.
I acknowledge many don't care that much about precision with such issues.
hour
Observer
Thanks for posting this, though I don't quite know how to interpret or conclude if this product will be a viable solution for me. I'm going to run without a BMS, instead using an active balance board paired with a Victron battery protect (cells are bottom balanced and have practically no variation all the way until completely dead) and an overvoltage relay. My wonkiest cell hits 3.57v when others are high 3.4's. That said, I should be able to safely run things if I just limit my charge voltage to something like 13.8 - even significantly lower would be suitable in my testing running fridge in living room.
I could probably omit the balance board from the equation with the other two components and applying my findings to the settings of each device, but it's already on the boat from China.
A BMS is a collection of functionality to protect the bank.
Just buying a product that claims to do it all for you
vs putting together a collection of devices yourself,
is not fundamentally different.
Any links to detailed specs or experience reports?
Just buying a product that claims to do it all for you
vs putting together a collection of devices yourself,
is not fundamentally different.
What made you choose this unit?
Any links to detailed specs or experience reports?
hour
Observer
Someone else on here - his inspiring reply: jonyjoe101
If I could have found an active balance bms all-in-one board I would have gone with that, but his linked post (and his other post on secondlifestorage) made me think I should order one and give a try. My 90ah 3.2v x 4 cells are like a decade old (thanks eBay) and while they all discharge in harmony now, one shoots up much higher in the last 25% of charging. I'd be fine with just charging up until (below) the point that the one cell starts to soar but this could work. I think the max balance current is 10 amps peak, which is about a trillion times higher than any other BMS I found - and it does it at all charge levels.
I keep reading about active balancing becoming more popular but I can't for the life of me find anything to buy other than the QNBBM that I linked. Detailed specs are in the link from Aliexpress in my post a couple above, if you scroll down on the listing. If you know of other active balancers please link, since I have other battery packs in progress that I could use them on - especially if they do more than just balance like the one I bought.
Yes that sounds great as a balancing board concept, again would appreciate any more details, where did you see that 10A balancing rate?
I don't see anything specific in the Ali listing?
Another approach is charging with a balancing charger, perhaps only occasionally as a maintenance procedure.
I don't see anything specific in the Ali listing?
Another approach is charging with a balancing charger, perhaps only occasionally as a maintenance procedure.
hour
Observer
Seems like deligreen (mfg)'s website is borked temporarily and asking for a username/password when trying to hit the domain. Wasn't like that the other day. But "QNBBM balane specs" on google returns a couple other places with specs. Guess it's 6a continuous for sure, and a site or two claiming 10a peak.
I do wonder what happens though if I'm charging at say... 20 amps... and my one cell is trying to exceed 3.6v when the other three are sitting at 3.45 or something. Maybe that will never happen since it's balancing all the time, but it's something I observe on my ISDT Q6 Pro 14-amp balance charger even when charging at 5 amps. The ISDT only balances when charging is complete though. However, in the scenario I mention (if it were even possible while actively balancing), I wonder if that 20 amps is still going to be beelining for my wonky cell, and be too much for the QNBBM to distribute to the others.
So yeah, I do have the hobby balance charger and thought about using that for periodic maintenance, but as user jonyjoe101 describes in that post I linked (he also owns this charger), it drops charge current wayyy down when things start getting imbalanced. Like I've seen it take hours to pump in another 0.5 amp hours and declare itself 'done' - only it never truly charges each cell. Then it does it's automated balance portion which never finishes, and never gets them anywhere close. Odd though the second I put a load on the pack, they all reach the same exact voltage (like to the third decimal) in a minute, and ride down to dead in harmony.
Hell, I might have three wonky cells and one good one, I don't know. I'll be sure to post impressions once the balancer arrives on the slow boat from China.
What is your logic in going past 3.45Vpc in the first place?
If you're trying to cram that last 2-4% of usable capacity in there, then again I ask, why?
The way that "balancing charger" is designed, to start that ridiculously low current bleeding routine, only after hitting a high voltage that causes imbalance and premature wear, forcing the bank to sit at that voltage for crazy stupid long periods, is just nuts.
Forget it, just use it to bulk charge to your healthier (lower voltage, shorter CV stage if any) definition of 100% Full.
What is its C-rate for your bank?
hour
Observer
I don't know, those were just numbers to try and illustrate the spread I observe between one cell and the three others when trying to fully charge on my living room floor with this ISDT hobby charger. That of course was for the sole purpose of immediately throwing a load on it and seeing how much I could pull out to gauge usable capacity on these old cells. I'll probably configure my overvoltage relay to 13.3 which should represent 90+% charge, and I doubt they'll ever go below 30% SOC since I really just need the fridge to keep running til the sun comes out, or til I run the engine (going to buy a DC-DC charger soon).
I feel like most BMS+balance boards I've seen state they don't even start balancing until 3.6v. So I do wonder how people are using them if they care about pack longevity and want to just play around in the 20%-80%SOC area. I think that also played in to me wanting to get an active balancer... not wanting any cell to ever have to hit close to 3.6v to trigger balancing.
Recommended continuous discharge current for each of my 90ah cells is <90a. Max continuous discharge is <300a. I'm not entirely clear as to what that amounts to when you have four of those in series, but the most I'll get out of my solar setup is a bit over 10 amps and DC-DC charger at 20 or 40 amps depending on the model I get. I don't use 120v much at all, so my victron batteryprotect is the smallest 65amp one. In short, I have pretty low requirements and no plans to really fast charge. I got in to lifepo4 stuff because of lead acid letdowns, weight reduction, boredom, and a surplus of money paired with stubbornness (not buying a battleborn)
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hour
Observer
Looking at that Renogy chart on the last page for this product, what are your thoughts on its lithium charge options? 13.0, 12.8, 12.6 for Type 1 (whatever that means), and Type 2 (also, whatever that means) of 14.6, 14.4, 14.2, 14.0. Even the lowest of type 2 exceeds 100% capacity and is unnecessary and undesirable. On Type 1, none of those seem particularly useful if the highest - 13v is roughly ~30% state of charge.
I have never seen a charge source labeled "lithium ready" whose canned setpoints are what I would want to use on my LFP banks,
Any charge source can be made more suitable than those for LFP - the only thing required is user-adjustable custom setpoints, and if used with small banks, the ability to derate current output.
Ability to set Float and AHT to none, just stop when voltage is reached is a "would be nice", but vanishingly rare, can't think of examples
Any charge source can be made more suitable than those for LFP - the only thing required is user-adjustable custom setpoints, and if used with small banks, the ability to derate current output.
Ability to set Float and AHT to none, just stop when voltage is reached is a "would be nice", but vanishingly rare, can't think of examples
Yes, IMO that means only (maybe) useful for the LVD / HVD cutoffs function, not for balancing.
If the cells are healthy and matched enough, usage is at low C-rates (well under say .8C) also avoids the voltage shoulders (as it should anyway)
and another means for checking / correcting any imbalances is regularly employed as a maintenance protocol,
then IMO doing without any cell-level hardware gives simplicity and overall lower risk of failure.
Pack-level HVD, LVD, short / current protections are then sufficient
and in some cases temperature cutoffs
Same as with a single cell, 1C and 3.3C respectively.
Best longevity to size vs loads so 30A is max normally, occasionally hitting double that for a few minutes at a time no real harm.
If you find using 70-80A becomes frequent, add another string.
Also better to charge at lower rates when on shore power, say 30-40A better than 60
hour
Observer
Thanks, you've helped a ton in the...2 weeks I've been in possession of lithium batteries and trying to get things ready for the season.
Still unsure of how one can benefit from this renogy unit though running lithium.. making it more suitable as you say. My high voltage disconnect relay that I ordered just disconnects if the incoming voltage exceeds my preset. I got it because I didn't want to put all my faith in the custom profile I'd set for my Victron 75/15... an added layer of redundancy instead of trusting that '13.5' (or something) in a text box on victron app would be honored. Setting this renogy on 14v would put each cell at 3.5v, and running it through the same relay gizmo would just cause it to shut off unless I set that to 14, or 14.1 or something.
Setting it to 14v and using a configurable buck converter seems like a less than glamorous solution and those aren't as common in high amp ratings, and since 1 in every 2 buck converters has a 2 star rating on Amazon... slim pickings.
Still unsure of how one can benefit from this renogy unit though running lithium.. making it more suitable as you say. My high voltage disconnect relay that I ordered just disconnects if the incoming voltage exceeds my preset. I got it because I didn't want to put all my faith in the custom profile I'd set for my Victron 75/15... an added layer of redundancy instead of trusting that '13.5' (or something) in a text box on victron app would be honored. Setting this renogy on 14v would put each cell at 3.5v, and running it through the same relay gizmo would just cause it to shut off unless I set that to 14, or 14.1 or something.
Setting it to 14v and using a configurable buck converter seems like a less than glamorous solution and those aren't as common in high amp ratings, and since 1 in every 2 buck converters has a 2 star rating on Amazon... slim pickings.
There's nothing wrong with charging To a bit higher voltage, as long as you're not holding CV there, for long or at all.
14V should be fine.
Remember, when the bank is depleted, say to 13V resting, applying a low-C charge current will not raise the "combined circuit" voltage much.
As that voltage rises, so does SoC.
If the charge is stopped as soon as it hits 14V (no CV / Absorb stage), the bank is "functionally full"; there is no practical reason to want to push any more.
There isn't any "damage" (lost cycle lifetime) in that scenario, very close to, maybe even a bit below SoC resulting from:
13.8 and hold Absorb until endAmps = .02C
depending on the charge amps rate.
14V should be fine.
Remember, when the bank is depleted, say to 13V resting, applying a low-C charge current will not raise the "combined circuit" voltage much.
As that voltage rises, so does SoC.
If the charge is stopped as soon as it hits 14V (no CV / Absorb stage), the bank is "functionally full"; there is no practical reason to want to push any more.
There isn't any "damage" (lost cycle lifetime) in that scenario, very close to, maybe even a bit below SoC resulting from:
13.8 and hold Absorb until endAmps = .02C
depending on the charge amps rate.
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