Alan B
100 GW
Does anyone with a 2 slot device (mower or snow blower) that uses them in parallel - do they have any circuitry when they parallel them? Or are they directly paralleled?? (( do any mowers take parallel batteries?? ))
Understanding and Using EGO Power+ Batteries
- Thread starter Alan B
- Start date
Yeah, like what happens if I put 2 5Ah packs in and one is fully charged but the other is almost empty? I don't see anything in the manual about that.
This topic discusses it but without a good answer:
Snowblower use with 7.5Ah and 2.5Ah battery
https://community.egopowerplus.com/ego/topics/snowblower-use-with-7-5ah-and-2-5ah-battery
This topic discusses it but without a good answer:
Snowblower use with 7.5Ah and 2.5Ah battery
https://community.egopowerplus.com/ego/topics/snowblower-use-with-7-5ah-and-2-5ah-battery
Alan B
100 GW
Exactly.
I reviewed the snow blower manual, I didn't see anything clear about mixing charge states. I didn't find a mower that had 2 slots (but maybe there is one), but the snow blower does have two slots that they say work together. Of course they always recommend charging before use, so perhaps that's how they cover it. Diodes could be used, but at these currents they aren't easy and there is some loss. So for now I'll assume that charging them before use and using them as a pair should be fine.
Another thought is that they might use a 2 pole switch to supply power to the blower, because under load they won't be very likely to cross-charge. Cross charging requires a voltage differential to drive it, and two batteries at different charge states will have a voltage differential, but in real life the cross charging currents may not be large enough to be a problem for these high current cells. Still, it is not something that we want. I can think of a smart switch to combine the power to the motor controller using FETs, but that's another project that we probably don't need very much.
I reviewed the snow blower manual, I didn't see anything clear about mixing charge states. I didn't find a mower that had 2 slots (but maybe there is one), but the snow blower does have two slots that they say work together. Of course they always recommend charging before use, so perhaps that's how they cover it. Diodes could be used, but at these currents they aren't easy and there is some loss. So for now I'll assume that charging them before use and using them as a pair should be fine.
Another thought is that they might use a 2 pole switch to supply power to the blower, because under load they won't be very likely to cross-charge. Cross charging requires a voltage differential to drive it, and two batteries at different charge states will have a voltage differential, but in real life the cross charging currents may not be large enough to be a problem for these high current cells. Still, it is not something that we want. I can think of a smart switch to combine the power to the motor controller using FETs, but that's another project that we probably don't need very much.
zro-1
1 kW
This is guessing, but if these can monitor pack heat, then in a case where you did parallel one full pack with an almost empty pack, wouldn't the heat from the rapid discharge --> charge cause things to cut off?
Alan B
100 GW
1. As far as we know, the BMS does not control a switching element in the main current leads. It is up to the tool to shut down. If there's no switching element then he cross charging current can not be controlled (by the BMS), aside from the (natural) voltage differential (charge states) and the resistances. The cells gaining voltage will rise quickly and the supplying cells voltage will fall and the differential voltage driving the current will fall so the current will fall. The BMS will not like the temperature but what can it do?
2. The voltage differential available to drive current from the charged battery to the discharged battery, together with the cell and path resistance will moderate the cross charging current. It may not be enough voltage to get to a really high current. The available voltage is less than a fast charger.. The resistance of the two sets of cells is in series, so double the resistance that would be in a fast charging system since the charger has virtually zero resistance (due to feedback loops). So this may not get to as high a current as the fast charger does. It is a little hard to predict, and I haven't tried to model it in detail, but if it did heat up it could be bad. Worst case would be if one pack had a shorted cell.
Paralleling two packs at the same state of charge (fresh off the charger or drained in parallel after that) should avoid these issues.
2. The voltage differential available to drive current from the charged battery to the discharged battery, together with the cell and path resistance will moderate the cross charging current. It may not be enough voltage to get to a really high current. The available voltage is less than a fast charger.. The resistance of the two sets of cells is in series, so double the resistance that would be in a fast charging system since the charger has virtually zero resistance (due to feedback loops). So this may not get to as high a current as the fast charger does. It is a little hard to predict, and I haven't tried to model it in detail, but if it did heat up it could be bad. Worst case would be if one pack had a shorted cell.
Paralleling two packs at the same state of charge (fresh off the charger or drained in parallel after that) should avoid these issues.
Teardown of the snowblower (I assume there's only one model) and battery: https://www.youtube.com/watch?v=8FaTU5Dsono
Confirms Samsung 25R cells
Motor and general wiring look a bit small for a claimed 2000W. Perhaps that's stall power or something daft. Run time measured at 8mins on full power with the 1P pack at the claimed 140Wh would be around 1000W.
Confirms Samsung 25R cells
Motor and general wiring look a bit small for a claimed 2000W. Perhaps that's stall power or something daft. Run time measured at 8mins on full power with the 1P pack at the claimed 140Wh would be around 1000W.
Alan B
100 GW
The link above is a review of the leaf blower, not the snow blower. The language is pretty raw. It only uses a single battery, so it doesn't address the parallel battery issue. I don't believe it is over 1000W, but it drains a battery pretty fast if you use the turbo feature much.
There is some surprising technology in the leaf blower (this is one of at least three different models I've seen).
This seems to be the model I have, and it works very well. With turbo mode on it really has some recoil.
The reviewer glues down the turbo button which is going to reduce runtime a lot. This unit has a variable speed pot and a turbo button. The trigger on this unit is a microswitch operated by the index finger and just does on-off. The speed is controlled by the lever on the front, which can be adjusted with the hand not holding the blower. The Turbo button is thumb operated by the blower holding hand and kicks the unit into a really high speed mode which consumes a lot of power. I don't find it necessary to use turbo all the time and would not make the modification he made.
The reviewer also fails to understand a lot of the issues with regard to cooling lithium batteries and controlling their temperatures. He favors smaller battery packs which don't have the cooling needed for more powerful tools.
I did a few searches on utube and didn't find a disassembly video on the actual snowblower that EGO makes.
There is some surprising technology in the leaf blower (this is one of at least three different models I've seen).
This seems to be the model I have, and it works very well. With turbo mode on it really has some recoil.
The reviewer glues down the turbo button which is going to reduce runtime a lot. This unit has a variable speed pot and a turbo button. The trigger on this unit is a microswitch operated by the index finger and just does on-off. The speed is controlled by the lever on the front, which can be adjusted with the hand not holding the blower. The Turbo button is thumb operated by the blower holding hand and kicks the unit into a really high speed mode which consumes a lot of power. I don't find it necessary to use turbo all the time and would not make the modification he made.
The reviewer also fails to understand a lot of the issues with regard to cooling lithium batteries and controlling their temperatures. He favors smaller battery packs which don't have the cooling needed for more powerful tools.
I did a few searches on utube and didn't find a disassembly video on the actual snowblower that EGO makes.
999zip999
100 TW
Can you just ask egp for an answer ? As I could see a possible problem here.
Alan B
100 GW
I don't expect them to comment (in a favorable way) regarding DIY applications.
Alan B
100 GW
I started another 3D test print of the battery connector. I've made a few changes from the first test, so this should fit better. On the first test I had to file a fraction of a mm off the rails to get it to fit the battery.
We do need to find connector material for these connections to the battery. It is 0.80 mm thick (approximately 20 gauge), about 20 x 36mm in size, and appears to have a nickel plating. I suspect the material is copper. Two of these will be required.
We do need to find connector material for these connections to the battery. It is 0.80 mm thick (approximately 20 gauge), about 20 x 36mm in size, and appears to have a nickel plating. I suspect the material is copper. Two of these will be required.
Raisedeyebrows
1 kW
The material needed for the spades is similar to this stuff, maybe different dimensions and I’d assume getting it in bulk form is of course preferable?:
https://www.greenbikekit.com/electric-bike-4-pin-connector.html
https://www.greenbikekit.com/electric-bike-4-pin-connector.html
Alan B
100 GW
It is quite a bit different than the contact material in the posting linked above. Much thinner, and larger. It is supported on two sides by the connector and the hood.
In this CAD drawing the connector blades are pink and shown transparent. Since they are being used subtractively here to cut clearance, they are also slightly thicker than the correct value to account for clearance and 3D printing tolerance. The contact is bolted to one surface and slotted into the other to give it stiffness and locate it properly.
In this CAD drawing the connector blades are pink and shown transparent. Since they are being used subtractively here to cut clearance, they are also slightly thicker than the correct value to account for clearance and 3D printing tolerance. The contact is bolted to one surface and slotted into the other to give it stiffness and locate it properly.
Attachments
Alan B
100 GW
Alan B
100 GW
I found some 20 gauge Nickel Silver material on Amazon that seems to be about right. It is 0.81mm thick, and is 65% copper, 18% nickel and 17% zinc (contains no silver). The 150x150mm piece costs $14 so not too bad for a small quantity, sufficient to make quite a few battery connectors (about 28 contacts). The design of the battery connector could be adjusted to use a little less material.
The second prototype battery connector / mount just finished printing. It fits the battery rails very nicely. The first one was very snug. This one slides freely.
The second prototype battery connector / mount just finished printing. It fits the battery rails very nicely. The first one was very snug. This one slides freely.
Attachments
Raisedeyebrows
1 kW
Crimp Supply has contacts, possible they might be able to order the right size material or actual ones that are coated on all sides?
https://crimpsupply.com/battery-terminals-copper-lugs?cat=223
https://crimpsupply.com/battery-terminals-copper-lugs?cat=223
Alan B
100 GW
The contacts we need are more like sheet metal than regular contacts. 20 x 36 mm and 0.8mm thick. See what you can find!
Alan B said:
Ah, OK, didn't realise that was the leaf blower.
The parallel battery question is a good one. I guess it's going to take someone with a 2-pack tool to take it apart and inspect the wiring between the battery holders and maybe perform an electrical test with a fully-charged & nearly-discharged battery.
Alan B
100 GW
One could always blow some snow with the leaf blower, as he mentions, but EGO has a regular snow blower that takes two batteries at once and apparently operates them in some form of parallel.
Charging both batteries before paralleling them should work fine. Lots of folks use parallel packs, I often use a parallel pack for range boost, but I charge both packs and then parallel them, so they have the same voltage and charge state. Then they are not going to shuffle current back and forth between them to any significant amount.
If you had two packs that were not the same voltage, you could always use the higher one by itself for awhile until the two packs were equal, and then parallel them.
We could make a circuit with diodes or FETs to essentially do the same thing automatically.
Charging both batteries before paralleling them should work fine. Lots of folks use parallel packs, I often use a parallel pack for range boost, but I charge both packs and then parallel them, so they have the same voltage and charge state. Then they are not going to shuffle current back and forth between them to any significant amount.
If you had two packs that were not the same voltage, you could always use the higher one by itself for awhile until the two packs were equal, and then parallel them.
We could make a circuit with diodes or FETs to essentially do the same thing automatically.
tomjasz
1 GW
Sadly, a single stage snow blower at a two stage price.
Alan B
100 GW
Let's not get into pricing (especially of the tools), we're just looking at how to re-utilize the batteries in a safe and effective way. A large part of costs are the batteries, the tools with no batteries are usually not bad.
If we don't find anything better soon, I'll get some of that nickel-silver for contacts. I see some brands use brass instead of copper, so have even higher resistivity. I'm also concerned that this jewelry type material may be too soft.
If we don't find anything better soon, I'll get some of that nickel-silver for contacts. I see some brands use brass instead of copper, so have even higher resistivity. I'm also concerned that this jewelry type material may be too soft.
tomjasz
1 GW
Actually, having bought scores of pieces of lawn maintenance stuff i’m not at all put off by any price other than th3 snowblower. Thanks for the continued work. This is really looking good.Alan B said:
Alan B
100 GW
Luckily I don't need snowblowers here so not familar with the pricing or use of them. 
The rare snow we get here generally melts on contact. Right now we're getting several inches of liquid snow. We send the snow to the mountains to feed the reservoirs later in the year, and support the skiiers and resorts who profit from this sort of thing.
I went ahead and ordered some 20 gauge copper/nickel/zinc alloy material (so called nickel-silver alloy). It is probably going to be soft. Perhaps it can be heat treated.
I'm trying to decide if I want to increase the dimensions of the battery mount/connector to make it a little bit more precise fitting. The first one was too tight in one dimension, the most recent one has about 0.7mm clearance in one direction, and 0.3mm in the other. 0.3mm is not bad, the 0.7mm could be a bit tighter.
I've got some other projects right now so can't spend too much time on this, but in a couple weeks should be clear to set this up on a bike and give it a try.
The rare snow we get here generally melts on contact. Right now we're getting several inches of liquid snow. We send the snow to the mountains to feed the reservoirs later in the year, and support the skiiers and resorts who profit from this sort of thing.
I went ahead and ordered some 20 gauge copper/nickel/zinc alloy material (so called nickel-silver alloy). It is probably going to be soft. Perhaps it can be heat treated.
I'm trying to decide if I want to increase the dimensions of the battery mount/connector to make it a little bit more precise fitting. The first one was too tight in one dimension, the most recent one has about 0.7mm clearance in one direction, and 0.3mm in the other. 0.3mm is not bad, the 0.7mm could be a bit tighter.
I've got some other projects right now so can't spend too much time on this, but in a couple weeks should be clear to set this up on a bike and give it a try.
Not paralleling packs of different SOC is very sensible, but as a consumer product with parallel packs it is foreseeable and inevitable that it will happen and I'd be very surprised if it wasn't taken into account during the design. There must be some kind of prevention or mitigation system in the tool, or it was tested and found not to be harmful/dangerous.
Alan B
100 GW
Punx0r said:
Exactly. So we need to know what they did, if anything, so we can do the same. They say to charge before use, but they did not make a big deal out of it.
http://www.ejbmetals.com/p/47/select_by_name/C75200
Conductivity is fairly low (would get warm at higher currents), but...I did find this...
Low conductivity is similar to high resistance, so...these blades are their own homogenous "pre-charge resistor"?
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