why do some LiFePo4 battery have two connectors
ba...@k7bwh.com
Hive mind question: Why do some LiFePo4 batteries have separate charge and load connectors? Can I safely charge the battery through the load connector using a suitably intelligent charger?
I’m shopping for a battery for the rover van and there are good prices on “ebike” batteries. Most of these have two connectors, one for the high-current load and another for the charger. Here’s an example picture of a random craptastic lithium ebike battery; this is one that I might buy. I’m just trying to understand how they’re built.
In my van I’ll connect the main battery negative output lead through a Victron SmartShunt for monitoring the state of charge (SOC). This is also how I must charge it, so that the shunt can keep proper track. The “charging” connector will go unused. So I’m trying to understand if charging will work this way, or if the battery has some special electronics (like a BMS) in its charging port. Shucks, I don’t even know if these things have a BMS or not.
Thanks, Barry K7BWH
Mihai Manolache
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KC7PBH
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ba...@k7bwh.com
Thanks Brad. Do you know if there’s typically a BMS circuit inside batteries like this? That is, it would be nice if these things have battery-balancing built in. I wouldn’t expect low-temperature cutoff in cheapo eBay batteries.
It’s a relief to hear that charging can be done with either connector. I have access to a 12v battery like this and will try it out. The shunt is set up already and it’s easy to run this little experiment.
73 Barry K7BWH
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Paul Butzi
On Jun 3, 2022, at 9:26 AM, <ba...@k7bwh.com> <ba...@k7bwh.com> wrote:
Hive mind question: Why do some LiFePo4 batteries have separate charge and load connectors? Can I safely charge the battery through the load connector using a suitably intelligent charger?I’m shopping for a battery for the rover van and there are good prices on “ebike” batteries. Most of these have two connectors, one for the high-current load and another for the charger. Here’s an example picture of a random craptastic lithium ebike battery; this is one that I might buy. I’m just trying to understand how they’re built.
<image002.jpg>
In my van I’ll connect the main battery negative output lead through a Victron SmartShunt for monitoring the state of charge (SOC). This is also how I must charge it, so that the shunt can keep proper track. The “charging” connector will go unused. So I’m trying to understand if charging will work this way, or if the battery has some special electronics (like a BMS) in its charging port. Shucks, I don’t even know if these things have a BMS or not.Thanks, Barry K7BWH
KC7PBH
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Rod Johnson
From: ba...@k7bwh.com
To: issaqu...@googlegroups.com
Sent: Fri, Jun 3, 2022 9:26 am
Subject: [IARC] why do some LiFePo4 battery have two connectors
 |
Gerard Hickey
Sorry coming into this conversation a little late.
Generally most standalone LifePO4 batteries will have a BMS built
into the case to manage the individual cells. Many of the battery
packs for ebikes and other applications are just the cells and the
BMS is built into the device itself. In cases where it is a
separate BMS there is usually a second connector that has a wire
that goes to the connection between each bank of cells so that the
BMS can balance the cells and equalize the voltage across the
cells. I have usually seen this as a JST connector.
Most of the low end applications like ebikes, scooters, one-wheel
skateboards, etc. do not have a BMS and just use the raw cells. If
the battery pack was manufactured with cells that were all from
the same lot this is usually not a problem as they generally
discharge and charge at pretty much the same rate and the minor
differences in voltage don't really matter that much. Over the
long term, yes, it does matter as the cumulative difference across
the cells will eventually make the battery pack appear that it has
reached its lifetime and be replaced. The reality is that in many
cases the battery pack can be charged/discharged once or twice
with balancing the cells to get it pretty healthy again. Not back
to 100%, but usually 85-90% easily.
The image you provided in your email to me appears to be a
standard battery pack without a BMS and without the balancing
harness. It appears to be the standard blue shrink wrap that is
used to hold the cells together. Given it is 48v, I would say that
it is probably a 15S battery (that is 15 banks of cells in series
to get to 48v) and then depending upon which cells were used any
where from 3P to 5P to get the 20 AH (that would be 3-5 packs of
15 cells in parallel to get the current ratings).
Actually just found a reference to the one that you had the
picture to. It is a 13S3P battery, but what is not clear to me is
if it is LiPO or LifePO4. To me it seems to indicate that it is a
LiPO battery which is some thing I would not consider because of
the fire hazzard. It makes sense also because 13S would be using a
cell voltage of 3.7v which is a LiPO cell.
LifePO4 cells have a voltage of 3.2v which is why I was originally thinking it might be a 15S battery. With a LifePO4 battery you don't have quite the power density that you do with LiPO, but you don't run the risk of the battery bursting into flames either. Given that you would have this battery in your vehicle (even just for a little bit) I would not run the risk.
-- Gerard Hickey / WTØF IRLP:3067/Echolink:529661 hic...@kinetic-compute.com DMR: 3102272 425-395-4554
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ba...@k7bwh.com
Thanks Rod. Your description sounds sensible for mfrs that offer the lowest possible cost: the charging point is not directly connected to the high current port. My plan is to use a smart charger designed for lithium-style batteries with bulk and absorption phases built in, and connect it to the big bus bar.
I’ll run an experiment this weekend. Rod, remember when we got those blue ebike 12v 20ah batteries years ago? Still have mine. It has two connectors like this. It’ll make a good test case for charging via its high-current port. That old battery came with a 10A charger that’s godawful noisy on 6 meters – it was a big problem on Green Mtn last month. I can hardly wait to replace that charger with something, anything else. Then at home between trips charge it again on the proper port so the BMS can do its cell-balancing act.
Oh, I finally noticed a missing word in my original note. I meant to say a “random craptastic lithium ebike battery; this is NOT one that I might buy.” Jeez. Proofreaders these days, smh.
Anyway, I’ll be specifically using LiFePo4 chemistry and not LiPO.
Thanks to Gerard for more insight. It seems to me the old ebike battery I currently have (not the one in my picture) doesn’t have room inside the blue shrinkwrap for a BMS, nor does it show bumps that would suggest a BMS.
73 Barry K7BWH
PS - I’ve watched many Will Prowse videos about batteries on YouTube. Highly recommended. Each video is short and to the point. It’s been interesting to watch him reviewing successively larger batteries, most recently a 200-lb monster of a server rack 48v battery. I was originally quite enamored with those 48v 100ah batteries that come complete and are so easy to wire into a system. I’ve done the energy budge and It’s big enough to run my whole high-power rover for a weekend, including making meals. But they weigh 107 lbs. Once I admitted to myself I’d never want to manhandle that in/out of a van, I’m looking more at a 30-40 lb weight limit, which puts me in the 40 to 50 amp-hour range of 48v batteries. Why 48v? Because I might be able to direct-drive a 6m solid state amplifier. Anyway, the ebike batteries are looking more sketchy the further I get. My design journey continues.
Sorry coming into this conversation a little late.
Generally most standalone LifePO4 batteries will have a BMS built into the case to manage the individual cells. Many of the battery packs for ebikes and other applications are just the cells and the BMS is built into the device itself. In cases where it is a separate BMS there is usually a second connector that has a wire that goes to the connection between each bank of cells so that the BMS can balance the cells and equalize the voltage across the cells. I have usually seen this as a JST connector.
Most of the low end applications like ebikes, scooters, one-wheel skateboards, etc. do not have a BMS and just use the raw cells. If the battery pack was manufactured with cells that were all from the same lot this is usually not a problem as they generally discharge and charge at pretty much the same rate and the minor differences in voltage don't really matter that much. Over the long term, yes, it does matter as the cumulative difference across the cells will eventually make the battery pack appear that it has reached its lifetime and be replaced. The reality is that in many cases the battery pack can be charged/discharged once or twice with balancing the cells to get it pretty healthy again. Not back to 100%, but usually 85-90% easily.
The image you provided in your email to me appears to be a standard battery pack without a BMS and without the balancing harness. It appears to be the standard blue shrink wrap that is used to hold the cells together. Given it is 48v, I would say that it is probably a 15S battery (that is 15 banks of cells in series to get to 48v) and then depending upon which cells were used any where from 3P to 5P to get the 20 AH (that would be 3-5 packs of 15 cells in parallel to get the current ratings).
Actually just found a reference to the one that you had the picture to. It is a 13S3P battery, but what is not clear to me is if it is LiPO or LifePO4. To me it seems to indicate that it is a LiPO battery which is some thing I would not consider because of the fire hazzard. It makes sense also because 13S would be using a cell voltage of 3.7v which is a LiPO cell.
LifePO4 cells have a voltage of 3.2v which is why I was originally thinking it might be a 15S battery. With a LifePO4 battery you don't have quite the power density that you do with LiPO, but you don't run the risk of the battery bursting into flames either. Given that you would have this battery in your vehicle (even just for a little bit) I would not run the risk.
--
Gerard Hickey / WTØF
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Derek Chauran
Sent: Friday, June 3, 2022 4:58:40 PM
To: issaqu...@googlegroups.com <issaqu...@googlegroups.com>
Subject: RE: [IARC] why do some LiFePo4 battery have two connectors
Rod Johnson
Rod Johnson
Rod Johnson
Rod Johnson
Paul Butzi
LFP: Why is there a separate DC barrel plug connector and PowerPole Connector on my battery? Can I charge through either connector?
On our PVC Pack LiFePO4 batteries, there are two separate connectors. The first connector has a DC barrel plug and the second connector has an Anderson Powerpole connector. The two connectors are indeed wired in parallel on the PCM (protection circuit module) that is integrated in every single battery pack. So it is perfectly okay and fine to charge through the PowerPole connectors. Many customers requested two separate connectors in the batteries, in order to keep the battery's charger attached to the battery, such that the battery and charger can be stored in a portable Go-Box. At the same time, customers can leave the PowerPole connector attached to the radio communications equipment, without having to repeatedly disconnect the charger from the battery, and attach the radio communications equipment. However, we understand customers want to charge through the Powerpole connectors and use various other third party products. We provided the two sets of connectors, simply for convenience purposes.
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<image001.jpg>
Mihai Manolache
Rod Johnson
At least on every charge I’ve seen, the green light does not mean it’s no longer charging the battery, it just means the charger is now in constant voltage mode instead of constant current mode.Some time later, the charge current will drop close to zero. The battery is fully charged.
Paul Butzi
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Rod Johnson
Derek C.
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John KA7TTY
I have been running an experiment using a Drok 2001802006 Battery Monitor/Charge Controller with a Bioenno Power BLF-1203AB 3 Ah 12 volt Battery. This is connected 24/7 to an old ICOM IC-02AT 2m HT since May 2020. This battery has the Anderson Power Pole discharge pigtail and the concentric connector identified as the charging connector. When I checked the resistance between the 2 positive contacts, and between the 2 negative contacts, I measured zero ohms. Dead short. The experiment connects only to the Anderson Power Pole connector. This setup cycles to charge at 11.2 v and charges to 14.55 v. The battery rating is 14.6 v. When it switches to discharge the voltage measures 14.16 v. It completes a discharge/charge cycle about every 4-5 hours. It uses the charger provided by Bioenno along with the battery.
I decided to use the 3 Ah battery (about $50) and then replace it with a 20 Ah battery (about $225) if all went well. I just haven’t gotten around to buying the bigger battery.
Curiously, the larger Bioenno batteries only have terminals (no pigtails) so all the charging and discharging is done through the same connections.
My overall conclusion is that at least for the Bioenno batteries, you can connect to either one.
John KA7TTY