Li Batteries and inrush current to inverters?

L

LoneSprinter

Active member
Lithium Battery Management System shutting down due to high inrush currents...anyone else experiencing this issue?

I'm converting a 2016 Sprinter into an RV. I purchased 2 Battleborn Li 100AHr batteries connected in series. I also purchased an AIMs 24V, 2KW, Low frequency inverter/charger. What I'm experiencing is a shut down of the Li battery's Battery Management System (BMS) with the initial start-up (closing of a battery isolation switch in the battery bank's negative lead) connected to the inverter, or any time the inverter is disconnected for any length of time (several hours or overnight) the inverters internal capacitors discharge. Cycling the battery isolation switch brings the BMS/batteries back online, but nothing works until the switch is cycled. AIMs confessed the inrush current to charge the capacitors in the inverter draws +500A and the standby current draw for the inverter not even being turned on is significant enough to warrant turning it off when no AC power is being used. Battleborn tells me the BMS shuts down at 700A. I'm being told by all involved what I'm experiencing is rare. It should only be occurring on inverters rated for 4KW or above where a Current Surge Limiter (CSL) is used to limit the inrush current a major additional expense expense, if it even works on for this small of an inverter...Battleborn was nice enough to send me one to try before I buy because they're not certain it's going to work. I doubt this issue is rare. As I'm building this van inside a garage connected to my home I open the battery isolation switch whenever I'm not working on the van to limit the possibility of any fire risk.

I'm wondering if anyone else using Li batteries is having issues with the BMS and their inverters...either low frequency or high frequency inverters?

AIMs has suggested an incandescent light bulb and switch to bypass the battery isolation switch in order to pre-charge the inverters capacitors. I haven't tried this yet but will shortly. Anyone else have any other "brilliant" solutions to this issue? I actually think the bulb might work for me.

Anyone considering Li batteries to swap out for any other battery technology needs to know absolutely everything about their coaches electrical system and any connected components before attempting this. While researching Li batteries a number of suppliers stated things like direct replacement, but don't believe it. Don't get me wrong, I think Li batteries are the future, it's just right now you have to be very careful because a lot of suppliers just don't have the experience with the Li battery technology and nobody wants to loose a sale...caveat emptor!
 
D

Deleted member 86082

Guest
My batteries are in parallel and 12v. Double the available current but half the voltage as yours. No inrush issues at all. Inverter is 2500w.
 
C

calbiker

Well-known member
Interesting problem. The BMS max surge current is 700A. That means resistance should be greater than 24V/700A = 34 mOhm.

Not sure the output resistance of your batteries. I would inquire if you have a contact. Let's say they are 15 mOhm. Two in series gives you 30 mOhm. You would need something like 5 mOhm (perhaps in cable resistance) to bridge the gap. You could change to a cable with higher resistance.
 
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J

john61ct

Active member
I would avoid "drop-in" type in converting to LFP.

Also better quality inverters, if actually needed, I try to avoid them as much as possible.

Xantrex is good but terrible CS attitude. Magnum is the best, Vanner, Victron, MasterVolt, Sterling, Outback, ProMariner but pricey. Samlex and Tripplite solid middle ground. I've heard Morningstar is good.

AIMS is not much of a step up from cheap-chinese off Ali
 
marklg

marklg

Well-known member
The Battleborn 100 Ah specifies 100A for 30 seconds and 200A for 0.5 seconds.
The Lifeblue 100 Ah specifies 100A continuous, 300 A for 3 seconds and BMS cutoff of 420 A for 6 seconds.
The Trillium 92 AH specifies 92A continuous, 250A for 30 seconds and max instantaneous discharge of 400A.

It seems some of the others may be more suited to this particular application and maybe Battleborn has not kept up with the competition. Both of the others include internal monitoring, so you don't need an external monitor, although the Trillium needs an external CAN interface that they do not seem to provide yet.


Regards,

Mark
 
J

john61ct

Active member
If you do not feel confident to just buy top quality cells and put in your own protective circuitry

then just pony up for a built system from Lithionics/Ocean Planet, Victron, MasterVolt or Redarc (Oz specific?).

But really, the former approach really isn't rocket science. . .

Those "drop-ins" are just too limited, basic quality issues, I suspect won't get over a fraction the cycle lifetime, and you just do not even have basic access to the cells for testing and maintenance.

But for someone looking to recharge screen gadgets, run a few lights and a fan, not interested in the tech details and money to burn, I guess they'll do, just not for me. . .
 
L

LoneSprinter

Active member
Thanks to all that took the time to respond. I tried the suggested light bulb by-pass and it worked fine. In the final setup I'm going to either replace the inverter or run a fused resister line to slower the pre-charge of the inverter...possibly both.
 
L

LoneSprinter

Active member
john61ct,

Hi...I'm not sure how to do what you're asking. Could you provide a link to an example of what you're referring to please? Preferably how to build your own Li battery and how/where you get the BMS components?
 
M

Midwestdrifter

Engineer In Residence
Building a DIY lithium pack should only be attempted by the skilled DIY with the time to do the research. You need to be proficient in basic DC wiring, crimping cables, etc. For most folks the time involved making a DIY pack exceeds the cost savings.
 
J

john61ct

Active member
It is true, there is no one simple way to build a bank, as you do research and learn the variables involved you will pick up your own ideas.

In this case

LoneSprinter said:
the suggested light bulb by-pass and it worked fine. In the final setup I'm going to either replace the inverter or run a fused resister line to slower the pre-charge of the inverter...possibly both.
Click to expand...
I figured things are simpler.
 
RVBarry

RVBarry

2023 AWD 170 DIY CamperVan
Hi, is this still an issue with current BMS's?
@vanski, how about with your battery pack/BMS?

My planned inverter would be a Victron 12/3000/120 or Magnum MSH3012RV / MSH3012M.
I read the inrush can exceed 3000A.

Is a 300A battery disconnect switch going to be damaged (by arcing) when switching?
e.g. a Blue Sea 6007 (300A continuous, 900A 30sec cranking rated)

Thanks!
 
B

borabora

Well-known member
RVBarry said:
Hi, is this still an issue with current BMS's?
@vanski, how about with your battery pack/BMS?

My planned inverter would be a Victron 12/3000/120 or Magnum MSH3012RV / MSH3012M.
I read the inrush can exceed 3000A.

Is a 300A battery disconnect switch going to be damaged (by arcing) when switching?
e.g. a Blue Sea 6007 (300A continuous, 900A 30sec cranking rated)

Thanks!
Click to expand...
Are you worried about this because you plan on disconnecting the inverter frequently for many hours or days? Short disconnects shouldn't be an issue because the capacitors won't fully discharge. If you let them discharge then I would use a resistor bypass before closing the switch.
 
H

hoosierrun

Active member
I have a Magnum MS2000, 2000 VA inverter and it recommends 400 or more AH battery capacity. I ended up putting in 400 AH of Battleborn, and I did have trouble getting the inverter started with just 2 batteries. My 2nd set of batteries can be switched in and out with a paralleling switch. In-rush due to caps can be significant.
 
vanski

vanski

If it’s winter, I’m probably skiing..
@RVBarry i haven’t experienced this failure in systems I’ve put together. But yes, they had a minimum 280ah of capacity and they all have had better inverters. I do have an install coming up where most likely I can only fit 200ah of LFP so this failure is interesting.
 
vanski

vanski

If it’s winter, I’m probably skiing..
I’ve seen Will P use those to prevent the initial spark when landing wires on an inverter, but they look small and he simply puts them in-line. What would be the needed resistor for a permanent and stable install? Or I guess the better question is how would the resistor be installed for a permanent and stable configuration?
 
B

borabora

Well-known member
vanski said:
I’ve seen Will P use those to prevent the initial spark when landing wires on an inverter, but they look small and he simply puts them in-line. What would be the needed resistor for a permanent and stable install? Or I guess the better question is how would the resistor be installed for a permanent and stable configuration?
Click to expand...
You can't have a resistor in parallel or inline permanently because it either would not allow you to disconnect the inverter or it would drop voltage in an unacceptable manner.
Instead of a simple On/Off switch you could install a 3 position switch that goes from On --> Charge --> Off and in reverse from Off --> Charge --> On. Instead of a resistor something like a 30W 12V halogen bulb could be used because unlike the resistor it will give the user a clue when the capacitors are charging or fully charged. It will blink on then go off when the inverter is first connected.
I would suspect that the better inverter manufacturers will soon incorporate inrush current limiting circuits as LIFEPO4 replaces SLA batteries.
 
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